High-Performance wearable flexible humidity sensor based on plasma-treated graphene oxide for medical monitoring and non-contact sensing

Graphene oxide (GO) is a humidity sensitive material commonly used in the manufacture of humidity sensors. However, GO-based humidity sensors still face issues such as low sensitivity, slow humidity response speed and poor stability in practical applications. In this paper, a flexible humidity sensor based on plasma graphene oxide (P-GO) was introduced, which used plasma-modified GO film as the humidity-sensitive layer, laser-induced graphene (LIG) with fork-finger structure as the electrode layer, and polydimethylsiloxane (PDMS) as the flexible substrate. It was found that the surface water contact angle of the P-GO film treated with plasma for 180 s decreased from 50° to 10°, reaching a superhydrophilic state. The sensitivity of the flexible humidity sensor based on P-GO was improved by nearly 10 times higher than that of the GO sensor. The mechanism was that the surface of the P-GO film was rougher and the relative contents of the surface oxygen-containing functional groups C-O and C=O increased by 6.28 % and 8.49 %, respectively. Meanwhile, the P-GO-based flexible humidity sensor was found to be able to perform a stable and sensitive response over a wide relative humidity range of 7 %∼97 %, possessing a response/recovery speed of 15 s/9s and exhibiting high stability over 60 days. In addition, the P-GO-based flexible humidity sensor was applied for breath detection and non-contact detection, and was found to have a large potential for application in the medical monitoring field.