{"id":13724,"date":"2017-12-11T15:05:04","date_gmt":"2017-12-11T13:05:04","guid":{"rendered":"https:\/\/www.iemn.fr\/articles-temporaires-anglais\/une-galerie-des-murmures-dans-une-goutte-deau-2.html"},"modified":"2019-10-10T14:50:59","modified_gmt":"2019-10-10T12:50:59","slug":"une-galerie-des-murmures-dans-une-goutte-deau","status":"publish","type":"post","link":"https:\/\/www.iemn.fr\/en\/news\/une-galerie-des-murmures-dans-une-goutte-deau.html","title":{"rendered":"A whispering gallery in a drop of water"},"content":{"rendered":"

\nAcoustic waves can be used to control, agitate and mix fluids with extreme precision. Researchers at the Institut d'\u00e9lectronique, de micro\u00e9lectronique et de nanotechnologie, the Mati\u00e8re et syst\u00e8mes complexes laboratory and the Institut des nanosciences de Paris have explained how these waves can induce the formation of vortices on the scale of a drop of water. This mechanism is similar to the acoustic phenomenon of the whispering gallery. This work is published in the Journal of Fluid Mechanics, where it is highlighted by a Focus on Fluids.
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Highly prized in the biomedical field, microfluidics involves manipulating very small volumes of liquid. While mixing remains a complex operation on these scales, it can be achieved using surface acoustic waves. These waves, with a frequency in the megahertz range, gradually transfer their momentum to the fluid, which then becomes agitated, forming micro-vortices. Researchers at the Institute of Electronics, Microelectronics and Nanotechnology (IEMN<\/a>CNRS\/Universit\u00e9 Lille 1\/ISEN Lille\/Universit\u00e9 Valenciennes\/UVHC\/\u00c9cole Centrale Lille), the Mati\u00e8re et syst\u00e8mes complexes (MSC<\/a>CNRS\/Universit\u00e9 Paris Diderot) and the Institut des nanosciences de Paris (INSP<\/a>(CNRS\/UPMC) have highlighted the particular topologies of the vortices in a phenomenon similar to a whispering gallery. In this architectural curiosity, sound can be perceived over long distances because it is focused along the vaults. In this way, two people can converse in hushed tones on either side of certain domes.<\/p>\n

Here, numerical calculations have revealed the focusing of a group of waves that propagate in periodic orbits along the surface of the drop. They are completely reflected when they reach the inner edge of the drop, the interface between the air and the liquid, and are guided in elliptical loops. The spherical cap shape of the drop, shaped by its surface tension, is responsible for this concentration of waves on three \"caustic\" points, which are a kind of focal line. This highly heterogeneous arrangement of the acoustic field forces the internal flow to adopt a particular structure, made up of one or two pairs of vortices. It is these vortices that enable efficient mixing within the drop.<\/p>\n

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Murmur gallery in a droplet. (A-B) trajectory of acoustic rays guided by the droplet surface. (C) Simulation of acoustic currents generated by murmur galleries. (\u00a9 IEMN - MSC - INSP)<\/p><\/div>\n<\/div>\n

References :<\/strong>
\nOn the influence of viscosity and caustics on acoustic streaming in sessile droplets: an experimental and a numerical study with a cost-effective method
\nA. Riaud, M. Baudoin, O. Bou Matar, J.-L. Thomas & P. Brunet,
\nJournal of Fluid Mechanics (July 2017)
\nDOI: https:\/\/doi.org\/10.1017\/jfm.2017.178<\/a><\/p><\/blockquote>\n

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Researcher contact :<\/strong>
\nAntoine Riaud<\/p>\n

INSIS communication contact :<\/strong>
\ninsis.communication@cnrs.fr<\/p>","protected":false},"excerpt":{"rendered":"

Acoustic waves can be used to control, agitate and mix fluids with extreme precision. Researchers from the Institut d'\u00e9lectronique, de micro\u00e9lectronique et de nanotechnologie, the Mati\u00e8re et syst\u00e8mes complexes laboratory and the Institut des nanosciences de Paris have explained how these waves can induce the formation of vortices on the scale of a drop of water. [...]<\/p>","protected":false},"author":2,"featured_media":23485,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[12],"tags":[],"class_list":["post-13724","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-news"],"_links":{"self":[{"href":"https:\/\/www.iemn.fr\/en\/wp-json\/wp\/v2\/posts\/13724","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.iemn.fr\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.iemn.fr\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.iemn.fr\/en\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.iemn.fr\/en\/wp-json\/wp\/v2\/comments?post=13724"}],"version-history":[{"count":0,"href":"https:\/\/www.iemn.fr\/en\/wp-json\/wp\/v2\/posts\/13724\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.iemn.fr\/en\/wp-json\/wp\/v2\/media\/23485"}],"wp:attachment":[{"href":"https:\/\/www.iemn.fr\/en\/wp-json\/wp\/v2\/media?parent=13724"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.iemn.fr\/en\/wp-json\/wp\/v2\/categories?post=13724"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.iemn.fr\/en\/wp-json\/wp\/v2\/tags?post=13724"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}