Beetles are often observed being able to tenaciously cling to smooth surfaces, like leaves, hanging on even when those surfaces are bordering on the vertical. A new study reveals that beetles can even keep their footing underwater thanks to tiny bubbles of air trapped between the hair-like structures on their feet.
The scientists published their findings in the journal Proceedings of the Royal Society B. Naoe Hosada, a material scientist at the National Institute for Material Science in Tsukuba, Japan, and Stanislav Gorb, studying biomechanics at the University of Kiel in Germany, have shown how this is possible.
Gastrophysa viridula (leaf beetles) secrete fluid into setae, the hair-like structures on their feet, keeping the insects attached to surfaces they are walking on. However, such forces are usually absent in water. The scientists discovered that G. viridula can walk on flooded surfaces, thanks to bubbles of air trapped in the setae. The bubbles provide adhesion, and might also dry the beetles’ feet, allowing their hairs to function in the same way as they do on dry land.
Inspired by the beetles, the researchers developed a polymer structure covered in bristles that mimics the feet of the beetles. When this substance is attached to small objects, like the treads of a toy, it can successfully stick to vertical surfaces underwater.
Reference: “Underwater locomotion in a terrestrial beetle: combination of surface de-wetting and capillary forces” by Naoe Hosoda and Stanislav N. Gorb, 8 August 2012, Proceedings of the Royal Society B.