Microfabricated air-microfluidic sensor for personal monitoring of airborne particulate matter: Design, fabrication, and experimental results.

Abstract: We present the design and fabrication of a micro electro mechanical systems (MEMS) air-microfluidic particulate matter (PM) sensor, and show experimental results obtained from exposing the sensor to concentrations of tobacco smoke and diesel exhaust, two commonly occurring PM sources. Our sensor measures only 25mm×21mm×2mm in size and is two orders of magnitude smaller than commercially available direct mass PM sensors. The small shape allows our sensor to be used for continuous recording of personal PM exposure levels. The sensor contains an air-microfluidic circuit that separates the particles by size (virtual impactor) and then transports and deposits the selected particles using thermophoretic precipitation onto the surface of a microfabricated mass-sensitive film bulk acoustic resonator (FBAR). The mass-loading of the FBAR causes a change in its resonant frequency, and the rate of the frequency change corresponds to the particle concentration in the sampled air volume. We present experimental results that demonstrate the performance of our sensor for measuring PM mass emitted from diesel exhaust and tobacco smoke, and show that it exhibits sensitivity approaching 2μg/m3 with up to 10min integration time. [Copyright &y& Elsevier]