Electroneutrality breakdown in charged, nanofluidic channels

Charged, nanofluidic channels containing electrolyte solution are building blocks of many biological and technological systems. Due to their geometrical confinement and the dominance of surface forces, unique phenomena are observed such as slip flow enhancement. To understand these phenomena, it is necessary to (re)examine several fundamental physical mechanisms and associated assumptions. In particular, the assumption of complete screening of the fixed surface charges by counter-ions (i.e. electroneutrality) may not hold in a nanochannel. Recent work by Levy et al. (2020) provides evidence for electroneutrality breakdown in a single nanopore for zero-size ions, measured both locally in cross sections and globally for the entire channel. Our study goes beyond this initial investigation and employs the Poisson-Boltzmann equation to examine the electroneutrality in the presence of finite-size ions for a single nanopore as well as a periodic array of cylindrical nanopores. The effects of system dimensions, charge density on the channel surface, dielectric constants of system domains, and size of ions are explored. Additionally, an attempt is made to model the material surrounding the nanopore as a metal or a semiconductor so as to expand the technological applications of our model.