All-printed flexible capacitive array tactile force sensors with tunable sensitivity and low crosstalk for micro motion detection

Tactile force sensor has attracted considerable interests owing to its great application prospects in human-computer interaction systems, intelligent robots, wearable medical devices and other fields. The key to achieve this sensor is (1) high sensitivity and low crosstalk, (2) fast response time and (3) the economy of fabricating macroscopic sensors on flexible substrates. However, low-cost tactile sensors reported hitherto cannot simultaneously achieve high sensitivity, low crosstalk and fast response time. In this study, we report an all-printed 4 × 4 capacitive array tactile sensors using PDMS with innovative island-structure and printable nanocomposite inks as dielectric layer and electrodes, respectively. By changing the geometry parameters of the island-structure of the dielectric layer, the sensors can achieve adjustable sensitivity while effectively reducing crosstalk between sensing elements, leading to accurate position perception of the applied pressure. The sensitivity of the sensor can reach 0.76 kPa⁻¹ in the range of 0–1 kPa, and 0.2 kPa⁻¹ in the range of 1–15 kPa. Moreover, the sensor exhibits a fast response time (∼50 ms) and low detection limit (∼2 Pa). These achievements have rarely been reported in a fully printed tactile force sensor. As a proof of concept for fully printed high sensitivity and low crosstalk sensor, human motion and sound signal detection were finally demonstrated. The advantages of the array sensors afford several applications, including low-cost, wide-range flexible wearable devices for measuring signals from a user, rehabilitation training and human-computer interaction, etc.