Airborne particulates are responsible for severe adverse effects on human health, examples being the lung disease caused by tobacco smoke and severeasthmatic reactions to certain other particulates. Present instrumentation to measure such particulates is bulky, costly to purchase, and difficult to operate; its use in field studies usually requires sending samples collected to an analytical laboratory in order to identify the particulates. This dissertation describes a miniaturized MEMS particulate matter (PM) monitor that employs:
- the deposition of particulates from a sample stream onto a piezoelectric thin-film bulk acoustic wave resonator (FBAR) by means of thermophoresis;
- determination of the mass deposited by measuring the resonant frequency shift of the resonator; and,
- determination of the nature of the particualtes from the absorption characteristics of the deposited film by the use of infrared and ultraviolet LED light sources and photodetectors
Thermophoretic PM precipitation was implemented with a quartz/polysilicon heater that establishes a temperature gradient across the channel through which the sample flows. Under the test conditions, the rate of requency shift for environmental tobacco smoke was approximately 1 kHz/min for a concentration of 400 ug/m^3. Sensitivity to a PM concentration as small as 18 ug/m^3 was observed. The monitor has a volume of 250 cm^3, a mass of 0.114kg, and a power consumption <100 mW. With some minor redesign, the monitor could be made considerable smaller and lighter and to consume significantly less power.