Seminar Thursday Nov. 16, 2011 1:30 pm 129NH

1. NEBRASKA CENTER FOR MATERIALS AND NANOSCIENCE AND CENTER FOR NANOHYBRID FUNCTIONAL MATERIALS Seminar Thursday Nov. 16, 2011 1:30 pm 129NH Structural Characterization of Cuticles of Scarab Beetles using Mueller-Matrix Spectroscopic Ellipsometry Prof. Dr. Hans Arwin Department of Physics, Chemistry and Biology, Linköping UniversitySE581 83 Linköping Sweden Many scarab beetles exhibit astonishing structural colors and polarization phenomena including elliptic/near circular polarization in reflected light. Electron microscopy studies reveal that the cuticles of these beetles contain complex layered or chiral structures. From an applications point of view it is of large interest to explore these nanostructures as inspiration for biomimetic design. In this work, a dual-rotating compensator ellipsometer is used in the spectral range 300-1000 nm to determine Mueller matrices of cuticles of several scarab beetle species. Coptomialaevis is blue/green and represents a beetle without a chiral nanostructure as observed by its small m41 Mueller-matrix element. Cetoniaaurata has a narrow-band reflection with large m41 values. The color varies from green to greenish/reddish among species and displays strong left-handed polarization. Anoplognathusfrenchi is goldish and has a broad-band reflection with large values on m41. Some beetles are also found to reflect right-handed polarization at certain wavelengths and angles of incidences. The spectral Mueller-matrix data are used for modeling the nanostructure of beetle cuticles involving dielectric surface layers and heliocoidal “Bouligand” structures. Using non-linear regression, parameterization in terms of layer thicknesses, refractive indices and pitch of the helix in cuticle structures is performed. It is found that a pitch distribution is needed to describe the measured data. Seminar hosted by Dr. M. Schubert, Department of Electrical Engineering