A. Rafsanjani, Y. Zhang, B. Liu, S. M. Rubinstein, and K. Bertoldi. 2/21/2018. “
Kirigami skins make a simple soft actuator crawl.” Science Robotics, 3, 15, Pp. eaar7555.
Publisher's VersionAbstractBioinspired soft machines made of highly deformable materials are enabling a variety of innovative applications, yet their locomotion typically requires several actuators that are independently activated. We harnessed kirigami principles to significantly enhance the crawling capability of a soft actuator. We designed highly stretchable kirigami surfaces in which mechanical instabilities induce a transformation from flat sheets to 3D-textured surfaces akin to the scaled skin of snakes. First, we showed that this transformation was accompanied by a dramatic change in the frictional properties of the surfaces. Then, we demonstrated that, when wrapped around an extending soft actuator, the buckling-induced directional frictional properties of these surfaces enabled the system to efficiently crawl.
Featured on Science Robotics Cover, Harvard SEAS News, Scientific American, Wired, The Verge, IEEE Spectrum, Digital Trends, NewsWeek, LA Times, DailyMail, BBC Click
X. Shang, L. Liu, A. Rafsanjani, and D. Pasini. 2/14/2018. “
Durable Bistable Auxetics Made of Rigid Solids.” Journal of Materials Research, Focus Issue: Architected Materials, 33, 3, Pp. 300-308.
Publisher's VersionAbstractBistable Auxetic Metamaterials (BAMs) are a class of monolithic perforated periodic structures with negative Poisson’s ratio. Under tension, a BAM can expand and reach a second state of equilibrium through a globally large shape transformation that is ensured by the flexibility of its elastomeric base material. However, if made from a rigid polymer, or metal, BAM ceases to function due to the inevitable rupture of its ligaments. The goal of this work is to extend the unique functionality of the original kirigami architecture of BAM to a rigid solid base material. We use experiments and numerical simulations to assess performance, bistability and durability of rigid BAMs at 10,000 cycles. Geometric maps are presented to elucidate the role of the main descriptors of BAM architecture. The proposed design enables the realization of BAM from a large palette of materials, including elastic-perfectly plastic materials and potentially brittle materials.