Quantification of bulk solution limits for liquid and interfacial transport in nanoconfinements

Area of Science:

• Physical Chemistry
• Nanotechnology
• Fluid Dynamics

Background:

• Liquid imbibition is key to understanding nanoscale transport.
• Deviations from the Washburn equation are common in nano-scale imbibition.
• The origins of these deviations are debated among researchers.

Purpose of the Study:

• To present an experimental method for measuring nanoscale transport variables.
• To determine independent effective values for capillary pressure, liquid viscosity, and interfacial gas partitioning.
• To investigate fluid transport in two-dimensional nanochannels.

Main Methods:

• Utilized reflected differential interference contrast microscopy for tracer-free imaging.
• Employed a novel image and data analysis scheme.
• Conducted experiments in siliceous nanochannels as small as 30 nm × 60 nm.

Main Results:

• Observed significant departures from bulk transport values for isopropanol in nanochannels.
• Measured reduced capillary pressures and increased liquid viscosity.
• Identified nucleation of structured, quasi-crystalline boundary layers (10-25 nm).

Conclusions:

• Structured boundary layers significantly impact nanoscale fluid transport.
• These layers are thicker than predicted by intermolecular forces alone.
• Understanding nanoconfinement effects is crucial for nanoporous media applications.