Direct Writing of Structurally-Colored 3D Architectures Using Bingham Colloidal Inks

Abstract

Photonic glasses generate less iridescent and diffusive structural colors (SC) from nanostructures that are periodic only in short-range order, unlike highly crystalline photonic crystals with iridescent SC. There have been almost no attempts to create 3D structures with SC as it is difficult to crystallize particles as well as stack the structures. Here, we suggest direct-writing of photonic-glass 3D structures using ethanol-mediated colloidal dispersion. Silica particles form hydrogen bonds with acrylate polymer in the dispersion, and a small amount of ethanol hinders the bond so that the resultant linkage between particles leads to high storage modulus and stackable property of the dispersion. The dispersion is direct-written rapidly as fast as 20 mm/s and SC is exhibited after ethanol evaporation. This strategy has a high degree of freedom in substrate types, the number of colors, and design. It suggests a new way of designing and information storage with permanent SC in 3D spaces.