A portion of the disclosure of this patent document contains material that is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent files or records, but otherwise reserves all copyright rights whatsoever.
This description relates to a system to produce a wide beam of non-thermal, atmospheric pressure partially ionized plasma with tunable properties using repetitive, fast rising electrical pulses.
Thermal atmospheric-pressure plasmas of large and small size are used for a variety of cleaning, coating, cutting and joining applications, but their high temperatures (many 1000's of degrees Celsius) limit their utility to materials that can withstand those high temperatures.
In order to broaden the applicability of the useful chemistries driven by atmospheric plasmas, a system for generating and delivering a wide beam of non-thermal, low temperature (below 50 degrees Celsius) partially ionized plasma with tunable properties has been developed based upon repetitive, fast rising, high voltage electrical pulses and a directed, high speed flow of gas. By using fast rising (greater than 100 V/ns), short duration (<100 ns) pulses, one generates a non-equilibrium plasma in which electrons receive the majority of the delivered pulse energy; the much heavier ion and neutral species in the plasma move too slowly to be directly effected by the fast electrical pulses. Increasing the energy of the electrons opens the door to new chemical pathways in atmospheric pressure plasma treatment, and limiting the energy delivered to the ions and other species reduces the amount of waste heat generated resulting in a much lower temperature output flow.
Briefly and in general terms, the present disclosure is directed to systems and methods to generate a wide beam of near-room temperature plasma using repetitive fast rising high voltage pulses. In the disclosed implementations, the fast rising pulses are transmitted to a plasma head via a coaxial cable. A source (e.g., fan, blower, compressor, reservoir of compressed gas) provides a moving stream of gas. The pulses are applied to the moving stream of gas via electrodes located at the plasma head. The partially ionized plasma that exits the head and its associated active species can be used to perform a variety of surface treatments such as cleaning, activation, disinfection, etching, and coating.
The system may optionally include an adjustable voltage output, an adjustable pulse repetition frequency, and an adjustable flow rate for one or more input gases. The input gas can be a noble gas such as helium or argon for achieving the lowest plasma stream temperatures near room temperature. Compressed air can also be used but with an attendant increase in the plasma stream temperature. The efficacy of the plasma can be tuned or optimized for each application by adjusting the amplitude of the voltage pulse, the repetition rate of the pulses, the velocity or composition of the flowing gas, or a combination thereof. While other atmospheric pressure plasma systems can also be used for cleaning, activation, disinfection, etching, and coating, their ability to optimize their performance for the specific application on a specific substrate is quite limited. For example, most atmospheric pressure plasma systems driven by an alternating voltage signal at a fixed frequency have only 2 or 3 output power settings which change the amount of energy pumped into the plasma. By using repetitive fast rising high voltage pulses, one can smoothly and independently tune key plasma features: increasing the pulse voltage (and the rate of voltage rise) creates different, higher energy radicals and active species, while increasing the pulse repetition rate raises the average number density of these usually short-lived active species.
In some implementations, a dimension (e.g., width) of the electrodes of the plasma head can be selected (e.g., more narrow or more wide) depending on the desired width of the plasma stream. In some implementations, the electrodes may be selectively replaceable in the plasma head, for example allowing an end user to select electrodes of a certain dimension to achieve a desired width of plasma, for instance based on a specific application for which the plasma will be employed. In some implementations, the plasma head may be selectively replaceable, allowing an end user to select a plasma head with electrodes of defined size to achieve a desired width of plasma, for instance based on a specific application for which the plasma will be employed.
The foregoing summary does not encompass the claimed subject matter in its entirety, nor are the illustrated or described implementations and embodiments intended to be limiting. Rather, the illustrated or described implementations and embodiments are provided as mere examples.
Other features of the disclosed implementations or embodiments will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the disclosed implementations and embodiments.
In the drawings, identical reference numbers identify similar elements or acts. The sizes and relative positions of elements in the drawings are not necessarily drawn to scale. For example, the shapes of various elements and angles are not necessarily drawn to scale, and some of these elements are arbitrarily enlarged and positioned to improve drawing legibility. Further, the particular shapes of the elements as drawn, are not necessarily intended to convey any information regarding the actual shape of the particular elements, and have been solely selected for ease of recognition in the drawings.
In the following description, certain specific details are set forth in order to provide a thorough understanding of various disclosed implementations and embodiments. However, one skilled in the relevant art will recognize that embodiments may be practiced without one or more of these specific details, or with other methods, components, materials, etc. In other instances, well-known structures associated with plasma generation and gas delivery systems have not been shown or described in detail to avoid unnecessarily obscuring descriptions of the implementations and embodiments.
Unless the context requires otherwise, throughout the specification and claims which follow, the word “comprise” and variations thereof, such as, “comprises” and “comprising” are to be construed in an open, inclusive sense, that is as “including, but not limited to.”
Reference throughout this specification to “one implementation” or “an implementation” or “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the implementation or embodiment is included in at least one implementation or embodiment. Thus, the appearances of the phrases “one implementation” or “an implementation” or “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same implementation or embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more implementations or embodiments.
As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the content clearly dictates otherwise. It should also be noted that the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.
The headings and Abstract of the Disclosure provided herein are for convenience only and do not interpret the scope or meaning of the implementations or embodiments.
The present disclosure relates to means of generating a low temperature (less than 50 degrees Celsius) wide plasma stream.
The pulsed voltage generator 104 of plasma treatment system 100 includes a power supply 200 (
The source of gas 106 of the plasma treatment system 100 may take a variety of forms that provide one a flow or flows of one or more gases to, or at least proximate, the plasma head 108. The source of gas 106 may, for example take the form of one or more reservoirs of compressed gas(es) and one or more compressors operable and fluidly coupled to increase a pressure of gas(es) in the reservoir(s), Alternatively or additionally, the source of gas 106 may include one or more fans, blowers or air movers operable to produce a stream or flow of gas(es). In at least some implementations, the plasma treatment system 100 may include one or more conduits 112 (e.g., hollow tubing) to deliver one or more gases (e.g., compressed gases) to the plasma head 108.
The supplied gas can be a noble gas (such as helium or argon) or compressed air and is provided at flow rates from 0.5 to 50 standard liters per minute (typically 5 SLPM). The flow rate should be high enough to provide a fast-moving gas channel that helps extend the plasma out from the plasma head 108 and into open air, but excessively high flow rates result in turbulent flow that causes the flow to quickly mix with ambient air upon exiting the plasma head 108 thereby quenching the plasma 102. Excessively small flow rates prevent the plasma 102 from extending past the plasma head 108 which limits the ability of the plasma 102 to reach and treat surfaces. The gas may include small amounts (1-5%) of reactive gases (such as oxygen or nitrogen) to encourage desired activation, cleaning, etching or disinfection chemistry in and around the plasma stream 102. Alternatively, the gas may include precursor chemicals that, after being mixed and energized in the plasma stream 102, are subsequently deposited on a substrate to form a desired coating. These precursor chemicals can be destroyed by the plasma 102 if it is too energetic, or they may fail to coat properly if the plasma 102 is not sufficiently energetic. It is important advantage of the described approach to be able to tune the plasma 102 properties in order to achieve the desired coating characteristics.
The plasma head 108 of the plasma treatment system 100 applies the incoming voltage pulses to the stream of moving gas. The electric field created by the voltage pulse is sufficient to ionize a small portion of the gas. The energetic free electrons drive reactions which create excited and reactive species from the surrounding air. The gas then exits the plasma head 108 via a wide exit slit 114 as a combination of charged and neutral particles that includes excited and reactive species.
The output of the pulse generator 104 may be of variable amplitude between 1 and 20 kV, but typically operates near 10 kV. The pulse generator 104 generates pulses that are less than 100 nanoseconds in duration, typically between 5 and 20 ns. These pulses repeat at a frequency between single shot up to 100 kHz, but typically in the range of 1 kHz. The average electrical power delivered to the electrodes of the plasma head 108 can range from a few Watts (for narrow plasma heads or mild plasma treatments) to 250 Watts (for wider plasma heads or more intense plasma streams). This approach is in contrast to available AC-driven plasma sources which typically require higher power, generate higher temperatures, and result in more narrow plasma streams with narrower windows of operation for the plasma parameters. By adjusting a combination of the applied voltage, the pulse repetition rate and the gas flow, the plasma stream can achieve various levels of strength with respect to numbers and types of reactive species (e.g., ozone, OH, excited oxygen, excited nitrogen). Thus, this plasma treatment system 100 (
As an example of the ability of the described plasma treatment system to perform desired surface activation on a temperature-sensitive substrate,
The surface of silicone is notoriously difficult to modify for adhesive applications. Even when silicone is successfully activated, the effect typically decays within minutes or even within seconds. The effectiveness of treatment with the described plasma treatment system for improving the strength of an adhesive bond between two pieces of silicone is shown in
In particular,
In particular,
The plasma head 108 includes a housing or body 300, a high voltage (HV) electrode PH1 carried by the housing or body 300, and a ground electrode PH2 carried by the housing or body 300 and spaced from the HV electrode PH1, as described below. The plasma head 108 includes a high voltage input, terminal or node 302 to electrically couple a high voltage to the HV electrode PH1, for example from a pulse generator 104 (
As previously discussed, the plasma head 108 includes an exit slit 114, via which gas and/or plasma 102 (
The plasma head 108 is where the incoming inputs of a voltage pulse and a gas flow are joined to result in the generation of partially ionized plasma 102 (typically less than 1%) that is then delivered through the exit slit 114. Where the plasma head 108 includes a baffle PH3, the incoming gas stream is mixed in the baffle PH3 in order to provide a more uniform flow through and across the exit slit 114. Non-uniformity in the gas flow results in non-uniformity in the plasma stream 102 (
The exit slit 114 of the plasma head 108 has a width W (
The dimension of the height H (
The electrically insulating material PH5 provides one of the enclosing walls or acts as a lid PH5 along which the gas and plasma flow. (The lid PH5 is shown as transparent in
The HV electrode PH1 inside the interior 306 of the plasma head 108 is in physical contact with the gas flow and the HV electrode PH1 ends 5-10 mm from the where the plasma stream 102 (
As an example of one of the benefits of the described plasma head geometry and described plasma treatment system,
Another benefit of this plasma head geometry is the ability to effectively treat over a range of plasma head-to-substrate distances. While some atmospheric-pressure plasma treatment systems are only effective up to distances of 2-4 mm,
Various embodiments of the devices and/or processes via the use of block diagrams, schematics, and examples have been set forth herein. Insofar as such block diagrams, schematics, and examples contain one or more functions and/or operations, it will be understood by those skilled in the art that each function and/or operation within such block diagrams, flowcharts, or examples can be implemented, individually and/or collectively, by a wide range of hardware, software, firmware, or virtually any combination thereof. In one embodiment, the present subject matter may be implemented via Application Specific Integrated Circuits (ASICs). However, those skilled in the art will recognize that the embodiments disclosed herein, in whole or in part, can be equivalently implemented in standard integrated circuits, as one or more computer programs running on one or more computers (e.g., as one or more programs running on one or more computer systems), as one or more programs running on one or more controllers (e.g., microcontrollers) as one or more programs running on one or more processors (e.g., microprocessors), as firmware, or as virtually any combination thereof, and that designing the circuitry and/or writing the code for the software and or firmware would be well within the skill of one of ordinary skill in the art in light of this disclosure.
When logic is implemented as software and stored in memory, one skilled in the art will appreciate that logic or information, can be stored on any computer readable medium for use by or in connection with any computer and/or processor related system or method. In the context of this document, a memory is a computer readable medium that is an electronic, magnetic, optical, or other another physical device or means that contains or stores a computer and/or processor program. Logic and/or the information can be embodied in any computer readable medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, processor-containing system, or other system that can fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions associated with logic and/or information. In the context of this specification, a “computer readable medium” can be any means that can store, communicate, propagate, or transport the program associated with logic and/or information for use by or in connection with the instruction execution system, apparatus, and/or device. The computer readable medium can be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, device, or propagation medium. More specific examples (a non-exhaustive list) of the computer readable medium would include the following: an electrical connection having one or more wires, a portable computer diskette (magnetic, compact flash card, secure digital, or the like), a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM, EEPROM, or Flash memory), an optical fiber, and a portable compact disc read-only memory (CDROM). Note that the computer-readable medium, could even be paper or another suitable medium upon which the program associated with logic and/or information is printed, as the program can be electronically captured, via for instance optical scanning of the paper or other medium, then compiled, interpreted or otherwise processed in a suitable manner if necessary, and then stored in memory.
In addition, those skilled in the art will appreciate that certain mechanisms of taught herein are capable of being distributed as a program product in a variety of forms, and that an illustrative embodiment applies equally regardless of the particular type of signal bearing media used to actually carry out the distribution. Examples of signal bearing media include, but are not limited to, the following: recordable type media such as floppy disks, hard disk drives, CD ROMs, digital tape, and computer memory; and transmission type media such as digital and analog communication links using TDM or IP based communication links (e.g., packet links).
The various embodiments described above can be combined to provide further embodiments. All of the above U.S. patents, U.S. patent application publications, U.S. patent applications, foreign patents, foreign patent applications and non-patent publications referred to in this specification and/or listed in the Application Data Sheet, including but not limited to commonly owned: U.S. Pat. No. 10,072,629; U.S. patent application Ser. No. 16/254,140; U.S. patent application Ser. No. 16/254,146; U.S. patent application Ser. No. 12/703,078; U.S. provisional patent application 62/699,475; U.S. provisional patent application 62/844,587, entitled “PULSED NON-THERMAL ATMOSPHERIC PRESSURE PLASMA PROCESSING SYSTEM” and filed on May 7, 2019 (Attorney Docket No. 910235.408P1) and U.S. provisional patent application 62/844,574, entitled “A METHOD FOR APPLYING A PLASMA RINSE TO FINGERNAILS” and filed on May 7, 2019 (Attorney Docket No. 910235.407P1) are each incorporated herein by reference, in their entirety.
The various embodiments and examples described above are provided by way of illustration only and should not be construed to limit the claimed invention, nor the scope of the various embodiments and examples. Those skilled in the art will readily recognize various modifications and changes that may be made to the claimed invention without following the example embodiments and applications illustrated and described herein, and without departing from the true spirit and scope of the claimed invention, which is set forth in the following claims.
Number | Date | Country | |
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62844587 | May 2019 | US | |
62844574 | May 2019 | US |