Bioinspired Noniridescent Structural Color with Hidden Patterns for Anticounterfeiting

Abstract

Noniridescent structural colors, by virtue of their pigment-like features and simple preparation techniques, have pivotal roles in color-related applications. However, because of the wide bandwidth resulting from coherent scattering, noniridescent structural colors lack the angle-altered color feature, which plays a critical role in angle-altered colored identification of structural color. Therefore, developing a novel strategy for noniridescent structural colors in security applications remains a challenge. Inspired by Diphylleia grayi, we developed a thickness-controlled silica@polydopamine (SiO2@PDA) amorphous arrays anticounterfeiting system. Owing to the melanin absorption of PDA, the SiO2@PDA amorphous arrays exhibit visual noniridescent structural colors in air but the brownish-black color of PDA in water. More importantly, when the arrays’ thickness exceeds 9 μm, the SiO2@PDA amorphous arrays display thickness-independent structural color in air but thickness-dependent PDA (brownish-black) color in water. On the basis of this finding, any designs of patterns with uniform or multicolored structural color can be encrypted by employing the distinct thicknesses and selectively disclosed in a liquid solvent environment. We believe these simple, user-interactive noniridescent structurally colored arrays are appealing for various security-related applications, such as anticounterfeiting.