A highly linear humidity sensor based on quartz crystal microbalance coated with urea formaldehyde resin/nano silica composite films

- Urea formaldehyde resin (UFR) and nano-silica composite films are used as the humidity sensitive films.
- The composite films were prepared by in situ polymerization on the surface of the quartz crystal electrode.
- A highly linear humidity sensor can be obtained by adjusting the mass ratio and the total mass of the composite films.

A highly linear humidity sensor based on a quartz crystal microbalance (QCM) was developed using urea formaldehyde resin (UFR) and nano-silica composite films. The composite films were prepared by in situ polymerization on the surface of the quartz crystal electrode. The scanning electron microscopy (SEM) images show that there are some interaction between UFR and nano-silica in the blend. The experiment results indicate that the optimal mass ratio of urea and formaldehyde to nano-silica is 1:2.8 and the total mass of the composite films loaded on the QCM is 0.95 μg. Under the optimum conditions, the humidity sensor exhibits good linearity (R2 = 0.9998), short response time (12 s), short recovery time (25 s), good stability and reproducibility. The proposed sensor can be applied to the determination of humidity in practical production.