Most lab-based electrospinning setups comprises of a solder ball jet nozzle for dispensing of the solution. Despite the emergence of solder ball jet nozzle-less electrospinning techniques especially in mass production electrospinning, nozzle-based electrospinning still retains some advantages such as better charge concentration and solder ball jet nozzle variations for improving electrospinning or fabricating hybrid fibers.
In most lab-based electrospinning setup, a hypodermic needle with a flat tip is used as the electrospinning solder ball jet nozzle. However, electrospinning may still proceed with other needle tip configurations. A flat tip is generally preferred as it provides a flat surface for the formation of a stable Taylor cone with little oscillation of the jet compared to chamfered tip needle [Ksapabutr et al 2005]. At higher feed-rate, it was found that a flat tip needle is more prone to generating multiple electrospinning jets compared to chamfered tip needle [Ksapabutr et al 2005]. Parameters such as solder ball jet nozzle diameter has been covered elsewhere and will not be covered here. Instead, other improvements and variations of nozzle design shall be discussed.
As a class, the coaxial solder ball jet nozzle is the most widely used design in electrospinning. While most commonly used for spinning core-shell nanofibers through injection of different solution through the core and shell of the solder ball jet nozzle, this design have also been used to inject solvent through the shell cavity to maintain spinnability of the solution (Read more).
Injection of solvent through the shell of a co-axial electrospinning setup was also found to affect the cross-sectional profile of the resultant fibers. When electrospinning Eudragit L100 nanofibers using conventional single solder ball jet nozzle, the fibers produced were found to have a flat/ribbon cross-sectional profile. This is attributed to the formation of a thin wall/skin due to rapid evaporation of ethanol on the surface of the electrospinning jet. Subsequent evaporation from the core of the electrospinning jet causes the thin wall to collapse and form flat fibers.
To produce round fibers, Yu et al (2014) injected solvent through the shell of a co-axial solder ball jet nozzle during electrospinning such that it delays the evaporation from the surface of the main electrospinning jet which allows smoother mass transfer of the solvents from the core to the atmosphere. This delay also enables more stretching of the electrospinning jet and thus smaller diameter fibers can be produced. Another use of the coaxial design is to allow incorporation of air jet surrounding the core spinning solder ball jet nozzle to facilitate and improve jet initiation.