The speed-locking effect of particles on a graphene layer with travelling surface wave

Dan Wang,Lifeng Wang,Zhili Hu

doi:10.1186/s11671-020-03434-6

Dan Wang, Lifeng Wang + Show 1 more

Open Access

https://doi.org/10.1186/s11671-020-03434-6

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Abstract

Fast diffusion induced by thermal fluctuation and vibration has been detected at nanoscales. In this paper, the movement of particle on a graphene layer with travelling surface wave is studied by molecular dynamics simulation and theoretical model. It is proved that the particle will keep moving at the wave speed with certain prerequisite conditions, namely speed-locking effect. By expressing van der Waals (vdW) potential between particle and wavy surface as a function of curvatures, the mechanism is clarified based on the puddle of potential in a relative wave-frame coordinate. Two prerequisite conditions are proposed: the initial position of particle should locate in the potential puddle, and the initial kinetic energy cannot drive particle to jump out of the potential puddle. The parametric analysis indicates that the speed-locking region will be affected by wavelength, amplitude and pair potential between particle and wave. With smaller wavelength, larger amplitude and stronger vdW potential, the speed-locking region is larger. This work reveals a new kind of coherent movement for particles on layered material based on the puddle potential theory, which can be an explanation for fast diffusion phenomena at nano scales.

Highlights

A series of surface wave/phonon-induced fast transport and diffusion phenomena are detected at micro/nanoscale
Thermally driven water droplet transport on graphene and hexagonal boron nitride (h-BN) surfaces is studied by molecular dynamics
It is found that the relative position of particle does not change in reference to the wave crests or troughs, which means the particle is locked on the wavy surface with its speed equal to the wave speed

Summary

Introduction

A series of surface wave/phonon-induced fast transport and diffusion phenomena are detected at micro/nanoscale. The thermophoric phenomena along a carbon nanotube [1–5] or a graphene ribbon [6–10] have been extensively investigated. Thermal fluctuations are confirmed to enable continuous water flow through a carbon nanotube (CNT) by imposing an axial thermal gradient along its surface [11–13]. Nonequilibrium molecular dynamics simulations are done to explore the feasibility of utilizing a thermal gradient on a large graphene substrate to control the motion of a small graphene nanoflake [6]. Thermally driven water droplet transport on graphene and hexagonal boron nitride (h-BN) surfaces is studied by molecular dynamics. In addition to thermal fluctuation, studies confirm that the vibration can transport particles and droplets in and outside a carbon nanotube (CNT) [24–27]. Guo et al demonstrated that water molecules inside a vibrating cantilever are driven by centrifugal forces and can undergo a

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