Utilizing Multilayer Design of Organic-Inorganic Hybrids to Enhance Wearable Strain Sensor in Humid Environment

Flexible strain wearable sensors have attracted considerable attention due to their advantages of low cost, lightweight, high sensitivity and good flexibility. However, the strain sensors are easy to be damaged in an extreme humidity environment or by the wearer’s sweat in the process of use, resulting in detection disorder or even a short circuit. Furthermore, preparation of sensors with stable properties under extreme environments is one of the most important research directions. To fill this gap, a flexible sensor was prepared by using polyurethane and carbon nanotubes, then modified by polydopamine and 1H,1H,2H,2H-perfluorodecane-mercaptan. A typical tunnel model was used to explain the working mechanism of the sensor, the sensitivity of the sensor is also explained and evaluated by the tunneling theory. The results show that the sensor has good sensitivity (the sensor has a stable sensing signal output under a strain range from 2% to 300%) and stability over 8500 cycles. At the same time, the sensor has good superhydrophobicity, the water contact angle reaches 152°, and it is still stable in a humid environment. Moreover, this sensor shows excellent performance in monitoring human joint motion (such as finger, elbow, wrist and knee) and physiological signals (such as speaking and drinking). This work provides an effective design method for the sensor which can be applied in a high humidity environment.