Flexible MXene/bamboo cellulose fiber/TPU membrane based humidity sensor for non-contact monitoring of human physiological signals

Abstract

Flexible humidity sensors have a promising application as smart wearable electronic devices for monitoring human physiological signals. In this paper, a flexible humidity sensor was designed to take advantage of the excellent water absorption of the one-dimensional bamboo cellulose fibers (BCFs) and the two-dimensional MXene material with electrical conductivity, both of which were vacuum filtered onto the thermoplastic polyurethane (TPU) hydrophilicly processed by polydopamine (PDA) to preparation of a flexible MXene/BCF/TPU membrane humidity sensor. This MXene/BCF/TPU humidity sensor has good humidity sensitivity performance with a sensitivity of 3.3%/% relative humidity (RH), a response time of 254 s and a recovery time of 304 s. In addition, the MXene/BCF/TPU humidity sensors are subjected to five cycles from 11% RH to 98% RH, 50 stretches, and half a month of exposure to air, respectively, and still maintained a stable dynamic humidity response with good durability. Non-contact sensing applications such as finger humidity monitoring, word recognition and breath recognition can be realized by the MXene/BCF/TPU humidity sensors, and the prediction of breath signals can be realized by neural network algorithms. Therefore, MXene/BCF/TPU humidity sensors have the potential for non-contact monitoring and prediction of human physiological signals in applications.