Workshop proceeding - final.pdf - Faculty of Information and ...

Blend nanofiber diameters distribution of different blend ratios were further determined and the
results were shown in Fig.2. Nanofiber diameters of every weight ratios were calculated from the
diameter of 100 nanofibers each sample which were directly measured from SEM photographs. From
numerical statement of average diameters and standard deviation we can see that the fiber diameter
gradually deceased with increasing collagen content in the blend. This phenomenon could be
explained as the conductivity increase of the blend solution. It has been known that in electrospinning,
the force that causes the stretching of the solution is due to the repulsive forces between the charges on
the electrospinning jet[29]. Collagen is typical amphiprotic macromolecule electrolyte. When collagen
was affiliated, more ions were formed in the blend solution. So a higher discharge density could be
carried by the electrospinning jet. The conductivity of the solution could be increased by the addition
of ions. On the other hand, the increased charge carried by the solution will increase the stretching of
the solution. And the increased in the stretching of the solution also could tend to yield fibers of
smaller diameter.
In order to investigate the factor of solution concentration, we selected one weight ratio (80/20,
TPU/collagen) to prepare this blend solution with six different concentrations.
Fig 1 and 2 SEM images of nanofiber mats at concentration of 6wt% with different blend ratios of
TPU to Collagen(T/C) and their fiber diameter distribution
Then the mixed solutions were subjected to the electrospinning process under the same
processing condition. Fig.3 shows SEM images of TPU/collagen fibers with the concentration which
varied from 1.5% to 9% at equal interval. Their fiber diameter distributions were calculated in the
same method and the results were shown in Fig.4. From the SEM images we could observe that the
smooth fibers could be obtained when the concentrations of the solutions were located between 4.5%
and 7.5%. At the same time, we could find that either the concentrations were too low or too high,
more beads structure could appear. It is established that chain entanglements in the solution plays an
important role in the fiber diameter and morphology. The increase of the solution concentration will
result in great polymer chain entanglements. Thus, if the concentration is to low, bead-only structure
will be produced due to a lack of chain entanglements in the solution[30]. On the contrary, if the
concentration is too high, that will make it very difficult to pump the solution through the syringe
needle. Morevoer, when the concentration is too high, the solutions may dries at the tip of the needle
before the electrospinning can be initiated.
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