**1.2. Nanoscale fibers**

Although only a few fibers smaller than 1 µm can be detected in traditional non-woven processes as for so-called "sea-island melt spinning"[13] and the recently developed flashspinning process [14], small continuous fibers with nanoscale diameters can be easily attained via the electrospinning process. Before the 1990s, researches had produced ultrafine fiber around 1 µm and found this method had the potential for nanometer fiber preparation. Until 1996, works by Darrell H Reneker and Iksoo Chun [11] demonstrated that many polymer solutions and melts can be produced into nanofiber in the range 40-2000nm. After that, great attention was given to this technique for nanofiber production. Nowadays more than 3,000 papers and patents per year (Figure 2) are published on electrospun nanofiber preparation and its applications based on more than 200 kinds of polymers.

Non-woven fabrics using nanoscale fibers always exhibit a high specific surface area and smaller pores and channels though the fabric, which means more functional molecules become exposed on the surface of the fiber or channels. This advantage can be applied into several high-end fields like high sensitive flexible sensor, efficient filter element, immobilized catalyst, and high energy storage element.
