Colloidal Photonic Inks for Mechanochromic Films andPatterns with Structural Colors of High Saturation

Colloidal arrays show structural colors through wavelength-selective diffraction. The structural colors are dynamically tunable with mechanical deformation for nonclose-packed colloidal array embedded in an elastic matrix. However, such compositions usually render photonic materials transparent and structural color lowly saturated. In this work, we formulate colloidal inks to produce mechanochromic films and patterns that show consistent structural colors with high saturation. The inks are composed of a high-volume fraction of silica particles and a low fraction of polydopamine nanoparticles dispersed in an elastomer-forming resin. The silica particles have repulsive interparticle potential and form a nonclose-packed array, whereas polydopamine nanoparticles are positioned in the interstitial areas. The colloidal arrays are captured in elastomer by photopolymerization of the resin. As polydopamine nanoparticles reduce incoherent scattering and make the materials opaque, the structural color arisen from th...