A Miniature System for Separation and Detection of PM Based on 3-D Printed Virtual Impactor and QCM Sensor

In this paper, we report a miniature system for separation and detection of particulate matter (PM) based on a 3-D printed virtual impactor (VI) and a quartz crystal microbalance (QCM) sensor. The VI is optimized by computational fluid dynamics (CFD) simulation to have a minor wall loss and relatively small size of 24 mm × 24 mm × 10 mm, which is utilized for classifying airborne particles according to their size, and the cutoff diameter of the VI is designed to be d
₀
= 2.5 μm. The mass concentration of the separated particles is detected by measuring the frequency shift of the QCM sensor. In order to reliably capture particles, the QCM electrode is coated with a thin photoresist film (420 nm) to enhance surface adhesion. The performance of the miniature PM monitoring system is characterized through classification and detection of silicon dioxide particles with diameter ranging from 0.5 to 8 μm in a chamber. The experimental results show that particles with diameter smaller than 2.5 μm are successfully separated from the inlet flow by the VI and detected by the QCM sensor. Moreover, the sensor shows a good sensitivity of 0.0554 Hz/min per μg/m
³
.