Radio-Frequency Oxygen Plasma as a Sterilization Source

Abstract

An oxygen plasma sustained at 13.56 MHz in a standardized reactor with a planar induction coil was used for biological decontamination experiments. Optical emission, mass spectrometry, Langmuir probe, and electrical measurements were applied to detection of chemical species and ion-energy and flux analysis. These diagnostics identified a plasma-mode transition in the range of 13-67-Pa pressure and 100-330-W power to the induction coil. At higher pressure and lower power, the plasma was sustained in a dim mode (primarily by stray capacitive coupling). A primarily inductive bright mode was attained at lower pressure and higher power. The coupling mode of plasma operation was then monitored by emission spectroscopy on an analogous, scaled-down reactor for biological degradation tests. Plasmid DNA degradation efficacies were compared in both plasma modes. DNA removal was ∼25% more efficient in the inductively coupled mode than in the capacitively coupled mode at the same power. The fast degradation was attributed to synergetic mechanisms (photo-and ion-assisted etching by oxygen atoms and perhaps O * 2 metastable molecules). Volatilization rates of the decomposition products (CO 2 , CO, N 2 , OH, H) evolving from the microbial (Deinococcus radiodurans) and polypeptide samples exposed to the plasma were compared. A plasma sustained in Martian atmosphere is considered.

Numerical Analysis of Microdischarge Oxygen Plasma and Prediction of Ozone Production Efficiency

“…Effectiveness of oxygen plasma in the sterilization processes is confirmed experimentally by Bol'shakov et al (1) , and it is shown that metastable molecules O * 2 ( 1 ∆ g ) and atomic oxygen O play an important role in microbial inactivation. These radicals prompt chemical alteration and volatilization of biological matters.…”

“…It can be said from the results obtained above that there is a high possibility to produce the optimal design by the numerical analysis because of the existence of maximal value of OPE. The focus of high density area of O 3 on the dielectric surface is the key technology of the sterilization in bioprocess (1) , and the optimal design of the sterilizer from the viewpoint of energy efficiency can be made by numerical simulation developed here, where the energy efficiency must be the practical knowledge.…”

Inactivation of Bacteria by Non-Thermal Plasmas

“…Taking into account the high efficiency of oxygen-based plasmas, literature on low pressure sterilization has mainly focused on these kind of plasmas, nevertheless, inert gas plasmas are in some cases still employed for bacterial inactivation (Liu&Chen, 2008. Recently, many studies (Bol'shakov et al, 2004, Boscariol et al, 2008, Cvelbar et al, 2006, Nagatsu et al, 2003, Rossi et al, 2008, Singh et al, 2009, Vicoveanu et al, 2008 on the effects of pure oxygen vacuum plasmas on bacteria have been conducted. Bol'shakov et al (Bol'shakov et al, 2004) published an interesting paper on the use of an oxygen RF plasma for sterilization purposes.…”

“…Recently, many studies (Bol'shakov et al, 2004, Boscariol et al, 2008, Cvelbar et al, 2006, Nagatsu et al, 2003, Rossi et al, 2008, Singh et al, 2009, Vicoveanu et al, 2008 on the effects of pure oxygen vacuum plasmas on bacteria have been conducted. Bol'shakov et al (Bol'shakov et al, 2004) published an interesting paper on the use of an oxygen RF plasma for sterilization purposes. The study was carried out for two operational modes: the inductively coupled mode and the capacitively coupled mode and it was found that the inductive mode offers a better efficiency in destroying bacterial cells.…”

Altering the sulfur content in the propanethiol plasma polymers using the capacitive-to-inductive mode transition in inductively coupled plasma discharge

“…In this case, the plasma has about one order of magnitude higher electron density and much stronger light emission, which both change abruptly at the transition power. [6][7][8][9][10][11][12][13][14] The E-H transition was a focus of both theoretical 7 and experimental 11-14 studies related to Ar, N 2, Ar/N 2 , O 2 , Ar/O 2 , H 2 , and Ar/H 2 plasmas used mainly for etching required, e.g., in semiconductor processing or in biological decontamination. Nevertheless, it has received little attention in the plasma polymer field.…”