A High-Sensitivity Strain Sensor with Auxetic and Wrinkled Structure for Human Joint Motion Tracking

Capacitive strain sensors play a crucial role in tracking human joint motion. However, for a long time, the sensitivity GF of the strain sensor is theoretically limited to 1 and is difficult to improve under low strain. This study aims to enhance the sensitivity for more accurate joint motion monitoring by utilizing an auxetic structure (rotating squares system) combined with a wrinkled design to replace the traditional dielectric layer. This novel approach leverages the negative Poissons ratio property of auxetic materials. In this study, inorganic silica gel (SiO_2) and conductive fabric are used to fabricate the dielectric layer and the electrodes, respectively. The strain sensor (80.0mm*20.0mm*1.0mm) with the proposed design achieves a maximum GF of 10.83 and a minimum GF of 4.07. Finally, the strain sensor is tested by measuring the bending angles of the knee joint during walking, jumping, a jump shot, and a fadeaway.