Soft Kirigami Composite that Deploys into Pre-programmed Shapes*

We report soft composites with multiple layers that morph from a planar form into pre-programmed 3D shapes. We start with bilayered composites wherein a pre-stretch is applied to a substrate layer; an unstretched layer is then attached on top of the same. The applied pre-stretch leads to a strain mismatch between the two layers, which forces the planar composite structure to assume a 3D shape when the load is released. Inspired by kirigami, the top layer is cut along specific patterns that ultimately determine the shape of the final 3D structure. We focus on the kirigami pattern that leads to a hemispherical 3D shape. Furthermore, we compare experiments with finite element simulations. We study the effect of various parameters, namely, kirigami pattern, amount of strain mismatch, and geometrical and material properties of the layers, on the shape of the final structure. This project is an unprecedented attempt at form-finding in mechanics through the combination of strain mismatch and kirigami patterning. Notably, the entire fabrication process of the 3D structure takes place on a 2D plane. Due to this ease of manufacturing, soft kirigami composites can find application in wearable electronics, deployable aerospace structures, and soft robotics.