Unique hollow ceramic composite nanofibers have also been constructed with clever selection of core and shell material. A higher evaporation rate facilitates the solidification and formation of an intact wall soon after leaving the nozzle tip. A high surface tension solvent will certainly overcome the supporting air blowing at the core and cause the collapsed or contraction of the wall leading to the formation of solid fibers. Yu et al (2014) hypothesized that low surface tension and higher evaporation rate of CHCl 3 is the reason for the formation of the hollow fibers. While Fe 3O 4/Eu(BA) 3phen/PVP was able to form hollow fiber using chloroform, CHCl 3 as the solvent, solid fibers were formed using DMF. Their study showed that solvent selection plays an important role in the formation of hollow fibers by blowing air through its core. Yu et al (2014) examined the factors that allows for the fabrication of Fe 3O 4/Eu(BA) 3phen/PVP hollow fibers. Using air as the core "material" means that post spinning process is not necessary. In a novel coaxial electrospinning technique, air, instead of solution was used as the core "material". In the construction of ceramic hollow fiber, other polymers may be used in the core as they can be removed during the sintering process. This causes solidification of the shell material at the interface during electrospinning and subsequent solvent vaporization encourages the core material to migrate to the interface thus forming a hollow fiber. Hollow fibers may also be formed using a core solution in which the solvent used is a non-solvent for the shell material. Depending on the post-spinning process, oil is often used as the temporary material as it is relatively easier to remove them than other higher molecular weight material. Hollow fiber constructed using coaxial electrospinning typically with a temporary material as the core and the actual material as the shell. When the core-material is made out of low molecular material or oil, these can be easily extracted to form hollow fibers. For this setup, only one of the materials needs to be electrospinninable to carry the drug. This is particularly useful in drug delivery application where the drug is typically loaded in the core such that the sheath provides a barrier to reduce the drug release rate. Such fibers are known as core-shell fibers as the core and sheath materials that made up the fibers are made from two distinct materials. TEM of calcium phosphate nanoparticles encapsulated within gelatine nanofiber Ī coaxial nozzle design enables two different materials to be dispensed for electrospinning of nanofibers. TEM analysis revealed the presence of nanoparticles at the core of the fibers but they were not uniformly distributed throughout the length of the fiber. As all three solutions were being ejected, the phosphate and calcium solution mixed and form calcium phosphate nanoparticles while the gelatine solution encapsulate the resultant nanoparticles and electrospins from the needle tip. For this setup, the outermost channel is the gelatine solution, the intermediate channel contains calcium solution and the central channel contains phosphate solution. In an interesting demonstration on possible uses of coaxial nozzle in electrospinning, Panzavolta et al (2016) prepared calcium phosphate nanoparticles inside gelatine nanofibers through a triaxial needle. These include initiation and facilitation of electrospinning, controlling fiber quality, creating hollow fibers and reducing fiber diameter. However, the coaxial nozzle design has many other uses in electrospinning and the production of fibers. Coaxial nozzle, where the nozzle comprises of an inner and outer orifice, is often associated with electrospinning core-shell fibers.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |