Flexible Smart Noncontact Control Systems with Ultrasensitive Humidity Sensors.

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 MoO3 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 MoO3 nanosheets-based humidity sensors in future HMI systems.