Electroosmotic Flow in a Microcapillary with One Solution Displacing Another Solution

Ren, Lu; Escobedo, Carlos; Li, Dongqing

doi:10.1006/jcis.2001.7809

Cited by 41 publications

(37 citation statements)

References 15 publications

(14 reference statements)

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“…This is not the case in our experiments: due to the relative high buffer concentration, the double-layer thickness (approximately 2 nm) is small compared to the channel height, therefore, there is no double-layer overlap. However, because of the tapered shape of the channels and the large difference in the buffer concentrations, pressure is build up in the channels [19] and the flow profile is not flat.…”

Section: Discussionmentioning

confidence: 99%

“…In fact the flow field is not uniform along the channel as a consequence of the variations in the cross-sectional area, the nonuniform electric field and the changing buffer concentration along the channel. The flow we generated is therefore not purely electroosmotic, in fact a pressure gradient is induced in the channel to ensure constant flow rate in different sections [19].…”

Section: Eof Measurementsmentioning

confidence: 99%

See 1 more Smart Citation

Electrokinetic pumping and detection of low‐volume flows in nanochannels

Mela¹,

Tas²,

Berenschot

et al. 2004

Electrophoresis

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Electrokinetic pumping of low-volume rates was performed on-chip in channels of small cross sectional area and height in the sub-microm range. The flow was detected with the current monitoring technique by monitoring the change in resistance of the fluid in the channel upon the electroosmosis-driven displacement of an electrolyte solution by a second electrolyte solution. Flow rates in the order of 0.1 pL/s were successfully generated and detected. The channels were fabricated with the sacrificial layer technology.

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Section: Discussionmentioning

confidence: 99%

Section: Eof Measurementsmentioning

confidence: 99%

Electrokinetic pumping and detection of low‐volume flows in nanochannels

Mela¹,

Tas²,

Berenschot

et al. 2004

Electrophoresis

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“…We infer the streamwise ensemble-average velocity of the flow in the east channel by tracking the displacement of scalars. Note that the bulk flow velocity in the east channel is difficult to quantify using bulk measurement methods such as current monitoring (see Huang, Gordon & Zare 1988;Ren, Escobedo & Li 2001;Devasenathipathy & Santiago 2005) as the flow has highly nonuniform conductivity and electric fields, resulting in non-uniform unsteady electroosmotic velocities near the walls. Only optical flow structure (or seed particle) tracking methods are possible.…”

Section: Velocity Fieldsmentioning

confidence: 99%

Convective instability of electrokinetic flows in a cross-shaped microchannel

Posner¹,

Santiago²

2006

J. Fluid Mech.

126

132

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We present a parametric experimental study of convective electrokinetic instability (EKI) in an isotropically etched, cross-shaped microchannel using quantitative epifluorescence imaging. The base state is a three-inlet, one-outlet electrokinetic focusing flow configuration where the centre sample stream and sheath flows have mismatched ionic conductivities. Electrokinetic flows with conductivity gradients become unstable when the electroviscous stretching and folding of conductivity interfaces grows faster than the dissipative effect of molecular diffusion. Scalar images, critical applied fields required for instability, and temporal and spatial scalar energy are presented for flows with a wide range of applied d.c. electric field and centre-tosheath conductivity ratios. These parameters impose variations of the electric Rayleigh number across four orders of magnitude. We introduce a scaling for charge density in the bulk fluid as a function of local maximum conductivity gradients in the flow. This scaling shows that the flow becomes unstable at a critical electric Rayleigh number (Ra e, = 205) and applies to a wide range of applied field and centre-tosheath conductivity ratios. This work is relevant to on-chip electrokinetic flows with conductivity gradients such as field amplified sample stacking, flow at the intersections of multi-dimensional assays, electrokinetic control and separation of sample streams with poorly specified chemistry, and low-Reynolds number micromixing.

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“…Similarly, Ren et al 25,26 have adopted the electrical circuit model in their investigations of two-fluid electroosmotic displacement flow whereby each fluid is represented by a resistance based on their conductivities. The underlying assumption for the model is that the two solutions must contain similar ionic species, albeit at different concentrations.…”

mentioning

confidence: 99%

“…Ren et al 25,26 have conducted displacement flow experiments with 0.1 mM lanthanum chloride (LaCl 3 ) solution and 0.1 mM potassium chloride (KCl) solution (solution pair with different ion species type) in two different flow directions. However, the displacement times for the flow in the forward and reverse flow directions were not reported.…”

mentioning

confidence: 99%

Electroosmotic flow hysteresis for dissimilar ionic solutions

Lim

Lam

2015

Biomicrofluidics

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Electroosmotic flow (EOF) with two or more fluids is commonly encountered in various microfluidics applications. However, no investigation has hitherto been conducted to investigate the hysteretic or flow direction-dependent behavior during the displacement flow of solutions with dissimilar ionic species. In this investigation, electroosmotic displacement flow involving dissimilar ionic solutions was studied experimentally through a current monitoring method and numerically through finite element simulations. The flow hysteresis can be characterized by the turning and displacement times; turning time refers to the abrupt gradient change of current-time curve while displacement time is the time for one solution to completely displace the other solution. Both experimental and simulation results illustrate that the turning and displacement times for a particular solution pair can be directional-dependent, indicating that the flow conditions in the microchannel are not the same in the two different flow directions. The mechanics of EOF hysteresis was elucidated through the theoretical model which includes the ionic mobility of each species, a major governing parameter. Two distinct mechanics have been identified as the causes for the EOF hysteresis involving dissimilar ionic solutions: the widening/sharpening effect of interfacial region between the two solutions and the difference in ion concentration distributions (and thus average zeta potentials) in different flow directions. The outcome of this investigation contributes to the fundamental understanding of flow behavior in microfluidic systems involving solution pair with dissimilar ionic species. V C 2015 AIP Publishing LLC. [http://dx

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Electroosmotic Flow in a Microcapillary with One Solution Displacing Another Solution

Cited by 41 publications

References 15 publications

Electrokinetic pumping and detection of low‐volume flows in nanochannels

Electrokinetic pumping and detection of low‐volume flows in nanochannels

Convective instability of electrokinetic flows in a cross-shaped microchannel

Electroosmotic flow hysteresis for dissimilar ionic solutions

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