Critical length limiting super-low friction

TL;DR

This paper investigates the limits of superlubricity in nanoscale systems, establishing a theoretical model that predicts the critical length beyond which super-low friction fails, based on material properties and experimental conditions.

Contribution

The authors develop a parameter-free analytical model linking critical length for superlubricity to material and experimental parameters, validated by numerical simulations.

Findings

Superlubricity persists below a critical length.

A high-friction stick-slip mechanism causes failure beyond critical length.

The model accurately predicts the critical length for superlubricity.

Abstract

Since the demonstration of super-low friction (superlubricity) in graphite at nanoscale, one of the main challenges in the field of nano- and micro-mechanics was to scale this phenomenon up. A key question to be addressed is to what extent superlubricity could persist, and what mechanisms could lead to its failure. Here, using an edge-driven Frenkel-Kontorova model, we establish a connection between the critical length above which superlubricity disappears and both intrinsic material properties and experimental parameters. A striking boost in dissipated energy with chain length emerges abruptly due to a high-friction stick-slip mechanism caused by deformation of the slider leading to a local commensuration with the substrate lattice. We derived a parameter-free analytical model for the critical length that is in excellent agreement with our numerical simulations. Our results provide a new perspective on friction and nano-manipulation and can serve as a theoretical basis for designing nano-devices with super-low friction, such as carbon nanotubes.