Ratchet funnels for swimming bacteria
Rectification of motile E. Coli bacteria has been experimentaly observed when confined in a closed environment separated by a series of funnel walls. In this project, we try to simulate this effect by using the lattice Monte Carlo model which is detailed enough to take mechanical and thermodynamical properties of round-shape autonomous cells into account. Motilities of bacterial cells can be easily controlled by both an applied external gradient on all monomers of the cell and the run / tumble transition duration. The rectification ability of funnel walls is found to strongly depend upon both the mean random walk step length of motile cell and the gap size between two adjacent walls. Our results not only agree well with experimental observations, but also confirm some deductions from a previous simple model of point-like bacteria. In addition, the present model can be extended to study cells at different shapes rather the round ones, e.g. cigar-shape bacteria. This feature makes it possible to study some characteristic properties of cells, such as anisotropy, collective behaviours, etc.