Flexible Smart Noncontact Control Systems with Ultrasensitive Humidity Sensors

Abstract The development of noncontact humidity sensors with high sensitivity, rapid response, and a facile fabrication process is urgently desired for advanced noncontact human–machine interaction (HMI) applications. Here, a flexible and transparent humidity sensor based on MoO 3 nanosheets is developed with a low‐cost and easily manufactured process. The designed humidity sensor exhibits ultrahigh sensitivity, fast response, great stability, and high selectivity, exceeding the state‐of‐the‐art humidity sensors. Furthermore, a wearable moisture analysis system is assembled for real‐time monitoring of ambient humidity and human breathing states. Benefiting from the sensitive and rapid response to fingertip humidity, the sensors are successfully applied to both a smart noncontact multistage switch and a novel flexible transparent noncontact screen for smart mobile devices, demonstrating the potential of the MoO 3 nanosheets‐based humidity sensors in future HMI systems.