Coupling the Leidenfrost Effect and Elastic Deformations to Power Sustained Bouncing

22 mins 17 secs, 85.21 MB, iPod Video 480x270, 29.97 fps, 44100 Hz, 522.11 kbits/sec

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Description:	Waitukaitis, S Tuesday 19th September 2017 - 15:10 to 15:30


Created:	2017-09-20 15:04
Collection:	Growth form and self-organisation
Publisher:	Isaac Newton Institute
Copyright:	Waitukaitis, S
Language:	eng (English)


Abstract:	The Leidenfrost effect occurs when an object near a hot surface vaporizes rapidly enough to lift itself up and hover. Although well-understood for liquids and stiff sublimable solids, nothing is known about the effect with materials whose stiffness lies between these extremes. Here we introduce a new phenomenon that occurs with vaporizable soft solids: the elastic Leidenfrost effect. By dropping hydrogel spheres onto hot surfaces we find that, rather than hovering, they energetically bounce several times their diameter for minutes at a time. With high-speed video during a single impact, we uncover high-frequency microscopic gap dynamics at the sphere-substrate interface. We show how these otherwise-hidden agitations constitute work cycles that harvest mechanical energy from the vapour and sustain the bouncing. Our findings unleash a widely applicable strategy for injecting mechanical energy into soft materials, with potential relevance to fields ranging from soft robotics and metamaterials to microfluidics and active matter.

Abstract:

The Leidenfrost effect occurs when an object near a hot surface vaporizes rapidly enough to lift itself up and hover. Although well-understood for liquids and stiff sublimable solids, nothing is known about the effect with materials whose stiffness lies between these extremes. Here we introduce a new phenomenon that occurs with vaporizable soft solids: the elastic Leidenfrost effect. By dropping hydrogel spheres onto hot surfaces we find that, rather than hovering, they energetically bounce several times their diameter for minutes at a time. With high-speed video during a single impact, we uncover high-frequency microscopic gap dynamics at the sphere-substrate interface. We show how these otherwise-hidden agitations constitute work cycles that harvest mechanical energy from the vapour and sustain the bouncing. Our findings unleash a widely applicable strategy for injecting mechanical energy into soft materials, with potential relevance to fields ranging from soft robotics and metamaterials to microfluidics and active matter.

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