Spinneret core-shell

Figure 4.3 Schematic Illustration of the set-up used to coelectrospin compound core-shell nanofibers. It involves the use of a spinneret consisting of two coaxial capillaries through which two polymer solutions can simultaneously be ejected to form a compound jet. (Reprinted with permission from Advanced Materials, Compound Core-Shell Polymer Nanofibers by Co-Electrospinning by Z. Sun, E. Zussman, A. L. Yarin eta ., 15, 22, 1929-1932. Copyright (2003) Wiley-VCH)...

A coaxial setup uses a multiple solution feed system that allows for the injection of one solution into another at the tip ofthe spinneret. The sheath fluid act as a carrier drawing in the inner fluid at the Taylor cone ofthe electrospinning jet. If the solutions are immiscible then a core-shell structure is usually observed. Miscible solutions, however, can result in porosity or a fiber with distinct phases due to phase separation during solidification ofthe fiber. 

Spinneret design Coaxial spinneret Hollow or core-shell nanofibers... 

Spinneret needle has been modified in some semps to produce nanofibers with new properties. For instance, coaxial spinneret which consists of two capillary spinnerets one inside another has been developed for some certain purposes and applications (Fig. 5a). This modified spinneret is capable of producing hollow nanofibers (Fig. 5b) (Li and Xia 2004). Core-shell nanofibers can also be obtained using this modified coaxial spinneret through spinning two different and immiscible polymer solutions (Zander 2013) (Fig. 5c) or emulsion polymer solution (Fig. 5d). 

Fig. 5 a Coaxial spinneret of a modified electrospinner, b the obtained hollow nanofibers, c spinning of two immiscible polymer solutions in form of core-shell nanofibers using a coaxial spinneret, d spinning of polymer emulsion solution through single nozzle spinneret. Adopted with modification from Pham et al. (2006) and Zander (2013)... 

Modifications in spinneret nozzles and collectors have been done in order to produce nanofibers with more utilized features. For instance, coaxial spinnerets were developed to form core-shell nanofibers. Rotating discs and dmms were developed in order to obtain oriented nanofibers, while meshes were used for obtaining nanofibrous patterns at the macroscale or microscale. 

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