Optics in the Natural World: Iridescent Colors of Butterflies and the Twisted Beetle!

Srinivasarao, Mohan

Title:

Optics in the Natural World: Iridescent Colors of Butterflies and the Twisted Beetle!

dc.contributor.author	Srinivasarao, Mohan
dc.contributor.corporatename	Georgia Institute of Technology. Microelectronics Research Center	en_US
dc.contributor.corporatename	Georgia Institute of Technology. Nanotechnology Research Center	en_US
dc.contributor.corporatename	Georgia Institute of Technology. School of Chemistry and Biochemistry	en_US
dc.contributor.corporatename	Georgia Institute of Technology. School of Materials Science and Engineering
dc.date.accessioned	2013-02-14T14:23:30Z
dc.date.available	2013-02-14T14:23:30Z
dc.date.issued	2013-01-08
dc.description	Mohan Srinivasarao presented a lecture at the Nano@Tech Meeting on January 8, 2013 at 12 noon in room 1116 of the Marcus Nanotechnology Building.	en_US
dc.description	Dr. Mohan Srinivasarao is a Professor with the School of Polymer, Textile & Fiber Engineering. Dr. Srinivasarao received his Ph.D. in Chemistry in 1990 from Carnegie Mellon University, a M.Sc in Applied Chemistry in 1981 from PSG College of Technology (University of Madras, India), and a B.Sc in Applied Science in 1979 from Madurai University, India. Dr. Srinivasarao specializes in physical chemistry of polymers, physics of nematic liquid crystals, optics of liquid crystals, rheology/rheo-optics of polymeric fluids and liquid crystals, polymer/liquid crystal dispersions, various forms of light microscopy including confocal microscopy and photon tunneling microscopy, color science, and nano-optics in the biological world (color of butterfly wings, beetles, moths, and bird feathers). Dr. Srinivasarao is a member os several professional organizations including the American Chemical Society, Materials Research Society, Optical Society of America, Society of Rheology, American Physical Society, and the American Association for the Advancement of Science. He has published several articles and papers in a variety of journals.
dc.description	Runtime: 57:55 minutes
dc.description.abstract	The study of photonics in nature contains beautiful and diverse examples of sub-wavelength structural features that create observed colors through thin layered or multilayered interference, diffraction, zero order diffraction and light scattering. In this talk I will discuss two such examples: Butterflies and Beetles, both of which attracted the attention of great scientists including Newton, Rayleigh, Michelson and Raman, among others. Structural coloration based on diffraction, multilayer reflection, cholesteric analogues or photonic crystal-like structures is pervasive especially in the world of insects. The color of Papilio palinurus results from microbowl lined with a multilayer of air and chitin. The green color is the result of color mixing of the yellow light reflecting from the bottom of the bowl and the blue light reflecting from the sides of the bowl. We have used breath-figure templated assembly as the starting point to mimic the structure of Papilio palinurus. We were able to produce microbowls which were then coated with a multilayer of alternating titanium oxide and aluminum oxide. The resulting structure exhibits the same color mixing as the original butterfly structure does. In the second part of the talk, we take a closer look at the colors produced by iridescent, metallic green beetle, Chrysina Gloriosa that selectively reflects left circularly polarized light when illuminated with unpolarized light which is observed to possess a nearly hexagonal cellular pattern on its exoskeleton. Using crystallographic concepts and Voronoi analysis of the structure present on the exoskeleton, we determine that these cells (~10 microns each) are organized with pentagons and heptagons, interdispersed typically as clusters, between hexagons. In an optical microscope, each cell appears to contain a bright yellow core, placed in greenish cell that has yellowish borders. Using confocal microscope and the auto-fluorescence of the exoskeleton matrix, we visualize that these cells consist of nearly concentric, nested arcs that lie on surface of a shallow cone. The observed textures are reminiscent of the texture of a cholesteric liquid crystalline phase with a free surface, and present an interesting analogy that provides the basis for structure and color present on beetles.	en_US
dc.embargo.terms	null	en_US
dc.format.extent	57:55 minutes
dc.identifier.uri	http://hdl.handle.net/1853/46186
dc.language.iso	en_US	en_US
dc.publisher	Georgia Institute of Technology	en_US
dc.relation.ispartofseries	Nano@Tech Lecture Series
dc.subject	Material science	en_US
dc.subject	Nanotechnology	en_US
dc.subject	Optics	en_US
dc.title	Optics in the Natural World: Iridescent Colors of Butterflies and the Twisted Beetle!	en_US
dc.type	Moving Image
dc.type.genre	Lecture
dspace.entity.type	Publication
local.contributor.author	Srinivasarao, Mohan
local.contributor.corporatename	Institute for Electronics and Nanotechnology (IEN)
local.relation.ispartofseries	Nano@Tech Lecture Series
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