A polymer thin film of appropriate thickness may display structural color, independant of the polymer's intrinsic electronic absorption color. Light striking a thin film reflects from the film surfaces and penetrates through the film and reflects from the underlying substrate. The hues of these films shift according to Bragg's Law, in which the optical path length distance, d, is a function of film thickness and index of refraction. Based upon d, light emerging from the film posesses a particular phase that may constructively or destructively interfere with an adjacent beam of light being reflected at the air-film interface. By varying the speed at which thin films are spun onto substrates, it is possible to control film thickness and film color.

These biopolymer thin films exhibit different reflected colors. These films are composed of the same material, and differ only in their thickness.

Thin film analysis is carried out with a spectroscopic ellipsometer and a fiber optic reflectance spectrometer system.