Garland formation process in electrospinning

Abstract

The electrospinning technique has become a widely used method to produce nanofibers. Much experimental and theoretical work has been done to investigate the electrospinning process. A typical path of a single jet of polymer solution begins with a straight segment, and then a bending instability generates coils inside a cone shaped envelope. The jet elongates and becomes thinner, and dries into a nanofiber.Polystyrene solutions with different salt concentrations were electrospun to investigate the effect of changing the electrical conductivity on the fibers that were formed. Salt increased the conductivity of the solution and smooth fibers formed. Electrospinning a polystyrene solution with salt, at relatively high voltage, caused the jet to first form bending coils with small and slowly increasing diameters. These small diameter coils were subsequently incorporated into a larger diameter bending instability coil. That is, a coil with a slender envelope cone developed first and this slender coil formed a larger bending coil with a more rapidly increasing diameter. This unusual situation produced a complicated jet path, which is called a “garland”. The coils entangled and conglutinated in flight to form a fluffy network of fibers. The conditions for the formation of garlands also provide examples of jet splitting and branching during the electrospinning process.