Active matter physically manipulated: bacteria vs human sperm cells.

V.I. MARCONI

La Plata

Workshop; Workshop PASI 2014; 2014

Active Matter physically manipulated: bacteria vs human sperm cellsI. Berdakin1, H.A. Guidobaldi2, A.J. Banchio1, C.A. Condat1, L.C. Giojalas2, A.V. Silhanek3, V.I. Marconi11 Facultad de Matemática, Astronomía y Física, Universidad Nacionalde Cordoba and IFEG-CONICET. 5000 Cordoba. Argentina.2 Centro de Biología Celular y Molecular (CeBiCeM). Facultad de Ciencias Exactas Físicas y Naturales. Universidad Nacional de Córdoba. 5000 Cordoba. Argentina.3 Departement de Physique, Université de Liege, B-4000 Sart Tilman, Belgium.This numerical and experimental work is aimed to understand the complex relation between populations of self-propelled micro-swimmers and micro-patterned connement geometries, in orderto optimize sorting and guiding micro uidic devices based on purely physical methods. Both, precise phenomenological models based on experimental motility parameters [1{3] and simple microswimmermodels using stokesian dynamics [4], were developed.It has been shown that the ratchet eect is an eective method to induce inhomogeneous bacterial distributions in microchambers separated by a wall of asymmetric V-shaped obstacles. Althoughthe origin of this eect is well established, we show numerically that its eciency is strongly dependent on the detailed dynamics of the individual microorganism. Simulations indicate that, forrun-and-tumble dynamics, the distribution of run lengths, the partial memory of run orientation after a tumble and the rotational difusion are important factors when computing the recticationeciency [1]. We optimize the geometrical dimensions of the asymmetric obstacles in order to maximize the swimmer concentration and we illustrate how it can be used for sorting by swimming strategy using an efficient long array of parallel walls [2].In addition we investigate diluted human sperm cell populations guided by asymmetric obstacles with a variety of geometries. Using realistic sperm models we optimized the confinement habitat foraccumulating the population. In particular, a trapping transition at convex angular wall features is identified and analyzed. We conclude that the specic self-propelled swimmer strategy and specificswimmer-wall interactions are crucial to design the optimum micro-patterned architecture able toachieve ecient physical sperm guidance. Interesting dierences between bacteria and sperm micro-geometrical guidance arise from their dierent interactions with walls and sharped corners. We showthat highly ecient microratchets can be fabricated by using curved asymmetric obstacles to takeadvantage of the spermatozoa specic swimming strategy along walls. These results sound verypromising and attractive for further rened designs in biotechnological applications [3].[1] In uence of swimming strategy on microorganisms separation by asymmetric obstacles, I. Berdakin, Y. Jeyaram, V.V.Moshchalkov, L. Venken, S. Dierckx, S.J. Vanderleyden, A.V. Silhanek, C.A. Condat, V.I. Marconi. Phys. Rev. E 87 052702(2013). arXiv:1305.5428v2.[2] Quantifying the sorting eciency of self-propelled run-and-tumble swimmers by geometrical ratchets, I. Berdakin, A. V.Silhanek, H. N. Moyano, V. I. Marconi, C. A. Condat. C. Eur. J. of Phys. (2013), DOI: 10.2478/ s11534-013-0300-7.arXiv:1305.5434.[3] Geometrical guidance and trapping transition of human sperm cells, A. Guidobaldi, Y. Jeyaram, I. Berdakin, V. V.Moshchalkov, C. A. Condat, V. I. Marconi, L. Giojalas, A. V. Silhanek. Phys. Rev. E (2014), in edition. arXiv: 1401.2551[4] Three linked spheres micro-swimmers: a stokesian dynamics study, I. Berdakin, V.I. Marconi, A.J. Banchio. PRE 2014.