Rapid-response humidity sensors based on ultra-thin films stacked with single-layer graphene oxide

Monitoring and control of humidity is important for industry, agriculture and human activities. Currently, it is achallengeto develop highly sensitive humidity sensors with both the response time and recovery time less than 1 s.Therefore, it isdifficult to dynamically monitor rapid changes in humidity. Here, we report a resistive humidity sensor based on an ultrathin graphene oxide (GO) film, which is formed by stacked single-layered GO. Both the response and recovery time of the sensor is less than 1 s in the range of 10 %–95 % relative humidity (RH). The shortest response and recovery time of the reported GO-based resistive humidity sensor can be 0.33 s at 10 % RH, indicating the fastest response and recovery property to date. Moreover, the sensor is sensitive, and it can accurately detect the distance between the sensor and the human finger as well as the strength of the human breath. The simple preparation, microscale structure, and extremely fast response make the GO-based sensor a new alternative for integrated humidity sensors with real-time monitoring functions.