Frictional Duality Observed during Nanoparticle Sliding

TL;DR

This study investigates nanoscale friction by measuring the resistance of nanoparticles using an atomic force microscope, revealing two coexisting frictional states linked to surface contamination.

Contribution

It provides experimental evidence of dual frictional states at the nanoscale and explores their dependence on surface contamination.

Findings

Some nanoparticles exhibit finite, area-dependent friction.

Others demonstrate frictionless sliding.

Frictional states are correlated with surface contamination levels.

Abstract

One of the most fundamental questions in tribology concerns the area dependence of friction at the nanoscale. Here, experiments are presented where the frictional resistance of nanoparticles is measured by pushing them with the tip of an atomic force microscope. We find two coexisting frictional states: While some particles show finite friction increasing linearly with the interface areas of up to 310,000nm^2, other particles assume a state of frictionless sliding. The results further suggest a link between the degree of surface contamination and the occurrence of this duality.