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Open AccessArticle

Detection of Particulate Matter of Size 2.5 μm with a Surface-Acoustic-Wave Sensor Combined with a Cyclone Separator

1
Institute of NanoEngineering and MicroSystems, National Tsing Hua University, Hsinchu 30013, Taiwan
2
Institute of Environmental Engineering, National Chiao Tung University, Hsinchu 30013, Taiwan
3
Department of Power Mechanical Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan
*
Author to whom correspondence should be addressed.
Micromachines 2018, 9(8), 398; https://doi.org/10.3390/mi9080398
Received: 26 June 2018 / Revised: 8 August 2018 / Accepted: 9 August 2018 / Published: 12 August 2018
(This article belongs to the Special Issue Advanced MEMS/NEMS Technology)
A device to monitor particulate matter of size 2.5 μm (PM2.5) that has been designed and developed includes a surface-acoustic-wave sensor operating in a shear horizontal mode (SH-SAW) combined with a cyclone separator. In our tests, aerosols generated as incense smoke were first separated and sampled inside a designed cyclone separator; the sampled PM2.5 was then introduced into the sensing area of an SH-SAW sensor for detection. The use of microcentrifuge tubes as a cyclone separator effectively decreases the size and power consumption of the device; the SAW sensor in a well design and operating at 122 MHz was fabricated with MEMS techniques. After an explanation of the design of the cyclone separator, a simulation of the efficiency and the SAW sensor detection are discussed. A microcentrifuge tube (volume 0.2 mL, inlet and outlet diameters 0.5 mm) as a separator has separation cutoff diameters 50% (d50) at 2.5 μm; the required rate of volumetric flow at the inlet is 0.125 LPM, according to simulation with computational fluid dynamics (CFD) software; the surface-acoustic-wave (SAW) sensor exhibits sensitivity approximately 9 Hz/ng; an experiment for PM2.5 detection conducted with the combined device shows a strong positive linear correlation with a commercial aerosol monitor. The limit of detection (LOD) is 11 μg/m3 with sample time 160 s and total detection duration about 5 min. View Full-Text
Keywords: cyclone separator; surface-acoustic-wave sensor; environmental sensing; PM2.5 cyclone separator; surface-acoustic-wave sensor; environmental sensing; PM2.5
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MDPI and ACS Style

Kuo, F.-Y.; Lin, Y.-C.; Ke, L.-Y.; Tsai, C.-J.; Yao, D.-J. Detection of Particulate Matter of Size 2.5 μm with a Surface-Acoustic-Wave Sensor Combined with a Cyclone Separator. Micromachines 2018, 9, 398.

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