Reconfigurable Grating Diffraction Structural Color in Self-Assembled Colloidal Crystals

Abstract

Self-assembled colloidal crystals display structural colors due to light diffracted from their microscale, ordered structure. This color arises due to Bragg reflection (BR) or grating diffraction (GD); the latter mechanism is much less explored than the former. Here the design space for generating GD structural color is identified and its relative advantages are demonstrated. Electrophoretic deposition is used to self-assemble crystals with fine crystal grains from colloids of diameter 1.0 µm. The structural color in transmission is tunable across the full visible spectrum. The optimum optical response—represented by both color intensity and saturation—is observed at low layer number (≤5 layers). The spectral response is well predicted by Mie scattering of the crystals. Taken together, the experimental and theoretical results demonstrate that vivid grating colors with high color saturation can be produced from thin layers of micron-sized colloids. These colloidal crystals extend the potential of artificial structural color materials.Structural color in nature is generated by two primary mechanisms—Bragg reflection (BR) and grating diffraction (GD). Yet, the use of self-assembly to produce artificial materials with GD structural color lags relative to those based on BR. Here is demonstrated prismatic, GD structural color in thin films of latex colloidal crystals, as produced by electrophoretic deposition.