Piezochromic hydrogels for physically unclonable optical anti-counterfeiting with machine-learning assisted automatic identification

Developing high-security anticounterfeiting with reliable authentication remains a significant challenge in preventing information leakage and economic losses from counterfeiting. Here, we successfully reported physically uncopiable optical system based on piezochromic polymer hydrogels (PPH). Pressure treatment induces a clustering-triggered emission transition from red to blue, driven by suppressed through-space interactions and reduced electron delocalization, with the blue-emissive state stably retained after pressure release. Stochastic spatial distribution of red- and blue-emissive particles generates physically unclonable patterns with high distinguishability. Statistical analysis reveals near-ideal randomness together with high uniqueness and reliability. A similarity-based machine learning framework enables rapid and robust authentication, overcoming the subjectivity and inefficiency of human-eye recognition. This work establishes piezochromic polymer hydrogels as a platform for physically unclonable optical systems for secure anti-counterfeiting. Development of materials for anticounterfeiting is challenging, with high levels of complexity required. Here, the authors report the development of piezochromic polymer hydrogels with the optical properties from clusteroluminescence effects allowing patterning for physically unclonable functions.