Thermal Effect on Microchannel Electro-osmotic Flow With Consideration of Thermodiffusion

2015 ◽  
Vol 137 (9) ◽  
Author(s):  
Yi Zhou ◽  
Yongqi Xie ◽  
Chun Yang ◽  
Yee Cheong Lam
Keyword(s):  
Charge Density ◽  
Thermal Effect ◽  
Temperature Difference ◽  
Electrical Potential ◽  
Ionic Concentration ◽  
Free Charge ◽  
Regular Perturbation ◽  
Osmotic Flow ◽  
Ionic Distribution ◽  
Electro Osmotic Flow

Electro-osmotic flow (EOF) is widely used in microfluidic systems. Here, we report an analysis of the thermal effect on EOF under an imposed temperature difference. Our model not only considers the temperature-dependent thermophysical and electrical properties but also includes ion thermodiffusion. The inclusion of ion thermodiffusion affects ionic distribution, local electrical potential, as well as free charge density, and thus has effect on EOF. In particular, we formulate an analytical model for the thermal effect on a steady, fully developed EOF in slit microchannel. Using the regular perturbation method, we solve the model analytically to allow for decoupling several physical mechanisms contributing to the thermal effect on EOF. The parametric studies show that the presence of imposed temperature difference/gradient causes a deviation of the ionic concentration, electrical potential, and electro-osmotic velocity profiles from their isothermal counterparts, thereby giving rise to faster EOF. It is the thermodiffusion induced free charge density that plays a key role in the thermodiffusion induced electro-osmotic velocity.

scholarly journals Evaluation of electro-osmotic flow in a nanochannel via semi-analytical method

2012 ◽  
Vol 16 (5) ◽  
pp. 1297-1302 ◽  
Author(s):  
Payam Jalili ◽  
Domairry Ganji ◽  
Bahram Jalili ◽  
Domiri Ganji
Keyword(s):  
Shear Stress ◽  
Analytical Method ◽  
Homotopy Perturbation Method ◽  
Numerical Solutions ◽  
Electrical Potential ◽  
Osmotic Flow ◽  
Homotopy Perturbation ◽  
Stress Profiles ◽  
Electro Osmotic Flow ◽  
Cation Distributions

In this paper, equations due to anion and cation distributions, electrical potential and shear stress profiles in a nanochannel are formed for 1-D electro-osmotic flow, and solved by homotopy perturbation method. Results are compared with numerical solutions.

A Continuum Theory for Simulation of Ionic-Strength-Sensitive Hydrogel for BioMEMS Application

2009 ◽  
Vol 74 ◽  
pp. 21-24
Author(s):  
Fu Kun Lai ◽  
Hua Li
Keyword(s):  
Ionic Strength ◽  
Charge Density ◽  
Electrical Potential ◽  
Continuum Theory ◽  
Ionic Concentration ◽  
Fixed Charge ◽  
Buffer Solution ◽  
Fixed Charge Density ◽  
Flux System ◽  
Smart Hydrogel

A continuum multiphysics theory is presented for simulation of the ionic-strength-sensitive hydrogel and surrounding solution. The theory considers the coupled effects of chemical, electrical and mechanical multi-energy domains on the swelling behavior of the ionic-strength-sensitive hydrogel and is thus termed the multi-effect-coupling ionic-strength-stimuli (MECis) model. The MECis model consists of several governing equations, including Nernst-Planck flux system, Poisson equation, fixed charge density and mechanical equilibrium equation, in which the effect of the ionic strength is incorporated into the governing equation of diffusive flux and fixed charge. The theory is capable of simulating the swelling/shrinking behavior of smart hydrogel in buffer solution subject to the change in the ionic strength, and providing the distribution of the ionic concentration and electrical potential for applications of BioMEMS design. Apart from the ionic strength as the main stimulus, the influence of several parameters is discussed in detail, including the initial fixed charge density and Young’s modulus of the hydrogel.

Dispersion coefficient in an electro-osmotic flow of a viscoelastic fluid through a microchannel with a slowly varying wall zeta potential

2018 ◽  
Vol 839 ◽  
pp. 348-386 ◽  
Author(s):  
J. C. Arcos ◽  
F. Méndez ◽  
E. G. Bautista ◽  
O. Bautista
Keyword(s):  
Dispersion Coefficient ◽  
Fluid Model ◽  
Perturbation Technique ◽  
Debye Length ◽  
Rheological Behaviour ◽  
Governing Equations ◽  
Regular Perturbation ◽  
Axial Distribution ◽  
Osmotic Flow ◽  
Electro Osmotic Flow

The dispersion coefficient of a passive solute in a steady-state pure electro-osmotic flow (EOF) of a viscoelastic liquid, whose rheological behaviour follows the simplified Phan-Thien–Tanner (sPTT) model, along a parallel flat plate microchannel, is studied. The walls of the microchannel are assumed to have modulated and low $\unicode[STIX]{x1D701}$ potentials, which vary slowly in the axial direction in a sinusoidal manner. The flow field required to obtain the dispersion coefficient was solved using the lubrication approximation theory (LAT). The solution of the electric potential is based on the Debye–Hückel approximation for a symmetric $(z:z)$ electrolyte. The viscoelasticity of the fluid is observed to notably amplify the axial distribution of the effective dispersion coefficients due to the variation in the $\unicode[STIX]{x1D701}$ potentials of the walls. The problem was formulated for two cases: when the Debye layer thickness (EDL) was on the order of unity (thick EDL) and in the limit where the thickness of the EDL was very small compared with the height of the microchannel (thin EDL limit). Due to the coupling between the nonlinear governing equations and the sPTT fluid model, they were replaced by their approximate linearized forms and solved in the limit of $\unicode[STIX]{x1D700}\ll 1$ using the regular perturbation technique. Here $\unicode[STIX]{x1D700}$ is the amplitude of the sinusoidal function of the $\unicode[STIX]{x1D701}$ potentials. Additionally, the numerical solution of the simplified governing equations was also obtained for $\unicode[STIX]{x1D700}=O(1)$ and compared with the approximate solution, showing excellent agreement for $0\leqslant \unicode[STIX]{x1D700}\leqslant 0.3$. Note that the dispersion coefficient primarily depends on the Deborah number, on the ratio of the half-height of the microchannel to the Debye length, and on the assumed variation in the $\unicode[STIX]{x1D701}$ potentials of the walls.

LATTICE BOLTZMANN SIMULATIONS OF MIXING ENHANCEMENT BY THE ELECTRO-OSMOTIC FLOW IN MICROCHANNELS

2005 ◽  
Vol 19 (28n29) ◽  
pp. 1515-1518 ◽  
Author(s):  
JINKU WANG ◽  
MORAN WANG ◽  
ZHIXIN LI
Keyword(s):  
Fluid Flow ◽  
Lattice Boltzmann ◽  
Potential Distribution ◽  
Electrical Potential ◽  
Mixing Enhancement ◽  
Lattice Boltzmann Methods ◽  
Osmotic Flow ◽  
Lattice Boltzmann Simulations ◽  
Simulation Results ◽  
Electro Osmotic Flow

The Lattice Boltzmann methods are used to study the mixing enhancements by the electro-osmotic flow in microchannel. Three sets of lattice evolution methods are performed for the fluid flow, for the electrical potential distribution, and for the concentration propagation. The simulation results show that the electro-osmotic flow induces y-directional velocity which enhances the mixing in microchannels. The mixing enhancement is related with the surface zeta potential arrangement and the external electric field strength.

Electro-Osmotic Flow in Reservoir-Connected Flat Microchannels With Non-Uniform Zeta Potential

2006 ◽  
Vol 128 (6) ◽  
pp. 1133-1143 ◽  
Author(s):  
S. A. Mirbozorgi ◽  
H. Niazmand ◽  
M. Renksizbulut
Keyword(s):  
Zeta Potential ◽  
Electric Potential ◽  
Stokes Equations ◽  
Planck Equation ◽  
Ionic Concentration ◽  
Complex Flow ◽  
Layer Potential ◽  
Osmotic Flow ◽  
Zeta Potentials ◽  
Electro Osmotic Flow

The effects of non-uniform zeta potentials on electro-osmotic flows in flat microchannels have been investigated with particular attention to reservoir effects. The governing equations, which consist of a Laplace equation for the distribution of external electric potential, a Poisson equation for the distribution of electric double layer potential, the Nernst-Planck equation for the distribution of charge density, and modified Navier-Stokes equations for the flow field are solved numerically for an incompressible steady flow of a Newtonian fluid using the finite-volume method. For the validation of the numerical scheme, the key features of an ideal electro-osmotic flow with uniform zeta potential have been compared with analytical solutions for the ionic concentration, electric potential, pressure, and velocity fields. When reservoirs are included in the analysis, an adverse pressure gradient is induced in the channel due to entrance and exit effects even when the reservoirs are at the same pressure. Non-uniform zeta potentials lead to complex flow fields, which are examined in detail.

Electro-osmotic flow in hydrophobic nanochannels

2019 ◽  
Vol 21 (41) ◽  
pp. 23036-23043 ◽  
Author(s):  
Elena F. Silkina ◽  
Evgeny S. Asmolov ◽  
Olga I. Vinogradova
Keyword(s):  
Charge Density ◽  
Surface Potential ◽  
Analytical Theory ◽  
Osmotic Flow ◽  
Hydrodynamic Slip ◽  
Diffuse Layers ◽  
Electro Osmotic Flow

An analytical theory of electroosmosis in hydrophobic nanochannels of large surface potential/charge density incorporates a mobility of adsorbed charges and hydrodynamic slip, and is valid both for thin and strongly overlapping diffuse layers.

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