Tuning Ion Transport through a Nanopore by Self-Oscillating Chemical Reactions.

Abstract

Ion transport in nanofluidic devices and biological ion channels are highly dependent on the local environmental conditions in the electrolyte solution. Many life processes in living systems are in dynamic electrolyte solutions, and many of them are self-oscillated. Tuning ion transport through a nanofluidic diode by the self-oscillating chemical reactions is demonstrated by modeling the electrokinetic ion transport process with a validated continuum model, which includes the time-dependent Poisson-Nernst-Planck equations for the ionic mass transport of multiple ionic species with both volumetric and surface chemical reactions, and Stokes equations for the flow field. A pH oscillator caused by oscillating chemical reactions (i.e., bromate-sulfite-ferrocyanide system) is added at the tip side of the nanopore to periodically change its surface charge properties, consequently tuning the ion selectivity and ion transport through the nanopore. Results show that both the surface charge density of the nanopore and the electrokinetic ion transport phenomena oscillate simultaneously with the pH oscillation generated by the self-oscillating chemical reactions. The numerical results obtained by our model qualitatively agree with the published experimental observations.