Surface wrinkling patterns on a core-shell soft sphere.

The three-dimensional patterns of surface wrinkling on a core-shell soft sphere are investigated through buckling and postbuckling analyses under differential tissue growth or shrinkage. With increasing deformation, the sphere first exhibits a buckyball-like wrinkling pattern and then undergoes a wrinkle-to-fold transition into labyrinth folded patterns, in agreement with experimental observations. This transition involves dynamic movement, rotation, and coalescence of polygons formed during the initial buckling.