Bioinspired colloidal photonic crystals with controllable wettability.

Because of the combinatorial advantage of their unique light manipulation properties and potential applications in novel optical devices, colloidal photonic crystals (PCs), the periodic arrangement of monodispersed latex spheres, have attracted interest from researchers. In particular, colloidal PCs exhibit structural colors based on interference effects within their periodic structures. The wavelength of these colors lies in the visible range, making them particularly attractive for a variety of applications. Colloidal PCs are extensively used in templating, catalysis, and chromatographic separations. Inspired by biological PCs with both structural color and specific wettability, researchers have fabricated colloidal PCs with controllable wettability as described in this Account. The wettability can be adjusted by the intrinsic roughness of colloidal crystals in combination with the tunable chemical composition of latex surfaces. Changes in the chemical composition of the latex surface under external stimuli, such as light, electricity, and heat, can reversibly control the wettability of PCs. Furthermore, the hierarchical structure of latex particles can effectively alter the water adhesive force of superhydrophobic colloidal PCs. Patterned PCs with a variety of wettabilities can be assembled using inkjet printing from well-designed latex suspensions. By combining their structural color and specific wettability, we also exemplify some of the promising applications of colloidal PCs as templates for the construction of hierarchical structures, as indicators for controllable transport of liquid droplets, and as color-based sensors for the monitoring changes in their environment. These findings offer innovative insights into the design of novel colloidal PCs and will be of great importance for further applications of these materials.