Journal Article

Induced mixing electrokinetics in a charged corrugated nano-channel: towards a controlled ionic transport

Banerjee, A, Haque, A, Nayak, A K, Weigand, B

2018

Overview

To perform a fluid analysis for electroosmotic flows in micro- and nano-channels, it is necessary to mix various fluid contents in micro- and nano-scales. It is observed that fluids in electroosmotic flow exhibits Reynolds number effect as the flow exerts very weak inertial force and it requires long channel for mixing of different layers and species through diffusion process. Hence, if the desired length scale of mixing is large, an enormous time is needed for the molecules to be thoroughly mixed by diffusion. The theory of dynamic equations on time scale is used to study the stability of these systems. It is found that such a system may exhibits an unstable nature for overlapping electric double layer field with fluctuating velocities and stability is preserved for zero linear growth coefficient. To obtain an improved understanding of mixing performance, a numerical study is performed with the variation of channel height when more than one ionic species with channels patterned with heterogeneity is considered. The wall heterogeneity may be created by placing some blocks of unequal size (with or without charged) close to the channel wall or some external potential patches. The analytical results for the transport characteristics of electroosmotic flow obtained are compared with the direct numerical simulation of the Navier–Stokes equation, Nernst–Plank equation, and Poisson equation, simultaneously. It is shown that heterogeneous potential could generate complex flow structures and the increment of species layers at different levels of the channel cross section from inlet to outlet significantly improve the mixing rate.

• Publisher: Springer Nature B.V
• Subject: Approximation / Channels / Computational fluid dynamics / Computer simulation / Diffusion / Diffusion layers / Direct numerical simulation / Dye dispersion / Dynamic stability / Electric double layer / Electric fields / Electrokinetics / Electroosmosis / Flow structures / Flow velocity / Fluid flow / Fluids / Heterogeneity / Inlets (waterways) / Mathematical analysis / Mathematical models / Nanochannels / Navier-Stokes equations / Poisson equation / Reynolds number / Species / Species diffusion / Transport