Biomedical Engineering Reference
In-Depth Information
Pieozoelectric characteristics of the samples.
Table 8.2
Sensitivity (mV N
-1
)
Sample
Input (N)
Output (mV)
A
4.44
130
29.25
B
3.33
140
42.00
C
3.56
135
37.97
D
4.44
107
24.08
E
3.56
135
37.97
F
3.33
140
42.00
G
4.44
105
23.63
H
4.44
50
11.25
β
ββ
β
ββ
A
E
F
B
C
D
G
H
0
10
20
30
10
50
0
10
20
30
10
50
(a)
(b)
2
θ°
2
θ°
Figure 8.11
X-ray diffraction patterns for sample sets (a) A-D and (b) E-H.
infrared (IR) spectroscopy, because the IR spectrum is very sensitive to crystal
modification as well as to chain and dipole orientations [25, 26]. Thus P(VDF-TrFE)
is the most appropriate piezoelectric polymer to elucidate the spontaneous dipole
switching during electrospinning by the IR spectroscopic method. P(VDF-TrFE)
(77/23) nanofibrous mat was prepared by electrospinning as shown in Figure 8.12.
The scanning electron microscope image of the electrospun nanofiber web is
illustrated in Figure 8.13a (right). The average fiber diameters are approximately
60-120 nmand the average preferential fiber orientation along the collector rotation
direction is also observed. The schematic of IR optics and sample geometry are
shown in Figure 8.14a. Figure 8.14b,c show the unit lattice of the ferroelectric crystal
phase of P(VDF-TrFE) and the relationship between the vibrational transition
moment and crystal unit axis for each vibrational symmetry species, respectively.
The FTIR spectra of the as-electrospun nanofiber webs measured with the parallel
and perpendicular polarized IR beamare illustrated in Figure 8.14d. The vibrational
bands assignment and its useful characteristics are listed in Table 8.3. From
Figure 8.14d, it is clear that A
1
and B
2
band absorptions are prominent in the
perpendicular polarized spectrum, whereas the B
1
band absorption is dominated
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