Dynamic wetting by liquids of different viscosity

Area of Science:

• Fluid dynamics
• Surface science
• Physical chemistry

Background:

• Dynamic contact angle is crucial in processes like coating and printing.
• Understanding the microscopic mechanisms of dynamic wetting is essential for controlling fluid behavior at interfaces.
• Previous models often simplified the complex dynamics of interface formation.

Purpose of the Study:

• To experimentally determine the velocity-dependence of the dynamic contact angle.
• To analyze the dominant microscopic mechanism governing interface formation during dynamic wetting.
• To validate a theoretical model for dynamic wetting based on interface disappearance-formation.

Main Methods:

• Experimental measurements of dynamic contact angle for water-glycerol solutions.
• Systematic variation of solution viscosity (1.5 to 672 mPa s).
• Interpretation of results using a theoretical framework of dynamic wetting.

Main Results:

• The velocity-dependence of the dynamic contact angle was characterized across a wide viscosity range.
• Experimental data were well-described by assuming a diffusive nature for the interface formation mechanism.
• Phenomenological parameters for the dynamic wetting model were estimated.

Conclusions:

• A diffusive mechanism is a key factor in interface formation during dynamic wetting.
• The proposed theory adequately describes experimental observations for dynamic contact angle.
• This research provides insights into the microscopic physics of wetting phenomena.