Airborne particulate matter classification and concentration detection based on 3D printed virtual impactor and quartz crystal microbalance sensor

In this paper, design, fabrication and experiment of a miniature system for detection of airborne particulate matter (PM) are presented. The miniature system contains a virtual impactor and a quartz crystal microbalance (QCM) resonant sensor. The virtual impactor is fabricated by three-dimensional (3D) printing process for classifying airborne particles according to their size. The QCM resonant sensor is utilized to detect the mass of the separated particles from the virtual impactor. The design of virtual impactor is optimized by computational fluid dynamics simulation and the QCM for its resonance in thickness shear mode is analyzed by finite element method. Silicon dioxide powders with diameter in the range from 0.5 to 8 μm are successfully separated according to their size by the virtual impactor, which indicates that the classification characteristic coincides with the theoretical and simulation results. PM concentration in a chamber is measured by the proposed monitoring system and the experimental results show that the resonant frequency of the QCM turns downward linearly with the PM mass loading increasing.