A Novel Needle-Less Multi-Pin-‎Electrospinning Method to Fabricate ‎Nanofibers from Dilute PAN Solution

A novel needle-less electrospinning system, "Multi-pin-electrospinning" was developed to produce thin nanofibers from dilute Polyacrylonitrile (PAN) solutions. PAN solution was placed in an open polymer bath. 16 stainless steel pins in 4 parallel rows were attached to a metal rod to form stable polymer jets. Pins were dipped into a polymer solution by rotating the pins containing rod and under the application of the electric field, multiple Taylor cone were formed followed by the multi-jet ejection from the cone's tip, then nanofibers were deposited on the aluminum collector sheet placed above the pins. The multi-pin-electrospun nanofibers were thinner with narrower diameter distribution compared with electrospun nanofibers prepared through the conventional method. The influence of the affecting parameters such as solution concentration, applied voltage, pins-collector distance and addition of CaCl2 salt on the diameter of multi-pin-electrospun nanofibers were investigated. The applied voltage change did not significantly affect the average diameter of nanofibers. At pins-collector distance of 6 cm, wet nanofibers with the beaded structure were formed, whereas on increasing the distance bundles in the fibers were disappeared and straight nanofibers with fewer beads were collected. The addition of 1 wt% CaCl2 salt to the 3 wt% PAN/DMF solution resulted in the formation of smooth, almost bead-free nanofibers.