Abstract
In this research, a PM2.5 monitor prototype is designed and developed, including the shear horizontal mode surface acoustic wave (SH-SAW) sensor combining with a cyclone separator. In the experiments, aerosols generated by incense smoke will be separated and sampled inside the designed cyclone separator first, and the sampled PM2.5 will be introduced into the sensing area of SH-SAW chip for the detection. Microcentrifuge tubes as the cyclone separator can reduce the device size and power consumption effectively; 122 MHz surface acoustic wave (SAW) chips are fabricated by MEMS techniques in well design and processes; gold interdigital transducers are deposited on the 36° YX-LiTaO3 and using different frequency shift to identify the concentration of sample. Therefore the research is divided into two major parts: cyclone separator design, efficiency simulation and SAW chip detection experiment. To accomplish the goal of detecting the PM concentration in normal atmosphere, the efficiency, device size of the separator and the sensitivity, stability of the SAW chip will be discussed and improved. 0.2 mL microcentrifuge tube with 0.5mm inlet and outlet diameter as the separator has the separation cutoff diameters (d50) at 2.5μm, and the required inlet volumetric flow rate is 0.125 LPM simulated by CFD software; SAW sensor exhibits sensitivity approximately 9Hz/ng; PM2.5 detection experiment conducting with integrated device, shows the strong positive linear correlation between aerosol monitor data, the concentration limit of detection is 11μg/m3 with 160 seconds sample time, total detection time is 5 minutes.