Surface phonon induced rotational dissipation for nanoscale solid-state gears

TL;DR

This study uses molecular dynamics simulations to investigate rotational friction in nanoscale solid-state gears, revealing that surface phonons and van-der-Waals interactions primarily cause energy dissipation.

Contribution

It is the first detailed analysis of rotational friction mechanisms in nanoscale gears, highlighting the role of surface phonons and substrate properties.

Findings

Viscous damping caused by van-der-Waals interactions.

Gear and substrate rigidity influence dissipation channels.

Surface phonons dominate energy dissipation.

Abstract

Compared to nanoscale friction of translational motion, the mechanisms of rotational friction have received less attention. Such motion becomes an important issue for the miniaturization of mechanical machineries which often involve rotating gears. In this study, molecular dynamics simulations are performed to explore rotational friction for solid-state gears rotating on top of different substrates. In each case, viscous damping of the rotational motion is observed and found to be induced by the pure van-der-Waals interaction between gear and substrate. The influence of different gear sizes and various substrate materials is investigated. Furthermore, the rigidities of the gear and the substrate are found to give rise to different dissipation channels. Finally, it is shown that the dominant contribution to the dissipation is related to the excitation of low-frequency surface-phonons in the substrate.