Wetting of ring-shaped surface domains

Wetting of ring-shaped surface domains is studied both theoretically and experimentally. The liquid channels covering these domains exhibit a volume-induced morphological transition from a homogeneous to a bulge state. The continuous symmetry of the low-volume channels is spontaneously broken by the transition to the high-volume regime. Therefore, an angular displacement of the bulge does not cost any (free) energy and the corresponding interface deformation represents a Goldstone boson which should be observable for domains in the micrometer regime.