Dynamic modulation of photonic bandgaps in crystalline colloidal arrays is achieved by application of electric field. Highly charged polystyrene particles spontaneously create the crystal lattice, which is compressed or relaxed under external electric field by electrokinetic force. As a result, structural color of colloidal crystals as a photonic bandgap can be tuned or fixed with unprecedentedly fast and precise manner.

Pixelated inverse opals with red, green, and blue colors were prepared by hybridizing convective assembly of colloidal particles and photolithography techniques. The brilliant structural colors, high mechanical stability, and small feature size of the pixels were simultaneously accomplished, thereby providing color reflectors potentially useful for display devices. Moreover, this hybridized method provides a general means to create multi-colored photonic crystals.

Amorphous colloidal array with short-range order displays noniridescent structural colors due to the isotropic nature of the colloidal arrangement. The low angle dependence renders the colloidal glasses, which is promising for various coloration applications. Nevertheless, the colloidal glasses are difficult to develop red structural color due to strong cavity-like resonance from individual particles in the blue region. To suppress the cavity mode and develop the colors in the full visible range, we prepare inverse glasses composed of amorphous array of air cavities with short-range order. To produce the structures in a simple and reproducible manner, monodisperse silica particles are dispersed in a photocurable resin of poly(ethylene glycol) dimethacrylate (PEGDMA) at a volume fraction of 0.3. The particles spontaneously form the amorphous array with short-range order, which is rapidly captured in polymeric films by photopolymerization of the resin. Selective removal of silica particles from the polymerized resin leaves behind amorphous array of air cavities. The inverse glasses display structural colors with negligible backscattering in blue due to short optical path and low index in each cavity. Therefore, the colors can be tuned in full visible range by simply controlling the cavity size. The photocurable suspensions of silica particles can be patterned by photolithography, which enables the production of freestanding films containing patterned inverse glasses with noniridescent structural colors.

Photonic microdisks with a multilayered structure are designed from photocurable suspensions by step-by-step photolithography. In each step of photolithography, either a colloidal photonic crystal or a magnetic-particle-laden layer is stacked over the windows of a photomask. Sequential photolithography enables the creation of multilayered photonic microdisks that have brilliant structural colors that can be switched by an external magnetic field.