American Association for Aerosol Research - Abstract Submission

AAAR 36th Annual Conference
October 16 - October 20, 2017
Raleigh Convention Center
Raleigh, North Carolina, USA

Abstract View


Dual Differential MEMS PM2.5 Mass Sensor: Mitigating Temperature and Humidity Effects through Dual Alternating Thermophoretic Precipitation

DORSA FAHIMI, Shravan Nagarjun Rangaraj, Omid Mahdavipour, Igor Paprotny, University of Illinois at Chicago

     Abstract Number: 669
     Working Group: Instrumentation and Methods

Abstract
Airborne fine particulate matter (PM2.5) has been linked to reduced lung functionality, bronchitis, and heart attacks. The negative health impacts resulting from PM2.5 exposure are significant. Consequently, it is important to develop portable inexpensive PM sensors that can allow the general public to mitigate PM exposure. In this work, we present the evaluation of a new dual differential direct-read MEMS PM2.5 mass sensor. The sensor extends our previous work on the direct-read MEMS PM2.5 mass sensor. The new device is designed such that an air-microfluidics circuit separates fine particulate matter from the airstream by means of a microfabricated particle fractionator, and the mass concentration is measured directly using a film bulk acoustic resonator (FBAR) by particle deposition on its surface using thermophoretic precipitation. The improved design presented in this work greatly increases the utility of the MEMS PM sensor by mitigating its temperature and humidity dependence. In our new design, we introduce a dual differential FBAR configuration, where PM is deposited on one FBAR, while a nearby reference FBAR is kept clean. By switching the deposition between the two FBARs, the drift in the resonant frequency of these resonators due to temperature and humidity variations can be mitigated.

We present new designs for the dual differential PM2.5 mass sensor, and show the results of how the differential reading can be obtained, despite local variations in the ambient temperature due to alternative localized heating created by alternating thermophoretic precipitation. The sensor is evaluated and calibrated at variable temperature and humidity levels using test aerosol in our laboratory setup at UIC. The results show that the new dual differential FBAR design can be used to reduce the dependence of the sensor's response to temperature and humidity changes, and increase the utility of the MEMS PM2.5 mass sensor. A demo of the improved sensor will be presented.