Observation of Skin Changes by Atmospheric Plasma Jet Irradiation
Kazuo Shimizu1, Kentaro Hayashida2, Marius Blajan1
1Organization for Innovation and Social Collaboration, Shizuoka University
2Graduate School of Engineering, Shizuoka University

Johoku, Hamamatsu, 432-8561, Japan
E-mail：shimizu@cjr.shizuoka.ac.jp

Medical application using atmospheric plasma havebeen studied such as sterilization, blood coagulation
and a wide range of the other applications [1, 2].
Radicals, active species and so on which aregenerated by atmospheric plasma could be beneficial
for use in various medical application. However, thespecific mechanism of the biomedical effects are notclearly understood. In addition, a less invasive
treatment for human body is required in the medicalapplications.
Atmospheric plasma jet has been investigated as aplasma source for biomedical application recently [3].
Especially, atmospheric plasma jet using argon as aprocess gas was employed for blood coagulation andcauterizing tumors. If atmospheric plasma jet
irradiates living matter directly, it is concerned thatthe irradiation may have a bad influence on the livingmatter.
In this study, the changes by irradiating atmosphericplasma jet on a rat skin was investigated.

Table 1 Experimental condition
Power supply

ACApplied voltage [kV]
5.0 (zero- to-peak)Power supply frequency [kHz]16.1
Flow rate [L/min.]
5.0
Process gas
Argon
Exposure time [min.]3, 5

RESULTS AND DISCUSSIONS(1)Observation of the rat skin surface
The rat skin surface was observed by a digital
microscope after the atmospheric plasma jetirradiation. Figure 4 shows the image of the rat skinsurface before irradiation. Figure 4 (a) and (b) show
the image of the rat skin surface after irradiationfor 3 or 5 minutes, respectively. Red circle showsthe exposed area.

METHODS(1)Experimental setup
Figure 1 shows the experimental setup. An electrodefor generating atmospheric plasma jet consisted in a
glass tube, a tungsten wire and aluminum tape. The
tungsten wire was energized by a neon transformer
and the aluminum tape was grounded. The process gas
was fed from a gas cylinder to the electrode.
Figure 2 shows the discharge voltage and current
waveforms. Figure 3 shows the image of thedischarge. The atmospheric plasma jet irradiated thewister rat skin on a stage with a distance of 1 mm
between a tip of the electrode and the rat skinsurface.
Table 1 shows the experimental condition.

Fig. 4 Rat skin surface (a) before irradiation. (b) After
irradiation for 3 minutes.

(b)

4540353025201510
50306090120

Exposure time [sec.]

150180Fig. 6 Change of the maximum temperatureon the rat skin surface

An increase in the temperature was observed on
the rat skin surface after 180 seconds ofatmospheric plasma jet irradiation. This increase of
the temperature is considered by the heat whichcaused by the atmospheric plasma jet. A thermal
injury occurred when skin was exposed to 45 ℃
for one hour.
The factor which changes color on the rat skinsurface include the following reasons.
ⅰ) A burn injuryⅱ) An electrical damage
However, the temperature achieved after 180
seconds was below 45 ℃ in this study. Thus it isconsidered that the temperature increase was not
the reason for the change of color on the rat skinsurface [4].

Fig. 4 (c) Rat skin surface after irradiation for 5 minutes.

Fig. 1 An experimental setup for irradiating
the plasma jet to rat skin.

Figure 6 shows the change of the temperature on
the rat skin.

Skin temperature [°C]

INTRODUCTION

Comparing the post-irradiation rat skin surface
with pre-irradiation one, a slightly change in color
was confirmed. Though the rat skin was exposed tothe atmospheric plasma jet directly, a great change
did not occur. In addition, color change afterirradiation for 5 minutes was not so different fromthat of 3 minutes one.
The factors which contributed to these changes
could be the following: an electrical damage, athermal injury and a change of water amount on therat skin surface. To find out the main factor of thecolor change, the temperature on the rat skin wasobserved.
(2) Change of temperature on the rat skin surface
The temperature was observed by a thermal camera(TVS-200) when the rat skin was exposed to theatmospheric plasma jet. Measurement time of thetemperature was from 30 seconds to 180 seconds.
Measured temperature was maximum temperature on
the rat skin surface.
Figure 5 shows the experimental apparatus and its
thermal image.

Fig. 2 Discharge voltage and current waveforms.

CONCLUSIONS
Rat skin was exposed to atmospheric plasma jet toinvestigate the influence by atmospheric plasma jet
exposure to the skin sample. The following results
were obtained.
1. The change of color of the rat skin surface wasobserved after the atmospheric plasma jet wasirradiated for 3 or 5 minutes.
2. Color change on the rat skin surface after
irradiation for 5 minutes was not so different
from that carried out for 3 minutes.
3. The increase in the maximum temperature on therat skin surface was confirmed when theatmospheric plasma jet was irradiated from 30
seconds to 180 seconds.
4. The main factor of color change could beconsidered due to the electrical damage whichappeared after 180 seconds [5].

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Fig. 3 Image of the atmospheric plasma discharge
Fig. 5 An experimental apparatus and its thermal image