As its name suggests the glasswing butterfly (Greta oto) features transparent wings with remarkable low reflectance even for large view angles . This omnidirectional anti-reflection behavior is caused by small nanopillars covering the transparent region of its wings. In difference to other anti-reflection coatings found in nature (moth eye, hawk moth wing, cicada wing) these pillars are not periodically arranged and feature a random height and width distribution. We analyze the specular and diffuse reflection of the surface and explain the concept of transparency by randomness. Such anti-reflective surfaces can be adapted to improve the light collection in solar cells or for efficient anti-reflection displays.
The hierarchical structures found in the scales of the black butterfly (Pachliopta aristolochia), consisting of disordered nano-holes assemblies surrounded by micrometer-spaced triangular ridges, are crucial for controlling light absorption and therefore the butterflies colors and thermoregulation properties. We studied numerically the light harvesting performance of these hierarchical structures. Based on these observations, efficient nano-patterned thin absorbers can be designed for photovoltaics applications. We show that using a lateral phase separation process enables to fabricate disordered nano-holes assemblies with tunable density and size distribution in a resist layer and onto large surfaces.
 Siddique, R. H., G. Gomard and H. Hölscher. “The role of random nanostructures for the omnidirectional anti-reflection properties of the glasswing butterfly”, Nature Communications, Vol. 6, 6909 (2015)
Hendrik Hölscher, "Bio-inspired surfaces with nano-scale structural randomness (Conference Presentation)," Proc. SPIE 10162, Bioinspiration, Biomimetics, and Bioreplication 2017, 101620R (Presented at SPIE Smart Structures and Materials + Nondestructive Evaluation and Health Monitoring: March 27, 2017; Published: 10 May 2017); https://doi.org/10.1117/12.2259907.5427096899001.
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