Stability of big surface bubbles: impact of evaporation and bubble size

Abstract

At the end of their life, surface bubbles burst and emit aerosols, which drastically impact exchanges in liquid as well as in pathogens or flavors with the surrounding atmosphere. This exchange depends on the thickness of the liquid film and is thus linked to the bubble drainage dynamics and to their lifetime. In this article, we propose to explore both feature for big surface bubbles depending on their size. We also explore the impact of atmospheric humidity by a careful control and systematic variation of the relative humidity. We show that a model including both capillary and gravity driven drainage gives a prediction of the bubble lifetime in line with experiments provided convection is taken into account to calculate the evaporation rate. arXiv:1907.09734v1 [cond-mat.soft]

Lifetime of a single bubble on the surface of a water and ethanol bath

“…On the contrary, films of bubbles stabilized by amphiphilic molecules adsorbed at the film interface are barely subject to drainage since, in this case, Marangoni stresses balance the gravitational or capillary stresses. This induces much longer lifetimes, for which mass loss induced by evaporation is no longer negligible [8,9]. Using the framework developed in [8] and [9], assuming that this is the liquid evaporation that limits the maximum lifetime accessible to very stable bubbles [i.e., evaporation of a film of critical thickness for which both film thinning phenomena induced by capillary drainage (lower and lower over time) and evaporation are of the same order (constant over time)], one can estimate the bubble lifetime…”

“…In this context, the lifetime of a bubble on the surface of a liquid is an important parameter: the longer the lifetime, the more the film is drained and the finer the aerosol formed. Overall, the life of a bubble at an interface is the sum of the characteristic times of drainage, evaporation, hole initiation, and bursting [5][6][7][8][9]. It therefore subtly depends on various parameters such as the size of the bubble, the viscosity of the liquid, and the presence of surfactant molecules [1,5,7,[9][10][11][12][13].…”

Fragmentation versus Cohesion

“…However, due to their enhanced lifetime, it is eventually evaporation that governs their thinning, thus also dramatically decreasing the cap thickness at burst (Champougny et al 2018). Miguet et al (2020) have nevertheless underlined the importance, in order to lock to this final regime, of working with surfactants exempt from impurities, these triggering the classical Marangoni piercing mechanism described above.…”

The Life of a Surface Bubble

“…This equation is obtained by integrating Equation (7) using the flow velocity given by Equation (9). For big bubbles, this lifetime actually overestimates the actual lifetime by up to 10% since an additional gravity-driven drainage needs to be taken into account [37]. Doing so, the experimental data are very well predicted by the thinning rate (Figure 8c).…”

“…(c) Comparison of the thickness of the film at the top of bubble with the model proposed by Lhuissier[21] (dashed lines) complemented by a gravity-driven drainage (solid lines) for bubbles of different radius R. The inset represents a sketch of the pinch in the vicinity of the meniscus, close to the bath. Figure adapted from reference[37].…”