Electrospinning-induced preferred dipole orientation in PVDF fibers
Tingping Lei1, Lingke Yu2, Gaofeng Zheng2, Lingyun Wang2, Dezhi Wu2,3 and Daoheng Sun†,2
1
Department of Mechanical and Electrical Engineering, Huaqiao University, Xiamen 361021, China
2
Department of Mechanical and Electrical Engineering, Xiamen University, Xiamen 361005, China
3
Shenzhen Research Institute of Xiamen University, Shenzhen 518057, China
†
Corresponding author: sundh@xmu.edu.cn
1 Stability test of the device
A preliminary study of the stability of the device was performed on untreated electrospun fiber mat under
continuous input pressure of 0.2 MPa at a constant frequency of 3 Hz. The output voltage was recorded
every other 50 s for 1 h based on the transmission rate and storing capacity of the flash memory disk, and
the result is shown in Fig. S1, which shows an average degeneration of c.a. 13.8%.
Output voltage (mV)
200
100
0
-100
-200
0
300
600
900
1200
1500
1800
Time (sec)
Fig. S1 Stability test of the device performed on untreated electrospun fiber mat under continuous input
pressure of 0.2 MPa at a constant frequency of 3 Hz.
2
Morphology observation of electrospun fiber mats before and after cycling test
SEM images of electrospun samples before and after extensive cycling tests are shown in Fig. S2. It
seems there are some little differences after cycling tests but may also arise from the difficulty in
transferring the samples after they were attached on the aluminum tapes.
(a)
(b)
(c)
(d)
Fig. S2 SEM images of electrospun fiber mats before (a, c) and after (b, d) extensive cycling tests.
Random and aligned fiber mats for (a, b) and (c, d), respectively.
3 Morphologies and polymorphisms of randomly distributed fibers electrospun from
different solution systems
Fig. S3 shows SEM images of PVDF fibers by conventional far-field electrospinning (FFES) from 16 wt%
PVDF solutions, with NMP and acetone volume ratios (VNMP/Vacetone) at 2/8, 3/7, 4/6, and 6/4 (VNMP/Vacetone = 5/5
described in the manuscript ). It can be seen that with increasing NMP ratio fiber diameter decreases in total.
Typical IR spectra of fiber mats from VNMP/Vacetone = 2/8, 3/7, 4/6, 5/5, and 6/4 are plotted in Fig. S4(a), and the
calculated fraction of β-phase of 5 samples for each ratio is shown in Fig. S4(b).
(a)
(b)
(c)
(d)
Fig. S3 SEM images of electrospun fibers produced from 16 wt% PVDF solutions, with NMP and acetone volume
ratios (VNMP/Vacetone) at 2/8, 3/7, 4/6, and 6/4, corresponding to “a”, “b”, “c”, and “d”, respectively. The polymer
solution flow rate, applied voltage, and the tip-to-collector are 60 μL/hr, 7.5 kV, and 10 cm, respectively.
100.0
(b)


 





 
 


(a)
F() (%)
Absorbance
97.5
a
b
c
d
e
1200
1000
800
c
d
a
95.0
e
b
92.5
600
90.0
400
-1
Wave number (cm )
2
4
6
NMP (V-mL) in 10-mL NMP/acetone mixtures
Fig. S4 (a) Typical infrared spectra and (b) calculated fractions of β-phase of electrospun fibers produced from 16
wt% PVDF solutions, with NMP and acetone ratios (VNMP/Vacetone) at 2/8, 3/7, 4/6, 5/5, and 6/4 as labeled with “a”,
“b”, “c”, “d”, and “e”, respectively.
4 Morphologies and polymorphisms of randomly distributed fibers electrospun at
different applied voltage
Morphology and polymorphism of randomly distributed electrospun fibers from baseline system (16 wt%,
VNMP/Vacetone = 5/5) with varying applied voltages from 4 to 11kV are depicted in Fig. S5 and Fig. S6,
respectively. It is found that the fraction of β-phase is very high for all samples (≥95%) and the influence of
applied electrical field on the formation of β-phase is not significant.
(a)
(b)
(c)
(d)
(e)
(f)
(g)
(h)
Fig. S5 SEM images of electrospun fibers at different applied voltages: a, b, c, d, e, f, g and h, corresponding to 4, 5,
6, 7, 8, 9, 10, and 11 kV, respectively. The polymer solution flow rate and the tip-to-collector are 60 μL/hr and 10 cm,
respectively.




      

Absorbance
A b so rb an ce
h
g
f
h
g
f
e
d
c
b
a
e
d
c
b
a
1400
1200
1000
800
600
400
-1
)
W a v e nwave
u m b number
e r ( c m (cm
)
-1
Fig. S6 Effect of applied voltage on the IR spectra
of number
electrospun
a, b, c, d, e, f, g and h, corresponding to 4, 5,
wave
(cm-1fibers:
)
6, 7, 8, 9, 10, and 11 kV, respectively.
5 Fiber population vs. diameter
The fiber diameter of each sample was measured from SEM images using ImageJ, and fiber population vs.
diameter graphs are shown in Figs. (S7-S9).
(a)
(b)
40
30
10 μm
20
10
0
0
Diameter percentage (%)
Diameter percentage (%)
40
30
10 μm
10 μm
20
10
0
100 200 300 400 500 600 700 800
0 100 200 300 400 500 600 700 800 900
Diameter (nm)
Diameter (nm)
(c)
Diameter percentage (%)
40
30
10 μm
20
10
0
1000
2000
3000
4000
5000
6000
Diameter (nm)
Fig. S7 The size distribution of fibers electrospun from the ‘baseline’ polymer solution (16 wt%,
VNMP/Vacetone = 5/5) by electrospinning and forcespinning as mentioned in Fig. 2 in the manuscript.
(a)
(b)
40
Diameter percentage (%)
Diameter percentage (%)
40
30
20
10
0
0
30
20
10
0
400 800 1200 1600 2000 2400 2800 3200
0
500
(c)
1500
2000
(d)
40
Diameter percentage (%)
40
Diameter percentage (%)
1000
Diameter (nm)
Diameter (nm)
30
20
10
0
0
500
1000
1500
30
20
10
0
2000
0
500
1000
1500
2000
Diameter (nm)
Diameter (nm)
Fig. S8 The size distribution of fibers electrospun from 16 wt% PVDF solutions, with NMP and acetone
volume ratios (VNMP/Vacetone) at 2/8, 3/7, 4/6, and 6/4, corresponding to “a”, “b”, “c”, and “d”, respectively,
as mentioned in Fig. S3 in supporting information.
(a)
(b)
40
Diameter percentage (%)
Diameter percentage (%)
40
30
20
10
0
0
30
20
10
0
400 800 1200 1600 2000 2400 2800 3200
0
500
(c)
1500
2000
(d)
40
Diameter percentage (%)
40
Diameter percentage (%)
1000
Diameter (nm)
Diameter (nm)
30
20
10
0
0
500
1000
1500
Diameter (nm)
2000
30
20
10
0
0
500
1000
Diameter (nm)
1500
2000
(e)
(f)
40
Diameter percentage (%)
Diameter percentage (%)
40
30
20
10
0
30
20
10
0
200 400 600 800 1000 1200 1400 1600
Diameter (nm)
(g)
Diameter (nm)
(h)
40
Diameter percentage (%)
40
Diameter percentage (%)
200 400 600 800 1000 1200 1400 1600
30
20
10
0
250 500 750 1000 1250 1500 1750 2000 2250
Diameter (nm)
30
20
10
0
250 500 750 1000 1250 1500 1750 2000
Diameter (nm)
Fig. S9 The size distribution of electrospun fibers under different applied voltages: a, b, c, d, e, f, g and h,
corresponding to 4, 5, 6, 7, 8, 9, 10, and 11 kV, respectively, as mentioned in Fig. S5 in supporting
information.