  Microscopic swimmers, e.g., chemotactic bacteria and cells, are capable of
directed motion by exerting a force on their environment. For asymmetric
microswimmers, e.g., bacteria, spermatozoa and many artificial active colloidal
particles, a torque is also present leading in two dimensions to circular
motion and in three dimensions to helicoidal motion with a well-defined
chirality. Here, we demonstrate with numerical simulations in two dimensions
how the chirality of circular motion couples to chiral features present in the
microswimmer environment. Levogyre and dextrogyre microswimmers as small as
$50\,\mathrm{nm}$ can be separated and selectively trapped in \emph{chiral
flowers} of ellipses. Patterned microchannels can be used as \emph{funnels} to
rectify the microswimmer motion, as \emph{sorters} to separate microswimmers
based on their linear and angular velocities, and as \emph{sieves} to trap
microswimmers with specific parameters. We also demonstrate that these results
can be extended to helicoidal motion in three dimensions.
