An Optically Modulated Hydrogel Synapse for Multilevel Information Decryption

Abstract The increasing significance of data security promotes the development of multilevel information encryption and decryption techniques. However, the realization of logical outputs modulated by multiple stimuli is challenging in the design of advanced functional materials. Herein, a multilevel information decryption system with a combination of visual and digital outputs that responds to dual‐optical inputs is developed based on a hydrogel‐based synaptic device. ammonium molybdate nanoparticles and calcium alginate supramolecular networks is incorporated into a polyacrylamide hydrogel to enable optically regulated color change and ionic conductivity. Under UV irradiation, the reduction of the nanoparticles allows the hydrogel to change color as visual outputs. Meanwhile, the ionic conductivity of the hydrogel can be modulated by near‐infrared (NIR) optical pulses to emulate the synaptic plasticity of biological synapses, producing NIR‐mediated digital outputs. As a demonstration, a multilevel decryption strategy is provided using a hydrogel array that combines digital information decoding with visual information camouflage. Moreover, the short‐term plasticity of the hydrogel synapse endows the system with time‐dependent decryption, which improves information security and reduces the risk of data leakage. This study contributes to advancing multilevel decryption systems by providing an effective technique for integrating digital and visual decryption in hydrogel materials.