Electroosmotic Flow Behavior of Viscoelastic LPTT Fluid in a Microchannel.

Dilin Chen,Haiwen Chen,Lai Zhang,Jie Li,Hongna Zhang,Yu Ma

doi:10.3390/mi10120881

Abstract

In many research works, the fluid medium in electroosmosis is considered to be a Newtonian fluid, while the polymer solutions and biological fluids used in biomedical fields mostly belong to the non-Newtonian category. Based on the finite volume method (FVM), the electroosmotic flow (EOF) of viscoelastic fluids in near-neutral (pH = 7.5) solution considering four ions (K+, Cl−, H+, OH−) is numerically studied, as well as the viscoelastic fluids’ flow characteristics in a microchannel described by the Linear Phan-Thien–Tanner (LPTT) constitutive model under different conditions, including the electrical double layer (EDL) thickness, the Weissenberg number (Wi), the viscosity ratio and the polymer extensibility parameters. When the EDL does not overlap, the velocity profiles for both Newtonian and viscoelastic fluids are plug-like and increase sharply near the charged wall. Compared with Newtonian fluid at Wi = 3, the viscoelastic fluid velocity increases by 5 times and 9 times, respectively, under the EDL conditions of kH = 15 and kH = 250, indicating the shear thinning behavior of LPTT fluid. Shear stress obviously depends on the viscosity ratio and different Wi number conditions. The EOF is also enhanced by the increase (decrease) in polymer extensibility parameters (viscosity ratio). When the extensibility parameters are large, the contribution to velocity is gradually weakened.

Highlights

In recent years, with the development of multi-disciplines and mutual integration, microfluidic chips have become more widespread
Broad application prospects can be foreseen in the Point-of-Care Testing (PoCT) of seafarers’ diseases [1,2] and the desalination [3,4] of automatic signal transmission
When direct current (DC) or alternating current (AC) voltage is applied along the horizontal direction of the microchannel, the direction of the external electric field is tangent to the charged surface, and the liquid ions in the electrical double layer (EDL) will be directionally displaced by the electric field force, driving the fluid microclusters to move along the direction of the electric field force to form electroosmotic flow (EOF)

Summary

Introduction

With the development of multi-disciplines and mutual integration, microfluidic chips have become more widespread. Microfluidic chips have many applications in the sensing and detection of nanoparticles [5,6,7], operations and reactions in analytical chemistry [8,9], encryption and decryption of information, future military communication, etc. Helmholtz [11] considered the liquid and electric flow phenomena comprehensively for the first time, connecting the electric phenomenon, fluid flow and ion concentration, and proposing a complete electrical double layer (EDL) model theory. When direct current (DC) or alternating current (AC) voltage is applied along the horizontal direction of the microchannel, the direction of the external electric field is tangent to the charged surface, and the liquid ions in the EDL will be directionally displaced by the electric field force, driving the fluid microclusters to move along the direction of the electric field force to form EOF

Methods

Results

Conclusion