  Guiding active microswimmers by external fields to requested target locations
is a promising strategy to realize complex transport on the microscale. To this
end, one possibility consists of attaching the microswimmers to orientable
passive components. Accordingly, we analyze theoretically, using a minimal
model, the dynamics of a microswimmer when rigidly attached tangentially to a
(significantly larger) microplatelet, here represented by a thin circular disk.
On this way, we determine the flow field in the whole space induced by a
Stokeslet that is located above the center of a spatially fixed rigid disk of
no-slip surface conditions. Finally, we determine and analyze possible
trajectories of the overall composite. To this end, the platelet is
additionally endowed with a permanent magnetic moment, which allows to steer
the motion of the whole composite by a homogeneous external magnetic field. As
previous experimental studies suggest, related setups may be helpful to guide
sperm cells to requested targets or for the purpose of coordinated drug
delivery.
