Highly Sensitive, Stretchable Chopped Carbon Fiber/Silicon Rubber Based Sensors for Human Joint Motion Detection

Strain sensing in applications such as soft robotic, human motion detection, health and sports monitoring, mass measurement, human-machine interfaces has attracted increasing attention. In the present paper, a piezoresistive composite strain sensor based on chopped carbon fiber (CCF) as a conductive element and silicone rubber as a stretchable polymeric matrix was introduced. The results of the electromechanical evaluation under cyclic loading suggest high sensitivity (maximum gauge factor of 50) within the strain amplitudes of up to 25 %. The nonlinear electromechanical behavior of the CCF/silicone strain sensors revealed a positive-to-negative piezoresistivity due to the deformation mechanisms including axial deformation, Poisson's effect, and viscoelastic characteristics. The sensors were employed to monitor human joint motion detection at the wrist, knee, as well as the elbow. The results showed high reversibility and strong sensing performance in action. The results showed that the fabricated sensors could be integrated with human textiles to record the motion data as the signals were observed to be well stable and highly sensitive to both small and large deformations induced by human motion.