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Special Issue "Micromixer & Micromixing"

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A special issue of Micromachines (ISSN 2072-666X).

Deadline for manuscript submissions: closed (30 June 2015)

Special Issue Editor

Guest Editor
Prof. Dr. Yong Kweon Suh (Website)

Department of Mechanical Engineering, Dong-A University, Busan 604-714, Korea
Fax: +82 (0) 51 200 7648
Interests: mixing in microsystem; electrohydrodynamics; molecular dynamics simulation

Special Issue Information

Dear Colleagues,

Establishing effective mixing in small scales is of the utmost importance in the design and operation of micromachines. Although numerous ideas have been proposed for enhancing the mixture of fluids in small-scale devices, the subject still deserves our attention because no generalized guidelines presently exist as to, e.g., the optimization of a given mixer system. Aside from the aspect of mixing performance, with respect to the fabrication of micromachines, such as lab-on-chips, the mixer unit should be as simple as possible so as to reduce the cost of products. A Special Issue on “Micromixer & Micromixing” is thus purposed to provide a research forum for scientists and engineers to exchange ideas of mixing enhancement and to present practical applications of mixing technologies in specific machines. We welcome studies, not only on small-scale machines, but also on large-scale systems if the results are relevant to journal readers. Various kinds of fluid-driving tools for mixing, such as acoustic, electrokinetic, and magnetic forces will hopefully be considered by the contributors. We also expect a wide range of applications to be discussed, including those involving heat transfer, chemical reactions, biology, food, etc.

Prof. Dr. Yong Kweon Suh
Guest Editor

Submission

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. Papers will be published continuously (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as 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 refereed through a 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 1000 CHF (Swiss Francs).

Keywords

  • mixing
  • mixer
  • chaotic advection
  • low Reynolds number
  • lab-on-chip
  • microfluidics

Published Papers (8 papers)

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Displaying articles 1-8
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Research

Jump to: Review

Open AccessArticle Comparative Analysis of Passive Micromixers at a Wide Range of Reynolds Numbers
Micromachines 2015, 6(8), 1166-1179; doi:10.3390/mi6081166
Received: 30 June 2015 / Revised: 5 August 2015 / Accepted: 5 August 2015 / Published: 18 August 2015
Cited by 2 | PDF Full-text (14243 KB) | HTML Full-text | XML Full-text
Abstract
Two novel passive micromixers, denoted as the Y-Y mixer and the H-C mixer, based on split-and-recombine (SAR) principle are studied both experimentally and numerically over Reynolds numbers ranging from 1 to 100. An image analysis technique was used to evaluate mixture homogeneity [...] Read more.
Two novel passive micromixers, denoted as the Y-Y mixer and the H-C mixer, based on split-and-recombine (SAR) principle are studied both experimentally and numerically over Reynolds numbers ranging from 1 to 100. An image analysis technique was used to evaluate mixture homogeneity at four target areas. Numerical simulations were found to be a useful support for the design phase, since a general idea of mixing of fluids can be inferred from the segregation or the distribution of path lines. Comparison with a well-known mixer, the Tear-drop one, was also performed. Over the examined range of Reynolds numbers 1 ≤ Re ≤ 100, the Y-Y and H-C mixers showed at their exit an almost flat mixing index characteristic, with a mixing efficiency higher than 90%; conversely the Tear-drop mixer showed a relevant decrease of efficiency at mid-range. Furthermore, the Y-Y and the H-C showed significantly less pressure drop than the Tear-drop mixer. Full article
(This article belongs to the Special Issue Micromixer & Micromixing)
Open AccessArticle Mixing Performance of a Serpentine Micromixer with Non-Aligned Inputs
Micromachines 2015, 6(7), 842-854; doi:10.3390/mi6070842
Received: 30 April 2015 / Revised: 25 June 2015 / Accepted: 26 June 2015 / Published: 3 July 2015
Cited by 3 | PDF Full-text (3328 KB) | HTML Full-text | XML Full-text
Abstract
In this study, a numerical investigation on mixing and flow structure in a serpentine microchannel with non-aligned input channels was performed. The non-aligned input channels generate a vortical flow, which is formed by incoming fluid streams through tangentially aligned channels. Mixing index [...] Read more.
In this study, a numerical investigation on mixing and flow structure in a serpentine microchannel with non-aligned input channels was performed. The non-aligned input channels generate a vortical flow, which is formed by incoming fluid streams through tangentially aligned channels. Mixing index was evaluated to measure the degree of mixing in the micromixer. Analyses of mixing and flow field were investigated for a Reynolds number range starting from 0.1 to 120. The vortical structure of the flow was analyzed to find its effect on the mixing performance. Mixing of two working fluids in the micromixer was evaluated by using three-dimensional Navier–Stokes equations. In order to compare the mixing performance between the serpentine micromixers with and without non-aligned inputs, the geometric parameters, such as cross-section areas of the input channels and main channel, height of the channel, axial length of the channel, and number of pitches, were kept constant. Pressure drops were also calculated with fixed axial length in both cases. Full article
(This article belongs to the Special Issue Micromixer & Micromixing)
Open AccessArticle Effects of Baffle Configuration on Mixing in a T-Shaped Micro-Channel
Micromachines 2015, 6(6), 765-777; doi:10.3390/mi6060765
Received: 8 April 2015 / Revised: 6 June 2015 / Accepted: 15 June 2015 / Published: 17 June 2015
PDF Full-text (1460 KB) | HTML Full-text | XML Full-text
Abstract
A numerical study was performed for a T-shaped microchannel to enhance mixing performance through a baffle configuration. The mixing performance was analyzed in terms of the DOM (degree of mixing) and the pressure load between the two inlets and outlet. Four different [...] Read more.
A numerical study was performed for a T-shaped microchannel to enhance mixing performance through a baffle configuration. The mixing performance was analyzed in terms of the DOM (degree of mixing) and the pressure load between the two inlets and outlet. Four different baffle configurations were designed and simulated to determine how they affect the mixing performance of a T-shaped microchannel. Among the four baffle configurations, a cyclic configuration of baffles produced the best results. It exhibited the fastest growth in the DOM along the microchannel. The cyclic configuration means that four baffles are attached to four side walls of the channel in a cyclic order. The mixing improvement occurs in two ways. One is in the baffle region, when the cyclic configuration causes the fluid flow to rotate in the cross section, unlike other configurations. The other improvement is observed in the remaining outlet branch after the baffle region. This improvement is due to twisting and elongation of the boundary between two fluids. The baffle size and the interval between two consecutive baffles are shown to be optimized in terms of the DOM for a given condition. Full article
(This article belongs to the Special Issue Micromixer & Micromixing)
Open AccessArticle Optimized Simulation and Validation of Particle Advection in Asymmetric Staggered Herringbone Type Micromixers
Micromachines 2015, 6(1), 136-150; doi:10.3390/mi6010136
Received: 23 October 2014 / Accepted: 16 December 2014 / Published: 30 December 2014
Cited by 5 | PDF Full-text (6499 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents and compares two different strategies in the numerical simulation of passive microfluidic mixers based on chaotic advection. In addition to flow velocity field calculations, concentration distributions of molecules and trajectories of microscale particles were determined and compared to evaluate [...] Read more.
This paper presents and compares two different strategies in the numerical simulation of passive microfluidic mixers based on chaotic advection. In addition to flow velocity field calculations, concentration distributions of molecules and trajectories of microscale particles were determined and compared to evaluate the performance of the applied modeling approaches in the proposed geometries. A staggered herringbone type micromixer (SHM) was selected and studied in order to demonstrate finite element modeling issues. The selected microstructures were fabricated by a soft lithography technique, utilizing multilayer SU-8 epoxy-based photoresist as a molding replica for polydimethylsiloxane (PDMS) casting. The mixing processes in the microfluidic systems were characterized by applying molecular and particle (cell) solutions and adequate microscopic visualization techniques. We proved that modeling of the molecular concentration field is more costly, in regards to computational time, than the particle trajectory based method. However, both approaches showed adequate qualitative agreement with the experimental results. Full article
(This article belongs to the Special Issue Micromixer & Micromixing)
Open AccessArticle The Effect of Inertia on the Flow and Mixing Characteristics of a Chaotic Serpentine Mixer
Micromachines 2014, 5(4), 1270-1286; doi:10.3390/mi5041270
Received: 9 October 2014 / Revised: 23 November 2014 / Accepted: 24 November 2014 / Published: 27 November 2014
Cited by 4 | PDF Full-text (4166 KB) | HTML Full-text | XML Full-text
Abstract
As an extension of our previous study, the flow and mixing characteristics of a serpentine mixer in non-creeping flow conditions are investigated numerically. A periodic velocity field is obtained for each spatially periodic channel with the Reynolds number (Re) ranging from 0.1 [...] Read more.
As an extension of our previous study, the flow and mixing characteristics of a serpentine mixer in non-creeping flow conditions are investigated numerically. A periodic velocity field is obtained for each spatially periodic channel with the Reynolds number (Re) ranging from 0.1 to 70 and the channel aspect ratio from 0.25 to one. The flow kinematics is visualized by plotting the manifold of the deforming interface between two fluids. The progress of mixing affected by the Reynolds number and the channel geometry is characterized by a measure of mixing, the intensity of segregation, calculated using the concentration distribution. A mixer with a lower aspect ratio, which is a poor mixer in the creeping flow regime, turns out to be an efficient one above a threshold value of the Reynolds number, Re = 50. This is due to the combined effect of the enhanced rotational motion of fluid particles and back flows near the bends of the channel driven by inertia. As for a mixer with a higher aspect ratio, the intensity of segregation has its maximum around Re = 30, implying that inertia does not always have a positive influence on mixing in this mixer. Full article
(This article belongs to the Special Issue Micromixer & Micromixing)
Figures

Open AccessArticle Mixing Analysis of Passive Micromixer with Unbalanced Three-Split Rhombic Sub-Channels
Micromachines 2014, 5(4), 913-928; doi:10.3390/mi5040913
Received: 15 September 2014 / Revised: 3 October 2014 / Accepted: 10 October 2014 / Published: 22 October 2014
Cited by 9 | PDF Full-text (2413 KB) | HTML Full-text | XML Full-text
Abstract
A micromixer with unbalanced three-split rhombic sub-channels was proposed, and analyses of the mixing and flow characteristics of this micromixer were performed in this work. Three-dimensional Navier-Stokes equations in combination with an advection-diffusion model with two working fluids (water and ethanol) were [...] Read more.
A micromixer with unbalanced three-split rhombic sub-channels was proposed, and analyses of the mixing and flow characteristics of this micromixer were performed in this work. Three-dimensional Navier-Stokes equations in combination with an advection-diffusion model with two working fluids (water and ethanol) were solved for the analysis. The mixing index and pressure drop were evaluated and compared to those of a two-split micromixer for a range of Reynolds numbers from 0.1–120. The results indicate that the proposed three-split micromixer is efficient in mixing for a range of Reynolds numbers from 30–80. A parametric study was performed to determine the effects of the rhombic angle and sub-channel width ratio on mixing and pressure drop. Except at the lowest Reynolds number, a rhombic angle of 90° gave the best mixing performance. The three-split micromixer with minimum minor sub-channel widths provided the best mixing performance. Full article
(This article belongs to the Special Issue Micromixer & Micromixing)
Open AccessArticle Effect of β-PVDF Piezoelectric Transducers’ Positioning on the Acoustic Streaming Flows
Micromachines 2014, 5(3), 654-666; doi:10.3390/mi5030654
Received: 17 July 2014 / Revised: 24 July 2014 / Accepted: 6 August 2014 / Published: 1 September 2014
Cited by 2 | PDF Full-text (8134 KB) | HTML Full-text | XML Full-text
Abstract
This paper reports the numerical and experimental analysis of the acoustic streaming effect in a fluidic domain. The actuation of a piezoelectric transducer generates acoustic waves that propagate to the fluids, generating pressure gradients that induce the flow. The number and positioning [...] Read more.
This paper reports the numerical and experimental analysis of the acoustic streaming effect in a fluidic domain. The actuation of a piezoelectric transducer generates acoustic waves that propagate to the fluids, generating pressure gradients that induce the flow. The number and positioning of the transducers affect the pressure gradients and, consequently, the resultant flow profile. Two actuation conditions were considered: (1) acoustic streaming generated by a 28 μm thick β-poly(vinylidene fluoride) (β-PVDF) piezoelectric transducer placed asymmetrically relative to the fluidic domain and (2) acoustic streaming generated by two 28 μm thick β-PVDF piezoelectric transducers placed perpendicularly to each other. The transducers were fixed to the lower left corner of a poly(methyl methacrylate) (PMMA)cuvette and were actuated with a 24 Vpp and 34.2 MHz sinusoidal voltage. The results show that the number of transducers and their positioning affects the shape and number of recirculation areas in the acoustic streaming flows. The obtained global flows show great potential for mixing and pumping, being an alternative to the previous geometries studied by the authors, namely, a single transducer placed symmetrically under a fluidic domain. Full article
(This article belongs to the Special Issue Micromixer & Micromixing)

Review

Jump to: Research

Open AccessReview Modeling and Optimization of Y-Type Micromixers
Micromachines 2014, 5(4), 886-912; doi:10.3390/mi5040886
Received: 29 August 2014 / Revised: 24 September 2014 / Accepted: 26 September 2014 / Published: 20 October 2014
Cited by 5 | PDF Full-text (3680 KB) | HTML Full-text | XML Full-text
Abstract
A trend in the global technological progress in the last few decades is the development of microsystem technology, microelectromechanical systems and corresponding technologies. Fluid mixing is an extremely important process widely used in various microfluidic devices (chemical microreactors, chemical and biological analyzers, [...] Read more.
A trend in the global technological progress in the last few decades is the development of microsystem technology, microelectromechanical systems and corresponding technologies. Fluid mixing is an extremely important process widely used in various microfluidic devices (chemical microreactors, chemical and biological analyzers, drug delivery systems, etc.). To increase the mixing rate, it is necessary to use special devices: micromixers. This paper presents the results of a hydrodynamic simulation of Y-shaped micromixers. Flows are analyzed for both low and moderate Reynolds numbers. The passive and active mixers are considered. The dependence of the mixing efficiency on the Reynolds and Péclet numbers, as well as the possibility of using the hydrophobic and ultra-hydrophobic coatings is analyzed. Five different flow regimes were identified: (1) stationary vortex-free flow (Re < 5); (2) stationary symmetric vortex flow with two horseshoe vortices (5 < Re < 150); (3) stationary asymmetric vortex flow (150 < Re < 240); (4) non-stationary periodic flow (240 < Re < 400); and (5) stochastic flow (Re > 400). The maximum mixing efficiency was obtained for stationary asymmetric vortex flow. Full article
(This article belongs to the Special Issue Micromixer & Micromixing)

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