With the rapid development of emerging nanoscale technologies, such as nanoprinting, the impact dynamics of nanodroplets have drawn increasing attention. Although impacts on curved surfaces frequently take place, the effect of curvature remains far from being understood. In this work, nanodroplet impacts on solid spheres are compressively investigated by molecular dynamics simulation, and two key feature parameters, including the maximum spreading factor and restitution coefficient, are focused on. For the maximum spreading factor, due to the dominant bulk viscous dissipation and interfacial slip, classical macroscale models no longer hold at the nanoscale. Nonetheless, it is intriguingly found that, even with curvature, the nanoscale flat-surface model can still predict to impacts on solid spheres, because curvature preserves the Hertz-like (low Weber number) and film-like (high Weber number) energy conversion mechanisms observed on flat surfaces. For the restitution coefficient ε (the ratio of bouncing velocity to initial velocity), the dissipation is identified as associated with redirecting horizontal motion into vertical motion during bouncing. With increasing curvature, the vertical kinetic energy gained during retraction increases while the horizontal component that requires redirected decreases, leading to reduced viscous dissipation. On this basis, a curvature-dependent scaling law for ε is derived, which can naturally reduce to a flat-surface model when the ratio of sphere to droplet diameter approaches infinity. The scaling law shows good agreement with not only data on spheres from both present and previous studies, but also points on flat surfaces in the literature, which provides insight into energy conversion mechanisms.
Cai et al. (2026) studied this question.