Electrophoresis of a colloidal sphere in a circular cylindrical pore

Keh, Huan J.; Chiou, Jinn Y.

doi:10.1002/aic.690420520

Cited by 83 publications

(99 citation statements)

References 24 publications

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“…Although the concentric cavity is an idealized abstraction of some real systems, the result of boundary effect on the electrophoretic velocity of a charged sphere obtained in this geometry [28] agrees with that for a circular cylindrical pore [29]. The geometric symmetry in this model system allows closed-form formulas for the EMP force and migration velocity of the confined particle to be obtained in Equations (15) and (20), respectively.…”

Section: Introductionmentioning

confidence: 63%

Electromagnetophoresis of a Colloidal Sphere in a Spherical Cavity

Hsieh¹,

Keh²

2014

JEMAA

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The quasi-steady electromagnetophoretic motion of a spherical colloidal particle positioned at the center of a spherical cavity filled with a conducting fluid is analyzed at low Reynolds number. Under uniformly applied electric and magnetic fields, the electric current and magnetic flux density distributions are solved for the particle and fluid phases of arbitrary electric conductivities and magnetic permeabilities. Applying a generalized reciprocal theorem to the Stokes equations modified with the resulted Lorentz force density and considering the contribution of the magnetic Maxwell stress to the force exerted on the particle, which turns out to be important, we obtain a closed-form formula for the migration velocity of the particle valid for an arbitrary value of the particle-to-cavity radius ratio. The particle velocity in general decreases monotonically with an increase in this radius ratio, with an exception for the case of a particle with high electric conductivity and low magnetic permeability relative to the suspending fluid. The asymptotic behaviors of the boundary effect on the electromagnetophoretic force and mobility of the confined particle at small and large radius ratios are discussed.

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Section: Introductionmentioning

confidence: 63%

Electromagnetophoresis of a Colloidal Sphere in a Spherical Cavity

Hsieh¹,

Keh²

2014

JEMAA

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“…Thus, our third test concerns a non-conducting spherical particle of radius a driven by electrophoresis within a straight cylinder of radius b. Our numerical result was compared with the analytical result reported by Keh and Chiou [34], who found the fundamental solution and then applied the Fourier transform and a collocation method to solve the problem. The cylinder in our test was truncated so that its length is six times its own diameter.…”

Section: Code Validationmentioning

confidence: 96%

Effect of direct current dielectrophoresis on the trajectory of a non‐conducting colloidal sphere in a bent pore

House

Luo

2011

Electrophoresis

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Dielectrophoresis has shown a wide range of applications in microfluidic devices. Force approximations utilizing the point-dipole method in dielectrophoresis have provided convenient predictions for particle motion by neglecting interactions between the particle and its surrounding electric and flow fields. The validity of this approach, however, is unclear when the particle size is comparable to the characteristic length of the channel and when the particle is in close proximity to the channel wall. To address this issue, we apply an accurate numerical approach based on the boundary-element method (BEM) to solve the coupled electric field, flow, and particle motion. This method can handle much closer particle-wall distances than the other numerical approaches such as the finite-element method. Using the BEM and integrating the Maxwell stress tensor, we simulate an electrokinetic, spherical particle moving within a bent cylindrical pore to investigate how the dielectrophoretic force affects the particle's trajectory. In the simulation, both the particle and the channel wall are non-conducting, and the electric double layers adjacent to the solid surfaces are assumed to be thin with respect to the particle radius and particle-wall gap. The results show that as the particle comes close to the wall, its finite size has an increasingly important effect on its own transient motion and the point-dipole approximation may lead to significant error.

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“…In this work, the authors use a convergingstraight-diverging PDMS channel and find that larger particles are retarded at the sidewalls of the channel due to viscous forces, which is in good agreement with theoretical results. When the particle-wall separation decreases further, theory predicts an increase in particle electrophoretic velocity Keh and Chiou 1996;Yariv and Brenner 2003a;Majumder et al 2007). Furthermore, Qian et al (2006) theoretically study the electrophoretic motion of a spherical particle in a nanotube with a converging-diverging section, finding that particle electrophoretic mobility becomes spatially dependent, a mechanism that the authors propose to enhance particle separation .…”

Section: Introductionmentioning

confidence: 99%

“…There have been many studies concerning corrections, which arise in this setting (Keh and Chiou 1996;Yariv and Brenner 2002;Ye et al 2002;Yariv and Brenner 2003a, b;Ye and Li 2004). In general, the equations describing the coupled electrokinetic and hydrodynamic coupling are nonlinear and difficult to handle analytically, often requiring solution by advanced CFD numerical methods.…”

Section: Electrokinetic Separation Datamentioning

confidence: 99%

“…It has been shown that the presence of a channel wall can affect the particle electrophoretic motion by coupled hydrodynamic and electrostatic effects. For example, in the thin EDL limit, theory predicts that a particle electrophoretic velocity is reduced by nonconducting channel walls (Keh and Anderson 1985;Keh and Chiou 1996;Yariv and Brenner 2002;Yariv and Brenner 2003b). An experimental investigation that supports this theory can be found in Xuan et al (2006), where the authors study wall effects in microchannels on the electrophoretic motion of polystyrene particles of comparable size.…”

Section: Introductionmentioning

confidence: 99%

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Experimental study of the separation behavior of nanoparticles in micro- and nanochannels

Napoli

Atzberger

Pennathur

2010

Microfluid Nanofluid

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In this article, we investigate the effects of pH, ionic strength, and channel height on the mobility and diffusivity of charged spherical particles within planar microfluidic channels. Specifically, we report results of a broad experimental study on the transport and separation behavior of 50 and 100 nm spherical carboxylated polystyrene nanoparticles, confined in 20 lm, 1 lm, and 250 nm deep fluidic channels. We find that pH, ionic strength, and channel height have coupled impacts on mobility changes. In particular, we show that, depending on pH, the dependence of particle mobility on channel size can have opposing behavior. In addition, we also show that at the nanoscale, at lower ionic strengths, there is a substantial increase in mobility, due to enhanced electric fields within the nanochannels. These effects are important to understand in order to avoid potential downfalls in terms of separation efficiency as well as design for better tuning of separation performance in micro-and nanochannels. Finally, we propose a method to estimate the effective zeta potential of spherical particles from measured electrophoretic mobility data. This could prove useful in characterizing a heterogeneous collection of particles having a distribution over a range of values of the zeta potential.

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Electrophoresis of a colloidal sphere in a circular cylindrical pore

Abstract: The electrophoretic motion of a dielectric sphere along the centerline of a long circular cylindrical pore is studied theoretically.

Cited by 83 publications

References 24 publications

Electromagnetophoresis of a Colloidal Sphere in a Spherical Cavity

Electromagnetophoresis of a Colloidal Sphere in a Spherical Cavity

Effect of direct current dielectrophoresis on the trajectory of a non‐conducting colloidal sphere in a bent pore

Experimental study of the separation behavior of nanoparticles in micro- and nanochannels

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