Bright-White Beetle Scales Optimise Multiple Scattering of Light

Year: 2014

Authors: Burresi M., Cortese L., Pattelli L., Kolle M., Vukusic P., Wiersma D. S., Steiner U., Vignolini S.

Autors Affiliation: European Laboratory for Non-linear Spectroscopy (LENS), Universita` di Firenze, 50019 Sesto Fiorentino (FI), Italy; Istituto Nazionale di Ottica (CNR-INO), Largo Fermi 6, 50125 Firenze (FI) Italy;
Universita` di Firenze, Dipartimento di Fisica e Astronomia, 50019 Sesto Fiorentino (FI), Italy;
School of Engineering and Applied Sciences Harvard University 29 Oxford St., Cambridge, MA, 02138, USA and Department of Mechanical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA; Thin Film Photonics, School of Physics, Exeter University, Exeter EX4 4QL, UK;
Cavendish Laboratory, Department of Physics, University of Cambridge, J. J. Thomson Avenue, Cambridge CB3 0HE, U.K;
Department of Chemistry, University of Cambridge Lensfield Road, Cambridge CB2 1EW UK

Abstract: 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.

Journal/Review: SCIENTIFIC REPORTS

Volume: 4      Pages from: 6075  to: 6075

More Information: 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 [291349] and USAF grant FA9550-10-1-0020.
KeyWords: Biophysics; Optics and photonics; Optical physics; Biological physics; Butterfly scales; Chitin, Animal; Anisotropy; Beetle; Color; Light; Metabolism; Physiology; Radiation scattering; Refractometry, Animals; Anisotropy; Beetles; Chitin; Color; Light; Refractometry; Scattering, Radiation
DOI: 10.1038/srep06075

Citations: 157
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