Experimental evaluation of miniature plate DMAs (mini-plate DMAs) for future ultrafine particle (UFP) sensor network

Abstract

Two iPhone-sized differential mobility analyzers (DMAs) in the parallel-plate configuration (i.e., miniplate DMAs) were designed and their performance was calibrated in this study in order to gain the instructive knowledge for the future mini-plate DMA design and to have a well-calibrated mini-plate DMA for the ultrafine particle (UFP) sensor network. The performance of mini-plate DMAs was calibrated using the tandem DMA (TDMA) technique. The experimental transfer functions of prototypes at different particle sizes and under various combinational conditions of aerosol and sheath flow rates were derived from the TDMA data. It is concluded that mini-plate DMAs performed reasonably well for UFP sizing. It was also found that the sizing resolution of mini-plate DMAs is closer to the aerosol-to-sheath flow rate ratio when the percentage of aerosol slit opening in length was increased (relative to the width of aerosol classification zone). A new concept of "effective sheath flow rate" was introduced to better interpret the experimental observation on the area and FWHM (full width at half maximum) data of measured DMA transfer functions. Based on the experimental data, we proposed a modified equation for mini-plate DMAs to better calculate the voltage required to size particles of a given electrical mobility.

Design, simulation, and characterization of a radial opposed migration ion and aerosol classifier (ROMIAC)

“…Analytical models of particle classifiers, such as those of Knutson and Whitby (1975), Stolzenburg (1988), andFlagan (2004) are applicable for instruments whose design and operation satisfy the assumptions on which those predictions are based, but geometric and experimental factors, i.e., small aspect ratios and field nonidealities, can lead to deviations in instrument behavior from such models, as seen both in this study and others (Rosell-Llompart et al 1996;Zhang and Flagan 1996;Chen et al 1998;Karlsson and Martinsson 2003;Brunelli et al 2009;Jiang et al 2011;Liu and Chen 2016). Owing to such deviations, one should be cautious about a priori predictions of performance, unless rigorous numerical models of the flows and fields within the instrument are available.…”

Simulation of Miniature PDMA for Ultrafine-Particle Measurement

“…Differential mobility analyzers (DMAs) have been the primary tool for characterizing fine and ultrafine aerosol particles in the atmosphere for a number of years [6,7]. Traditional DMAs are designed cylindrical for laboratory use, and are too large in volume to be suitable for outdoor, portable applications [7][8][9][10]. In contrast with cylindrical DMAs, PDMAs have higher resolution and a simpler manufacturing process, and there is almost no empty space inside them [11][12][13][14].…”

“…Rus, J. et al discussed design criteria leading to high DMA, resolving power R and transmission efficiency η based on various DMA prototypes [16]. Liu and Chen implemented a small PDMA, similar in size to an iPhone 5 [10]. Liu and Chen focused on studying the design and performance of this small PDMA, and discussed its transfer function and other key factors to analyze performance.…”

Development of a toroidal-shaped differential mobility analyzer for effective measurements of airborne particles: Experiment and modeling

“…Other than the standard design of DMAs with cylindrical electrodes, different DMA geometries such as parallel-plate and circular-disk analyzers have been reported to have higher transmission efficiency and better resolution of sub-20 nm particles (Zhang et al 1995;Alsharifi and Chen 2018;Liu and Chen 2016;Li et al 2009). By reducing diffusional broadening effects from a shorter residence time, Zhang et al (1995) developed a radial DMA targeting sub-10 nm particle classification and obtained a transmission efficiency of 0.85 to 0.90 for 3 to 10 nm particles.…”