  Spontaneous segregation of run-and-tumble particles with different velocities
in microchannels is investigated by numerical simulations. Self-propelled
particles are known to accumulate in the proximity of walls. Here we show how
fast particles expel slower ones from the wall leading to a segregated state.
The mechanism is understood as a function of particle velocities, particle
density, or channel width. In the presence of an external fluid flow, particles
with two different velocities segregate due to their different particle fluxes.
Promising applications can be found in the development of microfluidic
lab-on-a-chip devices for sorting of particles with different motilities.
