tag:theconversation.com,2011:/uk/topics/materials-science-24012/articlesMaterials science – The Conversation2024-03-22T12:31:50Ztag:theconversation.com,2011:article/2201902024-03-22T12:31:50Z2024-03-22T12:31:50ZThin, bacteria-coated fibers could lead to self-healing concrete that fills in its own cracks<figure><img src="https://images.theconversation.com/files/578396/original/file-20240227-26-c98ze5.jpg?ixlib=rb-1.1.0&rect=0%2C7%2C5176%2C3437&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Cracked roads and sidewalks generate big costs for cities. </span> <span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/CaliforniaDroughtRain/f93eda16ae2d49ad8539aaf1ad9eb92c/photo?Query=cracked%20concrete&mediaType=photo&sortBy=&dateRange=Anytime&totalCount=260&digitizationType=Digitized&currentItemNo=17&vs=true&vs=true">AP Photo/Marcio Jose Sanchez</a></span></figcaption></figure><p>Some say there are two types of concrete – cracked and on the brink of cracking. But what if when concrete cracked, it could heal itself? </p>
<p><a href="https://research.coe.drexel.edu/caee/aim/">We’re part of a team</a> of <a href="https://scholar.google.com/citations?user=Tn72mFcAAAAJ&hl=en">materials</a> <a href="https://scholar.google.com/citations?user=AtY08c4AAAAJ&hl=en">scientists</a> and microbiologists that has <a href="https://theconversation.com/calcium-munching-bacteria-could-be-a-secret-weapon-against-road-salt-eating-away-at-concrete-roads-and-bridges-113970">harnessed the power of bacteria</a> to create biological fibers that <a href="https://doi.org/10.1016/j.conbuildmat.2023.133765">initial results suggest</a> can heal cracks in concrete. We’re working on a technology that, if we work out the kinks and manage to bring it to the market one day, could extend the life span of concrete.</p>
<h2>Cracking concrete</h2>
<p>Picture a bridge exposed to snow, rain, temperature changes and trucks carrying heavy loads. The concrete on the bridge will gradually develop cracks from stress and wear. Over time, these cracks expand, allowing water and corrosive substances that weaken the concrete to penetrate further down. </p>
<p>At some point, local authorities have to pay for repairs, which are not only expensive but also <a href="https://artbabridgereport.org/reports/2022-ARTBA-Bridge-Report.pdf">disrupt traffic and drain public resources</a>.</p>
<p>Now, consider a medical patient recovering from a severe injury. As the patient’s cells recognize the damage, they release tiny healing agents – like microscopic repair crews. These agents target the wounded area, mending tissues and restoring the cells’ functionality. What if concrete had the same kind of <a href="https://doi.org/10.1038/nmat1934">self-healing ability</a> as human tissue? </p>
<h2>A self-healing concrete</h2>
<p><a href="https://research.coe.drexel.edu/caee/aim/people/">Our team</a> at the <a href="https://research.coe.drexel.edu/caee/aim/">Advanced Infrastructure Materials lab</a> at Drexel University was inspired by self-healing tissue in the human body. We developed an addition to concrete we <a href="https://doi.org/10.1016/j.conbuildmat.2023.133765">call BioFiber</a>.</p>
<p>BioFiber has <a href="https://doi.org/10.1016/j.conbuildmat.2023.133765">three essential functions</a>: It heals itself on its own, it stops cracks from growing wider, and it remains intact inside the concrete when there aren’t any cracks. </p>
<p>Each BioFiber has <a href="https://doi.org/10.1016/j.conbuildmat.2023.133765">three key components</a>: a tough core fiber made of a polymer called polyvinyl alcohol, a porous layer of hydrogel infused with <em><a href="https://www.sciencedirect.com/topics/immunology-and-microbiology/lysinibacillus-sphaericus">Lysinibacillus sphaericus</a></em> bacteria, and a damage-responsive outer shell. When cracks hit the BioFiber, its outer shell breaks and releases the bacteria into the crack, which starts the self-healing process.</p>
<p>The strong core fibers in BioFiber <a href="https://doi.org/10.1016/j.conbuildmat.2023.133765">bridge the cracks</a> and stop them from growing wider during the healing process.</p>
<p>Surrounding the core fiber, the hydrogel layer is made up of a mesh of polymer chains at the molecular level that attract water. Their spongelike structure can absorb and hold large volumes of water. During the production process, we add calcium to help the hydrogel solidify. </p>
<p>The hydrogel itself is made up of a <a href="https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/alginate">natural polymer found in seaweed called alginate</a>, which has special properties that allow it to trap bacteria. Alginate isn’t toxic and is even safe for biomedical applications such as <a href="https://doi.org/10.1155/2020/8886095">drug delivery</a> and <a href="https://doi.org/10.3390/md21030189">tissue engineering</a>.</p>
<p>The hydrogel <a href="https://www.ncbi.nlm.nih.gov/books/NBK556071">houses endospores</a>, which are dormant bacteria. Once the outer shell cracks and the endospores are awakened from their dormant state, they facilitate the self-healing. </p>
<h2>Activating BioFiber</h2>
<p>The endospores need water to activate. Luckily, the middle hydrogel layer absorbs water well. When the concrete cracks, and water from rain, humidity or street runoff seeps in, the spores wake up. </p>
<p>The spores ingest carbon that we specifically add into the concrete mix, as well as calcium in the concrete itself. With these materials, the bacteria facilitates a chemical reaction called microbially induced calcium carbonate precipitation, or MICCP. This reaction creates <a href="https://doi.org/10.1016/j.dibe.2024.100351">calcium carbonate crystals</a>, which build up and fill in the cracks in the concrete.</p>
<p>The crystal shape varies, from sphere to needle-shaped, and each shape is strong enough to heal the cracks. We can alter the type of crystals the bacteria produces by changing the pH level, calcium source and type of bacteria.</p>
<p>Concrete acts like a solid, tough substance because it’s a mix of cement, sand, gravel and water. We toss the BioFibers into the mix and spread them out as the concrete is mixed, ensuring they’re evenly distributed throughout the mixture.</p>
<p>Once the self-healing process ends and the bacteria dies, the activated BioFiber is done – it can’t heal anymore. But since the concrete has many BioFibers distributed throughout, another fiber can mend the next crack. At the moment, we do not know how many cracks BioFiber concrete can heal, and we’re conducing more research to figure that out. </p>
<p>To feed the bacteria, we add the amount of food it needs to stay alive and heal the cracks, depending on how many cracks we anticipate them having to fix. When the bacteria runs out of food, the process stops. The bacteria can live for roughly a couple of weeks during the healing process. </p>
<p>While BioFiber shows initial promise, it does have shortcomings, which could make manufacturing it at a larger scale challenging. The manufacturing process and materials used are specialized and not always affordable and practical. While our first tests suggest that BioFiber extends the life span of concrete, we’ll need more testing, including field trials, to verify those early results.</p>
<p>We hope to eventually commercialize and manufacture the fibers at larger production scales, while in the meantime we continue to run tests and study how to improve BioFiber’s self-healing abilities. We’d like to one day get these fibers into roads and sidewalks to potentially prevent cracking in aging concrete.</p><img src="https://counter.theconversation.com/content/220190/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Mohammad Houshmand works for Drexel University. He receives funding from the National Science Foundation.</span></em></p><p class="fine-print"><em><span>Yaghoob Farnam receives funding from the National Science Foundation. In addition to his role as an associate professor at Drexel University, he is co-founder and senior technical advisor for SusMaX Inc. </span></em></p>Your skin heals from cuts and scrapes on its own − what if concrete could do that too?Mohammad Houshmand, Ph.D. Candidate in Civil Engineering, Drexel UniversityYaghoob Farnam, Assistant Professor of Civil Engineering, Drexel UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2141262024-02-20T13:29:38Z2024-02-20T13:29:38Z3D printing promises more efficient ways to make custom explosives and rocket propellants<figure><img src="https://images.theconversation.com/files/575456/original/file-20240213-26-q2ug1p.jpg?ixlib=rb-1.1.0&rect=6%2C3%2C2111%2C1406&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">3D printing can be used to build with all kinds of materials – even those that go 'boom.'</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/printer-printing-prototypes-royalty-free-image/1459229120?phrase=3D+printer&adppopup=true">kynny/iStock via Getty Images</a></span></figcaption></figure><p>Imagine you’re driving to work on a rainy day, when a distracted, reckless driver hits your car out of nowhere. With a “boom,” an air bag deploys faster than you can <a href="https://www.nhtsa.gov/vehicle-safety/air-bags">blink your eyes</a> to save your life. </p>
<p>That air bag deployed rapidly thanks to an energetic material called <a href="https://cen.acs.org/safety/chemicals-make-airbags-inflate-changed/100/i41">sodium azide</a>, which generates nitrogen gas during a chemical reaction to inflate your airbag. But what’s an energetic material? </p>
<p>Energetic materials include <a href="https://www.osti.gov/biblio/1765628">propellants, pyrotechnics, fuels and explosives</a>, and they’re used in all sorts of settings. </p>
<p>Uses of energetic materials include <a href="https://www.explainthatstuff.com/flares.html">flares</a>, <a href="https://www.compoundchem.com/2014/11/20/matches/">matches</a>, <a href="https://www.youtube.com/watch?v=a1Ef1PcPKjk">solid rocket boosters</a>, <a href="https://www.ict.fraunhofer.de/en/comp/em/treib.html">gun propellants</a>, hot <a href="https://www.twi-global.com/technical-knowledge/faqs/what-is-cad-welding">thermite welding</a> used to fuse materials together, <a href="https://theconversation.com/how-do-fireworks-work-a-pyrotechnics-chemist-explains-the-science-behind-the-brilliant-colors-and-sounds-173576">fireworks</a> and the <a href="https://www.gq.com/video/watch/the-breakdown-gq-the-breakdown-explosions">explosive special effects</a> in your favorite action movie. </p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/575457/original/file-20240213-30-hajfxf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A gold and white rocket, with flames coming out of its end, attached to a concrete scaffold." src="https://images.theconversation.com/files/575457/original/file-20240213-30-hajfxf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/575457/original/file-20240213-30-hajfxf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=750&fit=crop&dpr=1 600w, https://images.theconversation.com/files/575457/original/file-20240213-30-hajfxf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=750&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/575457/original/file-20240213-30-hajfxf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=750&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/575457/original/file-20240213-30-hajfxf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=943&fit=crop&dpr=1 754w, https://images.theconversation.com/files/575457/original/file-20240213-30-hajfxf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=943&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/575457/original/file-20240213-30-hajfxf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=943&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Propellants help rockets blast off.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/Rocket_propellant#/media/File:Delta_IV_launch_2013-08-28.jpg">U.S. Air Force/Joe Davila</a></span>
</figcaption>
</figure>
<p>Energetic materials come in many shapes and sizes, but they’re often in a solid form and release a lot of energy through <a href="https://www.nfpa.org/news-blogs-and-articles/blogs/2023/03/27/explosions-vs-deflagrations-vs-detonations">burning or exploding</a>, depending on their shape and the conditions they’re operating in. </p>
<p>I’m a <a href="https://www.technologyreview.com/innovator/monique-mcclain/">mechanical engineering professor</a> who studies <a href="https://scholar.google.com/citations?user=whbrwS0AAAAJ&hl=en">energetic materials</a>. Making energetic materials isn’t easy, but developments in 3D printing could make customization easier, while allowing for more potential scientific applications. </p>
<h2>The role of geometry</h2>
<p>How energetic materials are made affects the shapes that they come in and how they release energy over time. For example, solid rocket propellants are made <a href="https://www.youtube.com/watch?v=E0bnPb1WIuc">similar to a cake</a> where a stand mixer stirs the “batter,” which is mostly made of <a href="https://blogs.nasa.gov/Rocketology/tag/ammonium-perchlorate/">ammonium perchlorate, aluminum and a rubbery binder</a>, before it’s poured into a pan. The “cake” solidifies in the pan while it bakes in the oven. </p>
<p>Typically, rocket propellants have a cylindrical shape, but with a rod in the center. <a href="https://airandspace.si.edu/collection-objects/mandrel-rocket-manufacturing-solid-propellant-rocket-motor/nasm_A20060526000">The rod</a> often has a specific <a href="https://www.nakka-rocketry.net/th_grain.html">cross-sectional shape</a>, like a circle or a star. When the propellant solidifies, the rod is removed, leaving the core shape behind. </p>
<p>The core shape affects how the propellant burns, which can affect the <a href="https://www.youtube.com/watch?v=eVvIZ3f2tSU">thrust of the motor it’s used in</a>. Just by changing the central shape of the propellant, you can make a motor accelerate, slow down or maintain its speed over time. </p>
<p>But this traditional “cake baking” process limits the shapes that you can make. You must be able to remove the rod after the propellant solidifies, so if the rod’s shape is too complex, you might break the propellant, which could make it burn erratically. </p>
<p>Designing propellant shapes that make rockets go faster or fly farther is an active area of research, but engineers need new manufacturing methods to create these increasingly complex designs.</p>
<h2>3D printing to the rescue</h2>
<p><a href="https://www.pcmag.com/news/3d-printing-what-you-need-to-know">3D printing</a> has revolutionized manufacturing in a variety of ways, and researchers like me are trying to understand how it can improve the performance of energetic materials. 3D printing uses a printer to stack up material <a href="https://www.youtube.com/watch?v=Vx0Z6LplaMU">layer by layer</a> to build an object. </p>
<p>3D printing allows you to make custom shapes, print multiple types of material in one part, and save money and material. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/Vx0Z6LplaMU?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">3D printing can be cost- and time-efficient.</span></figcaption>
</figure>
<p>However, it is very challenging to 3D-print energetic materials for several reasons. Some <a href="https://ntrs.nasa.gov/citations/19720024117">energetic materials are very viscous</a>, which means it is very hard to squeeze that mixture out of a tube with a small nozzle. Imagine squeezing clay out of a small syringe – the material is too thick to easily move through the small hole. </p>
<p>In addition, energetic materials can be dangerous if handled improperly. They can ignite if there is <a href="https://www.osti.gov/servlets/purl/639810">too much heat</a> during the manufacturing process or during storage, or if they are exposed to a <a href="https://apps.dtic.mil/sti/tr/pdf/ADA322856.pdf">static electric shock</a>.</p>
<h2>Recent progress</h2>
<p>Despite this, researchers have made a lot of progress in the <a href="https://doi.org/10.1002/prep.201900060">past decade</a> to overcome some of these challenges. For example, scientists have 3D-printed <a href="https://engineering.purdue.edu/ME/News/inkjetprinted-thermite-combines-energetic-materials-and-additive-manufacturing">reactive inks onto electronics</a> to enable self-destruction if they fall into the wrong hands.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/8QNQRhBstRg?wmode=transparent&start=28" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Scientists are studying how to print thin layers of thermite, a type of energetic material, onto surfaces.</span></figcaption>
</figure>
<p>Theoretically, you could also 3D-print these inks strategically onto old satellites or the <a href="https://www.cnn.com/2022/02/02/world/nasa-international-space-station-retire-iss-scn/index.html">aging International Space Station</a> to break up these orbiting devices into <a href="https://arc.aiaa.org/doi/10.2514/6.2024-2162">small enough debris</a> that burns up in the atmosphere before hitting the ground. </p>
<p>Many researchers are looking into 3D-printing gun propellants. <a href="https://doi.org/10.1002/prep.201900176">Modifying the shape of gun propellants</a> could make bullets that can fly farther. </p>
<p>Others have sought to use 3D printing to reduce the environmental impact of <a href="https://serdp-estcp.mil/projects/details/a04a6382-e4d4-4e7e-b262-2febb6cae014/wp19-1246-project-overview">gun propellants</a> and <a href="https://serdp-estcp.mil/projects/details/7a5dc45b-a30b-485f-93ab-ec3731356b3c/wp19-1300-project-overview">igniters that require harsh solvents</a> to manufacture. These solvents are unsafe, difficult to dispose of and can harm <a href="https://www.epd.gov.hk/epd/english/environmentinhk/air/prob_solutions/vocs_smog.html">the environment</a> and <a href="https://www.epa.gov/indoor-air-quality-iaq/volatile-organic-compounds-impact-indoor-air-quality">peoples’ health</a>. </p>
<p>I showed that it is possible to <a href="https://www.purdue.edu/newsroom/releases/2018/Q2/now-you-can-3d-print-clay,-cookie-dough--or-solid-rocket-fuel.html">3D-print solid rocket propellants</a> that have similar properties to traditionally made propellants. With that research, we now have the opportunity to explore how <a href="https://doi.org/10.2514/1.B38282">propellants made of multiple materials burn</a>, which is new territory. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/OIdLg4zeGso?wmode=transparent&start=2" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">To 3D-print rocket propellants, you first need to figure out how to print very viscous materials.</span></figcaption>
</figure>
<p>For example, instead of using a rod to made a cross-sectional shape in a propellant, you could <a href="https://doi.org/10.2514/1.B38128">3D-print a highly reactive material</a> that you could add to the center. Instead of having to remove that center material, you could burn it up so fast that it leaves a core shape behind. The reactive material would also add energy to the propellant. This would eliminate the need to use and remove a rod to make a central core.</p>
<p>While much of this research is in its infancy, companies such as <a href="https://www.prnewswire.com/news-releases/x-bow-systems-launches-second-successful-bolt-rocket-301851088.html">X-Bow</a> have been 3D-printing propellants and conducting successful flight tests with these motors.</p>
<p>Finally, several researchers have studied how <a href="https://www.machinedesign.com/3d-printing-cad/article/21836373/a-look-inside-the-explosive-3dprinting-industry">3D-printed explosives</a> detonate. When the explosives are printed into a grid-shaped lattice, they react differently when their pores are filled with air or water. This process produces a safer “<a href="https://discover.lanl.gov/news/0317-high-explosives/">switchable” explosive</a> that does not react unless it is in a specific environment. </p>
<p>3D-printing energetic materials is still a new field. Scientists have a long way to go before we completely understand how <a href="https://doi.org/10.1002/prep.202380231">3D printing affects their safety and performance</a>. But every day, scientists like me are finding new ways to use 3D-printed energetics to serve crucial, and sometimes lifesaving, purposes.</p><img src="https://counter.theconversation.com/content/214126/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Monique McClain receives funding from Air Force Office of Scientific Research (AFOSR), Army Research Office (ARO), and National Aeronautics and Space Administration (NASA).</span></em></p>‘Energetic’ materials are ones that readily ignite or detonate. The shapes of those materials have a big effect on how they burn or blow up.Monique McClain, Assistant Professor of Mechanical Engineering, Purdue UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2114702024-01-24T13:29:42Z2024-01-24T13:29:42ZCombining two types of molecular boron nitride could create a hybrid material used in faster, more powerful electronics<figure><img src="https://images.theconversation.com/files/569648/original/file-20240116-15-csiabm.jpg?ixlib=rb-1.1.0&rect=8%2C17%2C5682%2C4471&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Hexagonal boron nitride, also known as 'white graphene.'</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/boron-nitride-monolayer-illustration-royalty-free-image/1161024204?phrase=boron+nitride&adppopup=true">Robert Brook/Science Photo Library via Getty Images</a></span></figcaption></figure><p>In chemistry, structure is everything. Compounds with the same chemical formula can have different properties depending on the arrangement of the molecules they’re made of. And compounds with a different chemical formula but a similar molecular arrangement can have similar properties.</p>
<p><a href="https://www.sciencedirect.com/topics/chemistry/graphene">Graphene</a> and a form of boron nitride called hexagonal boron nitride fall into the latter group. Graphene is made up of carbon atoms. Boron nitride, BN, is composed of boron and nitrogen atoms. While their chemical formulas differ, <a href="https://doi.org/10.1063/PT.3.3297">they have a similar structure</a> – so similar that many chemists call hexagonal boron nitride “white graphene.”</p>
<p>Carbon-based graphene has <a href="https://theconversation.com/graphene-is-a-proven-supermaterial-but-manufacturing-the-versatile-form-of-carbon-at-usable-scales-remains-a-challenge-194238">lots of useful properties</a>. It’s thin but strong, and it conducts heat and electricity very well, making it ideal for use in electronics.</p>
<p>Similarly, hexagonal boron nitride has a host of properties similar to graphene that could improve biomedical imaging and drug delivery, as well as computers, smartphones and LEDs. <a href="https://doi.org/10.1038/nmat2711">Researchers have studied</a> this type of boron nitride for many years.</p>
<p>But, hexagonal boron nitride isn’t the only useful form this compound comes in.</p>
<p>As <a href="https://scholar.google.com/citations?user=S5oLGEgAAAAJ&hl=en">materials engineers</a>, <a href="https://ajayan.rice.edu/">our research team</a> has been investigating another type of boron nitride called cubic boron nitride. We want to know if combining the properties of hexagonal boron nitride with cubic boron nitride could open the door to <a href="https://www.azom.com/article.aspx?ArticleID=78">even more useful applications</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/569649/original/file-20240116-15-c9h3ox.gif?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Molecular structures of molecules, with atoms represented as blue spheres and bonds represented by gray lines connecting them. The left structure is in the shape of the cube, the right in flat sheets of hexagons." src="https://images.theconversation.com/files/569649/original/file-20240116-15-c9h3ox.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/569649/original/file-20240116-15-c9h3ox.gif?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=227&fit=crop&dpr=1 600w, https://images.theconversation.com/files/569649/original/file-20240116-15-c9h3ox.gif?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=227&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/569649/original/file-20240116-15-c9h3ox.gif?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=227&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/569649/original/file-20240116-15-c9h3ox.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=285&fit=crop&dpr=1 754w, https://images.theconversation.com/files/569649/original/file-20240116-15-c9h3ox.gif?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=285&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/569649/original/file-20240116-15-c9h3ox.gif?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=285&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Cubic boron nitride, shown on the left, and hexagonal boron nitride, shown on the right.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Structures_cub_hex_BN.gif">Oddball/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-sa/4.0/">CC BY-NC-SA</a></span>
</figcaption>
</figure>
<h2>Hexagonal versus cubic</h2>
<p>Hexagonal boron nitride is, as you might guess, boron nitride molecules arranged in the shape of a flat hexagon. It looks honeycomb-shaped, like graphene. Cubic boron nitride has a <a href="https://www.azom.com/article.aspx?ArticleID=78">three-dimensional lattice structure</a> and looks like a diamond at the molecular level.</p>
<p>H-BN is thin, soft and used in cosmetics to give them a silky texture. It doesn’t melt or degrade even under extreme heat, which also makes it useful in electronics and other applications. Some scientists predict it could be used to build a <a href="https://doi.org/10.1016/j.cej.2020.127802">radiation shield</a> for spacecraft.</p>
<p>C-BN is hard and resistant. It’s used in manufacturing to make cutting tools and drills, and it can keep its sharp edge even at high temperatures. It can also help dissipate heat in electronics.</p>
<p>Even though h-BN and c-BN might seem different, when put together, <a href="https://doi.org/10.1021/acs.nanolett.3c01537">our research has found</a> they hold even more potential than either on its own.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/566921/original/file-20231220-23-komtmy.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Two white powders, the top labeled 'hexagonal boron nitride' and the bottom labeled 'cubic boron nitride' with a circle between them labeled 'mixed phase boron nitride.' The bottom powder is slightly more brown and more clumpy." src="https://images.theconversation.com/files/566921/original/file-20231220-23-komtmy.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/566921/original/file-20231220-23-komtmy.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=557&fit=crop&dpr=1 600w, https://images.theconversation.com/files/566921/original/file-20231220-23-komtmy.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=557&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/566921/original/file-20231220-23-komtmy.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=557&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/566921/original/file-20231220-23-komtmy.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=700&fit=crop&dpr=1 754w, https://images.theconversation.com/files/566921/original/file-20231220-23-komtmy.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=700&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/566921/original/file-20231220-23-komtmy.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=700&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The two forms of boron nitride have some similarities and some differences, but when combined, they can create a substance with a variety of scientific applications.</span>
<span class="attribution"><span class="source">Abhijit Biswas</span></span>
</figcaption>
</figure>
<p>Both types of boron nitride conduct heat and can provide electrical insulation, but one, h-BN, is soft, and the other, c-BN, is hard. So, we wanted to see if they could be used together to create materials with interesting properties.</p>
<p>For example, combining their different behaviors could make a coating material effective for high temperature structural applications. C-BN could provide strong adhesion to a surface, while h-BN’s lubricating properties could resist wear and tear. Both together would keep the material from overheating.</p>
<h2>Making boron nitride</h2>
<p>This class of materials doesn’t occur naturally, so scientists must make it in the lab. In general, high-quality c-BN has been difficult to synthesize, whereas h-BN is relatively easier to make as high-quality films, using what are called vapor phase deposition methods. </p>
<p>In vapor phase deposition, we heat up boron and nitrogen-containing materials until they evaporate. The evaporated molecules then get deposited onto a surface, cool down, bond together and form a thin film of BN.</p>
<p>Our research team has worked on combining h-BN and c-BN using <a href="https://doi.org/10.1021/nl1022139">similar processes</a> to vapor phase deposition, but we can also <a href="https://doi.org/10.1021/acs.nanolett.3c01537">mix powders of the two together</a>. The idea is to build a material with the right mix of h-BN and c-BN for thermal, mechanical and electronic properties that we can fine-tune.</p>
<p>Our team has found the composite substance made from combining both forms of BN together has a variety of potential applications. When you point a laser beam at the substance, it flashes brightly. Researchers could use this property to create display screens and improve radiation therapies in the medical field. </p>
<p>We’ve also found we can tailor how heat-conductive the composite material is. This means engineers could use this BN composite in <a href="https://doi.org/10.1021/acs.nanolett.3c01537">machines that manage heat</a>. The next step is trying to manufacture large plates made of a h-BN and c-BN composite. If done precisely, we can tailor the mechanical, thermal and optical properties to specific applications.</p>
<p>In electronics, h-BN could <a href="https://doi.org/10.1063/PT.3.3297">act as a dielectric – or insulator – alongside graphene</a> in certain, low-power electronics. As a dielectric, h-BN would help electronics operate efficiently and keep their charge. </p>
<p>C-BN could work alongside diamond to create <a href="https://www.nrel.gov/materials-science/wide-bandgap-semiconductors.html">ultrawide band gap materials</a> that allow electronic devices to work at a much higher power. Diamond and c-BN both conduct heat well, and together they could help cool down these <a href="https://doi.org/10.1002/aelm.201600501">high-power devices</a>, which generate lots of extra heat.</p>
<p>H-BN and c-BN separately could lead to electronics that perform exceptionally well in different contexts – together, they have a host of potential applications, as well. </p>
<p>Our BN composite could improve heat spreaders and insulators, and it could work in energy storage machines like supercapacitors, which are <a href="https://www.azonano.com/article.aspx?ArticleID=6643">fast-charging energy storage devices</a>, and rechargeable batteries.</p>
<p>We’ll continue <a href="https://www.preciseceramic.com/blog/boron-nitride-the-superhero-material-of-the-future.html">studying BN’s properties</a>, and how we can use it in lubricants, coatings and wear-resistant surfaces. Developing ways to scale up production will be key for <a href="https://www.linkedin.com/pulse/global-boron-nitride-market-2024-share-future-trends-d1uwf/?published=t">exploring its applications</a>, from materials science to electronics and even environmental science.</p><img src="https://counter.theconversation.com/content/211470/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Pulickel Ajayan receives funding from the Army Research Laboratory and the Army Research Office. </span></em></p><p class="fine-print"><em><span>Abhijit Biswas does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Two forms of the same boron nitride molecules couldn’t look and act more different – but combining them could lead to applications that have the best of both worlds.Pulickel Ajayan, Professor of Materials Science and NanoEngineering, Rice UniversityAbhijit Biswas, Research Scientist in Materials Science and Nanoengineering, Rice UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2133262023-11-07T13:38:21Z2023-11-07T13:38:21ZEngineered ‘living materials’ could help clean up water pollution one day<figure><img src="https://images.theconversation.com/files/556959/original/file-20231031-27-mncpgs.jpg?ixlib=rb-1.1.0&rect=18%2C0%2C2048%2C1358&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Researchers at the University of California, San Diego have developed a new 'living' material.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/jsoe/53172954946/in/album-72177720311058323/">David Baillot/UC San Diego Jacobs School of Engineering</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span></figcaption></figure><p>Water pollution is a growing concern globally, with <a href="https://doi.org/10.1016/j.oneear.2022.01.005">research estimating</a> that chemical industries discharge <a href="https://cleanwaterinternational.org/water-pollution-everything-we-need-to-know/amp/">300-400 megatonnes</a> (600-800 billion pounds) of industrial waste into bodies of water each year. </p>
<p>As a <a href="https://www.pokorskilab.com/">team of materials scientists</a>, we’re working on an engineered “living material” that may be able to transform chemical dye pollutants from the <a href="https://www.cnn.com/2023/04/21/middleeast/textile-wastewater-pollutant-cleaner-hnk-scn-spc-intl/index.html">textile industry</a> into harmless substances.</p>
<p><a href="https://www.safewater.org/fact-sheets-1/2017/1/23/industrial-waste">Water pollution</a> is both an environmental and humanitarian issue that can affect ecosystems and human health alike. We’re hopeful that the materials we’re developing could be one tool available to help combat this problem.</p>
<h2>Engineering a living material</h2>
<p>The “<a href="https://www.nature.com/collections/fhcabedjaa">engineered living material</a>” our team has been working on <a href="https://my.clevelandclinic.org/health/articles/24494-bacteria">contains programmed bacteria</a> embedded in a soft hydrogel material. We first published a paper showing the potential effectiveness of this material in <a href="https://doi.org/10.1038/s41467-023-40265-2">Nature Communications</a> in August 2023.</p>
<p><a href="https://www.snexplores.org/article/explainer-what-is-a-hydrogel">The hydrogel</a> that forms the base of the material has similar properties to Jell-O – it’s soft and made mostly of water. Our particular hydrogel is made from a natural and biodegradable <a href="https://dalchem.com.au/how-to/what-is-alginate/">seaweed-based polymer called alginate</a>, an ingredient common <a href="https://kitchen-theory.com/sodium-alginate-spherification/">in some foods</a>.</p>
<p>The alginate hydrogel provides a solid physical support for bacterial cells, similar to how <a href="https://theconversation.com/mapping-the-100-trillion-cells-that-make-up-your-body-103078">tissues support cells</a> in the human body. We intentionally chose this material so that the bacteria we embedded could grow and flourish. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/556960/original/file-20231031-15-o1t0v7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A green polymer, arranged in a square with a 5 by 5 grid of smaller squares, sits on a clear surface." src="https://images.theconversation.com/files/556960/original/file-20231031-15-o1t0v7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/556960/original/file-20231031-15-o1t0v7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/556960/original/file-20231031-15-o1t0v7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/556960/original/file-20231031-15-o1t0v7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/556960/original/file-20231031-15-o1t0v7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/556960/original/file-20231031-15-o1t0v7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/556960/original/file-20231031-15-o1t0v7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The grid shape of the material helps the bacteria take in carbon dioxide.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/jsoe/53173442373/in/album-72177720311058323/">David Baillot/UC San Diego Jacobs School of Engineering</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span>
</figcaption>
</figure>
<p>We picked the seaweed-based alginate as the material base because it’s porous and can retain water. It also allows the <a href="https://www.microscopemaster.com/photosynthetic-bacteria.html">bacterial cells</a> to take in nutrients from the surrounding environment.</p>
<p>After we prepared the hydrogel, we embedded photosynthetic – or sunlight-capturing – bacteria called <a href="https://www.britannica.com/science/blue-green-algae">cyanobacteria</a> into the gel.</p>
<p>The cyanobacteria embedded in the material still needed to take in light and carbon dioxide <a href="https://education.nationalgeographic.org/resource/photosynthesis/">to perform photosynthesis</a>, which keeps them alive. The hydrogel was porous enough to allow that, but to make the configuration as efficient as possible, we <a href="https://www.cellink.com/3d-bioprinting/">3D-printed</a> the gel into custom shapes – grids and honeycombs. These structures have a higher surface-to-volume ratio that allow more light, CO₂ and nutrients to come into the material. </p>
<p>The cells were happy in that geometry. We observed higher cell growth and density over time in the alginate gels in the grid or honeycomb structures when compared with the default disc shape.</p>
<h2>Cleaning up dye</h2>
<p>Like all other bacteria, cyanobacteria has different <a href="https://www.ibiology.org/bioengineering/genetic-circuits/">genetic circuits</a>, which tell the cells what outputs to produce. Our team <a href="https://www.britannica.com/science/genetic-engineering/Process-and-techniques">genetically engineered</a> the bacterial <a href="https://www.newscientist.com/definition/dna/">DNA</a> so that the cells created a specific enzyme <a href="https://en.wikipedia.org/wiki/Laccase">called laccase</a>. </p>
<p>The laccase enzyme produced by the cyanobacteria works by performing a chemical reaction with a pollutant that transforms it into a form that’s no longer functional. By breaking the chemical bonds, it can make a toxic pollutant nontoxic. The enzyme is regenerated at the end of the reaction, and it goes off to complete more reactions. </p>
<p>Once we’d embedded these laccase-creating cyanobacteria into the alginate hydrogel, we put them in a solution made up of <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10532910/">industrial dye pollutant</a> to see if they could clean up the dye. In this test, we wanted to see if our material could change the structure of the dye so that it went from being colored to uncolored. But, in other cases, the material could potentially change a chemical structure to go from toxic to nontoxic. </p>
<p>The dye we used, <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10532910/">indigo carmine</a>, is a common industrial wastewater pollutant usually found in the water near textile plants – it’s the main pigment in blue jeans. We found that our material took all the color out of the bulk of the dye over about 10 days.</p>
<p>This is good news, but we wanted to make sure that our material wasn’t adding waste to polluted water by leaching bacterial cells. So, we also engineered the bacteria to produce a protein that could damage the cell membrane of the bacteria – a programmable kill switch. </p>
<p>The genetic circuit was programmed to respond to a harmless chemical, called <a href="https://academic.oup.com/pcp/article/54/10/1724/1908151">theophylline</a>, commonly found in caffeine, tea and chocolate. By adding theophylline, we could destroy bacterial cells at will. </p>
<p>The field of engineered living materials is still developing, but this just means there are plenty of opportunities to develop new materials with both living and nonliving components.</p><img src="https://counter.theconversation.com/content/213326/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jonathan K. Pokorski receives funding from the National Science Foundation and Department of Energy.</span></em></p><p class="fine-print"><em><span>Debika Datta does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>‘Living materials’ made with genetically engineered bacteria and Jell-O-like gel could make pollutants in water bodies nontoxic.Jonathan K. Pokorski, Professor of Nanoengineering, University of California, San DiegoDebika Datta, Postdoctoral Scholar in Nanoengineering, University of California, San DiegoLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2146142023-10-24T12:22:02Z2023-10-24T12:22:02ZSpace rocks and asteroid dust are pricey, but these aren’t the most expensive materials used in science<figure><img src="https://images.theconversation.com/files/552576/original/file-20231006-23-aam2il.jpg?ixlib=rb-1.1.0&rect=0%2C34%2C5751%2C3794&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Meteorites can get pricey, but they're not the most expensive material. </span> <span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/FranceMeteoriteAuction/e075e1b22656489db39610bafb0682af/photo?Query=meteorites&mediaType=photo&sortBy=&dateRange=Anytime&totalCount=341&currentItemNo=5&vs=true">AP Photo/Thibault Camus</a></span></figcaption></figure><p>After a journey of seven years and nearly 4 billion miles, <a href="https://science.nasa.gov/mission/osiris-rex">NASA’s OSIRIS-REx</a> <a href="https://www.space.com/osiris-rex-asteroid-samples-land-houston">spacecraft landed</a> gently in the Utah desert on the morning of Sept. 24, 2023, with a precious payload. <a href="https://science.nasa.gov/mission/osiris-rex">The spacecraft</a> brought back a sample from the asteroid Bennu.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/552573/original/file-20231006-27-cm9a07.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="An artist's illustration of a gray metallic spacecraft hovering above the dark surface of an asteroid, with an arm that reaches down to the surface." src="https://images.theconversation.com/files/552573/original/file-20231006-27-cm9a07.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/552573/original/file-20231006-27-cm9a07.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=376&fit=crop&dpr=1 600w, https://images.theconversation.com/files/552573/original/file-20231006-27-cm9a07.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=376&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/552573/original/file-20231006-27-cm9a07.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=376&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/552573/original/file-20231006-27-cm9a07.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=472&fit=crop&dpr=1 754w, https://images.theconversation.com/files/552573/original/file-20231006-27-cm9a07.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=472&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/552573/original/file-20231006-27-cm9a07.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=472&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">OSIRIS-REx collected a sample from the asteroid Bennu.</span>
<span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/20c047ec48f74f6995ffad6b0f54422c?ext=true">NASA/Goddard Space Flight Center via AP</a></span>
</figcaption>
</figure>
<p>Roughly half a pound of material collected from the <a href="https://science.nasa.gov/solar-system/asteroids/101955-bennu/facts/">85 million-ton asteroid</a> (77.6 billion kg) will help scientists learn about the <a href="https://solarsystem.nasa.gov/missions/osiris-rex/in-depth/">formation of the solar system</a>, including whether <a href="https://solarsystem.nasa.gov/asteroids-comets-and-meteors/asteroids/101955-bennu/in-depth/">asteroids like Bennu</a> include the chemical ingredients for life.</p>
<p>NASA’s mission was budgeted at <a href="https://www.asteroidmission.org/qa/">US$800 million</a> and will end up costing around <a href="https://www.planetary.org/space-policy/cost-of-osiris-rex">$1.16 billion</a> for <a href="https://www.nasa.gov/news-release/nasas-first-asteroid-sample-has-landed-now-secure-in-clean-room/">just under 9 ounces of sample</a> (255 g). But is this the most expensive material known? Not even close.</p>
<p>I’m a <a href="https://scholar.google.com/citations?user=OrRLRQ4AAAAJ&hl=en">professor of astronomy</a>. I use Moon and Mars rocks in my teaching and have a modest collection of meteorites. I marvel at the fact that I can hold in my hand something that is billions of years old from billions of miles away.</p>
<h2>The cost of sample return</h2>
<p>A handful of asteroid works out to $132 million <a href="https://www.hoodmwr.com/things-that-weigh-around-1-ounce/">per ounce</a>, or $4.7 million per gram. That’s about 70,000 times the <a href="https://goldprice.org/">price of gold</a>, which has been in the range of $1,800 to $2,000 per ounce ($60 to $70 per gram) for the past few years.</p>
<p>The first extraterrestrial material returned to Earth came from the Apollo program. Between 1969 and 1972, six Apollo missions brought back 842 pounds (382 kg) of <a href="https://curator.jsc.nasa.gov/lunar/">lunar samples</a>.</p>
<p>The <a href="https://www.planetary.org/space-policy/cost-of-apollo">total price tag</a> for the Apollo program, adjusted for inflation, was $257 billion. These Moon rocks were a relative bargain at $19 million per ounce ($674 thousand per gram), and of course Apollo had additional value in demonstrating technologies for human spaceflight. </p>
<p>NASA is planning to bring samples back from Mars in the early 2030s to see if any contain traces of ancient life. The <a href="https://mars.nasa.gov/msr/">Mars Sample Return</a> mission aims to return <a href="https://www.universetoday.com/161264/we-can-only-bring-30-samples-of-mars-back-to-earth-how-do-we-decide/">30 sample tubes</a> with a <a href="https://downloads.regulations.gov/NASA-2022-0002-0002/attachment_5.pdf">total weight of a pound</a> (450 g). The <a href="https://science.nasa.gov/mission/mars-2020-perseverance">Perseverance rover</a> has already <a href="https://www.universetoday.com/160109/perseverance-is-building-up-a-big-collection-of-mars-samples/">cached 10 of these samples</a>. </p>
<p>However, <a href="https://www.science.org/content/article/mars-sample-return-got-new-price-tag-it-s-big">costs have grown</a> because the mission is complex, involving multiple robots and spacecraft. Bringing back the samples could run $11 billion, putting their cost at $690 million per ounce ($24 million per gram), five times the unit cost of the Bennu samples.</p>
<h2>Some space rocks are free</h2>
<p>Some space rocks cost nothing. Almost 50 tons of free samples from the solar system <a href="https://science.nasa.gov/solar-system/meteors-meteorites/">rain down on the Earth</a> every day. Most burn up in the atmosphere, but if they reach the ground <a href="https://www.amnh.org/explore/news-blogs/on-exhibit-posts/meteor-meteorite-asteroid">they’re called meteorites</a>, and most of those come from asteroids. </p>
<p><a href="https://www.nhm.ac.uk/discover/types-of-meteorites.html">Meteorites can get costly</a> because it can be difficult to recognize and retrieve them. Rocks all look similar unless you’re a geology expert. </p>
<p>Most meteorites are stony, <a href="https://www.britannica.com/science/chondrite">called chondrites</a>, and they can be bought online for as little as $15 per ounce (50 cents per gram). Chondrites differ from normal rocks in containing <a href="https://www.amnh.org/exhibitions/permanent/meteorites/origins-of-the-solar-system/chondrules">round grains called chondrules</a> that formed as molten droplets in space at the birth of the solar system 4.5 billion years ago.</p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/552568/original/file-20231006-19-kgbnz8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A meteorite that looks like a long gray rock with dark gray veins running across it." src="https://images.theconversation.com/files/552568/original/file-20231006-19-kgbnz8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/552568/original/file-20231006-19-kgbnz8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=305&fit=crop&dpr=1 600w, https://images.theconversation.com/files/552568/original/file-20231006-19-kgbnz8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=305&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/552568/original/file-20231006-19-kgbnz8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=305&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/552568/original/file-20231006-19-kgbnz8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=384&fit=crop&dpr=1 754w, https://images.theconversation.com/files/552568/original/file-20231006-19-kgbnz8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=384&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/552568/original/file-20231006-19-kgbnz8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=384&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A chondrite from the Viñales meteorite, which originated from the asteroid belt between Mars and Jupiter.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Ordinary_chondrite_%28Vi%C3%B1ales_Meteorite%29_15.jpg">Ser Amantio di Nicolao/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p><a href="https://aerolite.org/shop/iron-meteorites/">Iron meteorites</a> are distinguished by a dark crust, caused by melting of the surface as they come through the atmosphere, and an internal pattern of long metallic crystals. They cost $50 per ounce ($1.77 per gram) or even higher. <a href="https://geology.com/meteorites/value-of-meteorites.shtml">Pallasites</a> are stony-iron meteorites laced with the mineral olivine. When cut and polished, they have a translucent yellow-green color and can cost over $1,000 per ounce ($35 per gram).</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/552571/original/file-20231006-21-vjnv0r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A brown-gray meteorite that's roughly circular with textured ridges" src="https://images.theconversation.com/files/552571/original/file-20231006-21-vjnv0r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/552571/original/file-20231006-21-vjnv0r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/552571/original/file-20231006-21-vjnv0r.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/552571/original/file-20231006-21-vjnv0r.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/552571/original/file-20231006-21-vjnv0r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/552571/original/file-20231006-21-vjnv0r.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/552571/original/file-20231006-21-vjnv0r.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">An iron meteorite.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Odessa_%28iron%29_meteorite.jpg">Llez/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>More than a few meteorites have reached us from the Moon and Mars. Close to 600 have been recognized as <a href="https://sites.wustl.edu/meteoritesite/items/lunar-meteorites/">coming from the Moon</a>, and <a href="https://www.catawiki.com/en/stories/4683-10-most-expensive-meteorites-ever-offered-up-on-earth">the largest</a>, weighing 4 pounds (1.8 kg), sold for a price that works out to be about $4,700 per ounce ($166 per gram). </p>
<p>About 175 meteorites are identified as <a href="https://www2.jpl.nasa.gov/snc/">having come from Mars</a>. <a href="https://aerolite.org/shop/mars-meteorites/">Buying one</a> would cost about $11,000 per ounce ($388 per gram). </p>
<p>Researchers can figure out <a href="https://science.nasa.gov/solar-system/meteors-meteorites/facts/">where meteorites come from</a> by using their landing trajectories to project their paths back to the asteroid belt or comparing their composition with different classes of asteroids. Experts can tell where Moon and Mars rocks come from by their geology and mineralogy.</p>
<p>The limitation of these “free” samples is that there is no way to know where on the Moon or Mars they came from, which limits their scientific usefulness. Also, they start to get contaminated as soon as they land on Earth, so it’s hard to tell if any microbes within them are extraterrestrial.</p>
<h2>Expensive elements and minerals</h2>
<p>Some elements and minerals are expensive because they’re scarce. Simple <a href="http://www.leonland.de/elements_by_price/en/list">elements in the periodic table</a> have low prices. Per ounce, carbon costs one-third of a cent, iron costs 1 cent, aluminum costs 56 cents, and even mercury is less than a dollar (per 100 grams, carbon costs $2.40, iron costs less than a cent and alumnium costs 19 cents). Silver is $14 per ounce (50 cents per gram), and gold, $1,900 per ounce ($67 per gram). </p>
<p><a href="https://alansfactoryoutlet.com/how-much-do-elements-cost-the-price-of-75-elements-per-kilogram/">Seven radioactive elements</a> are extremely rare in nature and so difficult to create in the lab that they eclipse the price of NASA’s Mars Sample Return. Polonium-209, the most expensive of these, costs $1.4 trillion per ounce ($49 billion per gram).</p>
<p>Gemstones can be expensive, too. <a href="https://www.gemsociety.org/article/emerald-jewelry-and-gemstone-information/">High-quality emeralds</a> are 10 times the <a href="https://goldprice.org/">price of gold</a>, and <a href="https://ajediam.com/diamond-prices/white-natural-diamond/">white diamonds</a> are 100 times the price of gold. </p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/554101/original/file-20231016-15-63z3ek.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A circular white diamond sitting on a white surface." src="https://images.theconversation.com/files/554101/original/file-20231016-15-63z3ek.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/554101/original/file-20231016-15-63z3ek.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=727&fit=crop&dpr=1 600w, https://images.theconversation.com/files/554101/original/file-20231016-15-63z3ek.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=727&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/554101/original/file-20231016-15-63z3ek.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=727&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/554101/original/file-20231016-15-63z3ek.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=914&fit=crop&dpr=1 754w, https://images.theconversation.com/files/554101/original/file-20231016-15-63z3ek.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=914&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/554101/original/file-20231016-15-63z3ek.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=914&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">High-quality white diamonds can cost millions of dollars.</span>
<span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/eeaab33d812a487ebfd2e5a76a25eb03?ext=true">AP Photo/Mary Altaffer</a></span>
</figcaption>
</figure>
<p>Some diamonds have a boron impurity that gives them a <a href="https://www.diamonds.pro/education/blue/">vivid blue hue</a>. They’re found in only a handful of mines worldwide, and at <a href="https://www.usatoday.com/story/money/2022/04/28/worlds-largest-blue-diamond-sells/9567999002/">$550 million per ounce</a> ($19 million per gram) they rival the cost of the upcoming Mars samples – an ounce is 142 carats, but very few gems are that large. </p>
<p>The <a href="https://www.sciencealert.com/scientists-create-world-s-most-expensive-material-valued-at-145-million-per-gram">most expensive synthetic material</a> is a tiny spherical “cage” of carbon with a nitrogen atom trapped inside. The atom inside the cage is extremely stable, so can be used for timekeeping. <a href="https://arstechnica.com/science/2015/12/oxford-company-now-selling-endohedral-fullerenes-priced-at-110-million-per-gram/">Endohedral fullerenes</a> are made of carbon material that may be used to create extremely accurate atomic clocks. They can cost $4 billion per ounce ($141 million per gram).</p>
<h2>Most expensive of all</h2>
<p><a href="https://www.livescience.com/32387-what-is-antimatter.html">Antimatter</a> occurs in nature, but it’s exceptionally rare because any time an antiparticle is created it quickly annihilates with a particle and produces radiation. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/7MkfMGzMcf8?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">At CERN’s ‘antimatter factory,’ scientists create antimatter in very small quantities.</span></figcaption>
</figure>
<p>The <a href="https://royalsocietypublishing.org/doi/10.1098/rsta.2010.0026">particle accelerator at CERN</a> can produces 10 million antiprotons per minute. That sounds like a lot, but <a href="https://archive.ph/6RUrA">at that rate</a> it would take billions of years and cost a billion billion (10<sup>18</sup>) dollars to generate an ounce (3.5 x 10<sup>16</sup> dollars per gram). </p>
<p><a href="https://www.newscientist.com/article/mg24232342-600-how-star-treks-warp-drives-touch-on-one-of-physics-biggest-mysteries/">Warp drives</a> as envisaged by “Star Trek,” which are powered by matter-antimatter annihilation, will have to wait.</p><img src="https://counter.theconversation.com/content/214614/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Chris Impey receives funding from the National Science Foundation. </span></em></p>Some space rocks you can get for free – if you know how to identify them. Rarer materials cost more, and the asteroid sample NASA just brought back has a high price tag.Chris Impey, University Distinguished Professor of Astronomy, University of ArizonaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2156522023-10-19T19:24:01Z2023-10-19T19:24:01ZNew class of recyclable polymer materials could one day help reduce single-use plastic waste<figure><img src="https://images.theconversation.com/files/554111/original/file-20231016-23-gcf4fp.jpg?ixlib=rb-1.1.0&rect=79%2C3%2C2038%2C1397&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Single-use plastics. </span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/various-types-of-plastic-trash-on-the-grass-plastic-royalty-free-image/1325351577?phrase=plastic&adppopup=true">Anton Petrus/Moment</a></span></figcaption></figure><p><a href="https://www.unep.org/interactives/beat-plastic-pollution/">Hundreds of millions of tons</a> of single-use plastic ends up in landfills every year, and even the small percentage of plastic that gets recycled can’t last forever. But our group of materials scientists has developed a new method for creating and deconstructing polymers that could lead to more easily recycled plastics – ones that don’t require you to carefully sort out all your recycling on trash day. </p>
<p>In the century since their conception, people have come to understand the enormous impacts – beneficial as well as detrimental – plastics have on human lives and the environment. As a <a href="https://miyakelab.colostate.edu/">group of polymer scientists</a> dedicated to inventing sustainable solutions for real-world problems, we set out to tackle this issue by rethinking the way polymers are designed and making plastics with recyclability built right in. </p>
<h2>Why use plastics, anyway?</h2>
<p>Everyday items including milk jugs, grocery bags, takeout containers and even ropes are made from a class of <a href="https://www.polymersolutions.com/blog/top-types-of-polyolefins-the-most-common-kind-of-plastics/">polymers called polyolefins</a>. Polyolefins make up around <a href="https://ourworldindata.org/grapher/plastic-waste-polymer">half of the plastics</a> produced and disposed of every year. </p>
<p>These polymers are used in plastics commonly labeled as HDPE, LLDPE or PP, or by their recycling codes #2, #4 and #5, respectively. These plastics are incredibly durable because the <a href="https://doi.org/10.1021/acssuschemeng.9b06635">chemical bonds</a> that make them up are extremely stable. But in a world set up for single-use consumption, this is no longer a design feature but rather a design flaw. </p>
<p><iframe id="2k7dQ" class="tc-infographic-datawrapper" src="https://datawrapper.dwcdn.net/2k7dQ/1/" height="400px" width="100%" style="border: none" frameborder="0"></iframe></p>
<p>Imagine if half of the plastics used today were recyclable by twice as many processes as they are now. While that wouldn’t get the recycling rate to 100%, a jump from single digits – <a href="https://www.energy.gov/articles/department-energy-releases-plastics-innovation-challenge-draft-roadmap-and-request">currently around 9%</a> – to double digits would make a big dent in the plastics produced, the plastics accumulated in the environment and their capacity for recycling and reuse. </p>
<h2>Recycling methods we already have</h2>
<p>Even the plastics that make it to a recycling facility <a href="https://ellenmacarthurfoundation.org/plastics-and-the-circular-economy-deep-dive">can’t be reused</a> in exactly the same way they were used before – the recycling process degrades the material, so it loses utility and value. Instead of making a plastic cup that is downgraded each time it gets recycled, manufacturers could potentially make plastics once, collect them and reuse them on and on.</p>
<p>Conventional recycling requires careful sorting of all the collected materials, which can be hard with so many different plastics. Here in the U.S., collection happens mainly through <a href="https://www.container-recycling.org/index.php/issues/single-stream-recycling">single stream recycling</a> – everything from metal cans, glass bottles, cardboard boxes and plastic cups end up in the same bin. Separating paper from metal doesn’t require complex technology, but sorting a polypropylene container from a polyethylene milk jug is hard to do without the occasional mistake. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/554113/original/file-20231016-20-hwyi6k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Two workers, in bright yellow, stand at a conveyor belt covered in plastics in a recycling facility." src="https://images.theconversation.com/files/554113/original/file-20231016-20-hwyi6k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/554113/original/file-20231016-20-hwyi6k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/554113/original/file-20231016-20-hwyi6k.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/554113/original/file-20231016-20-hwyi6k.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/554113/original/file-20231016-20-hwyi6k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/554113/original/file-20231016-20-hwyi6k.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/554113/original/file-20231016-20-hwyi6k.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Recycling workers sort through materials.</span>
<span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/OhioRecycling/d1c2014b8c194d55b9f06a328b2dd4a5/photo?Query=recycling%20plant&mediaType=photo&sortBy=&dateRange=Anytime&totalCount=181&currentItemNo=22&vs=true">AP Photo/Mark Gillispie</a></span>
</figcaption>
</figure>
<p>When two different plastics are mixed together during recycling, their useful properties are hugely reduced – to the point of <a href="https://www.scientificamerican.com/article/why-its-so-hard-to-recycle-plastic/">making them useless</a>. </p>
<p>But say you can recycle one of these plastics by a different method, so it doesn’t end up contaminating the recycling stream. When we mixed samples of polypropylene with a polymer we made, we were <a href="https://doi.org/10.1126/science.adh3353">still able to depolymerize</a> – or break down the material – and regain our building blocks without chemically affecting the polypropylene. This indicated that a contaminated waste stream could still recover its value, and the material in it could go on to be recycled, either mechanically or chemically. </p>
<h2>Plastics we need − but more recyclable</h2>
<p>In <a href="https://doi.org/10.1126/science.adh3353">a study published in October 2023</a>, our team developed a series of polymers with only two simple building blocks – one soft polymer and one hard polymer – that mimicked polyolefins but could also be chemically recycled.</p>
<p>Connecting two different polymers together multiple times until they form a single, long molecule creates what’s called a <a href="https://doi.org/10.1021/jacsau.1c00500">multiblock polymer</a>. Just by adjusting how much of each polymer type goes into the multiblock polymer, our team created a wide range of materials with properties that spanned across polyolefin types. But creating these multiblock polymers is easier said than done. </p>
<p>To link these hard and soft polymers, we <a href="https://doi.org/10.1126/science.adh3353">adapted a technique</a> that had previously been used only on very small molecules. This method is improved relative to traditional methods of making polymers in a step-by-step fashion, developed in the 1920s, where the reactive groups on the end of the molecules need to be exactly matched. </p>
<p>In our method, the reactive groups are now the same as each other, meaning we didn’t have to worry about pairing the ends of each building block to make polymers that can compete with the polyolefins we already use. Using the same strategy, applied in reverse by adding hydrogen, we could disconnect the polymers back into their building blocks and easily separate them to use again. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/554857/original/file-20231019-21-9enk8w.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A graph showing a steady increase in single-use plastic use across all plastic types shown, from X to projected in 2050." src="https://images.theconversation.com/files/554857/original/file-20231019-21-9enk8w.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/554857/original/file-20231019-21-9enk8w.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=302&fit=crop&dpr=1 600w, https://images.theconversation.com/files/554857/original/file-20231019-21-9enk8w.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=302&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/554857/original/file-20231019-21-9enk8w.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=302&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/554857/original/file-20231019-21-9enk8w.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=380&fit=crop&dpr=1 754w, https://images.theconversation.com/files/554857/original/file-20231019-21-9enk8w.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=380&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/554857/original/file-20231019-21-9enk8w.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=380&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Realized and predicted production of commodity plastics through 2050.</span>
<span class="attribution"><a class="source" href="https://www.energy.gov/sites/default/files/2021/01/f82/Plastics%20Innovation%20Challenge%20Draft%20Roadmap.pdf">International Energy Agency</a></span>
</figcaption>
</figure>
<p>With an almost <a href="https://www.reuters.com/business/environment/plastic-consumption-course-nearly-double-by-2050-research-2023-02-27/">twofold increase in annual plastic use</a> projected through 2050, the complexity and quantity of plastic recycling will only increase. It’s an important consideration when designing new materials and products. </p>
<p>Using just two building blocks to make plastics that have a huge variety of properties can go a long way toward reducing and streamlining the number of different plastics used to make the products we need. Instead of needing one plastic to make something pliable, another for something stiff, and a third, fourth and fifth for properties in between, we could control the behavior of plastics by just changing how much of each building block is there.</p>
<p>Although we’re still in the process of answering some big questions about these polymers, we believe this work is a step in the right direction toward more sustainable plastics. </p>
<p>We were <a href="https://doi.org/10.1126/science.adh3353">able to create materials</a> that mimic the properties of plastics the world relies on, and our sights are now set on creating plastic compositions that you couldn’t with existing methods.</p><img src="https://counter.theconversation.com/content/215652/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Katherine Harry receives funding from RePLACE (Redesigning Polymers to Leverage a Circular Economy) funded by the Office of Science of the US Department of Energy.</span></em></p><p class="fine-print"><em><span>Emma Rettner receives funding from RePLACE (Redesigning Polymers to Leverage a Circular Economy) funded by the Office of Science of the US Department of Energy.</span></em></p>A team of scientists has developed a method for creating a new class of plastic materials that are potentially more recyclable than single-use plastics.Katherine Harry, PhD Student in Chemistry, Colorado State UniversityEmma Rettner, PhD Candidate in Materials Science and Engineering, Colorado State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2150152023-10-04T21:19:46Z2023-10-04T21:19:46ZQuantum dots are part of a revolution in engineering atoms in useful ways – Nobel Prize for chemistry recognizes the power of nanotechnology<figure><img src="https://images.theconversation.com/files/552184/original/file-20231004-19-i1snbm.jpg?ixlib=rb-1.1.0&rect=143%2C24%2C3655%2C2727&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Flasks of quantum dots fluorescing at the Nobel Prize announcement.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/laboratory-flasks-are-used-for-explanation-during-the-news-photo/1705001725">Jonathan Nackstrand/AFP via Getty Images</a></span></figcaption></figure><p>The 2023 Nobel Prize for chemistry <a href="https://www.nobelprize.org/prizes/chemistry/2007/summary/">isn’t the</a> <a href="https://www.nobelprize.org/prizes/physics/1986/summary/">first Nobel</a> <a href="https://www.nobelprize.org/prizes/chemistry/2010/summary/">awarded for</a> <a href="https://www.nobelprize.org/prizes/chemistry/2016/summary/">research in</a> <a href="https://www.nobelprize.org/prizes/chemistry/1996/summary/">nanotechnology</a>. But it is perhaps the most colorful application of the technology to be associated with the accolade.</p>
<p>This year’s prize recognizes <a href="https://scholar.google.com/citations?user=8086TkwAAAAJ&hl=en&oi=ao">Moungi Bawendi</a>, <a href="https://scholar.google.com/citations?user=GT0oh5QAAAAJ&hl=en&oi=ao">Louis Brus</a> and <a href="https://www.nobelprize.org/prizes/chemistry/2023/ekimov/facts">Alexei Ekimov</a> for the <a href="https://www.nobelprize.org/prizes/chemistry/2023/press-release/">discovery and development of quantum dots</a>. For many years, these <a href="https://doi.org/10.1021/acsanm.0c01386">precisely constructed nanometer-sized particles</a> – just a few hundred thousandths the width of a human hair in diameter – were the darlings of nanotechnology pitches and presentations. As a <a href="https://scholar.google.com/citations?user=b8NhWc4AAAAJ&hl=en">researcher</a> and <a href="https://en.wikipedia.org/wiki/Andrew_D._Maynard">adviser</a> on nanotechnology, <a href="https://2020science.org/wp-content/uploads/2009/01/maynard-ucla-090417-handouts.pdf">I’ve even used them myself</a> when talking with developers, policymakers, advocacy groups and others about the promise and perils of the technology.</p>
<p>The origins of nanotechnology predate Bawendi, Brus and Ekimov’s work on quantum dots – the physicist Richard Feynman speculated on what could be possible through nanoscale engineering <a href="http://calteches.library.caltech.edu/1976/">as early as 1959</a>, and engineers like Erik Drexler were speculating about the possibilities of atomically precise manufacturing <a href="https://www.penguinrandomhouse.com/books/42881/engines-of-creation-by-k-eric-drexler/">in the the 1980s</a>. However, this year’s trio of Nobel laureates were part of the earliest wave of modern nanotechnology where researchers began <a href="https://andrewmaynard.substack.com/p/living-in-a-material-world">putting breakthroughs in material science to practical use</a>.</p>
<p>Quantum dots brilliantly <a href="https://www.britannica.com/science/fluorescence">fluoresce</a>: They absorb one color of light and reemit it nearly instantaneously as another color. A vial of quantum dots, when illuminated with broad spectrum light, shines with a single vivid color. What makes them special, though, is that their color is determined by how large or small they are. Make them small and you get an intense blue. Make them larger, though still nanoscale, and the color shifts to red.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/552172/original/file-20231004-26-sy0ozo.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="diagram of colorful circles of different sizes" src="https://images.theconversation.com/files/552172/original/file-20231004-26-sy0ozo.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/552172/original/file-20231004-26-sy0ozo.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=186&fit=crop&dpr=1 600w, https://images.theconversation.com/files/552172/original/file-20231004-26-sy0ozo.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=186&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/552172/original/file-20231004-26-sy0ozo.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=186&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/552172/original/file-20231004-26-sy0ozo.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=234&fit=crop&dpr=1 754w, https://images.theconversation.com/files/552172/original/file-20231004-26-sy0ozo.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=234&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/552172/original/file-20231004-26-sy0ozo.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=234&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The wavelength of light a quantum dot emits depends on its size.</span>
<span class="attribution"><a class="source" href="https://doi.org/10.3389/fnins.2015.00480">Maysinger, Ji, Hutter, Cooper</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>This property has led to many arresting images of rows of vials containing quantum dots of different sizes going from a striking blue on one end, through greens and oranges, to a vibrant red at the other. So eye-catching is this demonstration of the power of nanotechnology that, in the early 2000s, quantum dots became iconic of the strangeness and novelty of nanotechnology.</p>
<p>But, of course, quantum dots are more than a visually attractive parlor trick. They demonstrate that unique, controllable and useful interactions between matter and light can be achieved through engineering the physical form of matter – modifying the size, shape and structure of objects, for instance – rather than playing with the chemical bonds between atoms and molecules. The distinction is an important one, and it’s at the heart of modern nanotechnology.</p>
<h2>Skip chemical bonds, rely on quantum physics</h2>
<p>The wavelengths of light that a material absorbs, reflects or emits are usually determined by the chemical bonds that bind its constituent atoms together. <a href="https://www.sciencedirect.com/topics/engineering/synthetic-dye">Play with the chemistry of a material</a> and it’s possible to fine-tune these bonds so that they give you the colors you want. For instance, some of the earliest dyes <a href="https://thedreamstress.com/2013/09/terminology-what-are-aniline-dyes-or-the-history-of-mauve-and-mauveine/">started with a clear substance such as aniline</a>, transformed through chemical reactions to the desired hue.</p>
<p>It’s an effective way to work with light and color, but it also leads to products that <a href="https://www.sciencemuseum.org.uk/objects-and-stories/chemistry/colourful-chemistry-artificial-dyes">fade over time as those bonds degrade</a>. It also frequently involves using chemicals that are <a href="https://doi.org/10.1016/B978-0-12-822850-0.00013-2">harmful to humans and the environment</a>.</p>
<p>Quantum dots work differently. Rather than depending on chemical bonds to determine the wavelengths of light they absorb and emit, they rely on very small clusters of semiconducting materials. It’s the <a href="https://www.britishcouncil.org/voices-magazine/what-quantum-dot">quantum physics of these clusters</a> that then determines what wavelengths of light are emitted – and this in turn depends on how large or small the clusters are.</p>
<p>This ability to tune how a material behaves by simply changing its size is a game changer when it comes to the intensity and quality of light that quantum dots can produce, as well as their resistance to bleaching or fading, their novel uses and – if engineered smartly – their toxicity.</p>
<p>Of course, few materials are completely nontoxic, and quantum dots are no exception. Early quantum dots were often based on cadmium selenide for instance – the component materials of which are toxic. However, the <a href="https://theconversation.com/are-quantum-dot-tvs-and-their-toxic-ingredients-actually-better-for-the-environment-35953">potential toxicity of quantum dots needs to be balanced</a> by the likelihood of release and exposure and how they compare with alternatives. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/552185/original/file-20231004-21-o7term.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="people walk past colorful multi-screen display at a trade show" src="https://images.theconversation.com/files/552185/original/file-20231004-21-o7term.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/552185/original/file-20231004-21-o7term.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=417&fit=crop&dpr=1 600w, https://images.theconversation.com/files/552185/original/file-20231004-21-o7term.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=417&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/552185/original/file-20231004-21-o7term.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=417&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/552185/original/file-20231004-21-o7term.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=524&fit=crop&dpr=1 754w, https://images.theconversation.com/files/552185/original/file-20231004-21-o7term.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=524&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/552185/original/file-20231004-21-o7term.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=524&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Quantum dots are now a normal part of many consumer items, including televisions.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/trade-visitors-walk-past-televisions-with-quantum-dots-news-photo/1040134228">Soeren Stache/picture alliance via Getty Images</a></span>
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<p>Since its earlier days, quantum dot technology has evolved in safety and usefulness and has found its way into an increasing number of products, from <a href="https://www.wired.com/2015/01/primer-quantum-dot/">displays</a> and <a href="https://doi.org/10.1021/acs.chemrev.2c00695">lighting</a>, to <a href="https://doi.org/10.1016/B978-0-323-88431-0.00025-9">sensors</a>, <a href="https://doi.org/10.2147/IJN.S357980">biomedical applications</a> and more. In the process, some of their novelty has perhaps worn off. It can be hard to remember just how much of a quantum leap the technology is that’s being used to promote the <a href="https://www.cnet.com/tech/home-entertainment/this-top-secret-prototype-display-will-blow-your-mind/">latest generation of flashy TVs</a>, for instance.</p>
<p>And yet, quantum dots are a pivotal part of a technology transition that’s revolutionizing how people work with atoms and molecules.</p>
<h2>‘Base coding’ on an atomic level</h2>
<p>In my book “<a href="https://andrewmaynard.net/films-from-the-future/">Films from the Future: the Technology and Morality of Sci-Fi Movies</a>,” I write about the concept of “<a href="https://andrewmaynard.substack.com/p/how-our-mastery-of-biological-physical-and-cyber-base-code-is-transforming-how-we-think-about-b2eae9d589d0">base coding</a>.” The idea is simple: If people can manipulate the most basic code that defines the world we live in, we can begin to redesign and reengineer it. </p>
<p>This concept is intuitive when it comes to computing, where programmers use the “base code” of 1’s and 0’s, albeit through higher level languages. It also makes sense in biology, where scientists are becoming increasingly adept at reading and writing the base code of DNA and RNA – in this case, using the chemical bases adenine, guanine, cytosine and thymine as their coding language. </p>
<p>This ability to work with base codes also extends to the material world. Here, the code is made up of atoms and molecules and how they are arranged in ways that lead to novel properties.</p>
<p>Bawendi, Brus and Ekimov’s work on quantum dots is a perfect example of this form of material-world base coding. By precisely forming small clusters of particular atoms into spherical “dots,” they were able to tap into novel quantum properties that would otherwise be inaccessible. Through their work they demonstrated the transformative power that comes through coding with atoms.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/552183/original/file-20231004-25-wr0i0a.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="alt" src="https://images.theconversation.com/files/552183/original/file-20231004-25-wr0i0a.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/552183/original/file-20231004-25-wr0i0a.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=514&fit=crop&dpr=1 600w, https://images.theconversation.com/files/552183/original/file-20231004-25-wr0i0a.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=514&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/552183/original/file-20231004-25-wr0i0a.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=514&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/552183/original/file-20231004-25-wr0i0a.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=646&fit=crop&dpr=1 754w, https://images.theconversation.com/files/552183/original/file-20231004-25-wr0i0a.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=646&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/552183/original/file-20231004-25-wr0i0a.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=646&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">An example of ‘base coding’ using atoms to create a material with novel properties is a single molecule ‘nanocar’ crafted by chemists that can be controlled as it ‘drives’ over a surface.</span>
<span class="attribution"><a class="source" href="https://news.rice.edu/news/2020/rice-rolls-out-next-gen-nanocars">Alexis van Venrooy/Rice University</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>They paved the way for increasingly sophisticated nanoscale base coding that is now leading to products and applications that would not be possible without it. And they were part of the inspiration for a <a href="https://www.nature.com/articles/d41586-022-02146-4">nanotechnology revolution</a> that is continuing to this day. Reengineering the material world in these novel ways far transcends what can be achieved through more conventional technologies.</p>
<p>This possibility was captured in a 1999 U.S. National Science and Technology Council report with the title <a href="https://trid.trb.org/view/636880">Nanotechnology: Shaping the World Atom by Atom</a>. While it doesn’t explicitly mention quantum dots – an omission that I’m sure the authors are now kicking themselves over – it did capture just how transformative the ability to engineer materials at the atomic scale could be.</p>
<p>This atomic-level shaping of the world is exactly what Bawendi, Brus and Ekimov aspired to through their groundbreaking work. They were some of the first materials “base coders” as they used atomically precise engineering to harness the quantum physics of small particles – and the Nobel committee’s recognition of the significance of this is well deserved.</p><img src="https://counter.theconversation.com/content/215015/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Andrew Maynard has previously received funding for nanotechnology-based work from the National Institutes of Health, the National Science Foundation, and the Pew Charitable Trusts</span></em></p>Quantum dots are a prime example of the way nanotechnology engineers materials at an atomic scale.Andrew Maynard, Professor of Advanced Technology Transitions, Arizona State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2141532023-09-26T20:06:41Z2023-09-26T20:06:41ZNew study shows we can create value from food waste by turning it into a highly desirable material – nanocellulose<p>Food waste is a global problem with approximately <a href="https://www.theworldcounts.com/challenges/people-and-poverty/hunger-and-obesity/food-waste-statistics">1.3 billion tonnes</a> of food wasted each year throughout the food lifecycle – from the farm to food manufacturers and households.</p>
<p>Across the food supply chain, Australians waste around <a href="https://www.dcceew.gov.au/environment/protection/waste/food-waste">7.6 million tonnes</a> of food each year. This costs our economy <a href="https://www.dcceew.gov.au/environment/protection/waste/food-waste">approximately A$36.6 billion</a> annually. </p>
<p>In a recent study published in <a href="https://doi.org/10.1016/j.biteb.2023.101629">Bioresource Technology Reports</a>, we have found a way to use food waste for making a versatile material known as nanocellulose. In particular, we used acid whey – a significant dairy production waste material that it usually difficult to dispose of.</p>
<h2>Mixing waste with bacteria</h2>
<p>Nanocellulose is a biopolymer, which means it’s a naturally produced long chain of sugars. It has remarkable properties – bacterial nanocellulose is strong, chemically stable and biocompatible, meaning it’s not harmful to human cells. This makes it a highly marketable product with applications in packaging, wound treatments, drug delivery or food production. </p>
<p>The traditional approach for making nanocellulose can be expensive, uses large amounts of energy and takes a long time. Some types of nanocellulose production also use a chemical process that produces unwanted waste byproducts. </p>
<p>By contrast, our new approach uses just food waste and a symbiotic culture of bacteria and yeasts (SCOBY) – something you may be familiar with as a kombucha starter. Our process is low cost, consumes little energy and produces no waste.</p>
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Read more:
<a href="https://theconversation.com/what-is-kombucha-and-how-do-the-health-claims-stack-up-87180">What is kombucha and how do the health claims stack up?</a>
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<p>We used a runny waste liquid known as acid whey from a local cheese manufacturer in Melbourne, Australia. In the dairy industry, acid whey is often disposed of as wastewater in large amounts (more than <a href="https://www.unimelb.edu.au/newsroom/news/2016/september/the-whey-to-go">100 million litres of acid whey</a> are produced annually in Australia alone), despite it being rich in carbohydrates and proteins. This is because it’s hard to process into other products due to a high lactic acid content. </p>
<p>We heat-treated the liquid and supplemented it with sugar and yeast extract before adding the key ingredient, SCOBY (obtained commercially from a Melbourne-based kombucha company).</p>
<p>Over four days as our mixture fermented, the bacteria worked to create nanocellulose material which floated to the top. Lovers of home-brewed kombucha may actually be familiar with the raw nanocellulose material – it forms as a floating off-white structure called a pellicle. Some people already use this kombucha by-product as <a href="https://www.instructables.com/Kombucha-Wallet/">vegan leather</a>.) A similar pellicle formed on our acid whey mixture. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/550158/original/file-20230926-23-ylbqjc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A hand holding a gelatinous cream coloured substance shaped like a circle" src="https://images.theconversation.com/files/550158/original/file-20230926-23-ylbqjc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/550158/original/file-20230926-23-ylbqjc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=503&fit=crop&dpr=1 600w, https://images.theconversation.com/files/550158/original/file-20230926-23-ylbqjc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=503&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/550158/original/file-20230926-23-ylbqjc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=503&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/550158/original/file-20230926-23-ylbqjc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=633&fit=crop&dpr=1 754w, https://images.theconversation.com/files/550158/original/file-20230926-23-ylbqjc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=633&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/550158/original/file-20230926-23-ylbqjc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=633&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The pellicle - the white stuff that grows on top of a homemade kombucha brew - is actually a type of nanocellulose.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
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<h2>A growing market</h2>
<p>Demand for nanocellulose is growing worldwide. The global market was valued at <a href="https://www.marketsandmarkets.com/Market-Reports/nano-cellulose-market-56392090.html">US$0.4 billion in 2022</a> (A$0.6bn) and is expected to grow to US$2 billion by 2030 (A$3.1bn). Bacterial nanocellulose produced from food waste can help to satisfy this demand.</p>
<p>This growth is in part due to how we can use nanocellulose instead of petroleum-based and other non-renewable materials in things like packaging. Among its desirable properties, nanocellulose is also fully biodegradable.</p>
<p>Manufacturers around the globe are seeking sustainable sources of raw material for producing composite materials with various properties. Nanocellulose is easily customised in this way. For example, infusing nanocellulose with a compound called glycerol enhances its flexibility and makes it more pliant. As a food-safe material, we are now investigating nanocellulose as “smart” packaging by <a href="https://www.abc.net.au/news/rural/2023-08-14/food-waste-turned-into-packaging-to-save-produce-from-landfill/102718618">infusing nanocellulose with indicators</a> that signal when food is no longer safe to eat.</p>
<p>Additionally, using a single source of food waste (such as acid whey in our example) means we can produce highly pure nanocellulose – ideal for biomedical applications, such as wound dressings, pharmaceutical compounding and cell cultures.</p>
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<a href="https://images.theconversation.com/files/550159/original/file-20230926-25-yhq86c.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A white filmy material draped across a person's forearm" src="https://images.theconversation.com/files/550159/original/file-20230926-25-yhq86c.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/550159/original/file-20230926-25-yhq86c.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/550159/original/file-20230926-25-yhq86c.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/550159/original/file-20230926-25-yhq86c.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/550159/original/file-20230926-25-yhq86c.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/550159/original/file-20230926-25-yhq86c.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/550159/original/file-20230926-25-yhq86c.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">An example of nanocellulose material that could be used for wound dressing.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
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</figure>
<h2>Efficient circular economy</h2>
<p>A circular economy attempts to minimise waste and extend the lifecycle of products for as long as possible. Our study demonstrates an efficient circular economy approach for upcycling a dairy industry waste product into sustainable nanocellulose.</p>
<p>Additionally, the sediment residue we produced has a high nutrient value and potentially has commercial value as a fertiliser or animal feed, while the liquid culture can be reused for the next batch. </p>
<p>Our study was limited to a single source of food waste within a laboratory environment. A future challenge will be taking this approach out of the lab and scaling it up for commercial use. This will involve a series of steps throughout the value chain from waste collection and transport through to commercial production.</p>
<p>We also hope to explore alternative mediums such as mixed food waste. More research also needs to be done on how nanocellulose can be most effectively customised for various applications, such as different types of food packaging.</p>
<p>Overall, our proof-of-concept study demonstrates potential for producing nanocellulose in a sustainable, environmentally sound manner – from food waste to significant value.</p>
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<em>
<strong>
Read more:
<a href="https://theconversation.com/explainer-what-is-a-circular-economy-29666">Explainer: What is a circular economy? </a>
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<img src="https://counter.theconversation.com/content/214153/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>We can’t entirely eliminate food waste – but we can find cheap ways to turn it into something useful.Alan Labas, Lecturer in Management, Federation University AustraliaBenjamin Matthew Long, Senior Lecturer, Chemistry, Federation University AustraliaDylan Liu, Lecturer in Food Science and Sustainability, Federation University AustraliaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2130252023-09-07T18:00:25Z2023-09-07T18:00:25ZSeparating molecules is a highly energy-intensive but essential part of drug development, desalination and other industrial processes – improving membranes can help<figure><img src="https://images.theconversation.com/files/546739/original/file-20230906-15-1tywxl.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C2121%2C1412&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Molecules are often separated by their size, shape or other properties.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/abstract-spheres-flowing-through-a-circle-shaped-royalty-free-image/1336236614">twomeows/Moment via Getty Images</a></span></figcaption></figure><p>Separating molecules is critical to producing many essential products. For example, in <a href="https://www.britannica.com/technology/petroleum-refining">petroleum refining</a>, the hydrocarbons – chemical compounds composed of hydrogens and carbons – in crude oil are separated into gasoline, diesel and lubricants by sorting them based on their molecular size, shape and weight. In the <a href="https://doi.org/10.1038/s41586-022-05032-1">pharmaceutical industry</a>, the active ingredients in medications are purified by separating drug molecules from the enzymes, solutions and other components used to make them. </p>
<p>These separation processes take a substantial amount of energy, accounting for <a href="https://doi.org/10.1038/532435a">roughly half of U.S. industrial energy use</a>. Traditionally, molecular separations have relied on methods that require intensive heating and cooling that make them very energy inefficient. </p>
<p>We are <a href="https://scholar.google.com/citations?user=wiZJ2yAAAAAJ&hl=en">chemical and</a> <a href="https://scholar.google.com/citations?user=ryUNRywAAAAJ&hl=en">biological engineers</a>. In our newly published research, we designed a new type of <a href="https://www.science.org/doi/10.1126/science.adh2404">membrane with nanopores</a> that can quickly and precisely separate a diverse range of molecules under harsh industrial conditions.</p>
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<figcaption><span class="caption">Membranes are one method to desalinate water.</span></figcaption>
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<h2>Membrane technology</h2>
<p><a href="https://en.wikipedia.org/wiki/Membrane">Membranes are physical barriers</a> that can separate molecules in a mixture like a sieve based on their size or affinity – such as charge or polarity – to the membrane material. For example, <a href="https://www.genome.gov/genetics-glossary/Cell-Membrane">your cells</a> are surrounded by a membrane that transports nutrients into it and transports toxins out of it. <a href="https://en.wikipedia.org/wiki/Membrane_technology">Membrane technology</a> include synthetic barriers that can separate molecules in industrially important mixtures at a lower energy cost than traditional methods. </p>
<p>Currently available membranes, including those used in large-scale <a href="https://doi.org/10.1126/science.abb8518">seawater desalination</a>, suffer from instability at high temperatures and when exposed to <a href="https://www.cdc.gov/niosh/topics/organsolv/default.html#">organic solvents</a> – carbon-based chemicals that dissolve other substances. This has limited the use of membranes in many industrial separations. </p>
<p><a href="https://doi.org/10.1126/science.aax3103">Inorganic materials</a> are more stable and better able to survive industrial conditions. Previous studies have focused on making inorganic membranes that are ultrathin in order to allow specific molecules to pass through. But thinness increases the likelihood of creating defects and pinholes in the membrane, and would be difficult to make on an industrial scale. </p>
<h2>Improving membrane separation</h2>
<p>We developed a technique to make a new inorganic material called <a href="https://www.science.org/doi/10.1126/science.adh2404">carbon-doped metal oxide</a> that can separate organic molecules smaller than one nanometer (for scale, a <a href="https://www.nano.gov/nanotech-101/what/nano-size">gold atom</a> is a third of a nanometer in diameter).</p>
<p>Taking inspiration from an existing technology that manufacturers use to make semiconductors, called <a href="https://doi.org/10.3762/bjnano.5.123">molecular layer deposition</a>, we worked with two low-cost reactants from that process and generated thin films. These films contain nanopores that can be precisely tuned to control the separation of molecules ranging from 0.6 to 1.2 nanometers in diameter.</p>
<p>One of the key features of our membrane is that it can <a href="https://www.science.org/doi/10.1126/science.adh2404">withstand harsh conditions</a>. These membranes are stable up to 284 degrees Fahrenheit (140 degrees Celsius) and pressures up to 30 atmospheres (around 441 pounds per square inch) in the presence of organic solvents. This stability is critical, as many industrial separation processes can save tremendous amounts of energy when carried out under high temperatures. </p>
<p>As a demonstration, we used our membrane in the molecule separation step during the manufacture of the pesticide boscalid. By tailoring the pore sizes of our membranes to match the sizes of the molecules in the mixture, we were able to <a href="https://www.science.org/doi/10.1126/science.adh2404">separate each individual component</a> of reactant, product and catalyst. Because of the stability of our membrane, we were able to carry out the whole process at 194 F (90 C), the temperature at which the reaction takes place, eliminating the need to reduce the temperature during the separation process. This can significantly reduce energy consumption and, in turn, reduce the carbon footprint of the industrial process. </p>
<p>We believe our membrane can be used in many similar industrial processes, including those involving harsh conditions where traditional membranes would fail, and are confident that it can be quickly scaled up. This can open the door for researchers and manufacturers to use membranes in previously unexplored applications.</p><img src="https://counter.theconversation.com/content/213025/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Miao Yu receives funding from National Science Foundation.</span></em></p><p class="fine-print"><em><span>Bratin Sengupta does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Around half of US industrial energy use goes toward separating molecules in industrial processes. Developing materials that can withstand harsh industrial conditions can help increase efficiency.Bratin Sengupta, Ph.D. Candidate in Chemical and Biological Engineering, University at BuffaloMiao Yu, Professor of Chemical and Biological Engineering, University at BuffaloLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2117332023-08-21T01:43:27Z2023-08-21T01:43:27ZHopes fade for ‘room temperature superconductor’ LK-99, but quantum zero-resistance research continues<figure><img src="https://images.theconversation.com/files/543584/original/file-20230821-153697-h30w0m.jpg?ixlib=rb-1.1.0&rect=0%2C8%2C1917%2C1141&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://sciencecast.org/casts/suc384jly50n">Hyun-Tak Kim</a></span></figcaption></figure><p>The past few weeks have seen a huge surge of interest among scientists and the public in a material called <a href="https://en.wikipedia.org/wiki/LK-99">LK-99</a> after it was claimed to be a superconductor at room temperature and ambient pressure.</p>
<p>LK-99 garnered attention after South Korean researchers posted <a href="https://arxiv.org/abs/2307.12008">two</a> <a href="https://arxiv.org/abs/2307.12037">papers</a> about it on arXiv, a non-peer-reviewed repository for scientific reports, on July 22. The researchers reported possible indicators of superconductivity in LK-99, including unexpectedly low electrical resistance and partial levitation in a magnetic field. </p>
<p>The potential discovery drew enthusiasm on social media and was widely reported in <a href="https://www.nytimes.com/2023/08/03/science/lk-99-superconductor-ambient.html">traditional</a> media too. As a physicist working on quantum phenomena in materials, I was gratified to see the interest in superconductivity, and I shared in the excitement about the report. But I also approached the results with scepticism, especially since many previous reports of room-temperature superconductivity have failed to be reproduced. </p>
<p>Now, after follow-up experiments by scientists around the world, <a href="https://www.nature.com/articles/d41586-023-02585-7">it seems LK-99 is not so special after all</a>. However, while this particular avenue of research may be a dead end, the dream of a room-temperature superconductor is still very much alive. </p>
<h2>What is a superconductor, and why are they useful?</h2>
<p>You’re probably familiar with ordinary conductors, like metals, in which electrons can move fairly easily through the “crystal lattice” of atoms that makes up the material. This means an electric current can flow – but the electrons are jostled around a bit as they move, so they lose energy as they travel. (This jostling is called electrical resistance.)</p>
<p>In a superconductor, there is zero resistance and an electrical current can flow perfectly smoothly without losing any energy. Many metals become superconductors at very low temperatures.</p>
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<p>Superconductivity occurs when the electrons slightly distort the crystal lattice of the metal in a way that makes them team up into “Cooper pairs”. These pairs of electrons then “condense” into a superfluid, a state of matter that can flow without friction.</p>
<p>Superconductors are very useful. They can be used to create extremely powerful electromagnets, such as those in MRI scanners, particle accelerators, fusion reactors and maglev trains. </p>
<p>Current superconductors work only at ultra-cold temperatures, so they require expensive refrigeration. A material that superconducts at everyday temperature and pressure could be used much more widely.</p>
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<p>Currently, the highest superconducting temperatures at ambient pressure are around –138°C (135 Kelvin), found in “cuprate” superconductors, a family of copper-containing compounds discovered unexpectedly in 1986. Electron pairing in the cuprates appears to involve a different mechanism than interaction with the lattice. </p>
<p>However, while our understanding of such exotic superconductors has improved, we still can’t yet predict with any certainty new materials which could superconduct at even higher temperature. Still, there is no reason to think this can’t be achieved. Moreover, many if not most superconducting materials are discovered serendipitously – so a claimed discovery of an unexpected room-temperature superconductor can’t be dismissed out of hand.</p>
<h2>So what about LK-99?</h2>
<p>LK-99 is a compound containing oxygen, phosphorus, lead and copper. Little was known about the material when the papers claiming superconductivity emerged. For example, it wasn’t even known whether it should conduct electricity at all. </p>
<p>The report of superconductivity at ambient conditions sparked a crash effort from researchers around the world to understand the material and reproduce the results. While it is still early days, and neither the initial report nor <a href="https://arxiv.org/search/?query=lk-99&searchtype=all&source=header">the follow-ups</a> have been peer-reviewed, a picture has started to emerge that the LK-99 compound described by the authors is <a href="https://arxiv.org/abs/2308.03544">not</a> a <a href="https://arxiv.org/abs/2308.03823">superconductor</a>, and <a href="https://arxiv.org/abs/2308.05143">not even</a> a <a href="https://arxiv.org/abs/2308.06256">metal</a>. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/viral-room-temperature-superconductor-claims-spark-excitement-and-skepticism-210700">Viral room-temperature superconductor claims spark excitement – and skepticism</a>
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</em>
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<p>So if it’s not a superconductor, why did the original researchers think it was? One study has <a href="https://arxiv.org/abs/2308.04353">pointed out</a> that an impurity in the initial LK-99 samples, cuprous sulfide, could explain some of what they saw.</p>
<p>Cuprous sulfide experiences a sudden, large change in resistance at a temperature of around 127°C (400K). The first researchers saw this drop in resistance and attributed it to superconductivity in LK-99, but it is more likely explained by very low (not zero) resistance in the cuprous sulfide impurity.</p>
<p>The partial levitation of LK-99, which might have indicated a property of superconductors called “<a href="https://www.fleet.org.au/blog/supercool-superconducting-mobius-track-helps-communicate-fleet-science/">magnetic flux pinning</a>”, seems to be caused by ferromagnetism, a familiar effect that occurs in iron and many other materials.</p>
<p>So while nobody has proven the LK-99 samples studied in the original reports <em>don’t</em> superconduct, the balance of evidence right now is strongly in favour of other explanations. Most scientists studying superconductivity don’t see much reason to continue looking at LK-99.</p>
<h2>Excitons and beyond</h2>
<p>What’s next for superconductivity research? Well, we can cross LK-99 off the list of materials to study, but the search goes on.</p>
<p>In fact, there has been a lot of progress in the past few years towards creating zero resistance under ordinary conditions. </p>
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<em>
<strong>
Read more:
<a href="https://theconversation.com/room-temperature-superconductors-could-revolutionize-electronics-an-electrical-engineer-explains-the-materials-potential-201849">Room-temperature superconductors could revolutionize electronics – an electrical engineer explains the materials' potential</a>
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<p>Making electrons pair together is the key to superconductivity, but this is hard to do as they naturally repel each other. However, it’s possible to make an electron pair up with a “hole” in a material – a gap where an electron should be. </p>
<p>These electron–hole pairs are called excitons, and they can be combined with light to form a <a href="https://doi.org/10.1038/s41467-022-34987-y">frictionless superfluid</a> at room temperature. This superfluid doesn’t carry an electrical current (because the charges of the electron and the hole cancel out), but <a href="https://doi.org/10.1038/nature03081">separating the electron and hole</a> might allow <a href="https://doi.org/10.1038/nphys1055">supercurrents without resistance</a>.</p>
<h2>Topological insulators</h2>
<p>An alternate route to zero resistance at room temperature has been found in so-called <a href="https://www.youtube.com/watch?v=jQ_ihxXcqpg">topological insulators</a>. These are materials that only allow electrons to move along their edges or surfaces, in some cases with no resistance.</p>
<p>Graphene, a material made of sheets of carbon only a single atom thick, can be <a href="https://doi.org/10.1126/science.1137201">turned into a topological insulator</a> in a strong magnetic field. But the required magnetic field is so extreme it can only be realised in a few laboratories in the world.</p>
<figure class="align-center ">
<img alt="A photo shows a scientist manipulating a levitating piece of metal surrounding by vapour from liquid nitrogen." src="https://images.theconversation.com/files/543374/original/file-20230818-21-mewpzs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/543374/original/file-20230818-21-mewpzs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/543374/original/file-20230818-21-mewpzs.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/543374/original/file-20230818-21-mewpzs.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/543374/original/file-20230818-21-mewpzs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/543374/original/file-20230818-21-mewpzs.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/543374/original/file-20230818-21-mewpzs.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">Typical superconductors only function at extremely low temperatures.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/female-student-demonstrates-quantum-magnetic-levitation-1371737648">Michelmond / Shutterstock</a></span>
</figcaption>
</figure>
<p>There are also other types of topological insulators that work without an externally applied magnetic field. Current versions of these materials show zero resistance only at very low temperatures, but there appears to be no reason they couldn’t work at room temperature. </p>
<p>Unfortunately superfluid excitons and topological insulators can only carry a limited amount of current, and are probably not useful for creating powerful magnets. But they could still be useful for transmitting the tiny electrical signals used in computer chips, and <a href="http://fleet.org.au">my colleagues and I</a> are using them to create low-power electronic and computing technologies.</p><img src="https://counter.theconversation.com/content/211733/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Michael Fuhrer receives funding from the Australian Research Council. </span></em></p>A potential new supermaterial isn’t so super after all, but the dream of a room-temperature superconductor is still very much alive.Michael Fuhrer, Professor of Physics, Monash UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2107002023-07-31T05:49:54Z2023-07-31T05:49:54ZViral room-temperature superconductor claims spark excitement – and skepticism<figure><img src="https://images.theconversation.com/files/540083/original/file-20230731-25689-3y1jr1.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C2787%2C1671&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://sciencecast.org/casts/suc384jly50n">Hyun-Tak Kim</a></span></figcaption></figure><p>Last week, a group of South Korean physicists made a startling claim. In <a href="https://arxiv.org/abs/2307.12037">two</a> <a href="https://arxiv.org/abs/2307.12008">papers</a> uploaded to the arXiv preprint server, they say they have created a material that “opens a new era for humankind”.</p>
<p>LK-99, a lead-based compound, is purportedly a room-temperature, ambient-pressure superconductor. Such a material, which conducts electricity without any resistance under normal conditions, could have huge implications for energy generation and transmission, transport, computing and other areas of technology.</p>
<p>The papers have sparked wild enthusiasm online, and several efforts to <a href="https://www.science.org/content/article/spectacular-superconductor-claim-making-news-here-s-why-experts-are-doubtful">replicate the work</a>. At the same time, there are <a href="https://www.asiafinancial.com/korea-superconductor-papers-published-without-consent-yonhap">reports</a> of disputes among the Korean researchers over whether the research should have been released at all.</p>
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<h2>Why superconductors are so super</h2>
<p>When an electric current flows through an ordinary conductor like a copper wire, the electrons bump into atoms as they jostle along. As a result, the electrons lose some energy and the wire heats up.</p>
<p>In a superconductor, electrons move without any resistance. Superconducting wires can transmit electricity without losing energy, and superconducting magnets are powerful enough to levitate trains and contain the fierce plasmas in fusion reactors.</p>
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Read more:
<a href="https://theconversation.com/room-temperature-superconductors-could-revolutionize-electronics-an-electrical-engineer-explains-the-materials-potential-201849">Room-temperature superconductors could revolutionize electronics – an electrical engineer explains the materials' potential</a>
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<p>However, all known superconductors require very low temperatures (typically lower than –100 °C) or extremely high pressures (more than 100,000 times ordinary atmospheric pressure). These restrictions make superconductors expensive and impractical for many applications.</p>
<p>Several teams of researchers have claimed to detect room-temperature superconductivity in various substances in the past, but none of the claims have withstood scrutiny. As recently as last week, a superconductivity paper by American physicist Ranga Dias was <a href="https://www.nature.com/articles/d41586-023-02401-2">retracted</a> amid suspicions of data fabrication. </p>
<p>So while a room-temperature superconductor would be an amazing discovery, we should meet the new claims with some skepticism.</p>
<h2>Bold claims</h2>
<p>The South Korean researchers say LK-99 can be made in a baking process that combines the minerals lanarkite (Pb₂SO₅) and copper phosphide (Cu₃P). They say the resulting material shows two key signs of superconductivity at normal air pressure and at temperatures up to 127 °C: zero resistance and magnetic levitation.</p>
<p>They propose a plausible theory of how LK-99 might display room-temperature superconductivity, but have not provided definite experimental evidence. The data presented in the papers appear inconclusive.</p>
<p>One of the signatures of a superconductor is the Meissner effect, which causes it to levitate when placed above a magnet. </p>
<p>In a <a href="https://sciencecast.org/casts/suc384jly50n">video demonstration</a>, the researchers position a piece of LK-99 over a magnet. One edge of the flat disk of LK-99 rises, but the other edge appears to maintain contact with the magnet. </p>
<p>We would expect a superconductor to display full levitation and also “quantum locking” which keeps it in a fixed position relative to the magnet. In a charitable interpretation, the behaviour we see in the video may be due to imperfections in the sample, meaning only part of the sample becomes superconductive.</p>
<p>So it is too early to say we have been presented with compelling evidence for room-temperature superconductivity.</p>
<h2>What’s next</h2>
<p>At present, all we know about LK-99 comes from the two arXiv papers, which have not been peer-reviewed. Both papers present similar measurements, though the presentation is unconventional. However, there are some differences in the content, and also in authorship, which does not inspire confidence.</p>
<p>So what happens now? The processes of science swing into action. </p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1684256538142154752"}"></div></p>
<p>Experts will closely review the papers. Researchers at other laboratories will attempt to reproduce the experiments described in the papers, and see whether they end up with a room-temperature superconductor. </p>
<p>These crucial steps are necessary to establish the validity and reliability of the LK-99 claims. If the claims are validated and confirmed, it could mark one of the most groundbreaking advancements in physics and materials engineering in the past few decades. </p>
<p>However, until the research undergoes rigorous review and testing, we should approach the claims with caution. We will all be awaiting the outcome of the verification process with great interest.</p><img src="https://counter.theconversation.com/content/210700/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Mahboobeh Shahbazi does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Room-temperature superconductors could transform technology – but the latest, much-hyped claims should be approached with caution.Mahboobeh Shahbazi, Senior Research Fellow, Materials Science, Queensland University of TechnologyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2046672023-06-13T12:30:44Z2023-06-13T12:30:44ZGlass: Neither a solid nor a liquid, this common yet complicated material is still surprising scientists<figure><img src="https://images.theconversation.com/files/531456/original/file-20230612-270005-nzhau6.jpg?ixlib=rb-1.1.0&rect=112%2C1003%2C3626%2C3654&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Most glass is made by melting down soda ash, limestone and quartz sand.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/foundry-royalty-free-image/503698461?phrase=pouring+molten+glass&adppopup=true">gezgin01/iSock via Getty Images</a></span></figcaption></figure><p>Glass is a material of many faces: It is both ancient and modern, strong yet delicate, and able to adopt almost any shape or color. These properties of glass are why people use it to make everything from <a href="https://www.glassnmirrors.com/why-are-phone-screens-made-of-glass/">smartphone screens</a> and <a href="https://www.popsci.com/story/technology/corning-fiber-optic-factory-glass/">fiber-optic cables</a> to <a href="https://www.bbc.com/news/business-55808640">vials that hold vaccines</a>. </p>
<p>Humankind has been <a href="http://doi.org/10.2109/jcersj2.22066">using glass in some fashion for millennia</a>, and researchers are still finding new uses for it today. It’s not uncommon to hear the oft-repeated factoid that glass is actually a liquid, not a solid. But the reality is much more interesting – glass does not fit neatly into either of those categories and is in many ways a state of matter all its own. As two <a href="https://scholar.google.com/citations?user=X-wzzwUAAAAJ&hl=en&oi=ao">materials</a> <a href="https://scholar.google.com/citations?user=RWYt-7EAAAAJ&hl=en&oi=ao">scientists</a> who study glass, we are constantly trying to improve our understanding of this unique material and discover new ways to use glass in the future.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/531439/original/file-20230612-63747-fgvswn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A large block of shiny black stone." src="https://images.theconversation.com/files/531439/original/file-20230612-63747-fgvswn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/531439/original/file-20230612-63747-fgvswn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/531439/original/file-20230612-63747-fgvswn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/531439/original/file-20230612-63747-fgvswn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/531439/original/file-20230612-63747-fgvswn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/531439/original/file-20230612-63747-fgvswn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/531439/original/file-20230612-63747-fgvswn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Obsidian is a naturally formed glass.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/obsidian-lave-field-landmannalaugar-iceland-royalty-free-image/522693482?phrase=obsidian&adppopup=true">Layne Kennedy/Corbis Documentary via Getty Images</a></span>
</figcaption>
</figure>
<h2>What is glass?</h2>
<p>The best way to understand glass is to understand how it is made. </p>
<p>The first step to make glass requires heating up a mixture of minerals – often soda ash, limestone and quartz sand – until they melt into a liquid at around 2,700 degrees Fahrenheit (1,480 Celsius). In this state, the minerals are freely flowing in the liquid and move in a disordered way. If this liquid cools down fast enough, instead of solidifying into an organized, crystalline structure like most solids, the mixture solidifies while maintaining the disordered structure. It is the atomically disordered structure that defines glass.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/531434/original/file-20230612-261256-xewjit.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Three graphics showing atomic structure ranging from ordered to chaotic." src="https://images.theconversation.com/files/531434/original/file-20230612-261256-xewjit.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/531434/original/file-20230612-261256-xewjit.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=221&fit=crop&dpr=1 600w, https://images.theconversation.com/files/531434/original/file-20230612-261256-xewjit.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=221&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/531434/original/file-20230612-261256-xewjit.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=221&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/531434/original/file-20230612-261256-xewjit.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=277&fit=crop&dpr=1 754w, https://images.theconversation.com/files/531434/original/file-20230612-261256-xewjit.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=277&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/531434/original/file-20230612-261256-xewjit.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=277&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">When molten glass cools, it freezes the disordered, amorphous structure it had as a liquid.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Crystalline_polycrystalline_amorphous2.svg#/media/File:Crystalline_polycrystalline_amorphous2.svg">Cdang/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>On short timescales, glass behaves much like a solid. But the liquidlike structure of glass means that over a long enough period of time, glass undergoes a process called <a href="https://www.sciencedirect.com/book/9780128162255/fundamentals-of-inorganic-glasses">relaxation</a>. Relaxation is a continuous but extremely slow process where the atoms in a piece of glass will slowly rearrange themselves into a more stable structure. Over 1 billion years, a typical piece of glass will <a href="https://doi.org/10.1111/jace.15092">change shape by less than 1 nanometer</a> – about 1/70,000 the diameter of human hair. Due to the slow rate of change, the myth that old windows are thicker at the bottom due to centuries of gravity pulling on the slowly flowing glass is not true.</p>
<p>Colloquially, the word glass often refers to a <a href="https://www.britannica.com/technology/glass">hard, brittle, transparent substance</a> made of fused sand, soda and lime. Yet there are many types of glass that are not transparent, and glass can be made from any combination of elements as long as the liquid mixture can be cooled fast enough to avoid crystallization. </p>
<h2>From the Stone Age to today</h2>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/531437/original/file-20230612-262080-brvmoz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A decorative, yellowish glass cup." src="https://images.theconversation.com/files/531437/original/file-20230612-262080-brvmoz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/531437/original/file-20230612-262080-brvmoz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=770&fit=crop&dpr=1 600w, https://images.theconversation.com/files/531437/original/file-20230612-262080-brvmoz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=770&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/531437/original/file-20230612-262080-brvmoz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=770&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/531437/original/file-20230612-262080-brvmoz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=967&fit=crop&dpr=1 754w, https://images.theconversation.com/files/531437/original/file-20230612-262080-brvmoz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=967&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/531437/original/file-20230612-262080-brvmoz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=967&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Humans have been creating tools with glass for thousands of years, like this Roman cup from the fourth century.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/File:Roman_diatretglas.jpg#/media/File:Roman_diatretglas.jpg">MatthiasKabel/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Humans have been using glass for more than 4,000 years, with some of the earliest uses being for decorative glass beads and arrowheads. Archaeologists have also discovered evidence of 2,000-year-old glass workshops. One such ancient workshop was uncovered near Haifa in modern Israel and dates back to around 350 C.E. There, archaeologists <a href="https://whatson.cmog.org/exhibitions-galleries/dig-deeper-discovering-ancient-glass-workshop">discovered pieces of raw glass</a>, glass-melting furnaces, utilitarian glass vessels and debris from glass-blowing.</p>
<p>Modern glass manufacturing began in the early 20th century with the development of <a href="https://www.asme.org/about-asme/engineering-history/landmarks/86-owens-ar-bottle-machine">mass production techniques for glass bottles</a> and <a href="https://www.pilkington.com/en/global/knowledge-base/glass-technology/the-float-process/the-float-process">flat glass sheets</a>. Glass became an essential part of the electronics and telecommunications industry in the latter part of the 20th century and <a href="https://www.corning.com/worldwide/en/innovation/culture-of-innovation/corning-celebrates-45-years-on-cutting-edge-with-optical-fiber.html">now forms the backbone for the internet</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/531436/original/file-20230612-119811-nzl2px.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A cable with light coming out of both ends." src="https://images.theconversation.com/files/531436/original/file-20230612-119811-nzl2px.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/531436/original/file-20230612-119811-nzl2px.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=376&fit=crop&dpr=1 600w, https://images.theconversation.com/files/531436/original/file-20230612-119811-nzl2px.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=376&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/531436/original/file-20230612-119811-nzl2px.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=376&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/531436/original/file-20230612-119811-nzl2px.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=472&fit=crop&dpr=1 754w, https://images.theconversation.com/files/531436/original/file-20230612-119811-nzl2px.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=472&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/531436/original/file-20230612-119811-nzl2px.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=472&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Fiber-optic cables use glass to efficiently transmit information.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Fiber_optic_illuminated.jpg#/media/File:Fiber_optic_illuminated.jpg">Hustvedt/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<h2>Glass enabling technologies of tomorrow</h2>
<p>Today, scientists are far beyond simply using glass as the material for a cup or a mirror. At the cutting edge of research into glass is the ability to manipulate its complex atomic structure and relaxation process to achieve certain properties.</p>
<p>Because glass is <a href="https://doi.org/10.1021/acs.chemrev.1c00974">atomically disordered and always changing</a>, any two points on a piece of glass are likely to have slightly different properties – whether it is strength, color, conductivity or something else. Because of these differences, two similar pieces of glass that were made in the same way using the same materials can behave very differently. </p>
<p>To better predict how a piece of glass behaves, our team has been researching how to <a href="https://doi.org/10.1021/acs.chemrev.1c00974">quantify and manipulate</a> the chaotic and ever-changing atomic structure of glass. Recent advances in this field have had direct benefits to existing technologies. </p>
<p>For example, phone screens do not crack as easily as they did in 2014 in part because <a href="https://www.acs.org/education/resources/highschool/chemmatters/past-issues/archive-2014-2015/smartphones.html">new processing techniques</a> decrease the differences in atomic bond strengths to make it harder for cracks to propagate. Similarly, internet speeds have vastly improved over the last 20 years because researchers have figured out ways to make the <a href="https://opg.optica.org/oe/fulltext.cfm?uri=oe-26-18-24190&id=396718">density of glass used for optical fibers more uniform</a> and, therefore, more efficient at transmitting data.</p>
<p>A deeper understanding of how to manipulate the changing, chaotic structure of glass could lead to big advancements in technology in the coming years. Researchers are currently working on a range of projects, including <a href="https://doi.org/10.1016/j.ssi.2006.07.017">glass batteries</a> that could enable faster charging speeds and improved reliability, <a href="https://doi.org/10.3390/ma10111285">fiberglass wind turbines</a> that <a href="https://doi.org/10.1002/we.2552">require less maintenance</a> than existing turbines, and improved <a href="https://cosmosmagazine.com/technology/materials/long-term-data-storage-in-glass/">memory storage devices</a>.</p><img src="https://counter.theconversation.com/content/204667/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Two glass researchers explain how glass is made, the unique properties of glass and how those properties have allowed it to be a useful material to humans for thousands of years.John Mauro, Professor of Materials Science and Engineering, Penn StateKatelyn Kirchner, PhD Candidate in Materials Science, Penn StateLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2018492023-03-28T12:15:34Z2023-03-28T12:15:34ZRoom-temperature superconductors could revolutionize electronics – an electrical engineer explains the materials’ potential<figure><img src="https://images.theconversation.com/files/516813/original/file-20230321-14-inrd39.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C5472%2C3637&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Room-temperature superconductors could make high-speed maglev trains more practical.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/chinas-600-km-h-high-speed-maglev-transportation-system-news-photo/1329831674">Visual China Group via Getty Images</a></span></figcaption></figure><p>Superconductors make highly efficient electronics, but the ultralow temperatures and ultrahigh pressures required to make them work are costly and difficult to implement. Room-temperature superconductors promise to change that.</p>
<p>The recent announcement by researchers at the University of Rochester of a new material that is <a href="https://doi.org/10.1038/s41586-023-05742-0">a superconductor at room temperature</a>, albeit at high pressure, is an exciting development – if proved. If the material or one like it works reliably and can be economically mass-produced, it could revolutionize electronics.</p>
<p>Room-temperature superconducting materials would lead to many new possibilities for practical applications, including ultraefficient electricity grids, ultrafast and energy-efficient computer chips, and ultrapowerful magnets that can be used to levitate trains and control fusion reactors. </p>
<p>A superconductor is a material that conducts direct current <a href="https://theconversation.com/how-do-superconductors-work-a-physicist-explains-what-it-means-to-have-resistance-free-electricity-202308">without encountering any electrical resistance</a>. Resistance is the property of the material that <a href="https://www.physicsclassroom.com/class/circuits/Lesson-3/Resistance">hinders the flow of electricity</a>. Traditional superconductors must be cooled to extremely low temperatures, close to absolute zero. </p>
<p>In recent decades, researchers have developed so-called <a href="https://doi.org/10.1038/s41586-019-1201-8">high-temperature superconductors</a>, which only have to be chilled to minus-10 degrees Fahrenheit (minus-23 Celsius). Though easier to work with than traditional superconductors, high-temperature superconductors still require special thermal equipment. In addition to cold temperatures, these materials require very high pressure, 1.67 million times more than the atmospheric pressure of 14.6 pounds per square inch (1 bar).</p>
<p>As the name suggests, room-temperature superconductors don’t need special equipment to cool them. They do need to be pressurized, but <a href="https://doi.org/10.1038/s41586-023-05742-0">only to a level that’s about 10,000 times more than atmospheric pressure</a>. This pressure can be achieved by using strong metallic casings. </p>
<h2>Where superconductors are used</h2>
<p>Superconductor electronics refers to electronic devices and circuits that use superconducting materials to achieve extremely high levels of performance and energy efficiency that are orders of magnitude better than can be achieved with state-of-the-art semiconductor devices and circuits. </p>
<p>The lack of electrical resistance in superconducting material means that they can support high electrical currents <a href="https://www.elsevier.com/books/superconductivity/poole/978-0-12-409509-0">without any energy loss due to resistance</a>. This efficiency makes superconductors very attractive for power transmission. </p>
<p>Utility provider Commonwealth Edison <a href="https://www.power-grid.com/td/comed-installs-new-high-temp-conductor-cables-to-improve-resilience-boost-cybersecurity/#gref">installed high-temperature superconducting transmission lines</a> and showcased technologies to bring power to Chicago’s north side for a one-year trial period. Compared to conventional copper wire, the upgraded superconducting wire can carry 200 times the electrical current. But the cost of maintaining the low temperatures and high pressures required for today’s superconductors makes even this efficiency gain impractical in most cases.</p>
<p>Because the resistance of a superconductor is zero, if a current is applied to a superconducting loop, the current <a href="https://www.elsevier.com/books/superconductivity/poole/978-0-12-409509-0">will persist forever unless the loop is broken</a>. This phenomenon can be used in various applications to make large permanent magnets. </p>
<p>Today’s magnetic resonance imaging machines <a href="https://doi.org/10.1088%2F0953-2048%2F30%2F1%2F014007">use superconductor magnets</a> to achieve the magnetic field strength of a few teslas, which is needed for accurate imaging. For comparison, the Earth’s magnetic field has a strength, or flux density, of about 50 microteslas. The magnetic field produced by the superconducting magnet in a 1.5 tesla MRI machine is 30,000 times stronger than that produced by the Earth. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/bD2M7P6dTVA?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Superconductors, from theory to applications.</span></figcaption>
</figure>
<p>The scanner uses the superconducting magnet <a href="https://doi.org/10.1088%2F0953-2048%2F30%2F1%2F014007">to generate a magnetic field</a> that aligns hydrogen nuclei in a patient’s body. This process combined with radio waves <a href="https://science.howstuffworks.com/mri.htm">produces images of tissue for an MRI exam</a>. The strength of the magnet directly affects the strength of the MRI signal. A 1.5 tesla MRI machine requires longer scan times to create clear images than a 3.0 tesla machine.</p>
<p>Superconducting materials expel magnetic fields from inside themselves, which makes them <a href="https://indico.cern.ch/event/688896/contributions/2975725/attachments/1646140/2630990/20180504_Applications_of_Superconductivity.pdf">powerful electromagnets</a>. These super-magnets have the potential to <a href="http://www.chm.bris.ac.uk/webprojects2000/igrant/uses.html">levitate trains</a>. Superconducting electromagnets generate 8.3 tesla magnetic fields – more than 100,000 times the Earth’s magnetic field. The electromagnets use a current of 11,080 amperes to produce the field, and a superconducting coil allows the high currents to flow without losing any energy. The <a href="https://scmaglev.jr-central-global.com/">Yamanashi superconducting Maglev train</a> in Japan levitates 4 inches (10 centimeters) above its guideway and travels at speeds up to 311 mph (500 kph).</p>
<p>Superconducting circuits are also a promising technology for quantum computing because they can be <a href="https://doi.org/10.1007/s11432-020-2881-9">used as qubits</a>. Qubits are the basic units of quantum processors, analogous to but much more powerful than transistors in classical computers. Companies such as D-Wave Systems, Google and IBM have built quantum computers that use superconducting qubits. Though superconducting circuits make good qubits, they pose some technological challenges to making quantum computers with large numbers of qubits. A key issue is the need to keep the qubits at very low temperatures, which requires the use of large cryogenic devices known as <a href="https://news.fnal.gov/2022/12/its-colossal-creating-the-worlds-largest-dilution-refrigerator/">dilution refrigerators</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/517795/original/file-20230327-22-3iahqv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="close-up of a computer chip showing colored LEDs scattered among integrated circuits" src="https://images.theconversation.com/files/517795/original/file-20230327-22-3iahqv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/517795/original/file-20230327-22-3iahqv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=460&fit=crop&dpr=1 600w, https://images.theconversation.com/files/517795/original/file-20230327-22-3iahqv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=460&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/517795/original/file-20230327-22-3iahqv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=460&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/517795/original/file-20230327-22-3iahqv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=578&fit=crop&dpr=1 754w, https://images.theconversation.com/files/517795/original/file-20230327-22-3iahqv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=578&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/517795/original/file-20230327-22-3iahqv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=578&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Some quantum computer processors use superconducting circuits.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/jurvetson/39188582795">Steve Jurvetson/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<h2>Promise of room-temperature superconductors</h2>
<p>Room-temperature superconductors would remove many of the challenges associated with the high cost of operating superconductor-based circuits and systems and make it easier to use them in the field. </p>
<p>Room-temperature superconductors would enable ultra high-speed digital interconnects for next-generation computers and low-latency broadband wireless communications. They would also enable high-resolution imaging techniques and emerging sensors for biomedical and security applications, materials and structure analyses, and deep-space radio astrophysics. </p>
<p>Room-temperature superconductors would mean MRIs could become much less expensive to operate because they would not require liquid helium coolant, which is expensive and in short supply. Electrical power grids would be at least 20% more power efficient than today’s grids, resulting in billions of dollars saved per year, according to my estimates. Maglev trains could operate over longer distances at lower costs. Computers would run faster with orders of magnitude lower power consumption. And quantum computers could be built with many more qubits, enabling them to solve problems that are far beyond the reach of today’s most powerful supercomputers.</p>
<p>Whether and how soon this promising future of electronics can be realized depends in part on whether the new room-temperature superconductor material can be verified – and whether it can be economically mass-produced.</p><img src="https://counter.theconversation.com/content/201849/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Massoud Pedram receives funding from the U.S. National Science Foundation (NSF), the Defense Advanced Projects Research Agency (DARPA), and the Intelligence Advanced Research Projects Activity (IARPA). </span></em></p>Superconductors make highly efficient electronics, but the ultralow temperatures and ultrahigh pressures make them costly and difficult to use. Room-temperature superconductors promise to change that.Massoud Pedram, Professor of Electrical and Computer Engineering, University of Southern CaliforniaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2022262023-03-24T12:36:40Z2023-03-24T12:36:40Z3D-printing the brain’s blood vessels with silicone could improve and personalize neurosurgery – new technique shows how<figure><img src="https://images.theconversation.com/files/517257/original/file-20230323-28-w03xh4.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C1864%2C1604&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">3D printers can lay down more than just layers of melted plastic.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/illustration/realistic-3d-paper-cut-human-brain-royalty-free-illustration/1391832014">Dedraw Studio/iStock via Getty Images Plus</a></span></figcaption></figure><p>A new 3D-printing technique using silicone can make accurate models of the blood vessels in your brain, enabling neurosurgeons to train with more realistic simulations before they operate, according to our <a href="https://doi.org/10.1126/science.ade4441">recently published research</a>.</p>
<p>Many neurosurgeons practice each surgery before they get into the operating room <a href="https://doi.org/10.3390%2Fbioengineering7010007">based on models</a> of what they know about the patient’s brain. But the current models neurosurgeons use for training <a href="https://doi.org/10.1093/neuros/nyaa217">don’t mimic real blood vessels well</a>. They provide unrealistic tactile feedback, lack small but important structural details and often exclude entire anatomical components that determine how each procedure will be performed. Realistic and personalized replicas of patient brains during pre-surgery simulations could reduce error in real surgical procedures. </p>
<p>3D printing, however, could make replicas with the soft feel and the structural accuracy surgeons need.</p>
<p>3D printing is typically thought of as a process that involves laying down layer after layer of melted plastic that solidifies as a self-supporting structure is built. Unfortunately, many soft materials do not melt and re-solidify the way the plastic filament that 3D printers typically employ do. Users only get one shot with soft materials like silicone – they have to be printed while in a liquid state and then irreversibly solidified.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/uHbn7wLN_3k?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Researchers are exploring 3D-printing organs using living cells.</span></figcaption>
</figure>
<h2>Shaping liquids in 3D</h2>
<p>How do you make a complex 3D shape out of a liquid without ending up with a puddle or a slumping blob?</p>
<p>Researchers developed a broad approach called <a href="https://doi.org/10.1002/adma.201004625">embedded 3D printing</a> for this purpose. With this technique, the “ink” is deposited inside a bath of a second supporting material designed to flow around the printing nozzle and trap the ink in the place right after the nozzle moves away. This allows users to create complex shapes out of liquids by holding them trapped in three-dimensional space until the time comes to solidify the printed structure. Embedded 3D printing has been effective for structuring <a href="https://doi.org/10.1126/sciadv.1500655">a variety of soft materials</a> like hydrogels, microparticles and even living cells. </p>
<p>However, printing with silicone has remained challenging. Liquid silicone is an oil, while most support materials are water-based. Oil and water have a high <a href="https://doi.org/10.1039/D0SM01971B">interfacial tension</a>, which is the driving force behind why oil droplets take on circular shapes in water. This force also causes 3D-printed silicone structures to deform, even in a support medium.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/517272/original/file-20230323-26-beetje.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Close-up of oil droplets on water" src="https://images.theconversation.com/files/517272/original/file-20230323-26-beetje.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/517272/original/file-20230323-26-beetje.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/517272/original/file-20230323-26-beetje.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/517272/original/file-20230323-26-beetje.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/517272/original/file-20230323-26-beetje.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/517272/original/file-20230323-26-beetje.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/517272/original/file-20230323-26-beetje.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Interfacial tension is what causes oil droplets to form on water and silicone to deform.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/abstract-art-oil-in-water-royalty-free-image/1251006239">Baac3nes/Moment via Getty Images</a></span>
</figcaption>
</figure>
<p>Even worse, these interfacial forces drive small-diameter silicone features to break into droplets as they are being printed. A lot of research has gone into making silicone materials that can be printed <a href="https://doi.org/10.1016/j.addma.2018.10.002">without a support</a>, but these heavy modifications also modify the properties that users care about, like how soft and stretchy the silicone is.</p>
<h2>3D-printing silicone with AMULIT</h2>
<p>As researchers working at the interface of <a href="https://scholar.google.com/citations?user=PYnyFvsAAAAJ&hl=en">soft matter physics, mechanical engineering</a> and <a href="https://scholar.google.com/citations?user=rVFU5coAAAAJ&hl=en">materials science</a>, we decided to tackle the problem of interfacial tension by developing a <a href="https://doi.org/10.1126/science.ade4441">support material made from silicone oil</a>.</p>
<p>We reasoned that most silicone inks would be chemically similar to our silicone support material, thus dramatically reducing interfacial tension, but also different enough to remain separated when put together for 3D printing. We created many candidate support materials but found that the best approach was to make a dense emulsion of silicone oil and water. One can think about it like crystal clear mayonnaise, made from packed microdroplets of water in a continuum of silicone oil. We call this method <a href="https://doi.org/10.1126/science.ade4441">additive manufacturing at ultra-low interfacial tension, or AMULIT</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/517288/original/file-20230323-22-p3hiok.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Diagram of AMULIT technique printing the bronchi of a lung model within a bath of supporting material, with a close-up of the needle depositing layers of silicone to make the tissue." src="https://images.theconversation.com/files/517288/original/file-20230323-22-p3hiok.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/517288/original/file-20230323-22-p3hiok.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=380&fit=crop&dpr=1 600w, https://images.theconversation.com/files/517288/original/file-20230323-22-p3hiok.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=380&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/517288/original/file-20230323-22-p3hiok.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=380&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/517288/original/file-20230323-22-p3hiok.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=478&fit=crop&dpr=1 754w, https://images.theconversation.com/files/517288/original/file-20230323-22-p3hiok.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=478&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/517288/original/file-20230323-22-p3hiok.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=478&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">This diagram shows the AMULIT technique printing the bronchi of a lung model within a bath of supporting material. At right is a close-up of the needle depositing layers of silicone to make the tissue.</span>
<span class="attribution"><a class="source" href="https://www.science.org/doi/10.1126/science.ade4441">Senthilkumar Duraivel/Angelini Lab</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>With our AMULIT support medium, we were able to print off-the-shelf silicone at high resolution, creating features as small as 8 micrometers (around 0.0003 inches) in diameter. The printed structures are as stretchy and durable as their traditionally molded counterparts. </p>
<p>These capabilities enabled us to 3D-print accurate models of a patient’s brain blood vessels based on a 3D scan as well as a functioning heart valve model based on average human anatomy.</p>
<h2>3D silicone printing in health care</h2>
<p>Silicone is a <a href="https://doi.org/10.1002/14356007.a24_057">critical component of innumerable products</a>, from everyday consumer goods like cookware and toys to advanced technologies in the electronics, aerospace and health care industries. </p>
<p>Silicone products are typically made by pouring or injecting liquid silicone into a mold and removing the cast after solidification. The expense and difficulty of manufacturing high-precision molds limits manufacturers to products with only a few predetermined sizes, shapes and designs. Removing delicate silicone structures from molds without damage is an additional barrier, and manufacturing defects increase when molding highly intricate structures. </p>
<p>Overcoming these challenges could allow for the development of advanced silicone-based technologies in the health care industry, where personalized implants or patient-specific mimics of physiological structures could transform care.</p><img src="https://counter.theconversation.com/content/202226/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Organ models that more accurately capture finer details could reduce surgical error and lead to personalized implants.Senthilkumar Duraivel, Ph.D. Candidate in Materials Science and Engineering, University of FloridaThomas Angelini, Associate Professor of Mechanical and Aerospace Engineering, University of FloridaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2023082023-03-24T12:36:27Z2023-03-24T12:36:27ZHow do superconductors work? A physicist explains what it means to have resistance-free electricity<figure><img src="https://images.theconversation.com/files/517284/original/file-20230323-14-cz0c5g.jpg?ixlib=rb-1.1.0&rect=62%2C98%2C5928%2C3574&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Magnetic levitation is just one of the interesting attributes that make superconductors so interesting.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/illustration/magnet-floating-above-a-superconductor-royalty-free-illustration/1301762762?phrase=superconductor&adppopup=true">Mark Garlick/Science Photo Library vie Getty Images</a></span></figcaption></figure><p>The modern world runs on electricity, and wires are what carry that electricity to every light, television, heating system, cellphone and computer on the planet. Unfortunately, on average, about <a href="https://www.nrdc.org/bio/jennifer-chen/lost-transmission-worlds-biggest-machine-needs-update">5%</a> of the power generated at a coal or solar power plant is lost as the electricity is transmitted from the plant to its final destination. This amounts to a <a href="https://www.nrdc.org/bio/jennifer-chen/lost-transmission-worlds-biggest-machine-needs-update">US$6 billion loss annually</a> in the U.S. alone. </p>
<p>For decades, scientists have been <a href="https://www.energy.gov/science/doe-explainssuperconductivity">developing materials called superconductors</a> that transmit electricity with nearly 100% efficiency. <a href="https://scholar.google.com/citations?user=5gCcMuMAAAAJ&hl=en&oi=sra">I am a physicist</a> who investigates how superconductors work at the atomic level, how current flows at very low temperatures, and how applications such as levitation can be realized. Recently, researchers have made significant progress toward developing superconductors that can function at <a href="https://doi.org/10.1088/1361-648X/ac2864">relatively normal temperatures and pressures</a>.</p>
<p>To see why these recent advances are so exciting and what impact they may have on the world, it’s important to understand how superconducting materials work.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/517258/original/file-20230323-1492-h3oux6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Two lightbulbs next to each other with one showing a glowing filament." src="https://images.theconversation.com/files/517258/original/file-20230323-1492-h3oux6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/517258/original/file-20230323-1492-h3oux6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=517&fit=crop&dpr=1 600w, https://images.theconversation.com/files/517258/original/file-20230323-1492-h3oux6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=517&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/517258/original/file-20230323-1492-h3oux6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=517&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/517258/original/file-20230323-1492-h3oux6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=650&fit=crop&dpr=1 754w, https://images.theconversation.com/files/517258/original/file-20230323-1492-h3oux6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=650&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/517258/original/file-20230323-1492-h3oux6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=650&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Most materials offer resistance when electricity runs through them and heat up. Resistance is how filaments in an incandescent lightbulb produce light.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Carbonfilament.jpg#/media/File:Carbonfilament.jpg">Ulfbastel/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<h2>A resistance-free material</h2>
<p>A superconductor is any material that conducts electricity without offering any resistance to the flow of the electric current. </p>
<p>This resistance-free attribute of superconductors contrasts dramatically with <a href="https://sciencenotes.org/examples-of-conductors-and-insulators/">standard conductors</a> of electricity – like copper or aluminum – which heat up when current passes through them. This is similar to quickly sliding your hand across a smooth, slick surface compared to sliding your hand over a rough rug. The rug generates more friction and, therefore, more heat, too. Electric toasters and older-style incandescent lightbulbs use resistance to produce heat and light, but resistance can pose <a href="https://resources.pcb.cadence.com/blog/2022-the-influence-of-the-joule-heating-effect-on-pcbs-and-ics">problems for electronics</a>. Semiconductors have resistance below that of conductors, but still higher than that of superconductors. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/sJLSL61sLZ0?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Superconductive materials repel magnetic fields, making it possible to levitate a magnet above a superconductor.</span></figcaption>
</figure>
<p>Another characteristic of superconductors is that they repel magnetic fields. You may have seen videos of the fascinating result of this effect: It is possible to levitate magnets above a superconductor. </p>
<h2>How do superconductors work?</h2>
<p>All superconductors are made of materials that are electrically neutral – that is, their atoms contain negatively charged electrons that surround a nucleus with an equal number of positively charged protons. </p>
<p>If you attach one end of a wire to something that is positively charged, and the other end to something that is negatively charged, the system will want to reach equilibrium by moving electrons around. This causes the electrons in the wire to try to move through the material. </p>
<p>At normal temperatures, electrons move in somewhat erratic paths. They can generally succeed in moving through a wire freely, but every once in a while they collide with the nuclei of the material. These collisions are what obstruct the flow of electrons, cause resistance and heat up the material.</p>
<p>The nuclei of all atoms are constantly vibrating. In a superconducting material, instead of flitting around randomly, the moving electrons get passed along from atom to atom in such a way that they keep <a href="https://www.energy.gov/science/bes/articles/electrons-line-dance-superconductor#:%7E:text=Superconductors%20are%20materials%20that%20can,called%20a%20pair%20density%20wave.">in sync</a> with the vibrating nuclei. This coordinated movement produces no collisions and, therefore, no resistance and no heat.</p>
<p>The colder a material gets, the more organized the movement of electrons and nuclei becomes. This is why existing superconductors only work at extremely <a href="https://journals.aps.org/pr/abstract/10.1103/PhysRev.108.1175">low temperatures</a>. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/517262/original/file-20230323-14-bajdav.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A close-up view of a computer chip." src="https://images.theconversation.com/files/517262/original/file-20230323-14-bajdav.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/517262/original/file-20230323-14-bajdav.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=419&fit=crop&dpr=1 600w, https://images.theconversation.com/files/517262/original/file-20230323-14-bajdav.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=419&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/517262/original/file-20230323-14-bajdav.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=419&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/517262/original/file-20230323-14-bajdav.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=527&fit=crop&dpr=1 754w, https://images.theconversation.com/files/517262/original/file-20230323-14-bajdav.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=527&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/517262/original/file-20230323-14-bajdav.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=527&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Superconducting materials would allow engineers to fit many more circuits onto a single computer chip.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Siliconchip_by_shapeshifter.png#/media/File:Siliconchip_by_shapeshifter.png">David Carron/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<h2>Benefits to electronics</h2>
<p>If scientists can develop a room-temperature superconducting material, wires and circuitry in electronics would be <a href="https://www.psfc.mit.edu/events/2017/high-temperature-superconductors-advantages-and-key-challenges-in-their-deployment-for">much more efficient</a> and produce far less heat. The benefits of this would be widespread.</p>
<p>If the wires used to transmit electricity were replaced with superconducting materials, these new lines would be able to carry up to <a href="https://phys.org/news/2014-05-longest-superconducting-cable-worldwide.html">five times as much electricity</a> more efficiently than current cables. </p>
<p>The speed of computers is mostly limited by how many wires can be packed into a single electric circuit on a chip. The density of wires is often <a href="https://link.springer.com/referenceworkentry/10.1007/978-0-387-09766-4_499">limited by waste heat</a>. If engineers could use superconducting wires, they could fit many more wires in a circuit, leading to faster and cheaper electronics.</p>
<p>Finally, with room-temperature superconductors, magnetic levitation could be used for <a href="https://www.intechopen.com/chapters/16183">all sorts of applications</a>, from trains to energy-storage devices.</p>
<p>With <a href="https://www.nytimes.com/2023/03/08/science/room-temperature-superconductor-ranga-dias.html">recent advances providing exciting news</a>, both researchers looking at the fundamental physics of high-temperature superconductivity as well as technologists waiting for new applications are paying attention.</p><img src="https://counter.theconversation.com/content/202308/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Mishkat Bhattacharya receives funding from the Office of Naval Research. </span></em></p>Superconductors are materials that can transmit electricity without any resistance. Researchers are getting closer to creating superconducting materials that can function in everyday life.Mishkat Bhattacharya, Professor of Physics and Astronomy, Rochester Institute of TechnologyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2023152023-03-22T18:58:22Z2023-03-22T18:58:22ZResearchers turned superglue into a recyclable, cheap, oil-free plastic alternative<figure><img src="https://images.theconversation.com/files/517011/original/file-20230322-26-2s4b3l.jpg?ixlib=rb-1.1.0&rect=24%2C96%2C4001%2C3024&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Researchers discovered a way to turn superglue into strong, clear plastic that can be made into many shapes.</span> <span class="attribution"><span class="source">Allison Christy</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><p><em>The <a href="https://theconversation.com/us/topics/research-brief-83231">Research Brief</a> is a short take about interesting academic work.</em> </p>
<h2>The big idea</h2>
<p><a href="https://www.boisestate.edu/coen-msl/group/">Our team</a> used superglue as a starting material to <a href="https://www.science.org/doi/10.1126/sciadv.adg2295">develop a low-cost, recyclable and easily produced transparent plastic</a> called polyethyl cyanoacrylate that has properties similar to those of plastics used for single-use products like cutlery, cups and packaging. Unlike most traditional plastics, this new plastic can be easily converted back to its starting materials, even when combined with unwashed municipal plastic waste.</p>
<p>To make a plastic from superglue, we first had to address the very issue that makes superglue so “super” – it sticks to just about everything. When superglue is used to stick something together, it is actually <a href="https://www.compoundchem.com/2015/10/15/superglue/">reacting with moisture in the air or on the surface</a> of whatever is being glued together. This reaction forms molecular chains of repeating superglue units called polymers. The polymers made when gluing something together are short and don’t bind to each other well, which makes the glue brittle and easy to break. </p>
<p>While short polymers are good for glue, long polymers have more binding locations and <a href="https://www.science.org.au/curious/everything-else/polymers">result in stronger materials</a>. Our team realized that if we could create longer versions of the same type of polymers made from superglue, we might be able to produce a strong plastic. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/517014/original/file-20230322-22-qpq0uh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A stack of plastic petri dishes." src="https://images.theconversation.com/files/517014/original/file-20230322-22-qpq0uh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/517014/original/file-20230322-22-qpq0uh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/517014/original/file-20230322-22-qpq0uh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/517014/original/file-20230322-22-qpq0uh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/517014/original/file-20230322-22-qpq0uh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/517014/original/file-20230322-22-qpq0uh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/517014/original/file-20230322-22-qpq0uh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The new plastic is made by elongating the molecular chains that make up superglue.</span>
<span class="attribution"><span class="source">Allison Christy</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>The way we make these plastics is relatively simple when compared with how <a href="https://www.bpf.co.uk/plastipedia/how-is-plastic-made.aspx">other types of plastics are made</a> – we simply mixed acetone and a little bit of an eco-friendly catalyst into store-bought superglue. Once this mixture dries, it produces a solid, glassy plastic made up of long polymer chains. </p>
<p>In our lab, we can easily produce up to 10 pounds of this material in a matter of days and turn it into usable products. By pouring the mixture into molds before it dries, we can make plastic objects in many shapes, like bowls and cutlery. We also discovered that heating up the plastic after it dries not only allowed us to shape the material into other products, but also strengthened the plastic.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/517012/original/file-20230322-18-txzoa3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A clear spoon and knife." src="https://images.theconversation.com/files/517012/original/file-20230322-18-txzoa3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/517012/original/file-20230322-18-txzoa3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=392&fit=crop&dpr=1 600w, https://images.theconversation.com/files/517012/original/file-20230322-18-txzoa3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=392&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/517012/original/file-20230322-18-txzoa3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=392&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/517012/original/file-20230322-18-txzoa3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=493&fit=crop&dpr=1 754w, https://images.theconversation.com/files/517012/original/file-20230322-18-txzoa3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=493&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/517012/original/file-20230322-18-txzoa3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=493&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The new superglue plastic is much easier to recycle than the kind of plastic used to make many single-use objects like cutlery.</span>
<span class="attribution"><span class="source">Allison Christy</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Why it matters</h2>
<p>When manufacturers need to produce a stiff plastic object – like cutlery, disposable razors, CD cases or plastic models – they often turn to polystyrene. Polystyrene is one of the most <a href="https://www.greenpeace.org/usa/news/new-greenpeace-report-plastic-recycling-is-a-dead-end-street-year-after-year-plastic-recycling-declines-even-as-plastic-waste-increases/">widely produced and least recycled types of plastic</a>.</p>
<p>Because our superglue plastic has properties similar to polystyrene – it is light, durable, cheap and easy to mass-produce – it could replace polystyrene in many products. But there are two distinct benefits of our superglue-based material: It isn’t made from oil and is easy to recycle. </p>
<p>When our material is heated to 410 degrees Fahrenheit (210 C), the long molecule chains made of repeating superglue units break apart into their small, individual superglue molecules. At this point, the superglue molecules turn into a vapor that is easy to separate out from a mixed waste stream of other plastics, paper, food residue, aluminum and other refuse <a href="https://www.europarl.europa.eu/EPRS/EPRS-Briefing-564398-Understanding-waste-streams-FINAL.pdf">commonly found in recycling waste streams</a>. Once you collect the superglue vapor, you can cool it and turn it right back into our new plastic with over 90% efficiency.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/517013/original/file-20230322-1056-ok9urc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A wavy bowl holding jelly beans." src="https://images.theconversation.com/files/517013/original/file-20230322-1056-ok9urc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/517013/original/file-20230322-1056-ok9urc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=609&fit=crop&dpr=1 600w, https://images.theconversation.com/files/517013/original/file-20230322-1056-ok9urc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=609&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/517013/original/file-20230322-1056-ok9urc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=609&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/517013/original/file-20230322-1056-ok9urc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=765&fit=crop&dpr=1 754w, https://images.theconversation.com/files/517013/original/file-20230322-1056-ok9urc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=765&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/517013/original/file-20230322-1056-ok9urc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=765&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The superglue plastic can be shaped or molded into complex designs.</span>
<span class="attribution"><span class="source">Allison Christy</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>What’s next?</h2>
<p>Since superglue is inexpensive and already produced on an industrial scale, we imagine our method of creating superglue plastics should be easy to scale up. Finally, the machinery used to make superglue could also be used to recycle the superglue plastics and could be simply adapted into existing <a href="http://www.madehow.com/Volume-1/Super-Glue.html">industrial processes</a>.</p>
<p>Finding a <a href="https://lbl.recyclist.co/guide/6-plastic-polystyrene/?embeddedguide=true">replacement for polystyrene</a> is a big step toward sustainable plastics, but polystyrene is only one of <a href="https://www.plasticsmakeitpossible.com/about-plastics/types-of-plastics/professor-plastics-how-many-types-of-plastics-are-there/">thousands of plastics used today</a>. Our team is now designing superglue-based plastics with properties that resemble other kinds of commodity plastics, while still being easy to produce and recycle.</p><img src="https://counter.theconversation.com/content/202315/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Scott Phillips receives funding from the Army Research Office. </span></em></p><p class="fine-print"><em><span>Allison Christy does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Researchers have developed a method for producing strong plastic materials by tweaking the chemical structure of superglue.Allison Christy, Graduate Research Assistant, Boise State UniversityScott Phillips, Professor of Materials Science and Engineering, Boise State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1966642023-01-31T19:12:20Z2023-01-31T19:12:20ZOur future could be full of undying, self-repairing robots. Here’s how<figure><img src="https://images.theconversation.com/files/507247/original/file-20230131-24-1wnmot.jpg?ixlib=rb-1.1.0&rect=419%2C14%2C4109%2C2200&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">frank60/Shutterstock</span></span></figcaption></figure><p>With generative artificial intelligence (AI) systems such as <a href="https://theconversation.com/chatgpt-dall-e-2-and-the-collapse-of-the-creative-process-196461">ChatGPT</a> and <a href="https://theconversation.com/ai-image-generation-is-advancing-at-astronomical-speeds-can-we-still-tell-if-a-picture-is-fake-191674">StableDiffusion</a> being the talk of the town right now, it might feel like we’ve taken a giant leap closer to a sci-fi reality where AIs are physical entities all around us.</p>
<p>Indeed, computer-based AI appears to be advancing at an unprecedented rate. But the rate of advancement in robotics – which we could think of as the potential physical embodiment of AI – is slow.</p>
<p>Could it be that future AI systems will need robotic “bodies” to interact with the world? If so, will nightmarish ideas like the self-repairing, shape-shifting <a href="https://en.wikipedia.org/wiki/T-1000">T-1000 robot</a> from the Terminator 2 movie come to fruition? And could a robot be created that could “live” forever?</p>
<h2>Energy for ‘life’</h2>
<p>Biological lifeforms like ourselves need energy to operate. We get ours via a combination of food, water, and oxygen. The majority of plants also need access to light to grow.</p>
<p>By the same token, an everlasting robot needs an ongoing energy supply. Currently, electrical power dominates energy supply in the world of robotics. Most robots are powered by the <a href="https://blog.mentyor.com/chemistry-of-batteries/">chemistry of batteries</a>. </p>
<p>An alternative battery type has been proposed that uses <a href="https://www.popularmechanics.com/science/green-tech/a35970222/radioactive-diamond-battery-will-run-for-28000-years/">nuclear waste and ultra-thin diamonds at its core</a>. The inventors, a San Francisco startup called <a href="https://ndb.technology/">Nano Diamond Battery</a>, claim a possible battery life of tens of thousands of years. Very small robots would be an ideal user of such batteries.</p>
<p>But a more likely long-term solution for powering robots may involve different chemistry – and even biology. In 2021, scientists from the Berkeley Lab and UMAss Amherst in the US demonstrated tiny nanobots could get their energy from chemicals in the <a href="https://newscenter.lbl.gov/2021/12/08/liquid-robots-never-run-out/">liquid they swim in</a>.</p>
<p>The researchers are now working out how to scale up this idea to larger robots that can work on solid surfaces.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/BdS72O2c9nQ?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<h2>Repairing and copying oneself</h2>
<p>Of course, an undying robot might still need occasional repairs.</p>
<p>Ideally, a robot would repair itself if possible. In 2019, a Japanese research group demonstrated <a href="https://robots.ieee.org/robots/pr2/">a research robot called PR2</a> tightening its <a href="https://ieeexplore.ieee.org/document/9035045">own screw using a screwdriver</a>. This is like self-surgery! However, such a technique would only work if non-critical components needed repair.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/47NjYRWVjLk?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>Other research groups are exploring how soft robots can self-heal when damaged. A group in Belgium showed how a robot they developed recovered after being stabbed six times in one of its legs. It stopped for a few minutes until its skin healed itself, <a href="https://www.newscientist.com/article/2350609-self-healing-robot-recovers-from-being-stabbed-then-walks-off/">and then walked off</a>.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/KTJaxxzTKYc?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>Another unusual concept for repair is to use other things a robot might find in the environment to replace its broken part.</p>
<p>Last year, scientists reported how <a href="https://www.popularmechanics.com/technology/robots/a40746165/dead-spider-leg-grippers/">dead spiders can be used as robot grippers</a>. This form of robotics is known as “necrobotics”. The idea is to use dead animals as ready-made mechanical devices and attach them to robots to become part of the robot.</p>
<figure class="align-center ">
<img alt="A video of a spider attached to a syringe being lowered onto another spider and picking it up" src="https://images.theconversation.com/files/507011/original/file-20230130-26-2uvwwp.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/507011/original/file-20230130-26-2uvwwp.gif?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=472&fit=crop&dpr=1 600w, https://images.theconversation.com/files/507011/original/file-20230130-26-2uvwwp.gif?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=472&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/507011/original/file-20230130-26-2uvwwp.gif?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=472&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/507011/original/file-20230130-26-2uvwwp.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=593&fit=crop&dpr=1 754w, https://images.theconversation.com/files/507011/original/file-20230130-26-2uvwwp.gif?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=593&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/507011/original/file-20230130-26-2uvwwp.gif?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=593&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The proof-of-concept in necrobotics involved taking a dead spider and ‘reanimating’ its hydraulic legs with air, creating a surprisingly strong gripper.</span>
<span class="attribution"><span class="source">Preston Innovation Laboratory/Rice University</span></span>
</figcaption>
</figure>
<h2>A robot colony?</h2>
<p>From all these recent developments, it’s quite clear that in principle, a single robot may be able to live forever. But there is a very long way to go.</p>
<p>Most of the proposed solutions to the energy, repair and replication problems have only been demonstrated in the lab, in very controlled conditions and generally at tiny scales.</p>
<p>The ultimate solution may be one of large colonies or swarms of tiny robots who share a common brain, or mind. After all, this is exactly how many species of insects have evolved.</p>
<p>The concept of the “mind” of an ant colony has been pondered for decades. Research published in 2019 showed ant colonies themselves have a form of memory that is <a href="https://aeon.co/ideas/an-ant-colony-has-memories-that-its-individual-members-dont-have">not contained within any of the ants</a>.</p>
<p>This idea aligns very well with one day having massive clusters of robots that could use this trick to replace individual robots when needed, but keep the cluster “alive” indefinitely.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/507246/original/file-20230130-10893-la43e0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A close-up swarm of orange ants forming a living bridge between two green leaves" src="https://images.theconversation.com/files/507246/original/file-20230130-10893-la43e0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/507246/original/file-20230130-10893-la43e0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/507246/original/file-20230130-10893-la43e0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/507246/original/file-20230130-10893-la43e0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/507246/original/file-20230130-10893-la43e0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/507246/original/file-20230130-10893-la43e0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/507246/original/file-20230130-10893-la43e0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Ant colonies can contain ‘memories’ that are distributed between many individual insects.</span>
<span class="attribution"><span class="source">frank60/Shutterstock</span></span>
</figcaption>
</figure>
<p>Ultimately, the scary robot scenarios outlined in countless science fiction books and movies are unlikely to suddenly develop without anyone noticing.</p>
<p>Engineering ultra-reliable hardware is extremely difficult, especially with complex systems. There are currently no engineered products that can last forever, or even for hundreds of years. If we do ever invent an undying robot, we’ll also have the chance to build in some safeguards.</p><img src="https://counter.theconversation.com/content/196664/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jonathan Roberts is Director of the Australian Cobotics Centre, the Technical Director of the Advanced Robotics for Manufacturing (ARM) Hub, and is a Chief Investigator at the QUT Centre for Robotics. He receives funding from the Australian Research Council. He was the co-founder of the UAV Challenge - an international drone competition.</span></em></p>If we’re going to put an AI brain somewhere, it’s likely going to be a robot. The next step – making that robot immortal.Jonathan Roberts, Professor in Robotics, Queensland University of TechnologyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1921542023-01-05T16:19:06Z2023-01-05T16:19:06ZFoams used in car seats and mattresses are hard to recycle – we made a plant-based version that avoids polyurethane’s health risks, too<figure><img src="https://images.theconversation.com/files/501976/original/file-20221219-16-5a8mrd.jpg?ixlib=rb-1.1.0&rect=6%2C92%2C4091%2C2881&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">You may be sitting on polyurethane foam right now.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/golden-sponge-foam-texture-royalty-free-image/134942499">Akhmad Bayuri/iStock/Getty Images Plus</a></span></figcaption></figure><p><em>The <a href="https://theconversation.com/us/topics/research-brief-83231">Research Brief</a> is a short take about interesting academic work.</em></p>
<h2>The big idea</h2>
<p>A new plant-based substitute for polyurethane foam eliminates the health risk of the material, commonly found in insulation, car seats and other types of cushioning, and it’s more environmentally sustainable, <a href="https://www.nature.com/articles/s41893-022-01022-3">our new research shows</a>.</p>
<p>Polyurethane foams are all around you, anywhere a lightweight material is needed for cushioning or structural support. But they’re typically made using chemicals that are <a href="https://www.osha.gov/isocyanates">suspected carcinogens</a>.</p>
<p>Polyurethanes are typically produced in a very fast reaction between two chemicals made by the petrochemical industry: polyols and isocyanates. While much work has gone into finding replacements for the polyol component of polyurethane foams, the isocyanate component has largely remained, despite its <a href="https://www.osha.gov/isocyanates">consequences for human health</a>. <a href="https://doi.org/10.1039/D0GC01659D">Bio-based foams</a> can avoid that component.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/488841/original/file-20221008-59028-9iaitu.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Four chunks of bio-based foam, looking a lot like brownies on a tray." src="https://images.theconversation.com/files/488841/original/file-20221008-59028-9iaitu.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/488841/original/file-20221008-59028-9iaitu.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=184&fit=crop&dpr=1 600w, https://images.theconversation.com/files/488841/original/file-20221008-59028-9iaitu.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=184&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/488841/original/file-20221008-59028-9iaitu.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=184&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/488841/original/file-20221008-59028-9iaitu.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=232&fit=crop&dpr=1 754w, https://images.theconversation.com/files/488841/original/file-20221008-59028-9iaitu.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=232&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/488841/original/file-20221008-59028-9iaitu.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=232&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">These bio-based foams avoid the need for petroleum products.</span>
<span class="attribution"><span class="source">Srikanth Pilla</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>We created a <a href="https://www.nature.com/articles/s41893-022-01022-3">durable bio-based foam</a> using lignin, a byproduct of the paper pulping industry, and a vegetable oil-based curing agent that introduces flexibility and toughness to the final material.</p>
<p>At the heart of the innovation is the ability to create a system that “gels,” both in the sense that the materials are compatible with one another and that they physically create a gel quickly so that the addition of a foaming agent can create the lightweight structure associated with polyurethane foams.</p>
<p>Lignin is a <a href="https://doi.org/10.1039/D1GC02744A">difficult material to convert into a usable chemical</a>, given its complicated and heterogeneous structure. We used this structure to create a network of bonds that enabled what we believe is the world’s first lignin-based nonisocyanate foam.</p>
<p>The foam can also be <a href="https://doi.org/10.1039/C7GC01496A">recycled</a> because it has bonds that can <a href="https://doi.org/10.1038/s41557-020-00614-w">unzip</a> the chemical network after it has formed. The main components used to produce the foam can then be extracted and used again.</p>
<h2>Why it matters</h2>
<p>Polyurethane foams are the world’s sixth-most-produced plastic yet among the least <a href="https://www.americanchemistry.com/industry-groups/center-for-the-polyurethanes-industry-cpi/applications-benefits/sustainability">recycled materials</a>. They are also designed for durability, meaning they will remain in the environment for several generations. </p>
<p>They contribute to the plastic waste problem for the world’s oceans, land and air, and to <a href="https://doi.org/10.1016/j.jhazmat.2021.127861">human health problems</a>. Today, plastics can be found in <a href="https://doi.org/10.1016/j.ancene.2016.01.002">virtually every creature in the terrestrial ecosystem</a>. And since most plastics are made from petroleum products, they’re connected to fossil fuel extraction, which contributes to climate change.</p>
<p>The fully bio-based origin of our foams addresses the issue of carbon neutrality, and the chemical recycling capability ensures that waste plastic has a value attached to it so it is less likely to be thrown away. Ensuring <a href="https://doi.org/10.1002/macp.202100488">waste has value</a> is a hallmark of the circular approach to manufacturing – attaching a monetary value to things tends to decrease the amount that is discarded.</p>
<figure class="align-center ">
<img alt="Illustration shows the recycling process including unzipping the molecules." src="https://images.theconversation.com/files/490558/original/file-20221019-19-a7wqv6.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/490558/original/file-20221019-19-a7wqv6.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=537&fit=crop&dpr=1 600w, https://images.theconversation.com/files/490558/original/file-20221019-19-a7wqv6.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=537&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/490558/original/file-20221019-19-a7wqv6.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=537&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/490558/original/file-20221019-19-a7wqv6.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=675&fit=crop&dpr=1 754w, https://images.theconversation.com/files/490558/original/file-20221019-19-a7wqv6.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=675&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/490558/original/file-20221019-19-a7wqv6.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=675&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">How the chemicals in bio-based foams can be recycled and reused.</span>
<span class="attribution"><span class="source">Srikanth Pilla</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>We hope the nature of these foams inspires others to design plastics with the full life cycle in mind. Just as plastics need to be designed according to properties of their initial application, they also need to be designed to avoid the final destination of 90% of plastic waste: landfills and the environment.</p>
<h2>What’s next</h2>
<p>Our initial versions of bio-based foams produce a rigid material suitable for use in foam-core boards used in construction or for insulation in refrigerators. We have also created a lightweight and flexible version that can be used for cushioning and packaging applications. Initial testing of these materials showed good durability in wet conditions, increasing their chance of gaining commercial adoption. </p>
<figure class="align-center ">
<img alt="Two men and two women stand over a beaker with dark liquid in it" src="https://images.theconversation.com/files/490561/original/file-20221019-20-p2m2rj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/490561/original/file-20221019-20-p2m2rj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/490561/original/file-20221019-20-p2m2rj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/490561/original/file-20221019-20-p2m2rj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/490561/original/file-20221019-20-p2m2rj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/490561/original/file-20221019-20-p2m2rj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/490561/original/file-20221019-20-p2m2rj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The authors with two students show methods for recycling bio-based foam.</span>
<span class="attribution"><a class="source" href="https://news.clemson.edu/green-foam-eliminates-the-need-for-toxic-chemicals/">Clemson University</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Polyurethane foams are used so extensively because of their <a href="https://doi.org/10.3390/ma11101841">versatility</a>. The formulation that we initially discovered is being translated to create a library of precursors that can be mixed to produce the desired properties, like strength and washability, in each application.</p><img src="https://counter.theconversation.com/content/192154/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Srikanth Pilla receives funding from the National Science Foundation (award # 2122822) and Department of Energy (award # DE-SC0021367) to support this work.</span></em></p><p class="fine-print"><em><span>James Sternberg receives funding from the National Science Foundation (award # 2122822) and Department of Energy (award # DE-SC0021367) to support this work. </span></em></p>Polyurethane foams are the world’s sixth-most-produced plastic yet among the least recycled materials.Srikanth Pilla, Professor of Engineering, Clemson UniversityJames Sternberg, Research Assistant Professor of Automotive Engineering, Clemson UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1942382022-11-29T13:34:50Z2022-11-29T13:34:50ZGraphene is a proven supermaterial, but manufacturing the versatile form of carbon at usable scales remains a challenge<figure><img src="https://images.theconversation.com/files/497098/original/file-20221123-22-6q2g12.jpg?ixlib=rb-1.1.0&rect=17%2C34%2C1260%2C770&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Graphene has many incredible physical properties that arise from its one-atom-thick carbon structure.</span> <span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Graphen.jpg#/media/File:Graphen.jpg">AlexanderAlUS/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>“Future chips may be <a href="https://www.msn.com/en-us/news/technology/future-chips-may-be-10-times-faster-all-thanks-to-graphene/ar-AA14qqsu">10 times faster, all thanks to graphene</a>”; “Graphene may be <a href="https://www.newswise.com/coronavirus/wonder-material-can-be-used-to-detect-covid-19-quickly-accurately/?article_id=753042">used in COVID-19 detection</a>”; and “Graphene allows batteries to <a href="https://www.theverge.com/22771702/graphene-power-bank-review-price-speed">charge 5x faster</a>” – those are just a handful of recent dramatic headlines lauding the possibilities of graphene. Graphene is an incredibly light, strong and durable material made of a single layer of carbon atoms. With these properties, it is no wonder researchers have been studying ways that graphene could advance material science and technology for decades.</p>
<p>I never know what to expect when I tell people <a href="https://scholar.google.com/citations?user=yykU46oAAAAJ&hl=en&oi=ao">I study graphene</a> – some have never heard of it, while others have seen some version of these headlines and inevitably ask, “So what’s the holdup?” </p>
<p>Graphene is a fascinating material, just as the sensational headlines suggest, but it is only just starting be used in real-world applications. The problem lies not in graphene’s properties, but in the fact that it is still incredibly difficult and expensive to manufacture at commercial scales.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/497095/original/file-20221123-20-ztyacw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A black and white image of a crystalline layer on a surface." src="https://images.theconversation.com/files/497095/original/file-20221123-20-ztyacw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/497095/original/file-20221123-20-ztyacw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=554&fit=crop&dpr=1 600w, https://images.theconversation.com/files/497095/original/file-20221123-20-ztyacw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=554&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/497095/original/file-20221123-20-ztyacw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=554&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/497095/original/file-20221123-20-ztyacw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=697&fit=crop&dpr=1 754w, https://images.theconversation.com/files/497095/original/file-20221123-20-ztyacw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=697&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/497095/original/file-20221123-20-ztyacw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=697&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Pure graphene is a uniform, single-atom-thick crystal of carbon arranged in a hexagonal pattern, as seen in this electron microscope image.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Graphene-TEM.jpg#/media/File:Graphene-TEM.jpg">M.H. Gass/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<h2>What is graphene?</h2>
<p>Graphene is most simply defined as a single layer of carbon atoms bonded together in a hexagonal, sheetlike structure. You can think of pure graphene as a one-layer-thick sheet of carbon tissue paper that happens to be the strongest material on Earth. </p>
<p>Graphene usually comes in the form of a powder made of small, individual sheets that are roughly the diameter of a grain of sand. An individual sheet of graphene is <a href="https://doi.org/10.1126/science.1235126">200 times stronger than an equally thin piece of steel</a>. Graphene is also <a href="https://doi.org/10.1038/nature26160">extremely conductive</a>, holds together at <a href="https://doi.org/10.3367/UFNe.0184.201410c.1045">up to 1,300 degrees Fahrenheit (700 C)</a>, can <a href="https://doi.org/10.1016/j.cej.2019.05.034">withstand acids</a> and is <a href="https://news.mit.edu/2017/3-d-graphene-strongest-lightest-materials-0106">flexible and very lightweight</a>.</p>
<p>Because of these properties, graphene could be extremely useful. The material can be used to <a href="https://www.azonano.com/article.aspx?ArticleID=5468#">create flexible electronics</a> and to <a href="https://www.azocleantech.com/article.aspx?ArticleID=936">purify or desalinate water</a>. And adding just 0.03 ounces (1 gram) of graphene to 11.5 pounds (5 kilograms) of cement <a href="https://firstgraphene.net/applications/concrete/#:%7E:text=The%20use%20of%20graphene%20concrete,new%20generation%20of%20concrete%20designs">increases the strength of the cement by 35%</a>. </p>
<p>As of late 2022, Ford Motor Co., with which I worked as part of my doctoral research, is one of the the only companies to use graphene at industrial scales. Starting in 2018, Ford began making plastic for its vehicles that was 0.5% graphene – <a href="https://media.ford.com/content/fordmedia/fna/us/en/news/2018/10/09/ford-innovates-with-miracle-material-powerful-graphene-for-vehicle-parts.html">increasing the plastic’s strength by 20%</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/497097/original/file-20221123-26-1wxtw5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A close-up photo of the tip of a pencil writing on paper." src="https://images.theconversation.com/files/497097/original/file-20221123-26-1wxtw5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/497097/original/file-20221123-26-1wxtw5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/497097/original/file-20221123-26-1wxtw5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/497097/original/file-20221123-26-1wxtw5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/497097/original/file-20221123-26-1wxtw5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/497097/original/file-20221123-26-1wxtw5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/497097/original/file-20221123-26-1wxtw5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Researchers made the first piece of graphene by peeling layers of carbon off of graphite – or pencil lead – with tape.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/macro-pencil-tip-resting-on-blank-white-paper-royalty-free-image/856908132?phrase=pencil%20lead&adppopup=true">Rapid Eye/E+ via Getty Images</a></span>
</figcaption>
</figure>
<h2>How to make a supermaterial</h2>
<p>Graphene is produced in two principal ways that can be described as either a top-down or bottom-up process.</p>
<p>The world’s <a href="https://www.graphene-info.com/graphene-history-controversy-and-nobel-prize">first sheet of graphene</a> was created in 2004 out of graphite. Graphite, commonly known as pencil lead, is composed of millions of graphene sheets stacked on top of one another. Top-down synthesis, also known as <a href="https://www.azonano.com/article.aspx?ArticleID=5471">graphene exfoliation</a>, works by peeling off the thinnest possible layers of carbon from graphite. Some of the earliest graphene sheets were made by using cellophane tape to <a href="https://science.wonderhowto.com/how-to/make-graphene-sheets-from-graphite-flakes-and-cellophane-tape-402113/">peel off layers of carbon from a larger piece of graphite</a>. </p>
<p>The problem is that the molecular forces holding graphene sheets together in graphite are very strong, and it’s hard to pull sheets apart. Because of this, graphene produced using top-down methods is often many layers thick, has holes or deformations, and <a href="https://doi.org/10.1002/adma.201803784">can contain impurities</a>. Factories can produce a few tons of mechanically or chemically exfoliated graphene per year, and for many applications – like mixing it into plastic – the <a href="https://www.compositesworld.com/articles/graphene-101-forms-properties-and-applications">lower-quality graphene works well</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/497094/original/file-20221123-16-meka9j.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A thin, folded, rough-edged piece of graphene." src="https://images.theconversation.com/files/497094/original/file-20221123-16-meka9j.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/497094/original/file-20221123-16-meka9j.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=420&fit=crop&dpr=1 600w, https://images.theconversation.com/files/497094/original/file-20221123-16-meka9j.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=420&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/497094/original/file-20221123-16-meka9j.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=420&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/497094/original/file-20221123-16-meka9j.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=528&fit=crop&dpr=1 754w, https://images.theconversation.com/files/497094/original/file-20221123-16-meka9j.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=528&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/497094/original/file-20221123-16-meka9j.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=528&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Graphene flakes made from top-down methods are usually more than one atom thick and have impurities like folds and tears, as seen in this image.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Graphene_flakes.JPG#/media/File:Graphene_flakes.JPG">Дагесян Саркис Арменакович/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Top-down, exfoliated graphene is far from perfect, and some applications do need that pristine single sheet of carbon. </p>
<p>Bottom-up synthesis builds the carbon sheets one atom at a time over a few hours. This process – called <a href="https://www.graphenea.com/pages/cvd-graphene#.Y3vcF3bMI2w">vapor deposition</a> – allows researchers to produce high-quality graphene that is one atom thick and up to 30 inches across. This yields graphene with the best possible mechanical and electrical properties. The problem is that with a bottom-up synthesis, it can take <a href="https://doi.org/10.1021/acs.chemrev.8b00325">hours to make even 0.00001 gram</a> – not nearly fast enough for any large scale uses like in <a href="https://doi.org/10.1038/nnano.2010.132">flexible touch-screen electronics or solar panels</a>, for example.</p>
<h2>So what’s the holdup?</h2>
<p>Current production methods of graphene, both top-down and bottom-up, are expensive as well as energy and resource intensive, and simply produce too little product, too slowly. </p>
<p>Some companies do manufacture graphene and sell it for <a href="https://bigthink.com/the-present/flash-graphene/">US$60,000 to $200,000 per ton</a>. There are a limited number of uses that make sense at these high costs.</p>
<p>While small amounts of top-down or bottom-up graphene can satisfy the needs of researchers, for companies even just the process of prototyping a new material, application or manufacturing process requires many pounds of graphene powder or hundreds of graphene sheets and a lot of time and effort. It took significant investment and more than four years of study, development and optimization before graphene hit the production line at Ford. </p>
<p>Current production can barely cover experimentation, much less widespread use. </p>
<h2>Improving manufacturing</h2>
<p>For a material that has been around since only 2004, a lot of progress has been made in scaling up the production and implementation of graphene. </p>
<p>There are hints that graphene is starting to break through at a commercial level. There are a huge number of <a href="https://fortune.com/2020/12/13/what-is-graphene-entrepreneurs-headphones-smartphones-construction-eco-friendly-thinnest-material-on-earth/">graphene-related startups looking at a wide range of uses</a> ranging from <a href="https://nanotechenergy.com/">energy storage</a> to <a href="https://graphmatech.com/">composites</a> to <a href="https://www.inbrain-neuroelectronics.com/">nerve stimulation</a>. Major companies – such as <a href="https://electrek.co/2022/03/22/elon-musk-tesla-working-new-manganese-battery-cell/">Tesla</a>, <a href="https://www.thegraphenecouncil.org/blogpost/1501180/347505/LG-Electronics-Secures-Its-Position-in-CVD-Graphene-Production">LG</a> and <a href="https://www.thegraphenecouncil.org/blogpost/1501180/359799/BASF-Applies-Expertise-to-Graphene-Commercialization">chemical giant BASF</a> – are also investigating how graphene could be used, in rechargeable batteries, flexible or wearable electronics and next-generation materials.</p>
<p>Graphene is ripe for a breakthrough that will bring down the cost and increase the scale of production, and this is an <a href="https://www.phdassistance.com/blog/graphenes-for-research-and-the-growing-number-of-publications-per-year/">area of intense academic research</a>. One new technique discovered in 2020, called <a href="https://doi.org/10.1038/s41586-020-1938-0">flash joule heating</a>, is especially promising. Researchers have shown that passing large amounts of electricity through any carbon source reorganizes the carbon-carbon bonds into a graphene structure. Using this process, it is possible to make many pounds of high-quality graphene for a relatively low cost out of any carbon-containing material like coal or even trash. A <a href="https://www.universalmatter.com/">company called Universal Matter Inc.</a> is already commercializing the process.</p>
<p>Once the cost of graphene comes down, the commercial applications will follow. The <a href="https://www.fortunebusinessinsights.com/graphene-market-102930">appetite for graphene is huge</a>, but it is going to take some time before this material lives up to its potential.</p><img src="https://counter.theconversation.com/content/194238/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Kevin Wyss receives funding through the NSF Graduate Research Fellowship, as well as the Rice University Stauffer-Rothrock Fellowship. He has worked in collaboration with Ford Motor Company and Universal Matter, but is not an employee.</span></em></p>Graphene is superstrong and superconductive, and it has applications in everything from construction to electronics. But to date there have been almost no commercial uses of the material.Kevin Wyss, PhD Student in Chemistry, Rice UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1928002022-10-19T18:37:54Z2022-10-19T18:37:54ZA new type of material called a mechanical neural network can learn and change its physical properties to create adaptable, strong structures<figure><img src="https://images.theconversation.com/files/490679/original/file-20221019-12170-qt1idp.JPG?ixlib=rb-1.1.0&rect=48%2C78%2C3977%2C2939&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">This connection of springs is a new type of material that can change shape and learn new properties.</span> <span class="attribution"><span class="source">Jonathan Hopkins</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><p><em>The <a href="https://theconversation.com/us/topics/research-brief-83231">Research Brief</a> is a short take about interesting academic work.</em></p>
<h2>The big idea</h2>
<p>A new type of material can learn and improve its ability to deal with unexpected forces thanks to a unique lattice structure with connections of variable stiffness, as <a href="https://doi.org/10.1126/scirobotics.abq7278">described in a new paper</a> by my colleagues and me. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/490682/original/file-20221019-23-rnqscu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A hand holding a small, complex cube of plastic." src="https://images.theconversation.com/files/490682/original/file-20221019-23-rnqscu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/490682/original/file-20221019-23-rnqscu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/490682/original/file-20221019-23-rnqscu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/490682/original/file-20221019-23-rnqscu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/490682/original/file-20221019-23-rnqscu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/490682/original/file-20221019-23-rnqscu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/490682/original/file-20221019-23-rnqscu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Architected materials – like this 3D lattice – get their properties not from what they are made out of, but from their structure.</span>
<span class="attribution"><span class="source">Ryan Lee</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>The new material is a type of architected material, which gets its properties mainly from the geometry and specific traits of its design rather than what it is made out of. Take hook-and-loop fabric closures like Velcro, for example. It doesn’t matter whether it is made from cotton, plastic or any other substance. As long as one side is a fabric with stiff hooks and the other side has fluffy loops, the material will have the sticky properties of Velcro.</p>
<p>My colleagues and I based our new material’s architecture on that of an artificial neural network – layers of interconnected nodes that can <a href="https://doi.org/10.1109/ACCESS.2019.2945545">learn to do tasks</a> by changing how much importance, or weight, they place on each connection. We hypothesized that a mechanical lattice with physical nodes could be trained to take on certain mechanical properties by adjusting each connection’s rigidity. </p>
<p>To find out if a mechanical lattice would be able to adopt and maintain new properties – like taking on a new shape or changing directional strength – we started off by building a computer model. We then selected a desired shape for the material as well as input forces and had a computer algorithm tune the tensions of the connections so that the input forces would produce the desired shape. We did this training on 200 different lattice structures and found that a triangular lattice was best at achieving all of the shapes we tested. </p>
<p>Once the many connections are tuned to achieve a set of tasks, the material will continue to react in the desired way. The training is – in a sense – remembered in the structure of the material itself.</p>
<p>We then built a physical prototype lattice with adjustable electromechanical springs arranged in a triangular lattice. The prototype is made of 6-inch connections and is about 2 feet long by 1½ feet wide. And it worked. When the lattice and algorithm worked together, the material was able to learn and change shape in particular ways when subjected to different forces. We call this new material a mechanical neural network.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/490683/original/file-20221019-14-emmwwr.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A photo of hydraulic springs arranged in a triangular lattice" src="https://images.theconversation.com/files/490683/original/file-20221019-14-emmwwr.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/490683/original/file-20221019-14-emmwwr.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/490683/original/file-20221019-14-emmwwr.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/490683/original/file-20221019-14-emmwwr.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/490683/original/file-20221019-14-emmwwr.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/490683/original/file-20221019-14-emmwwr.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/490683/original/file-20221019-14-emmwwr.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The prototype is 2D, but a 3D version of this material could have many uses.</span>
<span class="attribution"><span class="source">Jonathan Hopkins</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Why it matters</h2>
<p>Besides some <a href="https://doi.org/10.1007/BF00436764">living tissues</a>, very few materials can learn to be better at dealing with unanticipated loads. Imagine a plane wing that suddenly catches a gust of wind and is forced in an unanticipated direction. The wing can’t change its design to be stronger in that direction.</p>
<p>The prototype lattice material we designed can adapt to changing or unknown conditions. In a wing, for example, these changes could be the accumulation of internal damage, changes in how the wing is attached to a craft or fluctuating external loads. Every time a wing made out of a mechanical neural network experienced one of these scenarios, it could strengthen and soften its connections to maintain desired attributes like directional strength. Over time, through successive adjustments made by the algorithm, the wing adopts and maintains new properties, adding each behavior to the rest as a sort of muscle memory.</p>
<p>This type of material could have far reaching applications for the longevity and efficiency of built structures. Not only could a wing made of a mechanical neural network material be stronger, it could also be trained to morph into shapes that maximize fuel efficiency in response to changing conditions around it.</p>
<h2>What’s still not known</h2>
<p>So far, our team has worked only with 2D lattices. But using computer modeling, we predict that 3D lattices would have a much larger capacity for learning and adaptation. This increase is due to the fact that a 3D structure could have tens of times more connections, or springs, that don’t intersect with one another. However, the mechanisms we used in our first model are far too complex to support in a large 3D structure. </p>
<h2>What’s next</h2>
<p>The material my colleagues and I created is a proof of concept and shows the potential of mechanical neural networks. But to bring this idea into the real world will require figuring out how to make the individual pieces smaller and with precise properties of flex and tension.</p>
<p>We hope new research in the <a href="https://doi.org/10.1039/C8MH01100A">manufacturing of materials at the micron scale</a>, as well as work on <a href="https://doi.org/10.1016/j.eml.2020.101120">new materials with adjustable stiffness</a>, will lead to advances that make powerful smart mechanical neural networks with micron-scale elements and dense 3D connections a ubiquitous reality in the near future.</p><img src="https://counter.theconversation.com/content/192800/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ryan Lee has received funding from the Air Force Office of Science Research . </span></em></p>Computer-based neural networks can learn to do tasks. A new type of material, called a mechanical neural network, applies similar ideas to a physical structure.Ryan H. Lee, PhD Student in Mechanical and Aerospace Engineering, University of California, Los AngelesLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1901342022-09-12T20:27:36Z2022-09-12T20:27:36ZFolded diamond has been discovered in a rare type of meteorite. How is this possible?<figure><img src="https://images.theconversation.com/files/483643/original/file-20220909-20-4vcbiw.jpg?ixlib=rb-1.1.0&rect=19%2C118%2C4373%2C2845&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.eurekalert.org/multimedia/948716">Nick Wilson</a></span></figcaption></figure><p>A “folded diamond” doesn’t sound entirely plausible. But that’s exactly what we’ve found inside a rare group of meteorites known as ureilites, which likely came from the mantle of a <a href="https://en.wikipedia.org/wiki/Dwarf_planet">dwarf planet</a> or very large asteroid that was destroyed 4.56 billion years ago in a giant collision.</p>
<p>Within these space rocks, we found layered diamonds with distinctive fold patterns. Our discovery is published today in the journal <a href="https://www.pnas.org/cgi/doi/10.1073/pnas.2208814119">Proceedings of the National Academy of Sciences</a>.</p>
<p>Now of course, everyone knows diamond is <a href="https://pursuit.unimelb.edu.au/articles/diamonds-the-hard-facts">the hardest naturally occurring material</a>, so the obvious question was – how on Earth (or in space!) could a folded diamond possibly form?!</p>
<p>This was exactly the sort of curiosity-piquing observation that sends scientists diving down rabbit holes for months on end.</p>
<h2>A new analysis technique</h2>
<p>Carbon, one of the most abundant elements in the universe, can form all kinds of structures. Among the more familiar ones are graphite and, of course, diamond. But there’s also an unusual hexagonal form of diamond known as lonsdaleite, which has been suggested to be even harder than standard cubic diamonds.</p>
<figure class="align-center ">
<img alt="A red, yellow and purple coloured marbling on a turquoise background" src="https://images.theconversation.com/files/483643/original/file-20220909-20-4vcbiw.jpg?ixlib=rb-1.1.0&rect=19%2C118%2C4373%2C2845&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/483643/original/file-20220909-20-4vcbiw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=424&fit=crop&dpr=1 600w, https://images.theconversation.com/files/483643/original/file-20220909-20-4vcbiw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=424&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/483643/original/file-20220909-20-4vcbiw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=424&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/483643/original/file-20220909-20-4vcbiw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=533&fit=crop&dpr=1 754w, https://images.theconversation.com/files/483643/original/file-20220909-20-4vcbiw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=533&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/483643/original/file-20220909-20-4vcbiw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=533&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Distribution of lonsdaleite in yellow, diamond in pink, iron in red, silicon in green, and magnesium in blue within a meteorite detected by electron probe microanalysis.</span>
<span class="attribution"><a class="source" href="https://www.eurekalert.org/multimedia/948716">Nick Wilson</a></span>
</figcaption>
</figure>
<p>Our team includes a bunch of people who drive development of advanced analysis techniques. At CSIRO, Nick Wilson, Colin MacRae and Aaron Torpy developed a new approach in electron microscopy to map the distribution of diamond, graphite and lonsdaleite in the meteorites. </p>
<p>When our mapping suggested the folded diamond might actually be lonsdaleite, we – Dougal McCulloch, Alan Salek and Matthew Field at RMIT – performed a more detailed investigation via a method called high-resolution transmission electron microscopy (<a href="https://en.wikipedia.org/wiki/Transmission_electron_microscopy">TEM</a>).</p>
<p>The results were exciting: we had found some of the largest lonsdaleite crystallites (microscopic crystals) ever discovered, about 1 micrometre across. So, those intriguing fold shapes were composed of polycrystalline lonsdaleite, meaning they were made from numerous tiny crystals.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/483167/original/file-20220907-16-j5r5p8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Folded structures visible in a greyscale image and the same visible in purple underneath" src="https://images.theconversation.com/files/483167/original/file-20220907-16-j5r5p8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/483167/original/file-20220907-16-j5r5p8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=833&fit=crop&dpr=1 600w, https://images.theconversation.com/files/483167/original/file-20220907-16-j5r5p8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=833&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/483167/original/file-20220907-16-j5r5p8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=833&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/483167/original/file-20220907-16-j5r5p8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1047&fit=crop&dpr=1 754w, https://images.theconversation.com/files/483167/original/file-20220907-16-j5r5p8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1047&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/483167/original/file-20220907-16-j5r5p8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1047&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Microscope photo (top) and cathodoluminescence map (bottom) of folded lonsdaleite, purple, with diamond in green-yellow (field of view 0.25 mm).</span>
<span class="attribution"><span class="source">PNAS, 2022</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>Reconstructing the cataclysm</h2>
<p>And there was even more. We found the lonsdaleite had been partially converted to diamond and graphite, giving us clues to the sequence of events that had happened in the meteorites. Follow-up work at the Australian Synchrotron by Helen Brand confirmed this result. </p>
<p>By comparing the diamond, graphite and lonsdaleite across 18 different ureilite meteorites, we started to form a picture of what probably happened to produce the folded structures we found. At the first stage, graphite crystals folded deep inside the mantle of the asteroid thanks to high temperatures causing the other surrounding minerals to grow, pushing aside the graphite crystals. (You can see this in the schematic below.)</p>
<figure class="align-center ">
<img alt="Complex chart showing the stages of an asteroid crumbling apart" src="https://images.theconversation.com/files/483169/original/file-20220907-24-5dem3n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/483169/original/file-20220907-24-5dem3n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=458&fit=crop&dpr=1 600w, https://images.theconversation.com/files/483169/original/file-20220907-24-5dem3n.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=458&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/483169/original/file-20220907-24-5dem3n.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=458&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/483169/original/file-20220907-24-5dem3n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=576&fit=crop&dpr=1 754w, https://images.theconversation.com/files/483169/original/file-20220907-24-5dem3n.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=576&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/483169/original/file-20220907-24-5dem3n.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=576&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Schematic indicating the timing and positions of diamond and lonsdaleite formation as the ureilite parent asteroid was partially destroyed by a giant impact (Ol, olivine; Px, pyroxene).</span>
<span class="attribution"><span class="source">PNAS, 2022</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>The second stage happened in the aftermath of the gigantic collision that catastrophically disrupted the ureilite parent asteroid. <a href="https://onlinelibrary.wiley.com/doi/abs/10.1111/maps.13755">Evidence in the meteorites</a> suggested the disruption event produced a rich mix of fluids and gases as it progressed.</p>
<p>This mix then caused lonsdaleite to form by replacement of the folded graphite crystals, almost perfectly preserving the intricate textures of the graphite. Of course, it’s not actually possible to <em>fold</em> lonsdaleite or diamond – it formed by replacement of pre-existing shapes.</p>
<p>We think this was driven by the hot fluid mix as pressure and temperature dropped immediately after the cataclysm. Then, shortly after, diamond and graphite partially replaced the lonsdaleite as the fluid further decompressed and cooled to form a gas mixture.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/how-rare-minerals-form-when-meteorites-slam-into-earth-105129">How rare minerals form when meteorites slam into Earth</a>
</strong>
</em>
</p>
<hr>
<h2>Manufacturing clues from nature</h2>
<p>The process is quite similar to a process used to manufacture diamonds known as <a href="https://www.youtube.com/watch?v=YTML-JGRfMc">chemical vapour deposition</a>. These manufactured diamonds are widely used in industry today, particularly for cutting and grinding because diamond is so hard. The difference is that we think the lonsdaleite replaced the shaped graphite at moderately higher pressures than those normally used to grow diamonds, from a <a href="https://en.wikipedia.org/wiki/Supercritical_fluid">supercritical fluid</a> rather than a gas. </p>
<p>So, nature appears to have given us clues on how to make shaped ultra-hard micro machine parts! If we can find a way to replicate the process preserved in the meteorites, we can make these machine parts by replacement of pre-shaped graphite with lonsdaleite.</p>
<p>Being able to study these weird folded diamonds was possible because lead author Andrew Tomkins had time to follow his nose – we call this type of research “curiosity-driven science”. However, although <a href="https://news.harvard.edu/gazette/story/2018/04/most-transformative-meds-originate-in-curiosity-driven-science-evidence-says/">curiosity-driven science produces important breakthroughs</a>, it isn’t normally funded by major funding agencies. They like to see well thought-out details for grand projects that already have a solid foundation of prior research.</p>
<p>We think a good way to boost Australia’s innovation would be to provide recognised science innovators a small grant annually to spend on research as they see fit; no questions asked, no justification or follow-up required.</p>
<p>For curiosity-driven research like our project, scientists need a small amount of time (and money) that can be spent with complete freedom; this produces <a href="https://theconversation.com/the-secret-to-creativity-according-to-science-89592">the creativity</a> that drives innovation. You never know what else we might find out there.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/we-created-diamonds-in-mere-minutes-without-heat-by-mimicking-the-force-of-an-asteroid-collision-150369">We created diamonds in mere minutes, without heat — by mimicking the force of an asteroid collision</a>
</strong>
</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/190134/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Andrew Tomkins receives funding from the Australia Research Council. </span></em></p><p class="fine-print"><em><span>Alan Salek receives a RSS Scholarship. </span></em></p><p class="fine-print"><em><span>Dougal McCulloch receives funding from Australian Research Council.</span></em></p>An unusual folded shape in a meteorite prompted scientists to dive deep into a rabbit hole – discovering a potential new way to make specially shaped diamonds in the lab.Andrew Tomkins, Geologist, Monash UniversityAlan Salek, PhD Researcher, RMIT UniversityDougal McCulloch, Professor, RMIT UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1852722022-06-23T11:48:54Z2022-06-23T11:48:54ZWhat is BPA and why is it in so many plastic products?<figure><img src="https://images.theconversation.com/files/470073/original/file-20220621-15-8umt72.jpg?ixlib=rb-1.1.0&rect=81%2C65%2C5381%2C3571&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Most plastic products that are clear and strong are made using bisphenol A, or BPA.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/drinking-water-bottle-for-sports-in-female-hand-on-royalty-free-image/1331157592">Beton Studio/iStock via Getty Images</a></span></figcaption></figure><p>Bisphenol A, or BPA, is a chemical widely used to make hard, clear plastics. It is an endocrine disruptor that has been linked to <a href="https://theconversation.com/decades-of-research-document-the-detrimental-health-effects-of-bpa-an-expert-on-environmental-pollution-and-maternal-health-explains-what-it-all-means-184630">many negative health effects</a>, including <a href="https://doi.org/10.1016/j.ando.2013.04.002">cardiovascular diseases and diabetes</a>. In 2013, the U.S. government <a href="https://www.federalregister.gov/documents/2013/07/12/2013-16684/indirect-food-additives-adhesives-and-components-of-coatings">banned its use in baby products that come into contact with food</a>, like bottles or the packaging of infant formula.</p>
<p>At the time, the U.S. Food and Drug Administration concluded that some exposure was safe for adults. But other health agencies, including the European Food Safety Authority, have concluded that the levels of BPA the FDA considers safe <a href="https://connect.efsa.europa.eu/RM/s/publicconsultation2/a0l1v00000E8BRD/pc0109">may have adverse health effects for adults as well</a>. </p>
<p>In early June 2022, the FDA signaled that it is reconsidering what amount of exposure to BPA is safe for adults, announcing that it would <a href="https://www.edf.org/media/fda-agrees-reconsider-safety-bpa-food-packaging">reconsider its guidance on the use of BPA</a> in plastics that come into contact with food. </p>
<p>As a <a href="https://scholar.google.com/citations?user=-tWvBjMAAAAJ&hl=en&oi=ao">synthetic polymer chemist</a>, I think a lot about how to design new polymers, with particular focus on <a href="https://www.wesleyan.edu/academics/faculty/belling/profile.html">how to do so sustainably</a>. It’s natural to wonder why companies don’t simply replace BPA with another chemical if health is such a concern. The secret to what makes BPA such an irreplaceable ingredient in plastics is the same thing that leads to its health risks – the molecule’s chemical structure. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/469367/original/file-20220616-12-e91m82.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A chemical diagram showing two hexagonal rings with OH on either side." src="https://images.theconversation.com/files/469367/original/file-20220616-12-e91m82.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/469367/original/file-20220616-12-e91m82.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=267&fit=crop&dpr=1 600w, https://images.theconversation.com/files/469367/original/file-20220616-12-e91m82.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=267&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/469367/original/file-20220616-12-e91m82.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=267&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/469367/original/file-20220616-12-e91m82.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=336&fit=crop&dpr=1 754w, https://images.theconversation.com/files/469367/original/file-20220616-12-e91m82.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=336&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/469367/original/file-20220616-12-e91m82.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=336&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Bisphenol A is made of two carbon rings with small alcohol groups attached and is used to produce strong, clear plastics.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Bisphenol-A-Skeletal.svg#/media/File:Bisphenol-A-Skeletal.svg">Darkness3560/Wikimedia Commons</a></span>
</figcaption>
</figure>
<h2>What is BPA?</h2>
<p>BPA is a small molecule made of two carbon rings with a bonded oxygen and hydrogen attached to either end. BPA can react with other carbon-based molecules to form long chains, with the BPA molecules stitched together by small chemical links.</p>
<p>Nearly all of the BPA produced in the world is used to manufacture plastics, mostly a specific type called polycarbonate. BPA-derived polycarbonates are transparent, incredibly strong, light and don’t begin to melt or lose structural integrity <a href="https://polymerdatabase.com/polymer%20classes/Polycarbonate%20type.html">until they reach very high temperatures</a>. These properties make polycarbonates excellently suited for use in everything from the lenses of eyeglasses to water bottles.</p>
<h2>It’s all about the structure</h2>
<p>In chemistry, structure means everything. The reasons different materials have different properties is due to their chemical structure.</p>
<p>BPA polymers are rigid because the carbon rings in BPA molecules are themselves rigid. Compare this to polyethylene, the thin, flexible material used to make plastic bags. The long chains of repeating molecules that make up polyethylene are very flexible. So the plastics they produce are highly pliable, too. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/469369/original/file-20220616-11-jmi2pw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A table with many colored sunglasses." src="https://images.theconversation.com/files/469369/original/file-20220616-11-jmi2pw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/469369/original/file-20220616-11-jmi2pw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/469369/original/file-20220616-11-jmi2pw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/469369/original/file-20220616-11-jmi2pw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/469369/original/file-20220616-11-jmi2pw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/469369/original/file-20220616-11-jmi2pw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/469369/original/file-20220616-11-jmi2pw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">BPA plastics are strong, transparent, light and have a high melting point, which makes them the perfect material for lenses for your eyeware.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/high-angle-view-of-colorful-sunglasses-for-sale-in-royalty-free-image/979123212?adppopup=true">Nipitphon Na Chiangmai / EyeEm via Getty Images</a></span>
</figcaption>
</figure>
<h2>How do BPAs leach out of plastic?</h2>
<p>When BPA plastics are made, nearly all the individual molecules of BPA are chemically bound to the plastic. So most of the BPA that leaches out of food containers or water bottles results from the <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2254523/">plastic slowly breaking down</a>.</p>
<p>When BPA polycarbonates are exposed to water and heat – say, when you put a plastic bottle in your dishwasher – the chemical bonds that link these BPA molecules together can break down in a <a href="https://doi.org/10.1002/app.1981.070260603">process known as hydrolysis</a>. Because of its unique structure, BPA polycarbonates are generally more susceptible to hydrolysis than plastics like polyethylene. </p>
<p>Hydrolysis breaks down plastic at a chemical level, and this releases a small amount of BPA molecules into the environment. In one study, researchers found that the process of washing a polycarbonate bottle leached <a href="https://doi.org/10.1016%2Fj.chemosphere.2011.06.060">0.2 to 0.3 milligrams of BPA</a> into each liter of water. For context, this is hundreds of times less concentrated <a href="https://www.open.edu/openlearn/mod/oucontent/view.php?printable=1&id=20880">than the levels of calcium and sodium in drinking water</a>.</p>
<h2>The search for a BPA replacement</h2>
<p>BPA is an endocrine disruptor, meaning it disrupts how hormones function in the body. Given the <a href="https://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/expert-answers/bpa/faq-20058331#:%7E:text=Exposure%20to%20BPA%20is%20a,2%20diabetes%20and%20cardiovascular%20disease">negative health effects of consuming BPA</a> and the fact that it breaks down when exposed to water, chemists have been searching for replacements for years. </p>
<p>A major concern with designing new plastics is that swapping out BPA for another molecule may not get rid of the negative health effects. Just as the chemical structure of BPA determines the properties of the material, the structure is also what triggers the negative biological effects. Endocrine disruptors like BPA, due to their similar structures to natural hormones, can <a href="https://doi.org/10.1038/s41574-019-0273-8">bind to and activate endocrine receptors</a>.</p>
<p>Research has shown that structurally similar chemical replacements, such as bisphenol F, <a href="https://www.ehn.org/bpa-replacement-2656483035.html">produce similar health effects as BPA</a>. </p>
<p>It’s also not easy to swap in a new molecule that has a different chemical structure because the plastic will then lose the desirable characteristics of BPA polycarbonates. But there is some promising new research. One path of inquiry focuses on making polycarbonates by <a href="https://doi.org/10.1038/ncomms11862">reacting rigid bio-based molecules with carbon dioxide gas</a>.</p>
<p>Polycarbonates are a ubiquitious part of modern life. As researchers develop new materials, it is important to consider not only the health risks – as the EPA is doing with BPA – but the environmental effects as well.</p><img src="https://counter.theconversation.com/content/185272/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Benjamin Elling receives funding from the American Chemical Society’s Petroleum Research Fund</span></em></p>The US Environmental Protection Agency is reexamining the health effects of bisphenol A. A chemist explains why BPA is in plastics and why it’s hard to find a safe replacement.Benjamin Elling, Assistant Professor of Chemistry, Wesleyan UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1730482021-12-21T14:55:12Z2021-12-21T14:55:12ZNickel oxide is a material that can ‘learn’ like animals and could help further artificial intelligence research<figure><img src="https://images.theconversation.com/files/436979/original/file-20211210-136652-1mgxcfu.JPG?ixlib=rb-1.1.0&rect=0%2C530%2C3953%2C3095&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Nickel oxide, the gray-and-black-striped material, demonstrates unique properties when exposed to hydrogen.</span> <span class="attribution"><span class="source">Purdue University/Kayla Wiles</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><p><em>The <a href="https://theconversation.com/us/topics/research-brief-83231">Research Brief</a> is a short take about interesting academic work.</em></p>
<h2>The big idea</h2>
<p>A unique material, nickel oxide demonstrates the <a href="https://doi.org/10.1073/pnas.2017239118">ability to learn things about its environment</a> in a way that emulates the most basic learning abilities of animals, as my colleagues and I describe in a new paper.</p>
<p>For over half a century, neuroscientists have studied sea slugs to understand basic animal learning. Two fundamental concepts of learning are <a href="https://doi.org/10.1016/j.nlm.2008.09.012">habituation</a> and <a href="https://doi.org/10.1126/science.11560">sensitization</a>. Habituation occurs when an organism’s response to a repeated stimulus continuously decreases. When researchers first touch a sea slug, its gills retract. But the more they touch the slug, the <a href="https://doi.org/10.1126/science.167.3926.1745">less it retracts its gills</a>. Sensitization is an organism’s extreme reaction to a harmful or unexpected stimulus. If researchers then shock a sea slug, it will <a href="https://doi.org/10.1126/science.11560">retract its gills much more dramatically</a> than when it was merely touched. This is sensitization. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/436815/original/file-20211209-27-12uc827.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A small square of material inside a test chamber of metal with tubes." src="https://images.theconversation.com/files/436815/original/file-20211209-27-12uc827.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/436815/original/file-20211209-27-12uc827.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/436815/original/file-20211209-27-12uc827.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/436815/original/file-20211209-27-12uc827.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/436815/original/file-20211209-27-12uc827.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/436815/original/file-20211209-27-12uc827.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/436815/original/file-20211209-27-12uc827.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">When nickel oxide is alternately bathed in hydrogen gas and air, its behavior changes.</span>
<span class="attribution"><span class="source">Purdue University/Kayla Wiles</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Nickel oxide has features that are strikingly similar to this learning behavior. Instead of gills retracting, we measured the change in electrical conductivity of the material. The stimulus, instead of a finger poke, was repeatedly alternating the environment of the nickel oxide between normal air and hydrogen gas.</p>
<p>Nickel oxide is interesting because when you expose it to hydrogen gas, its crystalline structure subtly changes and <a href="https://doi.org/10.1002/pssa.200778914">more electrons become available to generate an electrical current</a>. In our experiment, we kept switching between the hydrogen-only and regular air environments. You would expect the electrical conductivity to oscillate up and down directly in relation to the exposure to hydrogen or air. But just as with the sea slugs, the change in conductivity of the nickel oxide slowly went down the more we stimulated it. It got habituated to the hydrogen.</p>
<p>When we exposed the material to bright light or ozone, though, it rapidly changed its conductivity – the same way a slug will always respond dramatically to a small shock.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/436813/original/file-20211209-140267-qt8jx9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A small piece of material underneath a large piece of scientific equipment." src="https://images.theconversation.com/files/436813/original/file-20211209-140267-qt8jx9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/436813/original/file-20211209-140267-qt8jx9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/436813/original/file-20211209-140267-qt8jx9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/436813/original/file-20211209-140267-qt8jx9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/436813/original/file-20211209-140267-qt8jx9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/436813/original/file-20211209-140267-qt8jx9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/436813/original/file-20211209-140267-qt8jx9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The conductivity of nickel oxide stores information similarly to the way slugs learn.</span>
<span class="attribution"><span class="source">Purdue University/Kayla Wiles</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Why it matters</h2>
<p>The ability to learn, remember or forget information as needed is a powerful skill for any animal or machine. So far, the vast majority of research in the field of artificial intelligence has <a href="https://doi.org/10.1126/science.aaa8415">focused on software-based approaches to machine learning</a>, with far less effort dedicated to <a href="https://doi.org/10.1063/1.5113574">studying the learning abilities of materials</a>.</p>
<p>At the center of these two related areas of research lies the field of <a href="https://doi.org/10.1038/s41586-019-1677-2">brain-inspired computers</a>. For intelligence to be encoded into hardware, scientists need semiconductors that can learn from past experience and adapt to dynamic environments in a physical way similar to that of neurons in animal brains. Our new research showing how nickel oxide demonstrates features of learning hints at how this or similar materials could serve as building blocks for computers of the future. </p>
<h2>What still isn’t known</h2>
<p>Before such materials can be incorporated into computer chips there are some knowledge gaps that need to be addressed. For instance, it is not yet clear at what <a href="https://doi.org/10.1146/annurev-neuro-090919-022842">time scales a material needs to learn</a> for it to be useful in electrical systems. How quickly does something need to learn or forget to be useful? Another unknown is how or whether it is possible to change the structure of nickel oxide to produce different learning behaviors.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/436812/original/file-20211209-141979-3zqxkp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A small square of gray material with stripes." src="https://images.theconversation.com/files/436812/original/file-20211209-141979-3zqxkp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/436812/original/file-20211209-141979-3zqxkp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/436812/original/file-20211209-141979-3zqxkp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/436812/original/file-20211209-141979-3zqxkp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/436812/original/file-20211209-141979-3zqxkp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/436812/original/file-20211209-141979-3zqxkp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/436812/original/file-20211209-141979-3zqxkp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">It is unclear whether nickel oxide itself can be used for computing, but the concepts at play could inspire further innovation.</span>
<span class="attribution"><span class="source">Purdue University/Erin Easterling</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>What’s next</h2>
<p>In addition to further experiments on the material itself, there are theoretical lessons to explore. Observations of collective behavior of animals in nature – such as bird flocks and schools of fish – have <a href="https://doi.org/10.1007/0-387-27705-6_6">inspired researchers to develop fields of AI like swarm intelligence</a>. In a similar fashion, the interesting collective motion of atoms and electrons in materials could inspire AI and hardware design in the future. </p>
<p>As new materials that can accommodate mobile atoms are discovered, I am optimistic we will see further breakthroughs that can bring researchers one step closer to designing computers that emulate animal brains.</p><img src="https://counter.theconversation.com/content/173048/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>S. Ramanathan receives funding from the National Science Foundation, Department of Defense agencies for basic research in physical sciences and engineering.</span></em></p>The ability to store information is central to learning and the field of artificial intelligence. Researchers have shown how a unique material shows basic learning properties similar to that of slugs.Shriram Ramanathan, Professor of Materials Engineering, Purdue UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1734722021-12-16T16:51:03Z2021-12-16T16:51:03ZA new approach finds materials that can turn waste heat into electricity<figure><img src="https://images.theconversation.com/files/437866/original/file-20211215-23-26cjm2.jpg?ixlib=rb-1.1.0&rect=48%2C37%2C3518%2C2500&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The Curiosity Mars rover, launched in November 2011, is powered by a nuclear battery that relies on thermoelectric materials to turn heat from radioactive decay into electricity.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/nasamarshall/25275103228">(NASA/JPL-Caltech/MSSS)</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc/4.0/">CC BY-NC</a></span></figcaption></figure><p>The need to transition to clean energy is apparent, urgent and inescapable. We must limit Earth’s rising temperature to within 1.5 C to avoid the worst effects of climate change — an especially daunting challenge in the face of the steadily increasing global demand for energy.</p>
<p>Part of the answer is using energy more efficiently. <a href="https://doi.org/10.1016/j.rser.2015.12.192">More than 72 per cent of all energy produced worldwide is lost in the form of heat</a>. For example, <a href="https://doi.org/10.1007/s11664-011-1580-6">the engine in a car uses only about 30 per cent of the gasoline it burns to move the car</a>. The remainder is dissipated as heat.</p>
<p>Recovering even a tiny fraction of that lost energy would have a tremendous impact on climate change. Thermoelectric materials, which convert wasted heat into useful electricity, can help. </p>
<p>Until recently, the identification of these materials had been slow. My colleagues and I have used quantum computations — a computer-based modelling approach to predict materials’ properties — to speed up that process and identify more than 500 thermoelectric materials that could convert excess heat to electricity, and help improve energy efficiency. </p>
<h2>Making great strides towards broad applications</h2>
<p>The transformation of heat into electrical energy by thermoelectric materials is based on the “Seebeck effect.” In 1826, German physicist <a href="https://doi.org/10.1002/andp.18260820302">Thomas Johann Seebeck observed that exposing the ends of joined pieces of dissimilar metals to different temperatures generated a magnetic field</a>, which was later recognized to be caused by an electric current.</p>
<p>Shortly after his discovery, <a href="http://dx.doi.org/10.1049/jste-1.1875.0018">metallic thermoelectric generators were fabricated to convert heat from gas burners into an electric current</a>. But, as it turned out, <a href="https://www.electronics-cooling.com/2006/11/the-seebeck-coefficient/">metals exhibit only a low Seebeck effect</a> — they are not very efficient at converting heat into electricity.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/437873/original/file-20211215-19-1nq0m8v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A black and white photo of a woman turning a dial on a large table top radio, with a lantern hanging above it." src="https://images.theconversation.com/files/437873/original/file-20211215-19-1nq0m8v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/437873/original/file-20211215-19-1nq0m8v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=639&fit=crop&dpr=1 600w, https://images.theconversation.com/files/437873/original/file-20211215-19-1nq0m8v.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=639&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/437873/original/file-20211215-19-1nq0m8v.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=639&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/437873/original/file-20211215-19-1nq0m8v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=804&fit=crop&dpr=1 754w, https://images.theconversation.com/files/437873/original/file-20211215-19-1nq0m8v.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=804&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/437873/original/file-20211215-19-1nq0m8v.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=804&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The kerosene radio was designed for rural areas, and was powered by the kerosene lamp hanging above it. The flame created a temperature difference across metals to generate the electrical current.</span>
<span class="attribution"><span class="source">('Popular Science', Issue 6, 1956)</span></span>
</figcaption>
</figure>
<p>In 1929, the Russian scientist <a href="https://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/ioffe-abram-fedorovich">Abraham Ioffe</a> revolutionized the field of thermoelectricity. He observed that semiconductors — materials whose ability to conduct electricity falls between that of metals (like copper) and insulators (like glass) — exhibit a significantly higher Seebeck effect than metals, boosting thermoelectric efficiency 40-fold, <a href="https://www.kelk.co.jp/english/useful/netsuden3.html">from 0.1 per cent to four per cent</a>. </p>
<p>This discovery led to the development of the first widely used thermoelectric generator, <a href="https://swling.com/blog/2020/05/soviet-era-kerosene-lamp-generator-gives-new-meaning-to-lets-fire-up-the-radio/">the Russian lamp</a> — a kerosene lamp that heated a thermoelectric material to power a radio.</p>
<h2>Are we there yet?</h2>
<p>Today, thermoelectric applications range from energy generation in <a href="https://www.energy.gov/ne/articles/what-radioisotope-power-system">space probes</a> to <a href="https://www.newair.com/blogs/learn/what-is-thermoelectric-cooling-and-is-it-right-for-you">cooling devices in portable refrigerators</a>. For example, space explorations are powered by radioisotope thermoelectric generators, <a href="https://solarsystem.nasa.gov/missions/cassini/radioisotope-thermoelectric-generator/">converting the heat from naturally decaying plutonium into electricity</a>. In the movie <em>The Martian,</em> for example, a box of plutonium saved the life of the character played by Matt Damon, by keeping him warm on Mars. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/0CvzBu5sTps?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">In the 2015 film, <em>The Martian</em>, astronaut Mark Watney (Matt Damon) digs up a buried thermoelectric generator to use the power source as a heater.</span></figcaption>
</figure>
<p>Despite this vast diversity of applications, wide-scale commercialization of thermoelectric materials is still limited by their low efficiency.</p>
<p>What’s holding them back? Two key factors must be considered: the conductive properties of the materials, and their ability to maintain a temperature difference, which makes it possible to generate electricity.</p>
<p>The best thermoelectric material would have the electronic properties of semiconductors and the poor heat conduction of glass. But this unique combination of properties is not found in naturally occurring materials. We have to engineer them.</p>
<h2>Searching for a needle in a haystack</h2>
<p>In the past decade, new strategies to engineer thermoelectric materials have emerged due to an enhanced understanding of their underlying physics. In a <a href="https://doi.org/10.1038/s41563-021-01064-6">recent study in <em>Nature Materials</em></a>, researchers from Seoul National University, Aachen University and Northwestern University reported they had engineered a material called tin selenide with the highest thermoelectric performance to date, nearly twice that of 20 years ago. But it took them nearly a decade to optimize it.</p>
<p>To speed up the discovery process, my colleagues and I have used quantum calculations to search for new thermoelectric candidates with high efficiencies. We searched a database containing thousands of materials to look for those that would have high electronic qualities and low levels of heat conduction, based on their chemical and physical properties. These insights helped us find the best materials to synthesize and test, and calculate their thermoelectric efficiency. </p>
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Read more:
<a href="https://theconversation.com/researchers-invent-device-that-generates-light-from-the-cold-night-sky-heres-what-it-means-for-millions-living-off-grid-123464">Researchers invent device that generates light from the cold night sky – here's what it means for millions living off grid</a>
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<p>We are almost at the point where thermoelectric materials can be widely applied, but first we need to develop much more efficient materials. With so many possibilities and variables, finding the way forward is like searching for a tiny needle in an enormous haystack.</p>
<p>Just as a metal detector can zero in on a needle in a haystack, quantum computations can accelerate the discovery of efficient thermoelectric materials. Such calculations can accurately predict electron and heat conduction (including the Seebeck effect) for thousands of materials and <a href="https://doi.org/10.1039/D0MH01112F">unveil the previously hidden and highly complex interactions between those properties</a>, which can influence a material’s efficiency.</p>
<p>Large-scale applications will require themoelectric materials that are inexpensive, non-toxic and abundant. Lead and tellurium are found in today’s thermoelectric materials, but their cost and negative environmental impact make them good targets for replacement. </p>
<p>Quantum calculations can be applied in a way to search for specific sets of materials using parameters such as scarcity, cost and efficiency. Although those calculations can reveal optimum thermoelectric materials, synthesizing the materials with the desired properties remains a challenge.</p>
<p>A multi-institutional effort involving government-run laboratories and universities in the United States, Canada and Europe has revealed more than <a href="https://doi.org/10.1039/C5TC01440A">500 previously unexplored materials</a> with high predicted thermoelectric efficiency. My colleagues and I are currently investigating the thermoelectric performance of those materials in experiments, and have already discovered new sources of high thermoelectric efficiency.</p>
<p>Those initial results strongly suggest that further quantum computations can pinpoint the most efficient combinations of materials to make clean energy from wasted heat and the avert the catastrophe that looms over our planet.</p><img src="https://counter.theconversation.com/content/173472/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jan-Hendrik Pöhls does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>More than two-thirds of the world’s energy is wasted as heat. Thermoelectric materials can convert unwanted heat into electricity, but finding the best ones has been slow.Jan-Hendrik Pöhls, McCall MacBain Postdoctoral Fellow, Department of Chemistry and Chemical Biology, McMaster UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1578402021-05-02T12:41:31Z2021-05-02T12:41:31ZFrom making wine to managing mine waste, clay is important for many industries<figure><img src="https://images.theconversation.com/files/397445/original/file-20210427-21-1jamobb.jpg?ixlib=rb-1.1.0&rect=0%2C9%2C3008%2C1985&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The unique properties of clays make them suitable for a wide variety of applications.</span> <span class="attribution"><span class="source">(Shutterstock)</span></span></figcaption></figure><p>The discovery and use of clays dates back to <a href="https://ceramics.org/about/what-are-engineered-ceramics-and-glass/brief-history-of-ceramics-and-glass">30,000 years ago</a>, making clays one of the oldest materials used in society. Clays are naturally occurring materials that were first used to make pottery and are now used abundantly in the manufacturing of goods, including ceramics, cosmetics and building materials. Clays also play <a href="http://doi.org/10.1007/s00706-019-02454-y">an important role in the “terroir,” the features a wine develops based on where the grapes are grown</a>.</p>
<p>Clay has unique properties that are useful in industries ranging from manufacturing to construction. But these properties can also pose a challenge in managing mine waste.</p>
<p>Clays and clay minerals are tiny particles with a unique <a href="https://www.srs.fs.usda.gov/pubs/ja/ja_barton002.pdf">plate-like structure less than two microns</a> in size (for comparison, the average thickness of a strand of human hair is about 70 microns). The small size of clay minerals and their distinct structure give them unique properties, and different types of clay minerals can exhibit diverse characteristics. </p>
<h2>Properties of clays</h2>
<p>There are <a href="https://doi.org/10.1080/24749508.2017.1361128">four main groups of clay mineral</a>: kaolinite, illite, vermiculite and smectite. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/397447/original/file-20210427-19-1sscsbp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="An illustration of the molecular structure of kaolinite clay" src="https://images.theconversation.com/files/397447/original/file-20210427-19-1sscsbp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/397447/original/file-20210427-19-1sscsbp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=471&fit=crop&dpr=1 600w, https://images.theconversation.com/files/397447/original/file-20210427-19-1sscsbp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=471&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/397447/original/file-20210427-19-1sscsbp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=471&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/397447/original/file-20210427-19-1sscsbp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=591&fit=crop&dpr=1 754w, https://images.theconversation.com/files/397447/original/file-20210427-19-1sscsbp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=591&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/397447/original/file-20210427-19-1sscsbp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=591&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Clay minerals are classified based on the arrangement of their molecules and layers.</span>
<span class="attribution"><span class="source">(Shutterstock)</span></span>
</figcaption>
</figure>
<p>Smectite clays for example, have the greatest ability to swell, often expanding several times their initial volume. Bentonite clay, a smectite, can <a href="https://doi.org/10.1016/j.enggeo.2011.10.003">swell up to 18 times its initial volume</a> by taking water into its interlayer, the distance between two layers of clays. This property makes it useful as a spill absorbent, but also means that it is very difficult to remove water from clay in dewatering processes, as in the case of mine waste management.</p>
<p>In contrast, kaolin, or china clay, does not swell and has low permeability, making it preferable for <a href="https://doi.org/10.1179/1745823414Y.0000000008">producing porcelain</a> or <a href="https://doi.org/10.1016/0169-1317(91)90015-2">improving the printability of paper</a>. </p>
<p>Clays also develop plasticity when wet, giving them the ability to stretch without breaking or tearing — a critical property for pottery sculpting. The <a href="http://doi.org/10.13140/RG.2.2.10554.70086">drying and firing processes</a> cause the water molecules to escape from between the clay sheets, and irreversibly changing the chemical structure of the clays, turning the piece into a hard and long-lasting pottery piece.</p>
<h2>Clay and wine</h2>
<p>Vineyard owners use their knowledge of clay content in the soil to help them make decisions about planting and irrigation so that they can improve the quality of the wine they produce. The soil composition in vineyards influences the drainage levels and the uptake of minerals and nutrients for the roots. Sandy soils are great for drainage, and clays, which have a net negative charge, help <a href="http://www.soilquality.org.au/factsheets/cation-exchange-capacity">retain positively charged nutrients including calcium, magnesium and potassium</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/397755/original/file-20210429-17-1esa900.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Vineyards with red clay soil" src="https://images.theconversation.com/files/397755/original/file-20210429-17-1esa900.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/397755/original/file-20210429-17-1esa900.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/397755/original/file-20210429-17-1esa900.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/397755/original/file-20210429-17-1esa900.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/397755/original/file-20210429-17-1esa900.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/397755/original/file-20210429-17-1esa900.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/397755/original/file-20210429-17-1esa900.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The composition of the soil and clays that grapes are grown in can affect the taste of the wine. Vineyard owners can use this knowledge to produce specific notes.</span>
<span class="attribution"><span class="source">(Shutterstock)</span></span>
</figcaption>
</figure>
<p>Clays also hold water quite well, which can be helpful in dry climates to keep the soil cooler and wetter. Certain vine varieties produce the best results in a particular soil type. For example, clay soils tend to produce <a href="https://sommelierschoiceawards.com/en/blog/insights-1/soil-types-that-matter-for-grape-growing-164.htm">bold and muscular red wines like sangiovese and merlot</a> and <a href="https://www.winc.com/blog/how-soil-type-affects-your-wine">white wines like chardonnay</a>.</p>
<h2>Clay in mine waste</h2>
<p>While clays can be valuable materials in certain industrial processes, they can also cause problems in mine waste management. For example, <a href="https://www.capp.ca/explore/tailings-ponds/">oilsands tailings</a> — produced from the surface mining of oilsands — consist of a mixture of water, sand, fine particles, clays and residual bitumen. </p>
<p>These tailings are stored in ponds, where the heavier sands settle quickly to the bottom and the fine particles and clays remain suspended. The water-loving nature of clays means that a lot of water is trapped in the tailings, making consolidation and subsequent reclamation very challenging. </p>
<p>As of 2018, there are <a href="https://static.aer.ca/prd/documents/oilsands/2018-State-Fluid-Tailings-Management-Mineable-OilSands.pdf">more than 1.2 trillion litres of fluid tailings</a> accumulated in these ponds in Alberta. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/398129/original/file-20210430-21-e9zkiv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Alternating stripes of bitumen, water, sand and grass at a mine's tailings pond" src="https://images.theconversation.com/files/398129/original/file-20210430-21-e9zkiv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/398129/original/file-20210430-21-e9zkiv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/398129/original/file-20210430-21-e9zkiv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/398129/original/file-20210430-21-e9zkiv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/398129/original/file-20210430-21-e9zkiv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/398129/original/file-20210430-21-e9zkiv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/398129/original/file-20210430-21-e9zkiv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=501&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Bitumen, water, sand and grass at a mine’s tailings pond, where the fine particles and clays gradually settle. Oilsands tailings are waste materials produced from extracting bitumen from the Alberta oilsands.</span>
<span class="attribution"><span class="source">(Shutterstock)</span></span>
</figcaption>
</figure>
<p>This fluid tailings problem is not exclusive to oilsands as all forms of mining — such as copper, potash and diamond — produce tailings. As the <a href="https://www.worldbank.org/en/news/press-release/2020/05/11/mineral-production-to-soar-as-demand-for-clean-energy-increases">global production of minerals and metals continue to rise</a>, so does the production of tailings. </p>
<p>Clay measurement methods will become increasingly important to monitor and optimize tailings management strategies.</p>
<h2>Treatment methods</h2>
<p>Many tailings treatment solutions modify clay properties to accelerate dewatering and consolidation, and so understanding the clays present is critical for any treatment methods to work. </p>
<p>Clays can be characterized based on <a href="https://doi.org/10.1080/24749508.2017.1361128">particle size, mineral type, surface area, cation exchange capacity, plasticity and flow behaviour</a>. In a laboratory setting <a href="https://www.researchgate.net/publication/282662304_DEMYSTIFYING_THE_METHYLENE_BLUE_INDEX">used in the oilsands industry for decades</a>, methylene blue dye can help determine some of these important properties.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/397161/original/file-20210426-21-1xn4rfz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/397161/original/file-20210426-21-1xn4rfz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/397161/original/file-20210426-21-1xn4rfz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/397161/original/file-20210426-21-1xn4rfz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/397161/original/file-20210426-21-1xn4rfz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/397161/original/file-20210426-21-1xn4rfz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/397161/original/file-20210426-21-1xn4rfz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/397161/original/file-20210426-21-1xn4rfz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">NAIT researchers are integrating robotics, sensors and optical systems to automate the methylene blue index laboratory method.</span>
<span class="attribution"><span class="source">(Author provided)</span></span>
</figcaption>
</figure>
<p>The Northern Alberta Institute of Technology and its partners are developing an <a href="https://www.nrcan.gc.ca/science-data/funding-partnerships/funding-opportunities/current-investments/development-line-active-clay-analyzer-canadian-mining-industry/22904">automated clay analyzer</a> based on the <a href="https://www.astm.org/Standards/C837.htm">methylene blue index method</a> that would make it possible for in-field clay measurement. This would optimize treatment processes, translating to cost savings and faster reclamation of the tailings ponds.</p>
<p>From helping to create reclaimable tailings to producing a bottle of quality wine, advances in clay measurement can bring many economic and environmental benefits.</p><img src="https://counter.theconversation.com/content/157840/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jason Ng receives funding from Natural Resources Canada's Clean Growth Program, Natural Sciences and Engineering Research Council of Canada (NSERC) and the Institute for Oil Sands Innovation (IOSI).</span></em></p><p class="fine-print"><em><span>Andrea Sedgwick receives funding from Natural Resources Canada"s Clean Growth Program, Natural Sciences and Engineering Research Council of Canada (NSERC), Alberta Innovates, Alberta Jobs, Economy and Innovation and the Institute for Oil Sands Innovation (IOSI).</span></em></p>Throughout human history, clay has played a role in many different industries. Its unique properties make it suited for a wide applications in widely ranging industries.Jason Ng, Research Associate, Oil Sands Sustainability, Northern Alberta Institute of TechnologyAndrea Sedgwick, Applied Research Chair, Oil Sands Sustainability, Northern Alberta Institute of TechnologyLicensed as Creative Commons – attribution, no derivatives.