Small Angle X-ray Scattering of Single Network Gyroid (I4132) Photonic Crystals In Butterfly Wing Scales

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Written by: Grant England AP225 Fall, 2011

Info

Title: Small Angle X-ray Scattering of Single Network Gyroid (I4132) Photonic Crystals In Butterfly Wing Scales

Authors: Vinodkumar Saranathana, Chinedum O. Osujib, Simon G. J. Mochrieb, Heeso Nohb, Suresh Narayananf, Alec Sandyf, Eric R. Dufresneb, and Richard O. Pruma

@Harvard: http://www.pnas.org/content/early/2010/06/11/0909616107.full.pdf

Summary

This paper describes the physical and optical characterization of the three dimensional photonic crystal structures found in a few different types of butterflies. By using various measurement and modeling techniques, they were able to determine the crystal structure found in such butterflies and used in the creation of structural color in the insects used for communication and signaling. The method for creating such structures could serve as an inspiration for methodologies to create artificial photonic crystal structures with the same symmetries.

Methods and Results

It was found that the butterflies exhibited a gyroid structure with approximately racemic chirality. The gyroid is from the I4132 space group and is fabricated by the butterfly in its development first by creating a double gyroid structure which is more thermodynamically favorable and then letting one of the interpenetrating gyroid structures die and dissolve, leaving only the more optically favorable single gyroid. Some of the different photonic crystal structures can be seen in the figure below with both optical and SEM images.

Butterflyscales.jpg

In addition a movie visualizing the gyroid structure can be found at this link: http://www.pnas.org/content/suppl/2010/06/14/0909616107.DCSupplemental/SM01.avi

Conclusions and Link to Soft Matter

This paper may be somewhat of a stretch for the surfactants, so the link should be explained. Double gyroid structures are one of the space groups of crystals which can be fabricated by using surfactant solutions (see http://www.ncbi.nlm.nih.gov/pubmed/19957975). So, once the photonic properties of such crystal structures are well understood, surfactants could be utilized to fabricate bio-inspired photonic crystal structures.