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Microfluidic mixing: a review.

Lee CY, Chang CL, Wang YN, Fu LM - Int J Mol Sci (2011)

Bottom Line: In such devices, sample mixing is essentially achieved by enhancing the diffusion effect between the different species flows.Many mixers have been proposed to facilitate this task over the past 10 years.Accordingly, this paper commences by providing a high level overview of the field of microfluidic mixing devices before describing some of the more significant proposals for active and passive mixers.

View Article: PubMed Central - PubMed

Affiliation: Department of Materials Engineering, National Pingtung University of Science and Technology, Pingtung 912, Taiwan; E-Mail: leecy@mail.npust.edu.tw.

ABSTRACT
The aim of microfluidic mixing is to achieve a thorough and rapid mixing of multiple samples in microscale devices. In such devices, sample mixing is essentially achieved by enhancing the diffusion effect between the different species flows. Broadly speaking, microfluidic mixing schemes can be categorized as either "active", where an external energy force is applied to perturb the sample species, or "passive", where the contact area and contact time of the species samples are increased through specially-designed microchannel configurations. Many mixers have been proposed to facilitate this task over the past 10 years. Accordingly, this paper commences by providing a high level overview of the field of microfluidic mixing devices before describing some of the more significant proposals for active and passive mixers.

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Schematic diagrams of barrier embedded Kenics micromixer [72].
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f18-ijms-12-03263: Schematic diagrams of barrier embedded Kenics micromixer [72].

Mentions: Keoschkerjan et al. [71] fabricated a micro-reaction unit for chemical engineering applications based on the combination of multi-lamination and chaotic advection effects. In the proposed design, a mixing zone with a three-dimensional geometry was formed through overlapping microrestrictions. The mixing zone of the second micromixer was formed through cavities in the two wafer levels. The cavities were arranged to form a continuous three-dimensional channel. The geometry of the three-dimensional channel forced the fluid to follow a tortuous path and induced a permanent change in the flow direction. The mixing performance was further enhanced by the turbulence-like and restriction effects induced at the corners of the three-dimensional channel. Kim et al. [72,73] developed barrier embedded micromixers for pressure-driven flow in which chaotic flow was induced by applying periodic perturbations to the velocity field via periodically inserted barriers along the upper surface and helical type flow structures were induced by slanted grooves on the lower surface of the microchannel (Figure 18). Observations using a confocal microscope revealed cross-sectional mixing behaviors in several locations in the micromixer. The proposed design was validated experimentally at a flow rate corresponding to a Reynolds number of 2.28 (corresponding to Re = 1.24 × 104 with a Rhodamine diffusivity of 2.8 × 10−10 m2s−1). Laser scanning of the entrance zone of the micromixer identified a bright image only in the half-zone containing Rhodamine. Bright images were also observed at the no-barrier zone in the first half-cycle, thus confirming the cross-sectional rotating flow effect induced by the slanted grooves. When the streams entered the barrier zone in the next half-cycle, laser scanning showed that the flow had rotated yet further. The experimental results confirmed that the barrier embedded micromixer yielded excellent species mixing within a short length of channel. Recently, Singh et al. [21] analyzed and optimized different designs of SMX motionless mixers based on the Mapping Method. Three design parameters that constituted the number of cross-bars over the width of channel, Nx, the number of parallel cross-bars per element, Np, and the angle between opposite cross-bars. An optimum series for all possible SMX(n) designs to obey the universal design rule is Np = (2/3) Nx − 1, for Nx = 3, 6, 9, 12…


Microfluidic mixing: a review.

Lee CY, Chang CL, Wang YN, Fu LM - Int J Mol Sci (2011)

Schematic diagrams of barrier embedded Kenics micromixer [72].
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC3116190&req=5

f18-ijms-12-03263: Schematic diagrams of barrier embedded Kenics micromixer [72].
Mentions: Keoschkerjan et al. [71] fabricated a micro-reaction unit for chemical engineering applications based on the combination of multi-lamination and chaotic advection effects. In the proposed design, a mixing zone with a three-dimensional geometry was formed through overlapping microrestrictions. The mixing zone of the second micromixer was formed through cavities in the two wafer levels. The cavities were arranged to form a continuous three-dimensional channel. The geometry of the three-dimensional channel forced the fluid to follow a tortuous path and induced a permanent change in the flow direction. The mixing performance was further enhanced by the turbulence-like and restriction effects induced at the corners of the three-dimensional channel. Kim et al. [72,73] developed barrier embedded micromixers for pressure-driven flow in which chaotic flow was induced by applying periodic perturbations to the velocity field via periodically inserted barriers along the upper surface and helical type flow structures were induced by slanted grooves on the lower surface of the microchannel (Figure 18). Observations using a confocal microscope revealed cross-sectional mixing behaviors in several locations in the micromixer. The proposed design was validated experimentally at a flow rate corresponding to a Reynolds number of 2.28 (corresponding to Re = 1.24 × 104 with a Rhodamine diffusivity of 2.8 × 10−10 m2s−1). Laser scanning of the entrance zone of the micromixer identified a bright image only in the half-zone containing Rhodamine. Bright images were also observed at the no-barrier zone in the first half-cycle, thus confirming the cross-sectional rotating flow effect induced by the slanted grooves. When the streams entered the barrier zone in the next half-cycle, laser scanning showed that the flow had rotated yet further. The experimental results confirmed that the barrier embedded micromixer yielded excellent species mixing within a short length of channel. Recently, Singh et al. [21] analyzed and optimized different designs of SMX motionless mixers based on the Mapping Method. Three design parameters that constituted the number of cross-bars over the width of channel, Nx, the number of parallel cross-bars per element, Np, and the angle between opposite cross-bars. An optimum series for all possible SMX(n) designs to obey the universal design rule is Np = (2/3) Nx − 1, for Nx = 3, 6, 9, 12…

Bottom Line: In such devices, sample mixing is essentially achieved by enhancing the diffusion effect between the different species flows.Many mixers have been proposed to facilitate this task over the past 10 years.Accordingly, this paper commences by providing a high level overview of the field of microfluidic mixing devices before describing some of the more significant proposals for active and passive mixers.

View Article: PubMed Central - PubMed

Affiliation: Department of Materials Engineering, National Pingtung University of Science and Technology, Pingtung 912, Taiwan; E-Mail: leecy@mail.npust.edu.tw.

ABSTRACT
The aim of microfluidic mixing is to achieve a thorough and rapid mixing of multiple samples in microscale devices. In such devices, sample mixing is essentially achieved by enhancing the diffusion effect between the different species flows. Broadly speaking, microfluidic mixing schemes can be categorized as either "active", where an external energy force is applied to perturb the sample species, or "passive", where the contact area and contact time of the species samples are increased through specially-designed microchannel configurations. Many mixers have been proposed to facilitate this task over the past 10 years. Accordingly, this paper commences by providing a high level overview of the field of microfluidic mixing devices before describing some of the more significant proposals for active and passive mixers.

Show MeSH