Dual Cross-Linked Ion-Based Temperature-Responsive Conductive Hydrogels with Multiple Sensors and Steady Electrocardiogram Monitoring

To balance the requirements of transparency, mechanical strength, stable conductivity, and biocompatibility of traditional electronic conductive hydrogels in intelligent devices is still a formidable challenge. The increase of ionic conductive gels has provided decent transparency, stretchability, and wearability in artificial skins but the dilemma still exists between stability and functionality. This article reports a facile strategy to develop a visual thermosensitive physically and chemically dual cross-linked ion-based conductive hydrogel through in situ free-radical copolymerization, achieving robust mechanical properties, an obvious response, and a multiple sensing process. As an archetypical template, the ion-based conductive hydrogel offers an evaluation and monitoring of electrocardiogram (ECG), which is comparable to commercial electrodes. Intriguingly, such kinds of conductive gels exhibit tunable upper critical solution temperature (UCST) behaviors. Taking advantage of their high temperature responsive accuracy, the visualized qualitative observation for smart response and digitized measurement and calibration for thermal stimulus can be simultaneously achieved. We therefore believe that this work will inspire the design of skinlike sensing materials, promote the preparation of biocompatible and multiple sensing abilities and the synthesis of intelligent hydrogels, and realize their applications in biosensors, wearable devices, and biomedicine.