A Miniature System for Separating Aerosol Particles and Measuring Mass Concentrations

We designed and fabricated a new sensing system which consists of two virtual impactors and two quartz-crystal microbalance (QCM) sensors for measuring particle mass concentration and size distribution. The virtual impactors utilized different inertial forces of particles in air flow to classify different particle sizes. They were designed to classify particle diameter, d, into three different ranges: d < 2.28 μm, 2.28 μm ≤ d ≤ 3.20 μm, d > 3.20 μm. The QCM sensors were coated with a hydrogel, which was found to be a reliable adhesive for capturing aerosol particles. The QCM sensor coated with hydrogel was used to measure the mass loading of particles by utilizing its characteristic of resonant frequency shift. An integrated system has been demonstrated

Ultrafine Aerosol Particle Sizer Based on Piezoresistive Microcantilever Resonators with Integrated Air-Flow Channel

To monitor airborne nano-sized particles (NPs), a single-chip differential mobility particle sizer (DMPS) based on resonant micro cantilevers in defined micro-fluidic channels (µFCs) is introduced. A size bin of the positive-charged fraction of particles herein is separated from the air stream by aligning their trajectories onto the cantilever under the action of a perpendicular electrostatic field of variable strength. We use previously described µFCs and piezoresistive micro cantilevers (PMCs) of 16 ng mass fabricated using micro electro mechanical system (MEMS) technology, which offer a limit of detection of captured particle mass of 0.26 pg and a minimum detectable particulate mass concentration in air of 0.75 µg/m3. Mobility sizing in 4 bins of a nebulized carbon aerosol NPs is demonstrated based on finite element modelling (FEM) combined with a-priori knowledge of particle charge state. Good agreement of better than 14% of mass concentration is observed in a chamber test for the novel MEMS-DMPS vs. a simultaneously operated standard fast mobility particle sizer (FMPS) as reference instrument. Refreshing of polluted cantilevers is feasible without de-mounting the sensor chip from its package by multiply purging them alternately in acetone steam and clean air

Приборы и методы измерений запылённости окружающей воздушной среды. Краткий обзор

The main characteristics of airborne micro/nanoparticles, their impact on human health and air quality standards are presented. International standards classify microparticles by size (PM10, PM2.5, PM1, UFP), establish maximum allowable concentrations and control methods. Particular attention is paid to carbonand virus-containing microparticles control. To monitor the air environment in enclosed spaces and in transport, the portable sensors of micro-, nanoparticles are required with the ability to classify them by size and electrophysical characteristics.Detection of microparticles includes the sorting of particles entering the sensor by size and material type, subsequent actual detection of particles of the same kind, with subsequent classification by size, electrical and morphological characteristics. Separation of nanoand microparticles by size before detection improves the sensitivity and selectivity of the detector both in size and material. The virtual impactor and dielectrophoresis method are considered for integration in a Lab-on-Chip type sensor. Detection of microparticles is performed by separating the dispersed phase from the aerosol followed by the analysis, or directly in the air flow. The classification of detection methods according to speed and functionality is given. Among the methods allowing detection of micrometer and submicrometer size particles, the most suitable for miniaturization and serial production of Lab-on-Chip sensors are the multi-wavelength photoelectric, MEMS, and capacitor elements.The microelectromechanics, microfluidics and microoptics technologies make it possible to create portable sensor systems of the Lab-on-Chip type to detect particulates matter of micrometer and submicrometer size. A micro-, nanoparticles detector prototype based on alumina technology using MEMS elements for a compact Lab-on-Chip type sensor is presented. The proposed design for multifunctional portable detector of airborne micro/nanoparticles is prospective for industry, transport, medicine, public and residential buildings applications.Представлены основные характеристики переносимых воздухом микро/наночастиц, их влияние на здоровье человека и нормативы качества воздушной среды. Международные стандарты классифицируют микрочастицы по размеру (PM10, PM2,5, PM1, UFP), определяют предельно допустимые концентрации и методики их контроля. Особое внимание уделяется контролю углероди вируссодержащих микрочастиц. Для мониторинга воздушной среды в закрытых помещениях, в транспорте требуются портативные датчики микро-, наночастиц с возможностями их классификации по размеру и электрофизическим характеристикам.Детектирование микрочастиц включает сортировку попадающих в детектор микро/наночастиц по размеру и типу материала и собственно детектирование однотипных частиц с последующей классификацией по размеру, электрофизическим и морфологическим характеристикам. Разделение нано и микрочастиц по размеру перед детектированием повышает чувствительность и селективность детектора как по размерам, так и по материалу. Для интеграции в сенсоре Lab-on-Chip типа рассмотрены методы виртуального импактора и диэлектрофореза. Детектирование микрочастиц осуществляется с выделением дисперсной фазы из аэрозоля с последующим анализом либо непосредственно в воздушном потоке. Приведена классификация методов детектирования по быстродействию и функциональным возможностям. Среди методов детектирования частиц микронных и субмикронных размеров наиболее пригодны для миниатюризации и серийного изготовления Lab-on-Chip сенсоров мультиволновые фотоэлектрические, МЭМС, конденсаторные элементы.Технологии микроэлектромеханики, микрофлюидики и микрооптики позволяют создавать портативные сенсорные системы типа Lab-on-Chip для детектирования твёрдых частиц микронного и субмикронного размера. Представлен прототип детектора микро-, наночастиц на основе алюмооксидной технологии с использованием МЭМС элементов для компактного сенсора Lab-on-Сhip типа. Предлагаемая конструкция многофункционального портативного детектора микро/наночастиц воздушной (газовой) среды перспективна для применения в промышленности, транспорте, медицине, общественных и жилых помещениях

Particle Sensor Using Solidly Mounted Resonators

This paper describes the development of a novel particle sensing system employing zinc oxide based solidly mounted resonator (SMR) devices for the detection of airborne fine particles (i.e., PM2.5 and PM10). The system operates in a dual configuration in which two SMR devices are driven by Colpitts-type oscillators in a differential mode. Particles are detected by the frequency shift caused by the mass of particles present on one resonator with while the other acts as a reference channel. Experimental validation of the system was performed inside an environmental chamber using a dust generator with the particles of known size and concentration. A sensor sensitivity of 4.6 Hz per μg/m3 was demonstrated for the SMRs resonating at a frequency of 970 MHz. Our results demonstrate that the SMR-based system has the potential to be implemented in CMOS technology as a low-cost, miniature smart particle detector for the real-time monitoring of airborne particles

Responses of gaseous sulfuric acid and particulate sulfate to reduced SO2 concentration : A perspective from long-term measurements in Beijing

SO2 concentration decreased rapidly in recent years in China due to the implementation of strict control policies by the government. Particulate sulfate (pSO(4)(2-)) and gaseous H2SO4 (SA) are two major products of SO2 and they play important roles in the haze formation and new particle formation (NPF), respectively. We examined the change in pSO(4)(2-) and SA concentrations in response to reduced SO2 concentration using long-term measurement data in Beijing. Simulations from the Community Multiscale Air Quality model with a 2-D Volatility Basis Set (CMAQ/2D-VBS) were used for comparison. From 2013 to 2018, SO2 concentration in Beijing decreased by similar to 81% (from 9.1 ppb to 1.7 ppb). pSO(4)(2-) concentration in submicrometer particles decreased by similar to 60% from 2012-2013 (monthly average of similar to 10 mu g.m(-3)) to 2018-2019 (monthly average of similar to 4 mu g.m(-3)). Accordingly, the fraction of pSO(4)(2-) in these particles decreased from20-30% to b10%. Increased sulfur oxidation ratio was observed both in the measurements and the CMAQ/2D-VBS simulations. Despite the reduction in SO2 concentration, there was no obvious decrease in SA concentration based on data from several measuring periods from 2008 to 2019. This was supported by the increased SA:SO2 ratio with reduced SO2 concentration and condensation sink. NPF frequency in Beijing between 2004 and 2019 remains relatively constant. This constant NPF frequency is consistent with the relatively stable SA concentration in Beijing, while different from some other cities where NPF frequency was reported to decrease with decreased SO2 concentrations. (C) 2020 Elsevier B.V. All rights reserved.Peer reviewe

Electrical And Magnetic Separation Of Particles

Particle separation technologies have been utilized in many industrial fields, such as pigment and filler production, mineral processing, environmental protection, the food and beverage industry, and the chemical industry, as well as in biomedical application, such as cell biology, molecular genetics, biotechnological production, clinical diagnostics, and therapeutics. A lot of particle separation technologies using various mechanics in terms of the differences in the physical or physico-chemical properties of the particles have been developed. Among these categories, electrical and magnetic separations are of great interest in recent researches. The overall objective of this dissertation is to advance our current knowledge on these two particle separation technologies. Accordingly, it has two major parts:: 1) Charge Conditioning for Particle Separation, and: 2) Magnetic Filtering for Particle Separation. In the first part, a new DC-corona-based charge conditioner for critical control of electrical charges on particles and a UV aerosol charger for fundamental investigation particle photocharging process were developed. The chargers\u27 performances including charging efficiencies and charge distributions were evaluated upon different operational conditions such as aerosol flow rates, corona operations, and ion-driving voltages for the charge conditioner, particle material and irradiation intensity for the UV charger. The birth-and-death charging model with the Fuchs limiting sphere theory for calculating the ion-particle combination coefficient was applied to obtain the charging ion concentration inside the charge conditioner. The UV charging model with the photoemission rely on the Fowler-Nordheim law was applied to predict the charging performance of the UV charger. In the second part, a magnetic filter system has been constructed, and its performance has been investigated. To retrieve the magnetic property of characterized particles from the measured penetration data, a numerical model was further developed using the finite element package COMSOL Multiphysics 3.5. The numerical model was first validated by comparing the experimental penetration with the simulation results for the cases of 100, 150, and 250 nm r-Fe2O3 particles having the magnetic susceptibility characterized by Vibrating Sample Magnetometer: VSM). The magnetic susceptibilities of other sizes from 100 to 300 nm were then derived from this model according to the measured penetration data. To control or remove the lunar dust through a magnetic approach, eight samples: three JSC-1A series lunar dust simulants, two NU-LHT series lunar dust simulants, and three minerals) in the size range from 150 to 450 nm were characterized. Magnetic susceptibilities were obtained from the difference in particle penetration through magnetic mesh filters with and without an applied external magnetic field

Atmospheres from Within

In this review of atmospheric investigations from planetary surfaces, a wide variety of measurement and instrument techniques relevant to atmospheric studies from future planetary lander missions are discussed. The diversity of planetary surface environments within the solar system precludes complete or highly specific coverage, but lander investigations for Mars and cometary missions are presented as specific cases that represent the broad range of atmospheric-surface boundaries and that also correspond to high priority goals for future national and international lander missions

Review of sub-3 nm condensation particle counters, calibrations, and cluster generation methods

This review discusses the developments in aerosol instrumentation that have led to the current vapor condensation based instruments capable of detecting sub-3 nm particles. We begin from selected reports prior to the year 1991, which have advanced the technology or understanding in condensation particle counting toward sub-3 nm sizes, and continue to more in depth review of the past efforts after 1991. We discuss how the developments in the calibration methods have progressed the development of particle counting techniques, and review briefly the sub-3 nm calibration experiments and cluster production methods used in calibration experiments. Based on these reviews, we identify several technological and scientific advances for the future to improve the accuracy, understanding, and technology of sub-3 nm particle counting. Copyright (c) 2019 American Association for Aerosol ResearchPeer reviewe

Ultrafine particle generation and measurement

Ultrafine particles (UFPs) with diameters smaller than 100 nm are omnipresent in ambient air. They are important sources for fine particles produced through the agglomeration and/or vapor condensation. With their unique properties, UFPs have also been manufactured for industrial applications. But, from the toxicological and health perspective, ultrafine particles with high surface-to-volume ratios often have high bio-availability and toxicity. Many recent epidemiologic studies have evidence UFPs are highly relevant to human health and disease. In order to better investigate UFPs, better instrumentation and measurement techniques for UFPs are thus in need. The overall objective of this dissertation is to advance out current knowledge on UFPs generation and measurement. Accordingly, it has two major parts: (1) ultrafine particle generation for laboratory aerosol research via electrospray (ES), and (2) ultrafine particle measurement for ambient aerosol monitor and personal exposure study via the development of a cost-effective and compact electrical mobility particle sizer. In the first part, to provide monodisperse nanoparticles, a new single capillary electrospray with a soft X-ray photoionizer as a charge reduction scheme has been developed. The soft X-ray effects on electrospray operation, particle size distribution and particle charge reduction were evaluated. To generate ultrafine particles with sufficient mass concentration for exposure/toxicity study, a TSE twin-head electrospray (THES) was evaluated, as well. The configuration and operational variables of the studied THES has been optimized. Three different nanoparticle suspensions were sprayed to investigate material difference. In the second part, to develop a miniature electrical mobility based ultrafine particle sizer (mini e-UPS), a new mini-plate aerosol charger and a new mini-plate differential mobility analyzer (DMA) have been developed. The performances of mini-plate charger and mini-plate DMA were carefully evaluated for ultrafine particles, including intrinsic/extrinsic charging, extrinsic charge distribution, DMA sizing accuracy and DMA transfer function. A prototype mini e-UPS was then assembled and tested by laboratory generated aerosol. Also a constrained least square method was applied to recover the particle size distribution from the current measured by a mini Faraday Cage aerosol electrometer