Linking plasma formation in grapes to microwave resonances of aqueous dimers

The sparking of cut grape hemispheres in a household microwave oven has been a poorly explained Internet parlor trick for over two decades. By expanding this phenomenon to whole spherical dimers of various grape-sized fruit and hydrogel water beads, we demonstrate that the formation of plasma is due...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2019-03, Vol.116 (10), p.4000-4005
Main Authors: Khattak, Hamza K., Bianucci, Pablo, Slepkov, Aaron D.
Format: Article
Language:English
Subjects:
Absorptivity
Beads
Dielectric constant
Dimers
Grapes
Hemispheres
Hydrogels
Microwave oven
Physical Sciences
Thermal imaging
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Summary:The sparking of cut grape hemispheres in a household microwave oven has been a poorly explained Internet parlor trick for over two decades. By expanding this phenomenon to whole spherical dimers of various grape-sized fruit and hydrogel water beads, we demonstrate that the formation of plasma is due to electromagnetic hotspots arising from the cooperative interaction of Mie resonances in the individual spheres. The large dielectric constant of water at the relevant gigahertz frequencies can be used to form systems that mimic surface plasmon resonances that are typically reserved for nanoscale metallic objects. The absorptive properties of water furthermore act to homogenize higher-mode profiles and to preferentially select evanescent field concentrations such as the axial hotspot. Thus, beyond providing an explanation for a popular-science phenomenon, we outline a method to experimentally model subwavelength field patterns using thermal imaging in macroscopic dielectric systems.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.1818350116