Buckling morphology evolution of thin films on non-linear elastic substrates

Organisms have evolved a strain limiting mechanism, reflected as a non-linear elastic constitutive, to prevent large deformations from threatening soft tissue integrity. Compared with linear elastic substrates, the wrinkle of films on non-linear elastic substrates has received less attention. In this article, a unique wrinkle evolution of the film-substrate system with a J-shaped non-linear stress-strain relation is reported. The result shows that a concave hexagonal array pattern is formed with the shrinkage strain of the film-substrate systems developing. As the interconnection of hexagonal arrays, a unit cell ridge network appears with properties such as chirality and helix. The subparagraph maze pattern formed with high compression is mainly composed of special single-cell ridge networks such as spiral single cores, chiral double cores, and combined multi-cores. This evolutionary model is highly consistent with the results of experiments, and it also predicts wrinkle morphology that has not yet been reported. These findings can serve as a novel explanation for the surface wrinkle of biological soft tissue, as well as provide references for the preparation of artificial biomaterials and programmable soft matter.