JAMJams: Jagged Anisotropic Mechanically Jamming Appendages for Robot Locomotion

Laminate structures with nonlinear stiffness and controllable bending properties have applications as appendages for soft robot locomotion. In this paper, we develop a laminate-based structure for soft-robotics called Jagged Anisotropic Mechanically Jamming (JAMJam) sheets. JAMJam sheets are comprised of two flexible layers with rigid anisotropic structures 3D printed onto the flexible surface. The rigid elements between the flexible sheets are displaced longitudinally as the sheets are bent and when the elements make contact the bending stiffness increases and the resulting curvature can be controlled. In this work we study a simple example of a JAMJam sheet consisting of controllable bending curvature which is anisotropic along the forward and backward directions. We characterize the JAMJam behavior through force-displacement measurements and we implement the JAMJam sheets as appendages in a swimming robot. We compare the JAMJam mechanics under representative limb motions for a swimming robot and compare two types of appendages. Lastly, a robot utilizing the appendages is designed for shallow-water environments, which can both walk while semi-submerged at up to 9 cm/s and swim at 7.2 cm/s, The robot is capable of locomotion in both turf and sandy laboratory conditions, and can traverse over obstacles in its path.