Wetting transition and fluid trapping in a microfluidic fracture

Area of Science:

• Physics
• Geophysics
• Fluid Dynamics

Background:

• Immiscible fluid displacement in confined geometries is crucial for geological CO2 sequestration and microfluidics.
• Fluid invasion dynamics are influenced by wetting transitions and surface interactions, especially at varying displacement rates.
• The effect of surface roughness on these processes in confined spaces remains poorly understood.

Purpose of the Study:

• To investigate the influence of surface roughness on immiscible fluid displacement and wetting transitions.
• To analyze the formation and stability of thin defending fluid films on structured surfaces.
• To understand the late-time morphologies of trapped fluids in rough geometries.

Main Methods:

• Utilized a microfluidic device with a precisely controlled structured surface to simulate rough fractures.
• Experimentally studied immiscible fluid-fluid displacement under varying degrees of surface roughness.
• Theoretically rationalized the observed phenomena, focusing on thin film stability and dewetting dynamics.

Main Results:

• Demonstrated that surface roughness alters both the stability and dewetting dynamics of thin defending fluid films.
• Observed distinct late-time morphologies of trapped (undisplaced) fluid due to roughness.
• Quantified the impact of roughness on the wetting transition during fluid invasion.

Conclusions:

• Surface roughness plays a critical role in dictating fluid displacement patterns in confined, rough geometries.
• Findings have significant implications for understanding and optimizing processes like geological CO2 sequestration and microfluidic applications.
• The study provides a fundamental understanding of fluid-fluid interactions on rough surfaces.