Characterization of Atmospheric Pressure Microplasma Jet Source and its Application to Bacterial Inactivation

Atmospheric pressure microplasma jet sources driven by radio-frequency wave of 13.56MHz and by low frequency continuous wave of several kHz ac were fabricated and characterized. The source consists of an ac-driven copper wire (needle) surrounded by dielectric layer that are placed in a glass tube, and a ground plane electrode (pin-to-plane electrode configuration). The basic physical and chemical properties of the plasma jet sources, such as optical emission spectrum, gas temperature, and power deposition were investigated. With various geometrical and operational parameters changed, plasma jets showed different discharge characteristics. The geometrical parameters include the length of the pin wire exposed to the plasma, the distance between the pin to the outlet of the glass tube, and the distance between the pin and the plane electrode. The operational parameters include the applied voltage (amplitude and frequency) and the gas flow rate. As an example of biomedical application of the microplasma jets, the bacterial inactivation experiment was performed. Plasma power (or applied voltage), treatment time, and needle-to-sample distance were varied and the bacterial inactivation effects of these parameters were observed.