Ion Size and Ion Partitioning Effects on Electroosmosis Flow of Power-Law Fluids in pH-Responsive Soft Nanochannels with Basic Functional Groups

Abstract

This study numerically investigates the electroosmotic flow (EOF) of power-law fluids in soft nanochannels whose inner walls are coated with pH-sensitive polyelectrolyte layers (PELs) containing basic functional groups. We focused on the combined effects of ion size and ion partitioning on the fully developed EOF within these channels. Our model uses modified Poisson−Boltzmann and Cauchy momentum equations to describe the electrostatic potential and flow velocity, which we solved numerically using the finite difference method. The results highlight the significant influence of ion size and ion partitioning (due to permittivity differences between the PEL and electrolyte) on both the electrostatic potential and the flow velocity, along with the role of other key parameters. We also emphasize the importance of the basic functional group present throughout the PEL on the selectivity of mobile electrolyte ions.