The generation of color in living systems is often, but not always, due to pigments. Especially in beetles and butterflies, color or color effects such as iridescence can also be caused by complex spatial nanostructures, with periodicity commensurate with visible light, that act as a photonic crystals. We here discuss a particular ordered and chiral nanostructure, called the single gyroid, with the topology of a triply-periodic network or labyrinth. The single gyroid is present as a porous chitin matrix in the wing-scales of a number of green butterflies, including the green hairstreak and the Kaiser-i-hind, and has been shown to contribute to the green coloration. In this talk, circular polarisation properties of the reflectance of the single gyroid are discussed. Both theory and experiments on nanofabricated replicas (at larger length scales) show that the geometric chirality of the single gyroid leads to circular polarisation in the reflected light. However, no significant circular polarisation signal is observed in reflections from the butterfly wings. This finding is discussed in the context of likely origins of the single gyroid in the butterfly.

Dr Schröder-Turk graduated from the University of Cologne with a Master degree in physics in 2000, with his thesis work addressing the statistical physics of models for magnets and flux line lattices with quenched disorder. He then, by a stroke of very good luck, ended up at the Department of Applied Maths at the ANU to pursue postgraduate studies, and was awarded a PhD from the ANU in 2005. His PhD research addressed the formation mechanisms of ordered bicontinuous phases in lipid or copolymeric self-assembly, from a geometric perspective. These softmatter phases, with long-range order and labyrinth-like spatial structure, have remained a focus of his research ever since. In 2006, he moved to the university of Erlangen-Nuremberg in Germany where he is conducting research on complex structure in softmatter, using geometry and morphology to address their physical properties (mechanical, photonic, etc) and their formation mechanisms.

Please join us for wine and nibbles after the Seminar in the RSPE Tearoom