Modeling Leidenfrost levitation of soft elastic solids

TL;DR

This paper develops a theoretical model for the elastic Leidenfrost effect, revealing how soft solids float on hot surfaces due to a complex interplay of thermodynamics, elasticity, and lubrication, with implications for soft machine design.

Contribution

It introduces a new theory describing elastic Leidenfrost floating, including a dimensionless number capturing the transition between rigid and elastic regimes.

Findings

Heavier solids can float higher in the elasticity-dominated regime.

The float height scales with material parameters according to derived laws.

The theory aligns with recent experimental observations.

Abstract

The elastic Leidenfrost effect occurs when a vaporizable soft solid is lowered onto a hot surface. Evaporative flow couples to elastic deformation, giving spontaneous bouncing or steady-state floating. The effect embodies an unexplored interplay between thermodynamics, elasticity, and lubrication: despite being observed, its basic theoretical description remains a challenge. Here, we provide a theory of elastic Leidenfrost floating. As weight increases, a rigid solid sits closer to the hot surface. By contrast, we discover an elasticity-dominated regime where the heavier the solid, the higher it floats. This geometry-governed behavior is reminiscent of the dynamics of large liquid Leidenfrost drops. We show that this elastic regime is characterized by Hertzian behavior of the solid's underbelly and derive how the float height scales with materials parameters. Introducing a dimensionless elastic Leidenfrost number, we capture the crossover between rigid and Hertzian behavior. Our results provide theoretical underpinning for recent experiments, and point to the design of novel soft machines.