Methods for controlled electrospinning of polymer fibers are described. The methods include spinning a polymer fiber from a fluid comprising a polymer in the presence of an electric field established between a plurality of collectors and a jet supply device controlling the dispersion characteristics of the fluid by applying a magnetic field created by at least one magnet located after the point of jet formation. Different voltages are applied to at least two collectors of the plurality of collectors. At least one magnet, located between the jet supply device and at least one collector, creates a magnetic field substantially transverse or substantially collinear to an electrospinning jet stream. The magnetic field changes direction of travel of the electrospinning jet stream.