Fabrication of quartz crystal microbalance humidity sensors based on super-hydrophilic cellulose nanocrystals

Natural cellulose nanocrystals (CNCs) possess outstanding properties, such as biodegradability, hydrophilicity, large specific surface areas, and are low in cost. A highly stable and sensitive humidity sensor based on a quartz crystal microbalance (QCM) was prepared using CNCs as the sensing film. To investigate the impact of CNCs loading on the sensor performance, a series of humidity-sensitive performance tests, including linearity, response and recovery times, repeatability, hysteresis characteristics, selectivity, and long-term stability tests, was conducted. The experimental results indicated that the humidity sensor with CNCs loading of 2 μg (QCM-2) exhibited excellent logarithmic linearity, high sensitivity (32.35 Hz/% relative humidity (RH)), excellent reversible behavior, and long-term stability at a RH of 11–84%. The contact angle of QCM-2 was 12.5°, revealing its suitable hydrophilicity. Thus, we demonstrate that CNCs are great prospects for potential application in humidity sensors with high performance and low cost.