Effect of Nanochannel Diameter and Debye Length on Ion Current Rectification in a Fluidic Bipolar Diode

Abstract

We have simulated ion current rectification (ICR) in a bipolar nanochannel fluidic diode for different nanochannel diameters, electrolyte concentrations, and surface charge densities. The ICR decreases with diameter of the fluidic nanochannel due to decrease in unipolar character of the electrolyte. The ICR decreases with electrolyte concentration due to surface charge screening by counterions. The ICR increases with channel diameter for a given ratio of channel diameter to Debye length. Scaling of forward and reverse current densities with electrolyte concentration has been determined using curve fitting for different values of surface charge densities and channel diameters. The ICR can be increased by increasing surface charge density to enhance unipolar character of the electrolyte. The fluid velocity close to the nanochannel walls is driven by body force and along the center by the fluid pressure, which gives rise to a curly fluid flow.