Controlling filament pattering by microsecond-pulsed dielectric barrier discharge plasma for biomedical applications

Abstract

Research investigating the use of non-thermal plasmas for biomedical application has shown plasmas can enhance both survival and death depending on the application. For example plasma can both enhance wound healing [1] cell differentiation and tissue development [2] and induce apoptosis in cancer cells [3]. All of these studies have been performed using either or both types of non-thermal plasmas; plasma jets and dielectric barrier discharge plasmas (DBD). Plasma jet treatments are usually applied to a liquid while DBD plasma treatment can be applied directly cell and tissue surface. Additionally, depending on the application the DBD electrode size can be modified to treat larger surface areas with a single treatment. However, this can affect the discharge characteristics, including streamer and filament formation and patterning, which in turn can result in cell and tissue damage. Therefore controlling the filament patterning, including filament distribution and speed in atmospheric air is of a great concern for biomedical application. In this work we report the range of parameters affecting the filament pattern and their effect on plasma characteristics such as OH-production and reduced electric field. We tested discharge condition at the power range of 0.105 W to 2.1 W for three electrodes with area of 4.15 cm2, 2 cm2 and 0.83 cm2. Using discharge photographs and image analysis it was found that the larger area electrodes (4.15 cm2) for discharge frequencies below 1 kHz resulted in a fast filament kinetics, with a random distribution, contributing to a more uniform filling of the electrode area over time. Frequencies above 1 kHz for the same electrode resulted in repeated filament pattern over time which can cause damage to cells and tissue. In the smaller area electrode (0.83 cm2) fast filament movement was observed only for frequencies less than 500 Hz. In conclusion, DBD treatment uniformity can be controlled by optimizing discharge parameters and electrode area. Changing filament pattern can extended the biological application range for DBD discharges.