Integrating Ti₃C₂T_<i>x</i> MXene Nanosheets with Thermoplastic Polyurethane Nanofibers as Wearable Humidity Sensors for Noninvasive Sleep Monitoring and Noncontact Sensing

Abstract

The development prospects of wearable humidity sensors in noninvasive diagnostic and noncontact sensing have attracted more and more attention. However, most of the existing humidity sensors are uncomfortable to wear and require complex and high-cost fabrication methods, limiting their application in continuous and real-time detection. Herein, an all-nanofiber wearable humidity sensor, integrating Ti 3 C 2 T x MXene nanosheets with thermoplastic polyurethane (TPU) nanofibers, is proposed by combining electrospinning and vacuum magnetron sputtering with high sensitivity, fast response, and good anti-interference ability. Benefiting from the 2D/3D multilevel structure and Grotthuss chain reaction, the sensor exhibits an ultrahigh linear sensitivity of −91%, fast response/recovery time (<3.7 s), and wide sensing range (11–95% RH). Moreover, the sensor is featured with portability, flexibility, breathability, and biocompatibility and is impervious to pressure, temperature, and sweat, contributing to real-time noninvasive monitoring of human respiration and skin moisture. In addition, it can respond remarkably and repeatably to weak humidity changes, which facilitates the noncontact humidity sensing. Most importantly, a simple humidity detection device is assembled and applied to early warn about sleep-related diseases and construct a human–machine interaction interface (such as an intelligent burglar alarm) as a proof of concept.