  We investigate the transport of active matter system in the presence of a
disordered square lattice of half-circles, which is built by removing a
fraction of them from the initial full lattice. We consider no external field.
We observe a spontaneous inversion of the net current, compared to the usual
sense of such a current reported in previous papers, if the obstacle has the
same diameter as the unit cell of the square lattice. If this diameter is
smaller, there is no inversion. We show a calculation that reproduces our
numerical results qualitatively, based on the argument that such effects are
the results of the imbalance of particles traveling in the positive and the
negative directions due to traps formed by the obstacles: for positive
travelers the traps are the spaces between neighboring obstacles, while for
negative travelers, they are the flat side of the obstacles.
