Abstract
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.
Highlights
Atmospheric particulate matter (PM) is the sum of solid and liquid particles suspended in air.The complex mixture originates from a variety of sources such as salt, soot, metals and fly ash
The results show that by detecting the polystyrene latex (PSL) particles with a certain diameter of 2 μm, the response of the surface acoustic wave (SAW) based PM2.5 sensor is linear, and in accordance with the response of the light scattering based PM2.5 monitor
The mechanical systems (MEMS) method based on a film bulk acoustic resonator (FBAR) mass sensor has a sensitivity of 2 μg/m3 with a 10 min testing time [13]
Summary
Atmospheric particulate matter (PM) is the sum of solid and liquid particles suspended in air. To satisfy the development trend and urgent requirement of the PM2.5 monitoring methods, a miniature PM2.5 sensor based on the surface acoustic wave (SAW) technology was developed. Trend and urgent requirement of the PM2.5 monitoring methods, a miniature PM2.5 sensor based on the surface acoustic wave (SAW) technology was developed. By thermophoresis the thermophoresis effect, the mass from loading from the PM2.5 results the SAW velocity shift, and the change of the oscillation frequency is deposited. Based on the thermophoretic deposition efficiency for a laminar flow profile, the the dimensions of the TP were obtained. A dual-port 300 MHz SAW oscillator was implemented by the sensor detecting probe as the feedback element. 2.5 sensor and data processing unit, the performance of the SAW developed based PM sensor was detecting the polystyrene latex (PSL) particles.
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