Efficient electrokinetic non-Newtonian flow mixing in a patterned micro-tube

This paper presents a numerical investigation of the micro-mixing behavior of a non-Newtonian fluid passing through a micro-tube with periodic zeta potential and sinusoidal wall roughness. A finite volume approach is utilized to numerically predict the flow field of two miscible aqueous electrolytes, which are described by a power-law model. To explore the pressure drop and mixing efficiency for a wide range of wave amplitude (δ), the Debye-H ü ckel parameter (κa), and the flow behavior index (n), simulations based on the Poisson-Nernst-Planck model are conducted. The presence of a sinusoidal charged surface is expected to increase the interfacial contact area between the two streams. With an increase in wall corrugation, the Debye length (λ), and the flow behavior index, a significant improvement in mixing efficiency is expected. Simulation results predict that the value of mixing efficiency rises up to 95% for δ=0.5, κa=10, and n=1.6. Moreover, for a thinner EDL, the mixing efficiency is predicted to reduce by 31% for a change in κa from 10 to 40 with n=1.5 and δ=0.5. It is also stated that increasing n, κa, and δ can result in a larger pressure drop in addition to forecasting a higher mixing. In order to create an effective and efficient micro-mixer that can forecast the highest possible mixing efficiency with a moderate pressure drop, a parametric study is conducted to predict and analyze the mixing performance factor, the ratio of mixing efficiency, and the average pressure drop. The findings of the current study could be useful for the thorough design and analysis of a passive micro-mixer, which would enable the effective transport of polymeric and bio-fluids inside micro-devices.