Electrospinning (ES) is one of the most useful techniques to form nanofibers in a diameter of several hundred nanometers (Doshi & Reneker, 1995, Buchko et al., 1999, Huang et al., 2003). The diameter of the nanofibers produced by ES is at least one or two orders of magnitude smaller than those of conventional fiber production methods like melt or solution spinning. As a result, the electrospun ...