# Turning drops into bubbles: Elastic cavitation by diffusion

## TL;DR

This paper investigates a model system where a droplet in an elastic medium shrinks via diffusion and then rapidly transforms into a bubble through cavitation, revealing insights into elastic energy release mechanisms.

## Contribution

It introduces a combined diffusive-elastic cavitation model that accurately describes the dynamics of droplet-to-bubble transformation, bridging slow diffusion and rapid cavitation events.

## Key findings

- Diffusive shrinkage follows classical diffusion laws.
- Cavitation dynamics are well-described by an inertial-elastic model.
- The model matches experimental cavity dynamics across nine orders of magnitude.

## Abstract

Some members of the vegetal kingdom can achieve surprisingly fast movements making use of a clever combination of evaporation, elasticity and cavitation. In this process, enthalpic energy is transformed into elastic energy and suddenly released in a cavitation event which produces kinetic energy. Here we study this uncommon energy transformation by a model system: a droplet in an elastic medium shrinks slowly by diffusion and eventually transforms into a bubble by a rapid cavitation event. The experiments reveal the cavity dynamics over the extremely disparate timescales of the process, spanning 9 orders of magnitude. We model the initial shrinkage as a classical diffusive process, while the sudden bubble growth and oscillations are described using an inertial-(visco)elastic model, in excellent agreement with the experiments. Such a model system could serve as a new paradigm for motile synthetic materials.