Abstract
Flexible wearable strain sensors capable of high sensitivity and wide sensing ranges are essential for next-generation personalized healthcare, human-machine interfaces, and continuous physiological monitoring. In this study, we report the development of a highly sensitive and robust flexible piezoresistive strain sensor based on a hybrid nanocomposite consisting of liquid-phase exfoliated few-layer graphene (FLG) embedded within a micro-structured polydimethylsiloxane (PDMS) and thermoplastic polyurethane (TPU) elastomeric matrix. By engineering a dual-scale hierarchical surface architecture via micro-contact molding, the conductive percolation network exhibits dynamic micro-crack propagation and reversible contact resistance modulation under mechanical deformation. The optimized graphene-polymer hybrid sensor achieves an outstanding gauge factor of 142.6 in the low-strain regime (<10%) and maintains a broad working strain range up to 75%, alongside an ultra-fast response time of 28 ms, negligible electromechanical hysteresis (3.4%), and exceptional cyclic durability over 10,000 stretching-relaxing cycles. To evaluate biomedical utility, the sensor was directly mounted on human skin to monitor both subtle physiological signals (epidermal radial artery pulse and vocal cord vibrations) and large-scale joint articulations (finger bending and swallowing motions). The demonstrated electromechanical performance and biocompatibility underscore the substantial potential of this graphene-elastomer hybrid architecture for continuous, non-invasive wearable health diagnostics.
