Electrokinetic instabilities in thin microchannels

Storey, Brian D.; Tilley, B. S.; Lin, Hao; Santiago, Juan G.

doi:10.1063/1.1823911

Cited by 52 publications

(73 citation statements)

References 9 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Next, we explore the effects of the length scales h, w and δ on the maximum conductivity gradient by analysing the quasi-one-dimensional spanwise diffusion of the centre stream in the domain bounded by y = ±w. In the stable nearly-parallel flow, we approximate the initial three-dimensional conductivity distribution of the centre stream (at the throat) as a one-dimensional diffuse top-hat distribution in the spanwise Storey et al (2005). Two-dimensional calculation, Ra e,c function of conductivity ratio varied from 10 to 1.5, from Lin et al (2004).…”

Section: Local Electric Rayleigh Number Scalingmentioning

confidence: 99%

“…¶ Three-dimensional calculation conductivity ratio of 10 from Lin et al (2004). Storey et al (2005), b also used by Oddy & Santiago (2005).…”

Section: Local Electric Rayleigh Number Scalingmentioning

confidence: 99%

“…They analysed the case of an electric field applied perpendicular to the conductivity gradient in a high-aspect-ratio microchannel. Storey et al (2005) presented a depth-averaged version of the Lin et al governing equations which compared well with the complete three-dimensional model for high-aspectratio channels. Chen et al (2005) presented preliminary experiments and detailed stability analyses using depth-averaged linearized equations for the study of convective instability in the T-shaped intersection of two microchannel flow streams.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Convective instability of electrokinetic flows in a cross-shaped microchannel

Posner¹,

Santiago²

2006

J. Fluid Mech.

Self Cite

128

132

View full text Add to dashboard Cite

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.

show abstract

Section: Local Electric Rayleigh Number Scalingmentioning

confidence: 99%

“…¶ Three-dimensional calculation conductivity ratio of 10 from Lin et al (2004). Storey et al (2005), b also used by Oddy & Santiago (2005).…”

Section: Local Electric Rayleigh Number Scalingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Convective instability of electrokinetic flows in a cross-shaped microchannel

Posner¹,

Santiago²

2006

J. Fluid Mech.

Self Cite

128

132

View full text Add to dashboard Cite

show abstract

“…Electrokinetic flows become unstable when the advection of the conductivity fields by electroviscous advection dominates the dissipative effects of viscosity and molecular diffusion. Full details of these models are provided in [32][33][34].…”

Section: Theorymentioning

confidence: 99%

“…Since the first reported observation of EKI in an electrokinetic microfluidic system by Oddy et al [30], many researchers have attempted to develop accurate models for predicting the onset of instability and its flow features, including its coherent wave structures and associated mixing rate. Santiago and co-workers [31][32][33][34] have employed experimental, analytical, and numerical techniques to investigate electrokinetic instabilities at the interface of two liquid streams in a microfluidic channel subjected to an electrical field perpendicular to the conductivity gradient. The results of these studies provide a fundamental insight into electrokinetic instabilities and identify the key factors and conditions governing its onset.…”

Section: Introductionmentioning

confidence: 99%

Micromixer utilizing electrokinetic instability‐induced shedding effect

et al. 2006

View full text Add to dashboard Cite

This paper presents a T-shaped micromixer featuring 45 degrees parallelogram barriers (PBs) within the mixing channel. The presented device obtains a rapid mixing of two sample fluids with conductivity ratio of 10:1 (sample concentration:running buffer concentration) by means of the electrokinetic instability-induced shedding effects which are produced when a direct current (DC) electric field of an appropriate intensity is applied. The presented device uses a single high-voltage power source to simultaneously drive and mix the sample fluids. The effectiveness of the mixer is characterized experimentally as a function of the applied electrical field intensity and the extent to which the PBs obstruct the mixing channel. The experimental results indicate that the mixing performance reaches 91% at a cross-section located 2.3 mm downstream of the T-junction when the barriers obstruct 4/5 of the channel width and an electrical field of 300 V/cm is applied. The micromixing method presented in this study provides a simple low-cost solution to mixing problems in lab-on-a-chip systems.

show abstract

Electrokinetic instability effects in microchannels with and without nanofilm coatings

Hong

Wen

et al. 2008

Electrophoresis

View full text Add to dashboard Cite

This paper presents a parametric experimental investigation into the electrokinetic instability (EKI) phenomenon within three different types of microfluidic device, namely T-type, cross-shaped, and cross-form with an expansion configuration. The critical electric field strength at which the EKI phenomenon is induced is examined as a function of the conductivity ratio, the microchannel width, the expansion ratio, and the surface treatment of the microchannel walls. It is found that the critical electric field strength associated with the onset of EKI is strongly dependent on the conductivity ratio of the two samples within the microfluidic device and reduces as the channel width increases. The surfaces of the microchannel walls are coated with hydrophilic or hydrophobic organic-based spin-on-glass (SOG) nanofilms for glass-based microchips. The experimental results indicate that no significant difference exists in the critical electric field strengths in the hydrophilic or hydrophobic SOG-coated microchannels, respectively. However, for a given conductivity ratio and microchannel width, the critical strength of the electric field is slightly lower in the SOG-coated microchannels than in the non-coated channels. In general, the results presented in this study demonstrate the potential for designing and controlling on-chip assays requiring the manipulation of samples with high conductivity gradients, and provide a useful general reference for avoiding EKI effects in capillary electrophoresis analysis applications.

show abstract

Electrokinetic instabilities in thin microchannels

Cited by 52 publications

References 9 publications

Convective instability of electrokinetic flows in a cross-shaped microchannel

Convective instability of electrokinetic flows in a cross-shaped microchannel

Micromixer utilizing electrokinetic instability‐induced shedding effect

Electrokinetic instability effects in microchannels with and without nanofilm coatings

Contact Info

Product

Resources

About