Polydimethylsiloxane/Graphene Conductive Composite Film Based Flexible Strain Sensor for Body Motion Detection

Strain sensors, which respond to mechanical deformation by altering their electrical properties, have garnered significant attention, especially those that are flexible and stretchable for integration into wearable electronic devices. This interest has been fueled by recent advancements in novel composition nanomaterials and microstructures. A flexible strain sensor based on polydimethylsiloxane/graphene (PDMS/G) conductive composite film was prepared using a simple, efficient, and cost-effective scratch coating method. This study explored the effects of different graphene concentrations (7%, 11%, 14%, and 21%) on the sensing performance of sensors under different conditions. It found that at the graphene concentration of 7%, the stress and strain of the flexible strain sensor exhibit a linear relationship within the strain range of 0–10% and demonstrate an excellent sensitivity across a wide stress range of 1 Pa to 550 kPa. The relative change in resistance ( ΔR / R ) remains stable and shows excellent stability under a repeated small strain of 1.5% up to 1000 times. The prepared flexible sensor also exhibits a fast response time of 750 ms and a recovery time of 550 ms, and the current amplitude can still maintain 75% of its initial state up to 2000 cycles within a strain of 0–6%. The multifunctionality of the flexible strain sensor for the actual detection of various human activities has been confirmed. It is capable of detecting both small strains (i.e., pulse pulsation) and large strain activities (e.g., elbow bending and knee flexion). The PDMS/G conductive composite-film-based flexible strain sensor has been validated for human activity monitoring and other applications.