Twist-coupled Kirigami cells and mechanisms

Abstract

Manipulation of thin sheets by folding and cutting offers opportunity to engineer structures with novel mechanical properties, and to prescribe complex force–displacement relationships via material elasticity in combination with the trajectory imposed by the fold pattern. Here we study the mechanics of a cellular Kirigami that rotates and buckles upon compression, presenting an example of a design strategy that we call ”flexigami”. The addition of diagonal cuts to an equivalent closed cell permits the cell to collapse reversibly without incurring significant tensile strains in its panels. Using finite-element modeling and experiments we show how the mechanical behavior of the cell is governed by the coupled rigidity of the panels and hinges and we design cells to achieve reversible force response ranging from smooth mono-stability to sharp bi-stability. We then demonstrate the cell-based construction of laminates with multi-stable behavior and a rotary-linear boom actuator, as well as self-deploying cells with shape memory alloy hinges. Advanced digital fabrication methods can enable the realization of this and other so-called flexigami designs that derive their overall mechanics from fold and panel elasticity, for applications including deployable structures, soft robotics and medical devices.