Laser‐Programmed 3D Gradient Architectures in Transparent Polymer Films for Dynamic Information Encryption and Anti‐Counterfeiting

Abstract Transparent polymer films face critical limitations in dynamic information encryption, including irreversible transparency loss, simplistic encrypted patterns, and the absence of active security mechanisms. To overcome these, this study proposes a laser‐programming strategy using polyvinyl alcohol composites synergistically doped with carbon nanotubes (50 ppm) and glucose monohydrate (4 wt%). This system maintains > 60% transmittance while enabling cross‐dimensional structural and chromatic responses: low‐energy irradiation induces 2D translucent whitening via grain‐boundary scattering (Δ E = 3.04–14.96); medium energy triggers milky‐white 3D foaming with 1162 µm height differential; high energy drives gradient carbonization (from charred yellow to brown, Δ E = 26.66–42.98). Leveraging precise energy‐threshold control, this study develops dual encryption paradigms: 1) Hydro‐triggered concealment/laser decryption enables water‐driven reversible erasure (>95% transmittance recovery) with selective background whitening for “opaque‐background/transparent‐message” revelation; 2) Dual‐laser‐threshold encryption combines sub‐threshold invisible writing (<5% transmittance variation) and localized foaming/carbonization development. Both integrate auto‐destruct security, where supra‐critical energy irreversibly destroys data. The film exhibits exceptional stability (abrasion/bending/aging resistance) and dynamic optical/tactile feedback, providing mask‐free single‐step fabrication of high‐security anti‐counterfeiting features that bridge transparent‐substrate encryption from concept to practical applications.