I had set up an in-house electrospinning apparatus with a horizontally positioned solution electrode and collection plate. The fiber mat from the collector has varied thicknesses from the center of the collection plate to the edge.
the variance is most likely due to Coulomb's law. This is because the difference between the charge on the fiber and the charge on the plate is the same everywhere, but the distance is different, so the place closest to the fiber output will have the thickest mat.