Hydrodynamic Boundary Conditions and Dynamic Forces between Bubbles and Surfaces

Manor, Ofer; Vakarelski, Ivan U.; Tang, Xiaosong; O’Shea, S. J.; Stevens, Geoffrey W.; Grieser, Franz; Dagastine, Raymond R.; Chan, Derek Y. C.

doi:10.1103/physrevlett.101.024501

Cited by 116 publications

(185 citation statements)

References 35 publications

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“…The barrier ring shape has to be connected to the dimple center. At the center, the dimple shape is approximatively parabolic and thus writes: (27) where (r d − δ r) is defined in Fig. 9 as the radius for which the parabolic shape h d is null.…”

Section: -14 | 11mentioning

confidence: 99%

“…Therefore, not only the expected liquid/liquid interface (β = 2) boundary condition is not obtained, but the solid/liquid boundary condition does not apply neither. In the literature, the tangentially immobile boundary condition (β = 1) was found to apply to different fluid interfaces such as gas bubble/water 1,27 or mercury/water. 5,28 No reports of β values smaller than 1 can be found, to the best of our knowledge.…”

Section: Three Drainage Regimesmentioning

confidence: 99%

“…When surface-active molecules (either added surfactants or contaminants) are present, even in small quantities, they accumulate at the interface and Marangoni stresses may develop, rendering the interface tangentially immobile, as observed in the literature, where a variation of interfacial tension as small as 0.1 mN.m −1 along an interface is sufficient to explain the tangentially immobile boundary condition. 27,29 In our case, an estimate of the interfacial tension variations resulting in a no-slip boundary condition is provided by balancing the Marangoni stress ∂ γ/∂ r ∼ ∆γ/δ r with the viscous tangential stress at the interface, where δ r is the radial width over which the dissipation occurs. It can be estimated from the This value is ten times smaller than the decrease over time of the oil/water interfacial tension measured by the tensiometer, validating the onset of Marangoni stresses at the oil/water interface.…”

Section: Three Drainage Regimesmentioning

confidence: 99%

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Water film squeezed between oil and solid: drainage towards stabilization by disjoining pressure

et al. 2017

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The spontaneous drainage of aqueous solutions of salt squeezed between an oil drop and a glass surface is studied experimentally. The thickness profile of the film is measured in space and time by reflection interference microscopy. As the film thins down, three regimes are identified: a capillary dominated regime, a mixed capillary and disjoining pressure regime, and a disjoining pressure dominated regime. These regimes are modeled within the lubrication approximation, and the role of the disjoining pressure is precisely investigated in the limit of thicknesses smaller than the range of electrostatic interactions. We derive simple analytical laws describing the drainage dynamics, thus providing tools to uncouple the effect of the film geometry from the effects of the disjoining or capillary pressures.

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Section: -14 | 11mentioning

confidence: 99%

Section: Three Drainage Regimesmentioning

confidence: 99%

Section: Three Drainage Regimesmentioning

confidence: 99%

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Water film squeezed between oil and solid: drainage towards stabilization by disjoining pressure

et al. 2017

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“…Although measurements of the terminal velocities of rising bubbles (21,22) show that the fully mobile boundary condition is applicable in ultraclean water, such degree of cleanliness is impractical to achieve in our experiments. Quantitative estimates suggest that a surface concentration of surface-active species that reduces the interfacial tension by ∼1 mN∕m would be sufficient to cause bubbles to exhibit the no-slip boundary condition (23).…”

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confidence: 99%

Dynamic interactions between microbubbles in water

Vakarelski

Manica²,

Tang³

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

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The interaction between moving bubbles, vapor voids in liquid, can arguably represent the simplest dynamical system in continuum mechanics as only a liquid and its vapor phase are involved. Surprisingly, and perhaps because of the ephemeral nature of bubbles, there has been no direct measurement of the time-dependent force between colliding bubbles which probes the effects of surface deformations and hydrodynamic flow on length scales down to nanometers. Using ultrasonically generated microbubbles (∼100 μm size) that have been accurately positioned in an atomic force microscope, we have made direct measurements of the force between two bubbles in water under controlled collision conditions that are similar to Brownian particles in solution. The experimental results together with detailed modeling reveal the nature of hydrodynamic boundary conditions at the air/water interface, the importance of the coupling of hydrodynamic flow, attractive van der Waals-Lifshitz forces, and bubble deformation in determining the conditions and mechanisms that lead to bubble coalescence. The observed behavior differs from intuitions gained from previous studies conducted using rigid particles. These direct force measurements reveal no specific ion effects at high ionic strengths or any special role of thermal fluctuations in film thickness in triggering the onset of bubble coalescence.bubble collision | colloidal forces | hydrodynamic interaction | soft matter | thin films B ubble dynamics has attracted scientific interest since the time of Leonardo da Vinci (1), yet the observation that some simple salts can prevent bubble coalescence at high concentrations whereas others cannot remains unexplained even after over a decade of systematic study (2). In themselves, bubble-bubble interactions are very important because they feature in diverse situations, from the basis of the bends in deep-sea divers, to the development of effective ultrasonic imaging contrast agents, through to enhancing the quality of champagne. However, the delicate and ephemeral nature of bubbles poses significant technical challenges to the precise quantification of the force-displacement characteristics of bubble collisions.As a vapor phase in a liquid, the interaction between bubbles should be amenable to a simple explanation in terms of basic physical and chemical principles. A detailed understanding of the interaction between moving bubbles can provide the foundation on which to study the fundamental coupling between forces and deformations that defines the dynamic interaction on the nanoscale between soft-matter materials, such as bubbles, drops, emulsions, biological cells, soft tissues, and gels. Here we report direct measurements of the dynamic force between two deformable microbubbles in water under a variety of accurately controlled collision protocols. The typical collision velocities are in the regime of Brownian particles of comparable dimensions. The experimental conditions are such that only attractive van der Waals-Lifshitz forces and hydrodynami...

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“…deformable mercury drop in aqueous solution against a mica plate 1,2 ; optical interference to visualize the dynamic stability of glycerol or water in silicone oil systems 3 ; the atomic force microscope to measure dynamic forces between oil emulsion drops moving at typical Brownian speeds in aqueous electrolyte [4][5][6] and forces between bubbles and a solid substrate 7 ; and the four-roll mill to manipulate interacting drops 8 .…”

mentioning

confidence: 99%