Flexible Tactile Sensor Arrays With Capacitive and Resistive Dual-Mode Transduction

The existing flexible tactile sensors can respond to either heavy load or small load, due to the limitation of their sensing units with single perception principle. To address this issue, we proposed a flexible tactile sensing array with capacitive and resistive dual-mode transduction. Copper foil and conductive graphite paint film were used as the electrodes of sensors, which differ in resistance by an order of magnitude. Furthermore, air cavity was designed to serve as the dielectric layer. The capacitor operates normally in response to small external loads. While the external load increases to a certain extent, the electrodes of the sensors will contact each other, which causes the capacitor failure. Simultaneously, the short-circuit effect accompanies and triggers the resistive sensing mode. The experimental results show that the capacitive mode is effective under load less than 0.9 N with a resolution of 0.02 N and a response time of 29 ms. When the external force is increased beyond 0.9 N, the capacitive mode becomes ineffective, while the resistive mode takes the effect. The resistive sensor has a resolution of 0.9 N in the range of [0.9, 16.3 N] and a response time of 31 ms. Moreover, the tactile sensor shows high repeatability and low hysteresis. The superposed plasticine detection and letter recognition experiments were performed to further illustrate the multiscale force sensing ability of the proposed sensor.