A formaldehyde gas concentration measurement system based on a quartz crystal microbalance sensor

Formaldehyde is a kind of air pollutant with strong volatility at room temperature. Formaldehyde is emitted from many sources, such as furnishing, building sector, and smoking. Formaldehyde is classified as a highly carcinogenic substance for human health. To mitigate the health impact of formaldehyde, it is necessary to detect and measure it. However, the measurement technology development of formaldehyde concentration in ambient air is rarely developed and is categorized as a high-cost device. Thus, this study aims to develop a formaldehyde measurement system based on a bare quartz crystal microbalance (QCM) due to its high sensitivity and low energy consumption. This study uses a 5?MHz QCM (uncoated QCM, silver electrodes) for the sensing unit connected to an oscillator and a frequency counter. The measured frequency shift is used to calculate the concentration of formaldehyde. The system was tested for the formaldehyde concentration measurement by varying the concentration generated by a sonication technique with different variations in the length of the evaporation time and mass. The result shows a linear correlation between frequency shift and formaldehyde concentration with a significant regression coefficient (R2>0.97). The system detects formaldehyde gas with concentrations up to 716?mg. L-1 with sensitivity and response time of 39x10-3 Hz. L. mg-1 and ∼167?s, respectively. This result indicates that the system with a bare QCM has the potential to measure formaldehyde gas in the air with good performance.