Shearigami : self-folding via shear deformation

Abstract

Origami and kirigami have become foundations for programmable sheet materials that fold along flexible creases. However, since they are originated from folded paper that allows no in-plane sheet deformation, they suffer from limited folding energy arising from narrow creases, and large varieties of crease patterns are completely non-foldable due to over-constraint. Herein, a new strategy that breaks the limitations of the conventional crease-induced folding kinematics by leveraging a folding effect from in-plane shear deformation of the sheet is reported, and it is referred to as shearigami. It is shown that shearigami extends the realm of foldable structures to include the strictly non-foldable origami patterns such as degree-3 vertices, and the sheet-stored self-folding energy outperforms the crease-stored energy by a potentially two orders of magnitude. Shearigami also inherits the mathematical framework of paper folding and provides a unified view that regards origami and kirigami as two special cases. Herein, self-folding shearigami models are experimentally demonstrated based on previously non-foldable patterns, including artificial muscles with rapid shear-induced extension. The way is paved toward active structures and architectured materials with design freedom and self-folding capabilities beyond origami and kirigami.