Enhancement of microwave plasma characteristics for biomedical applications using pulse modulation method

Summary form only given. Microwave plasma technique for biomedical applications has been studied and applied to several fields such as blood coagulation and sterilization. The microwave plasmas generally showed high electron temperature and high electron density, consequently the gas temperature higher than low frequency plasmas. For biomedical applications, especially for human body, it is required to have low temperature and high concentration of reactive species. Pulse modulation technique is one of possible methods to achieve the needs. Finger-size microwave generator and pulsed microwave power module using palm-size power module were developed. Gas temperature and emission spectra were measured with several duty ratios and a fixed average power. Gas temperature of Ar and Air plasmas reduced as the duty ratio reduced. In the case of Air plasma, the gas temperature reduced from 100° C to ~55° C. This caused by off-phase of the pulse modulated signal which was proportional to the reduction of duty ratio. On the other hand, the portion of reactive species including O and OH increased as the duty ratio reduced. This related to the momentary high power excitation. The technique embedded to a skin care system (Medipl Corp.) and blood coagulation experiment was conducted. While natural coagulation time was about 18 min, treated blood drops were coagulated in 2.5 min. Numerical analysis such as global and fluid modeling will also be presented.