The pressure-driven flow of ionic liquid through an asymmetrically charged rectangular microchannel has been investigated numerically using the finite element method. The mathematical model equations such as the Poisson and Navier-Stokes in conjunction with Nernst-Planck equations have been solved to obtain the electrical potential, charge, pressure, and induced electric fields for the following dimensionless conditions: inverse Debye length K = 2, top wall charge density ST = 8, charge density ratio (Sr = SB/ST) as 0 – 2 and Reynolds and Schmidt numbers (Re = 0.01, Sc = 1000). The current results have been compared with the literature for the limiting conditions and found to have good agreement with them. It is found that the asymmetry of the surface charge at the two walls of the microfluidic device plays a significant role in the development of flow fields. The higher asymmetry of surface charge increases the electroviscous effects in microfluidic device flow. The electroviscous correction factor (Y=ΔP/ΔP0) increases by 17% for Sr in the range of 0 to 2 at fixed K. The present results provide useful guidelines which may help in the design and engineering of the microfluidic devices.

Pressure driven flow of ionic liquid through asymmetrically charged contraction-expansion microfluidic device

ACS Spring 2022

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