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

described in Figure 4.

Figure S1. Fluctuation of film thickness during outdoor testing.

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.

-1.0

-0.75

-0.5

-0.25

0.0

0.25

0.5

0.75

1.0

0 25 50 75 100 125 150

変化量

[m

]

経過時間 [d]

TiO2: 0 Mass%TiO2: 3.1× 10-5 Mass%

0

20

40

60

80

100

120

140

160

0 25 50 75 100 125 150経過時間 [d]

接触角

[ o]

150100500

[㎜]

TiO2: 0 Mass%TiO2: 3.1× 10-5 Mass%

膜厚変化 接触角変化

降水量の経日変化（横浜管区気象台）

Elapsed time [day]

Am

ount

of t

hick

ness

cha

nge

[m

]

Rainfall fluctuation (Yokohama District Meteorological Observatory)

■ TiO2: 0 Mass%◆ TiO2: 3.1 × 10-5 Mass%

a) b)

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.

Figure S3. Contact angles under ultraviolet exposure. The UV intensity was 2 mW/cm2.

0102030405060708090

100

300 400 500 600 700Wavelength [nm]

Ref

lect

ance

[%]

ST-01

0 200 400 600 800 1000 1200 1400 1600Irradiation time [h]

0

20

40

60

80

100

120

140

160

Without TiO2

TiO2 3.1×10-5 Mass% Black light

Sample

UV Intensity 2 mW/cm2

TiO2 31× 10-5 Mass%

Con

tact

ang

le [

o ]

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.

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].

Figure S4. Diffuse reflectance spectrum of UV/VIS in TiO2 photocatalyst (ST-01).

Air

Area of frame modified by fluorine polymer

Porosity of organic monolithic resin: 80 % ⇒ l = 0.8Maximum Mass % of TiO2 particles in organic monolithic resin: 5 % ⇒ m = 0.05

l 1- l

Area of baredTiO2 particles

1- m m

Frame

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.

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.

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.

Figure S6. Phase separation between the mixture and the solvent.

Figure S7. Colored highly hydrophobic coating and discoloration test by washing the film.

RedBlueWhite

Discolored testing

UV-VIS

After placing samples in the water, a change with the color ends within 4 minutes.

Mixture with dye.Discolored testing.

Red: New CoccineBlue: Brilliant Blue FCF

(Tar dye)

Soaking sample in water: 200 ml.⇒ UV-VIS

(absorption of water)

Wave length [nm]

Rat

e of

Abs

orpt

ion

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.

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.

180

24Te

trad C

14.3

Toma

id 24

5-S

14.3

MW 20

071

.4-

--

-0.0

000.0

000.6

1-

Figur

e S1,

S32

8024

Tetra

d C14

.3To

maid

245-

S14

.3MW

200

71.4

--

--

0.000

13.1

×10

-50.6

1-

Figur

e 4, S

1, S3

380

24Te

trad C

14.3

Toma

id 24

5-S

14.3

MW 20

071

.4-

--

-0.0

0131

×10

-50.6

1-

Figur

e 44

8024

Tetra

d C14

.3To

maid

245-

S14

.3MW

200

71.4

--

--

0.005

6.2×

10-5

0.61

-Fig

ure 4

580

24Te

trad C

9.52T

omaid

245-

S9.5

2MW

200

47.62

33.3

63.6

0.00.0

0-

-0.6

1Fig

ure 6

680

24Te

trad C

9.52T

omaid

245-

S9.5

2MW

200

47.59

33.3

63.6

0.10.1

3-

-0.6

1-

Figur

e 67

8024

Tetra

d C9.4

6Tom

aid 24

5-S

9.46M

W 20

047

.3033

.162

.80.7

1.26

--

0.61

-Fig

ure 6

880

24Te

trad C

9.22T

omaid

245-

S9.2

2MW

200

46.08

32.3

59.8

3.25.9

8-

-0.6

1-

Figur

e 69

100

1Te

trad C

15.41

4,4'-D

iamino

dicyc

lohex

ylmet

hane

7.70M

W 20

048

.9725

.349

.72.6

5.03

--

0.61a

ceto

neFig

ure 7

, 810

100

1Te

trad C

15.41

4,4'-D

iamino

dicyc

lohex

ylmet

hane

7.70M

W 20

048

.9725

.349

.72.6

5.03

--

0.61x

ylene

Figur

e 711

100

1Te

trad C

15.41

4,4'-D

iamino

dicyc

lohex

ylmet

hane

7.70M

W 20

048

.9725

.349

.72.6

5.03

--

0.61t

oluen

eFig

ure 7

1210

01

Tetra

d C15

.474,4

'-Diam

inodic

ycloh

exylm

etha

ne7.6

3MW

200

48.96

25.5

49.9

2.54.8

3-

-0.6

1-

Figur

e 10

1390

1Te

trad C

15.47

4,4'-D

iamino

dicyc

lohex

ylmet

hane

7.63M

W 20

148

.9625

.549

.92.5

4.83

--

0.61

-Fig

ure 9

, 10

1411

01

Tetra

d C15

.474,4

'-Diam

inodic

ycloh

exylm

etha

ne7.6

3MW

200

48.96

25.5

49.9

2.54.8

3-

-0.6

1-

Figur

e 9, 1

015

120

1Te

trad C

15.47

4,4'-D

iamino

dicyc

lohex

ylmet

hane

7.63M

W 20

048

.9625

.549

.92.5

4.83

--

0.61

-Fig

ure 9

, 10

1614

01

Tetra

d C15

.474,4

'-Diam

inodic

ycloh

exylm

etha

ne7.6

3MW

200

48.96

25.5

49.9

2.54.8

3-

-0.6

1-

Figur

e 9, 1

0

On fr

ame

OMR-

POF

（）

In fra

meOM

R-PI

F（

）

Samp

le Na

me

TiO2 P

hoto

cata

lyst

in So

l solu

sion

Mass

%on

fram

e.Ma

ss %

infra

me.

Mass

%Ma

ss %

PEG

Mass

%

Mat

erial

s for

fram

e in O

rganic

Mon

olith

ic Re

sinPT

FE pa

rticle

sTiO

2 Pho

toca

talys

t

Mass

%Ma

ss %

infra

me.

Solut

ionMa

ss %

Amine

Mass

%

Heat

ingTe

mper

atur

eoC

Heat

ingTim

e [h]

Conc

entra

tion i

n Mixt

ure

FPCo

ncen

tratio

n[M

ass %

inSo

lution

]

Orga

nicso

lvent

for sp

ray

coat

ingRe

mark

Resin

Tabl

e S1.

The

pre

pare

d co

nditi

ons o

f the

hig

hly

hydr

opho

bic

mon

olith

ic re

sin.