Vol.2, No.9, 1044-1048 (2010) Natural Science
Copyright © 2010 SciRes. OPEN ACCESS
Smell reduction and disinfection of textile materials by
dielectric barrier discharges
Siegfried Müller1*, Rolf-Jürgen Zahn1, Torsten Koburger2, Klaus-Dieter Weltmann1
1Leibnitz-Institut für Plasmaforschung und Technologie e.V., Greifswald, Germany; *Corresponding Author: muellers@inp-greifswald.de
2Hygiene Nord GmbH, Greifswald, Germany
Received 10 May 2010; revised 18 June 2010; accepted 25 June 2010.
In this paper we present investigations of textile
cleaning of cotton fabrics with respect to both,
the smell reduction and the disinfection of tex-
tile materials. Normal pressure plasma sources
on the base of dielectric barrier discharge (DBD)
were used for the purification and disinfection of
textiles. For gaseous odour components which
stick to clothing the results have shown that
one can reach an uncritical odour threshold. In
the case of disinfection a significant reduction
of microorganism population in some of the
samples could be noted. In particular a high
reactivity is reached, while in parallel with a ra-
diation by ultraviolet light ozone is activated.
Keywords: Dielectric Barrier Discharge; Odour
Reduction; Ozone Activation; Disinfection and
Sterilization; Pollution Control
The purification and disinfection of textiles is linked
with the use of water and diverse cleaning agents. This
causes a considerable consumption of our water resources
and leads to water charges. Water is becoming an increa-
singly scarce resource so that there is an urgent need to
reduce the amount of water and energy used for washing
In this contribution we present investigations of textile
cleaning and of disinfection by using plasma on the base
of DBD. DBDs are widely used as a non-thermal plasma
(NTP) technique in many plasma technological applica-
tions. Examples for NTP applications are air-pollution
control systems, soot decomposition, destruction of mi-
croorganisms, and water treatment [1-5]. Fur-ther, a lot
of other plasma processing applications like surface
cleaning, modification and functionalization are under
investigation [6].
In NTP’s temperature differs substantially between the
electrons and other particles (ions, atoms, molecules).
The electric energy is supplied only to charged particles,
mainly electrons (T 10.000 K), whereas the neutral gas
molecules remain almost cold (nearly room temperature).
In this case an NTP also refers to as non-equilibrium
plasma or cold plasma.
A strong electric field causes an ionization of the work-
ing gas and the formation of radicals and ions. These are
highly reactive species, and they are the basis for various
plasma chemical reactions.
Besides the above applications it was demonstrated
that one can eliminate or reduce odours from waste air in
the process of fabricating French frees by special DBD-
configurations [7]. The experiments showed a correla-
tion of odour strength with odourous compounds such as
volatile organic substances (VOCs). The VOCs were
identified mainly as aldehydes by using thermal desorp-
tion GC/MS. This was one background for the question
of textile cleaning concerning odour control like in the
case of airborne waste.
On the other hand microbial contaminations become
important in a lot of fields related to textile cleaning. As
it is known sterilization can be achieved by chemical
and/or physical treatment, such as heat, chemical solu-
tions, gases and radiation. But these methods have nu-
merous detrimental effects on the environment and sub-
strates. In the last few decades, medicine and food in-
dustries have conducted research to adopt new steriliza-
tion methods.
The sterilization with NTP arose as one of the suc-
cessful solutions destroying microorganisms. Steriliza-
tion agents of plasma are radiation and particles (elec-
trons, ions, radicals) [8-16].
Today, NTP can be generated in wide range of pres-
sures and with various means, such as the use of micro-
wave, RF, pulsed, ac and dc power sources. Several de-
vice geometries and electrode configurations have been
used. Among these, the DBD, the resistive barrier dis-
charge and the atmospheric pressure plasma jet have been
S. Müller et al. / Natural Science 2 (2010) 1044-1048
Copyright © 2010 SciRes. OPEN ACCESS
especially researched in the past few years [12].
The use of special plasma methods in the textile in-
dustry is also well-known. The spectra of applications of
plasma technologies ranges from the functionalization of
fibre surfaces to the production of special layers. Surface
properties like wettability, refractability, colourability
and printability or surface hardness can be influenced
without changing the bulk qualities of the substrate
The purpose of this investigation was to test the
cleaning of cotton fabrics with respect to the smell re-
duction and the disinfection using different DBD plasma
2.1. Discharge Configurations
In the process, textiles were exposed to the plasma in
different devices and by special methods. For the ex-
periments we used different plasma reactor constructions
on the basis of DBD configurations, partly described in
[7,19]. In principle a DBD consists of two electrodes
with at least one insulating layer (dielectric barrier) in
between. The DBD can be operated in a wide pressure
range (mbar-range up to atmospheric pressure range);
the electrode distance is in the range of tenth of mm up
to some mm. Generally the DBE can be sustained with
sine wave or square wave voltages in the frequency
range of some Hz up to some 100 kHz.
Three basic DBD configurations have been used. One
configuration consists of a flat arranged metallic bottom
electrode, a dielectric on the top of the bottom electrode,
a discharge gap and a second electrode. The dielectric
barrier is formed by a composite material of mica with a
thickness of 1 mm. In case of odour treatment the size of
the top electrode equals the dimension of textile patches
(120 mm × 75 mm). In the experiments square wave
voltages with positive or negative polarity have been
Besides the conventional configuration a stacked
DBD system was used. The special features of this reac-
tor configuration are structured electrodes arranged in a
compact pattern; the structured electrodes alternate with
dielectric flat disks. An exploded view of such a stack
configuration is given in [7]. In addition, spacers are
mounted between the mesh electrodes and the dielectrics.
The structured electrode consists of woven wires of
stainless steel with a wire thickness of 0.5 mm and a
mesh size of 0.8 mm. The dielectric barrier is formed
again by a composite material of mica. The stack is
sealed on two opposite sides and enables the processing
gas to flow through the configuration. The complete sys-
tem is mounted in a casing. The stack planes of wire mesh
are put alternately on high voltage potential or ground
potential alternately. At the reactor outlet a pipe was
mounted which serves as flow path and treatment space.
Additionally, in some experiments, a low-pressure mer-
cury lamp containing a quartz window was used. The
lamp was positioned at a side wall opening of the pipe
and radiates a part of the treatment space.
The third configuration contains a surface discharge
DBD (SD-DBD) with structured electrodes mounted at
the top of a casing. In the considered assembly a woven
wire electrode is positioned on top of a dielectric flat
disk while the second one is on its reverse side. The
types of wire electrodes and dielectric barriers are the
same as in case of stacked DBD.
Furthermore we constructed a setup where an extrac-
tion electrode in front of the SD-DBD was mounted.
This way an ion extraction from the discharge region can
be performed. The extraction electrode serves also as
holder for the textiles. The SD-DBD was sustained by
square wave or sine wave pulse voltages. The plasma is
ignited at the side wall in a small part of the reactor, and
the textiles are not in touch with the plasma part. Posi-
tive or negative ions are extracted from the discharge
side by the given potential difference and penetrate the
The electrical parameters of all three discharge con-
figurations were determined by a digital oscilloscope in
the usual way.
For the comparison of the microbiological activity we
used finally a commercial air purifier which is based on
a corona discharge configuration. In the product specifi-
cation more than 106 negative ions/cm3 were advertised.
2.2. Odour and Microbiological Procedures
For odour control the cotton fabric was situated within
time duration of 12 hours in the exhaust pipe of a cooker
hood from a food restaurant. For the different experi-
ments we prepared patches of 120 mm × 75 mm. In our
experiments the olfactometry was used for the smell
analysis. In order to realize this, the different patches
were put in bags of inert material with a volume of
approx. 8 litres. For the determination of the basic level
at smells, further samples of the untreated and unloaded
air were taken from the surroundings.
The microbiological tests were carried out using Es-
cherichia coli K12 (NCTC 10538) obtained from the
German Collection of Microorganisms and Cell Cultures
(DSMZ) as lyophilized cultures. The test organisms
were grown and cultivated in accordance with the DIN
EN 12353 “Chemical disinfectants and antiseptics—
Preservation of test organisms used for the determination
of bactericidal and fungicidal activity”. Small pieces (30
S. Müller et al. / Natural Science 2 (2010) 1044-1048
Copyright © 2010 SciRes. OPEN ACCESS
mm × 30 mm) of cotton cloth (DIN 53919) were used as
reference fabric and germ carriers. They were prepared
by rinsing them in distilled water, followed by steam
sterilization. After that the small pieces of cotton cloth
were contaminated by submerging them in a suspension
of E. coli. After a drying time of 3 h, they were either
stored away aseptically or exposed to the plasma in the
reactor right away. After the exposure, the number of
surviving bacteria was individually determined for each
germ carrier by vigorously vortexing it in test tubes con-
taining 5 ml nutrient broth (TSB) and glass beads and
transferring defined amounts and dilutions of the result-
ing solution, as well as the germ carrier, to agar plates
(TSA). After an incubation time of 48 h at 36 bacterial
colonies were counted, the number of surviving bacteria
was calculated and compared to that obtained from
non-plasma treated germ carriers.
For the removing of smells from textiles three discharge
configurations as described above were used. With dif-
ferent installations the impact of different effects was
evaluated. Figure 1 shows the comparison of these ver-
sions after the plasma treatment with air as carrier gas.
The results show a clear degradation of odour strength
by plasma application. Compared to the untreated sam-
ple this upshot occurred in all three constellations. By
using plasma methods reactions by long living species
like ozone are predominantly pronounced.
In the case of ion extraction method the textiles are
exposed for 1 hour to the ions coming from the plasma
electrode in a distance of 20 cm. The discharge was sus-
tained by negative pulse voltages with amplitudes of 7.5
kV and frequencies of 5 kHz. In this case the reduction
of odour strength in addition is based on the effect of
negative ions.
With the direct treatment of the patches in the discharge
Figure 1. Odour strength after different plasma treatment pro-
gap similar results could be reached under comparable
discharge conditions (treatment time of 6 minutes).
In case of stacked-SD-DBD the textile material is ar-
ranged on the exhaust-side of the reactor. Reactions by
ozone which is streaming out of the reactor become es-
pecially dominant.
As another procedure in the microbial analysis an ac-
tivation of oxygen was tested. Figure 2 shows the ex-
perimental set up. Ozone generated in the discharge was
exposed to UV radiation emitted by a Hg-low pressure
discharge lamp.
In Figure 3 this procedure schematically is demon-
strated. In the experiments we applied an interference
filter on demand to filter out the 254 nm resonance line.
The short wavelength resonance line (185 nm) leads
to the formation of ozone by cracking oxygen molecules,
but the line at 254 nm decomposes the ozone whereas
highly reactive oxygen radicals (activated oxygen) are
Figure 4 shows the effect of radiation of ozone at 254
nm. In this experiment ozone was generated with a
commercial ozonizer and the concentration has been
measured, using UV absorption spectroscopy. The ex-
periments took place in a box with a total volume of 100
As clearly recognizable, a quick decrease of the ozone
concentration occurs by switching on the UV radiation
(254 nm line) because of the following decomposition of
the ozone. After switching off the lamp a higher ozone
Figure 2. Experimental set up for treatment of textiles by SD-
DBD and UV-radiation.
Figure 3. Scheme of the ozone activation by UV radiation.
S. Müller et al. / Natural Science 2 (2010) 1044-1048
Copyright © 2010 SciRes. OPEN ACCESS
level is building up again.
The Figures 5 to 7 present the results of the microbial
tests. We carried out different test series with the devices
and methods described above to proof the possible ap-
plication of plasma procedures for the disinfection of
Figure 4. The influence of UV radiation on the ozone concen-
Figure 5. Results of the treatment in the discharge gap of a
Figure 6. Influence of discharge and ultraviolet radiation.
Figure 7. Comparison between ion extraction method and
commercial air purifier.
Figure 5 shows results of the treatment in the dis-
charge gap of a DBD with different frequencies, positive
and negative pulse voltages of 7.5 kV and a treatment
time of 30 minutes.
With the treatment in the discharge gap and a fre-
quency of 50 Hz about two-log reductions in number of
germs is observed. The best results are obtained by using
higher frequencies with more than six-log reductions in
the number of germs.
Figure 6 shows results when ultraviolet radiation
comes into operation. In this case an experimental ar-
rangement has been used such as in Figure 2.
The application of ultraviolet radiation (254 nm) al-
ready causes a reduction of about approx. 3 log 10 steps.
When we add additional a DBD a reduction over more
than 5 log steps emerges.
Figure 7 shows the effect of the ion extraction method
and a commercial air purifier. A commercial air purifier
causes a reduction of the germs of about approx. 70%.
The according results with the ion extraction methode
were performed with different pulse voltages. In the case
of negative pulses 91% and in the case of positive pulse
voltages 98% of germes were reduced.
dc, and rms do not have to be defined. Do not use ab-
breviations in the title or heads unless they are unavoid-
Atmospheric pressure plasmas possess the ability to re-
duce smell effectively. In addition a significant reduction
of microorganism population in some of the samples
could be achieved.
In case of odours it was already shown for the proc-
essing gas air loaded with aldehydes or butanone that an
oxidation or a decomposition of hydrocarbon com-
pounds may occur [7]. Here these reactions can be also
assumed as cleaning mechanisms.
S. Müller et al. / Natural Science 2 (2010) 1044-1048
Copyright © 2010 SciRes. OPEN ACCESS
The sterilization of the textile samples served notice-
able results in particular for the procedures with direct
plasma contact as well as in case of the oxygen excita-
tion by UV-light. In case of the oxygen excitation we can
assume reactions between excited atomic oxygen and
germ cell walls.
By direct exposure of germs with plasma a complex
and complicated impact of several effects occurs like
radiation and reactions of different radicals with the
germs. A charge accumulation and rupture of the outer
membrane of bacterial cells is also conceivable.
The attempts with the treatment by ions, with com-
mercial ionizer as well as with the introduced ion extrac-
tion procedure, show a noticeable effect. This indicates
possible ion molecule reactions.
The presented investigations are a first step. For ex-
amination of different disinfection mechanisms further
systematic investigations are necessary. In particular the
time dependence of the mechanisms is an important
The relatively simple designs of proposed DBD con-
figurations and methods give them the potential to re-
place conventional cleaning methods in described appli-
cation fields. It could help to save water consumption
and to develop a cleaning procedure of textiles without
the use of detergents.
The authors are grateful to Kirsten Anklam, Diana Neudeck, Tila
Krüger and Norman Mleczko for their technical support.
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