Flexible Textile Structures Composed of Various Functional Threads and Managing Circuitry for Self-Powered Wearable Sensor System

In this research, we propose a sensor system consisting of a power-generating sensor with a textile structure comprising piezoresistive, piezoelectric, and supercapacitor threads, and a circuit for efficient energy delivery. A multifunctional piezoelectric energy harvester for energy generation, piezoresistive strain, and capacitive tactile sensors to detect motion, and supercapacitor for energy storage were implemented through the proposed sensor platform. An energy management circuit was also added to the platform to store the generated energy and supply it for sensor operation. The devices were fabricated into a textile structure using functional threads in a total area of 130 mm × 130 mm with a 7 × 7 thread array. The piezoresistive strain sensor exhibited a resistance change of approximately 24% at a maximum strain of 24%, and the capacitive tactile sensor exhibited a change rate of 12.5% at a maximum vertical force of 5 N. In addition, the energy source, a piezoelectric energy harvester, obtained a power of 440 μW at a 6 Hz motion and a 3 MΩ load resistor. In the energy management circuits, using a parallel synchronized switch harvesting on inductor (P-SSHI) circuit and a voltage doubler, increased the voltage stored in the supercapacitor by 119%.