Impalement transitions in droplets impacting microstructured superhydrophobic surfaces

TL;DR

This paper investigates how droplets impact microstructured superhydrophobic surfaces, revealing conditions under which droplets bounce, land in a fakir state, or become impaled, using lattice-Boltzmann simulations.

Contribution

It introduces a two-phase lattice-Boltzmann model to simulate droplet impacts, showing fakir states can occur at higher velocities with increased surface hydrophobicity or post height.

Findings

Fakir state can occur at high impact velocities.

Increased surface hydrophobicity favors fakir state.

Taller posts make impalement less energetically favorable.

Abstract

Liquid droplets impacting a superhydrophobic surface decorated with micro-scale posts often bounce off the surface. However, by decreasing the impact velocity droplets may land on the surface in a fakir state, and by increasing it posts may impale droplets that are then stuck on the surface. We use a two-phase lattice-Boltzmann model to simulate droplet impact on superhydrophobic surfaces, and show that it may result in a fakir state also for reasonable high impact velocities. This happens more easily if the surface is made more hydrophobic or the post height is increased, thereby making the impaled state energetically less favourable.