(271g) Field-Induced Knotting of Semi-Flexible Filaments in Centrifuge Systems

The settling dynamics of filaments in viscous fluids is a fundamental problem in fluid mechanics with implications in different fields of industry and science. For instance, the ultracentrifuge technique has been used for decades to separate DNA filaments based on length. In this study, we investigate the dynamics of a single semi-flexible Brownian filament in centrifuge systems. For the numerical scheme, the filament is discretized in the bead-spring fashion. We implement the Brownian Dynamics method accounting for hydrodynamic interactions to evolve the beads’ positions in time and capture the dynamics of the filament. We show that, as one increases the centrifuge rotational velocity, the filament’s configuration tends to collapse into dense structures, which leads to higher sedimentation factors. Above a critical rotational velocity, the filaments acquire stable configurations composed of a condensed head followed by a linear tail structure. The stability of such configurations is due to a field-induced knot-tightening mechanism caused by the tension introduced by the drag difference between the tail and head structures. We promote a statistical study on the different formed knots to better understand the role of rotational velocity and filament elasticity.