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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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Microscopic images of microfludic mixer with parallelogram barriers in mixing channel [48].
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f8-ijms-12-03263: Microscopic images of microfludic mixer with parallelogram barriers in mixing channel [48].

Mentions: The use of electrokinetic instability (EKI) as a mixing technique for electrokinetically-driven microfluidic flows with conductivity gradients has received considerable attention in recent years [46,47]. In an attempt to improve the mixing performance of micromixers, Tai et al. [48] developed a T-type mixer with parallelogram barriers formed within the microchannels (Figure 8). The authors presented experimental results for the sample concentration distribution in a micromixer for a parallelogram barrier length (PB) of 4/5 W (where W is the channel width), a 10:1 conductivity ratio, and electrical field intensities of 150 V/cm, 300 V/cm and 500 V/cm. The results indicated that the electrokinetic instability phenomenon was induced when high electrical field intensity was applied to drive the flow streams. When the electrokinetic instability effect was not induced, the mixing efficiency at a cross-section located 2.3 mm downstream of the T-junction was 60%. However, when the parallelogram barrier was established, the mixing efficiency increased to 91.25% at the same location. Recent years have witnessed many developments in active mixing approaches for microfluidic devices. Micromixer design appears to be moving towards active chaotic mixers with no moving parts. To avoid complicated microfabrication processes, and to reduce the cost and complexity involved in integrating active mixers in microfluidic systems, the species samples should be driven using an appropriate external energy source such as electrokinetic forces. In recent years, electrokinetic forces have been widely employed in many active mixers, such as the electrokinetic instability micromixer presented by Huang et al. in [11]. However, this particular design suffers the drawback of requiring a high voltage. Accordingly, low-voltage electrokinetic, AC electrokinetic and nonlinear electrokinetic techniques have received increasing attention in recent years as potential means of overcoming this limitation. The high flow rate or high velocity can also be produced through various nonlinear electrokinetic external sources. Therefore, the application of nonlinear electrokinetics to realize active mixers is likely to emerge as a major research topic in the microfluidics community in the future.


Microfluidic mixing: a review.

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

Microscopic images of microfludic mixer with parallelogram barriers in mixing channel [48].
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f8-ijms-12-03263: Microscopic images of microfludic mixer with parallelogram barriers in mixing channel [48].
Mentions: The use of electrokinetic instability (EKI) as a mixing technique for electrokinetically-driven microfluidic flows with conductivity gradients has received considerable attention in recent years [46,47]. In an attempt to improve the mixing performance of micromixers, Tai et al. [48] developed a T-type mixer with parallelogram barriers formed within the microchannels (Figure 8). The authors presented experimental results for the sample concentration distribution in a micromixer for a parallelogram barrier length (PB) of 4/5 W (where W is the channel width), a 10:1 conductivity ratio, and electrical field intensities of 150 V/cm, 300 V/cm and 500 V/cm. The results indicated that the electrokinetic instability phenomenon was induced when high electrical field intensity was applied to drive the flow streams. When the electrokinetic instability effect was not induced, the mixing efficiency at a cross-section located 2.3 mm downstream of the T-junction was 60%. However, when the parallelogram barrier was established, the mixing efficiency increased to 91.25% at the same location. Recent years have witnessed many developments in active mixing approaches for microfluidic devices. Micromixer design appears to be moving towards active chaotic mixers with no moving parts. To avoid complicated microfabrication processes, and to reduce the cost and complexity involved in integrating active mixers in microfluidic systems, the species samples should be driven using an appropriate external energy source such as electrokinetic forces. In recent years, electrokinetic forces have been widely employed in many active mixers, such as the electrokinetic instability micromixer presented by Huang et al. in [11]. However, this particular design suffers the drawback of requiring a high voltage. Accordingly, low-voltage electrokinetic, AC electrokinetic and nonlinear electrokinetic techniques have received increasing attention in recent years as potential means of overcoming this limitation. The high flow rate or high velocity can also be produced through various nonlinear electrokinetic external sources. Therefore, the application of nonlinear electrokinetics to realize active mixers is likely to emerge as a major research topic in the microfluidics community in the future.

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