Living Photonic Devices: Protein Self-Assembly of Optical Materials in Mollusks

Molluscan animals such as squids, octopuses and clams build an array of living optical devices of astounding optical/photonic sophistication and complexity, such as structural camouflaging coatings, graded index lenses, solar radiance distributors, and wavelength-specific light guides. Unlike the iridescent structures in fish, butterflies and birds, the "iridocytes" in molluscs are formed from still-living cells, with the high-index portions generated by dense assemblies of protein in the active cytoplasm. These optically resonant cells seem to be allowed more structural diversity than systems in other taxa, and have evolved to solve a wider array of evolutionary optical problems than in any other animal group, such as underwater vision, emissive camouflage, reflective camouflage, and distribution of light for efficient photosynthesis. Several new observations about reflectin proteins and S-crystallins from squids show that the soft matter physics construct of "patchy colloids" is the most informative paradigm for understanding assembly of these living photonic systems. This talk will discuss our recent discoveries of optical function and self-assembly in squid vision, squid camouflage, and "solar transformers" in mollusks.