Active particle transport in disordered porous media

Fluid suspensions of motile microswimmers such as bacteria and active colloids are often observed in porous environments, but the complexity of the medium geometry and its effect on particle dynamics makes the study of their transport properties challenging. We provide insight into this problem by performing Brownian dynamics simulations in disordered environments at the scale of the constituent microscopic solid inclusions. The particles are modeled as point-sized active Brownian particles swimming through the interstices of a fluid-saturated porous medium composed of randomly distributed polydisperse solid inclusions. Our simulations reveal how the swimmer activity, together with geometrical properties of the surrounding medium, affect statistics of swimmer distributions, orientations and long-time transport. We also study the effects of an imposed pressure-driven Stokes flow through the porous matrix, where we elucidate the role of advection and local shear-induced reorientations on microswimmer dynamics.