Impact of beads and drops on a repellent solid surface: a unified description

TL;DR

This study presents a unified theoretical framework for impact dynamics of soft beads and drops on a special surface, revealing a universal behavior that encompasses solids, liquids, and viscoelastic fluids, with a new material-dependent velocity parameter.

Contribution

It introduces a unified description of impact dynamics across different materials by incorporating elastocapillary effects and identifies a novel impact velocity characteristic.

Findings

Unified impact behavior across solids, liquids, and viscoelastic fluids

Introduction of a material-dependent impact velocity

Experimental validation of the theoretical framework

Abstract

We investigate freely expanding sheets formed by ultrasoft gel beads, and liquid and viscoelastic drops, produced by the impact of the bead or drop on a silicon wafer covered with a thin layer of liquid nitrogen that suppresses viscous dissipation thanks to an inverse Leidenfrost effect. Our experiments show a unified behaviour for the impact dynamics that holds for solids, liquids, and viscoelastic fluids and that we rationalize by properly taking into account elastocapillary effects. In this framework, the classical impact dynamics of solids and liquids as far as viscous dissipation is negligible, appears as the asymptotic limits of a universal theoretical description. A novel material-dependent characteristic velocity that includes both capillary and bulk elasticity emerges from this unified description of the physics of impact.