Colored dyes in both solution in the coaxial setup showed CME coloration on the collected fibers at lower voltage and N6 coloration at higher voltage. At higher voltage, a 2D membrane was formed and this behaviour matches that of when N6 only solution was electrospun. In coaxial electrospinning of both solution, a lower applied voltage resulted in more CME fibers deposited with depositing fibers climbing towards the nozzle as if it was electrospinning CME only solution. Individually, CME solution require a lower voltage for electrospinning jet initiation compared to N6 solution. Bazrafshan et al (2018) found that in their coaxial electrospinning of collagen-g-poly(MMA-co-EA) (CME) shell and nylon 6 (N6) core. In coaxial electrospinning, the charges on the core and shell solution may be different although the voltage applied is the same. Although it may be more challenging to use imaging to view the core-shell structure, comparison of the drug release rate between core-shell fiber and fiber with uniformly dispersed drug showed the shell was able to retard the release of drug from its core. Some investigators have used the same polymer solution for the core and the shell for the purpose of controlling drug release from the core of the fiber. However, this depends on the application. Chakraborty et al (2009) recommended selecting solutions pair with similar volatility and use of intermediate solvent where miscibility of core and shell solution is poor. There are also some selection criteria for the core and shell solution pair. Fiber diameter can be controlled by the nozzle diameter while the volume ratio is by the feed-rate of the core and shell solution. There are several parameters that can be modified to control the size of the fibers and the volume ratio of the core and shell material. Two different solutions are dispensed simultaneously through the inner and outer cylinders and charged in the same way as conventional single bore nozzle. The co-axial nozzle comprises of two cylinders with a one cylinder situated within the core of a larger bore cylinder.
The carrier solvent for the molecules may be immiscible such that the solvents may separate and dry core-shell fibers are collected.Ĭore-shell fibers are most often produced by using a co-axial nozzle for electrospinning. In some solution mixtures, the molecules may self-organize during electrospinning. However, other methods have since been found to be capable of forming core-shell fibers. A common use of core-shell fibers composite is to have a mechanically stronger core material and a functional shell material.Ī co-axial nozzle is the earliest method used in the production of core-shell fibers. Core-shell fibers may also be used to encapsulate monomers or initiators in self-healing materials. In controlled drug release, the drug is often encapsulated within the core of the fiber such that the polymeric shell layer acts as a barrier to reduce unwanted burst release. Core-shell fibers are often used for molecular release or for the creation of composite fibers.