Nanoscopic spontaneous motion of liquid trains: non-equilibrium molecular dynamics simulation

TL;DR

This study uses molecular dynamics simulations to investigate the spontaneous motion of liquid trains in nanoscale tubes, revealing how surface tension and wetting conditions influence flow behavior at the molecular level.

Contribution

It demonstrates nanoscale spontaneous liquid train motion through molecular dynamics, analyzing flow profiles and deviations from classical laws under various conditions.

Findings

Flow resembles Poiseuille law at small radius-to-length ratios

Surface tension asymmetries drive spontaneous motion

Deviations from classical flow profiles are explained

Abstract

Macroscale experiments show that a train of two immiscible liquid drops, a bislug, can spontaneously move in a capillary tube because of surface tension asymmetries. We use molecular dynamics simulation of Lennard-Jones fluids to demonstrate this phenomenon for NVT ensembles in sub-micron tubes. We deliberately tune the strength of intermolecular forces and control the velocity of bislug in different wetting and viscosity conditions. We compute the velocity profile of particles across the tube, and explain the origin of deviations from the classical parabolae. We show that the self-generated molecular flow resembles the Poiseuille law when the ratio of the tube radius to its length is less than a critical value.