Microdevices useful to manipulate bacteria need to be revised for controlling efficiently sperm cells trapping and guidance
Prof. Dr. Veronica Marconi
University of Cordoba, Argentina
- 24 Jun 2014 10:30
- 24 Jun 2014 11:30
- Seminarraum A1-A3, Building 04.6
It has been shown that the ratchet effect is an effective method to induce inhomogeneous bacterial distributions in nanoliter chambers separated by a wall of asymmetric V-shaped obstacles. Although the origin of this effect is well established, we show that its observed effciency is strongly dependent on the detailed dynamics of the individual microorganisms. Our numerical results indicate that for run-and-tumble dynamics, the distribution of run lengths, the partial memory of run orientation after a tumble and the rotational diusion are crucial factors when computing the rectication effciency. We show that all are essential ingredients to get a perfect agreement with experiments and to be able to improve and suggest new microdevices of control . In addition, we optimize the geometrical dimensions of the V-obstacles in order to maximize the swimmer concentration and we illustrate how it can be used for sorting by swimming strategy using a long array of parallel walls [1, 2].
Following these previous ideas we wanted to guide and control spermatic cells using a purely physical and non-invasive method in view of applications to human reproduction. Unexpectedly, interesting differences between bacteria and sperm micro-geometrical guidance are observed, due to their specific interactions with walls and trapping in the corners. Effects of geometrical guidance and concentration is studied in detail both theoretically and experimentally. 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 U-shaped asymmetric obstacles to take advantage of the spermatozoa specific swimming strategy along walls and corners .
 Influence of swimming strategy on microorganism separation by asymmetric obstacles, I. Berdakin et al., Phys. Rev. E, 87, 052702 (2013).
 Quantifying the sorting efficiency of self-propelled run-and-tumble swimmers by geometrical ratchets, I. Berdakin et al., Cent. Eur. J. Phys. 11(12), 1653-1661 (2013).
 A. Guidobaldi et al. Geometrical guidance and trapping transition of human sperm cells, I. Berdakin et al., Phys. Rev. E, 89, 032720 (2014).
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