Flexible structural color label with tetra-mode iridescence in full three-dimensional space for sophisticated anti-counterfeiting

Abstract

The attractive visual appearance provided by disordered surfaces has been proven, which demonstrates great anticounterfeiting potential. However, the real application is challenging due to complex processing and Si substrates. We fabricated flexible structural color anti-counterfeiting labels by printing ZnS spheres onto aluminized flexible films to form a disordered surface, resulting in specular-diffuse dual modes appearances. Especially, based on the directionality of Mie scattering, the diffuse mode displayed three-dimensional (3D) angle-dependent structural colors under ambient light and exhibited angle-sensitive dynamic structural colors in 3D space under the light source. The angle dependence of the specular mode and the 3D iridescent of the diffuse mode form a tetra-mode iridescence, which brings sophisticated anti-counterfeiting. The comprehensive color information is directly determined by the optical properties of ZnS and Al, which pose challenges for replication using alternative methods. Further, labels with multi-color dragon patterns were fabricated using ZnS spheres with different diameters, which greatly improves information security. More importantly, based on the tetra-mode, a verification method compatible with personal terminals has been developed, which can quickly identify authenticity.