On steady two-fluid electroosmotic flow with full interfacial electrostatics

Choi, Wonsuk; Sharma, Ashutosh; Qian, Shizhi; Lim, Geunbae; Joo, Sang Woo

doi:10.1016/j.jcis.2011.01.107

Cited by 39 publications

(35 citation statements)

References 18 publications

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“…The dimensionless parameters (Z R , E O , De, E R and G) employed in generating the following results are obtained based on the physically realistic ranges of the parameters [19,20] We vary all the dimensionless parameters, Z R , E R , E O , and De, for a very wide range to uncover the importance of the ratio of the zeta-potentials at the interfaces, the strength of the applied field and resulting flow rate, and the film thickness on the modes of the instabilities.…”

Section: Resultsmentioning

confidence: 99%

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Surface instability of a thin electrolyte film undergoing coupled electroosmotic and electrophoretic flows in a microfluidic channel

et al. 2011

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We consider the stability of a thin liquid film with a free charged surface resting on a solid charged substrate by performing a general Orr-Sommerfeld (O-S) analysis complemented by a long-wave (LW) analysis. An externally applied field generates an electroosmotic flow (EOF) near the solid substrate and an electrophoretic flow (EPF) at the free surface. The EPF retards the EOF when both the surfaces have the same sign of the potential and can even lead to the flow reversal in a part of the film. In conjunction with the hydrodynamic stress, the Maxwell stress is also considered in the problem formulation. The electrokinetic potential at the liquid-air and solid-liquid interfaces is modelled by the Poisson-Boltzmann equation with the Debye-Hückel approximation. The O-S analysis shows a finite-wavenumber shear mode of instability when the inertial forces are strong and an LW interfacial mode of instability in the regime where the viscous force dominates. Interestingly, both the modes are found to form beyond a critical flow rate. The shear (interfacial) mode is found to be dominant when the film is thick (thin), the electric field applied is strong (weak), and the zeta-potentials on the liquid-air and solid-liquid interfaces are high (small). The LW analysis predicts the presence of the interfacial mode, but fails to capture the shear mode. The change in the propagation direction of the interfacial mode with the zeta-potential is predicted by both O-S and LW analyses. The parametric range in which the LW analysis is valid is thus demonstrated.

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Section: Resultsmentioning

confidence: 99%

“…The directions of these EOF and EPF are opposite (same) for the same (opposite) signs of the surface potentials on a fixed wall and on a mobile surface. The EOF is caused by the force on the counter-ion charge whereas electrophoresis of a mobile surface is caused by the force acting on the surface (particle) charge [19,20].…”

Section: Introductionmentioning

confidence: 99%

Surface instability of a thin electrolyte film undergoing coupled electroosmotic and electrophoretic flows in a microfluidic channel

et al. 2011

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“…The interfacial electrostatics is an important factor which affects the stability behavior of the two-liquid system. Choi et al (2011) have provided the base state of the system along with complete interfacial electrostatics by incorporating the Maxwell stress but have not considered the stability analysis of the interface. A complete study of instabilities at a free surface (Mayur et al 2012) and the base state of an air-liquid interface in 3D microchannels (Mayur et al 2014a) has been developed in the case of a DC electric field.…”

Section: Introductionmentioning

confidence: 99%

“…1). The interface is represented by y ¼ h x; t ð Þ: The zeta potential of the substrate at the upper and lower walls is represented by f u and f b ; respectively; f I and Q I are the zeta potential and the surface charge density present at the interface, respectively, (Choi et al 2011) and are taken as independent parameters. In the experimental studies of the interface between two immiscible electrolyte solutions (ITIES), Samec et al (1985) showed that for a given interface zeta potential (f I ), the surface charge density (Q I ) can be varied by varying the electrolyte concentrations.…”

Section: Introductionmentioning

confidence: 99%

Long-wave interface instabilities of a two-liquid DC electroosmotic system for thin films

Navarkar

Amiroudine

Mayur

et al. 2015

Microfluid Nanofluid

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Instabilities of the interface between two thin liquid films under DC electroosmotic flow are investigated using linear stability analysis followed by an asymptotic analysis in the long-wave limit. The two-liquid system is bounded by two rigid plates which act as substrates. The Boltzmann charge distribution is considered for the two electrolyte solutions and gives rise to a potential distribution in these liquids. The effect of van der Waals interactions in these thin films is incorporated in the momentum equations through the disjoining pressure. Marginal stability and growth rate curves are plotted in order to identify the thresholds for the control parameters when instabilities set in. If the upper liquid is a dielectric, the applied electric field can have stabilizing or destabilizing effects depending on the viscosity ratio due to the competition between viscous and electric forces. For viscosity ratio equal to unity, the stability of the system gets disconnected from the electric parameters like interface zeta potential and electric double-layer thickness. As expected, disjoining pressure has a destabilizing effect, and capillary forces have stabilizing effect. The overall stability trend depends on the complex contest between all the above-mentioned parameters. The present study can be used to tune these parameters according to the stability requirement.

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“…The sharp change at this layer can often be described by a zeta potential jump across the interface. Theoretical studies on steady two-fluid EOF with full interfacial electrostatics [33] show the importance of the Maxwell stress on interface. Very recently, the free surface instability in EOF of ultrathin liquid films was investigated by Mayur et al [34].…”

Section: Introductionmentioning

confidence: 99%

Transient electroosmotic flow of general Maxwell fluids through a slit microchannel

Jian

Chang

et al. 2013

Z. Angew. Math. Phys.

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Abstract. Using Laplace transform method, semi-analytical solutions are presented for transient electroosmotic flow of Maxwell fluids between micro-parallel plates. The solution involves solving the linearized Poisson-Boltzmann equation, together with the Cauchy momentum equation and the Maxwell constitutive equation considering the depletion effect produced by the interaction between macro-molecules of the Maxwell fluids and the channel surface. The overall flow is divided into depletion layer and bulk flow outside of depletion layer. In addition, the Maxwell stress is incorporated to describe the boundary condition at the interface. The velocity expressions of these two layers were obtained respectively. By numerical computations of inverse Laplace transform, the influences of viscosity ratio μ, density ratio ρ, dielectric constant ratio ε of layer II to layer I, relaxation timeλ 1 , interface charge density jump Q, and interface zeta potential difference Δψ on transient velocity amplitude are presented. Mathematics Subject Classification (2000). 76A05 · 76D05 · 76W05.

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On steady two-fluid electroosmotic flow with full interfacial electrostatics

Cited by 39 publications

References 18 publications

Surface instability of a thin electrolyte film undergoing coupled electroosmotic and electrophoretic flows in a microfluidic channel

Surface instability of a thin electrolyte film undergoing coupled electroosmotic and electrophoretic flows in a microfluidic channel

Long-wave interface instabilities of a two-liquid DC electroosmotic system for thin films

Transient electroosmotic flow of general Maxwell fluids through a slit microchannel

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