Butterfly Wings: Nature’s Fluttering Kaleidoscope

Abstract

The butterfly amazes people not just for its beautiful, kaleidoscope-like appearance but also its potential for mimicry, which is evident in its high adaptability in various kinds of environments. Each butterfly has a particular wing structure and corresponding living habit. Although their iridescent colors attract the most attention, other characteristics like their anti-wetting property and heat dissipation due to their special surface structure are also interesting and inspiring. On the micro-scale, we see that the wings of butterflies are not as smooth as they seem; SEM observations show that the wing surface is covered by a large number of quadrate scales that overlap each other and are orderly arranged along the radial outward (RO) direction. Once magnified to the nano-scale level, research revealed that each scale consisted of ridging stripes that could be further split into multiple layers separated by air (Zheng et al.. Soft Matter 3:178–182, 2007). The iridescent effect observed in many species of butterflies is the product of the periodical multi-layers of their scales, which give rise to multiple internal reflection, refraction, and interference events (Herring, Comp Biochem Physiol A Physiol 109(3):513–546, 1994). Like lotus and rice leaves, butterfly wings are superhydrophobic, which enable them to keep their wings clean and dry (Zheng et al., Soft Matter 3:178–182, 2007). Butterfly wing replication has been explored by the scientific community in order to reproduce these outstanding properties. Dai et al. proposed a procedural texture generation approach using traits of iteration behavior to achieve the surface texture of butterfly wings (Dai et al., Visual Comput 11(4):177–187, 1995). SiO₂ inverse structure replicas using butterfly wings as templates in a sol-gel process have been attempted as well (Xu et al., Nano Res 4(8):737–745, 2011). Finally, Kang et al. used a molding lithography technique to fabricate a polydimethylsiloxane (PDMS) replica of the multi-layered scales on the upper surface of a Morpho butterfly (Kang et al., Curr Appl Phys 10(2):625–630, 2010).