Granular Particles with Circular Motions and Novel Shapes on the Vibration Stage

Abstract

Self-propelled active particles, such as fish, birds, bacteria, and active colloidal and granular particles, exhibit rich collective behavior and provide a new class of systems for the study of non-equilibrium physics. In this work, we discover that a certain type of grass seed exhibits novel spinning and orbital rotational motions under vibration. We shape particles with various sizes and masses through 3D printing and study their effects on active rotations. The seeds provide a powerful platform to verify simulation predictions on rotational active particles. We study the motions of seeds in various obstacle arrays and find that they agree with the simulation result, including caged motions and  superdiffusion under slightly different obstacle environments.  The second part is about the C-shaped granular particles. Among various novel shaped particles we explored, C-shaped particles can spontaneously connect into complex networks and thus belongs to a novel type of granular system with unusual structures and rheological properties. We study the cluster formation process of C-shaped particles with various opening angles on a vibration stage and compare the results with the simulation.  We discover and study the percolation transition for entanglement of particles.