Transport of microswimmers in complex media

Locomotion by swimming and the ability to randomly change their swimming direction are important ingredients for the survival strategy of many micro-organisms in their often densely packed environments. Using computer simulations and modeling we identified a geometric criterion, which predicts that micro-swimmers can spread most effectively, when the length they swim before they reorient corresponds roughly to the length of the longest pore of the porous medium. This finding could be important for the design of new cargo-carriers, which should be capable of operating in complex environments.