Flexible Wearable Humidity Sensor Based on Nanodiamond With Fast Response

In this paper, a novel and flexible humidity sensor based on nanodiamond (ND) sensing film was fabricated on a polyimide substrate. A series of flexibility-related humidity testing experiments is also performed. The experimental results demonstrated that the prepared sensor exhibited a subsecond response/recovery time and showed good repeatability under different bending states. It was found that different bending radii had an influence on the humidity sensor's response/recovery time. The response/recovery time is reduced with the increase in bending radius, which is suspected to be related to the interspace change of nanodiamond sensing membrane under different bending radii. Furthermore, due to good flexibility and rapid response, this humidity sensor can be directly attached on finger or wrist for human breath detection, which can provide a more convenient monitoring means for human health activities such as sports and fitness.