A 3D microfluidic cage collector for airborne particles

Sensors and Actuators B: Chemical, 2015

This is the accepted version of a paper published in Sensors and actuators. B, Chemical. This paper has been peer-reviewed but does not include the final publisher proof-corrections or journal pagination.

Journal of Aerosol Science, 2006

This research investigates the physical collection characteristics of a novel and compact (combined dimensions ∼ 2.5 l) air-to-liquid aerosol collector recently developed by the Lawrence Livermore National Laboratory. In this collector, the air flow is drawn into an annular, centripetal slot, which directs the aerosol flow into a small volume of liquid at the sampler's center, thereby imbedding airborne particles in the liquid. A mist eliminator positioned above the liquid prevents liquid droplets from escaping the sampler thus improving its performance. We found that the sampler's collection efficiency increases with decreasing width of the annular slot, and with increasing flow rate, mist eliminator speed and sample volume. When operating at a flow rate of 275 l/min and collecting particles into 1 ml of liquid, the sampler can achieve concentration rates as high as 275,000/min. We also determined that by changing the sampler's operational parameters we can move its collection efficiency curve over a wide range of particle sizes, thus adjusting the sampler's cutoff size from 0.45 m to 2.1 m. The sampler's small size and its high collection performance make it suitable for many biodetection strategies. ᭧

Aerosol Science and Technology, 2014

Aerosol sampling and identification is vital for assessment and control of particulate matter pollution, airborne pathogens, allergens and toxins, and their effect on air quality, human health, and climate change. Assays capable of accurate identification and quantification of chemical and biological airborne components of aerosol provide very limited sampling time resolution and relatively dilute samples. A low-cost micro-channel collector (mCC) which offers fine temporal and spatial resolution, high collection efficiency, and delivers highly concentrated samples in very small liquid volumes was developed and tested. The design and optimization of this mCC was guided by computational fluid dynamics (CFD) modeling. Collection efficiency tests of the sampler were performed in a well-mixed aerosol chamber using aerosolized fluorescent microspheres in the 0.5-6 mm diameter range. Samples were collected in the mCC and eluted into 100 mL liquid aliquots; bulk fluorescence measurements were used to determine the performance of the collector. Typical collection efficiencies were above 50% for 0.5 mm particles and 90% for particles larger than 1 mm. The experimental results agreed with the CFD modeling for particles larger than 2 mm, but smaller particles were captured more efficiently than predicted by the CFD modeling. Nondimensional analysis of capture efficiencies showed good agreement for a specific geometry but suggested that the effect of channel curvature needs to be further investigated.

Sensors and Actuators B: Chemical, 2007

Collection of biological particles is the first and critical step for any biological agent detection system. Towards our goal of capturing and detecting airborne biological entities in real time, here we investigate on the design of an electrostatic particle capture system. We report on the capture of airborne 100 nm diameter polystyrene nanoparticles as a model system, in swirling flows under non-uniform electrostatic fields with an electrospray aerosol generator and a homemade particle collector. The particle collector has five positive electrodes on the bottom and one large grounded electrode on the top. The nanoparticles coming into the collector were slowed down during their swirling and stayed in the collector long before leaving the collector. Silicon chips were placed on the bottom electrodes and the electrostatically captured particles were counted as a function of flow rates, electrode positions, bias voltages, and capture times by epifluorescent images and scanning electron micrographs (SEMs). Particles captured in the electrode at the center of the collector were much less than those on the surrounding four electrodes and 10-25% of the particles with negative charges entering the collector were captured on the bottom electrodes at a flow rate of 1.1 l/min and an applied potential of 2 kV. Particle capture increased with decreasing flow rates. We also simulated flow and electrical fields separately, and found the positional trends to be in good agreement with the measurements. This collector is well adaptable to integration with micro resonator devices and can be used for real-time monitoring of bioaerosols.

2013

We present the design and fabrication of a micro electro mechanical systems (MEMS) air-microfluidic particulate matter (PM) sensor, and show experimental results obtained from exposing the sensor to concentrations of tobacco smoke and diesel exhaust, two commonly occurring PM sources. Our sensor measures only 25 mm × 21 mm × 2 mm in size and is two orders of magnitude smaller than commercially available direct mass PM sensors. The small shape allows our sensor to be used for continuous recording of personal PM exposure levels. The sensor contains an air-microfluidic circuit that separates the particles by size (virtual impactor) and then transports and deposits the selected particles using thermophoretic ir quality monitoring M2.5 ir-microfluidics EMS precipitation onto the surface of a microfabricated mass-sensitive film bulk acoustic resonator (FBAR). The mass-loading of the FBAR causes a change in its resonant frequency, and the rate of the frequency change corresponds to the par...

Aerosol Science and Technology, 2017

Aerosol sampling and identification is vital for the assessment and control of particulate matter pollution, airborne pathogens, allergens, and toxins and their effect on air quality, human health, and climate change. In situ analysis of chemical and biological airborne components of aerosols on a conventional filter is challenging due to dilute samples in a large collection region. We present the design and evaluation of a micro-well (m-well) aerosol collector for the assessment of airborne particulate matter (PM) in the 0.5-3 mm size range. The design minimizes particle collection areas allowing for in situ optical analysis and provides an increased limit of detection for liquid-based assays due to the high concentrations of analytes in the elution/analysis volume. The design of the collector is guided by computational fluid dynamics (CFD) modeling; it combines an aerodynamic concentrator inlet that focuses the aspirated aerosol into a narrow beam and a m-well collector that limits the particle collection area to the m-well volume. The optimization of the collector geometry and the operational conditions result in high concentrations of collected PM in the submillimeter region inside the m-well. Collection efficiency experiments are performed in the aerosol chamber using fluorescent polystyrene microspheres to determine the performance of the collector as a function of particle size and sampling flow rate. The collector has the maximum collection efficiency of about 75% for 1 mm particles for the flow rate of 1 slpm. Particles bigger than 1 mm have lower collection efficiencies because of particle bounce and particle loss in the aerodynamic focusing inlet. Collected samples can be eluted from the device using standard pipettes, with an elution volume of 10-20 mL. The transparent collection substrate and the distinct collection region, independent of particle size, allows for in situ optical analysis of the collected PM.

Sensors and Actuators B: Chemical, 2018

The use of microfluidic droplets has become ubiquitous in many Lab-on-a-Chip (LOC) applications ranging from material synthesis to novel biochemical sensing. In this paper, we introduce a new droplet-based approach that incorporates a gas phase for generating liquid droplet microreactors in a microfluidic flow-focusing format. We demonstrate the subsequent on-chip transition, collection and handling of the droplets in a secondary liquid carrier inside a multilayer PDMS structure. The presented technique has potential applications in capturing and probing airborne particles and gaseous vapors using high surfaceto-volume picoliter droplets. The discrete microfluidic gas-liquid interfaces created in this approach, greatly facilitate absorption and up-concentration of a gaseous target analyte into the droplet volume. The chip-based format of the units also allows for different microfluidic modules and analytical techniques to be integrated in this platform for droplet probing, providing highly-sensitive LOC detection systems. Here, we demonstrate the basic principles of sample partitioning with gas-liquid droplets by capturing and detection of vaporized ammonia at different gaseous concentrations using Nessler's reaction inside the droplets. The results of this work provide a simple and robust quantification approach for determining gaseous ammonia which can be further expanded to other gas-phase analytes in next generation of airborne target detectors for human breath analysis and environmental monitoring.

Sensors and Actuators A: Physical, 2013

We present the design and fabrication of a micro electro mechanical systems (MEMS) air-microfluidic particulate matter (PM) sensor, and show experimental results obtained from exposing the sensor to concentrations of tobacco smoke and diesel exhaust, two commonly occurring PM sources. Our sensor measures only 25 mm × 21 mm × 2 mm in size and is two orders of magnitude smaller than commercially available direct mass PM sensors. The small shape allows our sensor to be used for continuous recording of personal PM exposure levels. The sensor contains an air-microfluidic circuit that separates the particles by size (virtual impactor) and then transports and deposits the selected particles using thermophoretic precipitation onto the surface of a microfabricated mass-sensitive film bulk acoustic resonator (FBAR). The mass-loading of the FBAR causes a change in its resonant frequency, and the rate of the frequency change corresponds to the particle concentration in the sampled air volume. We present experimental results that demonstrate the performance of our sensor for measuring PM mass emitted from diesel exhaust and tobacco smoke, and show that it exhibits sensitivity approaching 2 g/m 3 with up to 10 min integration time.

2008 IEEE Sensors, 2008

This paper presents a high-performance microfabricated preconcentrator consisting of a micro-cavity with embedded 3D structures and on-chip thermal desorption capability. The novel crisscross pillar design with multiple inlet/outlet ports demonstrated high surface to volume ratio, higher probability of adsorption, and improved sample distribution. This device achieved a preconcentration factor of more than 10,000 making it suitable for hand-held breath analyzers to concentrate and identify trace levels of volatile organic compounds found in human breath.

2010 IEEE Sensors, 2010

Real-time monitoring of airbo aerosols, is important for protecting hu conserving earth's environment. To this end, selective aerosol sensor, including a centrif microfluidics device for real-time aerosol siz have achieved separation of bidisperse mix polystyrene latex particles in the range of 0.7 This is the first time microchannels have been aerosols by size using mechanical principles system responds to the test particles at co above and below the regulatory limits. Th detection systems together will form a portab for continuous monitoring of aerosols.