Osmotic flow through fully permeable nanochannels

Area of Science:

• Nanoscale science
• Physical chemistry
• Fluid dynamics

Background:

• Osmosis traditionally relies on semipermeable membranes.
• Understanding fluid transport in nanochannels is crucial for nanotechnology.

Purpose of the Study:

• To demonstrate and investigate osmotic flow in nonselective nanochannels.
• To quantify diffusio-osmotic transport driven by solute gradients.

Main Methods:

• Utilized a high-sensitivity fluorescence imaging technique.
• Measured water flow rates at the femtoliter per minute level in single nanochannels.

Main Results:

• Observed convective liquid motion from high to low electrolyte concentration due to salinity gradients.
• Demonstrated diffusio-osmotic transport under neutral polymer gradients, with flow in the opposite direction.
• Provided the first experimental evidence and quantitative analysis of this interfacial transport.

Conclusions:

• Diffusio-osmotic transport occurs in fully permeable nanochannels, driven by solute gradients.
• This phenomenon, influenced by interfacial effects and polymer entropic depletion, is critical for nanoscale dynamics.
• The findings necessitate a re-evaluation of transport mechanisms in confined systems.