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An antibubble is a liquid droplet wrapped by a thin layer of gas, inside a bulk liquid usually of the same composition. The lifetime of an antibubble is governed by the drainage of the gas between the two liquid-gas interfaces populated by surfactants. Depending on the relative magnitude of surface viscosity and elastic moduli, which directly depend on or are determined by the nature of surfactants, the lifetime of an antibubble may vary a lot, from few seconds to few minutes. While such a difference can be predicted with models that include the role of interfacial properties, they were not observed experimentally in previous studies, due to important sources of dispersion. In this review, the main sources of dispersion are identified, such as (i) the initial amount of gas embedded in the antibubble, (ii) the level of saturation of gas in the bulk liquid, (iii) the presence of dust particles (<0.5 μm) in the gas, and (iv) three-dimensional flow effects. By accounting for these various effects, we obtain a coherent view on the lifetime of an antibubble, as a function of its radius and the surface rheology, with excellent consistency between experiments and modeling. Results thus demonstrate that controlling the size and lifetime of antibubbles is achievable. Unlabelled Image • Surface elasticity plays a dominant role in antibubble lifetime for small surfactant molecules; • Above a threshold, the lifetime is almost independent on the bulk concentration of surfactants; • Accounting precisely for gas dissolution in the liquid is crucial to obtain qualitative agreement with modeling. • The antibubble lifetime increases with the radius; • In controlled conditions, the antibubble collapse is shown to be a deterministic process; [ABSTRACT FROM AUTHOR]

Abstract: A theoretical study of the phenomena, occurring in an adsorbed layer, subject to small dilatational perturbations was carried out. Two main processes, provoked by the perturbations (surface reaction and surfactant transport onto the surface) were considered. The reaction was described by means of the reaction coordinate. The derived general rheological equation for insoluble surfactants, gave as limiting cases Voight and Maxwell type equations for fast and slow reactions, respectively. Expressions for all characteristics of the process (surface elasticity, reaction elasticity, reaction relaxation time and dilatational surface viscosity) were obtained. The obtained generalized rheological equation for reactions involving soluble surfactants is a dynamic analog of Gibbs adsorption isotherms for a multi-component system with surface reaction, since similarly to Gibbs equation it relates the surface stress only to surface variables. It gives as limiting cases generalized forms for soluble surfactants of Voight and Maxwell equations. All new rheological equations were analyzed for deformations with constant rate and periodic oscillations and they were applied to three simple surface reactions (monomolecular with one product, dimerization and association). The mass transfer was analyzed initially in the absence of surface reaction. In this system the surface stress is purely elastic, but it was shown that if the adsorption perturbation is small, regardless of the type of surface perturbation and the mechanism of adsorption, the process of mass transport always obeys a Maxwell type rheological equation. For all considered processes surface viscosities were defined, but they were called “apparent”, because they stem from diffusion, rather than from interaction between the surfactant molecules and they depend not only on surface parameters, but also on the geometry of the system. The often used in the literature correlations between the lifetime of emulsions and foams and the imaginary elasticity were analyzed. It was shown that this approach lacks serious scientific foundations and could lead to erroneous conclusions. Finally, the problem for the coupling of the surfactant diffusion with the chemical reaction was analyzed and it was demonstrated on a simple example how it could be tackled. [Copyright &y& Elsevier]