Propagating concentration polarization and ionic current rectification in a nanochannel-nanofunnel device

Area of Science:

• Nanofluidics
• Computational physics
• Electrochemistry

Background:

• Ionic current rectification is crucial for nanofluidic devices.
• Understanding ion transport in confined geometries is essential.
• Concentration polarization (CP) significantly influences ion flow.

Purpose of the Study:

• To investigate ionic current rectification in a nanofluidic device with a nanofunnel and adjacent nanochannels.
• To analyze the behavior and propagation of concentration polarization (CP) zones.
• To explore the impact of CP zones on ionic current rectification.

Main Methods:

• Simulating ion transport using coupled 3D Nernst-Planck, Poisson, and Navier-Stokes equations.
• Modeling a nanofluidic device comprising a nanofunnel between two nanochannels.
• Analyzing charge-selective properties and CP zone formation and propagation.

Main Results:

• The funnel tip exhibits charge-selective properties, creating enriched and depleted CP zones.
• CP zones can propagate into adjacent nanochannels, influenced by electroosmotic flow.
• High-conductance states show increased ionic concentrations in the cathodic nanochannel; low-conductance states localize depleted CP zones.

Conclusions:

• The study provides insights into ionic current rectification mechanisms in complex nanofluidic geometries.
• The findings highlight the role of CP zone propagation in device performance.
• The developed 3D modeling scheme is efficient for designing advanced nanofluidic devices.