Emergent Spinning and Orbital Motion in Clustered Wind-Assisted Flyers

Nature offers a rich diversity of wind-assisted flyers, ranging from snowflakes to dandelion seeds and fungal spores. Despite their differences in size, material, and aerodynamic regime, these systems share a common principle: when individual flyers aggregate into clusters, the resulting geometric asymmetry gives rise to emergent behaviors, e.g., spinning, orbital motion, and extended gliding. This cluster-induced aerodynamic asymmetry represents a general mechanism in passive aerial dispersers, yet it remains poorly understood and rarely studied in a controlled manner. Here, we present a physical model of a wind-assisted flyer capable of cluster-induced spinning. The flyers are designed with porous and laser-cut from office paper. A single flyer exhibits airborne stability due to the formation of vortex rings downstream. When two flyers form a cluster, the clustering handedness determines the spinning velocity. Computational simulations reveal that the torque difference induced by structural asymmetry plays a critical role in determining the mid-air motion. With experiments, we demonstrate peak autorotation efficiency at 5° angular mismatch between two flyers. Furthermore, we explore mid-air self-assembly of flyers driven by aerodynamic interactions, during which dynamic clustering and de-clustering behaviors are observed, yielding diverse spinning velocities. These findings offer new possibilities for programmable mid-air clustering motion.