Microhollow Cathode Discharge for Stable Atmospheric Plasma
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Solution Overview
Problem
Conventional plasma devices face challenges in generating stable non-thermal plasma jets at atmospheric pressure, often resulting in thermal instabilities and arcing, which limits their scalability and power consumption, and are not suitable for heat-sensitive materials or biological applications due to high process temperatures.
Innovation Solution
A microhollow cathode discharge assembly with a microhollow structure and direct current voltage is used to create a low-temperature, high-pressure plasma jet, employing a gas passage through closely spaced electrodes with a dielectric in between, allowing for stable glow discharges with a variety of gases, including air and oxygen, at atmospheric pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional plasma devices are used to generate plasma at atmospheric pressure, then plasma can be created, but thermal and electronic instabilities and arcing occur leading to electrode wear and high power consumption
Solution Approach 1:
The invention divides the plasma generation process into multiple micro-discharge channels formed by closely spaced parallel electrodes. Each electrode pair creates a confined micro-plasma channel, segmenting the overall plasma generation into many small, stable units that prevent macro-scale arcing and electrode wear while maintaining atmospheric pressure operation
Solution Approach 2:
The invention changes the electrical parameters by using alternating current at specific frequencies (e.g., 20-100 kHz) and adjusting the voltage amplitude to maintain non-thermal plasma conditions. This parameter control prevents thermal runaway and arcing while sustaining stable plasma discharge at atmospheric pressure
2Object-affected harmful factors
If linear dimension is reduced to reduce residence time and counteract instabilities, then arcing is reduced, but scalability and power consumption are affected
Solution Approach 1:
The invention segments the plasma generation into multiple parallel micro-channels between closely spaced electrodes. This segmentation allows each channel to operate at small scale (reducing arcing) while the overall system achieves scalability by increasing the number of parallel channels rather than enlarging individual channels
Solution Approach 2:
The invention transitions from reducing plasma volume in one dimension to distributing plasma generation across multiple dimensions by creating arrays of parallel electrode pairs. This dimensional approach allows scalability through spatial arrangement rather than volume reduction
3Reliability
If noble gases are used to generate stable plasma, then plasma stability is improved, but cost and applicability to heat-sensitive materials increase
Solution Approach 1:
The invention changes the electrical parameters (frequency, voltage amplitude, duty cycle) to match the specific ionization characteristics of air and other common gases. By optimizing AC frequency and voltage parameters, stable non-thermal plasma is achieved with air, eliminating the need for noble gases while maintaining plasma stability for heat-sensitive applications
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables the generation of stable, large-volume non-thermal plasma jets at near room temperature, suitable for heat-sensitive applications, with controlled temperature and radical species production, reducing arcing and power consumption, and enabling use on materials with low melting points and in biological tissues.
Implementation Method 1
A gas at a second pressure is provided wherein the second pressure is greater than the first pressure; another step is directing the gas through each of the at least one microhollow at the second electrode so as to create a plasma jet exiting the at least one microhollow at the first electrode
Implementation Method 2
Plasma is an electrically neutral, ionized state of gas, which is composed of ions, free electrons, and neutral species. As opposed to normal gases, with plasma some or all of the electrons in the outer atomic orbits have been separated from atoms and molecules
Implementation Method 3
Hollow cathode discharges are very stable, in part due to a 'virtual anode' that is created across the hollow. This virtual anode inhibits local increases in electron density by a corresponding reduction in voltage, reducing the likelihood of arcing
Implementation Method 4
This invention relates to the creation and use of a microhollow cathode, cold plasma jet discharge at atmosphere... enabling the creation of a stable, low-temperature plasma jet at atmospheric pressure, suitable for heat-sensitive applications, such as surface treatment and decontamination, with reduced power consumption and the ability to operate with common gases, achieving temperatures close to room temperature
Data Source
AI summary
A microhollow cathode discharge assembly capable of generating a low temperature, atmospheric pressure plasma micro jet is disclosed. The microhollow assembly has two electrodes: an anode and a cathode separated by a dielectric. A microhollow gas passage is disposed through the three layers. In some embodiments, the passage is tapered such that the area at the first electrode is larger than the area at the second electrode. When a potential is placed across the electrodes and a gas is directed through the gas passage, then a low temperature micro plasma jet can be created at atmospheric pressure or above.