Active Matter Manipulation: from bacteria separation to human espermatozoa guiding

I. BERDAKIN; L. VENKEN; Y. JEYARAM; H. A. GUIDOBALDI; V. V. MOSHCHALKOV; J. VANDERLEYDEN; ADOLFO J. BANCHIO; L .C. GIOJALAS; A. V. SILHANEK; C.A. CONDAT; V. I. MARCONI

Bad Honnef

Workshop; JÜLICH SOFT MATTER DAYS 2012; 2012

FORCHUNGSZENTRUM JÜLICH

This numerical and experimental interdisciplinary work is aimed to understand the complexrelation between a population of self-propelled micro-swimmers and the micro-patterned confinementgeometry in order to optimize the design of microfluidic devices.It has been shown that a nanoliter chamber separated by a wall of asymmetric obstacles can leadto bacteria inhomogeneous distribution. Although it is well established that this rectificationeffect arises from the interaction between swimmers and the non-centrosymmetric pillars, herewe show that its efficiency is strongly dependent on the detailed dynamics of the individualmicroorganism. Simulations indicate that, for run-and-tumble dynamics, the distribution of runlengths and the partial preservation of run orientation memory through a tumble turn out to beimportant factors when computing the efficiency. We optimized the geometrical dimensions inorder to maximize the separation efficiency. Complementarily experiments are being performedusing e. coli mutants.In addition we consider human espermatozoa rectification, cells with a completely differentswimming strategy compared with bacteria. Using a simple phenomenological model we optimizedthe geometrical confinement habitat for accumulating the population and we use it fordesigning new devices. We conclude that both swim strategy and swimmers size are crucialto design the optimum micro-patterned architecture for new biomedical devices able to achieveefficient physical sperm guidance. We show that interesting differences between bacteria andsperm micro-geometrical directioning arise from their different interactions with the wall. Wesuggest a new technological application inspired on the observed spermatozoa accumulationnear walls.We also study simple artificial swimmers using Stokesian Dynamics simulations which includethe full hydrodynamic interaction effects. We analyze their swimming velocity and energydissipation as well as their trajectories during binary collisions. This complementary knowledgewill help us to improve our simple phenomenological model.