Design and preliminary characterization of a miniature pulsed RF APGD torch with downstream injection of the source of reactive species

Abstract

The design of a miniature low-power atmospheric pressure glow discharge torch (APGD-t) and the results of its preliminary electrical and spectroscopic characterization are presented. A capacitively-coupled pulsed RF (13.56 MHz) helium plasma jet is formed in a converging confinement tube and O 2 is injected downstream in the plasma afterglow region through a capillary electrode. With 1 SLM He, the APGD-t produced a non-thermal plasma jet of 500 µm-diameter and ≈2.5 mm-long at power levels ranging from 1 to 5 W. At ≈1 W, the gas temperature and He excitation temperature near the nozzle exit were ≈50˚C and slightly below 2000 K, respectively. The breakdown voltage in 1 SLM He is approximately 220 V pk-to-0 . Careful electric probe measurements and circuit analysis revealed the strong effect of the voltage probe on the total load impedance. The injection of 10 SCCM O 2 through the capillary electrode led to the transport of atomic O further downstream in the plasma jet and to a slight increase of the He excitation temperature without significant effects on the electrical properties and jet length. Alternatively, the addition of an equivalent amount of O 2 (1 v/v%) to the plasma-forming gas affected the electrical properties slightly, but led to a drastic contraction of the plasma jet. The atomic oxygen production and transport conditions provided by the APGD-t are promising for precise bio-applications such as the treatment of skin tissues and cells.

Contrasting characteristics of pulsed and sinusoidal cold atmospheric plasma jets

“…It is worth mentioning that UV emission was found to be similarly weak in other studies of pulsed APGD jets. 10,13 This suggests that the APGD jets considered in this study are likely to enable applications through their reactive plasma species. Interestingly, optical emission intensities of the pulsed APGD jet were greater even though its power consumption was lower.…”

“…[2][3][4][5][6][7][8][9][10][11] The vast majority of APGD jets reported so far employ sinusoidal excitation, although it has been known that nonsinusoidal excitation, through voltage pulsing, for example, offers a useful freedom to further improve APGD performance. 12 Initial results from few reported studies of pulsed APGD jets 4,10,13 have shown their general similarity to and contrast with sinusoidal APGD jets. However, a direct comparison of pulsed and sinusoidal APGD jets remains elusive, thus casting an uncertainty of whether a pulsed APGD jet offers significant advantages.…”

“…12 The plasma power dissipated in our pulsed APGD jet was more than one order of magnitude lower than that found in previous studies of pulsed APGD jets. 10,13 Gas temperature was estimated using an optical spectroscopy technique 16 as shown in Fig. 3.…”

Photo-initiated chemical vapor deposition as a scalable particle functionalization technology (a practical review)

“…Moreover, the operating cost versus the equipment size usually increases exponentially for plasma systems. While it is possible to operate cold plasma discharges at atmospheric or near-atmospheric pressures [23,24,25], discharge volumes are severely limited and thus not appropriate for large-scale particle functionalization. Recently, PECVD has also been used for the growth of carbon nanotube [26].…”

Miniature atmospheric pressure glow discharge torch (APGD-t) for local biomedical applications

“…We recently developed a miniature RF (13.56 MHz) atmospheric pressure glow discharge plasma torch, the so-called APGD-t, whose characteristics are well suited for biomedical applications [12,13]. In the present article, we report on the main characteristics of the APGD-t, on the optimization of the O 2 /He ratio for the maximum production of O radicals, and preliminary experiments on cell detachment and removal.…”