Fabrication of two types of atmospheric pressure microplasma jet sources: A capillary electrode and a single pin electrode surrounded by tapered insulator with eight holes (original) (raw)
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Electrical characterization of an air microplasma jet operated at a low frequency ac voltage
Journal of Physics: Conference Series, 2012
In this work a small plasma jet is generated applying an ac high voltage (kV) of low frequency (50 Hz) between two disk-shaped electrodes with a hole in the center and separated by a centrally perforated dielectric material. A plasma jet emerges from the electrode system to the room air when a large air flow rate is passing through the holes, for inter-electrode voltage drops around 1 ÷ 3 kV. The electrical characteristics of the discharge, voltage and current were studied varying the applied voltage amplitude and the gas flow rate. It was found that the microplasma jet was stable during a long period of time and the gas temperature remained almost at room temperature. These characteristics make this discharge suitable for biological applications.
A microfabricated atmospheric-pressure microplasma source operating in air
2005
An atmospheric-pressure air microplasma is ignited and sustained in a 25 µm wide discharge gap formed between two co-planar gold electrodes. These electrodes are the two ends of a microstrip transmission line that is microfabricated on an Al2O3 substrate in the shape of a split-ring resonator operating with a resonant frequency of 895 MHz. At resonance, the device creates a peak gap voltage of ∼390 V with an input power of 3 W, which is sufficient to initiate a plasma in atmospheric pressure air. Optical emission from the discharge is primarily in the ultraviolet region. In spite of an arc-like appearance, the discharge is not in thermal equilibrium as the N2 rotational temperature is 500–700 K. The intrinsic heating of the Al2O3 substrate (to 100˚C) causes a downward shift in the resonant frequency of the device due to thermal expansion. The temperature rise also results in a slight decrease in the quality factor (142> Q> 134) of the resonator. By decreasing the power supply ...
Individual ignition of RF microplasma array at atmospheric pressure
Plasma Processes and Polymers
Following the trend of miniaturisation in semiconductor industry, atmospheric plasma jets in array configuration were developed for cleaning or treatment of workpieces under homogeneous conditions. We describe here the first development of a small array of 5 individual identical plasma cells where each cell is ignited and quenched individually, which can be upscaled to several tens or hundreds of cells. The power electronics for ignition of plasma is composed of a multiplexing system with a kHz high voltage plasma ignition pulse and an RF-supply which can be distributed to each ignited cell to maintain the plasma in the respective cell. Experimental results show an ignition voltage for argon of 1300 V, and RF-current per cell of 70 mA.
Journal of Applied Physics, 2007
A rf microplasma jet working at atmospheric pressure has been characterized for Ar, He, and Ar/ CH 4 and Ar/ C 2 H 2 mixtures. The microdischarge has a coaxial configuration, with a gap between the inner and outer electrodes of 250 m. The main flow runs through the gap of the coaxial structure, while the reactive gases are inserted through a capillary as inner electrode. The discharge is excited using a rf of 13.56 MHz, and rms voltages around 200-250 V and rms currents of 0.4-0.6 A are obtained. Electron densities around 8 ϫ 10 20 m −3 and gas temperatures lower than 400 K have been measured using optical emission spectroscopy for main flows of 3 slm and inner capillary flows of 160 SCCM. By adjusting the flows, the flow pattern prevents the mixing of the reactive species with the ambient air in the discharge region, so that no traces of air are found even when the microplasma is operated in an open atmosphere. This is shown in Ar/ CH 4 and Ar/ C 2 H 2 plasmas, where no CO and CN species are present and the optical emission spectroscopy spectra are mainly dominated by CH and C 2 bands. The ratio of these two species follows different trends with the amount of precursor for Ar/ CH 4 and Ar/ C 2 H 2 mixtures, showing the presence of distinct chemistries in each of them. In Ar/ C 2 H 2 plasmas, CH x species are produced mainly by electron impact dissociation of C 2 H 2 molecules, and the CH x /C 2 H x ratio is independent of the precursor amount. In Ar/ CH 4 mixtures, C 2 H x species are formed mainly by recombination of CH x species through three-body reactions, so that the CH x /C 2 H x ratio depends on the amount of CH 4 present in the mixture. All these properties make our microplasma design of great interest for applications such as thin film growth or surface treatment.
The European Physical Journal D, 2010
Linear Stark splitting of the H β Balmer line components and spatially resolved optical emission spectroscopy (OES) measurements were used to estimate the electric field gradient in the cathode sheath region (∼70 μm long) of an atmospheric pressure direct current argon flow-stabilized microplasma jet. Also, plasma parameters in the negative glow region were investigated by both OES and electrical diagnostics. The microplasma jet was operated for current ranging from 10 to 110 mA. OH (A 2 Σ + , v = 0 → X 2 Π, v = 0) rotational bands at 306.357 nm and also the Ar 603.213 nm line were used to determine the gas temperature, which ranges from 600 to 1000 K. Electron number density, ranging from 4.
Applied Physics Letters, 2009
Bacterial inactivation experiment was performed using atmospheric pressure microplasma jets driven by radio-frequency wave of 13.56 MHz and by low frequency wave of several kilohertz. With addition of a ground ring electrode, the discharge current, the optical emission intensities from reactive radicals, and the sterilization efficiency were enhanced significantly. When oxygen gas was added to helium at the flow rate of 5 SCCM, the sterilization efficiency was enhanced. From the survival curve of Escherichia coli, the primary role in the inactivation was played by reactive species with minor aid from heat, UV photons, charged particles, and electric fields.
Ignition Delay for Atmospheric Pressure Microplasmas
Contributions To Plasma Physics, 2009
The ignition process in microplasmas is characterized by time resolved microwave reflection coefficient measurements, using a specially equipped vector network analyzer. We measured the time between the switching on of the microwave power and the onset of the plasma state in air at atmospheric pressures. The delay time decreases from approx. 3 ms to 60 μ s by increasing the microwave power from values just above the ignition threshold to higher values. A simple model shows the role of the free electrons in air and of the electrodes in the ignition process (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)