Date of Award

Spring 2016

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Electrical/Computer Engineering

Committee Director

Chunqi Jiang

Committee Member

Loree Heller

Committee Member

Christian Zemlin

Abstract

Bacterial resistance to antimicrobial methods is a critical issue in many fields of medicine. This work describes the studies performed to characterize and optimize the bacterial inactivation effects of a non-thermal atmospheric-pressure plasma brush and plasma jet on a laminate surface inoculated with Acinetobacter baumannii and Staphylococcus aureus, and a cultivated Enterococcus faecalis biofilm, respectively. These treatments are pilot studies for eventual application to surface sterilization in hospitals and root canal disinfection. To evaluate bacterial inactivation, after treatment and recovery, the bacterial colony forming units (CFUs) are counted. Several different methods are used to optimize the antimicrobial effect. For the plasma jet, the optimal fraction of oxygen in the helium feed gas is determined, resulting in a 1.5 log (97%) bacterial inactivation. For the plasma brush treatment of a dry laminate environment, the addition of water to the feed gas and surface is investigated. These variations greatly alter the plasma chemistry, which is characterized for the plasma brush by the use of optical emission spectroscopy to detect the presence of excited reactive species. These and other species generated in the plasma plume play a large role in the deleterious effect of plasma on bacterial cells. In a humid discharge, bacterial inactivation is maximized at 0.6 log (75%), whereas adding water to the laminate surface before treatment yields a 4 log (99.99%) reduction in bacterial growth. Thus, while the optimized oxygen or water concentration in a noble feed gas improves inactivation effect of the plasma, the most significant criterion for maximal bacterial inactivation in these studies is the presence of water at the treatment surface.

ISBN

9781339862170

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