Pressure-dependent ion current rectification in conical-shaped glass nanopores

Area of Science:

• Electrochemistry
• Nanofluidics
• Physical Chemistry

Background:

• Ion current rectification in nanopores is crucial for applications like sensing and filtration.
• Understanding factors influencing rectification, such as pore geometry and solution conditions, is essential.
• Previous studies have explored various parameters, but the impact of pressure-driven flow on rectification in conical nanopores requires further investigation.

Purpose of the Study:

• To investigate the influence of pressure-driven electrolyte flow on ion current rectification in conical glass nanopores.
• To determine the relationship between flow rate, nanopore dimensions, and the degree of rectification.
• To compare experimental findings with theoretical predictions from numerical simulations.

Main Methods:

• Fabrication of conical glass nanopores with varying orifice radii (e.g., ~30 nm and ~200 nm).
• Experimental measurements of ion current-voltage (i-V) characteristics under varying applied pressures.
• Finite-element simulations solving Nernst-Planck, Poisson, and Navier-Stokes equations for ion transport in a moving electrolyte.

Main Results:

• Ion current rectification in conical nanopores is dependent on the rate of pressure-driven electrolyte flow, decreasing as flow rate increases.
• The disruption of equilibrium cation and anion distributions within the nanopore by flow is responsible for the observed pressure dependence.
• Pressure-driven flow significantly reduces rectification in larger nanopores (~200 nm) but has a minimal effect on smaller ones (~30 nm).

Conclusions:

• Pressure-driven electrolyte flow is a critical factor modulating ion current rectification in conical nanopores.
• The effect of flow on rectification is strongly dependent on nanopore geometry, particularly the orifice radius.
• Experimental results align with finite-element simulations, validating the model for predicting ion transport phenomena in nanopores under flow.