Ion-Specific Network Reconfiguration in Gelatin Hydrogels Enables Self-Powered Photodetection and Neuromorphic...

Soft ionic gels are promising materials for flexible optoelectronic sensors owing to their softness, transparency, and light responsiveness. However, achieving controllable regulation of device sensitivity and response speed through modulation of gel composition or molecular structure remains challenging. Here, we demonstrate that specific ion effects induce reconfiguration of the hydration-polymer network in gelatin hydrogels, thereby enabling tunable optoelectronic properties. Kosmotropic anions reinforce interfacial polarization by promoting structural ordering within the polymer-water network, resulting in highly sensitive (0.288 µW mm^-2) and fast-response (0.077 s) self-powered photodetection. In contrast, chaotropic anions disrupt network organization, enhance water disorder, and amplify photothermal-driven ion migration, leading to weak (1.44 µW mm^-2) yet slow-response (2.08 s) persistent photoconductivity. These results reveal an ion-specific hydration mechanism that governs the transition between polarization-dominated and ion migration-dominated optoelectronic behaviors. As a proof of concept, optical encryption communication and image recognition/learning are demonstrated using photodetection-mode and photosynaptic-mode devices, respectively.