Room temperature direct current air plasma jet for biomedical applications

Summary form only given. Atmospheric-pressure room-temperature plasma jets are commonly used in plasma medicine, nanotechnology, as well as surface and materials processing. Most of the applications require room-temperature operation while completely avoiding the glow-to-arc transitions. To meet these requirements, the atmospheric plasma jets are usually sustained in noble gases. However, this is very challenging for the open-air operation. Moreover, the cross-sections of the plasma plumes are typically very small, which make large-area surface processing particularly difficult. One promising way to overcome this shortcoming is by using the plasma jet arrays. However, since the individual plasma plumes generated by the arrayed plasma jets are in most cases independent and do not merge in open air, it is very difficult to achieve uniform plasmas and surface treatment effects. In this paper, we demonstrate a homogenous cold air plasma glow with a large cross-section generated by a direct current power supply. There is no risk of glow-to-arc transitions, and the plasma glow appears uniform regardless of the gap between the nozzle and the surface being processed. Detailed studies show that both the position of the quartz tube and the gas flow rate affect the plasma characteristics. Further investigation indicates that the residual charges trapped on the inner surface of the quartz tube may be responsible for the generation of the air plasma plume with a large cross-section. Moreover, the spatially resolved optical emission spectroscopy reveals that the air plasma plume is uniform as it propagates out of the nozzle. The air plasma plume with remarkable improvement of the plasma uniformity is used to improve the bio-compatibility of a glass coverslip over a reasonably large area. This improvement is demonstrated by a much more uniform and effective attachment and proliferation of human embryonic kidney 293 (HEK 293) cells on the plasma-treated surface.