Natural inspiration 2

More examples of nature inspiring innovation.

Cling like a limpet

Scientists at the University of Portsmouth believe they have found the strongest natural material known to humans: limpet teeth. Limpets—small aquatic snail-like creatures with conical shells—use their teeth to cling to the rock surfaces on which they live. The teeth contain a hard mineral known as goethite, which form in the limpet as it grows. If the biological structure of the teeth can be mimicked, the resulting material could be used in high-performance engineering applications such as Formula 1 racing cars, the hulls of boats, and aircraft structures. The material currently being tested is almost 100 times thinner than a human hair. The photograph shows a scanning electron microscope image of limpet teeth. The teeth are slightly less than a millimetre long, and curved.

University of Portsmouth (2015, February 18). Scientists find strongest natural material.

Barber, A.H., Lu, D., & Pugno, N.M. (2015). Extreme strength observed in limpet teeth. Royal Society Journal Interface, 12(105). DOI: 10.1098/rsif.2014.1326. Article freely available.

Skin changes

Chameleon

Researchers at The Optical Society have made a material that changes colour when stretched, inspired by the way a chameleon changes its skin. Chameleons manipulate nanoscale structures to change the colour of their skin. A layer of skin cells contains nanocrystals, which reflect light at wavelengths related to their spacing. When the chameleon’s skin is relaxed, it takes on one colour. When it stretches, the nanocrystals spread out, and the colour changes.  This material might be used in anything from displays to motorcars.

Octopus

A different material that changes both colour and opacity when stretched was inspired by the way octopuses change colour from transparent to opaque, in shades of red, pink, purple, and blue. Scientists at the University of Pennsylvania coat the stretchy, rubbery material in light-bending silica nanoparticles, similar to those used in the cosmetics industry. In its “resting” state, the material is highly transparent, but when stretched, changes colour depending on the nanoparticle size. Not only can the material take on any colour, it can also be made to reflect infrared light. A potential application is in energy-efficient buildings which, when coated in this material, can change colour to better absorb or reflect sunlight.

Turkey

Skin changes have also inspired a way to identify toxins cheaply and conveniently using a smartphone. Turkeys can change the colour of their skin from red to blue to white, due to bundles of collagen interspersed with a dense array of blood vessels. When the blood vessels swell or contract, depending on whether the bird is excited or angry, the amount of swelling changes the way light waves are scattered, which in turn alters the colours on the turkey’s head. Scientists at UC Berkeley found a way to get M13 bacteriophages, benign viruses with a shape that closely resembles collagen fibres, to self-assemble into patterns that could be easily fine-tuned. Like collagen fibres, these phage-bundled nanostructures expand and contract, resulting in colour changes. When these biosensors are exposed to a range of volatile organic compounds, the viruses swell rapidly, causing specific colour patterns that serve as “fingerprints” to distinguish the different chemicals tested. Some colour changes, however, are extremely small and almost undetectable without the use of technology. The researchers created a smartphone app, iColour Analyser, that can recognize even small changes in the visible colour spectrum. The app utilizes the high-resolution cameras on smartphones to analyse photos taken before and after a supposed colour change, and determine whether a chemical is present in the environment. The technology may be used in future to identify the presence of lung cancer and other diseases by monitoring bodily functions, such as breathing.

Gizmodo (2015, 14 March). We can now make synthetic chameleon skin.

Motherboard (2015, 10 March). In the future, your city could change colours like an octopus.

Zhu, L., Kapraun, J., Ferrara, J., & Chang-Hasnain, C.J. (2015). Flexible photonic metastructures for tunable coloration. Optica, 2(3). pp. 255-258. DOI: 10.1364/OPTICA.2.000255.

University of California - Berkeley. (2014, January 21). Turkeys inspire smartphone-capable early warning system for toxins. ScienceDaily.

Oh, J.-W., et al. (2014, 21 January). Biomimetic virus-based colourimetric sensors. Nature Communications, 5. DOI: 10.1038/ncomms4043

Bug-eyed

The United States Air Force (USAF) is working on a fly-like, artificial compound eye that could be used for seekers on missiles and other targeting systems. Instead of one large optical sensor with a limited field of view, the artificial compound eye comprises a large array of equidistant smaller staring optical sensors, each pointing in a slightly different direction. The information from those sensors is processed and digitally “stitched” together to give a high-resolution and wide field-of-view image. Such an ‘eye’ could even scan for new targets while simultaneously tracking multiple targets.

Rogoway, T. (2015, 11 March). How this bug-inspired compound eye could transform missile seeker tech. Foxtrot Alpha.

Bendable circuits

Normal printed circuits, built on rigid silicon substrates, break when they stretch, which is why rollable phones and tablets are not commonplace. Taking rose petals as model, researchers from Hong King Polytechnic University have created a material that allows standard printed circuits to flex without breaking. The surface of rose petals consists of a series of microscale craters, with sharp ridges that act as crack-stopping edges to prevent tearing. When this material is used, the electrical properties of the printed circuits remain consistent even when the substrate is stretched by more than 40 per cent, and continue to function up to 90 per cent.

Image by Beatrice Murch, under Creative Commons license

Condliffe, Jamie (2015, 6 March). New stretchable circuitry is inspired by rose petals. Gizmodo.

Guo, R., et al. (2015, March). Biomimicking topographic elastomeric petals (E-Petals) for omnidirectional stretchable and printable electronics. Advanced Science, 2(3). 10.1002/advs.201400021.