Physical Unclonable Anti‐Counterfeiting “Watermarks” Via Swelling‐Induced Buckling‐Delamination in Polymer Bilayers for Portable and Robust Authentication

Abstract Conventional anti‐counterfeiting labels, primarily fabricated through deterministic processes, are inherently vulnerable to sophisticated counterfeiting attacks. Physical unclonable functions (PUFs), leveraging intrinsic non‐deterministic characteristics, have emerged as a promising hardware‐based solution for high‐security applications. This work presents a novel anti‐counterfeiting label that bridges the time‐honored watermarking concept with cutting‐edge PUF technology. By harnessing surface buckling‐delamination instabilities via a facile one‐step water‐swelling approach on poly(vinyl alcohol)/polydimethylsiloxane (PVA/PDMS) bilayers, millimeter‐scale PUF watermarks are fabricated that mimic natural leaf vein morphologies. These watermarks exhibit critical attributes including randomness, irreversibility, uniqueness, and irreproducibility, which are fundamental to anti‐counterfeiting efficacy. Additionally, they offer tunable control over pattern dimensions, shapes, and encoding capacities, accommodating diverse security level requirements. Furthermore, the watermarks exhibit fingerprint‐like minutiae and compatibility with computer‐vision‐based feature‐matching algorithms, enabling accurate and efficient authentication/identification using portable devices (e.g., smartphones and flatbed scanners) without relying on costly instrumentation. Moreover, the encapsulated watermark patterns demonstrate excellent durability under rigorous tests, such as UV irradiation, water immersion, and high‐temperature exposure, validating their superior environmental adaptability. Notably, this transparent and flexible label can be easily integrated onto various real‐world objects without compromising their visual appearance and normal use.