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Outer fluid
Inner fluid
(b)
(a)
Compound Ta ylor cone
100 nm
Coaxial jet
V
High-voltage
power supply
500 nm
Collector
FIGURE 23.3
(See color insert.) (a) Setup for coaxial electrospinning for the fabrication of core-shell nanoibers. (b) SEM
images of an array of hollow anatase TiO 2 nanotubes. (From Feng, C. et al., Sep. Purif. Technol. , 102, 118, 2013.)
23.2.1 Technological Advances in Electrospinning—Core-Shell and Hollow Fibers
Technological advances in electrospinning allow the fabrication of core-shell and hollow
ibers of polymers, ceramics, and composites for water puriication and other applica-
tions. 18-20 Figure 23.3a shows a schematic of the spinneret needed for coaxial electrospin-
ning to fabricate core-shell and hollow nanoibers. The core solution is fed through the
inner spinneret and shell solution through the outer one (to have core-shell geometry
for ibers). For fabricating hollow ibers, the core solution through the inner spinneret is
usually mineral oil. The low rate of the solutions must be carefully controlled to get the
core-sheath or hollow morphology for the ibers. Figure 23.3b shows a scanning electron
microscopic (SEM) image of the hollow ibers (by removing the mineral oil at the core by
treatment with hexane) fabricated by McCann et al. 21
Yet another modiication in electrospinning to have structural anisotropy for the ibers
is the multiluidic compound jet electrospinning technique (Figure 23.4a). Several metal-
lic capillaries (with gaps between them) were inserted into a plastic syringe, and two
Inner fluid
Outer fluid
(a)
(b)
FIGURE 23.4
(See color insert.) (a) Schematic of the multichannel coaxial electrospinning system. (b) Cross-sectional SEM
images of hollow ibers with two, three, four, and ive channels. Scale bars in all the images are 100 nm. (From
Feng, C. et al., Sep. Purif. Technol. , 102, 118, 2013.)
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