Sterilization using a microwave-induced argon plasma system at atmospheric pressure

Abstract

The use of microwave plasma for sterilization is relatively new. The advantages of this method are the relatively low temperature, time-savings and its nontoxic nature, in contrast to traditional methods such as heat and gas treatment, and radiation. This study investigated the sterilization effects of microwave-induced argon plasma at atmospheric pressure on materials contaminated with various microorganisms, such as bacteria and fungi. A low-cost and reliable 2.45 GHz, waveguide-based applicator was designed to generate microwave plasma at atmospheric pressure. This system consisted of a 1 kW magnetron power supply, a WR-284 copper waveguide, an applicator including a tuning section, and a nozzle section. Six bacterial and fungal strains were used for the sterilization test. The results showed that regardless of the strain, all the bacteria used in this study were fully sterilized within 20 seconds and all the fungi were sterilized within 1 second. These results show that this sterilization method is easy to use, requires significantly less time than the other traditional methods and established plasma sterilization methods, and it is nontoxic. It can be used in the field of sterilization in medical and dental clinics as well as in laboratory settings.

Inactivation of Bacteria by Non-Thermal Plasmas

“…Therefore, UV photons are not likely to take part in the inactivation of micro-organisms when air plasmas are used. In contrast to the previous literature overview, some authors (Park et al, 2003, Heise et al, 2004, Lee et al, 2005, Trompeter et al, 2002 do mention the possible role of UV photons in plasma sterilization at atmospheric pressure, however, the arguments brought forward are quite often not fully convincing or incomplete (Boudam et al, 2006). For example, Trompeter et al (Trompeter et al, 2002) employed an atmospheric pressure filamentary DBD in different gases and found that argon was the most efficient gas in terms of spore inactivation.…”

“…We need to stress that the term sterilization is somewhat ambiguous since this term is only used when all initial micro-organisms are killed, which is however not always the case when applying non-thermal plasmas to contaminated surfaces (Boudam et al, 2006). Conventional sterilization methods include the use of dry heat (oven), moist heat (autoclave) or chemicals like gaseous ethylene oxide, liquid formaldehyde and glutaraldehyde (Kelly-Wintenberg et al, 1998, Moisan et al, 2001, Park et al, 2003. Some major drawbacks of these conventional techniques are the high processing temperatures (ovens and autoclaves) which makes it impossible to sterilize heat-sensitive materials like polymers, the use of toxic chemicals and the long sterilization times needed (approximately 12 hours in the case of ethylene oxide exposure) (Park et al, 2003, Moisan et al, 2001.…”

“…Conventional sterilization methods include the use of dry heat (oven), moist heat (autoclave) or chemicals like gaseous ethylene oxide, liquid formaldehyde and glutaraldehyde (Kelly-Wintenberg et al, 1998, Moisan et al, 2001, Park et al, 2003. Some major drawbacks of these conventional techniques are the high processing temperatures (ovens and autoclaves) which makes it impossible to sterilize heat-sensitive materials like polymers, the use of toxic chemicals and the long sterilization times needed (approximately 12 hours in the case of ethylene oxide exposure) (Park et al, 2003, Moisan et al, 2001. Another interesting sterilization method is the use of gamma irradiation, but this is an expensive technique and may cause the material to undergo undesirable changes during sterilization (Moisan et al, 2001, Henn et al, 1996, Ishigaki&Yoshii, 1992.…”

Inactivation of Bacterial Spore, Endotoxin, Lipid A, Normal Prion and Abnormal Prion by Exposures to Several Sorts of Gases Plasma

“…Nevertheless, the role of UV Trompeter et al, 2002Park et al, 2003Heise et al, 2004Lee et al, 2005 against spores was shown to be similar to what was observed for low-pressure plasmas. In addition, two further mechanisms that have not been observed with low-pressure plasma discharges are active in this case.…”

A 2.45 GHZ Reentarnt Coaxial Cavity for Liguid Sterilization Based on Non-Thermal Microwave Effect

“…Sterilization is typically based on either a physical or chemical process that destroys or eliminates microorganisms, or both [2][3][4]. Traditional methods including pasteurization, chemical and radiation sterilization are widely used in food industry.…”