Obstacle-induced lateral dispersion and nontrivial trapping of flexible fibers settling in a viscous fluid

We investigate the dynamics of a single flexible fiber settling in a viscous fluid embedded with obstacles of arbitrary shapes. We show that the presence of obstacles may lead to two types of events: gliding and trapping. In particular, we observe nontrivial trapping conformations on sharp obstacles that result from a subtle balance between elasticity, gravity, and friction. In the gliding case, a flexible fiber reorients and drifts sideways after sliding along the obstacle. We show how these effects can be leveraged to propose an efficient strategy to sort fibers based on their size and/or elasticity.