Effects of Environmental Humidity and Temperature on Sterilization Efficiency of Dielectric Barrier Discharge Plasmas in Atmospheric Pressure Air

Kikuchi, Yusuke; Miyamae, Masanori; Nagata, Masayoshi; Fukumoto, N.

doi:10.1143/jjap.50.01ah03

Cited by 12 publications

(6 citation statements)

References 20 publications

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“…These observations were similar to those reported by Zhao et al 17 and Yang et al 24 who observed marked erosions of Geobacillus stearothermophilus , Streptococcus mutans , and Lactobacillus acidophilus after low-temperature sterilization under surface-wave-excited O 2 plasma treatment. Kikuchi et al 19 also found that B. atrophaeus spores were deformed (SEM images) by DBD plasma treatment. In addition, the observation of severe damage of cell morphology in this study was also similar to that of Hong et al 18 , who demonstrated that E. coli was obviously destroyed after treatment with an atmospheric-plasma mixture created by the ionization of helium, as shown by transmission electron microscopy scanning.…”

Section: Discussionmentioning

confidence: 97%

“…Hong et al 18 used an atmospheric-plasma mixture created by the ionization of helium and oxygen to observe the inactivation of E. coli and Bacillus subtilis , and confirmed that oxygen radicals generated by radiofrequency plasma were effective for impairing bacterial cells and endospores. Kikuchi et al 19 studied the inactivation of Bacillus atrophaeus spores by DBD plasma in atmospheric humid air. The results revealed that the bacteria inactivation was completed within 15 minutes at a relative humidity of 90% and a temperature of 30°C, indicating that the sterilization rate depended not only on the relative humidity but also on the temperature, which affects the generation of reactive species such as hydroxyl radicals.…”

Section: Discussionmentioning

confidence: 99%

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Oral bacterial inactivation using a novel low-temperature atmospheric-pressure plasma device

Chang

Chen

2016

Journal of Dental Sciences

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Background/purpose Atmospheric-pressure plasma is a new technology for biomedical applications. Utilization of an ionized gas (plasma) to achieve disinfection is an alternative sterilization technique that has become popular recently due to its safety, cost effectiveness, and superior performance to traditional methods. The purpose of this study was to evaluate the germicidal effectiveness of a low-temperature atmospheric-pressure plasma device by treating Enterococcus faecalis for different durations. Materials and methods A novel low-temperature atmospheric-pressure plasma device was developed for this study. A suspension of E. faecalis (BCRC 10789) was standardized to 10 7 colony-forming units (CFUs)/mL, as confirmed by an optical spectrophotometer. E. faecalis was first transferred and spread on 70 sterile cover glasses measuring 18 mm 2 . Each batch of 10 specimens was exposed to the low-temperature plasma device and treated for 1 minute, 2 minutes, 3 minutes, 5 minutes, 10 minutes, and 15 minutes; the specimen treated for 0 minute served as the control. The cover glasses containing plasma-treated bacteria were then immersed into 10 mL deionized distilled water and vibrated with an ultrasonic device to detach the residual fluid. Bacterial colonies were finally inoculated into Luria–Bertani agar plates and cultured at 37°C for 24 hours. The numbers of bacterial colonies were counted to evaluate the germicidal efficacy of the plasma device, and the results were expressed as CFUs. Meanwhile, field emission scanning electron microscopy was performed to observe the cell morphology of E. faecalis prior to and after plasma treatment. Results Quantitative analysis of sterilization revealed a reduction in the number of bacterial colonies with time duration. When specimens were treated for 10 minutes, colonies of E. faecalis decreased from 10 5 CFUs to 10 2 CFUs. The sterilization D -value (90% cell reduction) of experiments was 2 minutes. Conclusion The novel low-temperature atmospheric-pressure device was capable of achieving effective sterilization of E. faecalis within a 2-minute interval. Further studies are needed to validate complete inactivation, refine the laboratory-made low-temperature plasma device, and develop a new plasma-jet device, which will be superior to traditional sterilization methods and can be used in root canal environment. This novel sterilization method can also be used as a clinical reference tool.

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Section: Discussionmentioning

confidence: 97%

Section: Discussionmentioning

confidence: 99%

Oral bacterial inactivation using a novel low-temperature atmospheric-pressure plasma device

Chang

Chen

2016

Journal of Dental Sciences

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“…On the other hand, higher RH levels above typical ambient values can be used to optimize the specific process under investigation: benzene decomposition is observed to reach an optimum in terms of efficiency for RH = 60% [11], the sterilization time of Bacillus atrophaeus spore is decreased to 15 min for RH = 90% instead of 60 min for RH = 60%-90% [12], the concentration of OH radicals is increased proportionally to RH for values higher than 35% [13], the remediation of naphthalene reaches an optimum for RH = 40%-60% [14], and 3 min exposure to air DBD plasma with 40%-90% RH leads to more than 2.3 times faster growth of Raphanus sativus L. [15] and a 56% increase in total seed weight of Arabidopsis thaliana [16]. Stable, humidity-proof SDBDs are therefore crucial for applications such as sterilization of microorganisms (bacteria, viruses and spores), treatment of plants, seeds [17], food, and PAW production, generally implying high humidity environments, which have great potential for industrial development.…”

Section: Introductionmentioning

confidence: 99%

Surface DBD degradation in humid air, and a hybrid surface-volume DBD for robust plasma operation at high humidity

Avino

Howling

Allmen

et al. 2023

J. Phys. D: Appl. Phys.

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Surface dielectric barrier discharge (SDBD) performance deteriorates in humid air, with permanent and/or reversible degradation of its components. Plasma operation in a humid environment is unavoidable when humid air or water-containing materials are treated. Experimental and numerical results indicate that an electrically conductive thin ﬁlm of water is responsible for ohmic dissipation and inhibited plasma ignition at high relative humidity. An alternative hybrid surface-volume DBD design provides more stable and uniform plasma operation in high-humidity atmospheres.

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“…In this way, non equilibrium low temperature plasma with high energy density can be produced at atmospheric pressure [1,2]. Thus, DBD has been widely studied and applied in the field of air pollution cleaning and medical appliance sterilization [3,4], material surface modification, optical physics, and so on [5][6][7].…”

Section: Introductionmentioning

confidence: 99%

Corona discharge effect on charge and energy transfer in dielectric barrier discharge

Sun¹,

Liu²,

Dong³

et al. 2019

Phys. Scr.

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To study characteristics of corona discharge effect on dielectric barrier discharge (DBD) with small curvature radius electrodes, two sets of comparative experiments were conducted on plate-plate with multi-needle-plate electrode structures and plate-plate with microcavity-plate electrode structures. At first, V-Q Lissajous figures were employed to analyze the air-gap voltage and charge transport in the first part of the experiment, and the result showed that the transferred charge of the multi-needle-plate electrode structure was about 1.5 times that of the plate-plate structure under the same power consumption. The second part of the experiment verified the above result, that is, the corona discharge effect on the microcavity produced a greater amount of transferred charge. Then, a reduced electric field was adopted to analyze the variation of average electron energy and the difference in molecular vibration temperature, and the corona discharge effect of the needle electrode on transfer of charge and energy are discussed. It was revealed that, in the non-uniform electric field of DBD, the local reduced electric field of the electrode tip with small radius of curvature was up to 750 Td, but the reduced electric fields in most of the air gaps were far lower than those of the plate-plate structure. Therefore, the average electron energy around the electrode tip was about 13 eV, which facilitates the collision and ionization of the electrons in air and the production of a large amount of charge. However, in this case, the temperature of molecular vibration was lower, and the excited particles generated in the discharge process were less than those generated by the plate-plate structure.

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Effects of Environmental Humidity and Temperature on Sterilization Efficiency of Dielectric Barrier Discharge Plasmas in Atmospheric Pressure Air

Cited by 12 publications

References 20 publications

Oral bacterial inactivation using a novel low-temperature atmospheric-pressure plasma device

Oral bacterial inactivation using a novel low-temperature atmospheric-pressure plasma device

Surface DBD degradation in humid air, and a hybrid surface-volume DBD for robust plasma operation at high humidity

Corona discharge effect on charge and energy transfer in dielectric barrier discharge

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