Abstract
Abstract. We present a portable, inexpensive, and accurate microelectromechanical-system-based (MEMS-based) condensation particle counter (CPC) for sensitive and precise monitoring of airborne ultrafine particles (UFPs) at a point of interest. A MEMS-based CPC consists of two main parts: a MEMS-based condensation chip that grows UFPs to micro-sized droplets and a miniature optical particle counter (OPC) that counts single grown droplets with the light scattering method. A conventional conductive cooling-type CPC is miniaturized through MEMS technology and three-dimensional (3-D) printing techniques; the essential elements for growing droplets are integrated on a single glass slide. Our system is much more compact (75 mm × 130 mm × 50 mm), lightweight (205 g), and power-efficient (2.7 W) than commercial CPCs. In quantitative experiments, the results indicated that our system could detect UFPs with a diameter of 12.9 nm by growing them to micro-sized (3.1 µm) droplets. Our system measured the UFP number concentration with high accuracy (mean difference within 4.1 %), and the number concentration range for which our system can count single particles is 7.99–6850 cm−3. Thus, our system has the potential to be used for UFP monitoring in various environments (e.g., as an air filtration system, in high-precision industries utilizing clean rooms, and in indoor and outdoor atmospheres).
Highlights
Monitoring of airborne ultrafine particles (UFPs, which are smaller than 100 nm) is needed in various fields for human health and yield enhancement in industrial fields (Donaldson et al, 1998; Donovan et al, 1985; Hristozov and Malsch, 2009; Li et al, 2016; Liu et al, 2015)
An air-purification system equipped with an ultra-low particulate filter eliminates the contaminants in the air entering the clean room, it cannot control the UFPs internally generated during the man
A quantitative characterization using Ag particles proves that our system is capable of growing UFPs to micrometer-sized droplets, counting them one by one, and thereby measuring UFP number concentration with a high accuracy, which is comparable to a commercial optical particle counter (OPC). These results show that our system can potentially be used as a portable, low-cost, and high-precision UFP sensor for various fields
Summary
Monitoring of airborne ultrafine particles (UFPs, which are smaller than 100 nm) is needed in various fields for human health and yield enhancement in industrial fields (Donaldson et al, 1998; Donovan et al, 1985; Hristozov and Malsch, 2009; Li et al, 2016; Liu et al, 2015). Because of dramatic developments in nanotechnology, engineered UFPs for commercial and research purposes have been produced on a large scale. These incidentally and intentionally generated UFPs are more harmful to human health than their larger counterparts. High-precision industries with clean rooms require UFP monitoring to trace their sources, minimize the contamination, and thereby increase the production yield. An air-purification system equipped with an ultra-low particulate filter eliminates the contaminants in the air entering the clean room, it cannot control the UFPs internally generated during the man-
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