Heated quartz crystal microbalance with highly controlled integration of ZIF-67 for ultra-reliable humidity sensing

The quartz crystal microbalance (QCM) is widely utilized in various fields for detecting parameters such as relative humidity (RH). However, the reliability of QCM as an RH sensor can be compromised by the nonuniform integration of sensing materials and the absence of a dehumidification system for calibration. Damping of the sensor performance may occur due to excessive water molecule adsorption on agglomerated sensing materials, while ineffective desorption of water molecules from these materials renders QCM-based humidity sensors unreliable in highly humid environments. This study presents an innovative approach to achieve area-specific and highly-controlled integration of ZIF-67 on a quartz crystal microbalance (QCM) using electrospray deposition (ESD). The proposed method effectively decorates the sensor surface with exceptional picogram (pg) mass resolution. Additionally, an integrated microheater facilitates rapid sensor heating, eliminating residual water molecules and enhancing the proposed self-recalibration method. The comparative analysis demonstrates that the heated sensor exhibits a remarkable improvement of 47 times in hysteresis and 8 times in drift performance compared to the non-heated sensor. These findings hold great promise for enhancing the reliability of QCM-based humidity sensors, thereby finding utility in diverse research and application fields.