Wetting properties of molecularly rough surfaces

Area of Science:

• Surface Science
• Nanotechnology
• Computational Physics

Background:

• Surface wettability is crucial for material properties and applications.
• Macroscopic theories like Wenzel's law predict roughness enhances wettability.
• Understanding nanoscale wettability requires atomistic simulations.

Purpose of the Study:

• Investigate the effect of nanoscale roughness on surface wettability.
• Examine how molecular roughness influences contact angles.
• Explore wettability changes for both strongly and weakly interacting surfaces.

Main Methods:

• Molecular dynamics simulations using Lennard-Jones interactions.
• Modeling smooth and molecularly rough planar surfaces with nanogrooves.
• Analyzing equilibrium droplet profiles to determine contact angles.

Main Results:

• Nanoscale roughness deteriorated substrate wettability, contradicting Wenzel's law.
• For strongly wettable surfaces, roughness reduced the liquid-wetted area and minimally affected contact angles.
• For weakly wettable surfaces, roughness induced a lyophilic-to-lyophobic transition.

Conclusions:

• Surface roughness at the nanoscale can decrease wettability.
• The impact of roughness depends on the degree of solid-fluid interaction.
• Nanoscale simulations provide critical insights beyond macroscopic models.