Wide strain range and high sensitivity sandwich structure CNTs/AgNWs/CNTs/TPU strain sensors for human motion detection

Nowadays, designing a flexible strain sensor that offers both high sensitivity and a wide operating range has been a significant challenge. However, this paper demonstrates the successful preparation of a sandwich-structured, flexible strain sensor with high sensitivity and wide operating range through vacuum-assisted filtration. The substrate of sensor is composed of electrospinning TPU. The three conductive layers of the sensor consist of CNTs, AgNWs, and CNTs. The AgNWs provide extremely low initial resistance and serve to bridge the individual CNTs islands under large strains. The CNTs/AgNWs/CNTs/TPU flexible strain sensor boasts a high sensitivity (GF=1005.8), a wide strain range (up to 350%), and fast response time (39 ms). It also maintains a long working range and long-term usage stability at 2500 cycles. Additionally, the electrothermal and photothermal performance of the sensor were investigated, which revealed a rapid temperature rise to 93.1 °C at 5 V and 80.8 °C at 500 mW/cm2 irradiation intensity. This sensor can accurately monitor the full range of human motion, from tiny pulse and breathing to large-scale finger joint flexion. These findings suggest that our sensor could have great potential for application in wearable devices as well as body health monitoring.