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Rendering SiO2/Si Surfaces Omniphobic by Carving Gas-Entrapping Microtextures Comprising Reentrant and Doubly Reentrant Cavities or Pillars
Published on: February 11, 2020
Effect of surface texturing on superoleophobicity, contact angle hysteresis, and "robustness"
Hong Zhao1, Kyoo-Chul Park, Kock-Yee Law
1Xerox Corporation, Xerox Research Center Webster, Webster, New York 14580, United States.
Langmuir : the ACS Journal of Surfaces and Colloids
|September 21, 2012
Summary
This study investigates how surface texture affects superhydrophobic and superoleophobic properties. Optimized pillar dimensions and overhangs enhance liquid repellency and surface robustness against pressure and abrasion.
Area of Science:
- Materials Science and Engineering
- Surface Science and Engineering
- Nanotechnology
Background:
- Fluorosilane (FOTS)-modified silicon pillar arrays exhibit superhydrophobic and superoleophobic properties (>150° contact angles).
- These properties are attributed to surface fluorination and re-entrant pillar structures, enabling low sliding angles (~10°).
Purpose of the Study:
- To investigate the influence of surface texturing (pillar size, spacing, height) on wettability, contact angle hysteresis, and robustness.
- To understand the role of solid area fraction and overhang geometry in liquid repellency.
- To model the robustness of superoleophobic surfaces against external pressure and abrasion.
Main Methods:
- Systematic variation of pillar dimensions (diameter, spacing) and solid area fraction.
- Measurement of static, advancing, and receding contact angles, and sliding angles.
- Surface Evolver modeling to simulate liquid-pillar interactions and wetting breakthrough pressure.
- Mechanical modeling to assess abrasion resistance.
Main Results:
- Static and advancing contact angles are insensitive to pillar size and spacing within tested ranges.
- Receding contact angle decreases, while sliding angle and hysteresis increase with higher solid area fraction due to increased pinning.
- Hexadecane penetration into re-entrant structures and overhangs significantly impacts receding angles and hysteresis compared to water.
- Overhang thickness positively correlates with increased contact angles and decreased sliding angles for hexadecane.
- Superoleophobic surfaces with 0.5-μm pillars show high wetting breakthrough pressure (~70 kPa).
- Pillar bending is identified as the primary failure mechanism during abrasion; short pillars mitigate this.
Conclusions:
- Surface texturing, particularly overhang geometry and solid area fraction, critically influences superoleophobic performance and robustness.
- Optimized FOTS pillar array surfaces can achieve superoleophobicity robust against external forces (~30 kPa), suitable for practical applications.
- Design strategies balancing liquid repellency and mechanical durability are essential for fabricating robust superoleophobic surfaces.
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