On mixed electroosmotic-pressure driven flow and mass transport in microchannels

Bera, Subrata; Bhattacharyya, S.

doi:10.1016/j.ijengsci.2012.09.006

Cited by 34 publications

(17 citation statements)

References 30 publications

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“…The form of u in ; / in ; g in and f in are governed by the combined effect of a constant pressure gradient G and constant surface potential f. The inlet and outlet conditions can be derived in a similar manner as described in Bera and Bhattacharyya [23]. In determining the inlet and outlet boundary conditions, the pressure gradient is assumed to be constant and is determined by the non-dimensional quantity,…”

Section: Mathematical Modelmentioning

confidence: 99%

Combined electroosmosis-pressure driven flow and mixing in a microchannel with surface heterogeneity

Bhattacharyya

Bera

2015

Applied Mathematical Modelling

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a b s t r a c tWe investigate the combined pressure-driven electroosmotic flow near a wall roughness in the form of a rectangular block mounted on one wall of an infinitely long microchannel. The insulated rectangular block has a constant surface potential which is different from the surface potential of the remaining part of the channel walls. The characteristics for the electrokinetic flow are obtained by numerically solving the Navier-Stokes equations coupled with the Nernst-Planck equation for ion transport and the Poisson equation for electric field. Vortical flow develops above the block when the surface potential of the block is in opposite sign to that of the surface potential of the channel. The strength of the re-circulating vortex grows as the surface potential of the block increases. Vortical flow also depends on the Debye length when it is in the order of the channel height. The combined effects due to the geometrical modulation of the channel wall and heterogeneity in surface potential is found to produce a stronger vortex and hence a stronger mixing, as compared with the effect of either of these. The recirculating vortex, which appears on the upper face of the block, grows and the average electroosmotic velocity increases with the increase of the electrolyte concentration. The recirculating vortex does not appear when EDL is thick and the effect of over-potential of the block on electroosmosis is negligible. The loss of momentum near the obstacle is compensated by the electrostatic force near the EDL, which prevents flow separation upstream or downstream of the obstacle. The mixing performance of the present configuration is compared with several other cases of surface modulation. The impact of the imposed pressure gradient on the vortical flow due to surface heterogeneity is analyzed.

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Section: Mathematical Modelmentioning

confidence: 99%

Combined electroosmosis-pressure driven flow and mixing in a microchannel with surface heterogeneity

Bhattacharyya

Bera

2015

Applied Mathematical Modelling

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“…The H-S approximate model has been frequently used and validated for predicting the electroosmotic flow field. However, for the purpose of mixing evaluation, there are rare studies in which validity of this model for mixing performance has been examined [10,26]. In Fig.…”

Section: Helmholtz-smoluchowski Model: Accuracy and Validation For MImentioning

confidence: 99%

“…To determine the electro-osmotic flow field, in addition to the continuity and momentum equations, the equations that describe electrical potential and electric charges transfer need to be established and solved. Solving these equations for heterogeneous micro-channels either in geometry or properties, needs efficient numerical methods with significant computation cost [10,11], hence some simple modeling approach such as Helmholtz-Smoluchowski model has been proposed [12][13][14], which reduces the computational cost considerably. Another surface phenomenon which plays an important role in micro-fluidic systems is the slip of fluid on the solid surface.…”

Section: Introductionmentioning

confidence: 99%

Investigation of slip effects on electroosmotic mixing in heterogeneous microchannels based on entropy index

2019

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In this article electrokinetic mixing through heterogeneous microchannels has been studied and the effects of slip coefficient, zeta-potential, Debye-Hückel parameter and Reynolds number on mixing efficiency have been investigated. The microchannels studied here, have non-homogenous zeta-potential distribution at the wall, while other surface properties are considered to be homogenous. In order to investigate the electro-osmotic mixing, the Navier-Stokes, Nernst-Planck, Laplace and convection-diffusion equations have been solved numerically for velocity field, ions distribution, electrical potential and concentration field, respectively. The entropy of concentration distribution has been used as a quantitative index to evaluate the mixing performance. The results show that the behavior of electro-osmotic micromixers strongly depends on the amount and distribution of wall zeta-potential and in most cases the mixing efficiency increases with reduction of slip coefficient or Debye-Hückel or Reynolds number. It is found that in presence of slip, mixing efficiency decreases at low Reynolds numbers, while increases at high Reynolds numbers. Also, the accuracy of Helmholtz-Smoluchowski approximate model is investigated and it is found that the performance of the Helmholtz-Smoluchowski model in predicting the mixing efficiencies deteriorates for high wall zeta-potential or low values of Debye-Hückel parameter.

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“…A spectral element algorithm was established by Dutta et al (2002aDutta et al ( , 2002b for the solution of pressuredriven electro-osmotic flows in complex geometries. Bera and Bhattacharyya (2013) performed a detailed numerical simulation to analyze similar kind of flows with species transport in micro/nano-channels and studied the effects of Re for both thin and overlapped cases of EDL. Ebrahimi et al (2014) studied mixing and heat transfer characteristics of pressure drivenelectro-osmotic flow in a T-shaped micro-channel by carrying out a numerical simulation and predicted some means to improve efficiency of mixing in micro-channel.…”

Section: Introductionmentioning

confidence: 99%

Pressure-Driven Electro-Osmotic Flow and Mass Transport in Constricted Mixing Micro-Channels

Ahamed

Algahtani

Badruddin

et al. 2020

JAFM

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Both micro electro mechanical systems (MEMS) based and lab-on-a chip (LoC) devices demand efficient micro-scale mixing mechanisms for its effective control which necessitates the quality research towards more efficient designs. A new venture is investigated in those direction with mixing micro-channel constricted with rectangular block under pressure-driven electro-osmotic flow and is numerically simulated by a modified immersed boundary method (IBM), an alternative technique in computational fluid dynamics (CFD). The electro-osmotic flow elucidated by electrical double layer theory when simultaneously considered with pressure driven flow in micro channels can be effectively figured out by the solution of Navier-Stokes equations linked with Nernst-Planck and Poisson equations for transportation of ion and electric field respectively. In this study, the effect of varying the height of rectangular block on the flow and mixing performance are analyzed. A hybrid method, which is a combination of active and passive techniques, is introduced simultaneously in the microchannel by the electro-osmotic effects and channel constriction. The approach is on the basis of finite volume methodology on a staggered mesh. The governing equations are solved by a time-integration technique based on a fractional step method. The velocity fields are corrected by a pseudo-pressure term to ensure the continuity in each computational time step. The extent of mixing in every cross section of the micro channel is assessed by a suitable mixing efficiency parameter. This study has shed light on the most predominant factors that influence mixing efficiency in a micro-channel, such as geometry of the block, non-dimensional numbers (Reynolds number, Re and Peclet number, Pe), zeta potential, external electric field strength and electrical double layer (EDL) thickness. The maximum efficiency in this micro mixer design is found to be 51.3% for Reynolds number of 0.05 and Peclet number of 450 with the rectangular block height of 0.75. It is clear that both electro osmotic effects and flow perturbations due to channel constriction caused a remarkable improvement in mixing efficiency. The outcomes of this investigation are widely applicable in cooling of microchips, heat sinks of MEMS based devices, drug delivery applications and Deoxyribonucleic acid (DNA) hybridization. The present IBM model is validated by experimental and numerical results from the literature.

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On mixed electroosmotic-pressure driven flow and mass transport in microchannels

Cited by 34 publications

References 30 publications

Combined electroosmosis-pressure driven flow and mixing in a microchannel with surface heterogeneity

Combined electroosmosis-pressure driven flow and mixing in a microchannel with surface heterogeneity

Investigation of slip effects on electroosmotic mixing in heterogeneous microchannels based on entropy index

Pressure-Driven Electro-Osmotic Flow and Mass Transport in Constricted Mixing Micro-Channels

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