  Micro-swimmers can serve as cargo carriers that move deep inside complex flow
networks. When a school collectively entrains the surrounding fluid, their
transport capacity can be enhanced. This effect is quantified with good
agreement between experiments with self-propelled droplets and a confined
Brinkman squirmer model. The volume of liquid entrained can be much larger than
the droplet itself, amplifying the effective cargo capacity over an order of
magnitude, even for dilute schools. Hence, biological and engineered swimmers
can efficiently transport materials into confined environments.
