Controllable wetting characteristics of hierarchically structured surfaces.

Area of Science:

• Surface Science and Nanotechnology
• Materials Science
• Computational Physics

Background:

• Hydrophobic surfaces with two-level topography are vital for ice repellency and self-cleaning.
• Current research often lacks a deep understanding of the underlying mechanisms governing wetting on these complex surfaces.

Purpose of the Study:

• To investigate the wetting characteristics of nanoscale water films on hierarchically structured surfaces.
• To elucidate the mechanisms behind different wetting regimes using molecular dynamics simulations.
• To design novel surfaces with switchable wetting properties.

Main Methods:

• Molecular dynamics (MD) simulations using the monoatomic water (mW) model.
• Indirect umbrella sampling (INDUS) calculations for free-energy pathways.
• Analysis of wetting regimes based on Young contact angles (θ_Y).

Main Results:

• Identified three wetting regimes: metastable nonwetting (θ_Y = 84.6°), coexisting one/two-level wetting (θ_Y = 107.4°), and stable nonwetting (θ_Y = 135.3°).
• The coexisting regime exhibits a metastable one-level wetting state due to asymmetric energy barriers.
• Two-level topography at θ_Y = 135.3° eliminates dewetting barriers, enabling spontaneous dewetting.
• A novel wetting-functional surface with dispersed nanoparticles promotes self-dewetting.

Conclusions:

• The study provides a mechanistic understanding of wetting on complex hierarchical surfaces.
• Findings guide the design of surfaces with tunable wetting states for advanced applications.
• The developed wetting-functional surface demonstrates effective self-dewetting capabilities.