(464e) Dynamics and Rotational Regimes of Semi-Flexible Colloidal Chains

The interaction between flexible filaments and a surrounding fluid has been a topic of study for many years, due to its relevance to both naturally occurring and industrially relevant phenomena. However, the connection between a fiberâ??s elastic properties, the external driving forces, and the eventual dynamics of the fiber is not well understood. Fibers in the semi-flexible regime, such as microtubules and carbon nanotubes, are of particular interest, as the competition of elastic, hydrodynamic, and external forces appear to cause deviations from the scalings expected of rigid and flexible fibers. We thus investigate the dynamical behavior of semi-flexible fibers experimentally, through the use of a tunable model system consisting of linked paramagnetic particle chains; when chains are driven by an external rotating magnetic field, which exerts a torque profile analogous to that of shear flow, we observe multiple regimes of dynamical behavior. By pairing experiments, computational models, and theoretical calculations, we find that the dynamics of the system depend on the dimensionless Mason and magnetoelastic numbers, which we then use to identify and classify the regimes of different rotational modes.