In this paper, we study the dynamics of cylindrical armoured bubbles excited by mechanical vibrations. A step by step transition from cylindrical to spherical shape is reported as the intensity of the vibration is increased, leading to a reduction of the bubble surface and a dissemination of the excess particles. We demonstrate through energy balance that nonspherical armoured bubbles constitute a metastable state. The vibration instills the activation energy necessary for the bubble to return to its least energetic stable state: a spherical armoured bubble. At this point, particle desorption can only be achieved through higher amplitude of excitation required to overcome capillary retention forces. Nonspherical armoured bubbles open perspectives for tailored localized particle dissemination with limited excitation power.
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http://dx.doi.org/10.1039/c7sm00097a | DOI Listing |
Soft Matter
May 2021
Faculty of Physics, Adam Mickiewicz University, Uniwersytetu Poznańskiego 2, 61-614 Poznań, Poland. and PoreLab, The Njord Centre, Department of Physics, University of Oslo, Blindern, N-0316 Oslo, Norway.
Droplets covered with densely packed solid particles, often called Pickering droplets, are used in a variety of fundamental studies and practical applications. For many applications, it is essential to understand the mechanics of such particle-laden droplets subjected to external stresses. Several research groups have studied theoretically and experimentally the deformation, relaxation, rotation, and stability of Pickering droplets.
View Article and Find Full Text PDFProc Natl Acad Sci U S A
September 2017
Department of Materials, ETH Zürich, CH-8093 Zürich, Switzerland;
A strategy to halt dissolution of particle-coated air bubbles in water based on interfacial rheology design is presented. Whereas previously a dense monolayer was believed to be required for such an "armored bubble" to resist dissolution, in fact engineering a 2D yield stress interface suffices to achieve such performance at submonolayer particle coverages. We use a suite of interfacial rheology techniques to characterize spherical and ellipsoidal particles at an air-water interface as a function of surface coverage.
View Article and Find Full Text PDFSoft Matter
May 2017
Univ. Lille, CNRS, Centrale Lille, ISEN, Univ. Valenciennes, UMR 8520, International Laboratory LEMAC/LICS - IEMN, F-59000 Lille, France.
In this paper, we study the dynamics of cylindrical armoured bubbles excited by mechanical vibrations. A step by step transition from cylindrical to spherical shape is reported as the intensity of the vibration is increased, leading to a reduction of the bubble surface and a dissemination of the excess particles. We demonstrate through energy balance that nonspherical armoured bubbles constitute a metastable state.
View Article and Find Full Text PDFSoft Matter
December 2014
International Laboratory LEMAC/LICS, IEMN, UMR CNRS 8520, Université Lille 1, Avenue Poincaré, 59652 Villeneuve d'Ascq, France.
In this paper, we report on the strongly modified dynamics of a liquid finger pushed inside a capillary tube, when partially wettable particles are lying on the walls. Particles promote the appearance of new regimes and enable the tailored synthesis of bubbles encapsulated in a monolayer of particles (so-called "armoured bubbles"). This remarkable behavior arises due to the collection of particles at the air-liquid interface, which modify the global energy balance and stabilize the interface.
View Article and Find Full Text PDFLangmuir
April 2012
Université de Lyon, Univ. Lyon 1, CPE Lyon, CNRS UMR5265, Laboratoire de Chimie, Catalyse, Polymères et Procédés (C2P2), LCPP team, 43 Bd du 11 Novembre 1918, 69616 Villeurbanne, France.
Stable methyl methacrylate (MMA) miniemulsions were successfully prepared using for the first time cerium oxide (CeO(2)) nanoparticles as solid stabilizers in the absence of any molecular surfactant. The interaction between MMA droplets and CeO(2) nanoparticles was induced by the use of methacrylic acid (MAA) as a comonomer. Both MAA and CeO(2) contents played a key role on the diameter and the stability of the droplets formed during the emulsification step.
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