History of Electrospining

Thursday, January 5, 2017

The origin of electrospinning as a viable fiber spinning technique can be traced back to the early 1930s. In 1934, Formhals patented his first invention relating to the process and the apparatus for producing artificial filaments using electric charges. Though the method of producing artificial threads using an electric field had been experimented with for a long time, it had not gained importance until Formhals’s invention due to some technical difficulties in earlier spinning methods, such as fiber drying and collection. Formhals’s spinning process consists of a movable thread collecting device to collect the threads in a stretched condition, like that of a spinning drum in the conventional spinning.
In the 1960s, fundamental studies on the jet forming process were initiated by Taylor. In 1969, Taylor studied the shape of the polymer droplet produced at the tip of the needle when an electric field is applied and showed that it is a cone and the jets are ejected from the vertices of the cone. This conical shape of the jet was later referred to by other researchers as the “Taylor Cone” in subsequent literature. By a detailed examination of different viscous fluids, Taylor determined that an angle of 49.3 degrees is required to balance the surface tension of the polymer with the electrostatic forces. The conical shape of the jet is important because it defines the onset of the extensional velocity gradients in the fiber forming process.
Electrospinning is a unique approach using electrostatic forces to produce fine fibers. Electrostatic precipitators and pesticide sprayers are some of the well known applications that work similarly to the electrospinning technique. Fiber production using electrostatic forces has invoked glare and attention due to its potential to form fine fibers. Electrospun fibers have small pore size and high surface area. There is also evidence of sizable static charges in electrospun fibers that could be effectively handled to produce threedimensional structures.
The advantages of the electrospinning process are its technical simplicity and its easy adaptability. The apparatus used for electrospinning is simple in construction, which consists of a high voltage electric source with positive or negative polarity, a syringe pump with capillaries or tubes to carry the solution from the syringe or pipette to the spinnerette, and a conducting collector like aluminum. The collector can be made of any shape according to the requirements, like a flat plate, rotating drum, etc.