Nature of Dynamic Friction in a Humid Hydrophobic Nanocontact

The physics of dynamic friction on water molecule contaminated surfaces is still poorly understood. In line with the growing interest in hydrophobic contact for industrial applications, this paper focuses on friction mechanisms in such interfaces. As a commonly used material, contact with graphite is considered in a twin-fold approach based on experimental investigations using the circular mode atomic force microscopy technique combined with molecular dynamic simulations. We demonstrate that an intuitive paradigm, which asserts that water molecules are squeezed out of a hydrophobic contact, should be refined. As a consequence, we introduce a mechanism considering a droplet produced within the sliding nanocontact by the accumulation of water adsorbed on the substrate. Then we show that a full slip regime of the droplet sliding on the hydrophobic substrate explains the experimental tribological behavior.

Automated summary

This paper investigates the physics of dynamic friction on water molecule contaminated surfaces, focusing on friction mechanisms in hydrophobic contact. Experimental investigations and molecular dynamic simulations reveal that water molecules form droplets within the sliding nanocontact instead of being squeezed out, leading to a full slip regime on the hydrophobic substrate. This research is of great significance for understanding the dynamic friction behavior of water molecules on surfaces.