Multi-mechanism synergistic regulation in MXene/polyacrylamide/polystyrene composite hydrogels for high-performance stretchable strain sensors

This study presents the development of a stretchable strain sensor based on a MXene/polyacrylamide (PAM)/polystyrene (PS) composite hydrogel. Optimizing the material composition and fabrication enables synergistic regulation of a hybrid elastic tunneling model. Linear resistance changes originate from PAM matrix deformation, while additional variations arise from MXene interlayer tunneling. The introduction of PS-induced microcracks further amplifies conductive-path modulation, thereby enhancing sensitivity, response speed, and cyclic stability. The composite hydrogel was synthesized via thermal polymerization, and a systematic evaluation was conducted on the effects of varying MXene (0–77.97 wt. %) and PS (0–0.21 wt. %) ratios on the microstructure, electrical properties, and conduction mechanisms. The sensor demonstrates high performance, achieving a maximum gauge factor of 2.35, a peak strain of up to 98.56%, a minimum detectable strain of 0.0405%, and a high-frequency response of 1.4 Hz across optimized compositions. These metrics show improvements compared with conventional PAM-based binary hydrogel sensors. Furthermore, the sensor retained 95% of its performance after 1000 cycles and achieved rapid response times (∼300 ms) under various stretching angles. This work systematically elucidates the coupled conduction behavior driven by multiple mechanisms and achieves a balance between high sensitivity and wide strain range through compositional tuning. This work establishes a theoretical basis for optimizing the design of flexible sensors and demonstrates potential for future applications in wearable health monitoring and human–machine interaction systems.