Dynamic Spreading of Droplets on Lyophilic Micropillar-Arrayed Surfaces

Area of Science:

• Surface Science
• Fluid Dynamics
• Materials Science

Background:

• Wetting kinetics on lyophilic pillar-arrayed substrates are crucial for natural phenomena and industrial applications like gas-liquid separation.
• A fringe film preceding the contact line on these surfaces leads to unique wetting dynamics requiring further study.

Purpose of the Study:

• To investigate the early spreading dynamics of droplets on lyophilic micropillar-arrayed surfaces.
• To understand the influence of micropillars on wetting kinetics and develop a predictive model.

Main Methods:

• Utilized Si(100) substrates with square micropillars for droplet-spreading experiments.
• Observed fringe film formation and analyzed spreading radius enhancement.
• Developed a semitheoretical model based on global energetic equations.

Main Results:

• Observed a fringe film ahead of the contact line on micropillar-arrayed surfaces.
• Micropillars enhanced droplet spreading radius, primarily due to liquid penetration into the pillar forest.
• Early spreading was dependent on solid fraction but independent of pillar height.

Conclusions:

• The study elucidates the mechanism of enhanced wetting on lyophilic micropillar surfaces.
• A novel, parameter-free semitheoretical model accurately predicts wetting kinetics.
• The model can aid in designing pillar-arrayed surfaces for practical applications.