Recent advances in mass-sensing humidity sensors: mechanisms, materials, and applications

Abstract

Humidity detection is of great significance in industry, agriculture, healthcare, and daily life. Humidity sensor is the core electronic component for humidity detection. Among the various humidity sensors, mass-sensitive humidity (MSH) sensors have received widespread attention due to their excellent humidity sensing performances. This review systematically explores recent advancements in MSH sensors, including quartz crystal microbalance (QCM) humidity sensors and surface acoustic wave (SAW) humidity sensors. Firstly, the unique mass-frequency transduction mechanisms and performance test methods of QCM and SAW humidity sensors are elucidated. Next, we comprehensively categorize and analyze critical advancements in humidity sensing materials for MSH sensors, including oxides, organic materials, two-dimensional materials, other single materials, and composite materials, highlighting their roles in enhancing humidity sensing performances. Furthermore, the potential of MSH sensors is demonstrated through cutting-edge applications on human body related humidity monitoring, including respiratory behavior analysis and non-contact human-machine interaction. Finally, we critically note existing challenges and outline future directions. We expect that this review will provide readers with a comprehensive understanding of MSH sensors and serve as a guide for researchers in the field of MSH sensors.