Split of droplets at the nanoscale using mixed-wettability surfaces: A molecular dynamics simulation

Abstract

The present work is to investigate nanodroplets impacting mixed-wettability surfaces, which are hydrophilic surfaces decorated by hydrophobic stripes, via molecular dynamics (MD) simulations. Based on various impact conditions (W/D0 = 0.1 to 1.5, and We = 1.5 to 410), the different impacting regimes are identified, including the stable non-splitting, coexisting regime, stable splitting, and hybrid regime, where W is the width of hydrophobic stripes and D0 is the diameter of droplets. There shows a significant scale effect for droplets splitting due to the intermolecular force, i.e. existing stable non-splitting regime. And, a new type of droplet splitting pattern is found, namely hole splitting, which would produce some daughter fragments during the impact-splitting process. The splitting time acting as an important parameter for evaluating the performance of splitting dynamics is discussed. Two splitting regimes are distinguished by the dependence/independence of splitting time to the impact We. Finally, a criterion for separating the stable splitting regime by the increasing W/D0 is obtained using a simple energy model. This work paves the way to understanding how to manipulate droplet splitting at the nanoscale.