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SUMMARY:Coupling the Leidenfrost Effect and Elastic Deformations to Power 
 Sustained Bouncing - Scott Waitukaitis (Universiteit Leiden\; FOM Institut
 e AMOLF)
DTSTART:20170919T141000Z
DTEND:20170919T143000Z
UID:TALK80181@talks.cam.ac.uk
CONTACT:INI IT
DESCRIPTION:The   Leidenfrost effect occurs when an object near a hot surf
 ace vaporizes rapidly   enough to lift itself up and hover. Although well-
 understood for liquids and   stiff sublimable solids\, nothing is known ab
 out the effect with materials   whose stiffness lies between these extreme
 s. Here we introduce a new   phenomenon that occurs with vaporizable soft 
 solids: the elastic Leidenfrost   effect. By dropping hydrogel spheres ont
 o hot surfaces we find that\, rather   than hovering\, they energetically 
 bounce several times their diameter for   minutes at a time. With high-spe
 ed video during a single impact\, we uncover   high-frequency microscopic 
 gap dynamics at the sphere-substrate interface. We   show how these otherw
 ise-hidden agitations constitute work cycles that   harvest mechanical ene
 rgy from the vapour and sustain the bouncing. Our   findings unleash a wid
 ely applicable strategy for injecting mechanical energy   into soft materi
 als\, with potential relevance to fields ranging from soft   robotics and 
 metamaterials to microfluidics and active matter.
LOCATION:Seminar Room 1\, Newton Institute
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