Title: Entanglement and localization of active filaments in a square well.

Author (Table Talk): Sohum Kapadia, Clark University

Abstract:

We will present a study of the dynamics of Lumbriculus variegatus (or California blackworm) under quasi 2D square confinement as a model of active filaments that can entangle as a function of their number density. We demonstrate by tracking the entire shape of the worms inside transparent laser-cut chambers with square cross sections, that the worms are not uniformly distributed, but can be found with greater probability near the boundaries, and exhibit trapping at corners. In the limit of a single worm, we show that the body orientation of the worm aligns along the boundary as it moves forward. However, when it encounters a corner, it gets trapped until a larger fluctuation in its undulations rescues it from the corner. We show that an active dumbbell model can capture the overall behavior exhibited by the worm as it moves, gets trapped, and escapes from the corner. Then, we examine the effect of worm-worm interactions on the observed dynamics. While worms are found to continue to aggregate at corners at large densities, they are found to react with sudden rapid motions due to collisions with the neighbors. We shall discuss the resulting effects on the trapping time and escape as a result of these counter trends.