Fourier blues: Structural coloration of biological tissues

Abstract

The non-pigmentary colors of the tissues of living organisms are produced by the physical interaction of light with nanostructures in the tissues. Contrary to what has been previously assumed for many decades, it has been established now that many of the beautiful blue and green colors observed in the tissues of mammals, birds, and butterflies are the result of coherent scattering or constructive interference. Using Fourier analysis one can show that many structurally colored tissues are quasi-ordered on the appropriate nanoscale to produce the observed colors by constructive interference. Understanding the mechanisms of coloration in animals is very important because of the role that bright colors play in communication, courtship display, and mate selection in many species of the animal kingdom. In this note we give an exposition of some of the extensive work done recently on nanomaterials with noncrystalline, local scale order. The focus of this article is, in particular, on a truly fascinating manifestation of Fourier analysis and synthesis in nature, which provides a way to explain coloration phenomena that are of interest in behavioral and evolutionary biology.