Supplementary Material
Bio-inspired Highly Hydrophobic Surface with Ecdysis Behavior Using an Organic Monolithic
Resin and Titanium Dioxide Photocatalyst
Munetoshi Sakai, Tomoya Kato, Norio Ishizuka, Akira Nakajima, Akira Fujishima.
1. Film thickness of a highly hydrophobic coating with surface restoration
The film thickness after surface restoration was approximately constant (Figure S1). The change in
film thickness was less than 0.25 m after three months, although testing was carried out on
different days than indicated in Figure 4. Therefore, the apparent film thickness was maintained. The
film thickness was measured using a micrometer (Figure S2). The measurement points were located
between three red markers. Highly hydrophobic coatings on the SUS substrate were formed as
膜厚変化
1.0
接触
160
0.75
■ TiO2: 0 Mass%
◆ TiO2: 3.1 ×10-5 Mass%
140
0.5
120
接触角 [ o]
[m]
change [m]
thickness
Amount of変化量
described in Figure 4.
0.25
0.0
-0.25
-0.5
-0.75
Rainfall fluctuation
TiO2
:0
TiO2: 3.1×10-5
(Yokohama District Meteorological Observatory)
Mass%
Mass%
-1.0
0
25
50 75 100 125 150
Elapsed
time [day]
経過時間
[d]
100
80
60
40
0
b)
Figure S2. Micrometer and the back of the SUS substrate. a) Micrometer and the evaluated
sample. b) Measurement points are located between red markers on the back of the SUS
substrate.
降水量の経日変化（横浜
20
Figure S1. Fluctuation of film thickness during outdoor testing.
a)
TiO2: 0
TiO2: 3.1
0
25
50 7
経過時
2. Function of the ultraviolet absorbing agent in the organic monolithic resin as TiO2
photocatalyst
Figure S3 shows the contact angles under an ultraviolet lamp. The UV intensity was 2 mW/cm2. In
this test, since there was no simulated rain, the self-restoration function was not generated. Moreover,
the evaluated samples were OMR-POF samples. The contact angles depend on the abundance of
TiO2 photocatalyst (ST-01). The diffuse reflectance spectrum of UV/VIS is shown in Figure S4.
When the organic monolithic resin contains TiO2 photocatalyst, the decrease in the contact angles
was slowest. Although TiO2 photocatalyst may absorb ultraviolet light, fluorine polymer could not
be decomposed. On the other hand, organic monolithic resin with more TiO2 photocatalyst quickly
appeared in the hydrophilic epoxy resin as a result of the decomposition of fluorine polymer.
160
Black light
TiO2 3.1×10-5 Mass%
Contact angle [ o]
140
UV Intensity 2 mW/cm2
120
100
80
Sample
60
40
20
TiO2 31×10-5 Mass%
Without TiO2
0
0
200
400
600
800
1000 1200 1400 1600
Irradiation time [h]
Figure S3. Contact angles under ultraviolet exposure. The UV intensity was 2 mW/cm2.
100
90
Reflectance [%]
80
ST-01
70
60
50
40
30
20
10
0
300
400
500
600
700
Wavelength [nm]
Figure S4. Diffuse reflectance spectrum of UV/VIS in TiO2 photocatalyst (ST-01).
3. Contact angles calculated from the Cassie function
Figure S5 shows a schematic diagram of the simple model of the contact angle in the organic
monolithic resin with TiO2 photocatalyst. The contact angle is calculated using the Cassie model [5].
Then, the contact angle of the organic monolithic resin with TiO2 photocatalyst was 148.8 when the
TiO2 photocatalyst was made superhydrophilic by applying ultraviolet light. On the other hand, the
contact angle of the organic monolithic resin without TiO2 photocatalyst was 150.3. Therefore,
incorporating TiO2 photocatalyst into the organic monolithic resin has an insignificant effect on the
contact angle.
Area of frame modified
by fluorine polymer
Frame
1- m m
Area of bared
TiO2 particles
Air
l
1- l
Porosity of organic monolithic resin: 80 % ⇒ l = 0.8
Maximum Mass % of TiO2 particles in organic monolithic resin: 5 % ⇒ m = 0.05
Here, when qa, qp and qf were the contact angle of air, fluorine polymer modified frame and
superhydrophilic TiO2 particle respectively, Cassie function in this model was described as follows.
Apparent contact angle q on the surface of the organic monolithic resin was calucurated, when qa, qp and
qf were putted 180, 0 and 110 degree respectively.
Figure S5. Schematic diagram of the simple model of the contact angle in an organic
monolithic resin with TiO2 photocatalyst. The Cassie model was used [5].
4. Phase separation between the mixture and the solvent
Figure S6 shows the phase separation between the mixture and various organic solvents. For the
cases of toluene and xylene, phase separation between the mixture and the solvent occurred quickly.
However, phase separation did not occur in the mixture with acetone.
Figure S6. Phase separation between the mixture and the solvent.
5. Coloring of the highly hydrophobic monolithic resin
Extra pigment was eliminated by washing the PEG. The discoloration of the dye did not appear
after 24 h (Figure S7). On the other hand, the hydrophobicity performance was similar to that in the
rubbing test.
White
Blue
Red
UV-VIS
Rate of Absorption
Discolored testing.
Discolored testing
Mixture with dye.
Soaking sample in
Blue: Brilliant Blue FCF
water: 200 ml.
Red: New Coccine
⇒ UV-VIS
(absorption of water)
(Tar dye)
Wave length [nm]
After 24 hours, the discoloring
of dye isn’t appeared.
≅ Corresponding time of
PEG washing in figure
2.
Similar
performance of the
hydrophobicity in rubbing test.
After placing samples in the water, a change with the
color ends within 4 minutes.
Figure S7. Colored highly hydrophobic coating and discoloration test by
washing the film.
80
80
80
80
4
5
6
7
10
100
90
110
120
140
12
13
14
15
16
100
100
9
11
80
100
8
In frame
（OMR-PIF）
24
80
1
1
1
1
1
1
1
1
24
24
24
24
24
24
80
2
24
On frame
3 （OMR-POF）
80
1
Sample Name
Heating
Temper Heating
ature Time [h]
oC
Tetrad C
Tetrad C
Tetrad C
Tetrad C
Tetrad C
Tetrad C
Tetrad C
Tetrad C
Tetrad C
Tetrad C
Tetrad C
Tetrad C
Tetrad C
Tetrad C
Tetrad C
Tetrad C
Resin
Amine
15.47 4,4'-Diaminodicyclohexylmethane
15.47 4,4'-Diaminodicyclohexylmethane
15.47 4,4'-Diaminodicyclohexylmethane
15.47 4,4'-Diaminodicyclohexylmethane
15.47 4,4'-Diaminodicyclohexylmethane
15.41 4,4'-Diaminodicyclohexylmethane
15.41 4,4'-Diaminodicyclohexylmethane
15.41 4,4'-Diaminodicyclohexylmethane
9.22 Tomaid 245-S
9.46 Tomaid 245-S
9.52 Tomaid 245-S
9.52 Tomaid 245-S
14.3 Tomaid 245-S
14.3 Tomaid 245-S
14.3 Tomaid 245-S
14.3 Tomaid 245-S
Mass %
PEG
7.63 MW 200
7.63 MW 200
7.63 MW 200
7.63 MW 201
7.63 MW 200
7.70 MW 200
7.70 MW 200
7.70 MW 200
9.22 MW 200
9.46 MW 200
9.52 MW 200
9.52 MW 200
14.3 MW 200
14.3 MW 200
14.3 MW 200
14.3 MW 200
Mass %
Materials for frame in Organic Monolithic Resin
48.96
48.96
48.96
48.96
48.96
48.97
48.97
48.97
46.08
47.30
47.59
47.62
71.4
71.4
71.4
71.4
Mass %
Concentration in Mixture
TiO2 Photocatalyst
-
-
-
-
25.5
25.5
25.5
25.5
25.5
25.3
25.3
25.3
32.3
33.1
33.3
33.3
-
-
-
-
49.9
49.9
49.9
49.9
49.9
49.7
49.7
49.7
59.8
62.8
63.6
63.6
-
-
-
-
2.5
2.5
2.5
2.5
2.5
2.6
2.6
2.6
3.2
0.7
0.1
0.0
-
-
-
-
4.83
4.83
4.83
4.83
4.83
5.03
5.03
5.03
5.98
1.26
0.13
0.00
0.61
0.61
0.001 31×10-5
-5
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
0.005 6.2×10
-
-
-
-
-
-
-
-
0.61
0.61
0.61
0.61
0.61
-
-
-
-
-
0.61 toluene
0.61 xylene
0.61 acetone
0.61
0.61
0.61
0.61
0.61
-5
0.0001 3.1×10
0.61
0.000
0.000
FP
TiO2 Photocatalyst
Organic
Concentratio
in Sol solusion
solvent
n
for spray
[Mass
%
in
Mass % in
Mass % in Solution Mass %
coating
Mass %
Mass %
frame.
frame.
Mass % on frame. Solution]
PTFE particles
Table S1. The prepared conditions of the highly hydrophobic monolithic resin.
Figure 9, 10
Figure 9, 10
Figure 9, 10
Figure 9, 10
Figure 10
Figure 7
Figure 7
Figure 7, 8
Figure 6
Figure 6
Figure 6
Figure 6
Figure 4
Figure 4
Figure 4, S1, S3
Figure S1, S3
Remark
6. Prepared conditions of the highly hydrophobic monolithic resin
Table S1 shows the prepared conditions of the highly hydrophobic monolithic resin. Then, the
important conditions in the present study are as follows.