A Wearable Capacitive Friction Force Sensor for E-Skin

In recent years, the rapid development of intelligent robots has placed higher demands on robotic hands that can dexterously manipulate objects. Among them, sensors that can measure and differentiate friction in real time have attracted great attention. Here, inspired by the fingerprint morphology, a wearable capacitive friction force sensor is proposed based on the laser etching process. The sensor is composed of polydimethylsiloxane (PDMS) elastomer as the dielectric strain layer and conductive silica gel as the electrode. Both the dielectric strain layers and electrodes are arranged in an interdigital structure and perpendicular to the sensor surface. The capacitance of the sensor decreases with increasing friction force applied to the surface of the sensor. The sensor has excellent sensing performance with a high friction force sensitivity of 0.149 N–1, an ultralow detection limit of 1 N (friction force), and a fast response time of 40 ms, and the sensor does not exhibit fatigue after 1000 friction robustness tests. More importantly, wearable tactile sensors have broad application scenarios in intelligent robotic arms and human motion detection. In addition, the fabrication strategy of this sensor provides a solution for the fabrication of wearable friction force sensors.