Decoupled and high-sensitivity strain-temperature bimodal sensors based on chitosan-enhanced hydrogel with local...

The rapid advancement of flexible wearable electronics has created an urgent demand for multimodal flexible sensors with both high sensitivity and effective decoupling of multiple physical signals. Herein, we propose a hydrogel-based strain-temperature bimodal flexible sensor enabled by a synergistic strategy of local strain concentration and interfacial charge regulation. The sensor is composed of a polyacrylamide/chitosan (PAM/CS) hydrogel substrate coated with a PEDOT:PSS conductive layer. A periodic platform architecture induces strain concentration in the non-platform regions, thereby significantly enhancing strain sensitivity. Meanwhile, the electrostatic interaction between CS and poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) strengthens the interfacial adhesion and elevates the Seebeck coefficient to 118 μV/K, leading to improved temperature sensitivity. Benefiting from this synergistic mechanism, the fabricated bimodal sensor exhibits outstanding comprehensive performance, including high strain sensitivity (GF = 10.25), a low strain detection limit (0.2%), fast response/recovery time (0.2 s), high temperature sensitivity, an ultralow temperature detection limit (0.2 K), and excellent stability and cycling reliability. More importantly, the local strain concentration strategy enables effective decoupling of strain and temperature signals. Furthermore, the device can switch between single-point/multipoint strain monitoring and spatial temperature field mapping modes, demonstrating broad application potential in human joint motion detection, rehabilitation training, and wearable temperature monitoring.