A numerical investigation of transient electro-osmotic flow in rectangular microchannels: A comparison of different models

2010 ◽  
Vol 224 (8) ◽  
pp. 1655-1663 ◽  
Author(s):  
R Kamali ◽  
M Eslami
Keyword(s):  
Zeta Potential ◽  
Transition Period ◽  
Effective Parameters ◽  
Start Time ◽  
Rectangular Microchannels ◽  
Steady State Condition ◽  
Osmotic Flow ◽  
Aspect Ratios ◽  
Poisson Boltzmann Equation ◽  
Electro Osmotic Flow

Transient electro-osmotic flow in rectangular microchannels is investigated numerically in this article. The complete Poisson—Boltzmann equation along with the time-dependent momentum equation is solved using the finite-difference method. Moreover, linearized equations based on the Debye—Huckle assumption are also solved to compare with the available analytical approximate solutions. The effects of different parameters such as wall zeta potential, non-dimensional electrokinetic width, and channel aspect ratio are also studied. It is shown that the Debye—Huckle approximation is not only valid for small values of zeta potential, but also the channel hydraulic diameter should be large enough with respect to electrical double layer (EDL) thickness. In addition, the flow behaviour at higher values of zeta potential is shown to be completely different from what available analytical solutions predict. Effective parameters on the transition period from the start time to the steady-state condition are also discussed. On the other hand, a comparison between the present numerical solution and the results of slip velocity approximation reveals that the slip model could be only used for very large values of non-dimensional electro-kinetic width. Finally, velocity distributions in channels of different aspect ratios are provided and discussed.

scholarly journals Towards bio-inspired artificial muscle: a mechanism based on electro-osmotic flow simulated using dissipative particle dynamics

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Ramin Zakeri
Keyword(s):  
Zeta Potential ◽  
Electric Field ◽  
Dissipative Particle Dynamics ◽  
Artificial Muscle ◽  
Particle Dynamics ◽  
Polymer Membrane ◽  
Channel Width ◽  
Micro Channel ◽  
Osmotic Flow ◽  
Electro Osmotic Flow

AbstractOne of the unresolved issues in physiology is how exactly myosin moves in a filament as the smallest responsible organ for contracting of a natural muscle. In this research, inspired by nature, a model is presented consisting of DPD (dissipative particle dynamics) particles driven by electro-osmotic flow (EOF) in micro channel that a thin movable impermeable polymer membrane has been attached across channel width, thus momentum of fluid can directly transfer to myosin stem. At the first, by validation of electro-osmotic flow in micro channel in different conditions with accuracy of less than 10 percentage error compared to analytical results, the DPD results have been developed to displacement of an impermeable polymer membrane in EOF. It has been shown that by the presence of electric field of 250 V/m and Zeta potential − 25 mV and the dimensionless ratio of the channel width to the thickness of the electric double layer or kH = 8, about 15% displacement in 8 s time will be obtained compared to channel width. The influential parameters on the displacement of the polymer membrane from DPD particles in EOF such as changes in electric field, ion concentration, zeta potential effect, polymer material and the amount of membrane elasticity have been investigated which in each cases, the radius of gyration and auto correlation velocity of different polymer membrane cases have been compared together. This simulation method in addition of probably helping understand natural myosin displacement mechanism, can be extended to design the contraction of an artificial muscle tissue close to nature.

Time-Periodic Electro-Osmotic Flow With Nonuniform Surface Charges

2019 ◽  
Vol 141 (8) ◽  
Author(s):  
Hyunsung Kim ◽  
Aminul Islam Khan ◽  
Prashanta Dutta
Keyword(s):  
Zeta Potential ◽  
Analytical Model ◽  
Potential Distribution ◽  
Step Change ◽  
Creeping Flow ◽  
Function Technique ◽  
Osmotic Flow ◽  
Nonuniform Surface ◽  
Time Periodic ◽  
Electro Osmotic Flow

Mixing in a microfluidic device is a major challenge due to creeping flow, which is a significant roadblock for development of lab-on-a-chip device. In this study, an analytical model is presented to study the fluid flow behavior in a microfluidic mixer using time-periodic electro-osmotic flow. To facilitate mixing through microvortices, nonuniform surface charge condition is considered. A generalized analytical solution is obtained for the time-periodic electro-osmotic flow using a stream function technique. The electro-osmotic body force term is accounted as a slip boundary condition on the channel wall, which is a function of time and space. To demonstrate the applicability of the analytical model, two different surface conditions are considered: sinusoidal and step change in zeta potential along the channel surface. Depending on the zeta potential distribution, we obtained diverse flow patterns and vortices. The flow circulation and its structures depend on channel size, charge distribution, and the applied electric field frequency. Our results indicate that the sinusoidal zeta potential distribution provides elliptical shaped vortices, whereas the step change zeta potential provides rectangular shaped vortices. This analytical model is expected to aid in the effective micromixer design.

scholarly journals Applicability of electro-osmotic flow for the analysis of the surface zeta potential

RSC Advances ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 6777-6789 ◽  
Author(s):  
Olivija Plohl ◽  
Lidija Fras Zemljič ◽  
Sanja Potrč ◽  
Thomas Luxbacher
Keyword(s):  
Zeta Potential ◽  
Bulk Properties ◽  
Electrokinetic Phenomena ◽  
Osmotic Flow ◽  
Electro Osmotic Flow

Detail comparison of two different electrokinetic phenomena EOF and SP method for the SZP determination with taking into account various materials with different surface and bulk properties.

scholarly journals Electro-osmotic flow of a third-grade fluid past a channel having stretching walls

2019 ◽  
Vol 8 (1) ◽  
pp. 56-64 ◽  
Author(s):  
Mamata Parida ◽  
Sudarsan Padhy
Keyword(s):  
Differential Equation ◽  
Boltzmann Equation ◽  
Linear Partial Differential Equation ◽  
Third Grade ◽  
Third Grade Fluid ◽  
Osmotic Flow ◽  
Grade Fluid ◽  
Poisson Boltzmann ◽  
Poisson Boltzmann Equation ◽  
Electro Osmotic Flow

Abstract The electro-osmotic flow of a third grade fluid past a channel having stretching walls has been studied in this paper. The channel height is taken much greater than the thickness of the electric double layer comprising of the Stern and diffuse layers. The equations governing the flow are obtained from continuity equation, the Cauchy’s momentum equation and the Poisson-Boltzmann equation. The Debye-Hückel approximation is adopted to linearize the Poisson-Boltzmann equation. Suitable similarity transformations are used to reduce the resulting non-linear partial differential equation to ordinary differential equation. The reduced equation is solved numerically using damped Newton’s method. The results computed are presented in form of graphs.

Transient electro-osmotic flow of generalized Maxwell fluids in a straight pipe of circular cross section

Open Physics ◽  
2014 ◽  
Vol 12 (6) ◽  
Author(s):  
Shaowei Wang ◽  
Moli Zhao ◽  
Xicheng Li
Keyword(s):  
Fractional Derivative ◽  
Integral Transform ◽  
Capillary Tube ◽  
Circular Cross Section ◽  
Maxwell Fluid ◽  
Navier Stokes Equation ◽  
Transform Method ◽  
Osmotic Flow ◽  
Poisson Boltzmann Equation ◽  
Electro Osmotic Flow

AbstractThe transient electro-osmotic flow of a generalized Maxwell fluid with fractional derivative in a narrow capillary tube is examined. With the help of an integral transform method, analytical expressions are derived for the electric potential and transient velocity profile by solving the linearized Poisson-Boltzmann equation and the Navier-Stokes equation. It was shown that the distribution and establishment of the velocity consists of two parts, the steady part and the unsteady one. The effects of relaxation time, fractional derivative parameter, and the Debye-Hückel parameter on the generation of flow are shown graphically and analyzed numerically. The velocity overshoot and oscillation are observed and discussed.

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.

Exact solution of an electro-osmotic flow problem in a cylindrical channel of polymer electrolyte membranes

2009 ◽  
Vol 465 (2109) ◽  
pp. 2663-2679 ◽  
Author(s):  
Peter Berg ◽  
Kehinde Ladipo
Keyword(s):  
Polymer Electrolyte ◽  
Cylindrical Channel ◽  
Polymer Electrolyte Membranes ◽  
Osmotic Flow ◽  
Counter Ions ◽  
Electrolyte Membranes ◽  
Poisson Boltzmann ◽  
Poisson Boltzmann Equation ◽  
Analytical Expressions ◽  
Electro Osmotic Flow

The electric potential of counter-ions (protons) in an infinite cylindrical channel is presented as a solution of the Poisson–Boltzmann equation, involving a constant ion charge density along the wall. The distribution of protons is derived and used subsequently to compute the velocity profile and mass flow rate of the corresponding electro-osmotic flow, driven by an electric field. Analytical expressions are derived for all quantities, including the conductivity and water drag coefficient. This analysis relates especially to cylindrical nano-channels of polymer electrolyte membranes such as Nafion and addresses the validity of continuum models for these materials.

Effect of Slip Velocity on the Rotating Electro-Osmotic Flow of the Power-Law Fluid in a Slowly Varying Microchannel

2018 ◽  
Vol 73 (9) ◽  
pp. 825-831 ◽  
Author(s):  
Shaowei Wang ◽  
Ning Li ◽  
Moli Zhao ◽  
Martin N. Azese
Keyword(s):  
Power Law ◽  
Slip Velocity ◽  
Slip Parameter ◽  
Power Law Fluid ◽  
Osmotic Flow ◽  
Fluid Behavior ◽  
Poisson Boltzmann ◽  
Poisson Boltzmann Equation ◽  
Electro Osmotic Flow ◽  
Behavior Index

AbstractIn this paper, the effect of slip velocity on the rotating electro-osmotic flow (EOF) of the power-law fluid in a non-uniform microchannel under high zeta potential is investigated. The potential distribution of the electric double layer is obtained by using the nonlinear Poisson-Boltzmann equation. By using the finite difference method, the numerical solution of the rotating EOF velocity profile is obtained. The effectiveness and correctness of the present numerical method is proven by comparing the results with the analytical solutions of the Newtonian fluid given by a previous study. The influences of the fluid behavior indexnand the slip parameterβon the velocity profiles are also discussed in detail.

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