Biphasic Polyampholyte Hydrogel for Rewritable 3D Encryption Enabled Via Pressure and Solvent Exchange

3D encryption is an advanced cryptographic technique that integrates concurrent information and shape encryption in a single unit. However, traditional 3D encryption systems suffered complex decryption proces with multiple triggers for decryption, due to their separated keys for shape decryption and information decryption. Herein, we propose polyampholyte hydrogels with biphasic structures for rewritable 3D encryption. The phase separation of polyampholyte hydrogel was triggered by pressure and solvent exchange, resulting in opaque patterns. Owing to the sea-island structure of quaternized polyrotaxane-modified polyampholyte (QRPA) hydrogel, 3D encryption could be achieved by shaping the patterned hydrogel and fixing in DMSO. Importantly, the one-step decryption was accomplished by immersing the 3D encrypted hydrogel in water, where the deformed hydrogel reverted to its original shape and simultaneously displayed the hidden patterns. Besides, the QRPA hydrogels were rewritable and multiple-shape programmable for complex 3D encryption. We constructed a new 3D encryption system that can be decrypted with a single step or multilevel security, showcasing its potential in advanced encryption.