A 2D Geometrical Perspective for the Contact Angle Hysteresis

Area of Science:

• Surface Science
• Fluid Dynamics
• Materials Science

Background:

• Contact angle and its hysteresis are fundamental to fluid-solid interactions.
• Surface roughness significantly influences contact angle hysteresis.
• A general model for fiber-roughened surfaces is lacking.

Purpose of the Study:

• Derive analytical solutions for contact angle hysteresis on fiber-roughened surfaces.
• Investigate the role of geometry and energy in droplet behavior.
• Validate models with simulations and experiments.

Main Methods:

• Geometrical analysis to derive analytical solutions.
• Calculation of Gibbs free interfacial energy.
• Lattice Boltzmann Method (LBM) simulations and quasi-2D/3D experiments.

Main Results:

• Contact angle hysteresis is geometrically constrained.
• Advancing, receding, and equilibrium contact angles oscillate and approach asymptote values.
• Droplet vibration and energy dissipation occur due to energy cliffs.
• Prewetted surfaces can achieve zero contact angle hysteresis.

Conclusions:

• Analytical models provide insights into contact angle hysteresis on fiber-roughened surfaces.
• Energy analysis reveals non-geometrical equilibrium states.
• Experimental validation confirms theoretical predictions for functional surfaces.