Topological mechanics of living worm blobs

Tangled filamentary objects are ubiquitous in biological and physical systems, from chromosomal DNA to turbulent vortex lines. Despite important recent progress, the interplay of topology, activity and elasticity in the context of many-body tangle interactions is not well understood. Here, we model California blackworms (Lumbriculus variegatus), which are known to slowly form tangles or blobs over minutes with their flexible bodies but untangle in milliseconds under stress. In this talk, we will develop a topological framework to understand the slow formation and fast separation of active tangles, combining elastic fiber simulations with a low-dimensional tangle representation. Using this model, we will describe the topological moves that guide tangle self-assembly and demonstrate that helical waves of alternating chirality, a characteristic dynamical feature of stressed, untangling worms, represent a possible unweaving mechanism that simplifies tangle topology. Our results illustrate the design principles underlying a self-assembling and disassembling tangle, and pave the way for exploring topologically tunable active matter.