Advanced Methods for Ion Selectivity Measurement in Nanofluidic Devices

Abstract

Nanofluidic devices with specific ion selectivity have shown great potential in efficient ion separation, biosensing, and energy conversion technologies. Advances in analytical techniques have enabled quantitative measurement of the nanofluidics’ ion selectivity and understanding of the ion selection mechanisms. This review gives a brief overview of recent progress in the fabrication of single-channel and multichannel nanofluidic devices with specific ion selection functionalities based on nanopores, nanochannels, nanotubes, nanopipettes, and nanoslits. Then advanced experimental methods (i.e., drift-diffusion experiments, charged molecular diffusion experiments, ion permeation experiments, electrodialysis, ion current/conductance/conductivity measurements, and pyranine assays) and theories (i.e., Goldman–Hodgkin–Katz model and ion selectivity calculation equations) for investigating cation/anion, mono/divalent-ion, and single-ion selectivities in nanofluidic devices are summarized. Finally, the challenges that need to be addressed in this research field and the perspective of sub-nanofluidic devices are discussed.