Electrokinetic instability effects in microchannels with and without nanofilm coatings

Fu, Lung-Ming; Hong, T.; Wen, Chih-Yung; Tsai, Chien Hsiung; Lin, Che-Hsin

doi:10.1002/elps.200800455

Cited by 11 publications

(9 citation statements)

References 41 publications

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“…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).…”

Section: Active Microfluidic Mixersmentioning

confidence: 99%

Microfluidic Mixing: A Review

Lee

Chang²,

Wang³

et al. 2011

IJMS

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938

496

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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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Section: Active Microfluidic Mixersmentioning

confidence: 99%

Microfluidic Mixing: A Review

Lee

Chang²,

Wang³

et al. 2011

IJMS

Self Cite

938

496

View full text Add to dashboard Cite

show abstract

“…At certain intensity of the external DC field, shedding, induced by electrokinetic instability, causes enhancement of the mixing inside a mixing chamber. Fu et al [48] proposed that critical strength of electric field for EKI flow can be significantly decreased in coated micro-channels. According to the research by Luo [49], the injection configuration of solutions has significant effect on the electrokinetic instability.…”

Section: Active Mixersmentioning

confidence: 99%

Fluid manipulation on the micro‐scale: Basics of fluid behavior in microfluidics

Novotný

Foret

2016

J of Separation Science

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Fluid manipulation on the micro-scale (microfluidics) is bringing new potential applications in a number of fields, including chemistry, biology and medicine. At sub-millimeter channel scale, some phenomena, unimportant at the macroscale, become an important force to consider when designing a microfluidics system. For example, the decrease in fluid mass causes the effects of viscosity to overcome the influence of inertia. Turbulent flow cannot be achieved at any realistic fluid velocity, making mixing a challenging task. The only phenomenon capable of blending liquids at microscale is diffusion and liquid streams can be flowed side-by-side for tens of minutes before they completely fuse together. The decrease in the channel size also leads to an increased surface-to-volume ratio, which increases the importance of surface effects, including adsorption, capillary action and surface wetting and/or electric double layer formation with related electrokinetic phenomena. While rivers cannot flow uphill, a stream of liquid can easily flow up against gravity inside a capillary. Similarly, the formation of electric double layer near the charged surface of a micro-channel or capillary can be applied for electrokinetic actuating. This review summarizes selected physical phenomena related to liquid-based (water solutions) microfluidics as described recently.

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“…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 [36][37][38][39][40]. In an attempt to improve the mixing performance of micromixers, Tai et al [39] developed a T-type mixer with parallelogram barriers within the microchannels.…”

Section: Introductionmentioning

confidence: 99%

Numerical analysis of a rapid magnetic microfluidic mixer

et al. 2011

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This paper presents a detailed numerical investigation of the novel active microfluidic mixer proposed by Wen et al. (Electrophoresis 2009, 30, 4179-4186). This mixer uses an electromagnet driven by DC or AC power to induce transient interactive flows between a water-based ferrofluid and DI water. Experimental results clearly demonstrate the mixing mechanism. In the presence of the electromagnet's magnetic field, the magnetic nanoparticles create a body force vector that acts on the mixed fluid. Numerical simulations show that this magnetic body force causes the ferrofluid to expand significantly and uniformly toward miscible water. The magnetic force also produces many extremely fine finger structures along the direction of local magnetic field lines at the interface in both upstream and downstream regions of the microchannel when the external steady magnetic strength (DC power actuation) exceeds 30 Oe (critical magnetic Peclet number Pe(m),cr = 2870). This study is the first to analyze these pronounced finger patterns numerically, and the results are in good agreement with the experimental visualization of Wen et al. (Electrophoresis 2009, 30, 4179-4186). The large interfacial area that accompanies these fine finger structures and the dominant diffusion effects occurring around the circumferential regions of fingers significantly enhance the mixing performance. The mixing ratio can be as high as 95% within 2.0 s. at a distance of 3.0 mm from the mixing channel inlet when the applied peak magnetic field supplied by the DC power source exceeds 60 Oe. This study also presents a sample implementation of AC power actuation in a numerical simulation, an experimental benchmark, and a simulation of DC power actuation with the same peak magnetic strength. The simulated flow structures of the AC power actuation agree well with the experimental visualization, and are similar to those produced by DC power. The AC and DC power actuated flow fields exhibited no significant differences. This numerical study suggests approaches to maximize the performance of the proposed rapid magnetic microfluidic mixer, and confirms its exciting potential for use in lab-on-a-chip systems.

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Electrokinetic instability effects in microchannels with and without nanofilm coatings

Cited by 11 publications

References 41 publications

Microfluidic Mixing: A Review

Microfluidic Mixing: A Review

Fluid manipulation on the micro‐scale: Basics of fluid behavior in microfluidics

Numerical analysis of a rapid magnetic microfluidic mixer

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