Biogenic Scatterers, Mirrors, Multilayer Reflectors and Photonic Crystals. Futuristic Ancient Technologies*

Organisms are able to construct an array of optical “devices” including diffuse scatterers, broadband reflectors, tunable photonic crystals and mirrors by varying the size, morphology and arrangement of organic crystals. These “devices” perform a variety of optical functions, such as generating the white color of certain spiders, the metallic silvery reflectance of fish scales, the brilliant iridescent colors of some copepods, and mirrors used for vision in animal eyes (1). Scallops have tens of eyes, each containing a concave multi-layered mirror tiled with a mosaic of square guanine crystals. The mirror forms images on a double-layered retina (2, 3). Shrimp, crayfish and lobsters possess compound eyes that also use reflective optics, and contain two sets of mirrors, composed of a previously unknown biogenic crystal – isoxanthopterine. The two mirrors have very different ultrastructures and functions that we can rationalize in terms of the optical performance of the eye. In all these examples, the hierarchical organization is controlled from the component crystals at the nanoscale to the complex 3D morphology at the millimeter level.

1) D Gur, BA Palmer, S Weiner, L Addadi, Adv Funct Mater 2017, 1603514
2) A Hirsch, BA Palmer, N Elad, D Gur, S Weiner, L Addadi, L Kronik, L Leiserowitz, Angew Chem 2017, 56, 1.
3)BA Palmer, GJ Taylor, V Brumfeld, D Gur, M Shemesh, N Elad, A Osherov, D Oron, S Weiner, L Addadi, Science, in press.