Structural colour in animals—simple to complex optics

Over the past 30 years, optics well known to the physicist have been identified in their multitudes in nature. Multilayer reflectors, diffraction gratings, liquid crystals and structures that scatter light—devices explained using “simple” optical theory—have been found in animals with a diversity of designs. For many years the potential to employ these designs commercially has been clear, although only one optical device in animals has been taken through to the manufacture stage—the fly-eye antireflector. Now, with the beginnings of “complex” optical study in biological specimens, and consequent identification of photonic band gaps, animal reflectors are being taken seriously as promising first stages in the design process of optical engineers. However, natural photonic crystals are often highly complex structures at the nano-scale that may lie beyond the limits of current engineering. This in turn justifies the study of cellular engineering—maybe we can also exploit the flawless processes of manufacture employed by animals.