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Hydrophobicity Does Not Affect Water Slip: Insights from Slip Length Mapping.
Haruya Ishida1, Koji Takahashi1,2, Vishwanath Ganesan3
1Department of Aeronautics and Astronautics, Kyushu University, Nishi-Ku, Motooka 744, Fukuoka 819-0395, Japan.
Nano Letters
|May 15, 2026
Summary
Researchers precisely measured fluid slip at solid-water interfaces. True slip lengths are near zero on most surfaces, except for unique graphite behavior in deionized water, advancing understanding of fluid dynamics.
Area of Science:
- Fluid dynamics
- Surface science
- Nanotechnology
Background:
- Solid-water interface slip is crucial but poorly understood.
- Experimental slip length measurements vary due to surface heterogeneity.
- Quantitative understanding requires precise nanoscale measurements.
Purpose of the Study:
- To precisely map nanoscale fluid slip and surface topography simultaneously.
- To overcome limitations in slip length detection sensitivity.
- To establish a unified experimental picture of fluid slip.
Main Methods:
- Utilized highly sensitive frequency-modulation atomic force microscopy (FM-AFM).
- Achieved a 159-fold improvement in slip length detection sensitivity.
- Simultaneously mapped slip length and surface topography at the nanoscale.
Main Results:
- True slip lengths on flat regions of various substrates were near zero.
- Measurements align with molecular dynamics simulation predictions.
- A large slip length on graphite in deionized water vanished with electrolytes due to ion adsorption.
Conclusions:
- Demonstrated near-zero slip on most atomically smooth, homogeneous surfaces.
- Explained unique slip behavior on graphite via its properties and ion adsorption.
- Advanced experimental capabilities for unified fluid slip research.
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