Geometrical guidance and trapping transition of human sperm cells
  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. 
A. Guidobaldi, Y. Jeyaram, I. Berdakin, V. V. Moshchalkov, C. A.   Condat, V. I. Marconi, L. Giojalas, A. V. Silhanek
cond-mat.soft physics.bio-ph