Kirigami-inspired parachutes with programmable reconfiguration

Abstract

The art of kirigami allows programming a sheet to deform into a particular manner with a pattern of cuts, endowing it with exotic mechanical properties and behaviours1–17. Here we program discs to deform into stably falling parachutes as they deploy under fluid–structure interaction. Parachutes are expensive and delicate to manufacture, which limits their use for humanitarian airdrops or drone delivery. Laser cutting a closed-loop kirigami pattern18 in a disc induces porosity and flexibility into an easily fabricated parachute. By performing wind tunnel testing and numerical simulations using a custom flow-induced reconfiguration model19, we develop a design tool to realize kirigami-inspired parachutes. Guided by these results, we fabricate parachutes from the centimetre to the metre scale and test them in realistic conditions. We show that at low load-to-area ratios, kirigami-inspired parachutes exhibit a comparable terminal velocity to conventional ones. However, unlike conventional parachutes that require a gliding angle for vertical stability20 and fall at random far from a target, our kirigami-inspired parachutes always fall near the target, regardless of their initial release angle. These kinds of parachutes could limit material losses during airdropping as well as decrease manufacturing costs and complexity. A thin planar disc designed with appropriately patterned cuts transforms itself, due to air flow effects, into an effective parachute exhibiting good positional stability, regardless of its initial orientation.