Voltage-Rectified Current and Fluid Flow in Conical Nanopores

Area of Science:

• Nanoscale science and engineering
• Physical chemistry
• Materials science

Background:

• Ion current rectification (ICR) mimics solid-state diodes due to asymmetric ion transport in nanopores.
• ICR arises from asymmetric electrical double layers, leading to ion accumulation/depletion.
• Recent research links ICR to nanoscale flow phenomena with potential applications.

Purpose of the Study:

• To review recent investigations on voltage-dependent ion distributions and ICR in conical nanopores.
• To explore how ICR and coupled electroosmotic flow (EOF) induce novel nanoscale flow phenomena.
• To highlight applications in energy storage, chemical sensing, and fluid pumping.

Main Methods:

• Experiments using conical nanopores (10-300 nm tip opening) in glass, mica, and polymer membranes.
• Investigating fluid flow induced by external pressure and electroosmotic forces.
• Analyzing electrical properties and their interplay with fluid dynamics.

Main Results:

• Pressure-driven flow significantly alters nanopore electrical properties, and vice versa.
• ICR is coupled with EOF rectification, enabling electrically controlled fluid pumping.
• Combination of pressure and EOF generates negative differential resistance (NDR) and bistability.

Conclusions:

• Nanopore ionics and fluid dynamics are intricately linked, enabling new functionalities.
• EOF rectification offers precise electrical fluid pumping capabilities.
• Nanopore-based NDR exhibits sensitivity to surface charge, suggesting chemical sensing applications.