It is usually assumed that for coaxial electrospinning, the shell fluids must be electrospinnable [25, 26]. However, our group has successfully developed a modified process, in which un-spinnable solutions can be used as shell fluids [14, 15]. For these processes to proceed successfully, the shell-to-core flow rate ratio is a key parameter. Here, we found that a shell-to-core Selleck AZD6244 flow rate ratio of 2:3 (shell 0.4, core 0.6 mL h−1) resulted in an irregular morphology where numerous spindles and beads were visible along

the nanofibers, as depicted in Figure 2f. To ameliorate this problem, a series of optimization experiments were performed. These led us to select shell and core flow rates of 0.3 and 0.7 mL h−1, respectively. The influence of PVC coating Based on our

previous studies [27], it was expected that the PVC coating would lead to a more efficient electrospinning process. An experiment was designed to investigate this hypothesis, as shown in Figure 3a,b,c. Two separate spinnerets coated with PVC tubing (inner diameter 1.0 mm) were arranged in parallel at a distance of 12 mm apart. One was supplied with the shell fluid and the other with the core fluid. A typical image of the electrospinning process under an applied voltage of 15 kV and a flow rate of 1.0 mL h−1 is exhibited in Figure 3b. Similarly, two uncoated stainless steel spinnerets (inner diameter 1.0 mm) were arranged under the same conditions, and typical results are given in Figure 3c. Figure 3 Investigation of how the PVC-coated spinneret affects electrospinning. (a) The experimental setup, (b) electrospinning with two PVC-coated spinnerets (inner diameter 1.0 mm), (c) spinning with two

LY2109761 datasheet stainless steel spinnerets (inner diameter 1.0 mm), and (d) a schematic diagram illustrating the interfacial tensions between the sheath fluid Microtubule Associated inhibitor and the spinneret. The sheath fluid is shown on the left and the core fluid on the right in (b) and (c). From a comparison of Figure 3b,c, a number of differences are clear: (i) when PVC-coated spinnerets were used, both fluids had a larger deflection angle than when the spinnerets were uncoated – for the shell fluid 47° > 25° and for the core 19° > 15°, (ii) the Taylor cones from the PVC-coated spinnerets are smaller than those from the metal spinneret, and (iii) the lengths of the straight fluid jets with the PVC-coated spinneret case are shorter than those using the metal spinneret, 9 mm < 10 mm (shell) and 6 mm < 8 mm (core). These results suggest that the PVC-coated spinneret conveys the electrical energy to the working fluids more effectively than the purely metal spinneret. This results in electrospinning commencing more rapidly with a smaller Taylor cone, shorter straight fluid jet, earlier onset of the instability region, and stronger repulsion forces between the two parallel fluids. Since it is an antistatic polymer, PVC can effectively retard the loss of electrical energy to the atmosphere.