1
Abstract
Formation of superhydrophobic materials from polystyrene will provide a material that is
able to separate miniscule amounts of water from organic fluids that normally would not be able
to be separated by mechanical means. By using polystyrene, not only is cost reduced due to the
large amount of polystyrene available, but the problem of finding an efficient method of
recycling polystyrene is also resolved. Samples were created using varying electrospinning
conditions, ranging from five weight percent polystyrene in dimethylformimide to thirty weight
percent. Electrospinning conditions were also varied between ten and thirty kilovolts. Samples
were tested for water contact angle as well as under a scanning electron microscope to determine
fiber diameter and structure. Samples were defined as superhydrophobic if the water contact
angle was greater than 150°. Superhydrophobic nanofibers were achieved using polystyrene by
ranging electrospinning conditions between ten and twenty weight percent polystyrene in
dimethylformimide and ranging the voltage between ten and twenty kilovolts.
2
Table of Contents
Executive Summary ................................................................................................................................ 4
Introduction............................................................................................................................................. 6
Procedure ................................................................................................................................................ 7
Discussion/Results ................................................................................................................................ 10
Conclusion ............................................................................................................................................ 20
Bibliography ......................................................................................................................................... 22
Appendix A: Water Contact Angle Raw Data ........................................................................................ 23
3
Executive Summary
The goal of this project was to develop superhydrophobic nanofibers from polystyrene
via electrospinning. Formation of superhydrophobic nanofibers is currently a growing field for
developing material for water and organic filters. These nanofibers allow for the separation of
miniscule amounts of water from organic fluids that are not able to be separated by mechanical
means, such as in a centrifuge or gravity separation. Use of polystyrene to generate
superhydrophobic materials is not only cost effective due to the low cost and availability of
polystyrene, but polystyrene can be recycled to form the superhydrophobic nanofibers. This
allows for green engineering of filters using the superhydrophobic polystyrene nanofibers.
Superhydrophobic nanofibers were able to be generated from polystyrene. Nanofibers
were produced from polymer solutions with a weight percentage of polystyrene to
dimethylformamide between ten and twenty pumped at a volumetric flow rate of one milliliter
per hour electrospun at a voltage between twenty and thirty kilovolts. Supherhydrophobic
nanofibers were produced at four total sets of conditions: 10wt% and 20kv, 10wt% and 30kV,
20wt% and 20kV, and 20wt% and 30kV. Water contact angles observed were 154.8±7.03°,
157.0±3.23°, and 154.1±4.18° for 10wt% and 20kV, 10wt% and 30kV, and 20wt% and 20kV,
respectively. Samples spun at 20wt% and 30kV were unable to be tested for water contact angle
due to the inability to determine the droplet on the surface of the material using the Krűss Drop
Shape Analyzer model DSA20E. Sample diameters ranged depending on electrospinning
conditions, and were measured with a scanning electron microscope. These ranges were 200500nm, 300-500nm, 500-900nm, and 1100-1700nm for 10wt% and 20kV, 10wt% and 30kV,
20wt% and 20kV, and 20wt% and 30kV, respectively. All samples were beaded nanofibers
except for samples spun at 20wt% and 30kV which were smooth nanofibers. Mass per unit area
was determined for each sample to determine the amount of polystyrene necessary to develop
superhydrophobic properties. These values were measured as 28.00±5.11 g/m 2, 35.56±3.08g/m2 ,
25.33±5.11 g/m2, and 37.33±4.36g/m2 for 10wt% and 20kV, 10wt% and 30kV, 20wt% and
20kV, and 20wt% and 30kV, respectively.
The optimal conditions for forming superhydrophobic nanofibers determined from this
research were a volumetric flow rate of one milliliter per hour, a distance of twenty centimeters
between the needle and ground, a solution weight percent of polystyrene to dimethylformamide
of twenty weight percent and a voltage of twenty kilovolts. These conditions allowed for the
4
formation of superhydrophobic materials while minimizing the amount of polystyrene that was
required to be spun.
During this research I further developed my skills with working with bench scale testing
and design of experiments. I also learned a new method for developing new materials. I furthered
my experience with being able to start with a wide goal and over the course of the project narrow
the methods to obtain the goal set forth originally by the project.
Further research is suggested in determining a cross-linking agent that can be spun with
the polystyrene to develop a cross linked superhydrophobic nanofiber network. A possible cross
linking agent to be further researched with polystyrene is divinyl benzene. It is also suggested for
further research into water droplet tilt angle testing and water droplet velocity testing on the
superhydrophobic polystyrene nanofibers.
5
Introduction
Formation of superhydrophobic nanofibers is currently a growing field for developing
material for water and organic filters. Fibers become superhydrophobic by creating increased
surface area (Kim, 2008). Spinning samples to nanofiber diameters increases the surface
roughness, which can also be further modified by spinning material that generates nanofibers,
beaded nanofibers, or nanospheres (Kim, 2008). These nanofibers allow for the separation of
miniscule amounts of water from organic fluids that are not able to be separated by mechanical
means, such as in a centrifuge or gravity separation (Kim, 2008). These nanofibers create a
surface area for the water molecules to collect while allowing for the organic fluids to pass
through.
Polystyrene was initially chosen to be tested due to its natural hydrophobic properties.
Use of polystyrene to generate superhydrophobic materials is not only cost effective due to the
low cost and availability of polystyrene, but polystyrene can be recycled to form the
superhydrophobic nanofibers. This allows for green engineering of filters using the
superhydrophobic nanofibers. The superhydrophobic nanofibers are able to be formed using an
electrospinning process.
The goal of the research described in this report was to determine the conditions
necessary to electrospin superhydrophobic polystyrene nanofibers. The conditions varied
included voltage, solution weight percent of polystyrene in dimethylformimide, and the solution
flow rate while spinning.
6
Procedure
The electrospinning of the polystyrene first involved creating a solution of polystyrene in
dimethylformamide. Polystyrene used during this research came from clean recycled materials to
simulate the ability to form superhydrophobic nanofibers from recycled polystyrene.
Dimethylformimide was used to dissolve polystyrene as described in previous work (Minsung
Kang, 2008). The weight percent of polystyrene was varied between five and twenty percent. A
five milliliter luer locker syringe was then filled with the solution of polystyrene. The syringe
was then placed in a syringe pump that controlled the flow rate between one milliliter per hour
and five milliliter per hour. The sample was spun through a twenty one gauge syringe connected
to a voltage source. The voltage source was used to control the applied voltage between ten
kilovolts and thirty kilovolts. Two sample slides were placed on a formed tray of aluminum that
was placed at a distance of twenty centimeters from the tip of the syringe. This distance was held
constant throughout all experiments. The electrospinning setup is shown below in Figure 1.
Figure 1: Electrospinning Set-up
7
Once the samples were spun, multiple tests were conducted to develop a list of properties
for each sample that was spun. Testing included water contact angle, surface structure of the
fibers, mass per area of fibers, and percent spun from solution.
The contact angle of water was measured on a Krűss Drop Shape Analyzer model
DSA20E. The samples that were tested on the DSA20E were tested using multiple drop sizes.
The drops size ranged from one micro-liter to five micro-liter. Drop size was varied to show if
the water contact angle of the water droplet decreased with droplet size. The DSA20E is shown
below in Figure 2.
Figure 2: DSA20E
Samples were tested for surface structure via Scanning Electron Microscope (SEM). This
was conducted to determine whether the samples spun were nanofibers, beaded nanofibers, or
electrosprayed nanospheres. The range of fiber size was also collected for each sample from the
SEM.
The samples were also tested for mass per unit area on the sample slides. These values
were calculated by determining the amount of polystyrene spun onto the slide divided by the
8
surface area of the sample slide. The surface area of the sample slide was calculated by
multiplying the width of the slide by the length of the slide. The amount of polystyrene spun onto
the sample slide was calculated as the difference of the weight of the sample slide with spun
polystyrene and the weight of the sample slide without spun polystyrene. The percent of
polystyrene spun from the solution to the slide was also calculated as the ratio of the polystyrene
that was spun onto the sample slide divided by the total weight of polystyrene spun. This ratio is
defined as the efficiency of the electrospinning of a given sample during this research.
9
Discussion/Results
The goal of the testing of the electrospun polystyrene was to develop a nanofiber material
that held a water contact angle greater than 150°. Initial testing was conducted to determine a
range of voltages, flow rates, and solution concentrations for further testing. These initial
samples and their conditions are shown below in Table 1.
Table 1: Initial Testing Conditions
Sample
Voltage (kV)
Conc. (wt%)
Flow Rate (mL/hr)
Result
1
20
5
5
Wet Sample, No Fibers
2
20
5
1
No Fibers, No WCA
3
20
10
1
Fibers, WCA of 140.9±3.22
4
30
10
1
Fibers, WCA of 149.5±2.60
5
10
10
1
Dripped instead of spinning, voltage too low
Based upon these results, it was determined that a flow rate of 5ml/hr was too fast to
develop fibers of polystyrene and to allow enough time for the dimethylformamide to evaporate
from the polystyrene. It was also determined that a voltage of 10kV did not supply enough
electrical potential to form polystyrene nanofibers over the 20cm distance between the syringe
and the sample slides.
Further testing was conducted by making the solution flow rate constant at 1mL/hr,
varying the voltage between 20kV and 30kV, and varying the polystyrene concentration between
10wt% and 20wt%. At each of these conditions a total of four sample slides were evaluated for
water contact angle, surface structure, mass per area, and percent of polystyrene spun. The
samples and their conditions are shown below in Table 2.
10
Table 2: Sample Synthesis Conditions
Slide
1
1
2
2
3
3
4
4
5
5
6
6
7
7
8
8
Sample
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Voltage (kV)
20
20
20
20
30
30
30
30
20
20
20
20
30
30
30
30
Conc. (wt%)
10%
10%
10%
10%
10%
10%
10%
10%
20%
20%
20%
20%
20%
20%
20%
20%
Flow Rate
(mL/hr)
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
Water contact angles were tested on the DSA20E with droplet sizes varying from one to
five micro liters. Samplees E, M, N, O, and P, were unable to be tested for water contact angle
on the DSA20E either because the sample was damaged (E) or because the surface of the sample
(M, N, O, and P) was very rough due to large fiber size.
The average water contact angles and standard deviations for each testing condition are
shown below in Table 3 and Table 4, respectively.
WCA °s (AVG)
10wt% 20kV
10wt% 30kV
20wt% 20kV
Table 3: Water Contact Angle Averages
5μL
4μL
3μL
2μL
154.8
152.4
150.6
146.1
157.0
157.7
160.8
155.5
154.1
149.1
148.0
143.5
1.5μL
1μL
143.4
153.0
141.5
140.9
151.1
137.2
Table 4: Water Contact Angle Standard Deviations
WCA °s StDEV
5μL
4μL
3μL
2μL
1.5μL
1μL
10wt% 20kV
7.03
3.59
3.21
2.81
4.37
2.27
10wt% 30kV
3.23
1.93
5.59
5.16
3.17
0.87
20wt% 20kV
4.18
11.77
10.34
10.15
11.65
9.07
11
Below are the graphs of the water contact angle vs. droplet size. Figure 3 represents the
testing condition 10wt% 20kV, Figure 4 represents the testing condition 10wt% 30kV, and
Figure 5 represents the testing condition 20wt% 20kV.
Contact Angle (degrees)
10wt% 20kV Droplet Size vs. Contact Angle
175.0
165.0
155.0
145.0
135.0
125.0
0
1
2
3
4
5
6
5
6
Droplet Size (m icroliter)
Figure 3: WCA vs. Droplet Size, 10wt% 20kV
Contact Angle (degrees)
10wt% 30kV Droplet Size vs. Contact Angle
175.0
165.0
155.0
145.0
135.0
125.0
0
1
2
3
4
Droplet Size (m icroliter)
Figure 4: WCA vs. Droplet Size, 10wt% 30kV
12
Contact Angle (degrees)
20wt% 20kV Droplet Size vs. Contact Angle
175.0
165.0
155.0
145.0
135.0
125.0
0
1
2
3
4
5
6
Droplet size (m icroliter)
Figure 5: WCA vs. Droplet Size, 20wt% 20kV
From the figures above, it is observed that the trend of the water contact angle decreases
with the decrease in droplet size. This testing was done to view how the superhydrophobic
properties of the nanofibers depend upon the water droplet size. With smaller droplet sizes, lower
water contact angles are observed. This is due to the surface energy of the water droplet lowering
with droplet size, allowing for the water droplet to sink into the fiber matrix due to the porosity ,
and of the fiber matrix. This is also shown below in Figures 6,7, and 8. The SEM images show
larger pore sizes on samples spun at 20wt% 20kV, which in Figure 5 the water contact angle
dropped at a faster rate. This is compared to samples spun at 10wt% 20kVand 10wt% 30kV
having water contact angles that drop slower with droplet size when the pore sizes observed in
Figures 6 and 7 are smaller.
A statistical analysis of regression was performed to determine the t-Stat values and Pvalues to determine if there was statistical correlation between the samples tested for water
contact angle. The t-Stat values and P-values are shown below in Table 5 and Table 6,
respectively.
13
Table 5: t-Stat Analysis
t-Stat
wt%
kV
5μL
-0.30159 0.914039
4μL
-0.9798
1.559823
3μL
-0.9798
1.559823
2μL
-0.81782 2.954591
1.5μL
-0.5309
2.759408
1μL
-1.46119 3.97479
Table 6: P-value Analysis
P-Value wt%
kV
5μL
0.765565 0.369788
4μL
0.336957 0.131892
3μL
0.336957 0.131892
2μL
0.421506 0.006911
1.5μL
0.600367 0.010908
1μL
0.156933 0.000562
Statistical significance was observed if the t-Stat value is greater than one while the Pvalue is less than 0.05 indicating 95% confidence. Values that showed this are highlighted in
yellow in Tables 5 and 6, respectively. This statistical model shows that voltage played the
largest role in determining water contact angle.
A second regression analysis was performed by removing the weight percent affect on
the statistics. The weight percent dependence in the analysis was removed due to the t-Stat
values being below one. The results from the second regression analysis are shown below in
Table 7.
Table 7: Second Regression Analysis
kV
t-Stat
P-Value
5μL
4μL
3μL
2μL
1.5μL
1μL
1.253
0.221
2.368
0.025
4.041
0.0004
3.909
0.0006
3.544
0.002
5.314
1.66E-05
This second analysis once again supports that the dominating factor on the water contact
angle is the voltage that the sample is electrospun at. A further t-test analysis was performed to
discern the large standard deviations between samples and droplet size. These values are shown
below in Table 8, 9, and 10 for samples 10wt% 20kV, 10wt% 30kV, and 20wt% 20kV,
respectively.
14
10wt% 20kV
5μL
4μL
3μL
2μL
1.5μL
1μL
Table 8: 10wt% 20kV t-Test Analysis
SE
n
mean
stdev
Mean
9
9
9
9
9
9
154.84
152.38
150.57
146.1
143.39
140.9
7.03
3.59
3.21
2.81
4.37
2.27
2.34
1.2
1.07
0.94
1.46
0.76
95%CI
(149.44,160.25)
(149.62,155.14)
(148.10, 153.03)
(143.94,148.26)
(140.03,146.75)
(139.16,142.65)
Table 9: 10wt% 30kV t-Test Analysis
10wt% 30kV
5μL
4μL
3μL
2μL
1.5μL
1μL
n
mean
stdev
SE Mean
95%CI
9
9
9
9
9
9
157.03
157.67
160.81
155.53
153.03
151.06
3.23
1.93
5.59
5.16
3.17
0.87
1.08
0.64
1.86
1.72
1.06
0.29
(154.55,159.52)
(156.18,159.15)
(156.51,165.11)
(151.57,159.50)
(150.6,155.47)
(150.39,151.72)
Table 10: 20wt% 20kV t-Test Analysis
20wt% 20kV
5μL
4μL
3μL
2μL
1.5μL
1μL
n
mean
stdev
SE Mean
95%CI
9
9
9
9
9
9
154.12
149.06
148.03
143.49
141.53
137.17
4.18
11.77
10.34
10.15
11.65
9.07
1.39
3.92
3.45
3.38
3.88
3.02
(150.91,157.34)
(140.01,158.11)
(140.09,155.98)
(135.68,151.29)
(132.58,150.49)
(130.20,144.14)
Comparing the standard error mean we can determine the accuracy of the water contact
angle for each sample for each water droplet size. Table 8 shows that for the 10wt% 20kV
sample the largest standard error mean is at a droplet size of 5μL with a value of 2.34.
Comparing this to the raw data shown in Appendix A it is visible that one sample slide was
slightly undervalued compared to other sample slides. Table 9 shows that the 10wt% 30kV
samples were all within reasonable values of each other. Table 9 shows that at 20wt% 20kV the
standard error mean is above 3 for multiple droplet sizes. Comparing this to the raw data shown
in Appendix A it is visible that one sample slide was slightly undervalued compared to other
sample slides.
15
From these regressions, equations to determine water contact angle for a given voltage
and drop size were determined. These equations are shown below for calculating the water
contact angle for 5µL, 4µL, 3µL, 2µL, 1.5µL, and 1 in Equations 1, 2, 3, 4, 5, and 6,
respectively.
Eqn 1:
Eqn 2:
Eqn 3:
Eqn 4:
Eqn 5:
Eqn 6:
For these equations, the water contact valuein degrees, y, is dependent upon the voltage
in kV, x.
From sample to sample, it is viewed that water contact angle generally increases with
higher voltages and with higher weight percent solutions. Water contact angle is generally
derived from the surface structure of the nanofibers. During electrospinning the structure of the
material can range between nanofibers, beaded nanofibers, or nanospheres. By increasing the
roughness of the surface structure of the material, greater contact angles and super-hydrophobic
properties are able to be obtained. Shown below are SEM images showing the surface structure
of different electrospinning conditions in Figures 6, 7, 8, and 9.
16
Figure 6: 10wt% 20kV
Figure 8: 20wt% 20kV
Figure 7: 10wt% 30kV
Figure 9: 20wt% 30kV
*Note that Figures 6 and 7 have a scale of 5μm, while Figure 8 has a scale of 10μm and Figure 9 has a
scale of 20μm*
From sample to sample, it is viewed that the surface roughness of the samples varies
dependent on the electrospinning conditions. Samples run at 10wt% 20kV, 10wt% 30kV, and
20wt% 20kV formed nanofibers and beaded nanofibers. Samples run at 20wt% 30kV formed
only nanofibers. Higher weight percent solutions and higher voltages resulted in higher diameter
samples, as shown in Table 11.
17
Condition
10wt% 20kV
10wt% 30kV
20wt% 20kV
20wt% 30kV
Table 11: Fiber Diameters
Diameter Average (nm)
332.7
435.3
668.0
1527.8
Diameter StDEV (nm)
134.2
66.8
157.2
127.8
Fibers spun at different conditions also showed different ranges for fiber diameters.
Samples spun at 10wt% 20kV showed a fiber diameter range from 200-500nm. Fibers spun at
10wt% 30kV showed a fiber diameter range from 300-500nm. Fibers spun at 20wt% 20kV
showed a fiber diameter range from 500-900nm. Fibers spun at 20wt% 30kV showed a fiber
diameter range from 1100-1700nm. A general trend is observed that as solution weight percent
increases fiber diameter increases. This can be explained as the higher amount of available
polystyrene causes there to be wider fibers formed. Another general trend is observed that as
voltage increases surface structure is varied. Lower voltages result in more beaded nanofibers
and nanospheres, while higher voltages result in smoother nanofibers or microfibers. This can be
explained as the higher energy potential forces the polystyrene to elongate, causing the fibers to
not collect in one area to form beads or nanospheres.
Samples were also tested to determine the mass of polystyrene per unit area, as well as to
determine the efficiency of the electrospinning. The efficiency of the electrospinning for the
samples spun during this research was defined as the ratio of the amount of polystyrene that was
spun onto the sample slide over the amount of polystyrene in the solution that was spun. The
mass per unit area for each sample is shown below in Table 12. The efficiency of the
electrospinning for each sample is shown below in Table 13.
18
Table 12: Mass Per Unit Area
Voltage (kV)
20
30
20
30
Voltage (kV)
20
30
20
30
Concentration (wt%)
10
10
20
20
Mass/Area (g/m 2)
28.000 ± 5.106
35.556 ± 3.079
25.333 ± 5.106
37.333 ± 4.355
Table 13: Electrospinning Efficiencies
Concentration (wt%)
Percent Spun (%)
10
11.41% ± 2.08%
10
14.49% ± 1.26%
20
13.54% ± 2.30%
20
14.89% ± 1.74%
In Table 12 it is shown that by increasing the voltage increases the mass per unit area.
This can be explained that due to the higher voltage the polystyrene is drawn to the sample slide
with greater energy. This is also shown due to the higher efficiency of the higher voltage samples
shown in Table 13.
19
Conclusion
Superhydrophobic nanofibers were able to be generated from polystyrene. The conditions
that allowed for formation of these nanofibers included varying the weight percent of
polystyrene to dimethylformamide between ten and twenty weight percent, a volumetric flow
rate of one milliliter per hour, and varying the voltage between twenty and thirty kilovolts.
Four total samples showed superhydrophobic properties, including 10wt% 20kv, 10wt%
30kV, 20wt% 20kV, and 20wt% 30kV. Samples spun at 10wt% and 20kV resulted in a contact
angle of 154.8±7.03°, a surface structure of beaded nanofibers ranging from 200-500ηm, and a
mass per unit area of 28.00±5.11 g/m2. Samples spun at 10wt% and 30kV resulted in a contact
angle of 157.0±3.23°, a surface structure of beaded nanofibers ranging from 300-500ηm, and a
mass per unit area of 35.56±3.08g/m 2. Samples spun at 20wt% and 20kV resulted in a contact
angle of 154.1±4.18°, a surface structure of beaded nanofibers ranging from 500-900ηm, and a
mass per unit area of 25.33±5.11 g/m2. Samples spun at 20wt% and 30kV in a surface structure
of nanofibers ranging from 1100-1700ηm, and a mass per unit area of 37.33±4.36g/m 2. Samples
spun at 20wt% and 30kV were unable to be tested for water contact angle due to the inability to
determine the droplet on the surface of the material using the Krűss Drop Shape Analyzer model
DSA20E.
The optimal conditions for forming superhydrophobic nanofibers determined from this
research were a volumetric flow rate of one milliliter per hour, a distance of twenty centimeters
between the needle and ground, a solution weight percent of polystyrene to dimethylformamide
of twenty weight percent and a voltage of twenty kilovolts. These conditions allowed for the
formation of superhydrophobic materials while minimizing the amount of polystyrene that was
required to be spun.
20
Further research is suggested in determining a cross-linking agent that can be spun with
the polystyrene to develop a cross linked superhydrophobic nanofiber network. A possible cross
linking agent to be further researched with polystyrene is divinyl benzene. Divinyl benzene is a
current cross linking agent used with polystyrene. Research will need to be conducted to
determine if the divinyl benzene will need to be spun with polystyrene or coated on the
nanofibers after they are electrospun. Curing conditions will also need to be researched.
It is also suggested for further research into water droplet tilt angle testing and water
droplet velocity testing on the superhydrophobic polystyrene nanofibers. These values can be
used to further determine physical properties of the materials spun as well as defining optimal
electrospinning conditions.
21
Bibliography
Kim, S. H. (2008). Fabrication of Superhydrophobic Surfaces. Journal of Adhesion Science and
Technology , 235-250.
Minsung Kang, R. J.-S.-J. (2008). Preparation of Superhydrophobic Polystyrene Membranes by
Electrospinning. Colloids and Surfaces A: Physicochem. Eng. Aspects , 411-414.
22
Appendix A: Water Contact Angle Raw Data
Sample
Slide
A
B
C
F
G
H
I
K
L
5μL
161.1
159.2
158.4
161.0
158.2
159.0
146.1
145.4
145.2
155.2
155.7
156.9
161.2
161.2
160.9
153.0
154.0
155.2
151.1
148.3
153.2
153.8
151.9
151
158.2
160
159.6
4μL
152.4
152.5
153.6
157.2
156.3
155.1
148.7
147.8
147.8
158.7
156.8
157.3
160.3
160.0
159.1
155.2
156.2
155.4
134.8
135
132.7
150.5
152.3
155.1
162
160.9
158.2
3μL
151.5
151.0
149.5
156.0
152.1
153.8
147.9
146.6
146.7
162.7
163.9
164.4
164.5
165.5
165.9
153.1
153.1
154.2
133.2
134.6
135.8
156.1
155.8
158.6
153.8
151.9
152.5
2μL
142.8
141.4
143.2
147.2
148.7
148.6
147.7
147.4
147.9
160.9
159.0
159.0
160.1
157.1
157.1
149.5
149.0
148.1
130
129.8
131.2
147.1
147.9
147.2
153.8
151.9
152.5
23
1.5μL
135.0
140.3
140.0
147.2
147.2
148.7
145.1
144.3
142.7
155.2
156.7
153.6
154.2
156.2
154.2
148.6
148.4
150.2
132.2
129.2
130.7
136.3
136.7
139.2
156.5
155.7
157.3
1μL
138.8
139.3
140.4
143.5
144.0
144.1
139.2
139.5
139.3
151.7
150.1
150.7
152.2
151.7
152.1
150.4
150.0
150.6
127.9
129.7
127.7
136.8
133.8
134.8
147.7
142.5
153.6