Stick-Slip Control in Nanoscale Boundary Lubrication by Surface Wettability

TL;DR

This study investigates how surface wettability influences nanoscale boundary-lubricated friction, revealing that hydrophilic surfaces induce stick-slip behavior while hydrophobic surfaces promote smooth sliding, based on molecular dynamics simulations.

Contribution

It demonstrates the atomic-scale mechanisms by which surface wettability controls stick-slip dynamics in nanoscale boundary lubrication.

Findings

Stick-slip occurs on hydrophilic mica surfaces with thin water layers.

Hydrophobic graphene surfaces exhibit smooth sliding without stick-slip.

Surface wettability determines the presence of stick-slip in nanoscale friction.

Abstract

We study the effect of atomic scale surface-lubricant interactions on nanoscale boundary-lubricated friction, by considering two example surfaces - hydrophilic mica and hydrophobic graphene - confining thin layers of water in molecular dynamics simulations. We observe stick-slip dynamics for thin water films confined by mica sheets, involving periodic breaking-reforming transitions of atomic scale capillary water bridges formed around the potassium ions of mica. However, only smooth sliding without stick-slip events is observed for water confined by graphene, as well as for thicker water layers confined by mica. Thus, our results illustrate how atomic scale details affect the wettability of the confining surfaces, and consequently control the presence or absence of stick-slip dynamics in nanoscale friction.