Structure, Function, and Self-Assembly of Single Network Gyroid (I4132) Photonic Crystals in Butterfly Wing Scales
biological meta-materials, organismal color, biomimetics, biological cubic mesophases
Small angle X-ray scattering (SAXS) was used to identify the 3D photonic nanostructures (made of chitin and air) of five butterfly species from two families (Papilionidae, Lycaenidae) as single network gyroid (<math>I4_132</math>) photonic crystals. Photonic band-gap modeling was also performed. Butterflies first develop thermodynamically favored double gyroid precursors and transform these into a single gyroid network which is optically more efficient.
Results and Discussion
A periodic variation in the refractive index on the order of visible wavelengths gives butterflies its structural colors. Pinhole synchrotron small angle X-ray scattering (SAXS) has been used to investigate natural photonic materials with mesoscale (150–350 nm) scattering features. The order of the lattice constant in these cases require small scattering angles and advanced X-ray optics. Five butterflies species were tested: Parides sesostris, Teinopalpus imperialis, (Papilionidae); Callophrys (formerly Mitoura) gryneus, Callophrys dumetorum, and Cyanophrys herodotus (Lycaenidae).