Gated CMOS-MEMS thermal-piezoresistive oscillator-based PM2.5 sensor with enhanced particle collection efficiency

A gated (on/off operation PM2.5 (aerosol) sensor utilizing CMOS-MEMS thermal-piezoresistive oscillator (TPO) calibrated by a commercial optical aerosol sensor (OAS) has been demonstrated in this work. The thermophoresis effect often seen in the thermal-drive devices to hinder the landing of aerosol (incense) onto the sensor proof-mass is resolved by the gated operation to ensure the functionality of the proposed sensor. In this improved scheme, the impactor used for particle guidance was designed meticulously to enhance the landing probability of the small (∼0.6μm) size aerosol on the proof-mass of the CMOS-MEMS resonator. As compared to the regular particle sensors, this improved setup can detect particles with diameter 5 times smaller. This is of epitome importance as pollutant aerosol particles found in the environment are less than m. 1μm. The enhanced sensitivity of the proposed sensor system enables this technique to be potentially utilized in pollutant monitoring systems implemented by the health regulatory boards across the world. With the OAS calibration, the CMOS-MEMS thermal-piezoresistive oscillator can detect aerosol concentration within a range of 50 μg/m3 to 200 μg/m3.