  Using Molecular Dynamics simulations of a coarse-grained polymer liquid we
investigate the transport of droplets on asymmetrically structured (saw-tooth
shaped), vibrating substrates. Due to a continuous supply of power by substrate
vibrations and the asymmetry of its topography, the droplets are driven in a
preferred direction. We study this directed motion as a function of the size of
the droplets, the linear dimensions of the substrate corrugation, and the
period of vibrations.
  Two mechanisms of driven transport are identified: (i) one that relies on the
droplet's contact lines and (ii), in a range of vibration periods, the entire
contact area contributes to the driving. In this latter regime, the set-up may
be used in experiments for sorting droplets according to their size.
Additionally, we show that the linear dimension of the substrate corrugation
affects the flux inside the droplet. While on a substrate with a fine
corrugation droplets mostly slide, on a more coarsely corrugated substrate the
flux may exhibit an additional rotation pattern.
