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A portable microwave‐excited atmospheric pressure plasma jet (APPJ) using a coaxial transmission line resonator is introduced for applications of plasma biomedicine. Its unique feature includes the portability and no need for matching network and cooling system with high power efficiency, operating at 900 MHz with low ignition power less than 2.5 W in argon at atmospheric pressure. The temperature at the downstream of the APPJ stays less than 47 °C (≈320 K) during 5 min of continuous operation. The optical emission spectrum of the APPJ shows various reactive radicals such as OH, NO, and O which are responsible for biomedicine. The APPJ was applied to investigate the acceleration of blood coagulation, which occurred within 20 s of plasma treatment in vitro and within 1 min in vivo. This is significantly faster than the natural coagulation.

Using surface type air atmospheric pressure plasma, we investigated the amount of ozone and other reactive species generation with variations of the surface temperature of an electrode through an optical emission spectrum and a tube type gas detector. Reduced version of global model (GM) was employed to complement these experimental observations. The results of the model matched well with the experimental data. The amount of ozone generated from the surface type air plasma device was dramatically reduced with increasing temperature. Atomic oxygen (O) and nitric oxide (NO) radicals, which are important agents for biomedical applications, proportionally increased with increasing temperature. We also elucidated the dominant reaction related to the generation or loss of these radicals based on temperature variation through our GM.

A microwave-excited atmospheric-pressure plasma jet (uAPPJ) exhibited a synergistic sterilization effect when combined with hydrogen peroxide (H 2 O 2 ), distilled water (DW) and titanium dioxide (TiO 2 ) photocatalysis. The sterilization efficacy of H 2 O 2 -uAPPJ increased as the H 2 O 2 concentration increased. The addition of TiO 2 also remarkably increased the sterilization efficacy. To find the main factor for the sterilization effect, optical emission spectra and the degradation rate of a methylene blue solution were measured. Numerical analysis, a newly developed global modeling, was also conducted to discover the mechanisms. Both experimental measurements and global modeling results suggested that combinations of H 2 O 2 , DW and TiO 2 increased the generation of hydroxyl radicals (•OH), which are known to be strong bactericidal agents. It was revealed that charged species, especially electrons, have a dominant role in the increase of •OH.