A Novel Particulate Matter 2.5 Sensor Based on Surface Acoustic Wave Technology

Design, fabrication and experiments of a miniature particulate matter (PM) 2.5 sensor based on the surface acoustic wave (SAW) technology were proposed. The sensor contains a virtual impactor (VI) for particle separation, a thermophoretic precipitator (TP) for PM2.5 capture and a SAW sensor chip for PM2.5 mass detection. The separation performance of the VI was evaluated by using the finite element method (FEM) model and the PM2.5 deposition characteristic in the TP was obtained by analyzing the thermophoretic theory. Employing the coupling-of-modes (COM) model, a low loss and high-quality SAW resonator was designed. By virtue of the micro electro mechanical system (MEMS) technology and semiconductor technology, the SAW based PM2.5 sensor detecting probe was fabricated. Then, combining a dual-port SAW oscillator and an air sampler, the experimental platform was set up. Exposing the PM2.5 sensor to the polystyrene latex (PSL) particles in a chamber, the sensor performance was evaluated. The results show that by detecting the PSL particles with a certain diameter of 2 μm, the response of the SAW based PM2.5 sensor is linear, and in accordance with the response of the light scattering based PM2.5 monitor. The developed SAW based PM2.5 sensor has great potential for the application of airborne particle detection.