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

solutions to the needle tip at a feed rate of 1.6~2.0 ml/h. A high electrospinning voltage was applied
between the needle and ground collector using a high voltage power supply (BGG6-358,
BMEICO.LTD, China). The applied voltage was between 16 and 20KV. The electric field generated
by the surface charge caused the solution drop at the tip of the needle to distort into a Taylor cone.
2.4 Characterization of collagen-blended TPU nanofibers
The morphologies and diameters of the nanofibers electrospunned by pure and different weight
ratio concentration of TPU to collagen were determined with SEM (JEOL, JSM-5600, Japan) at a
accelerated voltage of 15KV. The diameter range of the fabricated nanofibers was measured based on
the SEM images using an image visualization software ImageJ 1.34s (National Institutes of Health,
USA).
Surface chemistry analysis of the electrospun scaffolds were also analyzed using X-ray
photoelectron spectroscopy (XPS) (Escalab 250; Thermo Scientific Electron, East Grinstead, UK)
equipped with Mg Kα at 1,486.6 eV and 150W power at the anode. A survy scan spectrum was taken
and the surface elemental compositions relative to carbon were calculated from the peak height with a
correction for atomic sensitivity.
Surface propeties of the nanofibers were examined using a a Nanoscope Ⅳ atomic-force
microscope (Digital Instruments), in the tapping mode and expressed as height and phase images.
2.5 Contact angle measurement
The electrospun mats made from pure TPU and TPU/collagen were characterized by the water
contact angle measurement to find the effect of addition of collagen on the hydrophicity of the
materials. The images of the droplet on the membrane were visualized through the image
analyzer(OCA40, Datephysics Co, German) and the angles between the water droplet and the surface
were measured. The measurement used distilled water as the reference liquid and was automatically
dropped onto the electrospun mats. To confirm the uniform distribution of blend nanofiber mats, the
contact angle was measured 3 times from different positions on each mat and an averge value was
calculated by statistical method.
2.6 The porosity of electrospun mats
The electrospun mats of TPU/collagen with different blend ratio at a concentration of 8wt%. The
thickness of the nanofiber mesh was measured with a micrometer (Shanghai, China). The apprent
density and porosity were calculated accroding to the following equations [26]:
Apparent density of nanofiber mats(g/cm 3 )=
Mass of nanofibrous mast (g)
2
Thickness of nanofibrous mats (cm) × Nanofiber mats area (cm )
Porosity of nanofiber mats (%)=
3
Naonfiber mats apparent density (g/cm )
) × 100%
3
bulk density fo raw TPU/collagen (g/cm )
2.6 FTIR spectra
Electrospun TPU nanofibers, collagen nanofiber and TPU/collagen with different weight ratios
were prepared for the FTIR test on AVATAR 380 FTIR instrument (Thermo Electron, Waltham, MA).
All spectra were recorded by an absorption mode in the wave length range of 4000-500 cm -1 .
2.7 Mechanical measurement
Mechanical measurements were carried out by applying tensile test loads to samples which were
prepared from electrospun ultra fine non-woven fiber mats. The specimens were electrospun with
different blend ratios of collagen to TPU (0:1, 1:3, 1:1, 3:1). In this study, the test was performed in
ambient temperature at 20 ℃ and relative humidity of 65%. Four specimens of each sample were
prepared according to the method described by Huang et al [21]. First, a white paper was cut into
templates with a planner dimension of width × gauge length=10mm×30mm and then double side tapes
were glued onto the top and bottom areas of one side. Secondly, the aluminum foil was carefully
scraped off and single side tapes were applied onto the griping areas as end-tabs. Finally, the resulting
specims were conducted on a commercial materials testing machine(H5K, Hounsfield, England) with
a load cell of 10N, and the elongation speed is 10mm/min.
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