Combined effects of interfacial permittivity variations and finite ionic sizes on streaming potentials in nanochannels

Abstract

In this work, we investigate the effects of local permittivity variations, induced by a preferential orientation and exclusion of water dipoles close to channel walls, and the effects of finite-sized ions on the induced streaming potential in nanochannels. We make a detailed analysis of the underlying physicochemical interactions by considering combinations of cases where ions are considered to be point sized/finite sized and permittivity variation effects to be present/absent. By accounting for the dielectric friction (which in turn is a function of the local permittivity) in addition to the classical Stokes friction, we show that for high interfacial potentials and narrow confinements, the induced streaming potential field for the cases in which the polarization effects are considered for finite-sized ions is remarkably higher than for the cases in which the polarization effects are neglected. Thus, by coupling the nonlinear effects of finite-sized ions and water dipole polarization along with the dielectric friction, we open a new paradigm of streaming potential predictions for narrow fluidic confinements, bearing far-ranging scientific and technological consequences in nanoscale science and technology.