The nano–scale structure of the eyes and wings of insects offers a wealth of ideas for industrial applications such as the design of ultra-low reflection solar cells or highly water repellent materials. Such artificial reproduction of nanostructures occurring in nature or biomimetics necessitates a deep knowledge of the relevant surfaces and of insects themselves.

Here, Mingxia Sun at the Institute of Zoology, Chinese Academy of Sciences, Beijing, in collaboration with co-workers at Beihang University, Beijing, and James Cook University, Australia, describe the relationship between the optical and wetting properties of the 'base' and 'apex' of the forewings of 32 species of cicada.

The researchers deduced that the anti-reflection and wetting properties of cicada wings were due to hexagonal nano-protrusions with diameters 777–148 nm, heights of 159–481 nm, and spaced 44–117 nm.

Furthermore, optical transmission in the 500–:2500 nm range was independent of the morphology of the wings but transmission was enhanced for higher protrusions. Notably, contact angle measurements of droplets on the surfaces of cicada wings showed that the lower the body-to-wing ratio, the weaker the wettability and strongly hydrophobic wings showed enhanced anti-reflectivity in the visible light spectrum.

These experimental results are valuable basic data for the design of biomimetic structures.

The work is reported in Bioinspiration & Biomimetics.