A stimuli-responsive hydrogel for reversible information storage, encryption and decryption

Smart hydrogel materials, known for their sensitivity to external stimuli, exhibit a reversible dynamic response and find applications in diverse fields, particularly in information storage. Despite significant efforts in this domain, developing a hydrogel with high-resolution, repeatable recording, and robust information encryption/decryption capabilities still remains a challenge. In this study, we synthesized a polymer hydrogel, namely polyvinyl alcohol-n-isopropylacrylamide-octadecyl polyoxyethylene ether acrylate hydrogel (PPNS), which features multiple hydrogen bonds through copolymerization, by using N-isopropylacrylamide, polyvinyl alcohol, and octadecyl polyoxyethylene ether acrylate (SGA₁₅) as raw materials. The PPNS hydrogel demonstrated outstanding high-resolution, repeatable recording capabilities, enabling reversible recording, encryption, and decryption of information using anhydrous ethanol as the inducer. Varying the SGA₁₅ monomer concentration revealed that the PPNS-2% hydrogel, prepared with 2% SGA₁₅, outperformed the other hydrogels in terms of information recording and encryption/decryption when immersed in anhydrous ethanol and deionized water. Furthermore, the PPNS-2% hydrogel exhibited the ability to undergo multiple information cycles while maintaining excellent mechanical properties even after 25 cycles. Notably, ethanol served as a specialized ink for inscribing different patterns on the hydrogel surface for information recording. The recorded information could be erased through water wiping or ethanol volatilization, enabling reversible information recording, encryption, and decryption. Due to their responsive and dynamic nature of PPNS hydrogels are positions them as promising candidates for use as innovative information storage platforms.