Triboelectric pressure sensor with spiking calibration signal for surface charge density compensation

Abstract

Self-powered triboelectric tactile sensors are growing interest due to increasing demand for various sensors for human-machine interaction and growing global energy concerns. However, signals of triboelectric sensors are easily affected by environment and user motion. It is because the surface charge density depends on those factors. Here, we propose a triboelectric self-powered pressure sensor with a unique spiking calibration system to compensate for change in surface charge density. The sensor generates two signals: open-circuit voltage and spiking calibration voltage. Based on switchable operation, spikes are generated at certain geometrical states. By computing the change in VOC between two consecutive spiked moments, current surface charge density can be calculated in real-time. The magnitudes of spikes were not affected by the speed of motion from 0.1mm/s to 5mm/s. The sensor signal was successfully calibrated in various humidity conditions from relative humidity of 20% to 80% at 22°C, and before and after deliberate charging. Furthermore, the sensor was integrated to a robotic gripper to harvest crops in their optimal environmental conditions to demonstrate its usage in smart farms.