Surface Treatment of Thin Polymer Sheet by Using Microplasma
H. Fukunaga, Y. Komuro, S. Tatematsu, M. Blajan, K. Shimizu
Innovation and Joint Research Center, Shizuoka University,Jyouhoku, Hamamatsu, 432-8561, Japan
E-mail：shimizu@cjr.shizuoka.ac.jp

INTRODUCTIONRESULTSThis study introduces the surface treatment ofpolymer sheet developed for medical use by using
microplasma. The thickness of the sheet is lessthan 100nm. The sheet is fabricated for themedical use, and the adhesive force is importantwhen is applied on wounds. Microplasma treatment
was used in order to improve the adhesive force
which is related to the hydrophilic property ofthe sheet.

(1)Electric Characteristics(4) Durability of Plasma EffectDischarge voltage

1 kV
10 μS

Discharge current

20 mA(1)Microplasma Electrodes

10 μS

Fig. 4 Discharge voltage and current discharge
waveform.
Spike currents generated due to the streamers
appeared at the slope of discharge voltage asshown in Fig. 4. Microplasma reactor cangenerate atmospheric plasma at about 1 kV,
since its discharge gap was narrow (about100µm).

(2) Emission Spectroscopy
OH radical peakN2 SPS peakFig. 8 Durability of plasma effect.
A polymer sheet, which was treated by Arplasma (applied voltage 880 V, treatment time30 s) was kept in both air and N2 atmospherebetween 0-7days. The contact angle did not
return to initial value even after 7 days (Fig. 8).
An increase of contact angle was observed forboth air. Contact angle remained at a lower
value for N2 than in the air.

(5) Surface Analysis by XPS

Fig. 1 Microplasma electrodes.

A pair of metal plates covered with dielectric
layer were used as a electrodes (Fig. 1).
A spacer with a hexagonal hole with 7mm side wasinserted between electrodes in order to increasea gas flow and to secure the desired gap length.

C-C
C-O C=O

C-H.

Fig. 2 The image of microplasma electrodes during
discharge at a discharge voltage of 1 kV.
.

Fig. 5 Emission spectroscopy（Process gas; 1%
N2 in Ar).
OH radical, peaks were observed. These active
species cut surface bonds and contributed tomake new surface bonds.

(3) Relation of Treatment Time and ContactAngle(2) Experimental Setup

Fig. 9 XPS spectra of the C1s component.
The C-C,C-H bond decreased and C-O, C=O
bonds decreased compared with untreatedpolymer films (Fig. 9). Microplasma treatment
cut C-C, C-H bonds and made C=O, C-O bonds.
The C-O, C=O bonds have the hydrophilic
property. The C-C, C-H bonds has hydrophobic
property.

Fig. 6 Treatment time versus contact angle.
Table 2 Applied voltage for surface treatment
Fig. 3 An experimental setup for surface
treatment of polymer sheet.
A neon transformer was used as an AC highvoltage power supply. Carrier gas was flowed into
the reactor in which were enclosed microplasma
electrodes. The radicals and ions generated bymicroplasma collided with the surface of polymer
film (Fig. 3).
Discharge voltage and discharge current weremeasured bya digital oscilloscope. Treatedpolymerfilm
surfacemodifications
wereestimated by using XPS and a contact angle meter.
Table 1 An experimental condition ofSurface treatment.
Gas flow late [L/min]
Process gas
Distance of between electrodes andpolymer sheet [mm]5Ar,N2,Air
1

Process gasArN2
Air

Applied voltage [kV]
0.9
1.3
1.4

Contact angle was reduced to 30° in 10
seconds using Ar as shown in Fig. 6. Air and N2
microplasma did not affected so much as using
Ar. These condition are shown in Table 2.

78.3°

45.6°

Fig. 10 O/C ratio of surface analysis by XPS.
Increase of C/O ratio corresponding contact
angle degreased was observed as shown in Fig.
10.

CONCLUSIONS
Microplasma treatment for polymer film wascarried out.

Fig. 7 Image of water droplet on the polymer film.
The water droplet on the surface of treatedpolymer film changed to a more elongated shapewithout plasma treatment as shown in Fig. 7.

1. The minimum contact angle was about 45°
with Ar plasma treatment.
2. A longer lasting effect of microplasma
treatment
was observed after keeping thetreated polymer in N2 than air.
3. Hydrophilicgroupincreased
andthehydrophobic group decreased after plasma
treatment.