Shape change through elastic phase-separation

We observed an unexpeted instability in an architected elastomer plate that includes an internal network of airways (”baromorph”).
Although we had designed these systems to undergo homogeneous in-plane expansion, we find that they sometimes shift fromt a planar shape into a very unusual three-dimensional shape.
We interpret this instability as buckling induced by the mechanical analogue of phase-separation, similar to that which appear when inflating linear balloon used for scultping.