A PIEZOELECTRIC BULK WAVE RESONANT HUMIDITY SENSOR FOR NONCONTACT HUMAN-MACHINE INTERACTION

This paper presents a humidity sensor consisting of a two-port piezoelectric bulk wave resonator and a uniform layer of graphene oxide (GO) film, aiming for the applications of human-machine interaction. With the help of the hydrophilic GO film, the sensor possesses high sensitivity (195 Hz/%RH with an operating frequency of 10.5 MHz) and low hysteresis (less than 3%RH) to environmental humidity changes. Meanwhile, the humidity response of the sensor is rapid, highly repeatable and stable, which endows the sensor a fast and accurate response to the approach of a human finger. Moreover, by leveraging the different reactions of the sensor to the finger approaching and staying for various lengths of time, the noncontact information input can be realized in the form of Morse code.