Flexible Humidity Sensing Fiber with High Sensitivity and Stability for Wearable Weaving and Physiological Signal Monitoring

With the rapid development of information technology, people's demand for intelligent, convenient, and comfortable electronic devices is gradually increasing, and flexible intelligent wearable electronic devices are leading the development trend of the future intelligent industry. As an important part of noncontact sensing, humidity sensing plays an important role in flexible wearable electronic devices. In this paper, by combining conductive multiwalled carbon nanotubes (MWCNTs) and silver nanowires (AgNFs) with sodium alginate (SA), the AgNFs/MWCNT/SA humidity sensing fibers with excellent sensitivity and stability were prepared by the simple wet spinning method. Experimental results show that the humidity sensing fiber had a large relative resistance change over a wide humidity range of 10–90%, and it can be sensitive to the humidity difference of 5% in the high humidity limit. In addition, the change in fiber diameter and AgNF content would affect the sensing performance of the humidity sensor fibers. Finally, the humidity sensing fiber with a diameter of 156 μm and a AgNFs content of 3.3 wt % was selected and woven into the mask and textile, which successfully realized the monitoring function of respiratory function and the skin surface moisture volatilization process. The successful preparation of the AgNFs/MWCNT/SA humidity sensor fiber broke through the shortcomings of traditional humidity sensing materials, such as poor flexibility, a complex preparation process, and the inability to realize fabric-based wearable devices through the weaving process, and provided unlimited possibilities for the development of smart wearable devices.