Insects in the spotlight
- There are 6.8 million terrestrial arthropods and 5.5 million varieties of insects. Materials engineers have found amazing properties within that rich pool of species, like the strength of spider silk.
- Insects are especially practical to study. Most can be ordered online, and they are not subject to strict animal-protection laws.
The spectacular blue wings of the morpho butterfly fascinate scientists around the world. Some materials engineers are now trying to build an identical replica of the nanostructures that result in that vivid blue, while others want to recreate those dazzling shades for use in the automotive industry. But this species is not the only one generating such keen interest. All sorts of arthropods are increasingly inspiring biomimetics. “It makes sense because there are tons of insects and spiders on the planet,” says Kalina Raskin from the Biomimicry European Centre of Excellence in Senlis, France. “It’s the branch of the animal kingdom with the largest number of individuals.” There are 6.8 million terrestrial arthropods and5.5 million varieties of insects, according to a 2015 study.
And materials engineers have found some amazing properties within that rich pool of species, such as the strength of spider silk. The webs woven by certain arachnids can withstand up to 380 tonnes, the weight of a Boeing 747 crammed with passengers. In2011, Horst Kessler and his team from the Institute for Advanced Study at the Technical University of Munich (TUM) discovered the molecular mechanism that makes silk yarn so sturdy. In 2014, the TUM spin-off AMSilk took these findings and began producing a natural fibre on an industrial scale. By highlighting the fibre’s durability compared to others in plastic, the start-up has been selling its product to companies active in the textile, automotive or interior decorating industries.
Beetles for sale online
The physicist Ullrich Steiner says that insects are particularly practical to study. “Most can be ordered online. They aren’t subject to any strict animal protection laws. And compared with plants, they don’t wither and are more robust,” says the professor from the National Center of Competence in Research (NCCR) for Bio-Inspired Materials at the University of Fribourg. The NCCR brings together 15 research groups from throughout Switzerland, including those from the École Polytechnique Fédérale de Lausanne.
Using the specimens he has ordered online, Ullrich Steiner hopes to reproduce natural photonic surfaces such as the shell on the Cyphochilus beetle. The insect’s most striking feature is its bright white colour, a rare phenomenon in nature. White only occurs when a surface reflects light in all directions. “This species of beetle is as white as paper, but the layer of its shell that produces the colour is 100 times thinner than a sheet of paper,” he says. “If we use our current technology to create something similar, for now the material comes out transparent.”
To solve the mystery behind this immaculate shell, the research team works with X-ray nanotomography and computer modelling. If they are able to imitate nature, they could use it in new technology including thinner paper and paint and similar structures for solar cells to improve light absorption. The main advantage of insects and other arthropods is that they are just different enough from human beings, says Thibaud Coradin, head of the Materials and Biology team at the Chemistry of Condensed Matter Laboratory in Paris.
“We won’t be discovering much new about ourselves if we study the biomimetics of mammals. And if we look at species that are too distant, it would be too difficult to adapt findings to our needs. So arthropods – which are neither too far nor too close – representa good compromise.”
Another advantage of working with insects is that many scientists share a basic knowledge of entomology. “The biodiversity of insects was identified along time ago, because these are organisms that we see, that we live with,” the French chemist says. “We’re familiar with them and understand many of their characteristics, without being zoologists. So, depending on what we’re looking for, we’ll think of a given species that can fly silently, another that can change colours or another that can live in the water for a long time, and so on.”
The blue colour of the morpho – widely known to butterfly catchers – sparked the curiosity of Anders Kristensen, a professor with the Department of Micro- and Nanotechnology at the Technical University of Denmark. Inspired by the microscopic surface structure that creates the bright colour of the wings, the physicist and his team developed an innovative technology. “We don’t use any dye or pigments, but photonic surfaces,” he says. “We’ve developed nanotextures that are cast directly into the surface of the plastic components.” And the structures are tiny. “They’re cylinders that are 100nanometres deep and high, coated in a layer of aluminium. That’s what creates the colour using a resonance absorption technique. And last, we add a thin protective layer.” Through the IZADI-Nano2Industry project, mainly financed by the Horizon 2020 European research programme, the Danish scientist is working on producing materials for automotive, agricultural and construction machinery.