Bio-Inspired Structural Color Irises as Physical Unclonable Functions for Anti-Counterfeiting.

The global proliferation of high-value commodities has the intensified demand for advanced anti-counterfeiting solutions. Physical Unclonable Functions (PUFs) present a viable authentication mechanism, yet existing implementations exhibit three critical limitations: suboptimal authentication accuracy, insufficient multi-level security architecture, and dependence on costly and specialized equipment for verification. To address these issues, this work utilizes colloidal photonic crystals to fabricate PUF anti-counterfeiting patterns spanning from the macro-to-micro scale. These patterns are integrated with the iris recognition algorithm to construct a multi-layered optical anti-counterfeiting system based on the structural color iris. This work experimentally and computationally demonstrates that the "Ring"-type colloidal photonic crystals originate from the "coffee ring" effect. By modulating the "coffee ring" effect, the size of the colloidal photonic crystal iris patterns can be controlled, enabling switching between "Ring"-type and "Dot"-type colloidal photonic crystals. Furthermore, multiple characteristic parameters confirm that the PUF codes derived from encoded "Ring"-type colloidal photonic crystal images exhibit uniqueness and readability. Finally, a multi-layered anti-counterfeiting system is constructed, comprising three components: structural color patterns, embedded "Morse codes" formed by "Ring"-type and "Dot"-type colloidal photonic crystals, and optical PUF labels based on the "Ring"-type colloidal photonic crystals. This cost-effective system enables low-threshold, high-performance structural color anti-counterfeiting for premium products.