Nanoscale impingement of binary droplets on liquid films supported by substrates

Impingement of nanodroplets on a liquid film is a crucial step in many advanced technologies, such as nanoscale inkjet printing and spray cooling. However, understanding the impact process in targeted systems involving binary nanodroplets remains insufficient due to the complex interactions between solid–liquid and liquid–liquid interfaces. To fill this gap, we employ molecular dynamics (MD) simulations to systematically investigate the impingement of binary nanodroplets on thin liquid films supported by a Pt substrate and identify three distinct dynamics regimes: regular crown, columnar jet, and central splash. Next, we focus on the effects of We, centroid distance L*, and film thickness H* on the free evolution of targeted systems, particularly on the spreading dynamics. The parameter H* exhibits a particularly interesting influence on spreading dynamics, as increasing its value progressively alters the direction of liquid-crown propagation from oblique to vertical. Based on the observed dynamics, we develop a theoretical model divided into two regimes, H* ≤ 0.5 and H* > 0.5, to predict the value of Rc, max*. The model agrees well with MD results for H* > 0.5, but its accuracy slightly decreases for H* ≤ 0.5 because the liquid film beneath the sink pit becomes very thin. In this regime, solid–liquid interactions can significantly influence the liquid-crown propagation process. This model may provide valuable guidance for optimizing micro- and nanoscale manufacturing processes that require precise control of binary-droplet impingement on liquid films.