Ionic Hydrogel-Based Solid-State Electrolyte for Versatile High-Resolution Light-Addressable Electrochemical Imaging and Sensing

Conventional light-addressable electrochemical (LAE) imaging relies on liquid electrolytes, which suffer from fluid leakage and poor immobilization of nonadherent analytes. Here, we introduce a robust, solid-state LAE platform utilizing ionic hydrogels that serve concurrently as ion-conducting electrolytes and stable encapsulation matrices. Photocurrent measurements reveal that the proposed α-Fe2O3/hydrogel electrolyte interface shows photoelectrochemical behavior comparable to liquid controls, achieving a lateral spatial resolution of ∼2.5 μm. By tuning hydrogel properties, biocompatible, soft agarose enables nondestructive mapping of both adherent and suspension cells, while mechanically reinforced polyacrylamide facilitates precise profiling of rigid microparticles. Coupled with an in situ gelation strategy, this platform achieves high-resolution mapping of heterogeneous tissue sections. Furthermore, a multichannel sensing array enables parallel, quantitative enzymatic sensing of multiple biochemical targets (e.g., urea and glucose with different concentrations) on a single substrate. This ionic hydrogel-assisted interfacial strategy expands the operational scope of LAE toward diverse sample types and establishes a universal platform for advanced solid-state photoelectrochemical imaging and sensing.