Self-propelled microswimmers: from bacteria and human spermatozoa to artificial swimmers

I. BERDAKIN; ADOLFO J. BANCHIO; H. N. MOYANO CORTÉZ; C.A. CONDAT; V. I. MARCONI

Buenos Aires

Otro; XV Giambiagi Winter School; 2013; 2013

This numerical and experimental work is aimed to understand the complex relation betweenpopulations of self-propelled micro-swimmers and micro-patterned confinement geometries, in order to optimize the design of sorting microfluidic devices. Both, precise phenomenological models based on experimental motility parameters and simple microswimmer models using Stokesian Dynamics, are developed. 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 obstacles. Although the origin of this effect is well established, we show that its effciency is strongly dependent on the detailed dynamics of the individual microorganism. Simulations indicate that, for run-and-tumble dynamics, the distribution of run lengths and the partial memory of run orientation after a tumble are important factors when computing the recti?cation effciency. In addition, 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 a long array of parallel obstacles. We also investigate human spermatozoa guided by asymmetric obstacles. Using a realistic phenomenological model we optimized the geometrical confinement habitat for accumulating the population and we use it for designing new devices. We conclude that the swimmer strategy, cells size, and swimmer-wall interactions are crucial to design the optimum micro-patterned architecture able to achieve effcient physical sperm guidance. Interesting differences between bacteria and sperm micro-geometrical directioning arise from their different interactions with walls and corners (Fig.1). We suggest a new technological application inspired on the observed spermatozoa accumulation nearwalls.