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A Review of Tubeless Microfluidic Devices
Published in Eric Lagally, Krzysztof Iniewski, Microfluidics and Nanotechnology, 2017
Pedro J. Resto, David J. Beebe, Justin C. Williams
Another unique application of passive pumping was the conversion of a passive pumping device into a Coulter counter. A Coulter counter is an apparatus for counting and sizing particles. A microfluidic Coulter counter is appealing because it would bring the benefits of microfluidics to an already popular technique. These benefits include reduced sample volume, simplified operation, high throughput, portability, and low unit cost. Many biomedical applications would benefit from such a microfluidic particle counter. In their work, McPherson et al.45 developed such a counter, using passive pumping as the actuation mechanism for a Coulter counter device (Figure 9.53). They used hydrodynamic focusing to align the particles and maximize counting efficiency. Their results show that a microfluidic particle counter based on passive pumping is as effective as one based on a syringe pump.
Microfluidic Particle Counting Sensors
Published in Sushanta K. Mitra, Suman Chakraborty, Fabrication, Implementation, and Applications, 2016
Chan Hee Chon, Hongpeng Zhang, Xinxiang Pan, Dongqing Li
The Coulter counter perhaps is the most popular and typical conventional particle counting device. Its working principle of measuring electric resistive pulse is also used in some microfluidic particle counting sensors. The Coulter counter was invented by Wallace H. Coulter during World War II and patented in 1953 (Coulter). When Coulter worked for the U.S. Navy, he used this technique to count the number of plankton particles that always caused large echoes on sonar. In a Coulter counter, a small aperture on the wall is immersed into a container that has particles suspended in a low-concentration electrolyte solution. Two electrodes are placed before and after the aperture, and a current path is provided by the electrolyte when an electric field is applied (Figure 14.1) and the aperture creates a “sensing zone.” As a particle passes through the aperture, a volume of electrolyte equivalent to the immersed volume of the particle is displaced from the sensing zone. This causes a short-term change in the impedance across the aperture. This change can be measured as a voltage pulse or as a current pulse. The pulse height is proportional to the volume of the sensed particle. If a constant particle density is assumed, the pulse height is also proportional to the particle mass. This technology is also called aperture technology.
Laboratory Evaluation of Metalworking Fluids
Published in Jerry P. Byers, Metalworking Fluids, Third Edition, 2018
Another means of quantifying emulsion stability is to measure the oil droplet size. This can be done by taking measurements from a photomicrograph,5 or using various instrumental methods. The Coulter Counter® measures electrical conductivity changes as oil droplets, suspended in a salt solution, passed through a small hole. Laser light scattering is another common technique. Particle size determinations are a useful measure of emulsion stability if the assumption is made that smaller oil droplets result in more stable emulsions. Dr. T.J. Lin questions that assumption, however.5
Comparison of zebrafish in vitro and in vivo developmental toxicity assessments of perfluoroalkyl acids (PFAAs)
Published in Journal of Toxicology and Environmental Health, Part A, 2021
Ola Wasel, Kathryn M. Thompson, Yu Gao, Amy E. Godfrey, Jiejun Gao, Cecon T. Mahapatra, Linda S. Lee, Maria S. Sepúlveda, Jennifer L. Freeman
The MTT Assay was used to quantify cell survival using an AB zebrafish embryonic fibroblast cell line (Freeman et al. 2007) maintained at 28°C and 5% CO2 in DMEM media supplemented with AmnioMax, FBS, and antibiotics. Stock solutions of 6,000 ppm (19,105 µM) were prepared in media for both PFHxA and K-PFBS treatments. Stock solutions of 2,000 ppm (4,830 µM) and 8,000 ppm (37,376 µM) were prepared in media for PFOA and PFBA treatments, respectively. Cells were counted using a Coulter counter. 96-well plates were seeded at a density of 7,000 cells/well and cells treated with PFOA, PFHxA, PFBA, or K-PFBS at a range of concentrations. Cells with regular media, without chemical treatment, were considered as 0 ppm negative control. After 96 hr treatment, 10 μl 5 mg/ml MTT was added to each well and incubated for 4 hr. A volume of 100 μl solubilization solution (SS) of 10% Triton in isopropanol at pH 4.8 was then added to each well and the plate shaken for 30 min at room temperature to solubilize the crystals formed. Living cells produce insoluble purple color by reducing MTT by mitochondrial succinate dehydrogenase (Mosmann 1983). The reduction of MTT to a purple formazan product was determined with a SpectraMax® M2e Microplate Reader at 570 nm. The absorbance was recorded and expressed as % control.
Ecotoxicological characterization of the antiepileptic drug carbamazepine using eight aquatic species: baseline study for future higher tier tests
Published in Journal of Environmental Science and Health, Part A, 2019
Katharina Heye, Janina Wiebusch, Johannes Becker, Lydia Rongstock, Kathrin Bröder, Arne Wick, Ulrike Schulte-Oehlmann, Jörg Oehlmann
The algae growth inhibition test with Desmodesmus subspicatus was conducted according to the OECD technical guideline 201.[28] To measure the number of cells via the optical density of the test solutions, a linear function was derived by plotting optical density (λ = 720 nm, Eppendorf BioSpectrometer kinetic 1.3.6.0, Eppendorf, Hamburg, Germany) against the amount of cells per milliliter. A dilution series of cells was used of which the concentration was determined using a Coulter Counter® (version 3.53, 2008, Multisizer™ 3, Beckman Coulter, Brea, CA). Based on this function, 7000 cells/mL were added into 100-mL Erlenmeyer flasks (glass) containing 75 mL AAP medium.[28] The medium was aerated for 2 days (oxygen saturation >90%) before the beginning of the experiment to ensure a high oxygen concentration throughout the experiment. The pH was set to 7.5 ± 0.1. Three replicates were set up per test concentration (Table 2). Erlenmeyer flasks were covered with organic cotton wool and incubated at 24 ± 2 °C and constant lighting (5500 lux) on a standard analog shaker adjusted to 150 orbital rpm (Standard 1000, VWR, Darmstadt, Germany). The growth was measured daily via optical density over the period of 72 h. At the end of the experiment, the specific growth rate was used to calculate the inhibition of the growth rate between days 0 and 3, using the nominally inoculated biomass as the starting value (7000 cells/mL) (calculated according to OECD 201[28]).
Development of polydisperse aerosol generation and measurement procedures for wind tunnel evaluation of size-selective aerosol samplers
Published in Aerosol Science and Technology, 2018
Andrew Dart, Jonathan D. Krug, Carlton L. Witherspoon, Jerome Gilberry, Quentin Malloy, Surender Kaushik, Robert W. Vanderpool
Using an ATD particle density of 2.5462 g/cm3 (measured during this study by ultrapycnometry) and a dynamic shape factor of 1.4 (Endo et al. 1998; Mohler et al. 2008), Equation (1) predicts a lower size detection limit of approximately 3 µm aerodynamic diameter. The upper size limit of the Coulter counter is related to the maximum diameter, which avoids plugging the aperture but is approximately 50 µm aerodynamic diameter for the 100 µm aperture used during this study. where