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. 2016 Jul 21;7(7):127.
doi: 10.3390/mi7070127.

Quantification of Vortex Generation Due to Non-Equilibrium Electrokinetics at the Micro/Nanochannel Interface: Particle Tracking Velocimetry

Seung Jun Lee  1 , Kilsung Kwon  2 , Tae-Joon Jeon  3 , Sun Min Kim  4 , Daejoong Kim  5
Affiliations

Quantification of Vortex Generation Due to Non-Equilibrium Electrokinetics at the Micro/Nanochannel Interface: Particle Tracking Velocimetry

Seung Jun Lee et al. Micromachines (Basel). .

Abstract

We describe a quantitative study of vortex generation due to non-equilibrium electrokinetics near a micro/nanochannel interface. The microfluidic device is comprised of a microchannel with a set of nanochannels. These perm-selective nanochannels induce flow instability and thereby produce strong vortex generation. We performed tracking visualization of fluorescent microparticles to obtain velocity fields. Particle tracking enables the calculation of an averaged velocity field and the velocity fluctuations. We characterized the effect of applied voltages and electrolyte concentrations on vortex formation. The experimental results show that an increasing voltage or decreasing concentration results in a larger vortex region and a strong velocity fluctuation. We calculate the normalized velocity fluctuation-whose meaning is comparable to turbulent intensity-and we found that it is as high as 0.12. This value is indicative of very efficient mixing, albeit with a small Reynolds number.

Keywords: microparticle; nanochannel; particle tracking velocimetry; vortex generation.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Schematic of the microfluidic device. The red rectangle indicates the region for the results in Figure 3, Figure 4 and Figure 6. The black rectangles indicate the region for the results in Figure 5.
Figure 2
Figure 2
(a) Particle path lines with no voltage and (b) particle path lines with an applied voltage of 150 V.
Figure 3
Figure 3
Velocity field particle tracking with (a) no applied voltage; (b) 50 V; (c) 100 V; and (d) 150 V.
Figure 4
Figure 4
Region of influence of vortex generation versus (a) applied voltage and (b) KCl concentration.
Figure 5
Figure 5
Speed distribution in (a) a non-vortex region and (b) a vortex region (see Figure 1).
Figure 6
Figure 6
Normalized velocity fluctuation versus (a) applied voltage and (b) KCl concentration.
See this image and copyright information in PMC

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