A Polyoxometalate-Based Proton-Conductive Hydrogel with Wet Adhesion for Amphibious Flexible Sensing

Amphibious flexible sensors that can operate reliably in both air and aqueous environments are of great interest for wearable electronics. However, conventional conductive hydrogels usually suffer from insufficient wet adhesion and poor conductive stability, which limit their applications in complex wet conditions. Herein, we developed a polyoxometalate-based composite proton-conductive hydrogel (CFeDW) based on chitosan (CS), FeCl 3, 2-(dimethylamino)ethyl methacrylate (DMAEMA), and Keggin-type silicotungstic acid (SiW 12 ). In this system, CS provides abundant amino and hydroxyl groups for interfacial adhesion, while the in situ formed PDMAEMA chains and Fe 3+ dynamic coordination help stabilize the network and improve the mechanical properties. Meanwhile, SiW 12 acts as a proton-conducting component and also regulates the network structure through electrostatic interactions and hydrogen-bonding interactions with the polymer chains. As a result, the hydrogel exhibits good mechanical performance, stable proton conduction, and good adhesion under both dry and wet conditions. The resulting hydrogel can be assembled into flexible sensors for strain and pressure detection, human motion monitoring, human–machine interaction, and underwater signal recognition and transmission. This work provides an effective strategy for constructing amphibious flexible sensing hydrogels for complex wet environments.