Electrical conductance of charged nanopores
Abstract
A nanopores's response to an electrical potential drop is characterized by its electrical conductance, G. It has long been thought that at low concentrations, the conductance is independent of the electrolyte concentration, c0, such that G ~ c00. It has been recently demonstrated that surface charge regulation changes the dependency to be G ~ c0α where the slope typically takes the values α = 1/3 or 1/2. Yet, experiments have observed slopes of 2/3 and 1 suggesting that additional mechanisms, such as convection and slip-lengths, appear. We show that the inclusion of convection doesn't vary the slope, while the inclusion of a slip length doubles the slope value. Here, we elucidate the interplay between surface charge regulation, convection, and slip-lengths. We show that when all effects are accounted for α can take any value between 0 and 1. This result is of utmost importance in designing any electro-kinetically driven nanofluidic system characterized by its conductance.