Can sheet cuttings (kirigami) control flow-induced deformation?*

Kirigami, which is the Japanese art of paper cutting, has emerged as a promising design tool to produce surfaces morphing into sophisticated shapes and with programmable mechanical properties. Those features can be tuned through the network of cuts, offering levers to control the way the object deforms in a fluid flow. Here, we study the deformation a kirigami sheet in a water cross-flow. Under fluid loading, the structure expands through the opening of pores that let fluid through, thus acting as a poro-elastic surface. We characterize experimentally and theoretically the relation between the cuts geometry and the resulting shape transformation. We show that the macroscopic morphing is dictated by interactions with fluid at the local scale of the pores, whose geometry changes in turns with the sheet elongation. Understanding those multi-scale couplings provides a novel control strategy for shape-shifting in flows through the reverse-engineering of cut motifs.