Tenjamity—Tensional Jamming Based Self-Deployable Mechanical Metamaterials

Recent advancements in robotics demand materials that can adapt dynamically to varying conditions, offering both flexibility and robustness. However, designing materials that possess self-deployment and post-deployment continuously tunable mechanical properties remains a challenge, notwithstanding its importance. Here, we introduce a class of mechanical metamaterials utilizing the contracting-cord particle jamming (CCPJ) mechanism, designed for robotic systems requiring adaptive morphology, stiffness, and damping. Our metamaterials feature networked chains with beads threaded with interlocking conical concavo-convex interfaces along contracting actuators, inspired by push puppets. This design allows for precise self-deployability and extensive tunability in stiffness and damping within three-dimensional metamaterials. In their slack state, these networks conform to various shapes, but upon actuation, they self-assemble into predetermined configurations. Further contraction dynamically tunes the mechanical properties through particle jamming, maintaining structural integrity with minimal changes.<br/><br/>Experimental and numerical exploration of CCPJ-based beams reveals that varying applied contracting tension induces particle jamming within engineered beads, significantly enhancing mechanical properties. For example, a self-deployed beam in a bending-dominated configuration achieves over 35 times increased stiffness and a 52% change in damping under 120 N of external tension. Adjusting the beads' conical angle influences self-deployability and mechanical tunability due to geometric and frictional nonlinearities. We further characterize CCPJ-based cubic unit cells, composed of identical unit beams, demonstrating the feasibility of constructing various configurations while retaining advantageous attributes. Comparisons between bending-dominated and stretching-dominated cells confirm a preference for bending-dominated structures, with a cubic cell showing a 32-fold stiffness change and a 40% reduction in damping.<br/><br/>To illustrate the practical application, we integrate actuators such as electrically-driven thermal artificial muscles and motor-driven cables, enabling rapid, on-demand self-deployment, self-retraction, and stiffness tuning in larger-scale metamaterials. This research introduces a new class of materials capable of adapting in situ, paving the way for advanced applications in soft robotics, reconfigurable architectures, and space engineering.