Spring 2012 Conference
March 7 - 9

Plenary 9: Gerardo Jaramillo

Airborne Particulate Monitoring Using a Micromechanical Electrometer

Environmental air quality is monitored by accurately sizing and quantifying nanometer-sized aerosol particles present in the atmosphere. One method of detection electrically charges the particles and then feeds a stream of charged particles into a Faraday cup electrometer. We present the first results of a MEMS based electrometer for the detection of small currents from ionized particles in a particle detection system. The MEMS electrometer is a millimeter-scale micromechanical silicon sensor. We replaced the Faraday cup with a filtering mesh sensing-electrode coupled to a MEMS electrometer with a noise floor below 1 fA rms produced by 10 nm diameter particles within an airflow of 1.0 L/min. At this airflow, a minimum particle density of 400 cm^-3 produced a current of 6242 electrons/sec (= 1 fA). The MEMS electrometer achieved an experimental sensitivity of 19.68 uVrms/fA and charge-detection efficiency of 5.476 X 10^7 V/C