Bioinspired Unclonable 2D Photonic Crystal Patterns with Multimode Reversible Switching for Anticounterfeiting...

The growing demand for information security and product authentication presents significant challenges for anticounterfeiting technologies. Photonic crystal (PC)-based optical anticounterfeiting approaches that enable multimode dynamic color regulation are of great significance for advancing the field of high-level anticounterfeiting. However, the susceptibility to replication and reliance on responsive materials remain key limitations. Inspired by tree rings, an elaborated two-dimensional (2D) PC anticounterfeiting system was proposed in this paper. By integrating 2D PCs with concentric periodic structures using nanospheres of varying sizes with a polyethylene glycol diacrylate 200-vinyl methacrylate (PEGDA-VMA) polymer matrix, a multimodal color changing performance was realized. The resulting "tree-ring" patterns, formed in situ via controlled injection and Marangoni effects, are inherently random and irreplicable, which provide "unclonable" characteristics. The labels exhibit multi-color-switching modes (full immersion and unilateral wetting), enabling brilliant and angle-dependent structural colors without relying on fatigue-prone responsive substrates. This simplified fabrication strategy enhances verification reliability and offers a robust route for advanced anticounterfeiting applications.