Princeton University Department of Physics Colloquium

ABSTRACT: In addition to molecular pigments, many organisms create colors for communication and camouflage using optical nanostructures. Color production by interference from thin films and diffraction gratings has been easily understood, but understanding color production by other biological nanostructures that lack regular crystalline periodicity has been a challenge. Fourier analysis and small-angle X-ray scattering reveals that these quasiordered, or aperiodic , nanostructures from bird feathers and insect scales have sufficient local order to produce structural colors by interference, but unlike most interference colors, these colors lack iridescence. A second challenge has been to understand the development of bio-optical nanostructures, which are too large to be explained by traditional molecular biology and too small for developmental biology. We are investigating the role of soft condensed matter physics in the self-assembly of two classes of bio-optical nanostructures: arrested phase separation in spongy beta-keratin nanostructures of blue bird feathers, and the membrane folding energetics in scales of butterflies, beetles, and bees. Understanding the optics and self-assembly of these nanostructures provides new insights into their communication functions and evolution.