  We report a phenomenon of phase separation that relates in many aspects to
Yves Couder's work: an inflatable architectured elastomer plate, expected to
expand homogeneously in its plane, buckles instead widely out-of-plane into
very complex shape when internal pressure is applied. We show that this
morphogenetic pattern formation is due to a two-dimensional elastic phase
separation, which induces incompatible patchy non-Euclidean reference metric.
