Transport of active particles through porous media

The transport of self-propelled particles such as bacteria or phoretic swimmers through porous materials is relevant to many natural and engineering processes, from biofilm formation and contamination processes to transport in soils and biomedical devices. In this talk, I discuss two distinct approaches aimed at predicting the long-time dispersion of self-propelled particles in idealized porous media. In a first approach, generalized Taylor dispersion theory is applied to analyze the long-time statistics of an active Brownian particle transported under an applied flow through the interstices of a periodic lattice. The model is used to unravel the roles of motility, fluid flow, and lattice geometry on the asymptotic mean velocity and dispersion coefficient. Unexpected trends are predicted, including a nonmonotonic dependence of axial dispersion on flow strength and a reduction in dispersion due to swimming activity in strong flows. In a second approach, the case of random media is considered using a statistical framework, and the long-time dispersion coefficient of a run-and-tumble particle swimming though a random distribution of circular obstacles is calculated analytically.