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.
A miniature atmospheric pressure glow discharge plasma torch was used to detach cells from a polystyrene Petri dish. The detached cells were successfully transplanted to a second dish and a proliferation assay showed the transplanted cells continued to grow. Propidium iodide diffused into the cells, suggesting that the cell membrane had been permeabilized, yet the cells remained viable 24 h after treatment. In separate experiments, hydrophobic, bacteriological grade polystyrene Petri dishes were functionalized. The plasma treatment reduced the contact angle from 93 • to 35 • , and promoted cell adhesion. Two different torch nozzles, 500 µm and 150 µm in internal diameter, were used in the surface functionalization experiments. The width of the tracks functionalized by the torch, as visualized by cell adhesion, was approximately twice the inside diameter of the nozzle. These results indicate that the miniature plasma torch could be used in biological micropatterning, as it does not use chemicals like the present photolithographic techniques. Due to its small size and manouvrability, the torch also has the ability to pattern complex 3D surfaces.
Abstract:The operating parameters of a miniature atmospheric pressure glow discharge torch (APGD-t) are optimized for the production of excited atomic oxygen, and the effect of the plasma jet on endothelial cells grown in Petri dishes is studied. We first demonstrate the importance of accounting for the effect of the voltage probe used to measure the electrical parameters of the torch on its ignition and operation characteristics. When operated with a main plasma gas flow rate of 1 SLM He and a power level of ~1 W, the torch shows an optimum in the production of excited atomic oxygen for a O 2 flow of ~3.5 SCCM injected downstream of the plasma-forming region through a capillary electrode (i.e., 0.35 v/v % O 2 /He). It is shown that endothelial cells are detached from the Petri dishes surface under the action of the optimized plasma jet and that this effect does not originate from heating and fluid shearing effects. It is postulated that the cell detachment is caused solely by plasma-induced biochemical processes taking place at the cell-substrate interface.
Summary: This article reports on the performance of a miniature APGD‐t conceived for the production of reactive species participating in bio‐applications. Two operating parameters were varied: the plasma‐forming gas flow rate (0.5–1.5 slm He) and the flow rate of O2 (0–50 sccm), which was injected downstream from the plasma‐forming zone, and which was used as a source of reactive species. The production of reactive species (O) was optimized, and the air entrainment in the plasma jet was minimized for a He gas flow rate of 1–1.5 slm and an O2/He volumetric ratio of 0.3 vol.‐%. A survey of the possible reaction pathways in the afterglow plasma jet suggests that the reactive species present in the plasma afterglow, and possibly reaching a remote substrate, are metastable He(23S), ground state O, OH, O2 (a1Δg), O2 (b1Σg+), N, N2, N 2+ and O3.
The paper highlights and provides solutions to the difficulties encountered with electrical probe measurements performed on a miniature, high capacitive impedance plasma device excited at 13.56 MHz. It is shown that a proper calibration of the phase angle between the circuit current and load voltage signals is required when commercial capacitive voltage probes (Tektronix P6139A and P5100 models) are used. A method to calculate the electrical characteristics of the plasma source and accounting for this calibration is described. The P6139A probe, which has the largest input capacitance and shortest cable length, introduced the smallest phase angle (−2 ± 1°), while the P5100 probe, which is used for higher input voltages and has a longer cable length, introduced a considerably larger phase angle (−34 ± 1°) for typical resistive loads. Simple circuit models are developed in an attempt to isolate the phase induced by the probe capacitance and cable length. The application of the proposed calibration to a miniature atmospheric pressure glow discharge source considerably reduced the error in the calculation of the power dissipated in the plasma device, though it remained relatively high (1 W ± 42%) due to the highly capacitive nature of the device.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.