Transport of electrolytes across nanochannels: The role of slip

We characterize the electrokinetic flow due to the transport of electrolytes embedded in nanochannels of varying cross section with inhomogeneous slip on their walls, modeled as an effective slip length on the channel wall. We show that, within linear response and Debye–Hückel regime, the transport coefficients, and so the fluxes, can be significantly improved by the presence of a hydrophobic surface coating located at the narrowest section of the nanochannel. Our model indicates that the enhancement is larger when considering electric conductive walls in comparison to dielectric microchannel walls, and it is produced by a synergy between the entropic effects due to the geometry and the presence of the slip boundary layer. Our results show that a tailored hydrophobic coating design can be an effective strategy to improve transport properties in the broad areas of lab-on-a-chip, biophysics, and blue energy harvesting and energy conversion technologies.