Schizophrenic Shape Memory Hydrogel with Hidden Morphological Information for Transient Encryption

Inspired by sign language, responsive materials construct an efficient encryption channel via programmable shape morphing, offering a potential solution to the decryption vulnerabilities of existing optical anticounterfeit. However, these pioneering approaches often fail to conceal morphological information due to predictable shape-shifting, let alone achieve higher-level encryption such as multiple and transient information storage. Herein, we report a schizophrenic shape memory hydrogel that can be applied for transient information encryption. In particular, two opposite shape fixation mechanisms, heating-induced aggregation of poly(acrylic acid)-Ca 2+ (PAAc-Ca 2+ ) coordination and cooling-induced clustering of alkyl chain-modified poly(vinyl alcohol) (PVA-C6), are coupled in one system. Through a two-step shape programming process involving alternating heating and cooling, complex morphological information can be hidden within an initially simple shape. During its temperature-triggered shape morphing process, the hydrogel rapidly undergoes shape-shifting to reveal the hidden morphological information, followed by an onset recovery to erase it, thereby achieving a transient information display. This single-triggered multiple shape-shifting system opens an unprecedented pattern-independent channel for existing encryption strategies and can motivate the development of advanced anticounterfeiting materials with integrated multifunctionality.