Bulk-cusp microstructure for controllable multi-directional liquid spreading

Area of Science:

• Surface Science
• Fluid Dynamics
• Materials Engineering

Background:

• Controllable liquid wetting on solid surfaces is crucial for advanced applications.
• Existing methods for liquid spreading are typically limited to unidirectional control.
• Achieving multi-directional liquid spreading on microstructured surfaces presents a significant challenge.

Purpose of the Study:

• To introduce a novel bulk-cusp microstructure for multi-directional liquid spreading.
• To demonstrate controllable 0 to 4-directional droplet spreading without external energy input.
• To explore the influence of microstructure geometry on liquid spreading dynamics.

Main Methods:

• Fabrication of bulk-cusp microstructures with varying bulk shapes (cross and square).
• Experimental investigation of single-drop deposition and continuous liquid injection.
• Mechanism analysis focusing on capillary forces and precursor film dynamics.

Main Results:

• The novel microstructure enables 0 to 4-directional liquid spreading without external energy.
• Cross-shaped bulk structures facilitate controllable spreading via precursor film drag.
• Square-shaped bulk structures offer guidance for the precursor film due to lower coverage.
• Capillary forces in cusp gaps effectively separate the precursor film.

Conclusions:

• The shape of the bulk structure dictates precursor film coverage, influencing droplet body coupling.
• Controllable multi-directional liquid spreading is achieved through tailored microstructure design.
• Potential applications include enhanced lubrication and smart evaporation cooling systems.