  We report numerical results which show the achievement of net transport of
self-propelled particles (SPP) in the presence of a two-dimensional regular
array of convex, either symmetric or asymmetric, rigid obstacles. The repulsive
inter-particle (soft disks) and particle-obstacle interactions present no
alignment rule. We find that SPP present a vortex-type motion around convex
symmetric obstacles even in the absence of hydrodynamic effects. Such a motion
is not observed for a single SPP, but is a consequence of the collective motion
of SPP around the obstacles. An steady particle current is spontaneously
established in an array of non-symmetric convex obstacle (which presents no
cavity in which particles may be trapped in), and in the absence of an external
field. Our results are mainly a consequence of the tendency of the
self-propelled particles to attach to solid surfaces.
