An exploratory study of a novel enhanced corona discharge for sterilization

Author

Weng Lock Kang

Date of Award

5-2000

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Electrical Engineering

Major Professor

Igor Alexeff

Committee Members

Marshall Pace, J. Douglas Birdwell, Thomas Meek, Mark Rader

Abstract

Conventional methods of sterilization have their shortcomings and limitations. The methods used have recently raised public controversies concerning their environmental effects and other health issues. In an attempt to eliminate these drawbacks, new approaches based on different technologies are being investigated by researchers the world over. Among the approaches, plasma-aided processing is perhaps the most promising. This dissertation describes a novel enhanced corona discharge for sterilization. Reducing or avoiding the attachment of electrons to the oxygen molecules will enhance corona discharge at atmospheric pressure and ambient room temperature. Such enhancement has been achieved by replacing the air around the limited corona points with non-electronegative gases such as argon, helium, and nitrogen. Three configurations of electrode are constructed or designed for the purpose and an enhanced corona discharge sterilization apparatus is developed. By biasing a parallel pair of electrodes positively and negatively, two species of ions are created. The two streams of ions migrate into the bulk plasma, overcoming density limitation that usually occurs in a single-species corona discharge. Plasma characteristics such as the I-V relationship, local ion density, the spatial ion density profiles and ozone productions are analyzed. Plasma ion densities of the enhanced corona discharge have reached the order of 10¹¹ ion/cm³. In the sterilization tests, preliminary results indicate that the atmospheric pressure enhanced corona discharge is effective in sterilizing surfaces contaminated with microorganisms such as Escherichia coli and Bacillus subtilis cells. The bi-phasic killing curves reveal two different D values, a fester 29 seconds followed by a slower 104 seconds for E. coli. For B. subtilis, the values are 30 seconds and 485 seconds respectively. A 4.8 and 1.5 minutes of exposure times have resulted in a 6-log and 3-log reduction of E. coli and B. subtilis populations respectively. The antimicrobial mechanism of the enhanced corona discharge is not investigated but it is believed that charged particles, active free radicals, and radiation produced by the discharge have played a major role in the sterilization process. Though the sterilization tests on E. coli and B. subtilis are preliminary, the results are encouraging to merit a more thorough investigation in the future.

Recommended Citation

Kang, Weng Lock, "An exploratory study of a novel enhanced corona discharge for sterilization. " PhD diss., University of Tennessee, 2000.
https://trace.tennessee.edu/utk_graddiss/8317