Theoretical and experimental study of the factors of sterilization of medical articles in low pressure glow discharge plasma
In the report the results of experimental and theoretical studies of the parameters of direct current glow discharge plasma are presented. The efficiencies of its main sterilizing factors (charged particles, electrically neutral chemically active particles and ultraviolet radiation of the plasma) ar...
Saved in:
| Published in: | Вопросы атомной науки и техники |
|---|---|
| Date: | 2000 |
| Main Authors: | , , , , , , |
| Format: | Article |
| Language: | English |
| Published: |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2000
|
| Subjects: | |
| Online Access: | https://nasplib.isofts.kiev.ua/handle/123456789/81605 |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| Journal Title: | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| Cite this: | Theoretical and experimental study of the factors of sterilization of medical articles in low pressure glow discharge plasma / I.A. Soloshenko, V.V. Tsiolko, V.A. Khomich, A.I. Schedrin, A.V. Ryabtsev, V.Yu. Bazhenov, I.L. Mikhno // Вопросы атомной науки и техники. — 2000. — № 1. — С. 38-42. — Бібліогр.: 7 назв. — рос. |
Institution
Digital Library of Periodicals of National Academy of Sciences of Ukraine| id |
nasplib_isofts_kiev_ua-123456789-81605 |
|---|---|
| record_format |
dspace |
| spelling |
Soloshenko, I.A. Tsiolko, V.V. Khomich, V.A. Schedrin, A.I. Ryabtsev, A.V. Bazhenov, V.Yu. Mikhno, I.L. 2015-05-18T12:36:59Z 2015-05-18T12:36:59Z 2000 Theoretical and experimental study of the factors of sterilization of medical articles in low pressure glow discharge plasma / I.A. Soloshenko, V.V. Tsiolko, V.A. Khomich, A.I. Schedrin, A.V. Ryabtsev, V.Yu. Bazhenov, I.L. Mikhno // Вопросы атомной науки и техники. — 2000. — № 1. — С. 38-42. — Бібліогр.: 7 назв. — рос. 1562-6016 https://nasplib.isofts.kiev.ua/handle/123456789/81605 533.9 In the report the results of experimental and theoretical studies of the parameters of direct current glow discharge plasma are presented. The efficiencies of its main sterilizing factors (charged particles, electrically neutral chemically active particles and ultraviolet radiation of the plasma) are also studied. The prospects of the use of such discharge for cold sterilization of medical instruments is estimated. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Газовый рaзряд, ППР и их применения Theoretical and experimental study of the factors of sterilization of medical articles in low pressure glow discharge plasma Article published earlier |
| institution |
Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| collection |
DSpace DC |
| title |
Theoretical and experimental study of the factors of sterilization of medical articles in low pressure glow discharge plasma |
| spellingShingle |
Theoretical and experimental study of the factors of sterilization of medical articles in low pressure glow discharge plasma Soloshenko, I.A. Tsiolko, V.V. Khomich, V.A. Schedrin, A.I. Ryabtsev, A.V. Bazhenov, V.Yu. Mikhno, I.L. Газовый рaзряд, ППР и их применения |
| title_short |
Theoretical and experimental study of the factors of sterilization of medical articles in low pressure glow discharge plasma |
| title_full |
Theoretical and experimental study of the factors of sterilization of medical articles in low pressure glow discharge plasma |
| title_fullStr |
Theoretical and experimental study of the factors of sterilization of medical articles in low pressure glow discharge plasma |
| title_full_unstemmed |
Theoretical and experimental study of the factors of sterilization of medical articles in low pressure glow discharge plasma |
| title_sort |
theoretical and experimental study of the factors of sterilization of medical articles in low pressure glow discharge plasma |
| author |
Soloshenko, I.A. Tsiolko, V.V. Khomich, V.A. Schedrin, A.I. Ryabtsev, A.V. Bazhenov, V.Yu. Mikhno, I.L. |
| author_facet |
Soloshenko, I.A. Tsiolko, V.V. Khomich, V.A. Schedrin, A.I. Ryabtsev, A.V. Bazhenov, V.Yu. Mikhno, I.L. |
| topic |
Газовый рaзряд, ППР и их применения |
| topic_facet |
Газовый рaзряд, ППР и их применения |
| publishDate |
2000 |
| language |
English |
| container_title |
Вопросы атомной науки и техники |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| format |
Article |
| description |
In the report the results of experimental and theoretical studies of the parameters of direct current glow discharge plasma are presented. The efficiencies of its main sterilizing factors (charged particles, electrically neutral chemically active particles and ultraviolet radiation of the plasma) are also studied. The prospects of the use of such discharge for cold sterilization of medical instruments is estimated.
|
| issn |
1562-6016 |
| url |
https://nasplib.isofts.kiev.ua/handle/123456789/81605 |
| citation_txt |
Theoretical and experimental study of the factors of sterilization of medical articles in low pressure glow discharge plasma / I.A. Soloshenko, V.V. Tsiolko, V.A. Khomich, A.I. Schedrin, A.V. Ryabtsev, V.Yu. Bazhenov, I.L. Mikhno // Вопросы атомной науки и техники. — 2000. — № 1. — С. 38-42. — Бібліогр.: 7 назв. — рос. |
| work_keys_str_mv |
AT soloshenkoia theoreticalandexperimentalstudyofthefactorsofsterilizationofmedicalarticlesinlowpressureglowdischargeplasma AT tsiolkovv theoreticalandexperimentalstudyofthefactorsofsterilizationofmedicalarticlesinlowpressureglowdischargeplasma AT khomichva theoreticalandexperimentalstudyofthefactorsofsterilizationofmedicalarticlesinlowpressureglowdischargeplasma AT schedrinai theoreticalandexperimentalstudyofthefactorsofsterilizationofmedicalarticlesinlowpressureglowdischargeplasma AT ryabtsevav theoreticalandexperimentalstudyofthefactorsofsterilizationofmedicalarticlesinlowpressureglowdischargeplasma AT bazhenovvyu theoreticalandexperimentalstudyofthefactorsofsterilizationofmedicalarticlesinlowpressureglowdischargeplasma AT mikhnoil theoreticalandexperimentalstudyofthefactorsofsterilizationofmedicalarticlesinlowpressureglowdischargeplasma |
| first_indexed |
2025-11-25T23:26:43Z |
| last_indexed |
2025-11-25T23:26:43Z |
| _version_ |
1850580561242882048 |
| fulltext |
ВОПРОСЫ АТОМНОЙ НАУКИ И ТЕХНИКИ. 2000. №1.
Серия: Плазменная электроника и новые методы ускорения (2), с. 38-42.
38
UDK 533.9
THEORETICAL AND EXPERIMENTAL STUDY OF THE FACTORS
OF STERILIZATION OF MEDICAL ARTICLES IN LOW PRESSURE
GLOW DISCHARGE PLASMA
I.A.Soloshenko1, V.V.Tsiolko1, V.A.Khomich1, A.I.Schedrin1, A.V.Ryabtsev1,
V.Yu.Bazhenov1, I.L.Mikhno2
1Institute of Physics of NAS Ukraine, Kiev, Ukraine
2Institute of Epidemiology and Infective Diseases of HM Ukraine, Kiev, Ukraine
In the report the results of experimental and theoretical studies of the parameters of direct current glow discharge
plasma are presented. The efficiencies of its main sterilizing factors (charged particles, electrically neutral chemically
active particles and ultraviolet radiation of the plasma) are also studied. The prospects of the use of such discharge for
cold sterilization of medical instruments is estimated.
Introduction
In modern medical practice wide variety of heat
sensitive instruments and materials is used which require
cold sterilization techniques. Up to now sterilization of
such articles was performed by means of toxic gases –
pure ethylene oxide or its mixture with
fluorochlorocarbons. This sterilization technique requires
long (up to 24 hours) aeration process for processed
articles and, the most essential, makes a serious danger
for both servicing personnel health and environment. For
these reasons the development of new cold sterilization
techniques is essentially urgent problem. At present time
one of the most serious alternatives for gas sterilization is
represented by the use of gas discharge plasma as
sterilizing agent. Main advantage of the plasma technique
consists in fact that the plasma as chemically active
medium is formed during the processes of excitation,
dissociation and ionization of any gas or vapor medium,
including non-toxic ones (even noble gases are suitable).
Besides, in this case active particles exist only during the
discharge glowing and disappear practically instantly
after its turning off. These two circumstances provide
complete solution of the problems of safety and ecology.
In spite of fact that the use of gas discharge plasma for
sterilization of medical articles was proposed yet in the
60-th years, up to now thorough investigations, which
would allow objective estimations of efficiency and
application range of this technique, were not
accomplished. Particular aspects of this complex task
were considered in [1-5]. In the present proceeding
experimental and theoretical studies of physical processes
in low pressure gas discharge plasma, which determine
the efficiencies of sterilizing factors of the plasma, are
performed. Respective medical-biological studies are
performed as well. Obtained results give the answer to the
question about the efficiency and application range of the
plasma technique for the cases of using the most
interesting (from viewpoint of the practice) gases: air,
oxygen, hydrogen, carbon dioxide gas, nitrogen, argon.
Description of experimental setup and techniques
of the measurements
Direct current glow discharge was used in the
experiments for generation of the plasma. The discharge
current was varied in range 0,05–0,7 A, the voltage – in
range 400–600 V. The volume of work chamber, which
served for placement of the articles to be sterilized, was
varied in range 20–40 l. Prior to its filling with working
gas (the gases mentioned above as well as their mixtures
were used) the chamber was evacuated by means of
forepump down to residual pressure of 3⋅10-3 Torr.
Pressure of working gases was varied in range 5⋅10-2 –
25⋅10-2 Torr. Measurements of plasma density and
electron energy distribution functions (EDF) were
performed by means of single and double Langmuire
probes. It has been found that for pressure range given
above the plasma density was practically independent on
pressure and was determined only by introduced power.
At variation of specific power Wd introduced into the
discharge in range 3⋅10-3–30⋅10-3 W/cm3 the plasma
density possessed practically linear growth from 7⋅108 up
to 6⋅109 см-3. At that the plasma inhomogeneity in main
part of chamber volume did not exceed 25–30%. EDF
measurements were accomplished for discharges on air,
oxygen, nitrogen. In oxygen and air the dependence of
EDF on energy possessed monotonous character. In
nitrogen for particular discharge regimes inverted region
on EDF in energy range ~ 2–4 eV was observed, which
was due to vibrational excitation of N2 molecules (curve 3
in Fig.1). It has been determined that for typical regimes
of the discharge glowing (P=10-1–2⋅10-2 Torr,
Wd = 3⋅10-3–10-3 Вт/см3) the electric field value in the
plasma varies in range ≈0,1–1,0 V/cm.
Regimes of the discharge glowing were chosen in
such way, that the temperature of sterilized test objects
should not exceed 60°C, since it is required by the
conditions of sterilization of articles made from heat
sensitive materials.
Metal and glass Petri dishes with internal square
surface of about 10 cm2 were used as test objects.
Medical-biological researches were performed with
microorganisms in vegetative, spore and virus forms,
however, the results presented below were obtained with
the use of spores Bac.subtilis and Bac.stearothermophilus,
which appeared to be the most resistant to the action of
sterilizing factors of the plasma. For contamination of the
test objects aqueous spores suspension was used, which
39
was homogeneously deposited onto internal surface of
Petri dishes. Initial amount of the spores on the test
objects was varied in range 105 – 108 (that is, average
surface density comprised 104 – 108 spores/cm2). After
incubation of the test objects processed in the plasma
(incubation duration 48-72 hours) their sterility check was
performed by means of immediate colony count
technique. After that the survival curves were built, that
is, the dependencies of the number of survived
microorganisms on the sterilization time.
0 2 4 6 8 10 12 14
10-7
10-6
10-5
10-4
10-3
10-2
10-1
100 f0(ε) (eV3/2)
1
2
3
ε (eV)
Fig.1. Typical shape of electron energy distribution
function: 1 – theoretical calculation for nitrogen;
2 – calculation for oxygen; 3 – experimental results for
nitrogen
0 5 10 15 20
10-1
100
101
102
103
104
105
106
107
3
2
1
N
um
be
r o
f s
ur
vi
vo
rs
Sterilization time, min
Fig.2. Survival curves for spores Bac.subtilis, obtained by
colony count technique at sterilization by integral action
of the plasma (● ) and just by UV radiation of the plasma
(■ ) for various working gases: 1 –oxygen; 2 –air;
3– nitrogen. Р=2⋅10-2 Torr, Wd = 3⋅10-3 W/cm3.
Initial microbial load – 107 spores
Experimental results
In earlier proceedings of the authors [3-5], devoted to
determining of main regularities of the sterilization by
low pressure glow discharge plasma, it has been
determined that:
1. Sterilization time for all used gases is practically
independent on the gas pressure in range of its variation
(8⋅10-2–25⋅10-2 Torr), however, it decreases with the
growth of specific power introduced into the discharge.
Thus, the sterilization efficiency for each kind of the gas
is determined by the plasma density.
2. The most efficient working medium is oxygen
subsequently followed by air, carbon dioxide gas,
hydrogen, argon, nitrogen.
3. Plasma sterilization efficiency decreases with the
growth of initial density of the spores on the test objects
from 104 to 107 spores/cm2. The reason for such effect is
due to diminishing of penetration of sterilizing agents of
the plasma to the spores due to their aggregation and
forming the bundles at the density of 107 spores/cm2. It is
obvious that such peculiarity is inherent to all kinds of the
plasma sterilizers.
4. Charged particles of the plasma do not play essential
role in plasma sterilization and thus the main sterilizing
factors are represented by UV radiation and electrically
neutral chemically active particles of the plasma.
Current proceeding is devoted to study of efficiency of
the sterilization by UV radiation and electrically neutral
chemically active particles of the plasma. For determining
of relative contribution of plasma ultraviolet radiation the
experiments have been performed, in which one group of
the test objects was opened during the sterilization,
whereas another one was placed under the filter made
from either lithium fluorine (LiF) or quartz glass of KU-1
type with 3 mm thickness. Thus, sterilization of the first
group of the test objects was performed by integral action
of the plasma (first of all, by UV radiation and action of
chemically active electrically neutral particles), and that
of the second group was provided by means of just UV
radiation with wavelength λ≥120 nm in case of filter
made from LiF and with wavelength λ≥160 nm in case of
quartz filter. In Fig.2 the survival curves are presented for
the sterilization by integral plasma action and that by
ultraviolet radiation of the plasma for the cases of oxygen,
air and nitrogen use. One can see from the figure that the
curves obtained with and without filter use are practically
identical for these gaseous media. Analogous results were
obtained in all working pressure ranges and specific
powers Wd for all used working media with the use of
both KU-1 filters and LiF ones. Thus, it is possible to
conclude that sterilization of opened surfaces is
determined mainly by ultraviolet radiation of the plasma.
Measurements have also shown that sterilization is mainly
performed by UV radiation generated in wavelength
region ≈ 160-220 nm. It should be noted that the
efficiency of sterilization by UV radiation of the plasma is
essentially higher than that by UV radiation of mercury
lamps commonly used in medical practice. Particularly,
time of sterilization by plasma radiation with
WS ≈ 100 µW/cm2 is approximately five times shorter
than that by UV radiation of lamp BUV-30 with
essentially higher intensity WS = 1500 µW/cm2 (see
Fig.3). It should be also noted that sterilization by UV
radiation of the plasma possesses one more important
advantage – here the effect of shadowing is significantly
absent, because radiating plasma wraps around sterilized
articles, like a liquid. Naturally, it is valid only for articles
which do not have the holes smaller than Debye radius of
the plasma electrons. Considering sterilization of articles
40
with complex shape, that is, those having slits and holes
smaller than Debye radius of the electrons, it will be
determined by less efficient factor – electrically neutral
chemically active particles of the plasma, rather than by
its UV radiation. For this reason it is very important to
separate the efficiency of sterilization by these particles.
For that we have developed the technique which enabled
separation of the action provided by electrically neutral
particles from more powerful background presented by
UV radiation of the plasma. The idea of the technique
consisted in the use of small size mesh grid (with mesh
size smaller than Debye radius of the electrons) for
reflection of charged plasma particles, and the shield
which is placed behind the grid for reflection and
absorption of UV radiation of the plasma. For comparison
of sterilization efficiencies by UV radiation of the plasma
and active electrically neutral particles of the plasma in
Fig.4 corresponding survival curves are presented for the
use of oxygen and air as working gases. One can see from
the figure that the sterilization time in oxygen due to
electrically neutral chemically active particles is just 2
times longer than that due to UV radiation of the plasma.
In case of air use these times differ more essentially – by
factor of 5-6.
Numerical simulation
As it follows from the experiments described above,
main sterilizing role in case of opened surfaces is
performed by UV radiation. Charged plasma components
do not participate in the sterilization (it will be shown
below that the plasma flow onto sterilized surface is
essentially less than flows of UV quanta and electrically
neutral chemically active particles).
In case when the cavities with complex shape are
present main sterilizing factor is represented by neutral
particles. In oxygen the following particles can be
basically considered as mentioned ones: atomic oxygen,
ozone, excited atoms and molecules; in nitrogen these
particles are its excited atoms and molecules.
0 5 10 15 20 25 30
10-1
100
101
102
103
104
105
106
107
2
1
N
um
be
r o
f s
ur
vi
vo
rs
Sterilization time, min
Fig.3. Survival curves for spores Bac. subtilis obtained
by colony count technique at sterilization by UV radiation
of air plasma, WS ≈ 100 µW/cm2, λ ≈ 160-220 nm
(curve 1) and UV radiation of lamp BUV-30,
WS = 1500 µW/cm2, λ ≈ 254 nm (curve 2)
0 1 2 3 4 5 6 7 8 9 10 11 12
10-1
100
101
102
103
104
105
106
107
2
1N
um
be
r o
f s
ur
vi
vo
rs
Sterilization time, min
Fig.4. Survival curves for spores Bac.subtilis, obtained by
colony count technique at sterilization of opened surfaces
by electrically neutral active particles of the plasma
(filled symbols) and UV radiation of the plasma (hollow
symbols) for the cases of use of various working gases:
1 – oxygen; 2 – air. Р = ⋅10-1 Torr, Wd = 3⋅10-3 W/cm3,
initial microbial load 107 spores
For determining quantitative and qualitative
composition of the plasma, first of all, chemically active
neutral components and radiation, numerical simulations
of glow discharge in nitrogen and oxygen were performed
for the conditions of plasma sterilizer operation.
In numerical simulation we followed from the system
of kinetic equations for neutral and charged components
of the mixture:
!++= ∑∑
≤ )(, jiji
jiij
i
ii
i NNkNk
dt
dN
Here the first term in right side describes the processes
linear on the concentrations of mixture components Ni,
the second term describes pair collisions, etc. Rate
constants kej for pair collisions with participation of
electrons were determined from Boltzman equation which
was solved together with the system of kinetic equations.
The equations were solved with the use of numerical
techniques which were used and approved earlier in [7]
with assumption of uniform distribution of concentrations
of all mixture components.
It was assumed that gas ionization in the sterilizer is
accomplished by the beam of fast electrons with
energy∼ 450 eV, since, as it was shown by the
measurements of potential in glow discharge, practically
whole applied voltage ∼ 450 V falls on the near-cathode
layer having thickness∼ 1 cm. Electric field in main
region of the discharge is close to uniform one and has a
value of ∼ 0,1 V/cm at pressure ∼ 0,1 Torr, which ensures
drift character of electrons escaping from the volume onto
the anode. Death of electrons due to electron
recombination is not determining factor in electrons
balance due to low concentration of the plasma. In
calculations of UV radiation only transitions from lower
excited state to vibrationally excited levels of ground state
were taken in consideration. In case of nitrogen those are
Laiman-Birdge-Golfild bands.
41
Results of numerical simulation and their
comparison with the experiment
In Fig.1. typical shapes of electron energy distribution
function (EDF) in nitrogen and oxygen (curves 1 and 2,
respectively) are presented. In case of nitrogen on the
EDF in 2–4 eV energy range inverted region ( 00 >
εd
df
)
is observed, which is due to vibrational excitation of N2
molecules. Presence of inverted region is confirmed by
experimental measurements (curve 3). In case of oxygen
the dependence of EDF on energy possesses monotonous
behavior, since the cross section value for vibrational
excitation of O2 molecules is essentially less than that of
N2, and also due to cutoff of EDF on electron excitation
О2(1∆g) with low threshold energy, which is also in
agreement with the experiment. It should be noted that
essential condition of the presence of inverted region on
EDF in nitrogen consists in requirement for electric field
in the discharge to be small, which is inherent for low
pressure (р ≤ 0,1 Torr) glow discharge. EDF in this
situation is analogous to the distribution of electrons in
disintegrating plasma in certain moment after turning off
electric field [6]. In Figs.5 and 6 the dependencies of
concentrations of main plasma and mixture components
on pressure for nitrogen and oxygen are presented. One
can see from Fig.5 that concentrations of the components
which are primary products of electron-molecular
reactions (concentrations of plasma, atomic nitrogen and
oxygen, excited molecules N2 and O2) are practically
independent on pressure. It is due to fact that at pressure
increase the cutoff of EDF tail is enhanced at energies of
dissociation, excitation and ionization. Rate constants kej
of dissociation, excitation and ionization decrease
inversely proportionally to gas concentration. Overall
rates of formation respective plasma and mixture
components, which are determined as
22 ,ONej Nk products,
remain at that practically constant.
It should be noted that concentrations of such
chemically active components, as atomic oxygen and
excited oxygen molecules О2(1∆g) reach big enough
values ~ 1012 cm-3. Significantly higher value of О2(1∆g)
concentration, as compared to that of N2
* (difference by
three orders of magnitude), is due to low excitation
energy (ε = 0,95 eV) for 1∆g level in oxygen.
Concentrations of secondary products of electron-
molecular reactions (Fig.6), including those of UV quanta
32
, ωω "" NN , are small (~ 103 cm-3). However, it should
be taken into account that sterilization is determined by
flows of respective biologically active components onto
substrate, penetrability and level of their action on the
spores, rather than the concentrations. Flow of UV quanta
cN ⋅
32 , ωω "" comprises 3⋅1013 cm-2s-1, which is more than
one order of magnitude higher than the plasma flow
(~ 1012 cm-2s-1) due to low rate of its ambipolar diffusion.
Calculated values of UV quanta flow and plasma
concentration are in good agreement with experimental
data. Flows of atomic oxygen and O2(1∆g), O2(b1Σg
+)
(~ 1015–1016 cm-2s-1) have the highest values among
neutral active particles due to high concentrations of
mentioned species. Considering ozone, as one can see
from Fig.6, its concentration (unlike concentrations of the
other active components) grows up with pressure
increase. Since the sterilization efficiency does not
depend on pressure, it can be undoubtedly stated that
ozone does not play essential role in the process of
sterilization of opened surfaces of the instruments. It is
most likely due to its low concentration (~ 107 cm-3) and,
respectively, to its low flow (~ 1011 cm-2s-1). It should be
noted that high sterilization efficiency of UV radiation is
most likely due to peculiarities of its interaction with the
spores.
0,05 0,10 0,15 0,20
0
1
2
3
4
5
6
7
8
C
on
ce
nt
ra
tio
ns
in
n
itr
og
en
, c
m
-3
Pressure, Torr
0
2
4
6
8
10
12
14
16
C
on
ce
nt
ra
tio
ns
in
o
xy
ge
n,
c
m
-3
Fig.5. Dependencies of concentrations of the plasma
components on pressure: dashed curves for nitrogen
(■ – ne×108; ● – 9102*
2
⋅×
N
N ; ▲ – 1210×NN );
solid curves for oxygen (■ – ne×108; ● – 1210×ON ;
▲ – 11
)( 101
2
×
∆gON ; ▼ – 10
)( 101
2
×+ΣgbON ;
◆ – 810*
2
×
O
N )
0,05 0,10 0,15 0,20
0
2
4
6
8
10
12
14
16
18
C
on
ce
nt
ra
tio
ns
in
n
itr
og
en
, c
m
-3
Pressure, Torr
0
2
4
6
8
10
12
14
C
on
ce
nt
ra
tio
ns
in
o
xy
ge
n,
c
m
-3
Fig.6. Dependencies of concentrations of the plasma
components on pressure: dashed curves for nitrogen
(■ – 410×+NN ; ● – 100* ×NN ; ▲ –
1ω"N ;
▼ – 310
2
×ω"N ); solid curves for oxygen
(■ – 610
3
×ON ; ● – 610×+ON ; ▲ – 610×−ON ;
▼ – 310
3
×ω"N )
42
Distribution of N2 and О2 molecules on vibrational
states is analogous to [8]. Here we do not concentrate
attention on vibrationally excited molecules N2(v) and
О2(v), since they have the same valence as N2 and О2 in
ground state. And the last do not provide sterilizing action
on studied biological objects at any concentration.
Densities of the components, which may provide
sterilizing action (UV quanta, O, О2(1∆g), O2(b1Σg
+)),
possess linear growth with increase of the discharge
current. It is in a good agreement with the measurements
of sterilization efficiency, which grows up with the
increase of discharge power (current). It should be noted
that dependence of the plasma concentration on the
discharge current agrees with experimentally measured
one.
In conclusion of the present section, on a basis of data
given above, we would note that in oxygen and air
atmospheres main particles, which determine the
sterilization efficiency, are atomic oxygen and excited
molecules О2(1∆g), O2(b1Σg
+). Concentrations of active
components in N2 are significantly less than that in O2,
which explains the reason for increase of sterilization
time in nitrogen, as compared to those in oxygen.
Brief conclusions
On the basis of accomplished studies it is possible to
conclude the following:
1. Main role in plasma sterilization of opened surfaces
is performed by UV radiation of the plasma in
wavelength range ≈ 160–220 nm.
2. Efficiency of sterilization by UV radiation of the
plasma is essentially higher than that in case of UV
radiation sources commonly used in medical
practice.
3. Sterilization of the instruments with complex shape
is mainly determined by the action of electrically
neutral chemically active plasma particles.
4. At the use of oxygen and air as working medium the
time of sterilization of opened surfaces by active
electrically neutral plasma particles is 2–6 times
longer than that in case of action of UV radiation.
5. In result of numerical simulations it is shown that in
oxygen plasma the highest concentrations, among all
active electrically neutral particles, are possessed by
oxygen atoms and oxygen molecules excited to
electron levels with energies 0,98 eV and 1,64 eV,
which determine the sterilization efficiency for the
instruments with complex shape.
6. Calculated values of the plasma concentration,
electron energy distribution function, density of UV
radiation flow, and also dependencies of plasma
sterilizing components on the discharge parameters
are in good agreement with experimental data.
References
1. Szu-Min Lin, D.Sc. Thesis, University of Texas at
Arlington (1986). Proceedings of the International Kilmer
Memorial Conference on the Sterilization of Medical
Products, Moscow, 1989, p.80-99.
2. V.A. Khomich, I.A. Soloshenko, V.V. Tsiolko et al //
Proceedings of the 12 International Conference on Gas
Discharges and their Applications. Greifswald, 1997, vol.2,
p.740-744.
3. V.A. Khomich, I.A. Soloshenko, V.V. Tsiolko et al //
Proceedings of the Congress on Plasma Sciences. Prague,
1998, p.2745-2748.
4. V.A. Khomich, I.A. Soloshenko, V.V. Tsiolko et al//
Proceedings of the 14th International Symposium on
Plasma Chemistry, Prague, August 2-6, v.V, p.2551-2556.
5. R. Hugon, G. Henrion and M. Fabry // Meas. Sci. Technol.
vol.7, (1996), p.553-559.
6. V.P. Goretsky, A.V. Ryabtsev, I.A. Soloshenko,
A.F.Tarasenko, A.I. Schedrin // Zh.tekh.fiz. 1993. vol.63,
p.46 (in Russian).
7. V. Guerra and J. Loureiro // J. Phys. D: Appl. Phys., vol.28,
(1995), p.1903-1918.
This proceeding is supported by grant # 57 of Science and
Technology Center in Ukraine.
Description of experimental setup and techniques of the measurements
Experimental results
Numerical simulation
Results of numerical simulation and their comparison with the experiment
Brief conclusions
References
|