  Suitable asymmetric microstructures can be used to control the direction of
motion in microorganism populations. This rectification process makes it
possible to accumulate swimmers in a region of space or to sort different
swimmers. Here we study numerically how the separation process depends on the
specific motility strategies of the microorganisms involved. Crucial properties
such as the separation efficiency and the separation time for two bacterial
strains are precisely defined and evaluated. In particular, the sorting of two
bacterial populations inoculated in a box consisting of a series of chambers
separated by columns of asymmetric obstacles is investigated. We show how the
sorting efficiency is enhanced by these obstacles and conclude that this kind
of sorting can be efficiently used even when the involved populations differ
only in one aspect of their swimming strategy.
