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Superhydrophobic stability of nanotube array surfaces under impact and static forces
1Polymer Science and Engineering Department, School of Chemistry and Chemical Engineering, State Key Laboratory of Coordination Chemistry, Nanjing University , Nanjing, Jiangsu 210093, China.
ACS Applied Materials & Interfaces
|May 31, 2014
Summary
Researchers developed superhydrophobic nanotube surfaces using PMMA, PDNS, and PFO coatings. Stable superhydrophobicity requires high surface energy materials and dense nanostructures to withstand extreme pressures.
Area of Science:
- Materials Science
- Surface Chemistry
- Nanotechnology
Background:
- Superhydrophobic surfaces mimic natural phenomena, offering potential for advanced applications.
- Maintaining superhydrophobicity under external pressures is crucial for practical use.
- Nanotube arrays provide a versatile platform for creating structured surfaces.
Purpose of the Study:
- To fabricate and characterize superhydrophobic nanotube array surfaces with different coatings.
- To evaluate the stability of superhydrophobicity under dynamic impact and static pressures.
- To understand the transition mechanism from Cassie-Baxter to Wenzel modes and identify factors influencing stability.
Main Methods:
- Fabrication of nanotube arrays using anodized alumina membranes and poly(methyl methacrylate) (PMMA) imprinting.
- Surface modification with silane coupling agents: (3-aminopropyl)trimethoxysilane (PDNS) and perfluorooctyltriethoxysilane (PFO).
- Contact angle measurements to assess hydrophobicity and superhydrophobicity.
- Pressure tests (dynamic impact and static) to evaluate superhydrophobic stability and determine maximum pressure (p(max)).
Main Results:
- Three superhydrophobic surfaces (PDNS, PMMA, PFO) were successfully prepared with high contact angles (155-168°).
- Surface stability varied, with PFO showing the highest potential for extreme conditions due to its low surface energy.
- All surfaces transitioned to the Wenzel mode under high pressure (0.5 MPa), losing superhydrophobicity irreversibly.
- Maximum pressure (p(max)) for stability depends on intrinsic contact angle and nanotube density.
Conclusions:
- Superhydrophobicity of nanotube arrays can be tuned by surface chemistry and nanostructure density.
- Achieving robust superhydrophobicity requires maximizing p(max) through low surface energy materials and high-density nanostructures.
- Irreversible transition to the Wenzel mode under extreme pressure highlights limitations and areas for future material design.
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