Advances in quartz crystal microbalance relative humidity sensors: A review

Humidity is a physical quantity used to assess the concentration of water vapor in the air. Humidity detection is of great significance in various fields such as industry, agriculture, meteorology, and national defense. Quartz crystal microbalance (QCM) humidity sensors have been extensively developed due to their high sensitivity, digital output, strong anti-interference ability, low energy consumption, and ease of modification. This paper reviews recent advancements in QCM humidity sensors, focusing on different materials, electrode structures, and their applications. This review begins by explaining the sensing principles of QCM, followed by an overview of the testing methods for QCM humidity sensors. It then summarizes the humidity-sensitive performance of QCM sensors made from various materials, including oxides, polymers, carbon materials, graphene-like materials, and natural nanomaterials. Subsequently, the review discusses the humidity-sensitive properties of QCM sensors with different electrode structures. Finally, it addresses the challenges faced in the development of QCM humidity sensors.