Microfluids in Microchannels

A special issue of Micromachines (ISSN 2072-666X). This special issue belongs to the section "E:Engineering and Technology".

Deadline for manuscript submissions: closed (30 September 2021) | Viewed by 10481

Special Issue Editor


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Guest Editor
Institute of Thermophysics Siberian Branch, Russian Academy of Sciences, Lavrentiev Ave 1, 630090 Novosibirsk, Russia
Interests: microfluidics; two-phase systems; heat and mass transfer; optical techniques

Special Issue Information

Dear Colleagues,

Over the last several decades, microchannel technologies are actively being developed and applied in many industrial sectors, as well as in numerous media-covered fields like biology, medicine, chemical and process engineering, transports, environmental sciences, microelectronics and so on. Microchannels provide high heat and mass transfer rates and enable fast, continuous and safe chemical reactions, reducing material and energy consumption compared to conventional batch systems. Despite a lot of results and achievements in this strongly multi-disciplinary area, further extensive studying is needed. Accordingly, this Special Issue seeks to showcase research papers and review articles that focus on fundamental and applied research of single and two-phase flows in microchannels.

Dr. Artur Bilsky
Guest Editor

Manuscript Submission Information

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Keywords

  • Microchannels
  • microfluidics
  • Single-phase microfluidics
  • two-phase microfluidics
  • micromixers
  • microreactors
  • droplet based microfluididcs
  • heat and mass transfer in microchannels

Published Papers (4 papers)

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Research

17 pages, 12567 KiB  
Article
Experimental Study of the Deposition of Magnetic Particles on the Walls of Microchannels
by Sylvana Varela, Antonio Rivas, Anton Vernet and Jordi Pallarès
Micromachines 2021, 12(6), 712; https://doi.org/10.3390/mi12060712 - 17 Jun 2021
Cited by 2 | Viewed by 1649
Abstract
This study analyzes experimentally the deposition of magnetic beads on the walls of a square microchannel by the action of a nearby cubical magnet. The deposition has been studied for different magnetic bead sizes, flow rates, magnetic conditions and with solutions of magnetic [...] Read more.
This study analyzes experimentally the deposition of magnetic beads on the walls of a square microchannel by the action of a nearby cubical magnet. The deposition has been studied for different magnetic bead sizes, flow rates, magnetic conditions and with solutions of magnetic and non-magnetic particles. Images of the time evolution of the deposition under the different conditions have been analyzed to determine the spatial distribution of the accumulation and the growth rate of the depositions. It has been found that the way in which the magnetic beads are deposited on the walls of the microchannel depends strongly on their size and the magnetic configuration. The accumulation of the major part of particles is on the wall closest to the magnet and, depending on the size of the particles, near the magnet leading and trailing edges or near the center of the magnet. The experiments with magnetic and non-magnetic particles revealed the screening effect of the non-magnetic particles on the deposition. In this case, the non-magnetic particles displace the deposition toward the region near the center of the magnet and near the trailing edge. Full article
(This article belongs to the Special Issue Microfluids in Microchannels)
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10 pages, 3461 KiB  
Article
Negative Pressure Provides Simple and Stable Droplet Generation in a Flow-Focusing Microfluidic Device
by Nikita A. Filatov, Anatoly A. Evstrapov and Anton S. Bukatin
Micromachines 2021, 12(6), 662; https://doi.org/10.3390/mi12060662 - 5 Jun 2021
Cited by 13 | Viewed by 3569
Abstract
Droplet microfluidics is an extremely useful and powerful tool for industrial, environmental, and biotechnological applications, due to advantages such as the small volume of reagents required, ultrahigh-throughput, precise control, and independent manipulations of each droplet. For the generation of monodisperse water-in-oil droplets, usually [...] Read more.
Droplet microfluidics is an extremely useful and powerful tool for industrial, environmental, and biotechnological applications, due to advantages such as the small volume of reagents required, ultrahigh-throughput, precise control, and independent manipulations of each droplet. For the generation of monodisperse water-in-oil droplets, usually T-junction and flow-focusing microfluidic devices connected to syringe pumps or pressure controllers are used. Here, we investigated droplet-generation regimes in a flow-focusing microfluidic device induced by the negative pressure in the outlet reservoir, generated by a low-cost mini diaphragm vacuum pump. During the study, we compared two ways of adjusting the negative pressure using a compact electro-pneumatic regulator and a manual airflow control valve. The results showed that both types of regulators are suitable for the stable generation of monodisperse droplets for at least 4 h, with variations in diameter less than 1 µm. Droplet diameters at high levels of negative pressure were mainly determined by the hydrodynamic resistances of the inlet microchannels, although the absolute pressure value defined the generation frequency; however, the electro-pneumatic regulator is preferable and convenient for the accurate control of the pressure by an external electric signal, providing more stable pressure, and a wide range of droplet diameters and generation frequencies. The method of droplet generation suggested here is a simple, stable, reliable, and portable way of high-throughput production of relatively large volumes of monodisperse emulsions for biomedical applications. Full article
(This article belongs to the Special Issue Microfluids in Microchannels)
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14 pages, 3937 KiB  
Article
Liquid–Liquid Flows with Non-Newtonian Dispersed Phase in a T-Junction Microchannel
by Anna Yagodnitsyna, Alexander Kovalev and Artur Bilsky
Micromachines 2021, 12(3), 335; https://doi.org/10.3390/mi12030335 - 22 Mar 2021
Cited by 8 | Viewed by 2311
Abstract
Immiscible liquid–liquid flows in microchannels are used extensively in various chemical and biological lab-on-a-chip systems when it is very important to predict the expected flow pattern for a variety of fluids and channel geometries. Commonly, biological and other complex liquids express non-Newtonian properties [...] Read more.
Immiscible liquid–liquid flows in microchannels are used extensively in various chemical and biological lab-on-a-chip systems when it is very important to predict the expected flow pattern for a variety of fluids and channel geometries. Commonly, biological and other complex liquids express non-Newtonian properties in a dispersed phase. Features and behavior of such systems are not clear to date. In this paper, immiscible liquid–liquid flow in a T-shaped microchannel was studied by means of high-speed visualization, with an aim to reveal the shear-thinning effect on the flow patterns and slug-flow features. Three shear-thinning and three Newtonian fluids were used as dispersed phases, while Newtonian castor oil was a continuous phase. For the first time, the influence of the non-Newtonian dispersed phase on the transition from segmented to continuous flow is shown and quantitatively described. Flow-pattern maps were constructed using nondimensional complex We0.4·Oh0.6 depicting similarity in the continuous-to-segmented flow transition line. Using available experimental data, the proposed nondimensional complex is shown to be effectively applied for flow-pattern map construction when the continuous phase exhibits non-Newtonian properties as well. The models to evaluate an effective dynamic viscosity of a shear-thinning fluid are discussed. The most appropriate model of average-shear-rate estimation based on bulk velocity was chosen and applied to evaluate an effective dynamic viscosity of a shear-thinning fluid. For a slug flow, it was found that in the case of shear-thinning dispersed phase at low flow rates of both phases, a jetting regime of slug formation was established, leading to a dramatic increase in slug length. Full article
(This article belongs to the Special Issue Microfluids in Microchannels)
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12 pages, 3374 KiB  
Article
Development of a Mobile Analytical Chemistry Workstation Using a Silicon Electrochromatography Microchip and Capacitively Coupled Contactless Conductivity Detector
by Yineng Wang, Xi Cao, Walter Messina, Anna Hogan, Justina Ugwah, Hanan Alatawi, Ed van Zalen and Eric Moore
Micromachines 2021, 12(3), 239; https://doi.org/10.3390/mi12030239 - 27 Feb 2021
Cited by 3 | Viewed by 2128
Abstract
Capillary electrochromatography (CEC) is a separation technique that hybridizes liquid chromatography (LC) and capillary electrophoresis (CE). The selectivity offered by LC stationary phase results in rapid separations, high efficiency, high selectivity, minimal analyte and buffer consumption. Chip-based CE and CEC separation techniques are [...] Read more.
Capillary electrochromatography (CEC) is a separation technique that hybridizes liquid chromatography (LC) and capillary electrophoresis (CE). The selectivity offered by LC stationary phase results in rapid separations, high efficiency, high selectivity, minimal analyte and buffer consumption. Chip-based CE and CEC separation techniques are also gaining interest, as the microchip can provide precise on-chip control over the experiment. Capacitively coupled contactless conductivity detection (C4D) offers the contactless electrode configuration, and thus is not in contact with the solutions under investigation. This prevents contamination, so it can be easy to use as well as maintain. This study investigated a chip-based CE/CEC with C4D technique, including silicon-based microfluidic device fabrication processes with packaging, design and optimization. It also examined the compatibility of the silicon-based CEC microchip interfaced with C4D. In this paper, the authors demonstrated a nanofabrication technique for a novel microchip electrochromatography (MEC) device, whose capability is to be used as a mobile analytical equipment. This research investigated using samples of potassium ions, sodium ions and aspirin (acetylsalicylic acid). Full article
(This article belongs to the Special Issue Microfluids in Microchannels)
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