IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 37, NO. 1, JANUARY 2009
121
The Interaction of a Direct-Current Cold
Atmospheric-Pressure Air Plasma With Bacteria
Hongqing Feng, Peng Sun, Yufeng Chai, Guohua Tong, Jue Zhang, Weidong Zhu, and Jing Fang
Abstract—A direct-current cold atmospheric-pressure air
plasma microjet (PMJ) based on the microhollow cathode discharge design is used to inactivate six types of bacteria within a
small well-defined area on a large petri dish. We show that the
PMJ is very effective in inactivating bacteria in their vegetative
state as well as in the spore state within the area of plasma
exposure. We also observed that bacteria in their vegetative state
were inactivated efficiently outside the area of direct plasma exposure. Different bacteria responded differently to an increase
in the plasma exposure (dose). Lastly, we observed two types of
colony forming unit (CFU) distributions after plasma treatment;
one distribution is diffusionlike with a gradual increase of the
surviving CFU as one moves radially away from the area of direct
plasma exposure, and the other distribution shows an essentially
uniform reduction in surviving CFU across the entire petri dish.
Index Terms—Atmospheric pressure, colony forming units
(CFUs), direct current (dc), plasma jet.
I. I NTRODUCTION
N
ONTHERMAL (“cold”) plasmas are susceptible to instabilities when operated in air at atmospheric pressure.
Confining the plasmas to small dimensions (with at least one
dimension at or below 1 mm) has been shown to improve
the stability of atmospheric-pressure air plasmas, and several
such “microplasma” designs have been reported in the literature, e.g., the plasma needle [1], the atmospheric-pressure
plasma jet [2], various corona discharges [3], [4], the splitring resonator microplasma [5], and the microhollow cathode
discharge (MHCD) [6]. These microplasmas can be generated
by direct-current (dc), alternating-current (ac including RF and
microwave), or pulsed excitation. Stable atmospheric-pressure
air plasmas can also be generated using ac or pulsed power in
Manuscript received May 19, 2008; revised August 19, 2008, September 7,
2008 and October 21, 2008. Current version published January 8, 2009. This
work was supported in part by Bioelectrics Inc. (USA) and in part by the
National Basic Research Program of China 2007CB935602.
H. Feng and Y. Chai are with the Academy for Advanced Interdisciplinary
Studies, Peking University, Beijing 100871, China.
P. Sun and G. Tong are with the Department of Biomedical Engineering,
College of Engineering, Peking University, Beijing 100871, China.
J. Zhang is with the Laboratory of Biomedical Signal and Image Studies,
Department of Biomedical Engineering, College of Engineering, Peking University, Beijing 100871, China (e-mail: zhangjue@pku.edu.cn).
W. Zhu is with the Department of Applied Science and Technology,
Saint Peter’s College, Jersey City, NJ 07031 USA (e-mail: wzhu@spc.edu).
J. Fang is with the Academy for Advanced Interdisciplinary Studies
and the Department of Biomedical Engineering, Peking University, Beijing
100871, China.
Color versions of one or more of the figures in this paper are available online
at http://ieeexplore.ieee.org.
Digital Object Identifier 10.1109/TPS.2008.2008438
an arrangement where at least one electrode is covered with an
insulating (or highly resistive) material (dielectric barrier discharges (DBDs) [7], floating-electrode DBDs [8], and resistive
barrier discharges [9]). Applications of these plasmas span a
wide range from UV/VUV radiation sources [4], [10] or radiation detector [11] to microdischarge plasma reactors [12] to the
remediation of volatile organic compounds [13], [14]. The use
of atmospheric-pressure cold plasmas in biomedical application
has attracted considerable attention recently due to possible
applications in wound healing [8], [15], sterilization of heatsensitive reusable medical instruments [16], [17], or the surface modification of biocompatible materials [18], [19]. Both
atmospheric- and low-pressure plasmas have been used extensively in the inactivation of various microorganisms [20], [21].
In this paper, we report results of the interaction of a dc
atmospheric-pressure cold air plasma microjet (PMJ) based on
the MHCD concept with six types of bacteria. The samples after
preparation and characterization were placed in a large petri
dish. Only a well-defined small area were subjected to various
doses of plasma exposure. The number of colony forming units
(CFU count) before and after plasma treatment was examined
inside the area of direct plasma exposure as well as outside.
Both bacteria in their vegetative state and spores were subjected
to plasma inactivation.
II. E XPERIMENTAL D ETAILS
A. Generation of the Atmospheric-Pressure PMJ
The PMJ used in the present study is based on the MHCD
concept [22]. The MHCD structure comprises a cathode with
a microhollow structure and an anode (with a similar microhollow structure, which is aligned with that in the cathode)
separated by a dielectric layer of dimensions below 1 mm.
When the operating gas (here, air or nitrogen) is pushed through
the opening of this structure and dc power is applied, a spatially
well-defined atmospheric-pressure PMJ can be sustained in
ambient air [23]. The device used in this study was originally
developed at the Frank Reidy Research Center for Bioelectrics
at Old Dominion University by Schoenbach et al. [24] and was
slightly modified from its original design here.
A schematic diagram of the device is shown in Fig. 1(a). Two
metal electrodes are separated from each other by a dielectric
layer of ∼ 0.5-mm thickness. The openings in the two electrodes are ∼ 0.8 mm in diameter. The high-voltage electrode is
completely embedded in the device and powered by a dc power
supply (Matsusada AU5R120). The outer electrode is grounded
for safety considerations. Although both positive and negative
0093-3813/$25.00 © 2008 IEEE
Authorized licensed use limited to: Peking University. Downloaded on June 6, 2009 at 10:50 from IEEE Xplore. Restrictions apply.
122
IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 37, NO. 1, JANUARY 2009
Fig. 1. (a) Schematic diagram of the PMJ device. Space between the metal
electrodes is ∼ 0.5 mm, and the size of the openings in the metal electrodes is
∼ 0.8 mm. (b) Picture of the PMJ operating with compressed air as the feed gas
in ambient air.
high voltages are able to generate and sustain the PMJ, we
primarily used a negative high voltage in this paper. A ballast
resistor of 5 k followed by a current monitoring resistor of
100 is inserted between the powered electrode and dc power
supply. We used compressed air as the working gas at a gas
flow rate of approximately 2 slm. The discharge sustaining
voltage is in the range of 400–600 V with an operating current
in the 20–35-mA range. Under these operating conditions, a
PMJ of ∼1-cm visible length is generated [see Fig. 1(b)]. The
power efficiency of our device (defined as power deposited
into the discharge relative to the total power drawn from the
power supply) is approximately 80%. The temperature of the
grounded electrode reaches approximately 70 ◦ C at a current of
20 mA and a flow rate of 2 slm. The gas temperature 1 cm away
from the nozzle is around 38 ◦ C.
To identify the reactive species that are generated in the
discharge and, subsequently, expelled, emission spectra were
recorded in the range of 200–900 nm along the axial direction
of the PMJ with a 0.75-m spectrometer (Princeton Instrument/
Acton Spectra Pro 2750). The whole spectrum was dominated
by N2 lines due the excessive nitrogen in air. A near-infrared
section of the spectrum is shown in Fig. 2 where emissions from
reactive species such as NO (742.0 nm) and O (777.2 nm) are
clearly identifiable. Some emission from NO was also observed
in the ultraviolet region from 215 to 315 nm.
B. Bacteria Cultures
Six different types of bacteria were used in our experiment:
Escherichia coli (DH5α), Staphylococcus aureus (S. aureus),
and Micrococcus luteus (M. luteus), and the three sporeforming bacteria Bacillus natto (B. natto), Bacillus subtilis
(B. subtilis), and Bacillus megaterium (B. megaterium). The
bacteria were obtained from the China General Microbiological
Culture Collection Center (see also Table I).
The bacteria were placed in a Luria–Bertani liquid culture for 12–18 h until they reached the logarithmic growth
Fig. 2. Emission spectrum at near-infrared range for PMJ with ambient air as
working gas.
phase. The suspensions were then diluted to a concentration of
104 CFU/ml. On an LB agar culture medium in a large petri
dish (90 mm in diameter), 150 μ l suspensions were then spread
more or less uniformly for plasma treatment and analysis.
Plasma-induced inactivation of spores using our PMJ was
studied for B. subtilis. The suspension of bacteria in their
vegetative state was spread onto an agar dish, and grown in
a batch culture for seven to ten days until the transition to
spores exceeded 95%. The spores were then removed and rinsed
with sterile water. The spore suspension was then spread on an
LB agar culture medium for plasma treatment.
C. Plasma Treatment
The plasma treatment of the bacteria was carried out on a
laminar-flow clean bench to avoid contamination. A schematic
diagram of the treatment setup is shown in Fig. 3. The distance
between the exit nozzle and the agar plate was 1 cm, and the
end of the visible plasma jet did not touch the bacteria suspension in the petri dish. The plasma treatment was limited to a
2 × 2 cm square area in the center of the petri dish (referred to
as the “treated area”). For each bacteria sample, the petri dish
was moved under the spatially fixed plasma torch with a constant speed of 4 mm/s along the gridlines shown in Fig. 3. Each
travel from the top left corner to the bottom right corner of the
defined square area corresponds to a treatment time of 30 s. The
effect of the plasma exposure (plasma dose) was studied by reversing (repeating) the treatment path n times (n = 0, 1, 2 . . .)
while maintaining the same speed, resulting in total plasma
treatment times of 0.5, 1, and 1.5 min for bacteria in the
vegetative state and 1.5, 2.0, and 2.5 min in the case of spores.
We repeated each experiment at least three times to ensure
that the results were sufficiently repeatable and allow the determination of statistical error bars. We also analyzed two sets of
control samples, one set of samples that was subjected only to
air flow without the plasma being present and one set that was
exposed to neither the plasma nor the air flow.
Authorized licensed use limited to: Peking University. Downloaded on June 6, 2009 at 10:50 from IEEE Xplore. Restrictions apply.
FENG et al.: INTERACTION OF DIRECT-CURRENT COLD ATMOSPHERIC-PRESSURE AIR PLASMA WITH BACTERIA
123
TABLE I
LIST OF THE BACTERIA CULTURES
Fig. 3.
Schematic diagram of the plasma treatment setup.
D. Inactivation Analysis
We determined the inactivation efficacy of the PMJ by performing CFU counts before and after the plasma treatment.
The plasma-treated bacteria samples in the petri dishes were
sealed and incubated in a box held at a constant temperature of
either 30 ◦ C or 37 ◦ C for about 18–21 h. Subsequently, CFU
counts were obtained for the plasma-treated area as well as for
the entire petri dish. This allows us to obtain information on the
efficacy of the plasma treatment in the treated area as well as
the area that was not directly exposed to the plasma. We define
the efficacy of the plasma treatment in terms of a “survival rate,”
which is the ratio of surviving CFU after plasma treatment
relative to the initial CFU count. Survival rates were determined
separately for the treated and untreated areas (defined as the
total area of the petri dish minus the treated area).
III. R ESULTS AND D ISCUSSIONS
A. CFU Evaluation
In the first series of experiments, we studied the effect of the
air flow on the inactivation of the samples of each of the bacteria
in the absence of the plasma. Within experimental uncertainty,
we did not observe a statistically significant inactivation of the
bacteria by the air flow in the absence of the plasma for any of
the six types of bacteria studied here.
The inactivation efficacy of the PMJ is shown in the following figures. We evaluated the CFU count separately for the
2 × 2 cm treated area as well as for the untreated area of the
petri dish. The results (for a 1.5-min total plasma exposure) are
shown in Fig. 4 for all six bacteria in their vegetative estate.
Almost no residual CFU are observed in the treated area in
all situations. We note that, in four out of the six cases, a
significant inactivation efficacy of the PMJ is observed even
in the untreated area of the petri dish. The only exceptions
are S. aureus and E. coli, which show a strong resistance
outside of the treated area. We note in particular that all three
spore-forming bacteria show a significant inactivation—in their
vegetative state—outside of the treated area. In fact, a total
plasma exposure of only 0.5 min results in an essentially zero
CFU account for the entire petri dish. Further inactivation
studies with the PMJ further removed from the petri dish will
be carried out as well as experiments with even lower plasma
exposures.
Authorized licensed use limited to: Peking University. Downloaded on June 6, 2009 at 10:50 from IEEE Xplore. Restrictions apply.
124
IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 37, NO. 1, JANUARY 2009
Fig. 6. Distribution patterns of surviving CFUs on the petri dish after PMJ
treatment for 1.5 min: (a) S. aureus and (b) M. luteus (see text for details).
Fig. 4. Survival rate of bacteria after a 1.5-min PMJ exposure (the vertical
scale is extended to −5% for better visualization of the error bars).
one inactivation agent and their simultaneous (or sequential)
action on the different types of bacteria with apparently very
different efficacies. Further studies are needed to shed light on
the origin of the different distribution patterns.
C. Plasma Dose Effect
Fig. 5. Survival rate of B. subtilis spores within the treated and untreated
areas. Spores were reduced to 6.5% in the treated area and to 64% in the
untreated area.
Spores are more difficult to inactivate due to the multiple
coatings and layers surrounding the genetic core. To evaluate
the effect of the PMJ on spores, Bacillus subtilis spore suspensions were prepared as described in Section II and treated with
the PMJ for 1.5 min. The results are shown in Fig. 5. The first
observation is that the spores in the treated area were reduced
to 6.5% of the initial CFU count, which is a significantly
less efficient inactivation efficacy compared to the bacteria
in their vegetative state. The second observation is that the
PMJ is very ineffective in inactivating the spores outside of the
treated area.
B. CFU Distribution Patterns
During the CFU evaluation, we observed two different spatial
distributions of surviving CFU on the petri dish: 1) a diffusionlike pattern [Fig. 6(a), S. aureus, treated for 1.5 min] with
essentially no surviving CFU in the treated area and a gradually
increasing number of surviving CFU as one moves out radially
from the treated area and 2) a uniform distribution [Fig. 6(b),
M. leteus, treated for 1.5 min] with a low CFU count across the
entire petri dish and essentially no difference in the CFU count
between the treated and untreated areas. The first distribution
was also observed in treated E. coli samples. The two different
CFU distributions are indicative of the presence of more than
The effect of the plasma exposure (plasma dose) on the
plasma inactivation efficacy was studied by using three different
total plasma treatment times, namely, 0.5, 1.0, and 1.5 min for
the bacteria in their vegetative state and 1.5, 2.0, and 2.5 min
for B. subtilis spores.
As mentioned earlier, a 0.5-min plasma treatment inactivates
almost all bacteria in the petri dish for the three Bacillus bacteria in their vegetative state. Thus, no dose effect was recorded
in those three cases. The survival rate of B. subtilis spores for
different treatment times is shown in Fig. 7(a). The CFU count
of B. subtilis spores in the treated area was reduced to 3%
of the initial count during the first 1.5 min and subsequently
appears to remain at a steady state within the uncertainty of
the determination of the survival rate. As far as the untreated
area was concerned, we found no significant inactivation of
the spores even at an exposure time of 2.5 min, indicating
that the PMJ is not effective in inactivating spores outside of
the treated area. The number of CFU of M. luteus in both
the treated and untreated areas decreases rapidly to less than
10% of the initial count in the first 0.5 min and is followed
by a much slower decay with increasing dose [Fig. 7(b)]. It is
possible that, during the first 0.5 min, some excited and reactive
species from PMJ penetrate through the outer membrane of
M. luteus and react with the biomaterial inside. These species
have a long lifetime and can thus travel radially to the untreated
area, leading to the inactivation of M. luteus in and out of
the treated area. With plasma electrons of energy as high as
10 eV and air as the working gas, atomic and metastable
oxygen (O and O∗ ), superoxide (O2− ) and ozone (O3 ), which
have a strong germicidal effect, are expected to exist in the
afterglow. Hydroxyl radical (OH) and reactive nitrogen species
(e.g., NO and NOx ) may also contribute in the inactivation
process.
E. coli is the only gram-negative bacteria studied. The PMJ
has similar efficacy on E. coli in the treated area, reducing the
CFU counts to about 5% within the first 0.5 min [Fig. 7(c)].
A 0.5-min dose increase inactivated the E. coli in the treated
area completely. The CFU count in the untreated area seems
to remain high (∼60%) for a short exposure to the PMJ, but
decreases substantially to ∼20% when the treatment time is
Authorized licensed use limited to: Peking University. Downloaded on June 6, 2009 at 10:50 from IEEE Xplore. Restrictions apply.
FENG et al.: INTERACTION OF DIRECT-CURRENT COLD ATMOSPHERIC-PRESSURE AIR PLASMA WITH BACTERIA
125
It is interesting to note that bacteria with different CFU
distributions after plasma treatment respond differently to an
increase in the plasma dose. As shown in Fig. 8, E. coli
(or S. aureus) bacteria show an essentially zero CFU count in
the treated area after a 0.5-min plasma treatment, while the
untreated area shows some reduction in the CFU count. With
an increasing plasma dose, the area of essentially zero CFU
count spreads out radially. On the other hand, M. luteus was
inactivated more or less uniformly across the entire petri dish,
and the number of residual CFU declines as the treatment time
is increased.
D. Possible Inactivation Mechanisms
The exact inactivation mechanisms for the death of microorganisms and the role of various inactivation agents are
still under debate. Moisan et al. suggested a sequence of
UV-induced photodesorption followed by etching through reactive species adsorption [25] for low-pressure plasma inactivation of microorganisms. This, however, does not apply directly
to atmospheric-pressure cold plasmas, where germicidal UV
(200–290 nm) is not present with sufficient intensity to inactivate the cells, even at the longest treatment times used here.
Montie et al. suggested the alternation of membrane lipid due
to unsaturated fatty acid peroxidation, the alternation of protein
from the amino acids oxidation and the nucleic acids [26].
Among those, lipids are the easiest to be attacked by reactive
oxygen species (ROS) because of their location near the cell
surface. Gram-negative E. coli is particularly vulnerable to ROS
due to its unique outer membrane. Mendis et al. [27] suggested
that charge accumulation on the outer surface of the membrane
can lead to the rupture of gram-negative bacteria. Gram-positive
bacteria, on the other hand, may be inactivated through direct
reaction of reactive species with the biomaterial in the cells.
B. subtilis spores are inactivated rapidly within the treated area
as a result of the deep diffusion of reactive species into the
interior of the spores, which leads to oxidative lethal damage
[28]. Outside of the treated area, however, reactive species may
not have enough momentum to penetrate the rather thick shell
of the spores.
IV. C ONCLUSION
Fig. 7. Bacteria CFU survival rate at different treatment times: (a) B. subtilis
spores, (b) M. luteus, and (c) E. coli.
increased to 1.5 min. Although the electron density decreases
rapidly with distance due to recombination and attachment in
air, negative and positive ions can be found at larger distances
from the visible plasma. Charge building up on the cells, which
eventually can cause the rupture of the cell membrane, may be
the reason for the cell death outside of the treated area.
A dc atmospheric-pressure cold air PMJ is shown to be able
to effectively inactivate the non-spore-forming bacteria E. coli,
S. aureus, and M. luteus as well as the spore-forming bacteria
B. megaterium, B. subtilis, and B. natto in their vegetative
state. In all cases, efficient inactivation was observed inside the
treated area on the petri dish, which is directly exposed to the
plasma. With the exception of E. coli and S. aureus, efficient
inactivation also occurred outside of the directly treated area.
The inactivation of bacteria in the untreated area is attributed
to the lateral transport of long-lived inactivation agents. In the
case of B. subtilis spores, the CFU count was found to drop
to about 3% in the treated area after a 1.5-min exposure to the
PMJ and did not decrease significantly as the plasma dose was
increased up to a total treatment time of 2.5 min. The PMJ is
much less effective in inactivating spores outside the treated
area, where the CFU count was reduced to only about 60% of
Authorized licensed use limited to: Peking University. Downloaded on June 6, 2009 at 10:50 from IEEE Xplore. Restrictions apply.
126
IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 37, NO. 1, JANUARY 2009
Fig. 8. Pictures to illustrate the different dose effect on E. coli and M. luteus. (a)–(d) E. coli. (e)–(h) M. luteus [(a) and (e) control; (b)–(d) and (f)–(h) treated for
0.5, 1.0, and 1.5 min, respectively].
its initial value after a 1.5-min plasma treatment did not seem
to decrease further with increasing plasma dose. Two distinctly
different types of CFU distributions after plasma treatment are
observed.
ACKNOWLEDGMENT
The authors would like to thank X. Zhang and H. Chen
from the Laboratory of Biomedical Signal and Image Studies at
Peking University for their help in the development of the CFU
counting program, Prof. Y. Zhang from the Institute of Vascular
Medicine at the Number 3 Hospital of Peking University for
her support in bacteria culturing, and Dr. K. Schoenbach,
Dr. J. Kolb, and R. Price from Frank Reidy Research Center
for Bioelectrics at Old Dominion University for their help with
the device design.
R EFERENCES
[1] E. Stoffels, I. E. Kieft, and R. E. J. Sladek, “Superficial treatment of
mammalian cells using plasma needle,” J. Phys. D, Appl. Phys., vol. 36,
no. 23, pp. 2908–2914, Dec. 2003.
[2] A. Scutze, J. Y. Jeong, S. E. Babyan, J. Park, G. S. Selwyn, and
R. F. Hicks, “The atmospheric-pressure plasma jet: A review and
comparison to other plasma sources,” IEEE Trans. Plasma Sci., vol. 26,
no. 6, pp. 1685–1694, Dec. 1998.
[3] M. Rader, I. Alexeff, P. P. Tsai, and L. C. Wadsworth, “Electrostatic
charging apparatus and method,” U.S. Patent 5 592 357, Jan. 7, 1997.
[4] M. Salvermoser and D. E. Murnick, “Efficient, stable, corona discharge
172 nm xenon excimer light source,” J. Appl. Phys., vol. 36, no. 23,
pp. 2722–2731, Sep. 2003.
[5] F. Iza and J. Hopwood, “Split-ring resonator microplasma: Microwave
model, plasma impedance and power efficiency,” Plasma Sources Sci.
Technol., vol. 14, no. 2, pp. 397–406, May 2005.
[6] M. Moselhy, I. Petzenhauser, K. Frank, and K. H. Schoenbach, “Excimer
emission from microhollow cathode argon discharges,” J. Phys. D, Appl.
Phys., vol. 36, no. 23, pp. 2922–2928, Dec. 2003.
[7] U. Kogelschatz, “Silent discharges for the generation of ultraviolet and
vacuum ultraviolet excimer radiation,” Pure Appl. Chem., vol. 62, no. 9,
pp. 1667–1675, Dec. 1990.
[8] G. Fridman, M. Peddinghaus, M. Balasubramanian, H. Ayan, A. Fridman,
A. Gutsol, A. Brooks, and G. Friedman, “Blood coagulation and living
tissue sterilization by floating-electrode dielectric barrier discharge in air,”
Plasma Chem. Plasma Process., vol. 27, no. 1, pp. 113–114, Feb. 2007.
[9] M. Laroussi, I. Alexeff, J. P. Richardson, and F. F. Dyer, “The resistive
barrier discharge,” IEEE Trans. Plasma Sci., vol. 30, no. 1, pp. 158–159,
Feb. 2002.
[10] W. Zhu, N. Takano, K. H. Schoenbach, D. Guru, J. McLaren, J. Heberlein,
R. May, and J. R. Cooper, “Direct current planar excimer source,” J. Phys.
D, Appl. Phys., vol. 26, no. 6, pp. 3896–3907, Jul. 2007.
[11] S.-J. Park, J. G. Eden, and J. J. Ewing, “Photodetection in the visible,
ultraviolet, and near-infrared with silicon microdischarge devices,” Appl.
Phys. Lett., vol. 81, no. 24, pp. 4529–4531, Dec. 2002.
[12] D. D. Hsu and D. B. Graves, “Microhollow cathode discharge stability
with flow and reaction,” J. Phys. D, Appl. Phys., vol. 33, no. 1, pp. 2898–
2908, Dec. 2003.
[13] A. Koutsospyros, S.-Y. Yin, C. Christodoulatos, and K. Becker, “Plasmochemical degradation of volatile organic compounds (VOC) in a capillary discharge plasma reactor,” IEEE Trans. Plasma Sci., vol. 33, no. 1,
pp. 42–49, Feb. 2005.
[14] C. Jiang, A.-A. H. Mohamed, R. H. Stark, J. H. Yuan, and
K. H. Schoenbach, “Removal of volatile organic compounds in
atmospheric pressure air by means of direct current glow discharges,”
IEEE Trans. Plasma Sci., vol. 33, no. 4, pp. 1416–1425, Aug. 2005.
[15] E. Stoffels, “Biomedical applications of electric gas discharges,” High
Temp. Mater. Process., vol. 6, no. 2, pp. 191–202, 2002.
[16] M. Laroussi, “Nonthermal decontamination of biological media by
atmospheric-pressure plasmas: Review, analysis, and prospects,” IEEE
Trans. Plasma Sci., vol. 30, no. 4, pp. 1409–1415, Aug. 2002.
[17] M. Kong, “Hospital decontamination using low-temperature atmospheric
plasmas,” in Proc.1st Int. Conf. Plasma Med., Corpus Christi, TX, 2007.
[18] F. Mwale, H. T. Wang, V. Nelea, L. Luo, J. Antoniou, and
M. R. Wertheimer, “The effect of glow discharge plasma surface
modification of polymers on the osteogenic differentiation of committed
human mesenchymal stem cells,” Biomaterials, vol. 27, no. 10, pp. 2258–
2264, Apr. 2006.
[19] F. S. Sanchez-Estrada, H. Qiu, and R. B. Timmons, “Molecular tailoring
of surfaces via RF pulsed plasma polymerizations: Biochemical and other
applications,” in Proc. IEEE Int. Conf. Plasma Sci., Banff, AB, Canada,
2002, p. 254.
[20] M. Moisan, J. Barbeau, M.-C. Crevier, J. Pelletier, N. Philip, and
B. Saoudi, “Plasma sterilization. Methods and mechanisms,” Pure
Appl. Chem., vol. 74, no. 3, pp. 349–359, 2002.
[21] M. Laroussi, J. P. Richardson, and F. C. Dobbs, “Effects of nonequilibrium
atmospheric pressure plasmas on the heterotrophic pathways of bacteria
and on their cell morphology,” Appl. Phys. Lett., vol. 81, no. 4, pp. 772–
774, Jul. 2002.
[22] K. H. Schoenbach, R. Verhappen, T. Tessnow, F. E. Peterkin, and
W. W. Byszewski, “Microhollow cathode discharges,” Appl. Phys.
Lett., vol. 68, no. 1, pp. 13–15, Jul. 2002.
[23] J. F. Kolb, R. O. Price, A. H. Mohamed, and K. H. Schoenbach, “DC powered atmospheric pressure micro-plasmajet for biomedical applications,”
in Proc. IEEE Int. Conf. Plasma Sci., Traverse City, MI, 2006, p. 361.
[24] J. K. Kolb, A.-A. H. Mohamed, R. O. Price, R. J. Swanson, A. Bowman,
R. L. Chiavarini, M. Stacey, and K. H. Schoenbach, “Cold atmospheric
pressure air plasma jet for medical applications,” Appl. Phys. Lett., vol. 92,
no. 24, pp. 241 501–241 503, May 2008.
[25] M. Moisan, J. Barbeau, S. Moreau, J. Pelletier, M. Tabrizian, and
L’H. Yahia, “Low-temperature sterilization using gas plasmas: A review
Authorized licensed use limited to: Peking University. Downloaded on June 6, 2009 at 10:50 from IEEE Xplore. Restrictions apply.
FENG et al.: INTERACTION OF DIRECT-CURRENT COLD ATMOSPHERIC-PRESSURE AIR PLASMA WITH BACTERIA
of the experiments and an analysis of the inactivation mechanisms,” Int.
J. Pharm., vol. 226, no. 1/2, pp. 1–21, Sep. 2001.
[26] T. C. Montie, K. Kelly-Wintenberg, and J. R. Roth, “An overview
of research using the one atmosphere uniform glow discharge plasma
(OAUGDP) for sterilization of surfaces and materials,” IEEE Trans.
Plasma Sci., vol. 28, no. 1, pp. 41–50, Feb. 2000.
[27] D. A. Mendis, M. Rosenberg, and F. Azam, “A note on the possible
electrostatic disruption of bacteria,” IEEE Trans. Plasma Sci., vol. 28,
no. 4, pp. 1303–1304, Aug. 2000.
[28] M. K. Boudam, M. Moisan, B. Saoudi, C. Popovici, N. Gherardi, and
F. Massines, “Bacterial spore inactivation by atmospheric-pressure plasmas in the presence or absence of UV photons as obtained with the same
gas mixture,” J. Phys. D, Appl. Phys., vol. 39, no. 16, pp. 3494–3508,
Aug. 2006.
Hongqing Feng received the B.S. degree from
Peking University, Beijing, China, in 2005, where
she is currently working toward the Ph.D. degree in the Academy for Advanced Interdisciplinary
Studies.
Peng Sun received the B.S. degree in biotechnology
from Beijing Forestry University, Beijing, China,
in 2008.
He is currently with the Department of Biomedical
Engineering, College of Engineering, Peking University, Beijing.
Yufeng Chai received the B.S. degree in power
system and automation from China Agricultural University, Beijing, China, in 1994.
He is currently with the Academy for Advanced
Interdisciplinary Studies, Peking University, Beijing.
As an engineer, he focuses on biomedical signal
processing and medical device design.
127
Guohua Tong received the B.S. degree from Heibei
University, Heibei, China, in 2007.
She is currently with the Department of Biomedical Engineering, College of Engineering, Peking
University, Beijing, China.
Jue Zhang received the Ph.D. degree in engineering
mechanics from Peking University, Beijing, China,
in 2003.
Since then, he has been with the Department of
Biomedical Engineering, Peking University, where
in 2006, he became an Associate Professor to
lead the Laboratory of Biomedical Signal and Image Studies. His current research interests include
biomedical applications of nonthermal atmospheric
pressure plasma, computer-aided surgery, and MR
imaging.
Weidong Zhu received the Ph.D. degree in physics
and material science from Stevens Institute of Technology, Hoboken, NJ, in 2005.
He further pursued postdoctoral research with
Frank Reidy Research Center for Bioelectrics, Old
Dominion University, and with the Department of
Physics and Engineering Physics, Stevens Institute
of Technology in 2006 and 2007, respectively. He
has been with Saint Peter’s College, Jersey City, NJ,
as an Assistant Professor of Physics in the Department of Applied Science and Technology since 2007.
Jing Fang received the Ph.D. degree from Tsinghua
University, Beijing, China, in 1987.
Since 1989, he has been with Peking University,
Beijing, where he was an Associate and then Full
Professor and is currently the Chairman of the Department of Biomedical Engineering and the Executive Deputy Dean of the Academy for Advanced
Interdisciplinary Studies. He has published over a
hundred papers, and his current research interests
include biomedical signal and image processing, and
biomechanics of cells and molecules.
Authorized licensed use limited to: Peking University. Downloaded on June 6, 2009 at 10:50 from IEEE Xplore. Restrictions apply.