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Fine-tuning the Size and Minimizing the Noise of Solid-state Nanopores
Published on: October 31, 2013
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Ion current rectification, limiting and overlimiting conductances in nanopores
Liesbeth van Oeffelen1, Willem Van Roy2, Hosni Idrissi3
1Research group of Microbiology, Vrije Universiteit Brussel, Brussels, Belgium; IMEC, Leuven, Belgium.
Plos One
|May 16, 2015
Summary
Steady state is rarely achieved in solid-state nanopore simulations due to ion co-diffusion. Ion concentration polarization explains limiting conductances and rectification, providing an intuitive model for nanopore behavior.
Area of Science:
- Computational physics
- Nanotechnology
- Electrochemistry
Background:
- Previous Poisson-Nernst-Planck (PNP) simulations of solid-state nanopores used simplified boundary conditions.
- Focus was on steady-state behavior, limiting practical and simulation accuracy.
Purpose of the Study:
- To perform time-dependent and steady-state PNP simulations with less restrictive boundary conditions.
- To investigate ion currents in various nanopore geometries and surface charge configurations.
- To elucidate the mechanisms behind limiting conductances and ion current rectification.
Main Methods:
- Time-dependent and steady-state Poisson-Nernst-Planck (PNP) simulations.
- Simulation of ion currents through cylindrical and conical nanopores.
- Analysis of spatial and temporal current dependence for individual ion species.
- Comparison of simulation results with experimental measurements of silicon nitride nanopores.
Main Results:
- Steady state is generally not reached due to slow co-diffusion of oppositely charged ions.
- Ion concentration polarization is identified as the cause of limiting conductances and rectification.
- Simulations accurately reproduced experimentally observed current-voltage characteristics and overlimiting conductances.
- Overlimiting conductances arise from enhanced electric double-layer conductance due to voltage-induced polarization charges.
Conclusions:
- A more intuitive model for ion current rectification in solid-state nanopores is established.
- Slow ion co-diffusion prevents reaching steady state in many nanopore simulations and experiments.
- Voltage-induced polarization charges significantly influence nanopore conductance, particularly in rectifying systems.
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