Metamaterial soft snake robot for rectilinear locomotion

Snake locomotion has served as a source of inspiration for the development of slender robots capable of maneuvering through challenging environments. Within the array of crawling gaits exhibited by snakes, rectilinear locomotion stands out as a prominent method for navigating confined and narrow spaces. In this mode of movement, snakes propel themselves in a straight line by generating a sequential series of waves through the contraction and extension of their muscles, making effective use of their flexible body and the anisotropic friction properties of their ventral skin. To translate this biological principle into robotic systems, there is a need for a framework that seamlessly integrates body deformation with surface interactions. In this study, we bridge this crucial gap by drawing inspiration from three fundamental elements of snake anatomy: the flexible rib structure, the muscular system, and the anisotropic compliant skin. To achieve this objective, we employ flexible mechanical metamaterials comprised of repetitive building blocks, which enable the creation of an origami-like backbone and a kirigami-inspired wrapping to mimic the snake's flexible rib and skin, respectively. These components are activated through an integrated tendon-driven actuation system. We provide a comprehensive account of the bioinspired design and fabrication process, followed by a thorough characterization of our snake robot's performance across various surfaces. The proposed design introduces a scalable multifunctional soft robotic snake module tailored for rectilinear locomotion, showcasing the potential for real-world applications in challenging and confined environments.