Wearable capacitive sensor based on ionic gels and a multi-channel sensor array for space mapping of pressure

Pulse is a critical sign in evaluating physical health for the traditional Chinese medicine. A wearable flexible pressure sensor is a good scheme for human pulse signals monitoring. The flexible pressure sensors are required own high sensitivity and fast response time. Adding ionic gel to the dielectric layer of capacitive pressure sensors to form a double electric layer is an effective way to enhance the sensitivity and the resolution of the sensors. However, the fluidity and instability of liquid seriously hinder the sensor’s application. In this work, a ternary composite gel dielectric layer, composed by H₂O, polyvinyl alcohol (PVA) and ionic liquids (ILs) with high flexibility and chemical stability, was prepared. Excellent self-healing and mechanical properties ensure the service life of the ionic gels. Assembled with patterned adhesive tape and two Ag electrodes, the sensor has a semi-hollow sensing chamber. A maximum sensitivity of 5.55 kPa^-1 and a fast response time of 53 ms were observed. The sensor also exhibits remarkable mechanical stability over 3000 load-release cycles. This outstanding performance endows the sensor with promising potential for application in pulse detection. Besides, a multi-channel sensors array is proposed to reveal the pressure distribution in the spatial dimension.