A fast response humidity sensor based on MXene-SWCNTs for the monitoring of respiration

Two-dimensional materials have attracted great interest in humidity sensing due to their excellent sensitivity and response time. Herein, we propose a humidity sensor consisting of MXene and single-walled carbon nanotubes (SWCNTs), using the Marangoni effect to self-assemble two-dimensional materials on the liquid surface, and then preparing them on the interdigital substrate through the layer-by-layer dip-coating method. Due to the expanded interlayer spacing of MXene and more exposed hydrogen active sites provided by SWCNTs, the sensor showed an excellent dynamic property with the response and recovery time of 2 s and 1.75 s Besides, the sensitivity is 0.53 pF/% RH (10–60% RH) and 7.6 pF/% RH (60–90% RH), the maximum humidity hysteresis is 6% of full scale (60% RH), and the reproducibility is ＞200cycles. Then, a flexible humidity breathing detection system has been developed based-on the sensor. Result demonstrated that it can detect human respiration and be successfully used to distinguish different human respiratory patterns. This work not only optimizes the dynamic property of sensors, but also provides a solution for the production of high-performance flexible humidity monitoring systems on this basis.