Active Matter geometrically manipulated: from bacteria to human spermatozoa.

I. BERDAKIN; A. GUIDOBALDI; C. A. CONDAT; L.C. GIOJALAS; A. J. BANCHIO; A. V. SILHANEK; V. I. MARCONI

Roma

Conferencia; International Soft Matter Conference, ISMC; 2013

Univeridad La Sapienza

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 order to optimize the design of sorting micro uidic 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 eect is an eective method to induce inhomogeneous bacterial distributions in nanoliter chambers separated by a wall of asymmetric obstacles. Although the origin of this eect is well established, we show that its eciency 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 rectication eciency. 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 phe- nomenological model we optimized the geometrical connement habitat for accumulating the pop- ulation 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 ecient physical sperm guidance. Interesting dierences between bacteria and sperm micro-geometrical directioning arise from their dierent interactions with walls and corners (Fig.1). We suggest a new technological application inspired on the observed spermatozoa accumulation near walls.