Electroosmotic Flow of Non-Newtonian Fluid in Porous Polymer Membrane at High Zeta Potentials.

Shuyan Deng,Mingying Li,Yukun Zeng,Cuixiang Liang

doi:10.3390/mi11121046

Shuyan Deng, Mingying Li + Show 2 more

Open Access

https://doi.org/10.3390/mi11121046

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Abstract

To help in the efficient design of fluid flow in electroosmotic pumps, electroosmotic flow of non-Newtonian fluid through porous polymer membrane at high zeta potentials is studied by mainly evaluating the total flow rate at different physical parameters. Non-Newtonian fluid is represented by the power-law model and the porous polymer membrane is considered as arrays of straight cylindrical pores. The electroosmotic flow of non-Newtonian fluid through a single pore is studied by solving the complete Poisson–Boltzmann equation and the modified Cauchy momentum equation. Then assuming the pore size distribution on porous polymer membrane obeys Gaussian distribution, the performance of electroosmotic pump operating non-Newtonian fluid is evaluated by computing the total flow rate of electroosmotic flow through porous polymer membrane as a function of flow behavior index, geometric parameters of porous membrane, electrolyte concentration, applied voltage, and zeta potential. It is found that enhancing zeta potential and bulk concentration rather than the applied voltage can also significantly improve the total flow rate in porous polymer membrane, especially in the case of shear thinning fluid.

Highlights

Microfluidic technologies have attracted increasing attention recently due to the broad applications in numerous fields such as microelectric mechanic systems, bio-sensor systems, and on-chip experimental systems [1,2,3]
The novelty of this paper is to study electroosmotic flow (EOF) of power-law fluids through porous polymer membrane at high zeta potentials in the context of Electroosmotic pump (EO pump) applications
The total flow rate of EOF through porous polymer membrane is increased for shear thinning fluids (n < 1) and it gets more evident as the flow behavior

Summary

Introduction

Microfluidic technologies have attracted increasing attention recently due to the broad applications in numerous fields such as microelectric mechanic systems, bio-sensor systems, and on-chip experimental systems [1,2,3]. The novelty of this paper is to study EOF of power-law fluids through porous polymer membrane at high zeta potentials in the context of EO pump applications. With the assumption that the porous membrane has a Gaussian distribution of parallel cylindrical pores (such as the porous glass [11,12,14], porous polymer membrane [15,16,17]), the total flow rate through porous track-etch polymer membrane is computed as a function of flow behavior index, zeta potential, electric voltage, and concentration of solution. Using Assumptions (1), (5) and (6), for a single direction EOF in each single pore of porous polymer membrane, the velocity is reduced to the component along the axial direction u(r) and the corresponding constitutive equation of power-law fluid can be written as τ = m(−du/dr)n−1·(du/dr). After computing velocity profile u(r), the flow rate and average velocity for EOF of power-law fluids in a single pore is solved from the following expressions

Mathematical Model for EOF of Power-Law Fluid through Porous Polymer Membrane

Results and Discussion

EOF of Power-Law Fluid in a Single Pore

Effect of the Applied Electric Voltage

Effect of the Geometric Properties of the Membrane

Conclusions