Wetting Driven by Thermal Fluctuations on Terraced Nanostructures

Area of Science:

• Physics, Physical Chemistry, and Materials Science
• Nanotechnology and Microfluidics

Background:

• Understanding liquid behavior in confined micro- and nanoscale environments is crucial for various applications.
• Capillary forces and wetting phenomena traditionally dictate fluid dynamics in such systems.

Purpose of the Study:

• To reveal a novel mechanism for fluid displacement in nanoscale channels driven by thermal fluctuations.
• To investigate the role of surface nanostructures in controlling immiscible liquid movement.
• To develop analytical models for predicting fluid displacement rates.

Main Methods:

• Theoretical analysis and fully atomistic molecular dynamics simulations were employed.
• A Brownian ratchet mechanism was identified as the driving force for liquid displacement.
• The Smoluchowski diffusion equation was analytically solved to predict mean displacement rates.

Main Results:

• A Brownian ratchet mechanism was demonstrated to drive net displacement of immiscible liquids.
• Thermally driven displacement can overcome conventional wetting and capillary forces.
• Analytical expressions for mean displacement rates were derived from simulation data.

Conclusions:

• Surface nanostructures with directional asymmetry can induce thermally driven liquid displacement.
• The findings provide a physical basis for engineering surfaces to control microfluidic and wetting processes.
• The developed analytical framework can guide the design of systems for capillary filling, wicking, and imbibition.