Growth of a bubble cloud in CO₂-saturated water under microgravity

Abstract

The diffusion-driven growth of a dense cloud of bubbles immersed in a gas-supersaturated liquid is a problem that finds applications in several modern technologies such as solvent-exchange microreactors, nanotechnology or the manufacturing of foamy materials. However, under Earth's gravity conditions, these dynamics can only be observed for a very limited time if the cloud is not attached to a surface, due to the action of buoyancy, i.e. of gravity effects. Here, we present experimental observations of the time evolution of dense bubble clouds growing in CO 2 -supersaturated water in microgravity conditions. We report the existence of three regimes where the bubble cloud exhibits different growth rates. At short times, each bubble grows independently following the Epstein-Plesset equation. Later on, bubbles start to interact with each other and their growth rate diminishes as they compete for the available CO 2 . When this happens, the growth rate slows down. This occurs earlier the deeper the bubble is in the cloud. Finally, at long times, only those bubbles on the husk continue growing. These regimes may be qualitatively described by a mathematical model where each individual bubble grows in the presence of a constellation of point mass sinks. Despite the model being only valid for dilute bubble clouds, its predictions are consistent with the experimental observations, even though the bubble clouds we observe are rather dense.

3D Bioprinting in Microgravity: Opportunities, Challenges, and Possible Applications in Space

“…Regulating such parameters relies on heat and mass transfer, liquid-gas interface, bubbling, and mixing. In microgravitational environments, all such physical behavior is affected, [65,[157][158][159] thus rendering it impossible to directly transfer tools from Earth for space. While none of the available common cell culture bioreactors [160] can fit the constraints imposed by microgravity and space, several dedicated equipment and installations have been deployed to the ISS to provide an adequate cell culture environment.…”

Bubble-laden thermals in supersaturated water

“…The fact that the volume of the bubbles inside the thermal grows in a similar fashion as for isolated bubbles is somewhat surprising at first sight. One could expect the bubbles inside the thermal to compete for the available CO, resulting in gas depletion and slower growth rates, as is the case for quasi-static bubble clouds (Vega-Martínez, Rodríguez-Rodríguez & van der Meer 2020). However, the mixing induced by the vortical motion of the thermal seems to replenish the dissolved CO gas content within.…”

Nonuniform Collective Dissolution of Bubbles in Regular Pore Networks

“…Notably, a densely populated cluster of bubbles with initial uniform size can produce a characteristic dissolution pattern, where bubbles on the outer layer dissolve faster than those on the inner layers (Weijs et al 2012;Laghezza et al 2016). In such cases, the interplay between Ostwald ripening and diffusive shielding may give rise to situations where bubbles undergo periods of growth and dissolution alternately, and layers no longer dissolve regularly (Michelin et al 2018;Vega-Martínez et al 2020).…”