By Thomas HornigoldMar 26 2018
Biomimetics develops research and technology by drawing inspiration from nature. To academics like Leonardo da Vinci, it seemed the most obvious thing to do. When he was designing his flying machines, he drew thousands of keenly-observed sketches of birds, reasoning that either God’s creation was perfect and would, therefore, unlock the secrets to flight, or perhaps, less profoundly, that it’s best to copy something that works.
Nowadays, we appreciate that biological structures have been fine-tuned by millions of years of random trials, adaptations, mutations, and so on. These structures and materials are often incredibly well-suited to the particular task at hand and can achieve things in the novel and surprising ways.
Exploring Animal-Based Biomimicry
A classic example of successful biomimicry is that of butterfly wings: their unique and vibrant colors are obtained, not by pigmented chemicals in the wing, but by microstructures that take advantage of optical phenomena like refraction, diffraction, and scattering of light at different wavelengths. Careful examination of these microstructures enabled Qualcomm to patent a display technology, Mirasol, which operates on the same principle.
In robotics, you can see biomimicry in action in CASSIE, a bipedal robot that’s inspired not by humans, but by ostriches.
What does nature need to do well to survive? Creatures need to be able to move quickly, if necessary. They need to be able to sense danger; whether that danger is in the form of poisons, chemicals, or dangerous approaching predators. We also know that animals have senses of taste and smell – biological chemical sensors – that are many times more powerful than human equivalents. But the potential for bio-inspired sensors in the future goes far beyond the Victorian-era trick of taking canaries into coal mines to discover any carbon monoxide.
Take the case of the “jelly” that’s present in the noses of sharks, and also some types of skate and ray. This gel can sense temperature changes, but it’s also exceptionally electrically conductive – on par with some of the most sensitive proton-conducting polymers ever synthesized in the lab. This material, combined with electro-sensing cells in the shark’s nose, may allow it to detect the electrical fields produced by moving prey too far away to see. The applications of this shark jelly (or similar materials) are evident in the medical sensing realm, where it would allow slight changes in electrical activity in the brain or nervous system could be monitored.
Another recent development is biomimicry for the sense of fluid flow. This could be used by automated systems in the industrial internet of things, or even by robots. In a paper published in Bioinspiration and Biomimetics, researchers from the University of Illinois at Urbana-Champaign and Illinois' Advanced Digital Sciences Centre in Singapore developed a tactile array of sensors inspired by the whiskers of animals like otters.
These sensors measure the drag force across the ‘whisker’ which can, in turn, allow for the fluid flow to be mapped out. This type of “vibrissal” sensing has the advantage of working well in dark and murky environments – which is precisely when the animals need them most.
Mapping out fluid flow – which has clear industrial applications - is just one example of the tasks for which technological whiskers can be used. Other groups have developed sensors that are designed for fine feature resolution and 3D mapping of objects.
Small fibers like the whiskers can provide a wealth of data – not only about the intricate details of a 3D object but also about its texture. A sweep of a robotic whisker can give information on the surface by analyzing the power spectral density of the signal. Pearson et al. found in 2013, that they could improve their whisker-sensor by adding an extra degree of freedom that mimicked the mystacial pad; a region of the rat’s snout muscles associated with fine tactile sensing.
One notable bio-inspired breakthrough in the sensor field was the use of sensors inspired by cricket-hairs. Crickets are highly adapted for detecting air-flows using the hairs that project from their abdomens; this information tells the cricket about the location of nearby predators, as well as the velocity and direction of travel. The hairs are attached to a plate beneath them, which varies in capacitance as the hairs move, producing an electrical signal.
The researchers were able to build an array of sensors similar to this, providing a kind of camera that can construct and visualize the airflow by compiling and processing data from each of the hairs. Given the increasing demand for inexpensive flowmeters that can provide detailed visualization of the flow under a range of different circumstances, this kind of development is likely to be applied.
A 2014 study drew its inspiration from spiders, mimicking the array of parallel slits that are found on the legs of the wandering spider. The team replicated this sensor using a thin film of platinum on a polymer sheet, with nanoscale cracks. When slight disturbances shift these cracks, the sensor can pick it up as a change in the electrical conductivity of the platinum sheet. The result is an ultra-sensitive vibration detector. The new challenge is a signals-processing one – differentiating the vibrations you want to analyze from background noise, something that the spider is well-adapted to do when searching for prey or evading predators.The world of insects is perhaps a particularly exciting area, given that there are so many insect species that have yet to be discovered.
Searching in extreme environments, the cavefish that is entirely blind manages to sense its surroundings using “lateral lines” – motion-sensors that detect disturbances in the fluid around the fish. The fish have even been observed to use this type of sensation for energy-efficiency, favoring paths where the turbulent wakes or vortices of other objects make swimming easier: venturing into the slipstream of objects it cannot see.
The difference between modern times and the era of Leonardo da Vinci is that we can now fabricate devices on tiny scales, with exquisite precision in the lab. But, for all the accumulated weight of human knowledge and ingenuity in the centuries since then, we still have – to quote Darwin - an unfathomable amount to learn from the “endless forms most beautiful and most wonderful that have been, and are being, evolved.”
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