Microconformal electrode-dielectric integration for flexible ultrasensitive robotic tactile sensing

Flexible pressure sensors have attracted a lot of interest because of their widespread applications in healthcare, robotics, wearable smart devices, and human-machine interfaces. While microstructuring both the electrodes and dielectrics has been proven to have a significant improvement in the sensitivity and response speed of piezocapacitive sensors, the synergetic influence of microstructured electrodes and dielectrics has not been discussed yet. Herein, a flexible piezocapacitive sensor has been demonstrated with a microstructured graphene nanowalls (GNWs) electrode and a conformally microstructured dielectric layer that consists of polydimethylsiloxane (PDMS) and piezoelectric enhancer of zinc oxide (ZnO). Such microstructured assembly with piezoelectric film constructs a microconformal GNWs/PDMS/ZnO electrode-dielectric integration (MEDI), which can effectively enhance the sensitivity and the pressure-response range. The piezocapacitive sensor exhibits an ultra-high sensitivity (22.3 kPa−1), fast response speed (25 ms), and broad pressure range (22 kPa). The finite element analysis indicates that the polarized electric field caused by the ZnO film’s piezoelectric effect greatly enhances the capacitance of the sensor. Moreover, the integration of the electrode and dielectric layer can eliminate the slippage between contiguous layers, which effectively increases the mechanical stability. Benefitting from the outstanding comprehensive performance, the potential application in robotic tactile perception has been successfully demonstrated, including object grabbing, braille recognition, and roughness detection. The MEDI in structure capacitive sensors provides a new approach to achieve high-performance E-skin, which delivers great potential applications in next-generation robotic tactile sensing.