Nonwettable Hierarchical Structure Effect on Droplet Impact and Spreading Dynamics

Area of Science:

• Surface Science
• Fluid Dynamics
• Materials Science

Background:

• Understanding droplet impact on surfaces is crucial for various applications.
• Superhydrophobic surfaces offer unique properties for fluid manipulation.
• Hierarchical surface structures can enhance control over droplet dynamics.

Purpose of the Study:

• To investigate the effect of nano/micro hierarchical structures on nonwettable surfaces during droplet impact.
• To analyze how dual-scale superhydrophobic surfaces influence droplet dynamics across a range of capillary pressures.
• To quantify the impact behavior, spreading diameter, and contact time of water droplets.

Main Methods:

• High-speed visualization techniques were employed to observe droplet impact.
• A dual-scale superhydrophobic surface was fabricated to manipulate capillary pressures.
• Distilled water droplets of varying sizes and velocities were impacted onto the prepared surfaces.

Main Results:

• At low Weber numbers (We), droplet spreading and contact time showed minimal dependence on the microscale design.
• At high Weber numbers (We), surface morphology configuration significantly affected droplet impact shape and fragmentation.
• A hierarchical effect was observed, influenced by the balance between surface capillary pressure and droplet impact pressure.

Conclusions:

• Dual-scale surface structures play a critical role in droplet impact dynamics, particularly at higher impact energies.
• The interplay between surface morphology and droplet momentum dictates impact outcomes.
• This research provides insights into designing advanced surfaces for controlled droplet interactions.