Ion conduction property of track- etched conical nanopores modified by atom layer deposition method under applied pressure

Abstract

In this work, single conical nanopores in Kapton films were fabricated using the etch-track and atomic layer deposition (ALD) methods. Nanopores with different tip sizes (34 nm, 123 nm, 194 nm, respectively) were used to investigate the effect of pressure on the ionic conduction rectification (ICR) of the nanopores. Results showed that the effect of pressure on the ICR of the nanopores is related to the tip size of the nanopore and the rectification coefficient of the nanopores in the electrolyte solution. When pressure was applied across the nanopore, a volumetric flow Q was engendered through the conical-shaped nanopore. Only when the tip size of the nanopore reached a certain size could the pressure-driven liquid flow eliminate the hydraulic resistance of the pore, changing the ion distribution in the nanopore and further altering the ICR of the nanopore. For nanopores with a tip size of 34 nm, the effect of pressure on ICR was almost negligible. Only when the tip size of the nanopore was greater than a certain extent did the applied pressure significantly affect the ICR. The influence of pressure on ICR was also related to the strength of the rectification coefficient of the nanopore in the electrolyte. Nanopores exhibiting smaller ion rectification coefficients were more susceptible to the effects of pressure on their ICR.