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 respectively 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 increased to a certain extent, the electrodes of the sensors will contact each other, which causes the capacitors 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 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 effect. The resistive sensor has a resolution of 0.9 N in rang of [0.9 N, 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 multi-scale force sensing ability of the proposed sensor.