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Abnormal Ionic-Current Rectification Caused by Reversed Electroosmotic Flow under Viscosity Gradients across Thin
Yinghua Qiu1, Zuzanna S Siwy2, Meni Wanunu1
1Department of Physics , Northeastern University , Boston , Massachusetts 02115 , United States.
Analytical Chemistry
|December 6, 2018
Summary
Ionic and fluidic transport in nanopores under viscosity gradients were studied. Reversed electroosmotic flow in nanopores filled with low-viscosity solutions affected current rectification, which could be tuned by surface charge density.
Area of Science:
- Nanofluidics
- Physical Chemistry
- Electrokinetics
Background:
- Single nanopores are crucial for various applications.
- Most studies use uniform electrolytes, unlike natural systems with solution gradients.
- Understanding transport under viscosity gradients is essential.
Purpose of the Study:
- Investigate ionic and fluidic transport through nanopores under viscosity gradients.
- Analyze the impact of viscosity gradients on ionic-current rectification.
- Explore the role of electroosmotic flow in these phenomena.
Main Methods:
- Experimental measurements of ionic current and fluid flow.
- Computational simulations of transport phenomena.
- Systematic variation of viscosity and surface charge density.
Main Results:
- Observed ionic-current rectification due to differing pore filling under bias.
- Noted abnormal reduction in current rectification with high-viscosity solutions.
- Identified reversed electroosmotic flow as the cause, linked to ion depletion dynamics.
- Demonstrated that increased surface charge density enhances current rectification.
Conclusions:
- Viscosity gradients significantly influence ion and fluid transport in nanopores.
- Electroosmotic flow dynamics, driven by ion depletion, dictate rectification behavior.
- Surface charge engineering offers a method to control rectification ratios in nanoporous systems.
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