Recent instrument development for aerosol measurement has focussed on small-scale, on-line measurements that can be incorporated into miniaturised sensor nodes as part of ambient or personal air quality monitoring networks. As a result, optical particle counters (OPCs) have risen in popularity given their ability to consistently size and count individual particles. OPCs have limitations, however, in their inability to detect ultrafine particles (considered the most influential to human health) or to measure particle mass directly (the standard metric for air quality). The growing field of microelectromechanical systems (MEMS) offers a potential alternative by implementing microresonators as mass sensors. MEMS resonators have high mass sensitivities and have recently seen implementation as particulate matter (PM) monitors. The field of MEMS PM instruments is still limited with a variety of implemented resonator topologies and sampling mechanisms. In general, however, they offer real-time, high sensitivity measurements at low flow rates. The aim of this thesis was to further examine the viability of implementing MEMS resonators for PM measurement with a focus on practical considerations for real-world applications. To this end, a new microresonator-based impactor was developed - the MEMS Impactor Stage (MIS) - capable of accommodating various nozzle and resonator combinations. Square lateral bulk acoustic resonators were the primary topology, but the results within the thesis are widely applicable. A series of laboratory studies covered the resonator lifetime, reusability, detection limits, and response to environmental changes. The resonator displayed a high sensitivity throughout, capable of detecting ultrafine particles, but is vulnerable to misinterpretation. Beyond mass measurement, studies introduced possible extensions to hygroscopicity and compositional applications. Ambient particle measurements with the MIS, simulating a real-world application to air quality monitoring, showed the capabilities as a PM instrument while highlighting concerns to be addressed for future instrument design. A microresonator-based impactor has potential as an alternative to OPCs, but its cross sensitivity to deposition patterns and environmental effects must be accounted for prior to implementation as PM monitor.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:744696 |
| Date | January 2018 |
| Creators | Zielinski, Arthur Timothy |
| Contributors | Jones, Roderic ; Kalberer, Markus ; Seshia, Ashwin |
| Publisher | University of Cambridge |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | https://www.repository.cam.ac.uk/handle/1810/274919 |
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