Electroosmotic Flow of Viscoelastic Fluid in a Nanoslit.

Lanju Mei,Hongna Zhang,Shizhi Qian,Hongxia Meng

doi:10.3390/mi9040155

Lanju Mei, Hongna Zhang + Show 2 more

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https://doi.org/10.3390/mi9040155

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Abstract

The electroosmotic flow (EOF) of viscoelastic fluid in a long nanoslit is numerically studied to investigate the rheological property effect of Linear Phan-Thien-Tanner (LPTT) fluid on the fully developed EOF. The non-linear Poisson-Nernst-Planck equations governing the electric potential and the ionic concentration distribution within the channel are adopted to take into account the effect of the electrical double layer (EDL), including the EDL overlap. When the EDL is not overlapped, the velocity profiles for both Newtonian and viscoelastic fluids are plug-like and increase sharply near the charged wall. The velocity profile resembles that of pressure-driven flow when the EDL is overlapped. Regardless of the EDL thickness, apparent increase of velocity is obtained for viscoelastic fluid of larger Weissenberg number compared to the Newtonian fluid, indicating the shear thinning behavior of the LPTT fluid. The effect of the Weissenberg number on the velocity distribution is less significant as the degree of EDL overlapping increases, due to the overall decrease of the shear rate. The increase (decrease) of polymer extensibility (viscosity ratio) also enhances the EOF of viscoelastic fluid.

Highlights

Over recent decades, nanofluidics has undergone significant development due to the advances in nanofabrication and its promising applications innanoparticle sensing and detection [1,2,3], manipulation of charged analytes [4,5], sequencing of single DNA molecules [6,7], etc
We numerically study the electroosmotic flow (EOF) of viscoelastic fluid with the PTT constitutive model in a nanoslit under different electrical double layer (EDL) conditions
The validated solver is applied to investigate the effects of Weissenberg number (Wi), the extensibility parameter ε, and the viscosity ratio β on the EOF of viscoelastic fluid in a long nanoslit with the consideration of EDL overlap

Summary

Introduction

Nanofluidics has undergone significant development due to the advances in nanofabrication and its promising applications in (bio)nanoparticle sensing and detection [1,2,3], manipulation of charged analytes [4,5], sequencing of single DNA molecules [6,7], etc. Das et al [25] derived the analytical solution of EOF of non-Newtonian fluid in a rectangular microchannel using the power-law model. Based on the earlier work, Afonso et al [33] investigated the EOF of viscoelastic fluid in a microchannel with asymmetric zeta potential, and Sousa et al [34] derived an analytical solution taking into account the wall depleted layer. Dhinakaran et al [35] extended the work of Afonso et al [31] and analytically analyzed the steady EOF of viscoelastic fluid in a microchannel with the PTT model by taking into account the full Gordon-Schowalter convective derivative

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