Dynamic characteristics of impacting binary nanodroplets on solid surfaces: From hydrophobic to superhydrophobic

Abstract

Droplet impact on hydrophobic solid surfaces holds considerable importance in various industrial applications and remains a prominent subject in both academia and industry. Although the dynamic characteristics of single droplets are relatively well understood, understanding the more critical and complex impact process involving binary droplets at the nanoscale is limited. To address this gap, we employ molecular dynamics (MD) simulations to investigate the dynamic behavior of impacting binary nanodroplets on surfaces ranging from hydrophobic to superhydrophobic. Through our MD simulations, we directly capture detailed dynamic evolutions under various conditions, encompassing primary and secondary spreading followed by depositing or bouncing. Specifically, we focus on the spreading dynamics associated with a maximum spread diameter (βmax), which are directly related to various practical applications. Taking the scale effect into consideration, we propose a new scaling law to predict βmax for impacting binary nanodroplets. By comprehensively examining all the observed outcomes, we develop a phase diagram to gain comprehensive insights into the impact process of binary droplets. This work contributes to a holistic understanding of how binary droplets behave upon impinging hydrophobic or superhydrophobic surfaces, paving the way for advancements in this field.