Experimental study of the bursting of inviscid bubbles

The rupture dynamics of smectic bubbles supported on a capillary is studied by means of microsecond photography, and properties of the retracting films are quantitatively analyzed. The film material collects in a moving rim that follows the sphere shape. A constant edge velocity is reached instantly; it is proportional to the inverse square root of the film thickness and in reasonable quantitative agreement with model predictions. The rim constitution for thin and thick films differs. In thin (submicrometer) films, the rim undulates and decomposes into single droplets, while for thick films, it remains compact and straight, and a brim is formed. During rupture, the initial film thickness increases globally, despite the smectic layer structure. Then, the recession of the film edge is accompanied by undulations of the bubble surface in the micrometer range.