Plasma Diagnosis and Biomedical Application Using Linear Microwave Atmospheric- Pressure Plasma Generator

A new type of microwave-excited atmospheric-pressure plasma (APP) generator that uses the principle of a strip-line transmission line resonator is presented. The microwave plasma has a length of 30 mm, so it can treat a wide area at the same time. The impedance of the resonator was matched to 50 Ω without additional matching equipment by exploiting characteristic of quarter wavelength transmission line. The design of the resonator was double-checked by computer simulation for the purpose of generating stable microwave APP. Microwave plasma discharge of the resonator was operated with argon gas flow of 1 slm, net power of 2.3 W, and resonance frequency of 2.41 GHz. The plasma gas temperature was maintained below 40 °C for 30 min, so it is safe to use in biomedical applications. The intensity of optical emission spectrum was higher at the center than edges. The average of electron excitation temperature was 0.78 eV with a standard deviation of 0.03 eV (3.85%) in 20-mm range. Increase in the amount of reactive oxygen and nitrogen species expressed in the normal human dermal fibroblast cells after plasma treatment was confirmed using fluorescent reagent. This new type of microwave atmospheric plasma resonator is expected to be useful in various biomedical fields.