Viscous flow over a chemically patterned surface

Area of Science:

• Fluid dynamics
• Surface science
• Materials science

Background:

• The classical no-slip boundary condition in fluid dynamics assumes wettability does not influence liquid flow.
• Experimental and simulation data contradict this assumption, showing wettability effects on fluid behavior.
• Understanding these effects is crucial for microfluidics and material design.

Purpose of the Study:

• To describe fluid flow over solid substrates with varying wettability using a continuum framework.
• To investigate how changes in surface chemistry impact shear flow.
• To quantify the relationship between wettability and flow disturbance.

Main Methods:

• Application of the interface formation theory in a continuum framework.
• Analysis of shear flow over a flat solid surface with altered wettability.
• Theoretical modeling to determine the effect's magnitude.

Main Results:

• Shear flow over a flat solid surface is demonstrably disturbed by changes in wettability.
• The disturbance is directly linked to alterations in the solid substrate's chemistry.
• The magnitude of the flow disturbance is proportional to the difference in equilibrium contact angles (cos θ1 - cos θ2).

Conclusions:

• Wettability variations on solid surfaces significantly affect adjacent fluid flow, contrary to the classical no-slip condition.
• The interface formation theory provides a valid continuum framework for describing these phenomena.
• The findings offer a quantitative relationship for predicting flow behavior based on surface properties and contact angles.