  Depletion forces exerted by self-propelled particles on circular and
elliptical passive objects are studied using numerical simulations. We show
that a bath of active particles can induce repulsive and attractive forces
which are sensitive to the shape and orientation of the passive objects (either
horizontal or vertical ellipses). The resultant force on the passive objects
due to the active particles is studied as a function of the shape and
orientation of the passive objects, magnitude of the angular noise, distance
between the passive objects. By increasing the distance between obstacles the
magnitude of the repulsive depletion force increases, as long as such a
distance is less than one active particle diameter. For longer distances, the
magnitude of the force always decrease with increasing distance. We also found
that attractive forces may arise for vertical ellipses at high enough area
fraction.
