Biomimetic Water-Repelling Surfaces with Robustly Flexible Structures

Area of Science:

• Materials Science
• Surface Science
• Biomimetics

Background:

• Biomimetic liquid-repelling surfaces are crucial for various applications.
• Existing rigidity-based strategies face limitations in mechanical robustness and repellency enhancement.
• Flexibility-based oscillation strategies offer improvements but have their own drawbacks.

Purpose of the Study:

• To design and fabricate a novel flexible liquid-repelling surface with enhanced mechanical robustness and water repellency.
• To mimic the mushroom-like geometry found on springtail cuticles using advanced fabrication techniques.
• To investigate the surface's performance under mechanical stress and its effect on droplet behavior.

Main Methods:

• Designing a flexible surface with mesoscale heads and microscale spring sets.
• Utilizing three-dimensional projection microstereolithography for fabrication.
• Evaluating mechanical robustness against normal/shear compression and tribological friction.
• Quantifying water repellency enhancement for impacting droplets through impalement resistance and contact time reduction.

Main Results:

• The fabricated surface demonstrated strong mechanical robustness, withstanding compression and tribological friction.
• Water repellency was significantly elevated, with improvements up to ~80% attributed to structural tilting movements.
• The surface effectively enhanced impalement resistance and reduced droplet contact time.
• A flexibility gradient was successfully created for directional droplet manipulation.

Conclusions:

• This study presents the first flexible interfacial structures capable of robustly enduring tribological friction while promoting water repellency.
• The biomimetic design offers a promising approach for real-world water-repelling applications.
• The developed surface enables directional control of droplets, opening avenues for droplet transport technologies.