The Transitional Wettability on Bamboo-Leaf-like Hierarchical-Structured Si Surface Fabricated by Microgrinding

Area of Science:

• Materials Science
• Surface Science
• Microfluidics

Background:

• Stabilizing hydrophobic wetting states is crucial for applications like heat transfer and microfluidics.
• Current hydrophobic silicon (Si) surfaces often rely on unstable low surface energy coatings.
• These coatings limit the practical industrial applications of hydrophobic Si surfaces.

Purpose of the Study:

• To develop a stable hydrophobic silicon surface using a novel texturing method.
• To investigate the wettability transitions and droplet behavior on these textured surfaces.
• To explore potential applications in microfluidics and heat transfer.

Main Methods:

• Fabrication of bamboo-leaf-like hierarchical structures (BLHSs) on Si chips using a one-step diamond grinding process.
• Characterization of surface wettability through contact angle measurements before and after droplet impacts.
• Evaluation of droplet splitting, transfer, and self-sucking capabilities on modified surfaces.
• Development of a fractal theory-based wetting model for BLHS surfaces.

Main Results:

• Achieved stable transitional hydrophobic silicon surfaces with contact angles up to 97°.
• Demonstrated minimal contact angle reduction (2%) after droplet impacts, indicating high stability.
• Showcased efficient droplet splitting and transfer with 100% mass retention.
• Upgraded surfaces to superhydrophobic (CA > 135°) with low surface energy coatings.
• Observed rapid (0.1 s) self-sucking of droplets into micro-tubes without external forces.

Conclusions:

• One-step micromachining of hard, brittle materials like silicon can create stable transitional wettability surfaces.
• Bamboo-leaf-like hierarchical structures offer superior hydrophobic stability and droplet manipulation capabilities.
• This approach enhances the application potential of silicon in advanced technological fields.