Particle Sweeping and Collection by Active and Living Filaments

Biological and robotic systems often operate in confined environments where materials must be gathered without centralized control. Inspired by the effective collection strategies of aquatic worms (Lumbriculus variegatus and Tubifex tubifex), we investigate how active filaments autonomously aggregate dispersed non-Brownian passive particles. We study this process across four platforms: living worms, a robotic chain, Brownian dynamics simulations of active polymers, and a coarse-grained toy model. We show that aggregation emerges from repeated contact and body deformation—effectively, a sweeping or brooming motion—and demonstrate that clustering dynamics are governed by filament length and bending stiffness. Across systems, particle gathering follows a shared aggregation-fragmentation process, where the steady-state cluster size approximately follows a quadratic increase with the effective width of the path cleared by the filament W relative to the domain size D. This scaling provides a minimal geometric baseline for comparison across active filamentous systems. We find that filament flexibility modulates W, enabling more flexible filaments to sweep larger areas and collect more particles. These results establish a unifying framework for understanding how shape and flexibility influence transport and organization in active filament systems and filamentous robots.