tag:theconversation.com,2011:/id/topics/biomimetics-7729/articlesBiomimetics – The Conversation2023-08-17T12:34:06Ztag:theconversation.com,2011:article/2054652023-08-17T12:34:06Z2023-08-17T12:34:06ZMobile robots get a leg up from a more-is-better communications principle<figure><img src="https://images.theconversation.com/files/542418/original/file-20230811-38693-1jf8u.jpg?ixlib=rb-1.1.0&rect=0%2C2%2C799%2C529&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Getting a leg up from mobile robots comes down to getting a bunch of legs.</span> <span class="attribution"><a class="source" href="https://research.gatech.edu/scurrying-centipedes-inspire-many-legged-robots-can-traverse-difficult-landscapes">Georgia Institute of Technology</a></span></figcaption></figure><p>Adding legs to robots that have minimal awareness of the environment around them can help the robots operate more effectively in difficult terrain, my colleagues and I found.</p>
<p>We were inspired by mathematician and engineer Claude Shannon’s <a href="https://www.quantamagazine.org/how-claude-shannons-information-theory-invented-the-future-20201222/">communication theory</a> about how to transmit signals over distance. Instead of spending a huge amount of money to build the perfect wire, Shannon illustrated that it is good enough to use redundancy to reliably convey information over noisy communication channels. We wondered if we could do the same thing for transporting cargo via robots. That is, if we want to transport cargo over “noisy” terrain, say fallen trees and large rocks, in a reasonable amount of time, could we do it by just adding legs to the robot carrying the cargo and do so without sensors and cameras on the robot?</p>
<p>Most mobile robots use inertial sensors to gain an awareness of <a href="https://doi.org/10.3390/designs6010017">how they are moving through space</a>. Our key idea is to forget about inertia and replace it with the simple function of repeatedly making steps. In doing so, our theoretical analysis confirms our hypothesis of reliable and predictable robot locomotion – and hence cargo transport – without additional sensing and control.</p>
<p>To verify our hypothesis, we built robots inspired by centipedes. We discovered that the more legs we added, <a href="https://doi.org/10.1126/science.ade4985">the better the robot could move across uneven surfaces</a> without any additional sensing or control technology. Specifically, we conducted a series of experiments where we built terrain to mimic an inconsistent natural environment. We evaluated the robot locomotion performance by gradually increasing the number of legs in increments of two, beginning with six legs and eventually reaching a total of 16 legs. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/6NhOervars4?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Navigating rough terrain can be as simple as taking it a step at a time, at least if you have a lot of legs.</span></figcaption>
</figure>
<p>As the number of legs increased, we observed that the robot exhibited enhanced agility in traversing the terrain, even in the absence of sensors. To further assess its capabilities, we conducted outdoor tests on real terrain to evaluate its performance in more realistic conditions, where it performed just as well. There is potential to use many-legged robots for agriculture, space exploration and search and rescue.</p>
<h2>Why it matters</h2>
<p>Transporting things – food, fuel, building materials, medical supplies – is essential to modern societies, and effective goods exchange is the cornerstone of commercial activity. For centuries, transporting material on land has required building roads and tracks. However, roads and tracks are not available everywhere. Places such as hilly countryside have had limited access to cargo. Robots might be a way to transport payloads in these regions.</p>
<h2>What other research is being done in this field</h2>
<p>Other researchers have been developing <a href="https://doi.org/10.1017/S0269888919000158">humanoid robots</a> and <a href="https://doi.org/10.1016/j.asej.2020.11.005">robot dogs</a>, which have become increasingly agile in recent years. These robots rely on accurate sensors to know where they are and what is in front of them, and then make decisions on how to navigate. </p>
<p>However, their strong dependence on environmental awareness <a href="https://doi.org/10.1109/ACCESS.2020.2975643">limits them in unpredictable environments</a>. For example, in search-and-rescue tasks, sensors can be damaged and environments can change.</p>
<h2>What’s next</h2>
<p>My colleagues and I have taken valuable insights from our research and applied them to the field of crop farming. We have founded a company that uses these robots to efficiently weed farmland. As we continue to advance this technology, we are focused on refining the robot’s design and functionality. </p>
<p>While we understand the functional aspects of the centipede robot framework, our ongoing efforts are aimed at determining the optimal number of legs required for motion without relying on external sensing. Our goal is to strike a balance between cost-effectiveness and retaining the benefits of the system. Currently, we have shown that 12 is the minimum number of legs for these robots to be effective, but we are still investigating the ideal number.</p>
<p><em>The <a href="https://theconversation.com/us/topics/research-brief-83231">Research Brief</a> is a short take on interesting academic work.</em></p><img src="https://counter.theconversation.com/content/205465/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors has received funding from NSF-Simons Southeast Center for Mathematics and Biology (Simons Foundation SFARI 594594), Georgia Research Alliance (GRA.VL22.B12), Army Research Office (ARO) MURI program, Army Research Office Grant W911NF-11-1-0514 and a Dunn Family Professorship.
The author and his colleagues have one or more pending patent applications related to the research covered in this article.
The author and his colleagues have established a start-up company, Ground Control Robotics, Inc., partially based on this work.</span></em></p>A study found that adding legs does more for you than having a good sense of the ground around you − if you’re a mobile robot.Baxi Chong, Postdoctoral Fellow, Complex Rheology And Biomechanics Lab, Georgia Institute of TechnologyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1082662018-12-06T17:14:21Z2018-12-06T17:14:21ZGeckos walk on water – we filmed them to find out how<figure><img src="https://images.theconversation.com/files/249339/original/file-20181206-128190-1iy9hvu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/colorful-macro-closeup-green-day-gecko-564753997?src=lCXUCR48828mRWAZXzvu_A-1-85">Natalia Van D/Shutterstock</a></span></figcaption></figure><p>Anyone who’s seen a gecko will likely know they can climb walls. But these common lizards can also run across water nearly as fast as they can move on solid ground. Yet while we know how geckos scale smooth vertical surfaces using countless tiny hairs on their feet called setae, how they manage to avoid sinking into the water has been something of a mystery – until now. My colleagues and I <a href="http://www.cell.com/current-biology/fulltext/S0960-9822(18)31469-6">recently completed research</a> that explains how geckos use a combination of techniques to perform this amazing feat.</p>
<p>The ability to walk on water has been recorded in smaller animals such as the <a href="https://www.nature.com/articles/nature01793">water strider</a>, which are light enough to be held up by the water’s surface tension, the force between the water molecules at the surface. Meanwhile, larger animals such as <a href="http://jeb.biologists.org/content/218/8/1235">the grebe</a>, can walk on water because they are powerful enough to slap the surface with their feet as they run. The fast movement pushes down the water beneath the foot, creating a pocket of air around it. The upwards force generated when this pocket is pushed under the water is what keeps the animal briefly suspended on the surface.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/qm1xGfOZJc8?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>But geckos are typically a size that falls in between these two categories. They are too weak to hold themselves up using surface slapping alone and too heavy to leave the water’s surface unbroken. Yet their relative water running speeds approach those of another well-known water running lizard, <a href="https://www.nature.com/articles/380340a0">the basilisk</a> (or “Jesus lizard”), which does rely on the slapping technique.</p>
<p>Initial calculations hinted, and video analysis confirmed, that unlike other species that move at the water’s surface, geckos use a combination of techniques to move faster on top of the water than they can by swimming through it. By analysing videos of geckos moving across the water, we found that their gait was similar to that of the basilisk. Each step involves retracting the foot through the air, slapping the surface, and stroking beneath the water. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/249258/original/file-20181206-128199-nsyi2n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/249258/original/file-20181206-128199-nsyi2n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=216&fit=crop&dpr=1 600w, https://images.theconversation.com/files/249258/original/file-20181206-128199-nsyi2n.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=216&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/249258/original/file-20181206-128199-nsyi2n.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=216&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/249258/original/file-20181206-128199-nsyi2n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=271&fit=crop&dpr=1 754w, https://images.theconversation.com/files/249258/original/file-20181206-128199-nsyi2n.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=271&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/249258/original/file-20181206-128199-nsyi2n.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=271&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">No bridge? No problem.</span>
<span class="attribution"><span class="source">Pauline Jennings</span></span>
</figcaption>
</figure>
<p>But <a href="https://www.ncbi.nlm.nih.gov/pubmed/9320547">unlike basilisks</a>, which aren’t affected by changes in the water’s surface tension, our experiments showed that geckos’ speed and head height were cut by half when we added detergent to the water, reducing the surface tension. This suggests that they are at least partly using the forces between the water molecules to stay above the surface. </p>
<p>We also found that geckos crucially use a combination of hydrostatic force (the upwards push of the water known as buoyancy) and hydrodynamic force (the lift created by movement across the water’s surface like in a surface-skimming motorboat). Together, these forces generate additional lift for the gecko, a condition known as <a href="https://www.globalsecurity.org/military/systems/ship/semi-planing.htm">semi-planing</a>.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/249260/original/file-20181206-128211-1i3yhj4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/249260/original/file-20181206-128211-1i3yhj4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=604&fit=crop&dpr=1 600w, https://images.theconversation.com/files/249260/original/file-20181206-128211-1i3yhj4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=604&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/249260/original/file-20181206-128211-1i3yhj4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=604&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/249260/original/file-20181206-128211-1i3yhj4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=759&fit=crop&dpr=1 754w, https://images.theconversation.com/files/249260/original/file-20181206-128211-1i3yhj4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=759&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/249260/original/file-20181206-128211-1i3yhj4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=759&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The gecko combo.</span>
<span class="attribution"><span class="source">Current Biology</span></span>
</figcaption>
</figure>
<h2>Sting in the tail</h2>
<p>For all the ingenuity of this multi-tasking approach, geckos can only keep their head and torso fully above the water, leaving their tails dragging underneath. Being able to move almost as fast as on land when almost half of your body is underwater and facing more resistance and drag forces is quite a feat – just ask Michael Phelps.</p>
<p>Geckos manage this by using their tail, which has already been shown to help them <a href="https://www.nature.com/articles/s41598-017-11484-7">manoeuvre around obstacles</a>, <a href="http://www.pnas.org/content/105/11/4215">jump</a> and <a href="http://jeb.biologists.org/content/212/5/604">escape predators</a>. Seen from above as it travels across the water, the gecko can resemble a crocodile, moving its body and tail with a wavelike motion to create propulsion to balance the backwards pull of the water.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/wbKVZIhloaM?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>Our research shows that for medium-sized animals to move quickly along the surface of water a complex and clever combination of physical mechanisms is required that previously was thought only to occur in larger and smaller animals. But it could also feed into better designs for animal-inspired robots. </p>
<p>Previous studies on geckos have inspired several such “biomimetic” endeavours, from <a href="https://geckskin.umass.edu/">better adhesives</a> to an agile (and pretty adorable) tailed robot car, aptly named <a href="https://blogs.scientificamerican.com/observations/robot-uses-lizard-tail-to-leap/">Tailbot</a>. Better understanding of how animals travel across complex terrains will hopefully lead to robots that can harness these techniques to move on both land and water with the high performance seen in geckos.</p><img src="https://counter.theconversation.com/content/108266/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jasmine Nirody 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>Understanding geckos’ movements could lead to better robots.Jasmine Nirody, Post-Doctoral Research Fellow in Biophysics, University of OxfordLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1045192018-10-16T10:40:33Z2018-10-16T10:40:33ZEvolution is at work in computers as well as life sciences<figure><img src="https://images.theconversation.com/files/240317/original/file-20181011-154555-l3rbo1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Evolution is not just for living beings.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-vector/evolution-man-into-modern-digital-world-656489833">mmatee/Shutterstock.com</a></span></figcaption></figure><p>Artificial intelligence research has a lot to learn from nature. <a href="https://scholar.google.com/citations?user=9OItN4cAAAAJ&hl=en">My work</a> links biology with computation every day, but recently the rest of the world was reminded of the connection: The <a href="https://www.nobelprize.org/prizes/chemistry/2018/press-release">2018 Nobel Prize in Chemistry</a> went to Frances Arnold together with George Smith and Gregory Winter for developing major breakthroughs that are collectively called “<a href="https://www.vox.com/science-and-health/2018/10/3/17931612/nobel-prize-2018-chemistry-directed-evolution-enzymes-antibodies">directed evolution</a>.” One of its uses is to improve protein functions, making them better catalysts in biofuel production. Another use is entirely outside chemistry – outside even the traditional life sciences.</p>
<p>That might sound surprising, but many research findings have very broad implications. It’s part of why just about every scientist wonders and hopes not only that maybe they would be selected for a Nobel Prize, but, far more likely, that the winner might be someone they know or have worked with. In the <a href="http://mathworld.wolfram.com/ErdosNumber.html">collaborative academic world</a>, this <a href="http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.592.1467&rep=rep1&type=pdf">isn’t terribly uncommon</a>: In 2002, I was studying under a scholar who had studied under one of the three co-winners of that year’s <a href="https://www.nobelprize.org/prizes/medicine/2002/summary/">Nobel Prize in Physiology or Medicine</a>. This year, it happened again – one of the winners has written a couple of papers with a <a href="http://adamilab.blogspot.com/">scholar I have collaborated with</a>.</p>
<p>Beyond satisfying my own vanity, the award reminds me how useful <a href="https://www.businessinsider.com/6-man-made-inventions-that-already-exist-in-nature-biomimicry-2016-5">biological concepts</a> are for engineering problems. The best-known example is probably the invention of Velcro hook-and-loop fasteners, <a href="http://nymag.com/vindicated/2016/11/an-idea-that-stuck-how-george-de-mestral-invented-velcro.html">inspired by burrs that stuck to a man’s pants</a> while he was walking outdoors. In the Nobel laureates’ work, the natural principle at work is evolution – which is also the approach I use to <a href="https://theconversation.com/evolving-our-way-to-artificial-intelligence-54100">develop artificial intelligence</a>. My research is based on the idea that evolution led to general intelligence in biological life forms, so <a href="https://blog.openai.com/evolution-strategies/">that same process</a> could also be used to develop computerized intelligent systems. </p>
<p>When designing AI systems that control virtual cars, for example, you might want safer cars that know how to avoid a wide range of obstacles – other cars, trees, cyclists and guardrails. My approach would be to evaluate the safety performance of several AI systems. The ones that drive most safely are allowed to reproduce – by being copied into a new generation. </p>
<p>Yet just as nature does not make identical copies of parents, genetic algorithms in <a href="https://theconversation.com/teaching-machines-to-teach-themselves-88374">computational evolution</a> let mutations and recombinations create variations in the offspring. Selecting and reproducing the safest drivers in each new generation finds and propagates mutations that improve performance. Over many generations, AI systems get better through the same method nature improves upon itself – and the same way the Nobel laureates made better proteins.</p>
<p>In the effort to understand human intelligence, many researchers are working to reverse-engineer the brain, figuring out how it works at all levels. Complex gene networks control the neurons that form the layers of the neocortex that are sitting on top of a <a href="https://www.patexia.com/feed/high-capacity-highways-in-the-brain-20120620">highway of connections</a>. These interconnections support communications between the different <a href="https://en.wikipedia.org/wiki/Cerebral_cortex">cortical regions</a> that make up most of our cognitive functions. All of this is integrated into the phenomenon of <a href="https://blogs.scientificamerican.com/cross-check/can-integrated-information-theory-explain-consciousness/">consciousness</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/240308/original/file-20181011-154567-1fe6v5g.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/240308/original/file-20181011-154567-1fe6v5g.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/240308/original/file-20181011-154567-1fe6v5g.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=560&fit=crop&dpr=1 600w, https://images.theconversation.com/files/240308/original/file-20181011-154567-1fe6v5g.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=560&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/240308/original/file-20181011-154567-1fe6v5g.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=560&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/240308/original/file-20181011-154567-1fe6v5g.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=704&fit=crop&dpr=1 754w, https://images.theconversation.com/files/240308/original/file-20181011-154567-1fe6v5g.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=704&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/240308/original/file-20181011-154567-1fe6v5g.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=704&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 map of the cerebral cortex.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Blausen_0102_Brain_Motor%26Sensory.png">Bruce Blaus/wikimedia</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Deep learning and neural networks are computer-based approaches that attempt to recreate how the brain works – but even they can only achieve the equivalent activity of a clump of brain cells <a href="http://bionumbers.hms.harvard.edu/bionumber.aspx?id=109245">smaller than a sugar cube</a>. There remains an enormous amount to learn about the brain – and that’s before trying to write the intensely complicated software that can emulate all those biological interactions.</p>
<p>Capitalizing on evolution can make systems that seem lifelike and are inherently as <a href="http://www.evolvingai.org/content/open-ended-evolution">open-ended and innovative</a> as natural evolution is. It is also the key methodology used in <a href="https://mitpress.mit.edu/books/introduction-genetic-algorithms">genetic algorithms</a> and <a href="https://mitpress.mit.edu/books/genetic-programming">genetic programming</a>. The Nobel Prize committee’s recognition highlights a technology that has evolution at its core. That indirectly justifies my own research approach and the idea that <a href="https://www.beacon-center.org">evolution in action</a> is a critical research topic with vast potential.</p><img src="https://counter.theconversation.com/content/104519/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Arend Hintze receives funding from NSF and Strength in Numbers Game Company.</span></em></p>Artificial intelligence research owes a lot to biology and chemistry.Arend Hintze, Assistant Professor of Integrative Biology & Computer Science and Engineering, Michigan State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/650092016-09-12T14:18:54Z2016-09-12T14:18:54ZHere’s how to convince the brain that prosthetic legs are real<figure><img src="https://images.theconversation.com/files/137355/original/image-20160912-3807-1w92mwl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Forgetting limitations</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>The carbon fibre legs or “blades” used by lower limb amputee runners have arguably become one of the most iconic symbols of the Paralympic Games. Although different lower-limb sports prostheses are used for <a href="https://theconversation.com/forget-about-the-olympics-its-the-paralympics-where-the-true-super-humans-perform-62860">running, jumping and other activities</a>, they share a single common aim: they are designed to help Paralympians run faster, jump higher or further <a href="http://www.scientificamerican.com/article/blade-runners-do-high-tech-prostheses-give-runners-an-unfair-advantage/">than other competitors</a>. Form follows function. </p>
<p>For those who have prostheses for more everyday uses, however, their replacement limbs need to be able adapt to different scenarios and perform a variety of functions, not just excel in one discipline – just like an actual leg. So how can we make prostheses feel more like the real thing rather than a specialist tool? </p>
<p>Whereas modern running blades have a distinctive hook shape, one of the most promising engineering approaches for everyday prostheses is to closely model the biological design of a leg, ankle and foot. This approach is referred to as “<a href="http://rsta.royalsocietypublishing.org/content/367/1893/1445">biomimicity</a>”.</p>
<p>A “passive” ankle-foot prosthesis generally uses elastic like a spring to replicate the behaviour of the Achilles tendon, storing elastic energy and releasing it before ankle push-off. “Active” prostheses additionally use an actuator or motor to make up for the power previously provided by the calf muscle <a href="https://www.youtube.com/watch?v=RJrYcPNLhKo&feature=youtu.be">at every step</a>. Such prostheses have been shown to help users <a href="http://rspb.royalsocietypublishing.org/content/279/1728/457.long">walk more like a non-amputee</a> and improve symmetry between the biological and the artificial limb. At the moment, this mainly applies to walking overground at steady speeds rather than activities such as climbing stairs.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/137354/original/image-20160912-3799-1r4cmhr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/137354/original/image-20160912-3799-1r4cmhr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/137354/original/image-20160912-3799-1r4cmhr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/137354/original/image-20160912-3799-1r4cmhr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/137354/original/image-20160912-3799-1r4cmhr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/137354/original/image-20160912-3799-1r4cmhr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/137354/original/image-20160912-3799-1r4cmhr.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">Maximum comfort.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>Simple design, advanced technology</h2>
<p>Other ways to make a prosthesis more like a biological leg and improve the user’s comfort are more simple. They also illustrate how important it is to involve the amputee in the design process. One user of the most advanced bionic ankle currently available told me its greatest feature was not that it provided a powered push-off or that it allowed them to walk more like a non-amputee. Instead it was that the <a href="http://www.ottobock.co.uk/prosthetics/lower_limb_prosthetics/prosthetic-product-systems/triton-smart-ankle/">foot dropped flat</a> <a href="http://www.bionxmed.com/patients/the-biom-advantage/">on the ground</a> when sitting with an outstretched leg, rather than sticking up awkwardly at a 90-degree angle (as is the case for the majority of prosthetic feet).</p>
<p>Another issue is how the prosthesis is controlled. Active prostheses now include <a href="https://hackaday.io/project/5765-flexsea-wearable-robotics-toolkit">on-board computers</a> to control the motors and emulate human walking. Prostheses are effectively becoming more and more like wearable robots. What’s more, we can even use interfaces that read signals from the brain <a href="http://www.nejm.org/doi/full/10.1056/NEJMoa1300126#t=article">or muscles</a> so that the user can operate the prosthesis like a real leg just by thinking and <a href="http://ieeexplore.ieee.org/document/6943925/?arnumber=6943925">moving in their normal way</a>. The next step being trialled is the use of implantable electrodes that send signals to the brain to give the user tactile feedback so they can <a href="http://stm.sciencemag.org/content/6/222/222ra19.full">feel the contact on the prosthesis as if it were their biological limb</a>, closing the human-machine loop.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/Ebd_Yc0oDZI?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>These technological and scientific advances connect the amputee more intimately with their prosthetic limb, meaning we can now focus more on how the prosthesis is embodied. In other words, to what extent does the prosthetic limb feel like part of the biological body? Does your brain treat it as such?</p>
<p>We have a good understanding of how our body is mapped in our brain. Both our motor cortex – the movement control centre, if you like – and the somatosensory cortex where we process a wide range of touch sensations are <a href="http://brain.oxfordjournals.org/content/60/4/389">organised somatotopically</a>. This means each area of our body corresponds to a specific area of the primary motor and sensory cortices. Importantly, this mapping does not disappear after the loss of a limb.</p>
<p>This means we have an opportunity to connect prostheses, through muscles and peripheral nerves, to the parts of the brain that would have controlled and sensed the biological body part. But it may also allow us to <a href="http://www.sciencedirect.com/science/article/pii/S1571064516000129">measure embodiment</a>, how successfully the brain accepts the prosthesis as part of the body.</p>
<p>Ultimately this line of research, bringing together cognitive neuroscience and biomedical engineering, is not only important for designing better prostheses. It is a unique window for understanding how our brain creates and maintains the image of our bodies – mechanisms that apply equally to amputees and <a href="http://www.oliversacks.com/books-by-oliver-sacks/leg-stand/">non-amputees</a>.</p><img src="https://counter.theconversation.com/content/65009/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Oliver Alan Kannape received funding from the Swiss National Science Foundation and the US Department of Defense while working at the Massachusetts Institute of Technology. </span></em></p>The best prosthetics feel more like the real thing.Oliver Alan Kannape, Assistant Lecturer, University of Central LancashireLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/646192016-09-01T08:16:11Z2016-09-01T08:16:11ZInsects are helping us develop the future of hearing aids<figure><img src="https://images.theconversation.com/files/136119/original/image-20160831-30794-zvwk2z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>The human ear is a miracle of mechanical evolution. It allows us to hear an astonishing range of sounds and to communicate and navigate in the world. It’s also easy to damage and difficult to repair. Hearing aids are still large, uncomfortable and as yet unable to deliver the rich and wonderful sounds we take for granted. Yet there may be a new way for us to replace damaged hearing from an unlikely source – the insect world.</p>
<p>Spend a summer in the countryside in a warm climate and you’ll likely hear crickets chirping, males of the species “singing” in an attempt to attract a female. What’s surprising is how small the creatures are given the very high sound levels they produce. Could studying crickets allow us to learn something about how to design a small speaker that is also loud, just as you need for a hearing aid?</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/e2KVj2vVxUs?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>Currently my colleagues and I are researching exactly this. Crickets create sound by rubbing their wings together. The <a href="http://jeb.biologists.org/content/214/12/2105">secret to their loud calls</a> is that their wings are corrugated in specific patterns which makes them very stiff, which in turn makes them very loud when they are rubbed together. Using laser vibration systems and advanced computer modelling simulations (more often used to study aerodynamics), we can <a href="http://www.pnas.org/content/109/22/E1444.short">replicate this idea</a> by tailoring the stiffness of a speaker surface. This creates a simple and efficient way to make tiny speakers very loud indeed. </p>
<p>Insect inspiration doesn’t stop with small speakers, however. Hearing aids have traditionally been designed to operate <a href="https://www.nidcd.nih.gov/health/hearing-aids">in distinct stages</a>. Sound signals are picked up by a microphone and then electrically amplified. Unwanted sounds are filtered out using digital processors and finally a speaker delivers high intensity sound into the ear canal. In each of these processes we may be able to learn from insects.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/136124/original/image-20160831-30804-uv2lam.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/136124/original/image-20160831-30804-uv2lam.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=519&fit=crop&dpr=1 600w, https://images.theconversation.com/files/136124/original/image-20160831-30804-uv2lam.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=519&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/136124/original/image-20160831-30804-uv2lam.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=519&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/136124/original/image-20160831-30804-uv2lam.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=652&fit=crop&dpr=1 754w, https://images.theconversation.com/files/136124/original/image-20160831-30804-uv2lam.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=652&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/136124/original/image-20160831-30804-uv2lam.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=652&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Tsunami-like waves in a locust’s ear.</span>
<span class="attribution"><span class="source">Rob Malkin</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Among the best studied insects in bio-acoustics is the locust, which has two large “tympanal” membranes <a href="http://link.springer.com/article/10.1007%2FBF01245156">used for hearing</a> on either side of its chest. These membranes vibrate with sound and transfer the resulting signals to the nervous system, much a like a human ear drum. <a href="http://rsif.royalsocietypublishing.org/content/11/90/20130857">Recently we observed</a> this membrane doing more than just vibrating up and down. Upon careful dissection, we found that it had a regular variation in thickness. While this may not sound particularly interesting at first, when we played sound to it we were amazed.</p>
<p>It produced a tsunami-like vibration with the peak of the wave directly at the location of the nerve cells. In effect, this simple variation in thickness allowed for huge amplifications of the sound energy. The process of amplification in mammals is achieved with fragile middle ear bones, something locusts are achieving by simply varying the thickness of their ear drum. So we may be able to similarly design microphones with inbuilt passive amplification based on this idea. </p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/136123/original/image-20160831-30772-1r6t6r3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/136123/original/image-20160831-30772-1r6t6r3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=800&fit=crop&dpr=1 600w, https://images.theconversation.com/files/136123/original/image-20160831-30772-1r6t6r3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=800&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/136123/original/image-20160831-30772-1r6t6r3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=800&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/136123/original/image-20160831-30772-1r6t6r3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1005&fit=crop&dpr=1 754w, https://images.theconversation.com/files/136123/original/image-20160831-30772-1r6t6r3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1005&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/136123/original/image-20160831-30772-1r6t6r3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1005&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Mosquito microphone.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>Interestingly, some insects are even making us question what exactly a microphone can be. Mosquitoes and fruit flies, as examples, have <a href="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1088611/">tiny antennae</a> on their heads which are microscopic in size yet are very sensitive to sound. While research into these features is tentative, it could direct us in unexplored directions of microphone design. </p>
<p>The process of filtering incoming sounds with a hearing aid requires quite sophisticated electronics, which directly impact the device’s size and battery life. Here again the locust may help. Along with amplifying the sound waves, the tympanal membranes also filter out a range of frequencies. This is most likely due to the material the membrane is made from.</p>
<p>My colleague, Professor Daniel Robert, <a href="http://science.sciencemag.org/content/338/6109/968">recently found</a> a South American species of katydid or bush cricket that may well perform the same task. The katydid has a tiny structure less than a millimetre in size in each of its forelegs that is capable of separating different frequencies into location specific vibrations, very similar in function to the human cochlea. If we could somehow encompass this mechanical frequency separation into the microphone itself, we may be able to harness its automatic filtering properties.</p>
<p>Biology, medicine and engineering have traditionally been quite separate disciplines. But by combining them, as we have in these projects, we can develop new engineering solutions based on discoveries that may have been made many years ago. So while bio-inspired hearing aids may not be about to arrive on the shelves, this innovative new field of study could find more and more ways to address the needs of people with hearing loss. And there’s plenty more inspiration that could come from our miniature mechanical specialists, the insects.</p><img src="https://counter.theconversation.com/content/64619/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Rob Malkin has been awarded the Isambard Kingdom Brunel Award Lecture for engineering, technology and industry at the 2016 British Science Festival by the British Science Association.</span></em></p>Studying the way insects hear and make their own sounds is inspiring new hearing technology.Rob Malkin, Senior Research Associate, University of BristolLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/627592016-08-09T22:57:52Z2016-08-09T22:57:52ZBiohybrid robots built from living tissue start to take shape<figure><img src="https://images.theconversation.com/files/133577/original/image-20160809-11006-q4ewto.JPG?ixlib=rb-1.1.0&rect=737%2C419%2C3825%2C2545&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Biohybrid sea slug, reporting for duty.</span> <span class="attribution"><span class="source">Dr. Andrew Horchler</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><p>Think of a traditional robot and you probably imagine something made from metal and plastic. Such “nuts-and-bolts” robots are made of hard materials. As robots take on more roles beyond the lab, such rigid systems can present safety risks to the people they interact with. For example, if an industrial robot swings into a person, there is the risk of bruises or bone damage. </p>
<p>Researchers are increasingly looking for solutions to make robots softer or more compliant – less like rigid machines, more like animals. With traditional actuators – such as motors – this can mean using <a href="http://dx.doi.org/10.1109/BIOROB.2006.1639201">air muscles</a> or adding springs in parallel with motors. For example, on a <a href="http://biorobots.case.edu/projects/whegs/usar-whegs/">Whegs robot</a>, having a spring between a motor and the wheel leg (Wheg) means that if the robot runs into something (like a person), the spring absorbs some of the energy so the person isn’t hurt. The bumper on a Roomba vacuuming robot is another example; it’s spring-loaded so the Roomba doesn’t damage the things it bumps into.</p>
<p>But there’s a growing area of research that’s taking a different approach. By combining robotics with tissue engineering, we’re starting to build robots powered by living muscle tissue or cells. These devices can be stimulated electrically or with light to make the cells contract to bend their skeletons, causing the robot to swim or crawl. The resulting biobots can move around and are soft like animals. They’re safer around people and typically less harmful to the environment they work in than a traditional robot might be. And since, like animals, they need nutrients to power their muscles, not batteries, biohybrid robots tend to be lighter too.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/133575/original/image-20160809-18023-1myrrq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/133575/original/image-20160809-18023-1myrrq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/133575/original/image-20160809-18023-1myrrq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=431&fit=crop&dpr=1 600w, https://images.theconversation.com/files/133575/original/image-20160809-18023-1myrrq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=431&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/133575/original/image-20160809-18023-1myrrq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=431&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/133575/original/image-20160809-18023-1myrrq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=541&fit=crop&dpr=1 754w, https://images.theconversation.com/files/133575/original/image-20160809-18023-1myrrq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=541&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/133575/original/image-20160809-18023-1myrrq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=541&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Tissue-engineered biobots on titanium molds.</span>
<span class="attribution"><span class="source">Karaghen Hudson and Sung-Jin Park</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Building a biobot</h2>
<p>Researchers fabricate biobots by growing living cells, usually from heart or skeletal muscle of rats or chickens, on scaffolds that are nontoxic to the cells. If the substrate is a polymer, the device created is a biohybrid robot – a hybrid between natural and human-made materials.</p>
<p>If you just place cells on a molded skeleton without any guidance, they wind up in random orientations. That means when researchers apply electricity to make them move, the cells’ contraction forces will be applied in all directions, making the device inefficient at best.</p>
<p>So to better harness the cells’ power, researchers turn to micropatterning. We stamp or print microscale lines on the skeleton made of substances that the cells prefer to attach to. These lines guide the cells so that as they grow, they align along the printed pattern. With the cells all lined up, researchers can direct how their contraction force is applied to the substrate. So rather than just a mess of firing cells, they can all work in unison to move a leg or fin of the device.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/133573/original/image-20160809-5131-12xdbn0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/133573/original/image-20160809-5131-12xdbn0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/133573/original/image-20160809-5131-12xdbn0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=398&fit=crop&dpr=1 600w, https://images.theconversation.com/files/133573/original/image-20160809-5131-12xdbn0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=398&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/133573/original/image-20160809-5131-12xdbn0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=398&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/133573/original/image-20160809-5131-12xdbn0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/133573/original/image-20160809-5131-12xdbn0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/133573/original/image-20160809-5131-12xdbn0.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">Tissue-engineered soft robotic ray that’s controlled with light.</span>
<span class="attribution"><span class="source">Karaghen Hudson and Michael Rosnach</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Biohybrid robots inspired by animals</h2>
<p>Beyond a wide array of biohybrid robots, researchers have even created some completely organic robots using natural materials, like the collagen in skin, rather than polymers for the body of the device. <a href="http://dx.doi.org/10.1088/1748-3190/11/3/036012">Some can crawl or swim</a> when stimulated by an electric field. Some take inspiration from <a href="http://dx.doi.org/10.1021/ac0507800">medical tissue engineering techniques</a> and use <a href="http://dx.doi.org/10.1038/srep00857">long rectangular arms</a> (or cantilevers) to pull themselves forward.</p>
<p>Others have taken their cues from nature, creating biologically inspired biohybrids. For example, a group led by researchers at California Institute of Technology developed a biohybrid robot <a href="http://dx.doi.org/10.1038/nbt.2269">inspired by jellyfish</a>. This device, which they call a medusoid, has arms arranged in a circle. Each arm is micropatterned with protein lines so that cells grow in patterns similar to the muscles in a living jellyfish. When the cells contract, the arms bend inwards, propelling the biohybrid robot forward in nutrient-rich liquid.</p>
<p>More recently, researchers have demonstrated how to steer their biohybrid creations. A group at Harvard used genetically modified heart cells to make a <a href="http://dx.doi.org/10.1126/science.aaf4292">biologically inspired manta ray-shaped robot</a> swim. The heart cells were altered to contract in response to specific frequencies of light – one side of the ray had cells that would respond to one frequency, the other side’s cells responded to another.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/-D_XrRo0h20?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>When the researchers shone light on the front of the robot, the cells there contracted and sent electrical signals to the cells further along the manta ray’s body. The contraction would propagate down the robot’s body, moving the device forward. The researchers could make the robot turn to the right or left by varying the frequency of the light they used. If they shone more light of the frequency the cells on one side would respond to, the contractions on that side of the manta ray would be stronger, allowing the researchers to steer the robot’s movement.</p>
<h2>Toughening up the biobots</h2>
<p>While exciting developments have been made in the field of biohybrid robotics, there’s still significant work to be done to get the devices out of the lab. Devices currently have limited lifespans and low force outputs, limiting their speed and ability to complete tasks. Robots made from mammalian or avian cells are very picky about their environmental conditions. For example, the ambient temperature must be near biological body temperature and the cells require regular feeding with nutrient-rich liquid. One possible remedy is to package the devices so that the muscle is protected from the external environment and constantly bathed in nutrients.</p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/133582/original/image-20160809-5131-n8kji7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/133582/original/image-20160809-5131-n8kji7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/133582/original/image-20160809-5131-n8kji7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=593&fit=crop&dpr=1 600w, https://images.theconversation.com/files/133582/original/image-20160809-5131-n8kji7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=593&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/133582/original/image-20160809-5131-n8kji7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=593&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/133582/original/image-20160809-5131-n8kji7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=745&fit=crop&dpr=1 754w, https://images.theconversation.com/files/133582/original/image-20160809-5131-n8kji7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=745&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/133582/original/image-20160809-5131-n8kji7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=745&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 sea slug <em>Aplysia californica</em>.</span>
<span class="attribution"><span class="source">Jeff Gill</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Another option is to use more robust cells as actuators. Here at Case Western Reserve University, we’ve recently begun to investigate this possibility by turning to the hardy marine sea slug <em>Aplysia californica</em>. Since <em>A. californica</em> lives in the intertidal region, it can experience big changes in temperature and environmental salinity over the course of a day. When the tide goes out, the sea slugs can get trapped in tide pools. As the sun beats down, water can evaporate and the temperature will rise. Conversely in the event of rain, the saltiness of the surrounding water can decrease. When the tide eventually comes in, the sea slugs are freed from the tidal pools. Sea slugs have evolved very hardy cells to endure this changeable habitat. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/133579/original/image-20160809-18037-1eyplpd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/133579/original/image-20160809-18037-1eyplpd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/133579/original/image-20160809-18037-1eyplpd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/133579/original/image-20160809-18037-1eyplpd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/133579/original/image-20160809-18037-1eyplpd.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/133579/original/image-20160809-18037-1eyplpd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/133579/original/image-20160809-18037-1eyplpd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/133579/original/image-20160809-18037-1eyplpd.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">Sea turtle-inspired biohybrid robot, powered by muscle from the sea slug.</span>
<span class="attribution"><span class="source">Dr. Andrew Horchler</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>We’ve been able to <a href="http://dx.doi.org/10.1007/978-3-319-42417-0_33">use <em>Aplysia</em> tissue to actuate a biohybrid robot</a>, suggesting that we can manufacture tougher biobots using these resilient tissues. The devices are large enough to carry a small payload – approximately 1.5 inches long and one inch wide.</p>
<p>A further challenge in developing biobots is that currently the devices lack any sort of on-board control system. Instead, engineers control them via external electrical fields or light. In order to develop completely autonomous biohybrid devices, we’ll need controllers that interface directly with the muscle and provide sensory inputs to the biohybrid robot itself. One possibility is to use neurons or clusters of neurons called ganglia as organic controllers.</p>
<p>That’s another reason we’re excited about using <em>Aplysia</em> in our lab. This sea slug has been a model system for <a href="https://www.routledge.com/Model-Systems-and-the-Neurobiology-of-Associative-Learning-A-Festschrift/Steinmetz-Gluck-Solomon/p/book/9780415650229">neurobiology research for decades</a>. A great deal is already known about the relationships between its neural system and its muscles – opening the possibility that we could use its neurons as organic controllers that could tell the robot which way to move and help it perform tasks, such as finding toxins or following a light.</p>
<p>While the field is still in its infancy, researchers envision many intriguing applications for biohybrid robots. For example, our tiny devices using slug tissue could be released as swarms into water supplies or the ocean to seek out toxins or leaking pipes. Due to the biocompatibility of the devices, if they break down or are eaten by wildlife these environmental sensors theoretically wouldn’t pose the same threat to the environment traditional nuts-and-bolts robots would.</p>
<p>One day, devices could be fabricated from human cells and used for medical applications. Biobots could provide targeted drug delivery, clean up clots or serve as compliant actuatable stents. By using organic substrates rather than polymers, such stents could be used to strengthen weak blood vessels to prevent aneurysms – and over time the device would be remodeled and integrated into the body. Beyond the small-scale biohybrid robots currently being developed, ongoing research in tissue engineering, such as attempts to grow vascular systems, may open the possibility of growing large-scale robots actuated by muscle.</p><img src="https://counter.theconversation.com/content/62759/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Victoria Webster receives funding from the National Science Foundation and the National Institute of Health.</span></em></p>To do the jobs “nuts-and-bolts” robots aren’t good at, engineers are creating soft living machines powered by muscle cells.Victoria Webster-Wood, Ph.D. Candidate in Mechanical and Aerospace Engineering, Case Western Reserve UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/568772016-03-29T15:01:14Z2016-03-29T15:01:14ZWhat can fish mouths teach us about engineering clog-free filters?<figure><img src="https://images.theconversation.com/files/116536/original/image-20160328-17844-f3fapm.jpg?ixlib=rb-1.1.0&rect=1046%2C404%2C3241%2C2516&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Filter-feeding fish have had 150 million years to improve filtration.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/usfwsmtnprairie/9546645557/">Rob Holm / USFWS</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>Filter-feeding fish accomplish a feat that human technologies cannot: species including goldfish, menhaden and basking sharks filter tiny algal cells or shrimp-like prey from huge volumes of water without clogging their oral filters.</p>
<p>Since fish have been filtering particles for more than 150 million years longer than human beings, we suspected fish may have evolved filter designs that use unknown processes to remain unclogged. So we decided to investigate.</p>
<p>Our research, <a href="http://nature.com/articles/doi:10.1038/ncomms11092">recently published in <em>Nature Communications</em></a>, combines approaches from biomechanics, medicine and ecology to explore how these fish retain and transport prey inside their mouths. Our goal is to provide ideas and data that could improve aquaculture, conservation and industrial filtration.</p>
<h2>Crossflow filtration works for fish and industry</h2>
<p>Until 15 years ago, we thought that most filter-feeding fish used oral structures called gill rakers in the same way that we use coffee filters or spaghetti strainers. These so-called dead-end sieves force water to pass straight through the pores of the mesh. But dead-end sieves always clog as particles accumulate over time to cover the filter surface.</p>
<p>The water flows right through a colander and leaves the spaghetti trapped on the mesh, but a fish needs to move the food from the gill raker filter to the back of its mouth for swallowing. Dead-end sieves would cause problems for fish, since their gill rakers would clog and fish don’t have a tongue to move food particles off the gill rakers. So we knew they must be using some other filtering technique.</p>
<p>By putting a biomedical endoscope inside the mouths of feeding fish, <a href="http://doi.org/10.1038/35086574">colleagues and I discovered in 2001</a> that several common fish species use crossflow filtration instead of trapping particles directly on a dead-end sieve.</p>
<p>During crossflow filtration, small secondary streams of fluid pass through each filter pore – perpendicular to the filter surface, like in dead-end filtration. But the main stream of fluid – the “crossflow” – is directed to travel across (parallel to) the filter surface, lifting particles off the filter and preventing the pores from clogging with particles.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/116557/original/image-20160329-17835-zbfkb9.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/116557/original/image-20160329-17835-zbfkb9.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/116557/original/image-20160329-17835-zbfkb9.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=170&fit=crop&dpr=1 600w, https://images.theconversation.com/files/116557/original/image-20160329-17835-zbfkb9.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=170&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/116557/original/image-20160329-17835-zbfkb9.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=170&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/116557/original/image-20160329-17835-zbfkb9.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=213&fit=crop&dpr=1 754w, https://images.theconversation.com/files/116557/original/image-20160329-17835-zbfkb9.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=213&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/116557/original/image-20160329-17835-zbfkb9.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=213&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 tilapia illustrating the current model of crossflow filtration, from Sanderson et al., doi: 10.1038/ncomms11092. The mainstream flow (MF) enters from the right and passes across the gill rakers (GR) that are attached to the branchial arches (BA). The mainstream flow carries concentrated particles to the back of the mouth for swallowing. The smaller secondary flows (the filtrate, Fi) pass through the pores of the gill raker filter.</span>
<span class="attribution"><span class="source">Virginia Greene, virginiagreeneillustration.com</span>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span>
</figcaption>
</figure>
<p>Through the endoscope, we could see that the main flow of water heading toward the back of the mouth was transporting concentrated particles parallel to the gill raker filter. Less forceful streams of particle-free water exited between the gill rakers. All of these fluid dynamics are caused by the interaction of the water with the physical structures in the fish’s mouth.</p>
<p>We hadn’t expected to see crossflow filtration in fish, though this mechanism had been independently developed by industry a few decades earlier. Crossflow filtration avoids clogging and is often used to filter wastewater, pharmaceuticals, dairy foods and beverages such as beer and fruit juices.</p>
<p>Unfortunately, even <a href="https://en.wikipedia.org/wiki/Membrane_fouling">industrial crossflow filters still clog eventually</a>. Over time, as water exits through the filter pores, it deposits some particles on the filter. The filters must then be backflushed or cleaned with chemicals, causing a major operating expense.</p>
<p>So we turned again to fish, to see whether millions of years of evolution might have come up with unique crossflow filter designs.</p>
<h2>Biomimetic designs from fish mouths</h2>
<p>We started our study by examining basic structures inside fish mouths, familiar to fishermen and aquarium hobbyists. Fish gill rakers – the “feeding filters” – are attached to the branchial arches. These arches are bone or cartilage “ribs” inside the mouth that also support the bright red gills for gas exchange. The arches are typically positioned one after another from the front of the mouth back toward the esophagus, where food is swallowed. Scientists hadn’t previously considered the effects these branchial arches could have on patterns of water flow.</p>
<p>For our latest research, we made our own filters by using computer-aided design (CAD) software and 3D printing to create cone-shaped plastic models of fish mouths. We covered the branchial arch “ribs” with a fine nylon mesh.</p>
<p>We based our physical models on paddlefish and basking sharks because their branchial arches form a series of tall ribs that are separated by deep grooves. In our models, each rib served as a <a href="https://www.youtube.com/watch?v=JP94PR9vE7g">backward-facing step</a> that interacted with the crossflow of water traveling over the step.</p>
<p>Almost anywhere that water flows over a backward-facing step, a vortex is created automatically. For this reason, the closely-spaced tall ribs (“<em>d</em>-type ribs”) in these fish mouths aren’t often used by engineers because of the disruptive vortices that form continuously in the grooves between the ribs.</p>
<p>We designed many models with different versions of these backward-facing steps to test the effects of varying characteristics like height and distance between the steps. Interestingly, designs for some microfluidics devices that are used in labs for cell sorting have similar rib-like structures.</p>
<p>Both paddlefish and basking sharks are ram filter feeders that <a href="https://www.youtube.com/watch?v=7Y5c9l4Eev8">swim forward with a completely open mouth to capture prey</a>. To simulate this kind of feeding, my three undergraduate student coauthors, Erin Roberts, Jillian Lineburg and Hannah Brooks, and I conducted experiments in a flow tank. We submerged our stationary models in a constant stream of water inside the tank. The models “fed” on particles as we adjusted the speed of the water in the flow tank and added particles of different sizes, shapes and densities to the water.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/116558/original/image-20160329-17859-bmyuik.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/116558/original/image-20160329-17859-bmyuik.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/116558/original/image-20160329-17859-bmyuik.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=183&fit=crop&dpr=1 600w, https://images.theconversation.com/files/116558/original/image-20160329-17859-bmyuik.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=183&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/116558/original/image-20160329-17859-bmyuik.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=183&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/116558/original/image-20160329-17859-bmyuik.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=231&fit=crop&dpr=1 754w, https://images.theconversation.com/files/116558/original/image-20160329-17859-bmyuik.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=231&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/116558/original/image-20160329-17859-bmyuik.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=231&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 paddlefish illustrating the new vortical cross-step filtration model, from Sanderson et al., doi: 10.1038/ncomms11092. The mainstream flow (MF) enters from the right and interacts with the series of backward-facing steps that are formed by the branchial arches (BA), causing vortical flow (Vo). The vortex interacts with the gill rakers (GR) to concentrate particles for transport towards the back of the mouth to be swallowed.</span>
<span class="attribution"><span class="source">Virginia Greene, virginiagreeneillustration.com</span>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span>
</figcaption>
</figure>
<h2>Unique vortical cross-step filtration in fish</h2>
<p>Like the spinning of a mini-tornado, water passed over the backward-facing steps inside our models and formed a distinct vortex in the groove between each pair of ribs. We designed accessory structures to control the movement of the vortices by creating regions of the model where the flow couldn’t escape easily. High shear rates around the vortices scoured particles off the mesh, preventing clogging.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/116532/original/image-20160328-17862-1jfs3q7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/116532/original/image-20160328-17862-1jfs3q7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/116532/original/image-20160328-17862-1jfs3q7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/116532/original/image-20160328-17862-1jfs3q7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/116532/original/image-20160328-17862-1jfs3q7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/116532/original/image-20160328-17862-1jfs3q7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/116532/original/image-20160328-17862-1jfs3q7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/116532/original/image-20160328-17862-1jfs3q7.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">Green dye helps visualize the vortices generated in model paddlefish and basking shark mouths.</span>
<span class="attribution"><span class="source">S. Laurie Sanderson</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>We manipulated the vortices to carry particles to the floor of the models, showing that fish could be using this highly adaptable filtration system like a “hydrodynamic tongue” to move particles inside their mouths.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/l03n9gVbkrc?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">We manipulated the vortices in our models to transport concentrated particles along the vortex axis, downstream from each backward-facing step. The vortices lifted particles from the mesh and carried them toward the floor of the model.</span></figcaption>
</figure>
<p>Small preserved paddlefish from an aquaculture company, placed in the flow tank in filter-feeding position, also formed vortices that concentrated particles inside the mouth. This suggests that we’ve correctly identified and modeled structures that are important for generating vortices inside real fish mouths.</p>
<p>This new filtration method, which we term “vortical cross-step filtration,” is effective even when the mesh is damaged or missing from a large portion of the models. Just like fish can continue to feed even when their gill rakers are still growing or are torn, our models can capture particles even when there are large holes in the mesh.</p>
<p>Although we’d identified vortices as a potential mechanism for fish filtration as early as 2001, data on particle capture by vortical flow in fish mouths haven’t been published previously.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/1T7MXCxbatM?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Rhodamine dye traces the path of a vortex that forms downstream from a backward-facing step. The step mimics a branchial arch inside a fish’s mouth.</span></figcaption>
</figure>
<h2>The future of cross-step filtration</h2>
<p>Our biomimetic models of paddlefish and basking shark mouths use novel arrangements of engineering structures that harness vortical flow to retain and transport tiny food particles. Cross-step filtration could also apply to filter-feeding ducks, baleen whales and the gill rakers of filter-feeding fish such as <a href="http://www.sciencefriday.com/videos/no-strain-no-gain-filter-feeding-mantas-2/">manta rays</a>.</p>
<p>Understanding these vortices in fish opens new research directions for engineering improved filters with less clogging, as well as the rapid separation of cells for biomedical tests.</p><img src="https://counter.theconversation.com/content/56877/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>S.Laurie Sanderson is the inventor on U.S. and international patent applications filed by the College of William & Mary (provisional filing 02/2014; nonprovisional filing 02/2015; 14/619,377; PCT/US15/15419). This research on filter-feeding fish was funded in part by the National Science Foundation (NSF Grant IBN-0131293 to S.L.S.).</span></em></p>Even the best engineered filters get clogged eventually. Fish mouths have evolved structures that create unique fluid dynamics patterns that solve that problem.S. Laurie Sanderson, Professor of Biology, William & MaryLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/504452015-11-11T10:46:33Z2015-11-11T10:46:33ZBody hair helps animals stay clean – and could inspire self-cleaning technologies<figure><img src="https://images.theconversation.com/files/101482/original/image-20151110-21220-1g17w17.jpg?ixlib=rb-1.1.0&rect=478%2C0%2C1568%2C1084&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Hair as helpers in the quest for cleanliness.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/stratman2/8568109612">stratman²</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span></figcaption></figure><p>Watch a fly land on the kitchen table, and the first thing it does is clean itself, very, very carefully. Although we can’t see it, the animal’s surface is covered with dust, pollen and even insidious mites that could burrow into its body if not removed.</p>
<p>Staying clean can be a matter of life and death. All animals, including us human beings, take cleaning just as seriously. <a href="http://www.bls.gov/news.release/pdf/atus.pdf">Each year</a>, we spend an entire day bathing, and another two weeks cleaning our houses. Cleaning may be as fundamental to life as eating, breathing and mating.</p>
<p>Yet somehow, cleaning has gotten little attention.</p>
<p>In our new <a href="http://dx.doi.org/10.1242/jeb.103937">review article</a> in the Journal of Experimental Biology, we discuss how cleaning happens in nature and whether animals indeed have principles for getting clean. We looked at microscope images to count the number and sizes of hairs across hundreds of animals. We read nearly a hundred articles on <a href="http://dx.doi.org/10.1098/rsif.2012.0429">cleaning in nature</a>, trying to put numbers onto the cleaning process.</p>
<p>Extrapolating principles is an important step for science, and even more necessary for engineering. Learning better ways to clean will allow us not just to understand the humble fly, but also to build new kinds of devices that stay clean longer.</p>
<h2>Hair vastly amplifies a body’s surface area</h2>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/101480/original/image-20151110-21201-1drjkbi.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/101480/original/image-20151110-21201-1drjkbi.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/101480/original/image-20151110-21201-1drjkbi.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=638&fit=crop&dpr=1 600w, https://images.theconversation.com/files/101480/original/image-20151110-21201-1drjkbi.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=638&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/101480/original/image-20151110-21201-1drjkbi.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=638&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/101480/original/image-20151110-21201-1drjkbi.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=801&fit=crop&dpr=1 754w, https://images.theconversation.com/files/101480/original/image-20151110-21201-1drjkbi.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=801&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/101480/original/image-20151110-21201-1drjkbi.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=801&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Scanning electron microscope images of hairs on a honeybee’s forelimb.</span>
<span class="attribution"><span class="source">Georgia Tech</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>To understand how animals get clean, one must first understand how they get dirty. Dirt accumulates on an animal’s exterior just as a consequence of living life. The surface area of an animal is not as easy to figure out as measuring the dimensions of a cardboard box. Most animals – from mosquitoes to elephants – are hairy. Beyond the exterior of a creature’s skin, hairs provide further surface area where dirt can accumulate.</p>
<p>We found that on average, hair increases an animal’s apparent surface area by a factor of a hundred. Thus, a cat has a surface area of a ping-pong table. (This explains why its so hard to get pets clean.) A chinchilla has the surface area of an SUV. And a sea otter has the surface area of a hockey rink.</p>
<p>We people have about <a href="http://bionumbers.hms.harvard.edu/bionumber.aspx?&id=101509">100,000 hairs on our head</a>. The number of hairs on other animals is comparatively staggering. A butterfly has 100 billion hairs, more than 10 times that of a beaver. The bee has three million hairs, the same number as a squirrel.</p>
<p>Moreover, on animals there are as many types of hairs as we have types of hairdos. Animals have trichia, spines, macrotrichia, setae, scales, hairs <a href="http://www.springer.com/us/book/9780792371533">of all shapes and sizes</a>. One thing is clear: hair increases the surface area of the body, and so makes the problem of cleaning much worse. Which would you rather clean, a linoleum floor or a shag carpet?</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/raojaROtFS0?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">A fruit fly brushing cornstarch off of its head and antennae. This is high-speed video, slowed by 33 times.</span></figcaption>
</figure>
<h2>Hair as cleaning apparatus</h2>
<p>To clean its body, nearly all insects have hairy legs, each leg resembling a feather duster. Observing how the legs interact with the body hairs reveals one of the surprising features of hair. We used a <a href="https://www.youtube.com/watch?v=AdpLDyb0G_I&feature=youtu.be">high-speed video camera</a> to watch a fruit fly groom its head with its arms. Particles attached to the body hairs are catapulted at nearly 1,000 times the acceleration of gravity, far faster than the fly can move its limbs. Hairs that initially acted as landing pads for dust now act as trebuchets, triggered by the hairy arms moving over them. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/wn2E_zBM46Y?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">High-speed video, slowed down 600 times, of a strand of human hair flicking the antenna of a fruit fly. The cornstarch particles that are flicked off travel at more than 1,000 times the acceleration of Earth’s gravity.</span></figcaption>
</figure>
<p>Effective cleaning is not simply just designing a good cleaning implement, like the squeegee. It’s also designing a surface that is ready to facilitate grooming. And quite often these surfaces in nature defy imagination.</p>
<p>We identified two main principles of cleaning. The first is a nonrenewable cleaning strategy – it uses the animal’s own energy sources. Examples include grooming, which is similar to vacuuming a carpet and requires energy to move the brush.</p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/101521/original/image-20151111-21232-ck2abt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/101521/original/image-20151111-21232-ck2abt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/101521/original/image-20151111-21232-ck2abt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=631&fit=crop&dpr=1 600w, https://images.theconversation.com/files/101521/original/image-20151111-21232-ck2abt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=631&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/101521/original/image-20151111-21232-ck2abt.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=631&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/101521/original/image-20151111-21232-ck2abt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=794&fit=crop&dpr=1 754w, https://images.theconversation.com/files/101521/original/image-20151111-21232-ck2abt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=794&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/101521/original/image-20151111-21232-ck2abt.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=794&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Shake it off.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/australianshepherds/6039367394">S Carter</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Other examples are wet-dog shaking: no cleaning implement is used, but instead the body’s own inertia. <a href="http://dx.doi.org/10.1098/rsif.2012.0429">A wet dog spins its body</a> at high speed like a washing machine in its spin cycle. Particles and drops are removed, expending the dog’s energy in the process.</p>
<p>Alternatively, there are renewable cleaning strategies – those that don’t require energy from the animal, but come for free. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/101522/original/image-20151111-21201-a6z0s7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/101522/original/image-20151111-21201-a6z0s7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/101522/original/image-20151111-21201-a6z0s7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/101522/original/image-20151111-21201-a6z0s7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/101522/original/image-20151111-21201-a6z0s7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/101522/original/image-20151111-21201-a6z0s7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/101522/original/image-20151111-21201-a6z0s7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/101522/original/image-20151111-21201-a6z0s7.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">Eyelashes are eye cleaners.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/kalexanderson/6653211121">Kristina Alexanderson</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>One example is the eyelash, the rim of hairs encircling the eye. When we walk forward, the <a href="http://dx.doi.org/10.1098/rsif.2014.1294">airflow generated by eyelashes</a> reduces the accumulation of particles by a factor of two, compared to a bare eye. Thus, simply by growing lashes, we can blink half as often, saving that energy for other uses.</p>
<p>Another example is the nanoscale pincushions on the wings of cicada. Bacteria act like water balloons, exploding when they are in contact. Lastly, raindrops can roll down a hairy animal’s fur, pulling particles along with it, and leaving it as clean as a lotus leaf.</p>
<h2>Surface + energy + behaviors = clean</h2>
<p>How animals get clean is an interplay among the surface of animal, its behaviors and the energy of its environment. An animal gets clean for free if it has the right kind of surface. If we have this mindset, perhaps we can design new devices that get clean for free too.</p>
<p>Consider solar panels. Like the eye, they must let light in. But solar panels <a href="http://www.ijert.org/view-pdf/2295/soiling-and-dust-impact-on-the-efficiency-and-the-maximum-power-point-in-the-photovoltaic-modules">lose 7% of their power annually</a> due to dust accumulation. The most high-tech solution is the squeegee. When you think about it, the computer age has put us light years ahead of our ancestors in terms of communication, but our cleaning methods remain stuck in the past.</p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/101525/original/image-20151111-5460-y0cg7h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/101525/original/image-20151111-5460-y0cg7h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/101525/original/image-20151111-5460-y0cg7h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=638&fit=crop&dpr=1 600w, https://images.theconversation.com/files/101525/original/image-20151111-5460-y0cg7h.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=638&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/101525/original/image-20151111-5460-y0cg7h.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=638&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/101525/original/image-20151111-5460-y0cg7h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=801&fit=crop&dpr=1 754w, https://images.theconversation.com/files/101525/original/image-20151111-5460-y0cg7h.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=801&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/101525/original/image-20151111-5460-y0cg7h.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=801&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Scanning electron microscope image of hairs on a honeybee’s eye.</span>
<span class="attribution"><a class="source" href="http://www.eurekalert.org/multimedia/pub/102875.php?from=311193">Georgia Tech</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Imagine solar panels designed like insect eyes. Thin filaments could be placed periodically to suspend dust above the panel, but still allow light to penetrate. Cleaning the panel would amount simply to swiping it with another brush. Just like the insects, the panel could get clean without the use of water or chemicals. Similarly, video cameras, the eyes of robots, could be rimmed with eyelashes to reduce deposition. Building synthetic hairy systems is the subject of our National Science Foundation grant, <a href="http://www.nsf.gov/awardsearch/showAward?AWD_ID=1510884">Engineering Insect Eyes</a>.</p>
<p>We typically envision future robots covered in smooth shiny surfaces, like a chrome-buffed automobile. But in nature, smooth surfaces are hardly the norm. Future tabletops may have nano-size posts that stretch and kill bacteria on contact. Robotic rovers may be covered with hairs that sense their environments, suspend particles and enable easy cleaning. Indeed, the future may be looking rather hairy.</p><img src="https://counter.theconversation.com/content/50445/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>David Hu receives funding from National Science Foundation.</span></em></p><p class="fine-print"><em><span>Guillermo Amador 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>Cleanliness is next to godliness. Did you know hairiness is a part of the equation as well?David Hu, Associate Professor of Mechanical Engineering and Biology, Adjunct Associate Professor of Physics, Georgia Institute of TechnologyGuillermo Amador, Assistant Professor in Experimental Zoology, Wageningen UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/279042014-06-19T05:05:09Z2014-06-19T05:05:09ZNature must remain at the heart of engineering solutions<figure><img src="https://images.theconversation.com/files/51525/original/6svdr79s-1403085549.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Inspired by Alpine seeds that stuck to dog fur.</span> <span class="attribution"><a class="source" href="http://en.wikipedia.org/wiki/Velcro#mediaviewer/File:Velcro_Hooks.jpg">Alexander Klink</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>Last week, David Taylor of Trinity College Dublin argued that <a href="https://theconversation.com/simply-copying-nature-is-no-way-to-succeed-at-inventing-just-ask-leonardo-da-vinci-27403">simply copying nature is no way to succeed at inventing</a>. His main point is valid – there are indeed not many chances for engineers to make a useful direct copy of a natural system. But there are plenty of ways in which we should be copying nature. More importantly, the way problems are solved in nature needs to shape our thinking when it comes to engineering.</p>
<p>One of the issues that Taylor raises is the high failure rate of natural materials, whereas engineers prefer to have fail-proof solutions. Monkeys in the wild <a href="http://press.princeton.edu/titles/7313.html">break about four bones every year</a>, for instance, so bones would not be a good source for inspiration to build engineering materials. </p>
<p>But bones aren’t fail-proof, because natural systems don’t evolve to be. As soon as a biological entity can perform its function, there is no longer an evolutionary driving force pushing further change. Bones often break but the “cost” of this failure has proven to be biologically acceptable. It isn’t the top priority in the evolution of the animal. When such failures occur, they tend not to be a life-or-death injury. </p>
<p>Of course we don’t always get it right in our quest for near-perfect materials either. In the 1970s <a href="http://resources.schoolscience.co.uk/Corus/16plus/steelch3pg1.html">high-strength steel</a> was fashionable, because with it one could build lighter, finer structures. In the exuberance of the era, structures were designed in a way that meant the failure of one component could take down the entire structure. This happened in dramatic fashion in 2007, when a motorway bridge across the Mississippi river in the US collapsed within a matter of seconds, <a href="http://www.johnweeks.com/bridges/pages/ms16.html">killing 13 people.</a> In light of this catastrophe, it has become more appealing to build timber bridges, based on natural materials. These have some risk of failure but but the bridge is designed in a way that would stop one component taking down the rest if it failed.</p>
<p>The nice thing about nature is that if bones break, they also heal. Engineers have, in fact, recently started to incorporate such abilities in a range of <a href="http://www.bbc.co.uk/news/science-environment-19781862">materials with self-healing capabilities</a>. For instance, capsules of one material are distributed throughout a component, and a healing chemical is incorporated into the material matrix. The two components don’t interact until failure breaks the capsules, allowing the two components to mix and “heal” the crack. </p>
<p>It is a philosophical shift to use a material that heals, instead of trying to design a material that won’t break down. By copying nature’s healing mechanism, we can acknowledge the inevitability that things do break. We can engineer self-healing materials, that do not include living biological cells but that still have intrinsic repair mechanisms. Such thinking opens up new engineering approaches to working with materials and structures. </p>
<p>Taylor also <a href="https://theconversation.com/simply-copying-nature-is-no-way-to-succeed-at-inventing-just-ask-leonardo-da-vinci-27403">raised the question</a> “Where do inventions come from?” There has been some fascinating analysis to answer this question. It started with Genrich Altshuller, a Soviet patent clerk. </p>
<p>For a patent to be granted, an invention must be new and must not be an obvious development of a previous invention. Altshuller analysed patents granted after World War II to trace different inventive principles – generalised rules used by inventors to tackle a problem. He found only 40 such principles among thousands of patents, suggesting inventors were following similar paths.</p>
<p>He went on to devise a system – best known by its Russian language acronym “<a href="http://www.triz.co.uk">TRIZ</a>” – for solving any particular problem. First he generalised the problem and looked at which of the 40 principles “normally” solved that generalised problem. Then he applied that principle to the specific case. This systematic approach to invention shows the inventor as the opposite of the mad, genius caricature.</p>
<p>Altshuller’s work was analysed further by Julian Vincent, a biomimetics professor then at the University of Bath, and his colleagues. In their <a href="http://rsif.royalsocietypublishing.org/content/3/9/471.abstract">2006 study</a>, they showed that there was only a small similarity between the way engineers solve problems, as typified by the 40 inventive principles from TRIZ, compared with the way similar problems in nature are solved. The most important take away from their analysis is that the engineering solutions tended to be energy-intensive, while the biological solutions were not. </p>
<p>If we copy nature, we have the potential to address some of the greatest challenges facing us in the 21st century. If we work intelligently, with a firm view towards trying to understand why natural systems are the way they are, there is great potential for engineers to succeed. </p>
<hr>
<p><em>Next, read this: <a href="https://theconversation.com/simply-copying-nature-is-no-way-to-succeed-at-inventing-just-ask-leonardo-da-vinci-27403">Simply copying nature is no way to succeed at inventing – just ask Leonardo da Vinci</a></em></p><img src="https://counter.theconversation.com/content/27904/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Michelle Oyen receives funding from EPSRC on self-healing materials for structural applications.</span></em></p>Last week, David Taylor of Trinity College Dublin argued that simply copying nature is no way to succeed at inventing. His main point is valid – there are indeed not many chances for engineers to make…Michelle Oyen, Lecturer in Mechanics of Biological Materials, University of CambridgeLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/274032014-06-10T04:52:40Z2014-06-10T04:52:40ZSimply copying nature is no way to succeed at inventing – just ask Leonardo da Vinci<figure><img src="https://images.theconversation.com/files/49900/original/2kccx752-1401452286.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">One design that didn't take off.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/tom-margie/1430804368">tom-margie</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>Where do inventions come from? There’s no magic formula, but there are ways to improve your creativity. One method is to look at nature. Some call this activity bionics, others call it biomimetics. Whatever you call it, it is big business: in recent years we have seen the rise of university courses, institutes and learned journals in the subject. The term I prefer is bio-inspired design, and here’s why.</p>
<p>If it hadn’t been for birds, I doubt if anyone would have even thought that it might be possible for something heavier than air to get airborne. With his flying machine, Leonardo da Vinci had a detailed design that looks, on paper, very impressive. But it doesn’t work. </p>
<p>Several centuries passed before we realised why. The bird’s wing performs two separate tasks, both of which are essential. By its shape, it provides lift when air passes over it. And by its movements it provides power. The crucial step to making aircraft was to separate these two functions, leaving the wing to do the lifting but transferring the power function to an engine and propeller, something no bird ever possessed.</p>
<p>There is an important lesson here. The first step is to imitate nature, and the second step is to abandon nature’s ways. At some point you have to give up the love affair, dump nature and move on. The problem is that simply copying nature doesn’t work. </p>
<p>Here is an example from my field – structural materials. Bones are an excellent material, providing support and strength. Currently we can’t make materials that reproduce a bone’s internal structure. But even if we could, we wouldn’t be able to use it in engineering structures for many reasons. </p>
<p>First, nature can live with failure, but we can’t. When we design a component for a car or aircraft, we need to ensure that the probability of failure of that part per year is something like one in a million. Because a vehicle has thousands of parts and is supposed to last for tens of years without catastrophic failure. </p>
<p>But nature is happy to work with much higher failure rates: the chance of breaking a bone if you are a monkey in the wild is about <a href="http://press.princeton.edu/titles/7313.html">2% per bone per year</a>. If engineers worked to that standard they would soon be looking for another job. The reason for this difference is that for nature the failure of an individual is of no consequence. What matters is the survival of the species. So nature is wasteful of individual lives, in a way which we risk-averse humans can’t tolerate.</p>
<p>In a recent paper, published in the <a href="http://pic.sagepub.com/content/early/2014/04/01/0954406214530881.abstract">Journal of Mechanical Engineering Science</a>, I consider several bio-inspired concepts. One is the work of the German engineering Claus Mattheck. His book Design in Nature: Learning from Trees is a classic on biomimetics. Mattheck’s lifelong love affair with trees has led to many important innovations in engineering design. </p>
<p>One of these considers the junction where the branch of a tree meets the trunk. Mattheck said the curvature around this junction was very cleverly designed to minimise the concentration of stress that occurs when engineers try to design the same shape. He suggested that the tree was sensitive to stress and so, as it grew, would deliberately place material in such a way as to minimise stress. He developed a computer programme to simulate tree growth, and the result was a fantastic reduction in stress concentration, allowing for more slender components. This is important, because shaving a few percent off the weight of a component in a car means lower material costs, less fuel usage, less CO<sub>2</sub> emissions and so on.</p>
<p>But when I go and actually look at trees, I don’t think Mattheck is right. I don’t think trees are doing what he thinks they are doing, and proving it would be quite difficult. But of course it doesn’t matter if you remember that nature was only the starting point, not the objective of the exercise.</p>
<p>Another example is the recent news that scientists have discovered an animal that runs faster than any other – and <a href="http://www.ibtimes.com/worlds-fastest-land-animal-has-new-name-meet-paratarsotomus-macropalpis-mite-made-speed-1577349">it’s a mite</a>. The story – no doubt distorting the original science – was that this mite runs faster than a cheetah if you measure speed in terms of how many body lengths it covers per second. </p>
<p>The report predicted that this fascinating result will be used by bioengineers to improve engineering design. Well, perhaps it will, but if so the inspiration will be the opposite of what it seems. It is well known that smaller animals can run faster when measured by body size – even the humble cockroach beats the cheetah on that measure. But a simple biomechanical model, applying the appropriate scaling laws, would suggest that all animals should be able to run at the same absolute speed, not the same relative speed. So the inspiration here will come from asking “why are the little guys so slow?”. </p>
<p>Nature can be a wonderful muse, an excellent starting point in the development of a new engineering device or material, but don’t make the mistake of thinking that nature has already solved your problems for you.</p>
<hr>
<p><em>Next, read this: <a href="https://theconversation.com/nature-must-remain-at-the-heart-of-engineering-solutions-27904">Nature must remain at the heart of engineering solutions</a></em></p><img src="https://counter.theconversation.com/content/27403/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>David Taylor 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>Where do inventions come from? There’s no magic formula, but there are ways to improve your creativity. One method is to look at nature. Some call this activity bionics, others call it biomimetics. Whatever…David Taylor, Professor, Trinity College DublinLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/197602013-11-05T00:52:50Z2013-11-05T00:52:50ZMullet over: how robotics can get a wriggle on with fishy locomotion<figure><img src="https://images.theconversation.com/files/34303/original/f9rjszd5-1383523466.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Simple, yet so effective – a fish's swimming motion removes the trade-off between stability and manoeuvrability.</span> <span class="attribution"><span class="source">Mell P</span></span></figcaption></figure><p>Teaching a robot to walk – even poorly – requires huge investment into computational resources. How is it that even the simplest animals are able to achieve far more sophisticated feats of manoeuvrability?</p>
<p>In a paper <a href="http://www.pnas.org/cgi/doi/10.1073/pnas.1309300110">published today</a> in the Proceedings of the National Academy of Sciences (PNAS), cross-disciplinary researchers have taken a major step forward in answering this question. </p>
<p>Perhaps surprisingly, a feature of many animals’ movement is that substantial forces are produced in directions other than those necessary for the animal to move through its environment. Some of these are perpendicular (or even opposite!) to the direction of travel. </p>
<p>This paper demonstrates how these so-called “antagonistic” (or mutually opposing) movements are the secret underlying nature’s ability to eliminate the trade-off between manoeuvrability and stability.</p>
<h2>A pain in the bass</h2>
<p>Researchers from the fields of robotics, biology and computational modelling have been collaborating to explain how animals can execute incredible feats of manoeuvrability with little-to-no conscious effort.</p>
<p>Anyone who has witnessed a <a href="https://theconversation.com/robocup-2013-new-moves-to-keep-players-on-the-ball-14287">game of robot soccer</a> will realise that humanoid robots are far from graceful in their attempts at walking – check out the video below. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/j9arXtrhZBo?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">RoboCup bloopers.</span></figcaption>
</figure>
<p>This problem becomes more prominent as the size of robots increase, with the adult-sized RoboCup league still requiring human handlers to prevent the robots from falling. Aside from the obvious limitations of large robots requiring large motors, struggles arise in both stages of “teaching” a robot to walk:</p>
<ul>
<li>The walk engine: a <a href="http://en.wikipedia.org/wiki/Kinematic_chain">kinematic model</a> must be derived for the robot, with corresponding systems to dynamically control balance as the robot walks. Although many of these models are derived from simple ideas (such as the commonplace <a href="http://en.wikipedia.org/wiki/Inverted_pendulum">inverted pendulum model</a>), their implementation is complex and parametrised by dozens of different values.</li>
<li>Parameter optimisation: a typical bipedal robot walk engine may contain in excess of 50 individual parameters, representing both physical properties (such as stance height, step length) and more abstract feedback controller values.</li>
</ul>
<p>Both of these components is the focus of much research, with the latter posing such a complex task that it has motivated the development of <a href="http://www.davidbudden.com/research/budden2013probabilistic/">speciality optimisation algorithms</a>. </p>
<h2>Sofishticated movement</h2>
<p>As the mutually opposing forces exhibited during an animals’ movement effectively “cancel out” over each gait cycle, they are difficult to observe and their role has previously remained a mystery. </p>
<p>Although clearly not contributing directly to the animals’ movement, today’s PNAS paper demonstrates that these forces play the equally important role of simplifying and enhancing the actual control of locomotion. </p>
<p>This relationship was investigated by studying the movement of the <a href="http://en.wikipedia.org/wiki/Glass_knifefish">glass knifefish</a> (<em>Eigenmannia virescens</em>), which produces mutually opposing forces during a “hovering” behaviour similar to a hummingbird feeding from a moving flower.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/34222/original/k6syjyww-1383283446.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/34222/original/k6syjyww-1383283446.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/34222/original/k6syjyww-1383283446.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=559&fit=crop&dpr=1 600w, https://images.theconversation.com/files/34222/original/k6syjyww-1383283446.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=559&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/34222/original/k6syjyww-1383283446.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=559&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/34222/original/k6syjyww-1383283446.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=702&fit=crop&dpr=1 754w, https://images.theconversation.com/files/34222/original/k6syjyww-1383283446.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=702&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/34222/original/k6syjyww-1383283446.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=702&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) <em>Eigenmannia virescens</em> B) Biomimetic robot C) Computational model.</span>
<span class="attribution"><span class="source">PNAS</span></span>
</figcaption>
</figure>
<p>In principle, the glass knifefish could adopt a simple locomotion strategy of moving its fin in one direction or another. However, for some additional energetic cost, the fish instead adopts a strategy that relies on mutually opposing forces to stabilise using <a href="http://en.wikipedia.org/wiki/Feedback#Control_theory">feedback control</a> of counter-propagating waves. </p>
<p>These waves offer two major advantages over simpler strategies:</p>
<ul>
<li>they passively reject perturbations (resulting in increased passive stability)</li>
<li>they require considerably less control effort (increased manoeuvrability).</li>
</ul>
<p>This elimination of the trade-off between manoeuvrability and stability, discovered in measurements of the knifefish, was later confirmed using computational models and experimentation with <a href="http://en.wikipedia.org/wiki/Biomimetics">biomimetic</a> robot (shown in the figure above).</p>
<p>In addition to challenging the manoeuvrability-stability dichotomy within biological locomotion, this research challenges the same trade-off within the engineering of mobile robots. </p>
<p>Evidence suggests that the very design of [animal morphology](http://en.wikipedia.org/wiki/Morphology_(biology%29) facilitates control, thereby reducing the number of physical parameters that must be managed by the nervous system. With further research and modelling of how animals utilise mutually opposing forces, future generations of robots may equivalently require significantly fewer parameters to control. </p>
<p>This <a href="http://en.wikipedia.org/wiki/Dimensionality_reduction">dimensionality reduction</a> would improve the tractability of tuning these parameters to their optimal values, resulting in further improvement in the performance of robot locomotion.</p>
<p>Fin.</p><img src="https://counter.theconversation.com/content/19760/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>David Budden 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>Teaching a robot to walk – even poorly – requires huge investment into computational resources. How is it that even the simplest animals are able to achieve far more sophisticated feats of manoeuvrability…David Budden, Graduate Researcher, The University of MelbourneLicensed as Creative Commons – attribution, no derivatives.