Frictional scattering and frictional waveguides: achieving persistent superlubricity at high velocity on the nanoscale

TL;DR

This paper investigates high-velocity friction in nanoscale systems, revealing frictional scattering phenomena and proposing waveguide methods to achieve persistent superlubricity, which could enhance nanomechanical device performance.

Contribution

It introduces the concept of frictional scattering at high velocities and demonstrates how graphitic nanoribbons can serve as frictional waveguides to maintain superlubricity.

Findings

Frictional scattering occurs at high velocities due to crystallographic alignment changes.

Frictional waveguides can suppress frictional scattering, enabling persistent superlubricity.

The phenomenon is analogous to Bragg scattering, providing a new understanding of nanoscale friction dynamics.

Abstract

Nanomechanical devices can operate at much higher speeds than their macroscopic analogues, due to low inertia. For example, peak speeds >100m/s have been predicted for carbon nanotube devices. This stimulates our interest in the atomic-scale physics of friction at high velocity. Here we study a model nanosystem consisting of a graphene flake moving freely on a graphite substrate at >100m/s. Using molecular dynamics we discover that ultra-low friction, or superlubricity, is punctuated by high-friction transients as the flake rotates through successive crystallographic alignments with the substrate. We term this phenomenon frictional scattering and show that it is mathematically analogous to Bragg scattering. We also show that frictional scattering can be eliminated by using graphitic nanoribbons as frictional waveguides to constrain the flake rotation, thus achieving persistent superlubricity. Finally, we propose an experimental method to study nanoscale high-velocity friction. These results may guide the design of efficient high-frequency nanomechanical devices.