Color-Tunable Elastic Photonic Shells with High Color Saturation and Deformability

Abstract

Photonic microspheres containing colloidal arrays are useful as structural colorants in inks and cosmetics. However, low color saturation and low deformability of the microspheres restrict the uses. To overcome the limitations, elastic photonic shells with enhanced color saturation and high deformability using water-in-oil-in-water (W/O/W) double-emulsion templates are designed. The elastic shells are produced by photocuring acrylate-based resin containing non-close-packed arrays of silica particles in the middle oil layer. The presence of two concentric interfaces and water-soluble molecules in the inner and continuous water phases at high concentrations improve the crystalline order of silica particles. In addition, the absence of a relatively disordered core reduces incoherent random scattering, thereby enhancing color saturation. Although the shells themselves are elastically deformable, the liquid core renders them significantly more deformable with small stiffness and negligible hysteresis, which is potentially beneficial for improving the fluidity of suspensions. Moreover, the structural colors of the elastic shells are post-tunable by osmotic inflation of the semipermeable shells in hypotonic conditions. The high color saturation and high deformability as well as color tunability will provide a new opportunity for structural coloration with the elastic photonic shells as a colorant in inks and cosmetics.