Tuning Disorder in Structurally Colored Bioinspired Photonic Glasses

Colloidal crystals, such as opals, display bright and iridescent colors when assembled from submicron
particles. While the brightness and purity of iridescent colors are well suited for ornaments, signaling,
and anticounterfeiting, their angle dependence limits the range of their applications. In contrast,
colloidal glasses display angle-independent structural color that is tunable by the size and local
arrangement of particles. However, the angle-independent color of colloidal photonic glasses usually
yields pastel colors that are not vivid due to the disorder in the particle assembly. Here, we report an
electrophoretic assembly platform for tuning the level of disorder in the particle system from a colloidal
crystal to a colloidal glass. Altering the electric field in our electrophoretic platform allows for deliberate
control of the assembly kinetics and thus the level of order in the particle assembly. With the help of
microscopy, X-ray scattering, and optical characterization, we show that the photonic properties of the
assembled films can be tuned with the applied electric field. Our analyses reveal that angle-independent
color with optimum color brightness can be achieved in typical colloidal suspensions when the range of
order is at ~3.2 particle diameters, which is expected at a moderate electric field of 15 V/mm.
.