Levitation-free vibrated droplets: resonant oscillations of liquid marbles

McHale, G., Elliott, S.J., Newton, M.I. ORCID: 0000-0003-4231-1002, Herbertson, D.L. and Esmer, K., 2009. Levitation-free vibrated droplets: resonant oscillations of liquid marbles. Langmuir, 25 (1), pp. 529-533. ISSN 0743-7463

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Abstract

A spherical conducting droplet in an alternating electric field is known to undergo shape oscillations. When the droplet is supported by a substrate, the shape is no longer a complete sphere, but shape resonances are still observed. To obtain a completely spherical droplet, some kind of levitation is needed, unless the droplet is in microgravity, and this has previously been provided by gas films or magnetic or other external forces. In this work, we report observations of shape oscillations of a hydrophobic-powder-coated droplet of water. A droplet of water rolled on a hydrophobic powder self-coats such that the water becomes encapsulated as a liquid marble. When the powder is a spherical hydrophobic grain with a contact angle greater than 90°, it adheres to the solid−water interface with more than half of its diameter projecting from the liquid, thus ensuring the encapsulated water does not come into contact with any substrate. These liquid marbles are highly mobile and can be regarded as completely nonwetting droplets possessing contact angles of 180°. In this work, we show that they also provide a new mechanism equivalent to levitating droplets and provide droplets with small contact areas and completely mobile contact lines for studies of shape oscillations. Liquid marbles were created using hydrophobic lycopodium and droplets of water containing potassium chloride and were excited into motion using an electrowetting-on-dielectric configuration with applied frequency swept from 1 to 250 Hz.

Item Type: Journal article
Publication Title: Langmuir
Creators: McHale, G., Elliott, S.J., Newton, M.I., Herbertson, D.L. and Esmer, K.
Publisher: American Chemical Society
Date: 2009
Volume: 25
Number: 1
ISSN: 0743-7463
Identifiers:
NumberType
10.1021/la803016fDOI
Rights: Reprinted with permission from MCHALE, G., ELLIOTT, S.J., NEWTON, M.I., HERBERTSON, D.L. and ESMER, K., 2009. Levitation-free vibrated droplets: resonant oscillations of liquid marbles. Langmuir, 25 (1), pp. 529-533. Copyright 2009 American Chemical Society.
Divisions: Schools > School of Science and Technology
Depositing User: EPrints Services
Date Added: 09 Oct 2015 09:53
Last Modified: 09 Jun 2017 13:13
URI: http://irep.ntu.ac.uk/id/eprint/4439

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