36 kPa). When THF/DMF ratio was less than 1:2 (v/v), beaded nanofibers with a rough surface were produced, while the quantity of beads was less than that of nanofibers from larger THF/DMF ratios. As discussed before, when THF/DMF ratio was 1:1 (v/v), bead-free grooved nanofibers were obtained from 10% (w/v) PS solutions (Figures 2A and 5). Figure
6 SEM pictures CX-5461 in vivo of nanofibers and their surfaces fabricated by electrospinning 10% ( w / v ) PS solutions with various THF/DMF ratios. (A, B) 6:0, (C, D) 5:1, (E, F) 4:1, (G, H) 3:1, (I, J) 2:1, (K, L) 0:6, (M, N) 1:5, (O, P) 1:4, (Q, R) 1:3, and (S, T) 1:2, v/v. RH 60%, collecting distance 15 cm, feeding rate 1.5 ml/h, and applied voltage 12 kV. Figure 7 Electrospun fibers and formation mechanism. (A, B, C) Representative images of fibers electrospun from 10% (w/v) PS solution (THF/DMF ratio 4:1 v/v). selleck compound RH 60%, collecting distance 15 cm, feeding rate 1.5 ml/h,
and applied voltage 12 kV. (D) Formation mechanism of single grooved texture. Inspired by the cues from the electrospinning of 10% (w/v) PS solutions, 20% (w/v) PS solutions with various THF/DMF ratios were electrospun under the lowest applied voltage (5 kV). Therefore, fibers with insufficient elongation were find more expected to be obtained. It should be mentioned here that the process was unstable because the applied voltage was not high enough, so a glass rod had to be used to clean the tip of the needle and keep the setup working continuously. Interestingly, small droplets connected to coarse fibers can be produced from some of the solutions (THF/DMF ratios, 5:1, 2:1, 1:1, 1:2, 1:5 v/v), demonstrating the formation mechanism of grooved texture.
The typical morphologies Calpain of the droplets and fibers are illustrated in Figure 8 and summarized in Table 1. When THF/DMF ratio was 5:1, numerous irregularly shaped pores in diameter of approximately 2 μm were found on the droplet surface, and the obtained fibers had a single grooved texture. In addition, there was a coarse fiber connected to the droplet, which has a diameter of 50 μm at the connection (exhibiting a grooved texture), while the diameter decreased to approximately 18 μm at the end of the coarse fiber. In this case, we can confirm that there were many large voids formed around the initial jet, so it is reasonable to assume that the formation of grooved texture should be attributed to elongation of large voids during electrospinning. Similarly, when THF/DMF ratio was 2:1, the coarse fiber with a diameter of 70 μm had a grooved texture, and the diameter decreased to approximately 20 μm at the end of the fiber. Even though no voids existed on the droplet surface, elongated voids (groove) presented on the surface of the coarse fiber, and all the resultant fibers were single grooved, which can also validate the aforementioned formation mechanism.