Sensitive and versatile humidity sensor based on rice flour modified quartz crystal microbalance (QCM)

Designing and manufacturing a cost-effective and efficient humidity sensor to measure and monitor of humidity is important in various industrial and biological fields. One of the methods of humidity sensing is the gravimetric method based on the adsorption of humidity on an oscillating quartz crystal. Due to the low sensitivity and adsorption capability of bare crystal surface to moisture, it is necessary to coat it with some suitable moisture adsorbent material. In this research, rice flour was studied as a good coating material for the crystal surface due to its good moisture adsorption properties, satisfactory stability and rapid desorption leading to a fast response. The mechanism of sensing moisture in this method is based on frequency changes with increasing water pressure mass adsorbed on it. Results showed that this low cost and easy to fabricatesensor can measure humidity in the range of ۱۱ to ۹۳% with a significant sensitivity and satisfactory precision. The fabricated sensor has a relatively fast response time i.e. around ۵ minutes of sensing and recovery.