Bioinspired Multi‐Grating Photopolymer for TIR/Vis Dual‐Mode Anti‐Counterfeiting

This work reports a multi‐grating‐based polymer device for visible/thermal‐infrared (TIR) dual‐mode information encryption. We demonstrate a convenient microstructure nested transfer strategy combining photopolymerization processes to fabricate multi‐grating structures. Inspired by Rosalia alpina longhorn beetle elytra, the multi‐grating microstructures generate distinct wavelength‐dependent optical responses. Numerical simulations reveal that the grating period plays a critical role in tuning the electromagnetic field distribution and emissivity. Mechanistically, compared with large‐period gratings or flat surfaces, a 5‐µm grating provides a more suitable grating vector G ( G = 2π / Λ , where Λ represents the grating period) for momentum matching and guided‐mode coupling, thereby resulting in an enhancement of ∼0.6% in Planck‐weighted emissivity within the TIR regime. Consequently, thermally hidden patterns become selectively revealed upon heating. Guided by this mechanism, the multi‐grating photopolymer devices with spatially programmable architectures are experimentally realized. The devices exhibit dual‐mode information encoding in visible/infrared images and further enable programmable digital anti‐counterfeiting patterns appearance under heating from 20°C to 65°C. Moreover, the photoresist templates used in the proposed fabrication strategy can be reused for multiple transfer cycles while maintaining high pattern fidelity. This work establishes a biomimetic and scalable strategy for constructing encoded infrared devices through multi‐grating structures, offering promising potential for anti‐counterfeiting and information encryption.