A preliminary in vitro feasibility study for the use of a Floating-Electrode Dielectric Barrier Discharge (FE-DBD) plasma source to induce skin disinfection in the context of preventing neonatal sepsis is performed. The FE-DBD is a copper electrode, enclosed in an insulating material and a thin plate of quartz. The quartz is placed parallel above the substrate which is to be disinfected and is used as secondary electrode. Short damping kHz voltage pulses are fed to the electrode, which leads to filamentary microdischarges between the quartz and the substrate. By changing the pulse frequency, pulse width, duty cycle, gap distance and the to be treated surface, the properties of the plasma formed between the quartz and the substrate are affected. For different settings of these five variables, the relative light intensity, maximum voltage in one pulse and power dissipation in the plasma are studied. FTIR spectrometry is used to get quantitative insight in the chemistry in the discharge, but the path length was too short to obtain species densities.The effect of treatment of a FE-DBD on bacteria and skin is investigated. Staphylococcus aureus are placed with small drops on cover glass and treated for different settings. The inactivation of S. aureus is more effective and there is more light emission when the power dissipation in the plasma is higher. Also human skin with S. aureus is treated, the inactivation of bacteria is less effective. The inactivation of S. aureus is compared with the inactivation of three other staphylococci which are also found in neonates with sepsis and it is similar. Treatment of the skin did not show any clear difference in metabolic activity of the skin cells. The growth of the skin cells seems even to be stimulated for a more intense treatment. Histology shows local damage in the skin samples, the damage is very small and are therefore not causing a visible drop in the metabolic activity. The skin samples are not completely flat, a higher part of the skin will have a higher impact of discharges, which will cause this local damage. The detrimental effects on skin are a cause of concerns and the investigation of a plasma source that does not use the neonatal skin as second electrode is recommended based on the outcome of this study. A lot of research needs to be done to develop a safe and practical plasma source.
|Date of Award||31 Aug 2013|
|Supervisor||Gerrit M.W. Kroesen (Supervisor 1), P.J. Bruggeman (Supervisor 2), S. Bambang Oetomo (Supervisor 2) & B.K.H.L. Boekema (Supervisor 2)|