Inflatable Kirigami Crawlers

Kirigami offers unique opportunities for guided morphing by leveraging the geometry of the cuts. Here, we present the design of an inflatable kirigami metamaterial structure by introducing staggered linear cut patterns into heat-sealable lightweight engineered textiles to achieve locomotion upon cyclic inflation and deflation. Inflatable air pouches often undergo symmetric bulging while contracting in length. We show that the accumulated compressive forces can uniformly break the symmetry in inflatable kirigami structures – air pouches with some sealed inner cuts – beyond a pressure threshold. This effect increases contraction compared to simple air pouches by two folds and triggers local rotation of the sealed edges that overlap and self-assemble into an architected surface with emerging scale-like features. Additionally, we harness pre-deformation to ensure the symmetry breaking is controllable upon actuation and avoid nonuniform morphing. As a result, the inflatable kirigami actuators exhibit a uniform, controlled contraction with asymmetric localized out-of-plane deformations. This process allows us to harness the geometric and material nonlinearities to imbue inflatable textile-based kirigami actuators with predictable locomotive functionalities. We thoroughly characterized the programmed deformations of these actuators and their impact on friction. We found that the kirigami actuators exhibit directional anisotropic friction properties when inflated, having higher friction coefficients against the direction of the movement, enabling them to move across surfaces with varying roughness. We further enhanced the functionality of inflatable kirigami actuators by introducing multiple channels and segments to create functional soft robotic prototypes with versatile locomotion capabilities.