  The guidance of human sperm cells under confinement in quasi 2D microchambers
is investigated using a purely physical method to control their distribution.
Transport property measurements and simulations are performed with dilute sperm
populations, for which effects of geometrical guidance and concentration are
studied in detail. In particular, a trapping transition at convex angular wall
features is identified and analyzed. We also show that highly efficient
microratchets can be fabricated by using curved asymmetric obstacles to take
advantage of the spermatozoa specific swimming strategy.
