Paper‐Structure Inspired Multiresponsive Hydrogels with Solvent‐Induced Reversible Information Recording, Self‐Encryption, and Multidecryption

Abstract Information recording and encryption/decryption functions are essential due to the prevalence of counterfeiting activities and information leakage in the current age. However, the development of high‐resolution information recording and multistage information protection systems to achieve high data security levels, such as self‐erasing encrypted data and time‐controlled data handling, remains limited. Herein, inspired by the information‐recording structure of paper, a multiresponsive nanofiber‐reinforced poly(N‐isopropylacrylamide) (PNIPAM) hydrogel (NCPN hydrogel) with improved mechanical properties, solvent‐induced high‐resolution reversible information recording, self‐encryption, and multi‐decryption capabilities, is proposed. Due to the unique hydrophilic and hydrophobic structures of the hydrogel matrix, ethanol and other polar analogs can be applied as special inks to record information by changing the lower critical solution temperature to achieve the repeatable transmittance variation. The recorded information can be erased via water wiping or ethanol volatilization. Additionally, self‐encryption can be achieved and adjusted based on the ethanol volatilization time and concentration difference, and confidential information can be further decrypted in a water environment or under a thermal stimulus. Furthermore, several stable, repeatable, and fast‐response hydrogel‐based information‐recognition systems are designed and investigated. Therefore, the designed hydrogel‐based informational platform provides a universal information‐handling system allowing for the reversible recording of information, with self‐encryption and multidecryption capabilities.