A study of pre-programmed soft Kirigami deployables exhibiting multistability

We present fully soft bistable structures that morph from a planar form into pre-programmed 3D shapes. These deployables consist of trilayered composites with a central pre-stretched substrate layer sandwiched between two symmetrically placed unstretched layers on the top and the bottom. This strain mismatch leads to the buckling of the planar structure into a 3D configuration. Inspired by Kirigami, the outer layers are cut along specific patterns, which, coupled with the strain mismatch, control the final shape of the structure. We study the effect of the initial design parameters, such as material and geometric properties of the layers, Kirigami designs, and the initial pre-stretch on the final 3D shape through detailed experimental, numerical, and analytical studies. This analysis culminates in developing a machine learning-aided approach to deduce the required Kirigami design, initial pre-stretch, and size of the planar composite to achieve a specific target 3D shape. This inverse design algorithm and a highly simplified manufacturing process provide us with a platform for the rapid prototyping of fully soft multistable structures. Through this study, we successfully demonstrate the use of these Kirigami structures in creating a manual bistable soft gripper and an autonomous flytrap-inspired gripper robot. This opens up a wide arena of applications, from delicate wearable electronics to deployable aerospace structures.