Sessile Droplet Freezing on Hydrophobic Structured Surfaces under Cold Ambient Conditions

Area of Science:

• Materials Science
• Surface Science
• Physics

Background:

• Conflicting reports exist on surface wettability's role in enhancing water droplet freezing delay.
• Effective anti-icing surfaces are critical for aircraft wings and infrastructure.
• Frost formation can alter wetting and nucleation, complicating freezing studies.

Purpose of the Study:

• To investigate the impact of surface wettability and nanostructuring on water droplet freezing delay.
• To elucidate the mechanisms behind freezing delay enhancement on different surfaces.
• To provide insights for designing advanced anti-icing materials.

Main Methods:

• Preparation of smooth, microstructured, and nanostructured surfaces with hydrophobic coatings.
• Characterization of static and dynamic wetting properties.
• Observation of precooled water droplet freezing behavior under controlled ambient conditions.

Main Results:

• Nanostructured surfaces with static contact angles >150° exhibited significantly prolonged freezing delay times.
• Smooth and microstructured surfaces showed less pronounced freezing delay.
• Droplet adhesion differences due to nanostructures had a negligible effect on freezing delay.

Conclusions:

• Reduced actual contact area between water and nanostructured surfaces restricts ice nucleus formation.
• Surface nanostructuring, rather than just hydrophobicity, is key to enhancing freezing delay.
• Findings offer a pathway for developing superior anti-icing technologies.