Instabilities and transitions in the deformation of a prismatic bubble

Various types of instabilities leading to topological changes were experimentally observed in the quasi-static uniaxial extension of a single prismatic bubble consisting of two parallel “vertical” films confined by a liquid pool and solid walls (two vertical and one horizontal wall). In one transition, under vertical extension, the bubble suddenly looses contact with the pool and a planar vertical film forms (horizontal pipe configuration). In another transition, under horizontal extension, the vertical films curve and eventually contact at one end originating a vertical pipe with a connected planar film. When the pipes are stretched in the direction of their triple film junction, the junction eventually curves and subsequently gives rise to new configurations geometrically similar to a keel and to a boot. We analyse these instabilities and transitions and predict the strains at which they occur. Instabilities of this type may be relevant in the deformation of three-dimensional foams.