Geometric optimization for motility-based microorganism concntrator and sorter devices

I. BERDAKÍN; Y. JEYARAM; A. SILHANEK; A. GUIDOBALDI; L. GIOJALAS; C.A. CONDAT; V.I. MARCONI

Carlos Paz, Córdoba

Congreso; LAWNP 2013 - XIII Latin American Workshop on Nonlinear Phenomena; 2013

The use of soft litography to build asymmetric micro-substrates makes it ossible to control microorganism motion and promises new and interesting applications inhealth industry and biotechnology. In this work we investigate two ways in which these ratchet devices can be employed. First we show, experimentally and numerically, that it is possible to accumulate sperm cells in a region of space of our choice. Second, we study the most efficient way to sort out different subpopulations in a mixed culture of E. coli bacteria that differ by their specific swimming strategies. In both cases we develop models that incorporate the most relevant phenomenological aspectsof the cellular motion using realistic parameters found in experiments, and integrate the equations of motion using molecular dynamics algorithms. For E. coli we study the diffusion properties of each subpopulation along the sorter and define a purity parameter for the extraction of each strain as a function of position. We obtain a set of optimized parameters of the array geometry that maximizes the sorting efficiency of the device. Our results show remarkably that it is possible to sort bacteria with 100% purity even for slightly different strains in experimentally reasonable times. We also conclude that a key element to consider when spermatozoa is that their interactions with walls and corners is different from that of run-and-tumble bacteria, because sperm cells tend to get trapped in acute angles.