Electrospinning is a novel process for forming fibers with fine thickness ranging from micron scale diameter to nano scale one through the action of electrostatic forces. The collected fibers as nonwoven mats have some useful properties such as high surface area mass ratio, and thus have great potentials in filtration, biomedical, and sensing application. However, most previous methods on electrospinning have involved polymer solutions. Even though the solvents in the polymer solution are easily evaporated during electrospinning, this solvent method makes harmful goods that are not useful to apply for the medical and bio related applications. Therefore there has continuously been an industrial need for the production of solvent-free materials using electrospinning techniques.

     Electrospinning directly from polymer melts can offer several advantages over electrospinning from polymer solution, such as the elimination of solvents, higher throughput, and the ability to use polymers that do not have convenient room temperature solvents. A related Cornell technology (D-3439, US Patent No. 7,326,043) presents a polymer melt electrospinning solution.  However, melt electrospinning still has a major drawback that the resulting fibers tend to be relatively thicker than those from solution electrospinning.

     The present invention solves these problems through gas assisted melt electrospinning where a heated gas stream is applied to one of two or multiple axial jets. The heated gas jet can secure the nozzle heating for inner melt jet(s) and thus delay solidification. The high flow rate of heated gas stream can keep providing additional drag force to the jet surface, leading to thinner fibers with higher production rate. As a result, due to additional deformation caused by the heated gas stream, submicron scale fibers can be obtained from melt electrospinning even without inducing a whipping motion. Without the whipping motion of the polymer jet, a guide channel for the melt jet surrounded by a heated gas stream can be installed to control the orientation and layout of nanofibers. If the inner channel is used for a gas stream, the resulting fibers can possess a hollow structure along the fiber axis. As the heated gas goes through the outer channel of spinneret, temperature of a molten polymer in the inner channel of the spinneret is kept high, and furthermore, the ejected heated gas jet offers additional thinning of the melt jet due to huge tangential drag force. Since the temperature, quantity and velocity of the gas stream can be controlled in the gas assisted melt electrospinning (GAME) process, various polymers can be used to produce much thinner fibers with higher production rate than the conventional melt electrospinning. Secondly, the controlled gas runs through the inner channel of spinneret, while the molten polymers go through the outer channel. The inner gas stream can prevent the outer melt jet being collapsed, and thus the resulting fibers can possess a hollow structure along the fiber axis.

Figure 1.  Schematic of gas assisted electrospinning device.

Potential Applications

• Electrospinning equipment

Advantages

• Melt electrospinning requires no solvents
• Device produces ultrathin fibers at high production rates

File Number: 4923