Transport properties of anti-symmetrically charged nanochannels in symmetrical electrolyte solutions

While numerous studies have explored ion and solvent transport in nanochannels with longitudinal inhomogeneity of surface charge, none has considered the effects of an alternative kind of inhomogeneity, namely, oppositely charged nanochannel walls. This study for the first time explores such system theoretically and shows its transport properties to be qualitatively different from nanochannels with identical walls. In particular, anti-symmetrically charged nanochannels feature negative osmosis, enhanced salt-diffusion permeability, and practically no ion perm-selectivity. On the contrary, “conventional” nanochannels typically exhibit positive osmosis and reduced salt-diffusion permeability. The practical lack of ion-perm-selectivity in anti-symmetrically charged nanochannels can make them useful for electrically driven micro-/nanofluidics due to negligible current-induced concentration polarization of micro-/nano-interfaces.