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How Water Makes the Surface Slippery; Friction on Water/Au(111) Investigated with Variable-Pressure Friction Force
Hunyoung Cho1, Won-Bin Kang2, Daeho Kim1
1Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Republic of Korea.
ACS Nano
|November 10, 2025
Summary
Water adsorption on metal surfaces reduces friction and suppresses plastic deformation. This lubrication effect is due to water molecules dissipating energy through hydrogen bond disruption under load.
Area of Science:
- Tribology
- Surface Science
- Nanotechnology
Background:
- Understanding water's influence on tribological properties is key for lubrication science.
- Precise control of water vapor pressure and nanotribological measurements are challenging.
Purpose of the Study:
- Investigate water's effect on friction and surface morphology of Au(111).
- Elucidate the mechanism of water-induced lubrication and plastic deformation suppression.
Main Methods:
- Variable-pressure atomic force microscopy (VP-AFM) for friction and morphology.
- Near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) for water adsorption.
- Molecular dynamics (MD) simulations for nanoscale mechanisms.
Main Results:
- Friction decreased with increasing water vapor pressure due to adsorption.
- Water layers suppressed plastic deformation induced by AFM tip loading.
- Higher water vapor pressure reduced dislocation density and facilitated bond breaking in water networks.
Conclusions:
- Water acts as a nanoscale passivating agent on metal surfaces in humid environments.
- Water's lubricating role is attributed to energy dissipation via hydrogen bond disruption.
- Findings highlight the importance of humidity in tribological behavior.
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