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Electromigration current rectification in a cylindrical nanopore due to asymmetric concentration polarization
Jung-Yeul Jung1, Punarvasu Joshi, Leo Petrossian
1Departments of Mechanical and Aerospace Engineering, Arizona State University, Tempe, Arizona 85287, USA.
Analytical Chemistry
|March 21, 2009
Summary
Electromigration through a nanopore shows current rectification due to electrical double layers. Ions redistribute after the electric field is off, causing measurable current.
Area of Science:
- Nanofluidics
- Electrokinetics
- Surface Chemistry
Background:
- Electrical double layers (EDLs) form at charged interfaces in electrolyte solutions.
- Concentration polarization near nanopores influences ion transport.
- Current rectification in nanopores is crucial for sensing and energy applications.
Purpose of the Study:
- To experimentally measure electromigration current in a single cylindrical nanopore.
- To investigate the effect of electrical double layer thickness on current rectification.
- To study ion redistribution after electric field removal.
Main Methods:
- Fabrication of a silicon chip with a single 175 nm nanopore in series with 2 and 100 micrometer micropores.
- Electromigration experiments to measure current through the nanopore under varying conditions.
- Analysis of current rectification and post-field ion redistribution.
Main Results:
- Thick EDLs (kappa a ≈ 1) exhibited significant current rectification attributed to asymmetric concentration polarization.
- Thinner EDLs showed nearly symmetric conductance.
- A measurable electrical current was observed after the electric field was turned off, resulting from ion redistribution.
Conclusions:
- Nanopore geometry and EDL thickness critically influence electromigration and current rectification.
- Concentration polarization dynamics are key to understanding rectification in confined geometries.
- The observed post-field current highlights the persistence of ion gradients and potential for energy harvesting or sensing applications.
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