Nanodrop impact on solid surfaces

TL;DR

This study uses molecular dynamics simulations to analyze how nanometer-sized liquid drops impact solid surfaces, revealing different behaviors like bouncing, sticking, splashing, or disintegrating depending on impact velocity and material properties.

Contribution

It provides detailed insights into nanodrop impact dynamics, highlighting the effects of velocity and surface wetting properties at the nanoscale, which differ from macroscopic drop behavior.

Findings

Low velocity drops bounce on non-wetting surfaces

High velocity impacts cause splashing and disintegration

Transition between regimes occurs at similar Reynolds and Weber numbers as larger drops

Abstract

The impact of nanometer sized drops on solid surfaces is studied using molecular dynamics simulations. Equilibrated floating drops consisting of short chains of Lennard-Jones liquids with adjustable volatility are directed normally onto an atomistic solid surface where they are observed to bounce, stick, splash or disintegrate, depending on the initial velocity and the nature of the materials involved. Drops impacting at low velocity bounce from non-wetting surfaces but stick and subsequently spread slowly on wetting surfaces. Higher velocity impacts produce an prompt splash followed by disintegration of the drop, while at still higher velocity drops disintegrate immediately. The disintegration can be understood as either a loss of coherence of the liquid or as the result of a local temperature exceeding the liquid-vapor coexistence value. In contrast to macroscopic drops, the presence of vapor outside the drop does not effect the behavior in any significant way. Nonetheless, the transition between the splashing and bouncing/sticking regimes occur at Reynolds and Weber numbers similar to those found for larger drops.