  Effective mixing of fluids at the microfluidic scale is important for future
applications in biology, medicine, and chemistry. A promising type of
micromixers are magnetic filaments, which can be activated by an external
magnetic field. However, there is a lack of research that combines experiments
and numerical modelling of hydrodynamics around such filaments. Here we use
micro-particle image velocimetry to measure flow fields around rotating
flexible ferromagnetic filaments and compare them to numerical data from
elastic rod model. We measure that rotating filaments hover above the surface,
whereas the resulting fluid velocities are highly dependent on the hovering
distance. We also find that the rotating filament causes a 3D flow coming from
the rotational plane and being extracted along the axis of rotation. These
findings will help develop better micromixers.
