Miniaturized particulate matter sensor for portable air quality monitoring devices

This paper presents a MEMS particulate matter (PM) sensor for portable air quality detection. The small size (5.2 mm × 4.2 mm × 1 mm) of the sensor allows integration in portable devices. Furthermore, an unsophisticated fabrication process is required which results in higher yield and consequently lower cost. The principle used to detect PM is based on light scattering in a micro fabricated chamber, formed by two micro machined silicon chips, one containing a laser diode and the other a photodiode, mounted on top of each other. The presence of PM in the micro fabricated chamber is detected by an increase of the light scattered and sensed by the photodiode. The principle is validated by exposing the sensor to tobacco smoke, which is a common PM source. Preliminary measurements show that the sensor is capable of detecting the presence of tobacco smoke. The sensor output (1.235V) is in a factor of 5% higher in the presence of tobacco smoke than in clean air.