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23 November 2017

The Animal Kingdom Inspires Scientists

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To overcome the challenges of the environment and be able to survive, animals have developed remarkable capabilities over millions of years—from thick fur to protect against low temperatures to hundreds of eyes that monitor the movements of their adversaries.

Human beings do not possess any of these extraordinary abilities, but thanks to our intelligence we are trying to imitate them in the laboratory. Thousands of scientists from around the world are working in this field of biomimicry in areas such as new materials, energy and robotics. Nature is their muse.

Aerial and aquatic flapping

Weighing just 175 milligrams, RoboBee is an insectoid robot capable of flying and swimming. The scientists who developed it took their inspiration from the honey bee, an insect with a similar weight and frequency of flapping. They also turned their attention to some species of plankton that flutter underwater.

“This is the first hybrid aerial-aquatic micro-robot at the insect scale,” Yufeng Chen, researcher at the John A. Paulson School of Engineering and Applied Sciences at Harvard University (USA), tells OpenMind. In a study published in the journal Science Robotics, Chen and the rest of the scientists have shown for the first time that the locomotion of the flapping wing is feasible in both air and water. This quality could allow the robots to participate in aquatic rescues or to analyse water quality.

Beneath polar fur

To protect itself from the low temperatures in which it lives, the polar bear has a coat very different from that of other animals. “Its hair has a unique structure, well-formed at the microscopic level, that permits the trapping of air inside, which serves to provide the necessary thermal insulation,” explains Mohamed Khayet, professor of applied physics and director of the Membranes and Renewable Energies Group at the Complutense University of Madrid, in a conversation with OpenMind.

Polar bear’s hair has a unique structure, well-formed at the microscopic level, that permits the trapping of air inside, which serves to provide the necessary thermal insulation. Credit: AWeith

These thermal properties have inspired a team of scientists to design a new type of nanostructured membrane. By focusing on the hair structure, they have developed a device that achieves low thermal conductivity and can be used for water treatment, including the desalination of waters with a high salt or brine content. In addition, water contaminated with radioactive materials can be treated with this type of membrane and products of great value for the industry can be recovered. “Nature hides answers to most of the questions that we scientists ask ourselves when developing new materials,” says Khayet.

Imitating fly eyes

Flies and other insects have compound eyes, that is, they are composed of dozens and even thousands of lenses that allow them to detect very fast movements. It is precisely this kind of visual honeycomb that has solved the problem that was troubling a team of researchers from Stanford University (USA) concerning their solar cells based on perovskite.

Flies have compound eyes, they are composed of dozens and even thousands of lenses that allow them to detect very fast movements. Credit: Virvoreanu-Laurenti

This material is capable of converting sunlight into electricity with an efficiency similar to traditional solar cells made with silicon. The problem with perovskite is its fragility and deterioration when exposed to high temperatures and humidity, at least with flat designs, the usual in most solar panels. By imitating the eyes of flies, researchers have created a solar cell composed of a large honeycomb of perovskites, each following a hexagonal shape 500 microns wide. In tests under extreme conditions, the cell continued to generate electricity with high efficiency, improving what was achieved with flat designs.

Black wing secrets

Insects and the energy sector make a good team. The wings of the black butterfly (Pachliopta aristolochiae) could improve the absorption of light by up to 200%. “The fact that this butterfly species is so black signifies that it efficiently absorbs sunlight (at least) in the visible portion of the solar spectrum,” Guillaume Gomard, a researcher at the Technological Institute of Karlsruhe (Germany), tells OpenMind.

Nanostructures of the wing of Pachliopta aristolochiae can be transferred to solar cells and enhance their absorption rates by up to 200 percent. Credit: Radwanul H. Siddique, KIT/Caltech.

In an article published in Science Advances, Gomard and other scientists have looked at the properties of these particular wings and copied them into solar cells. One of their characteristics is that they have nanoholes of variable diameters located in a disorderly manner. “The apparent “disorder” of the black butterfly design is advantageous for harvesting more light, regardless of the illumination conditions,” says the researcher. Its disordered arrangement allows for absorption across a very broad spectrum and ensures that light is absorbed efficiently, whatever the position of the Sun in the sky.

Turning over with a click

Although there are beetles that are incapable of righting themselves if they end up on their backs, there is one family, the elateridae (commonly called click beetles), which has overcome this problem thanks to a violent “click” generated by their body that throws them into the air. A team of researchers from the University of Illinois (USA) has studied this hinge-type mechanism between the head and abdomen of the insects that allows them to flip over and get back on their feet again without using their legs.

Click beetles can jump without the aid of their limbs when they are tipped onto their backsides. Credit: Judy Gallagher

The objective of the scientists is to imitate the action in the laboratory in order to incorporate it into those robots that cannot right themselves in another manner if they tip over. For this, they are studying different species of elaterids that vary from a few millimetres to several centimetres in length. The team of researchers, made up of engineers and entomologists, has built several prototypes that have already been presented at different innovation fairs.

Laura Chaparro

@laura_chaparro

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