Molecular Dynamic Approach of Enhanced Self-Propelled Nano-Droplet Motion on Wettability Gradient Surfaces

TL;DR

This study uses molecular dynamics simulations to investigate how micro-sized droplets move on surfaces with wettability gradients, revealing the influence of temperature and interaction parameters on contact line friction and droplet propulsion.

Contribution

It introduces a detailed MD simulation approach to analyze self-propelled nano-droplet motion on wettability gradient surfaces, linking atomistic interactions to macroscopic behavior.

Findings

Contact line friction decreases with increasing temperature.

Simulation results align with existing models of droplet motion.

Temperature significantly affects droplet propulsion dynamics.

Abstract

Droplet motion over a surface with wettability gradient has been simulated using molecular dynamics (MD) simulation to highlight the underlying physics. GROMACS and Visual Molecular Dynamics (VMD) were used for simulation and intermittent visualization of the droplet configuration respectively. The simulations mimic experiments in a comprehensive manner wherein micro-sized droplets are propelled by surface wettability gradient against a number of retarding forces. The liquid-wall Lennard-Jones interaction parameter and the substrate temperature were varied to explore their effects on the three-phase contact line friction coefficient. The contact line friction was observed to be a strong function of temperature at atomistic scales, confirming the experimentally observed inverse functionality between the coefficient of contact line friction and increase in temperatures. These MD simulation results were successfully compared with the results from a model for self-propelled droplet motion on gradient surfaces.