A non-contact porous composite fiber paper-based humidity sensor for wearable breathing and skin humidity monitoring

Flexible sensors capable of continuously monitoring surface moisture and respiratory status play a crucial role in human health monitoring. However, manufacturing flexible humidity sensors at low cost remains challenging in traditional manufacturing industries. This study introduces a humidity sensor prepared by impregnating paper with LiCl solution and using carbon nanotube-carboxymethyl cellulose composite paper-based fibers to fabricate interdigital electrodes. This sensor exhibits high sensitivity to gas humidity due to its flexible and porous electrode structure and moisture-sensitive substrate. The prepared porous fiber paper-based humidity sensor (PLFC) is used for detecting small amounts of gas humidity ranging from 33% RH to 98% RH, with a response time of only 500 ms and a linearity of R2 = 0.960. In terms of human health monitoring, it can continuously monitor respiratory rate and amplitude and non-contactly perceive the humidity status of body parts. By reflecting the tester's physiological condition based on surface humidity, it is highly beneficial for patient recovery care and health preservation. Therefore, the design and ideas proposed in this work are of significant importance for the future development and application of wearable respiratory sensors and moisture sensors. Flexible sensors capable of continuously monitoring surface moisture and respiratory status play a crucial role in human health monitoring.