Highly sensitive flexible humidity sensors with fast response and recovery times based on the composite of graphene oxide and WS2 for detection of human breath and fingertip proximity†

Humidity sensors have been widely used for humidity monitoring in daily life, agriculture, etc. This paper reports flexible resistive humidity sensors based on graphene oxide (GO)/WS₂ hybrid nanostructures, which were made by mixing different volumes of GO and WS₂ dispersions. The GO/WS₂ composite film has been used as a sensing layer on screen-printed interdigital electrodes. The results show that the device shows the best overall performance when the GO/WS₂ volume ratio is 1 : 4, with a high sensitivity of 1.68%/%RH in the humidity range from 11% RH to 59% RH, fast response/recovery times (11.3 s/12.4 s) and low cost. In addition, the humidity sensor has good linearity over a humidity range of 11% RH–59% RH at room temperature (25 °C). The prepared humidity sensor has been successfully applied for human breath detection and human fingertip proximity detection. These findings indicate that the GO/WS₂ composite has great potential for a new generation of high-performance moisture-sensitive elements.