Study of coaxial-dual-gap dielectric barrier discharge based on capillary: discharge characteristics and Escherichia coli decontamination.

Aims: The medical capillary catheters occupy a high proportion of medical diagnosis, monitoring, and treatment devices, and will cause serious cross-infection without being disinfected adequately. This paper presents a new plasma structure for efficient inactivation of harmful microorganisms in medical capillaries.

Methods And Results: An innovative coaxial-dual-gap dielectric barrier discharge reactor powered by nanosecond-pulsed power supply was designed for disinfection of Escherichia coli (E. coli) inside and outside medical capillary catheters in this work. Atmospheric helium plasma (AHP) and atmospheric air plasma (AAP) were successfully obtained inside and outside capillary (0.6 mm inner diameter and 1.0 mm outer diameter), respectively. The electrical and optical characteristics of AHP and AAP were investigated. As the threshold of applied voltage amplitude (Uamp) was <7.0 kV, only one helium glow discharge was generated inside the capillary at the rising and falling stages of pulse voltage. As the Uamp exceeded the threshold, two helium glow discharges were generated that further caused generation of air discharge. Under the Uamp of 9.0 kV, the production of AHP lowered the breakdown voltage in air gap, resulting in the formation of high-volume and uniform AAP, which was conducive to the realization of full inactivation. The inactivation rates of E. coli reached 98.13% and 99.99% by 2 min AHP and 0.5 min AAP treatment, respectively.

Conclusions: The electrical stress of AHP and the reactive oxygen and nitrogen species produced by AAP were contributed to the inactivation of E. coli. The results of SEM (Scanning Electron Microscope) show that plasma treatment can destroy the cellular structure of E. coli.