Braiding parameter design of high-compressible yarn-like triboelectric electrode for self-powered fabric pressure sensors

The self-powered textile pressure sensor using triboelectricity is one of the most promising technologies in wearable sensors. However, it is challenging for a pressure sensor to simultaneously achieve a broad pressure sensing range, high energy output, and fast response, and these depend on the high compressive elasticity (the combined performance of yarns’ compressive deformability and elastic recovery under compressive forces) and a large specific surface area of the triboelectric electrode. For the polytetrafluoroethylene/stainless steel (PTFE-SS) braided yarn as the negative triboelectric electrode of fabric pressure sensor, this work adjusted the braiding parameters to obtain high compressive elasticity. Then, the PTFE-SS braided yarns overlap with the polyamide 66/stainless steel (PA66-SS) braided yarns, the positive triboelectric electrode, to form the pressure sensor. It was found that the braiding angle and the number of braiding materials have a significant effect on compressive elasticity of the PTFE-SS braided yarn, and a strong positive linear correlation between the compressive elasticity of the PTFE-SS braided yarn and the output performance of the pressure sensor. When 8 PTFE multifilaments are braided at a 30° to form PTFE-SS braided yarn, the pressure sensor achieves a maximum sensing force (6.0 N), energy output (0.055 µA/cm 2 ), response time (97 ms), and high repeatability (not exceeding 1.9% variation in output voltage after 2000 compression cycles). In addition, the pressure sensor performs outstanding finger-touching sensitivity and gait response. These results indicated that the high compressive elasticity PTFE-SS braided yarn and the overlapping structure can be used to build the fabric sensor.