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Lundi 30 juin 2014 14:00 - Duree : 1 heure
Lieu : Conference room - LIPhy - Bât E - 140 Avenue de la Physique - St Martin d’Hères. Accès par interphone, appeler le secrétariat

Orateur : Veronica MARCONI (Mathematics, Astronomy and Physics Faculty, National University of Córdoba and IFEG-CONICET, Argentina)

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 efficiency 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 diffusion are crucial factors when computing the rectification efficiency. We show that all are essential ingredients (distinct of each mutant) to get a good 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.

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 show that highly efficient microratchets can be fabricated by using U-shaped asymmetric obstacles to take advantage of the spermatozoa distinct swimming strategy along walls and corners.

Contact : ezequiel.ferrero@ujf-grenoble.fr

Discipline évènement : (Physique)
Entité organisatrice : (LIPhy)
Nature évènement : (Séminaire)
Evènement répétitif : (Séminaire Mat. Molle/grise)
Site de l'évènement : Domaine Universitaire de St Martin d’Hères

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