Asymmetric-Fluidic-Reservoirs Induced High Rectification Nanofluidic Diode

Area of Science:

• Nanotechnology
• Electrochemistry
• Fluid Dynamics

Background:

• Nanofluidic diodes are crucial for controlling ion flow.
• Existing devices often struggle with low rectification ratios and complex fabrication.
• Asymmetry in pore geometry or surface charge is typically required for rectification.

Purpose of the Study:

• To demonstrate a novel nanofluidic diode with exceptionally high current rectification.
• To investigate the mechanism of rectification based on reservoir size asymmetry.
• To present a scalable and industrially viable nanofluidic diode design.

Main Methods:

• Fabrication of ion permselective nanopores using plasma oxidation.
• Connecting nanopores between reservoirs of differing diameters (micropore and macropore).
• Applying varying voltages (+100 V and -100 V) to induce ion depletion and enrichment zones.

Main Results:

• Achieved rectification factors exceeding 3500, nearly two orders of magnitude higher than previous reports.
• Observed distinct ion-depleted and ion-enriched zones under applied voltage, driven by reservoir asymmetry.
• Demonstrated that asymmetry in connected reservoirs, not the nanopore itself, is key to high rectification.

Conclusions:

• The developed nanofluidic diode offers unprecedented rectification efficiency.
• The design leverages simple reservoir asymmetry for high performance, simplifying fabrication.
• This technology shows significant potential for industrial-scale applications in ionic devices.