6D-2 MEMS-Enabled Miniaturized Particulate Matter Monitor Employing 1.6 GHz Aluminum Nitride Thin-Film Bulk Acoustic Wave Resonator (FBAR) and Thermophoretic Precipitator

Abstract

We describe a miniaturized MEMS particulate matter (PM) monitor that employs the deposition of particulates from a sample stream onto a 1.6 GHz piezoelectric thin-film bulk acoustic wave resonator (FBAR) by means of thermophoresis, and determination of the mass deposited by measuring the resonant frequency shift of a Pierce oscillator. Real-time measurements made in an environmental chamber over several weeks and during a week-long field study in a residence showed excellent correlation with the responses of other commercial aerosol instruments. An added mass of 1 pg could be resolved with the sensor, and the level of detection was 18 µg / m 3 . The monitor weighs 114 g, has a volume of approximately 245 cm 3 , consumes less than 100 mW, and would cost less than $100 USD in small quantities. Efforts to further miniaturize the sensor and integrate it with a cell-phone are described.

A Portable Wireless Particulate Sensor System for Continuous Real-Time Environmental Monitoring

“…Several new technologies of interest that are under development have the potential to reduce both cost and size of currently available equipment. These include thin-film bulk acoustic wave resonator (FBAR) 31 and MEMS resonator 32 particulate sensors. These technologies may be of significant interest in future developments of particulate matter sensing WSNs.…”

Aerosol impactor with embedded MEMS resonant mass balance for real-time particulate mass concentration monitoring

“…The main challenge in such system is aligning the aerosol jet stream with the microscale resonant device. In [6], airborne particles were deposited onto a film bulk acoustic resonator (FBAR) via thermophoretic precipitation technique. The particles were driven away from a heated surface and collected due to the gained kinetic energies.…”

Transport of airborne particles in straight and curved microchannels

“…Aerosols with diameters of less than half a micrometer have been sorted by size in microchannels using electrostatic forces, 12 and a micromachined virtual impactor was used to sort aerosols into two size bins with a fixed cutoff diameter around 1 μm. 13 Mass-measurements of particulate matter deposited onto thin-film bulk acoustic wave resonators 14 and thermally actuated silicon resonators 15 have also been presented. These approaches demonstrated high resolution and sensitivity to low concentration levels but do not inherently include a size-selective mechanism that would allow the device to characterize the concentration of particular sizes of aerosol.…”