High‐performance flexible humidity sensors for breath detection and non‐touch switches

AbstractFlexible humidity sensors have attracted much attention due to the promising applications in medical health monitoring. Up to now, the realization of such devices with ultrafast response/recovery and wide humidity range still remains a challenge. In this work, we report a new type of humidity sensor based on laser‐induced graphene (LIG) and graphene oxide (GO) with excellent performances. Graphene interdigital electrodes with good conductivity were prepared by the laser‐induced method. Then, the GO dispersion was drop‐coated on the interdigital electrode and heated to form a film as a sensing material. We have systematically studied the performances of the humidity sensor under different humidity levels. The experiment results reveal that the humidity sensor possesses high response, fast response/recovery behavior with 2 and 35 seconds, and wide humidity range from 11% RH to 97% RH. This proposed high‐performance humidity sensors could be applied in practical applications such as human breath monitoring under different states including slow breath, normal breath, fast breath, cough and rhinitis. In addition, the humidity sensors could also be used to monitor the approaching of fingertips, which makes the sensors be ideal non‐contact buttons of the elevator for stopping contacting spread of COVID‐19 viruses.