Bright-white beetle scales optimise multiple scattering of light
Nature Publishing Group
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Whiteness arises from diffuse and broadband reflection of light typically achieved through optical scattering in randomly structured media. In contrast to structural colour due to coherent scattering, white appearance generally requires a relatively thick system comprising randomly positioned high refractive-index scattering centres. Here, we show that the exceptionally bright white appearance of Cyphochilus and Lepidiota stigma beetles arises from a remarkably optimised anisotropy of intra-scale chitin networks, which act as a dense scattering media. Using time-resolved measurements, we show that light propagating in the scales of the beetles undergoes pronounced multiple scattering that is associated with the lowest transport mean free path reported to date for low-refractive-index systems. Our light transport investigation unveil high level of optimisation that achieves high-brightness white in a thin low-mass-per-unit-area anisotropic disordered nanostructure.
We wish to thank R. Blumenfeld, T. Svensson, R. Savo and K. Vynck for fruitful discussions, B.D. Wilts for the comments on the manuscript and J. Aizenberg for support in the SEM measurements. The research leading to these results has received funding from the European Research Council under the European Union’s Seventh Framework Programme (FP7/2007–2013)/ERC grant agreement n  and USAF grant FA9550-10-1-0020
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Error in funder statement in this article is corrected in http://hdl.handle.net/10871/22212
Vol. 4: 6075
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