Flexible Capacitive Pressure Sensor Enhanced by Black Phosphorus-Au Nanocomposites/Ecoflex Sponge for Pressure and Proximity Detection

Capacitive sensors with high sensitivity, flexibility, stability, and low power consumption have broad applications in wearable electronics, tactile perception, and more. Gaining progressing sensitivity has been one of the goals widely sought by researchers. However, the high fabrication cost of the microstructure and complicated fabrication process limit the large-scale production, hindering the further improvement of current capacitive sensors. For this reason, a low-cost fabrication method of flexible capacitive sensors is explored by fabricating a dielectric composite sponge consisting of black phosphorus-gold nanocomposites (BP-AuNCs) and Ecoflex sponge. With the optimized experimental parameters, the capacitance response of the sensor is measured as a function of noncontact and contact mechanical stimulation. The capacitive sensor exhibits high sensitivity (0.10 kPa $^{-{1}}$ @0–2 kPa, 0.06 kPa $^{-{1}}$ @2–7 kPa, 0.01 kPa $^{-{1}}$ @7–12 kPa), fast response and recovery time (45 and 60 ms), and good stability (>5000 cycles) by utilizing the good mechanical properties of porous Ecoflex dielectric layer and the electrical properties of BP-AuNCs. The performance of the sensor enables it to be used for proximity detection and motion sensing, including respiratory, wrist bending, mouse clicking, and more. In addition, it can detect ultralow pressure (as low as 0.75 Pa). The proposed capacitive pressure sensor is fabricated in a facile process while having good performance, demonstrating its great potential to become an exceptionally reliable candidate for wearable tactile sensors.