Programmable Collective Behavior via Entangled Granular Metamaterials

Entanglement between geometrically complex grains enables emergent collective behavior in granular metamaterials. We introduce a design framework for creating grains with tunable geometric complexity and demonstrate how their interlocking interactions govern packing, entanglement, and disentanglement dynamics. Using molecular dynamics simulations and experiments, we identify quantitative relationships linking grain geometry, packing fraction, and disentanglement rate. Grains with higher geometric complexity exhibit stronger and more persistent entanglement, leading to emergent mechanical stability and cohesive collective response. Leveraging these properties, we develop a magnetically actuated granular metamaterial capable of entangling with and retrieving tangle-prone targets such as fibers, nets, and soft natural materials. This entanglement-based approach offers a new paradigm for material design and robotic manipulation, embedding functionality directly into the geometry of the grains.