Flexible tactile sensors have broad applications in human physiological monitoring, robotic operation and human-machine interaction. However, the research of wearable and flexible tactile sensors with high sensitivity, wide sensing range and ability to detect three-dimensional (3D) force is still very challenging. Herein, a flexible tactile electronic skin sensor based on carbon nanotubes (CNTs)/polydimethylsiloxane (PDMS) nanocomposites is presented for 3D contact force detection. The 3D forces were acquired from combination of four specially designed cells in a sensing element. Contributed from the double-sided rough porous structure and specific surface morphology of nanocomposites, the piezoresistive sensor possesses high sensitivity of 12.1 kPa-1 within the range of 600 Pa and 0.68 kPa-1 in the regime exceeding 1 kPa for normal pressure, as well as 59.9 N-1 in the scope of < 0.05 N and > 2.3 N-1 in the region of < 0.6 N for tangential force with ultra-low response time of 3.1 ms. In addition, multi-functional detection in human body monitoring was employed with single sensing cell and the sensor array was integrated into a robotic arm for objects grasping control, indicating the capacities in intelligent robot applications.
Keywords: 3D force detection; CNTs/PDMS nanocomposites; Electronic skin; Flexible tactile sensors; Piezoresistive sensors.