High-Sensitivity Chitin Nanofiber-Coated Series Piezoelectric Quartz Crystal Humidity Sensors

This article fabricated a high-performance chitin nanofiber (ChNF)-coated interdigital electrode–piezoelectric quartz crystal (IDE-PQC) humidity sensor. First, this article investigated the influence of each Butterworth–Van Dyke equivalent parameter of the PQC on the resonance characteristics of the IDE-PQC humidity sensor. Then, the results of MATLAB calculations revealed that the resonant frequency of the IDE-PQC humidity sensor changes larger (i.e., higher sensitivity) by increasing the PQC electrode area and decreasing the quartz wafer thickness. Next, the theoretical result was proved using advanced design system (ADS) simulation. Finally, the moisture-sensitive performances of IDE-PQC humidity sensors with different electrode areas and quartz wafer thicknesses were tested using ChNFs as the moisture-sensitive material. The experimental results showed that the IDE-PQC humidity sensor with a larger electrode area and thinner quartz wafer thickness has higher sensitivity. This article provides a new solution for building a high-performance series PQC sensor.