Leidenfrost droplet trampolining

Gustav Graeber,Pascal Hodel,Dominic Landolf,Christian Küttel,Kartik Regulagadda,Dimos Poulikakos,Thomas M Schutzius

doi:10.1038/s41467-021-21981-z

Abstract

A liquid droplet dispensed over a sufficiently hot surface does not make contact but instead hovers on a cushion of its own self-generated vapor. Since its discovery in 1756, this so-called Leidenfrost effect has been intensively studied. Here we report a remarkable self-propulsion mechanism of Leidenfrost droplets against gravity, that we term Leidenfrost droplet trampolining. Leidenfrost droplets gently deposited on fully rigid surfaces experience self-induced spontaneous oscillations and start to gradually bounce from an initial resting altitude to increasing heights, thereby violating the traditionally accepted Leidenfrost equilibrium. We found that the continuously draining vapor cushion initiates and fuels Leidenfrost trampolining by inducing ripples on the droplet bottom surface, which translate into pressure oscillations and induce self-sustained periodic vertical droplet bouncing over a broad range of experimental conditions.

Highlights

A liquid droplet dispensed over a sufficiently hot surface does not make contact but instead hovers on a cushion of its own self-generated vapor
Intensive research in the past centuries revealed that the Leidenfrost effect is not limited to the classical case of a water droplet on a hot rigid surface
It has been shown that the Leidenfrost effect can reduce the heat transfer between droplet and substrate with significant negative consequences in all related applications, but that it can e.g., provide controlled droplet motion[16,17], reduce fluidic drag[20], or enhance chemical reactions[21]

Summary

Introduction

A liquid droplet dispensed over a sufficiently hot surface does not make contact but instead hovers on a cushion of its own self-generated vapor. It is widely accepted that the droplet and the vapor co-exist in a quasistatic Leidenfrost equilibrium, which determines the droplet shape and the vapor cushion thickness based on a balance between gravity, surface tension, and lifting force resulting from the draining vapor[22,23,24].

Results

Conclusion