Electrokinetic preconcentration of particles and cells in microfluidic reservoirs

Harrison, H.B.; Lu, Xinglin; Patel, Saurin; Thomas, Cory; Todd, Andrew; Johnson, Mark A.; Raval, Yash S.; Tzeng, Tzuen‐Rong; Song, Yongxin; Wang, Junsheng; Li, Dongqing; Xuan, Xiangchun

doi:10.1039/c5an00105f

Cited by 33 publications

(26 citation statements)

References 64 publications

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“…IV B. Similar to that reported in our earlier work, 23 particles get trapped inside the circulations of ICEO and are further concentrated adjacent to the corners of the channel entrance. The latter phenomenon can be better viewed from the superimposed image in Fig.…”

Section: A Comparing the Depth-averaged Model Prediction With Experisupporting

confidence: 74%

“…19,20 This so-called electrothermal flow arises from the action of electric field on the inhomogeneous temperature-dependent fluid properties. 21,22 More recently, our group has reported an electrokinetic in-reservoir pre-concentration of particles and bacterial cells, 23 where Joule heating effects can be safely neglected due to the use of a low ionic concentration fluid. 24,25 We have attributed this phenomenon to the recirculating flow of induced charge electroosmosis (ICEO) at the channel entrance.…”

Section: Introductionmentioning

confidence: 99%

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Induced charge effects on electrokinetic entry flow

et al. 2017

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Electrokinetic flow, due to a nearly plug-like velocity profile, is the preferred mode for transport of fluids (by electroosmosis) and species (by electrophoresis if charged) in microfluidic devices. Thus far there have been numerous studies on electrokinetic flow within a variety of microchannel structures. However, the fluid and species behaviors at the interface of the inlet reservoir (i.e., the well that supplies the fluid and species) and microchannel are still largely unexplored. This work presents a fundamental investigation of the induced charge effects on electrokinetic entry flow due to the polarization of dielectric corners at the inlet reservoir-microchannel junction. We use small tracing particles suspended in a low ionic concentration fluid to visualize the electrokinetic flow pattern in the absence of Joule heating effects. Particles are found to get trapped and concentrated inside a pair of counter-rotating fluid circulations near the corners of the channel entrance. We also develop a depth-averaged numerical model to understand the induced charge on the corner surfaces and simulate the resultant induced charge electroosmosis (ICEO) in the horizontal plane of the microchannel. The particle streaklines predicted from this model are compared with the experimental images of tracing particles, which shows a significantly better agreement than those from a regular two-dimensional model. This study indicates the strong influences of the top/bottom walls on ICEO in shallow microchannels, which have been neglected in previous two-dimensional models.

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Section: A Comparing the Depth-averaged Model Prediction With Experisupporting

confidence: 74%

Section: Introductionmentioning

confidence: 99%

Induced charge effects on electrokinetic entry flow

et al. 2017

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“…It can even cause electrothermal flow15 in the form of counter-rotating vortices16171819 due to the action of electric field on the thermally induced fluid property gradients2021. Fluid circulations can also be produced in electrokinetic microchannel flow when there is a non-uniform surface property due to, for example, heterogeneous patterning2223, field effect2425 or induced charge effect2627282930.…”

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confidence: 99%

Electrokinetic instability in microchannel ferrofluid/water co-flows

Song

Zhou

et al. 2017

Sci Rep

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Electrokinetic instability refers to unstable electric field-driven disturbance to fluid flows, which can be harnessed to promote mixing for various electrokinetic microfluidic applications. This work presents a combined numerical and experimental study of electrokinetic ferrofluid/water co-flows in microchannels of various depths. Instability waves are observed at the ferrofluid and water interface when the applied DC electric field is beyond a threshold value. They are generated by the electric body force that acts on the free charge induced by the mismatch of ferrofluid and water electric conductivities. A nonlinear depth-averaged numerical model is developed to understand and simulate the interfacial electrokinetic behaviors. It considers the top and bottom channel walls’ stabilizing effects on electrokinetic flow through the depth averaging of three-dimensional transport equations in a second-order asymptotic analysis. This model is found accurate to predict both the observed electrokinetic instability patterns and the measured threshold electric fields for ferrofluids of different concentrations in shallow microchannels.

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“…5,6 More preferably, particles can be captured in a flowing suspension through the use of an external force, where the accumulated particles can be readily dispersed by either lowering (or switching off) the force field or increasing the flow rate. [2][3][4] A number of non-magnetic force fields, 1,7 including acoustic, 8,9 electric, [10][11][12][13] and optical [14][15][16] forces, have been demonstrated to enrich various types of particles and cells in microfluidic devices. Compared to these contactless methods, magnetic trapping of particles has several advantages such as low cost, heating free (except for electromagnets), and near independence of the suspending medium properties (e.g., ionic concentration and pH value).…”

Section: Introductionmentioning

confidence: 99%

Simultaneous diamagnetic and magnetic particle trapping in ferrofluid microflows via a single permanent magnet

Zhou

Kumar

et al. 2015

Biomicrofluidics

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Trapping and preconcentrating particles and cells for enhanced detection and analysis are often essential in many chemical and biological applications. Existing methods for diamagnetic particle trapping require the placement of one or multiple pairs of magnets nearby the particle flowing channel. The strong attractive or repulsive force between the magnets makes it difficult to align and place them close enough to the channel, which not only complicates the device fabrication but also restricts the particle trapping performance. This work demonstrates for the first time the use of a single permanent magnet to simultaneously trap diamagnetic and magnetic particles in ferrofluid flows through a T-shaped microchannel. The two types of particles are preconcentrated to distinct locations of the T-junction due to the induced negative and positive magnetophoretic motions, respectively. Moreover, they can be sequentially released from their respective trapping spots by simply increasing the ferrofluid flow rate. In addition, a three-dimensional numerical model is developed, which predicts with a reasonable agreement the trajectories of diamagnetic and magnetic particles as well as the buildup of ferrofluid nanoparticles.

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Electrokinetic preconcentration of particles and cells in microfluidic reservoirs

Cited by 33 publications

References 64 publications

Induced charge effects on electrokinetic entry flow

Induced charge effects on electrokinetic entry flow

Electrokinetic instability in microchannel ferrofluid/water co-flows

Simultaneous diamagnetic and magnetic particle trapping in ferrofluid microflows via a single permanent magnet

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