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Micromachines
Special Issues
Mixing in Microchannels
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Mixing in Microchannels

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

Deadline for manuscript submissions: closed (20 June 2022) | Viewed by 6565

Special Issue Editors

Prof. Dr. Xueye Chen

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Guest Editor
College of Transportation, Ludong University, Yantai 264025, China
Interests: microfluidics; nanofluidics; micro/nano manufacturing; MEMS
Prof. Dr. Dalei Jing

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Guest Editor
School of Mechanical Engineering, University of Shanghai for Science and Technology, Shanghai 200093, China
Interests: microfluidic systems; heat and mass transfer over micro/nanoscale; mixing; two-phase fluidic dynamics
Prof. Dr. Joaquin Ortega-Casanova

E-Mail Website
Guest Editor
Department of Mechanical, Thermal and Fluid Engineering, University of Malaga, 29071 Malaga, Spain
Interests: fluid mechanics; micromixing; numerical modelling/optimisation; aero/hydro-dynamics; heat transfer; laminar/turbulent impinging jets; swirling flows; computational fluid dynamics
Special Issues, Collections and Topics in MDPI journals
Dr. Francisco-J. Granados-Ortiz

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Guest Editor
Department of Mechanical, Thermal and Fluid Engineering, University of Malaga, 29071 Malaga, Spain
Interests: mechanical engineering; fluid mechanics; aerodynamics; computational design; heat transfer; impinging jets; optimisation; uncertainty quantification; numerical modelling; machine learning
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

As a significant part of a microfluidic system, microchannel mixers have a wide range of applications in fields such as Lab-on-a-Chip, biochemical analysis, and micro-reactors. The mixing efficiency of the micromixer is important for the performance of microfluidic devices. However, due to the small size of the mixing channel in the micromixer, the fluid flow is restricted by a low-Reynolds-number laminar flow, and mixing occurs primarily through molecular diffusion, resulting in low mixing efficiency. Furthermore, the small characteristic dimension of the microchannel results in large hydraulic resistance and large energy consumption. Thus, improving the hydraulic and mixing performances of the microchannel mixer has inspired comprehensive scientific attentions. To answer this, the present Special Issue welcomes original research papers and review papers on the theoretical, numerical, and experimental studies of the mixing in microchannels, as well as the optimization design, fabrication, and application of both passive and active micromixers.

Prof. Dr. Xueye Chen
Prof. Dr. Dalei Jing
Prof. Dr. Joaquin Ortega-Casanova
Dr. Francisco-J. Granados-Ortiz
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Micromachines is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • microchannel
  • micromixer
  • mixing
  • hydraulic performance
  • optimization design
  • fabrication
  • application

Published Papers (4 papers)

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Research

31 pages, 9277 KiB  
Article
Energy Dissipation Rate and Micromixing in a Two-Step Micro-Reactor with Intensively Swirled Flows
by Rufat Sh. Abiev and Irina V. Makusheva
Micromachines 2022, 13(11), 1859; https://0-doi-org.brum.beds.ac.uk/10.3390/mi13111859 - 29 Oct 2022
Cited by 5 | Viewed by 1128
Abstract
The influence of the hydrodynamics (flow rates Q, specific energy dissipation rate ε) on the micromixing in a two-step microreactor with intensively swirled flows (MRISF-2) was studied experimentally. Three methods of liquid input into the reactor were compared: (i) through the upper [...] Read more.
The influence of the hydrodynamics (flow rates Q, specific energy dissipation rate ε) on the micromixing in a two-step microreactor with intensively swirled flows (MRISF-2) was studied experimentally. Three methods of liquid input into the reactor were compared: (i) through the upper tangential and axial nozzles (TU1, Ax); (ii) through two upper tangential nozzles (TU1, TU2); (iii) through the upper and lower tangential nozzles (TU1, TL2). Segregation index Xs used as a measure of micromixing level was determined by means of iodide iodate reaction method. The Bernoulli equation for a device with two inputs and one output was derived to assess the energy consumption. It was revealed that in MRISF-2 up to 99.8–99.9% of input energy is dissipated, i.e., transformed into liquid element deformations thus resulting in better micromixing. For each of three liquid inputs, the dependence ε = f(Q) could be fairly approximated by an exponent ε = A1Qn1, with n1 ≈ 3.0. For connection (TU1, TU2) the dependence Xs = f(ε) falls linearly for Q > 2 L/min, but for the low flow rates (Q ≈ 1 L/min) there is an unusually small Xs value; the effect of good micromixing is caused by the kinetic energy concentrated in a small volume of liquid near the neck. The best behavior in terms of micromixing was achieved for the (TU1, Ax) connection scheme: the level of Xs ≈ 0.01 for ε ≈ 30 W/kg, and comes down with growing ε to Xs ≈ 0.002 for ε ≈ 30,000 W/kg. These values are 50 and 250 times lower compared to the mixing in a lab glass with a magnetic stirrer, as shown in our previous work. The parameters of dependencies Xs=A3εn3 were found for (TU1, Ax) and (TU1, TL2). Full article
(This article belongs to the Special Issue Mixing in Microchannels)
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11 pages, 2598 KiB  
Article
A 3D Miniaturized Glass Magnetic-Active Centrifugal Micropump Fabricated by SLE Process and Laser Welding
by Jeongtae Kim, Sungil Kim, Jiyeon Choi and Chiwan Koo
Micromachines 2022, 13(8), 1331; https://0-doi-org.brum.beds.ac.uk/10.3390/mi13081331 - 17 Aug 2022
Cited by 1 | Viewed by 1659
Abstract
A miniaturized pump to manipulate liquid flow in microchannels is the key component of microfluidic devices. Many researchers have demonstrated active microfluidic pumps, but most of them still required additional large peripherals to operate their micropumps. In addition, those micropumps were made of [...] Read more.
A miniaturized pump to manipulate liquid flow in microchannels is the key component of microfluidic devices. Many researchers have demonstrated active microfluidic pumps, but most of them still required additional large peripherals to operate their micropumps. In addition, those micropumps were made of polymer materials so that their application may be limited to a variety of fields that require harsh conditions at high pressures and temperatures or organic solvents and acid/base. In this work, we present a 3D miniaturized magnetic-driven glass centrifugal pump for microfluidic devices. The pump consists of a volute structure and a 3D impeller integrated with two magnet disks of Φ1 mm. The 3D pump structure was 13 mm × 10.5 mm × 3 mm, and it was monolithically fabricated in a fused silica sheet by selective laser-induced etching (SLE) technology using a femtosecond laser. The pump operation requires only one motor rotating two magnets. It was Φ42 mm × 54 mm and powered by a battery. To align the shaft of the motor to the center of the 3D glass pump chip, a housing containing the motor and the chip was fabricated, and the overall size of the proposed micropump device was 95 mm × 70 mm × 75 mm. Compared with other miniaturized pumps, ours was more compact and portable. The output pressure of the fabricated micropump was between 215 Pa and 3104 Pa, and the volumetric flow rate range was 0.55 mL/min and 7.88 mL/min. The relationship between the motor RPM and the impeller RPM was analyzed, and the flow rate was able to be controlled by the RPM. With its portability, the proposed pump can be applied to produce an integrated and portable microfluidic device for point-of-care analysis. Full article
(This article belongs to the Special Issue Mixing in Microchannels)
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15 pages, 5348 KiB  
Article
Mixing Enhancement of a Passive Micromixer with Submerged Structures
by Makhsuda Juraeva and Dong Jin Kang
Micromachines 2022, 13(7), 1050; https://0-doi-org.brum.beds.ac.uk/10.3390/mi13071050 - 30 Jun 2022
Cited by 7 | Viewed by 1485
Abstract
A passive micromixer combined with two different mixing units was designed by submerging planar structures, and its mixing performance was simulated over a wider range of the Reynolds numbers from 0.1 to 80. The two submerged structures are a Norman window and rectangular [...] Read more.
A passive micromixer combined with two different mixing units was designed by submerging planar structures, and its mixing performance was simulated over a wider range of the Reynolds numbers from 0.1 to 80. The two submerged structures are a Norman window and rectangular baffles. The mixing performance was evaluated in terms of the degree of mixing (DOM) at the outlet and the required pressure load between inlet and outlet. The amount of submergence was varied from 30 μm to 70 μm, corresponding to 25% to 58% of the micromixer depth. The enhancement of mixing performance is noticeable over a wide range of the Reynolds numbers. When the Reynolds number is 10, the DOM is improved by 182% from that of no submergence case, and the required pressure load is reduced by 44%. The amount of submergence is shown to be optimized in terms of the DOM, and the optimum value is about 40 μm. This corresponds to a third of the micromixer depth. The effects of the submerged structure are most significant in the mixing regime of convection dominance from Re = 5 to 80. In a circular passage along the Norman window, one of the two Dean vortices burst into the submerged space, promoting mixing in the cross-flow direction. The submerged baffles in the semi-circular mixing units generate a vortex behind the baffles that contributes to the mixing enhancement as well as reducing the required pressure load. Full article
(This article belongs to the Special Issue Mixing in Microchannels)
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14 pages, 10523 KiB  
Article
Activity-Induced Enhancement of Superdiffusive Transport in Bacterial Turbulence
by Chenliang Xie, Yanan Liu, Hao Luo and Guangyin Jing
Micromachines 2022, 13(5), 746; https://0-doi-org.brum.beds.ac.uk/10.3390/mi13050746 - 08 May 2022
Cited by 2 | Viewed by 1835
Abstract
Superdiffusion processes significantly promote the transport of tiny passive particles within biological fluids. Activity, one of the essential measures for living matter, however, is less examined in terms of how and to what extent it can improve the diffusivity of the moving particles. [...] Read more.
Superdiffusion processes significantly promote the transport of tiny passive particles within biological fluids. Activity, one of the essential measures for living matter, however, is less examined in terms of how and to what extent it can improve the diffusivity of the moving particles. Here, bacterial suspensions are confined within the microfluidic channel at the state of bacterial turbulence, and are tuned to different activity levels by oxygen consumption in control. Systematic measurements are conducted to determine the superdiffusion exponent, which characterizes the diffusivity strength of tracer particles, depending on the continuously injecting energy converted to motile activity from swimming individuals. Higher activity is quantified to drastically enhance the superdiffusion process of passive tracers in the short-time regime. Moreover, the number density of the swimming bacteria is controlled to contribute to the field activity, and then to strengthen the super-diffusivity of tracers, distinguished by regimes with and without collective motion of interacting bacteria. Finally, the non-slip surfaces of the microfluidic channel lower the superdiffusion of immersed tracers due to the resistance, with the small diffusivity differing from the counterpart in the bulk. The findings here suggest ways of controlled diffusion and transport of substances within the living system with different levels of nutrition and resources and boundary walls, leading to efficient mixing, drug delivery and intracellular communications. Full article
(This article belongs to the Special Issue Mixing in Microchannels)
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