A Flexible Strain Sensor With Multi-Spatial-Scale Three-Dimensional Conductive Network for Human Physiological Activity Monitoring

This study developed a flexible strain sensor based on a novel polydimethylsiloxane (PDMS)-based conductive nanofiber composite (CNC) featuring a multi-scale three-dimensional (3D) conductive network to overcome the limitations of conventional PDMS films, including low sensitivity and insufficient stretchability. Using electrospinning, PDMS was blended with spinnable thermoplastic polyurethane (TPU) and conductive carbon black (CCB) to fabricate flexible nanocomposite fibers with good stretchability and sensitivity. Subsequently, a mesoscopic 3D conductive network was constructed by loading CCB and carbon nanotubes (CNTs) onto the fiber film surface. This surface network connects with the 3D conductive network formed by CCB within the fiber matrix, ultimately producing a PDMS-based conductive CNC with a multi-scale 3D conductive architecture. This multi-scale structure endows the composite with a wide strain sensing range and fast response (208 ms), while improving tensile strength (3.89 MPa). The material exhibits robust durability under cyclic loading. The resulting wearable sensor possesses good skin affinity and effectively monitors various physiological motions, including joint movements and laryngeal vibration, demonstrating considerable potential for wearable electronics.