Highly-sensitive ultrathin flexible pressure sensor based on quasi-2D conductive network for human physiological signal monitoring

Abstract

Ultrathin flexible pressure sensors are highly desirable for human physiological signal monitoring due to their portability and ability to conform to the body. However, existing ultrathin pressure sensors face challenges in balancing the sensitivity and their range. A spatial-dimensionally constrained strategy was proposed to construct an ultrathin active layer. In detail, multi-walled carbon nanotubes (MWCNTs) with an average length of ∼1.3 μm were intentionally spin-coated into a thin thermoplastic polyurethane (TPU) film with a thickness of 1.5 μm. By doing so, a quasi-2D MWCNTs conductive network is constructed, which enabled the sensor to have ultrahigh sensitivity of 27.04 kPa−1, a wide liner detection range of 0.2–24 kPa, ultrafast response time of 40 ms and a recovery time of 10 ms, and high durability in 1500 cycles under 0.2 kPa with loading/unloading frequency of 2 Hz. Thanks to this superior performance, the ultrathin pressure sensor can be used to monitor human movement and physiological signals, including finger touch, finger bending, wrist bending, and deep breathing. Moreover, the sensor can be attached to the side wall of the tip of the renal ureteroscope, allowing for the monitoring of renal pelvic pressure. Therefore, this spatial-dimensionally constrained strategy will open up a new way to fabricate highly sensitive ultrathin pressure sensors and have great application prospects in health monitoring.