Dynamics of semiflexible paramagnetic colloidal chains under a rotational magnetic field
Doctor of Philosophy
The rich dynamics of stiff and flexible filaments in flow and their propensity for non-reciprocal orbits is relevant for both naturally occurring and industrially relevant phenomena, such as flagellar motion and polymer processing, as well as for developing applications, such as microfluidic scale propulsion and fluid manipulation. However, the connection between a filament’s elastic properties, the external driving forces, and its resulting dynamics is not well understood; in particular, both computational and theoretical results indicate that the scaling behaviors of fibers in the intermediate semiflexible regime deviate from the results expected from rigid and flexible fibers. We synthesize paramagnetic colloidal particle chains, and then utilize a rotating magnetic field as an external force, with which we are able to experimentally identify and probe various dynamical regimes. By complementing our studies with Brownian dynamics simulations of a bead-spring chain as well as theoretical arguments, we find that the dynamics of the system depend on the dimensionless Mason and magnetoelastic numbers, and use them to elucidate, predict, and optimize fiber dynamics.
Colloids; polymer physics; semiflexible fibers