Self-cleaning cicada wings inspire new smart materials
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Researchers studying the extraordinary properties of cicada wings suggest that they could serve as the inspiration for new self-cleaning, de-icing, anti-fogging surfaces.
Aside from the obvious benefit of allowing cicadas to fly, these insects’ wings are excellent at repelling water to keep the creature dry. This property is just one of billions of nature’s secrets that scientists and engineers are attempting to replicate.
“The property that allows a surface to repel water is called hydrophobicity and it causes water to bead up and roll away,” said Professor Nenad Miljkovic, a professor of mechanical science and engineering at the University of Illinois at Urbana-Champaign.
“Superhydrophobicity is an extreme form of this property and cicada wings that have this feature have a rough nanotexture that creates open spaces around water droplets, allowing surface tension to force the droplets to jump off of the wings.”
Cicada wings are studded with waxy nanoscale cones, creating a water-repellent film. As raindrops fall on this film, they coalesce and roll off, naturally removing dirt. When bacteria land on the wings, their membranes are torn apart by the spikes.
This makes cicada wings the first known biomaterial capable of killing bacteria.
In the past, researchers studying the wings of cicadas have focused on one individual species at a time. The University of Illinois researchers, however, wanted to take an approach which accounts for natural variation. They collected four different species: a wetlands cicada, a forest cicada, a prairie cicada and a periodic seventeen-year cicada.
The engineers and entomologists used high-speed microscopic photography to study the ability of the cicada wings to repel water. They found that all cicadas – even those living in dry habitats – had superhydrophobic wings. The entomologists suggested that differences in species life cycles and species relatedness may be a better predictor of superhydrophobicity than habitat.
This more generalised understanding of the properties of cicada wings could, the researchers hope, make the artificial construction of surfaces inspired by the wings possible in the future. This could lead to the development of self-cleaning, antibacterial, water-repellent surfaces, with myriad applications.
“We are learning as much as we can from the natural design of cicada wings to engineer artificial objects that are useful to humans,” said Professor Miljkovic.