Electrospinning Nanofibers Having a Core-sheath Structure

Li and Xia fabricated hollow fifibers made of titania by coaxial electrospinning through a two capillary coaxial spinneret and subsequent extraction of mineral oil as well as calcination of the core, in 2004. This group solved the instability problem by coelectrospinning two immiscible solutions, followed by gelation (or crosslinking) and stabilization of the sheath. In this work, an ethanol solution containing a solegel precursor, an acid catalyst, and a polymer was loaded into the sheath capillary, while heavy mineral oil was loaded into the core capillary. When the correct viscosities and rates of hydrolysis were achieved as stable bicomponents, a Taylor cone was formed, resulting in a stable coaxial jet. One of the major obstacles involved in the formation of core-sheath or hollow nanofifibers is the instability of the core. With the addition of a solegel precursor, gelation in the outer surface of the sheath during the spinning process prevented structural breakdown and resulted in fifibers with a stable morphology. Hollow fifibers could be obtained by extracting the mineral oil core with a solvent such as octane. As shown in Fig. 5.8A, the setup for