Special Issue "Optimization of Microfluidic Devices"

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

Deadline for manuscript submissions: closed (15 November 2019).

Special Issue Editor

Prof. Kwang-Yong Kim
E-Mail Website
Guest Editor
Department of Mechanical Engineering, Inha University, Incheon, 22212, Korea
Tel. +82-32-872-3096
Interests: micromixer; micro heat sink; fluid machinery; optimization; heat transfer
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Special Issue Information

Dear Colleagues,

Performance of most microfluidic devices depends strongly on the geometric shape of flow channels. Thus, shape optimization of microchannels is required to improve the performance of microfluidic devices. Recently, computational fluid dynamics (CFD) has been widely used in the analyses of fluid flow, mixing, and chemical reactions in microfluidic devices. In addition, design optimization using 3D CFD and optimization techniques has become an efficient tool for the design of microfluidic devices, owing to the development of computers. Most microfluidic problems involve multiple conflicting design objectives. For example, the degree of mixing and pressure drop can be two objectives of a micromixer design. A popular approach to multi-objective optimization is optimization using multi-objective evolutionary algorithms (MOEAs), where multiple trade-off solutions for the objectives are determined. The latest MOEAs include Pareto evolutionary algorithms, Pareto archived evolutionary strategies, and an elitist non-dominated sorting genetic algorithm. Multi-objective problems yield many solutions, which are known as Pareto-optimal solutions. These Pareto optimal solutions can be used to analyze trade-offs among designs. The current Special Issue covers applications of design optimization to various microfluidic devices.

Prof. Kwang-Yong Kim
Guest Editor

Manuscript Submission Information

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Keywords

  • Optimization
  • Microfluidic device
  • Computational fluid dynamics
  • Multi-objective optimization

Published Papers (3 papers)

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Research

Open AccessArticle
Elaboration of the Demulsification Process of W/O Emulsion with Three-Dimensional Electric Spiral Plate-Type Microchannel
Micromachines 2019, 10(11), 751; https://doi.org/10.3390/mi10110751 - 01 Nov 2019
Abstract
Rapid and efficient demulsification (destabilizing of an emulsion) processes of a water in oil (W/O) emulsion were carried out in a three-dimensional electric spiral plate-type microchannel (3D-ESPM). In this experiment, the demulsifying efficiency of emulsions by 3D-ESPM was compared with that by gravity [...] Read more.
Rapid and efficient demulsification (destabilizing of an emulsion) processes of a water in oil (W/O) emulsion were carried out in a three-dimensional electric spiral plate-type microchannel (3D-ESPM). In this experiment, the demulsifying efficiency of emulsions by 3D-ESPM was compared with that by gravity settling, the factors influencing demulsifying efficiency were investigated, and the induction period, cut size and residence time in the demulsification process were studied. The results showed that in contrast to the gravity settling method, 3D-ESPM can directly separate the disperse phase (water) instead of the continuous phase (oil). The maximum demulsifying efficiency of W/O emulsion in a single pass through the 3D-ESPM reached 90.3%, with a microchannel height of 200 μm, electric field intensity of 250 V /cm, microchannel angle of 180°, microchannel with 18 plates and a flow rate of 2 mL /min. An induction period of 0.6 s during the demulsification process was simulated with experimental data fitting. When the residence time of emulsion in 3D-ESPM was longer than the induction period, its demulsifying efficiency increased as the increase of the flow velocity due to the droplet coalescence effects of Dean vortices in the spiral microchannel. For this device a cut size of droplets of 4.5 μm was deduced. Our results showed that the demulsification process of W/O emulsion was intensified by 3D-ESPM based on the coupling effect between electric field-induced droplets migration and microfluidic hydrodynamic trapping. Full article
(This article belongs to the Special Issue Optimization of Microfluidic Devices)
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Open AccessArticle
Single and Multi-Objective Optimization of a Three-Dimensional Unbalanced Split-and-Recombine Micromixer
Micromachines 2019, 10(10), 711; https://doi.org/10.3390/mi10100711 - 21 Oct 2019
Abstract
The three-dimensional geometry of a micromixer with an asymmetrical split-and-recombine mechanism was optimized to enhance the fluid-mixing capability at a Reynolds number of 20. Single and multi-objective optimizations were carried out by using particle swarm optimization and a genetic algorithm on a modeled [...] Read more.
The three-dimensional geometry of a micromixer with an asymmetrical split-and-recombine mechanism was optimized to enhance the fluid-mixing capability at a Reynolds number of 20. Single and multi-objective optimizations were carried out by using particle swarm optimization and a genetic algorithm on a modeled surrogate surface. Surrogate modeling was performed using the computational results for the mixing. Mixing and flow analyses were carried out by solving the convection–diffusion equation in combination with the three-dimensional continuity and momentum equations. The optimization was carried out with two design variables related to dimensionless geometric parameters. The mixing effectiveness was chosen as the objective function for the single-objective optimization, and the pressure drop and mixing index at the outlet were chosen for the multi-objective optimization. The sampling points in the design space were determined using a design of experiment technique called Latin hypercube sampling. The surrogates for the objective functions were developed using a Kriging model. The single-objective optimization resulted in 58.9% enhancement of the mixing effectiveness compared to the reference design. The multi-objective optimization provided Pareto-optimal solutions that showed a maximum increase of 48.5% in the mixing index and a maximum decrease of 55.0% in the pressure drop in comparison to the reference design. Full article
(This article belongs to the Special Issue Optimization of Microfluidic Devices)
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Open AccessArticle
Chaotic Micromixer Based on 3D Horseshoe Transformation
Micromachines 2019, 10(6), 398; https://doi.org/10.3390/mi10060398 - 14 Jun 2019
Abstract
To improve the efficiency of mixing under laminar flow with a low Reynolds number (Re), a novel three-dimensional Horseshoe Transformation (3D HT) was proposed as the basis for the design of a micromixer. Compared with the classical HT, the Lyapunov exponent of the [...] Read more.
To improve the efficiency of mixing under laminar flow with a low Reynolds number (Re), a novel three-dimensional Horseshoe Transformation (3D HT) was proposed as the basis for the design of a micromixer. Compared with the classical HT, the Lyapunov exponent of the 3D HT, which was calculated based on a symbolic dynamic system, proved the chaotic enhancement. Based on the 3D HT, a micromixer with a mixing length of 12 mm containing six mixing units was obtained by sequentially applying “squeeze”, “stretch”, “twice fold”, “inverse transformation”, and “intersection” operations. Numerical simulation and Peclet Number (Pe) calculations indicated that when the squeeze amplitude 0 < α < 1/2, 0 < β < 1/2, the stretch amplitude γ > 4, and Re ≥ 1, the mass transfer in the mixer was dominated by convective diffusion induced by chaotic flow. When Re = 10, at the outlet of the mixing chamber, the simulated mixing index was 96.4%, which was far less than the value at Re = 0.1 (σ = 0.041). Microscope images of the mixing chamber and the curve trend of pH buffer solutions obtained from a mixing experiment were both consistent with the results of the simulation. When Re = 10, the average mixing index of the pH buffer solutions was 91.75%, which proved the excellent mixing efficiency of the mixer based on the 3D HT. Full article
(This article belongs to the Special Issue Optimization of Microfluidic Devices)
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