Captive bubble nucleation, growth, and detachment on plastrons under reduced pressure

Reduced pressure is able to affect captive bubbles collectively rather than individually. The depressurization and repressurization of a submerged superhydrophobic (SH) surface was found here to produce a captive bubble that exhibited height changes but invariant contact angles and contact lines. In some instances during depressurization, the initial nucleated captive bubble could be smaller in volume, which attested to the stochastic manner in which the very small bubbles that appear on the plastron are able to utilize Ostwald's ripening to merge with the captive bubble. With a captive bubble initially dispensed on the plastron surface, the captive bubble was found to visibly increase in size with each depressurization and repressurization cycle. This indicated the tendency of the Ostwald's ripening process, present only during the depressurization process, to grow the captive bubble at the expense of the gaseous content available in the plastron layer. When depressurized further, the captive bubble was able to detach from the plastron surface with a high degree of perturbation, to the extent that it could occasionally result in the formation of smaller captive bubbles with no plastron, or a plastron that did not cover the entire SH surface.