Influence of Graphene Wettability on Spreading Patterns of Nanodroplets Impacting at High Speed

TL;DR

This study uses atomistic molecular dynamics to explore how graphene's wettability influences the impact behavior of nanodroplets at high velocities, revealing distinct impact regimes and the critical role of void formation in spreading dynamics.

Contribution

It provides new insights into the impact dynamics of nanodroplets on graphene, highlighting the effects of wettability tuning and identifying velocity-dependent impact regimes.

Findings

Three impact regimes identified: deposition, spreading with rebound, and fragmentation.

Void formation at intermediate velocities critically alters spreading behavior.

Droplet fragmentation occurs at velocities above 11 Å/ps, indicating maximum spreading.

Abstract

We report here a fully atomistic molecular dynamics study on the dynamics of impact of water nanodroplets (100 {\AA} of diameter) at high velocities (from 1 up to 15 {\AA}/ps) against graphene targets. Our results show that tuning graphene wettability (through parameter changes) significantly affects the structural and dynamical aspects of the nanodroplets. We identified three ranges of velocities with distinct characteristics, from simple deposition of the droplet to spreading with rebound, and finally droplet fragmentation. We also identify that in an intermediary velocity of 7 {\AA}/ps, the pattern of spreading critically changes, due to formation of voids on droplet structure. These voids affect in a detrimental way the droplet spreading on the less hydrophilic surface, as it takes more time to the droplet recover from the spreading and to return to a semi-spherical configuration. When the velocity is increased to values larger than 11 {\AA}/ps, the droplet fragments, which reveals the maximum possible spreading.