Molecular streaming and its voltage control in ångström-scale channels

Area of Science:

• Physics
• Materials Science
• Nanotechnology

Background:

• Nanoscale fluidic devices reveal unique water and ion transport phenomena.
• Two-dimensional materials enable artificial channels with ångström-scale precision, challenging continuum transport models.
• Molecular confinement alters water properties and ionic motion due to wall interactions.

Purpose of the Study:

• To investigate the coupled transport of water and ions in molecular-sized slit-like channels.
• To explore the electrohydrodynamic effects on ionic fluid transport under confinement.
• To understand material-dependent differences in transport phenomena.

Main Methods:

• Measurements of ionic fluid transport driven by pressure and electric fields.
• Utilizing molecular-sized slit-like channels made of graphite and hexagonal boron nitride.
• Applying a modified continuum framework to analyze frictional interactions.

Main Results:

• A transistor-like electrohydrodynamic effect was observed, significantly increasing pressure-driven ionic transport (up to 20x) with a small applied bias.
• This gating effect was present in both graphite and hexagonal boron nitride channels, but with distinct material-dependent variations.
• The study quantified streaming mobilities under varying electrical conditions.

Conclusions:

• Molecular-scale confinement enables a highly nonlinear gating of fluid transport.
• The observed electrohydrodynamic effect offers new strategies for controlling molecular and ion transport.
• Findings may elucidate electromechanical couplings in biological systems like mechanosensitive channels.