Analysis of Electro-Osmotic Flow Characteristics at Joint of Capillaries with Step Change in ζ -Potential and Dimension

2005 ◽  
Vol 7 (2) ◽  
pp. 131-135 ◽  
Author(s):  
Wang Ruijin ◽  
Lin Jianzhong ◽  
Li Zhihua
Keyword(s):  
Flow Characteristics ◽  
Step Change ◽  
Ζ Potential ◽  
Osmotic Flow ◽  
Electro Osmotic Flow

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.

Dispersion in Electro-Osmotic Flow Through a Slit Channel With Axial Step Changes of Zeta Potential

2013 ◽  
Vol 135 (10) ◽  
Author(s):  
Chiu-On Ng ◽  
Bo Chen
Keyword(s):  
Dispersion Coefficient ◽  
Hydrodynamic Dispersion ◽  
Plate Height ◽  
Cross Sectional ◽  
Ζ Potential ◽  
Osmotic Flow ◽  
Long Wave ◽  
Cross Sectional Dimension ◽  
Limiting Case ◽  
Electro Osmotic Flow

An analytical study is presented in this paper on hydrodynamic dispersion due to steady electro-osmotic flow (EOF) in a slit microchannel with longitudinal step changes of ζ potential. The channel wall is periodically patterned with alternating stripes of distinct ζ potentials. Existing studies in the literature have considered dispersion in EOF with axial nonuniformity of ζ potential only in the limiting case where the length scale for longitudinal variation is much longer than the cross-sectional dimension of the channel. Hence, the existing theories on EOF dispersion subject to nonuniform charge distributions are all based on the lubrication approximation, by which cross-sectional mixing is ignored. In the present study, the general case where the length of one periodic unit of wall pattern (which involves a step change of ζ potential) is comparable with the channel height, as well as the long-wave limiting case, are investigated. The problem for the hydrodynamic dispersion coefficient is solved numerically in the general case, and analytically in the long-wave lubrication limit. The dispersion coefficient and the plate height are found to have strong, or even nonmonotonic, dependence on the controlling parameters, including the period length of the wall pattern, the area fraction of the EOF-suppressing region, the Debye parameter, the Péclet number, and the ratio of the two ζ potentials.

Exact Solution of AC Electro-Osmotic Flow in a Microannulus

2013 ◽  
Vol 135 (9) ◽  
Author(s):  
Ali Jabari Moghadam
Keyword(s):  
Exact Solution ◽  
Double Layer ◽  
Electric Double Layer ◽  
Maximum Velocity ◽  
Velocity Profiles ◽  
Radius Ratio ◽  
Dimensionless Frequency ◽  
Ζ Potential ◽  
Osmotic Flow ◽  
Electro Osmotic Flow

The time-periodic electro-osmotic flow in a microannulus is investigated based on the linearized Poisson–Boltzmann equation. An exact solution of the velocity distribution is obtained by using the Green's function approach. The influences of the geometric radius ratio, the wall ζ potential ratio, the electrokinetic radius, and the dimensionless frequency on velocity profiles are presented. Variations of the geometric radius ratio (between zero and one) can lead to quite different flow behaviors. The wall ζ potential ratio affects the magnitude and direction of the velocity profiles within the electric double layer near the two walls of a microannulus. Depending on the frequency and the geometric radius ratio, the walls identically and/or oppositely charged, both may result in the two-opposite-direction flow in the annulus. For high frequency, the electro-osmotic velocity variations are restricted mainly within a thin layer near the two cylindrical walls. Increasing the electrokinetic radius leads to decrease the electric double layer thickness as well as the maximum velocity near the walls.

Enhanced Electro-Osmotic Flow of Power-Law Fluids in Hydrophilic Patterned Nanochannel

2020 ◽  
Vol 142 (10) ◽  
Author(s):  
M. Majhi ◽  
A. K. Nayak ◽  
A. Banerjee
Keyword(s):  
Power Law ◽  
Enhancement Factor ◽  
Random Phase ◽  
Flow Characteristics ◽  
Navier Stokes ◽  
Physical Parameters ◽  
Osmotic Flow ◽  
Power Law Fluids ◽  
Dilatant Fluid ◽  
Electro Osmotic Flow

Abstract In this paper, electro-osmotic flow (EOF) enhancement of non-Newtonian power-law fluids in a modulated nanochannel with polarized wall is proposed. The channel walls are embedded with periodically arranged rectangular grooves, placed vertically with the direction of electric field. The key aspect of the present study is to achieve enhanced EOF of power-law fluids due to periodic groove patterns. The flow characteristics are studied through Poisson–Nernst–Plank-based Navier–Stokes model associated with electrochemical boundary conditions. Some random-phase differences between the grooves in both the walls are allowed to find the best configuration for the EOF enhancement in case of both Pseudo-plastic fluid, Dilatant fluid, and compared to Newtonian fluid. A notable enhancement factor is observed when groove width is much larger than its depth along with overlapped EDL. It is also found that EOF enhancement for shear-thinning fluid is quite better than the other fluids, for the same set of physical parameters. A comparison of enhancement factor for power-law fluid is also presented when the grooves are replaced with hydrophobic strips. It is worth to mention here that the present study assumes no-slip condition which is true for wetting (hydrophilic) surface over nonwetting (hydrophobic) strips which is common occurrence in regards to nanoconfinements.

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.

Modeling electro-osmotic flow and thermal transport of Caputo fractional Burgers fluid through a micro-channel

2021 ◽  
pp. 095440892110259
Author(s):  
Mohammed Abdulhameed ◽  
Garba Tahiru Adamu ◽  
Gulibur Yakubu Dauda
Keyword(s):  
Electric Field ◽  
Laplace Transform ◽  
Inverse Laplace Transform ◽  
Micro Channel ◽  
Osmotic Flow ◽  
Sine Transform ◽  
Fourier Sine ◽  
Fourier Sine Transform ◽  
Burgers Fluid ◽  
Electro Osmotic Flow

In this paper, we construct transient electro-osmotic flow of Burgers’ fluid with Caputo fractional derivative in a micro-channel, where the Poisson–Boltzmann equation described the potential electric field applied along the length of the microchannel. The analytical solution for the component of the velocity profile was obtained, first by applying the Laplace transform combined with the classical method of partial differential equations and, second by applying Laplace transform combined with the finite Fourier sine transform. The exact solution for the component of the temperature was obtained by applying Laplace transform and finite Fourier sine transform. Further, due to the complexity of the derived models of the governing equations for both velocity and temperature, the inverse Laplace transform was obtained with the aid of numerical inversion formula based on Stehfest's algorithms with the help of MATHCAD software. The graphical representations showing the effects of the time, retardation time, electro-kinetic width, and fractional parameters on the velocity of the fluid flow and the effects of time and fractional parameters on the temperature distribution in the micro-channel were presented and analyzed. The results show that the applied electric field, electro-osmotic force, electro-kinetic width, and relaxation time play a vital role on the velocity distribution in the micro-channel. The fractional parameters can be used to regulate both the velocity and temperature in the micro-channel. The study could be used in the design of various biomedical lab-on-chip devices, which could be useful for biomedical diagnosis and analysis.

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