Plasma surface disinfectant and its method

Abstract

To provide a process for generating plasma on a surface to be sanitized or directly on the surface and a plasma rail device for this purpose.SOLUTION: A plasma rail device is a novel method and device for generating plasma in the immediate vicinity of a surface or slightly above the surface for surface treatment, specifically surface disinfection. The device generally includes a pair of electrodes held together by a frame. A feature of the device is a fan for holding and positioning the electrode in close proximity to the surface during treatment. By generating electrical discharge in a space surrounded by the electrode and generating plasma on and above the surface to be treated, the device can be placed outside an object during treatment.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to the application of cold plasma for surface treatment and sterilization, and more particularly to biocides with plasma for surface sterilization. Further, it relates to a method of directly generating a controllable and uniform plasma on a treatment surface to create desirable surface properties including sterilization.

Background Art

[0002] Cross-contamination and cross-infection can occur through airborne infection or via frequently touched surfaces. Bacteria can multiply on physical surfaces. For example, some bacterial species such as methicillin-resistant Staphylococcus aureus (MRSA) can survive on dry surfaces for more than 4 to 5 months, and viruses such as norovirus can survive for about a week.

[0003] In recent years, it has been proven that plasma technology is very effective for air disinfection (see, for example, Patent US8361402 B2, Apparatus for Air Purification and Disinfection, Tsui). Plasma is called the fourth state of matter and is a partially ionized gas composed of freely moving ions, electrons, and neutral particles. Although plasma is electrically neutral as a whole, it is conductive. Due to this property, electrical energy can be injected into the space occupied by the plasma. Depending on the operating conditions, plasma can be composed of charged particles (electrons and ions), excited species, free radicals, ozone, and ultraviolet photons, and can decompose chemical compounds and destroy microorganisms. The energy of electrons can be used for the excitation of atoms and molecules, thereby causing chemical reactions and / or emitting radiation. These emissions, especially those in the ultraviolet spectral region, can initiate photophysical and photochemical processes by breaking molecular bonds. High-energy electrons can break some chemical bonds of molecules, collide with background molecules to break molecular chains, cause ionization and excitation, and generate free atoms and radicals such as O, OH, or HO2. Radicals can attack harmful organic molecules and help decompose pollutants in the air. Dissociation of O2 provides the O necessary to combine with O2 to form ozone. Also, low-energy electrons can attach to neutral atoms or molecules to form negative ions, which can promote the reactions of pollutant decomposition and microorganism destruction. Furthermore, in order to be effective, usually, a delivery mechanism is required to deliver charged particles and active species to the surface to be treated.

[0004] Plasma can cause a gaseous discharge by electrical means, whereby a high voltage is applied to a set of electrodes, an anode and a cathode. When the applied voltage is high enough and greater than the breakdown voltage, an arc begins to occur between the anode and cathode electrodes. Prolonged use can cause problems of electrode degradation and overheating.

[0005] Several approaches for surface sterilization using plasma have been proposed, some of which deal with methods of delivering charged particles and other active species from a plasma generation device to the treatment surface. For example,

[0006] · Patent Application Publication US 20040005261 A1 (Plasma Sterilization Apparatus, Ko) describes sterilizing articles in a vacuum chamber by drawing in plasma and active species generated in a separate chamber.

[0007] · Patent US 7633231 B2 (Harmonic Cold Plasma Device And Associated Methods, Watson) describes the use of a plasma gun device with helium gas injection and a magnetic system to deliver plasma and active species to the surface to be treated.

[0008] · Patent US9236227 B2 (Cold Plasma Treatment Devices and Associated Methods, Watson et al.) describes the use of a plasma gun device to deliver highly charged ions and reactive species for suction by a patient.

[0009] · Patent US 9623132 B2 (Plasma-generated Gas Sterilization Method, Krohmann et al.) describes generating plasma from air to produce reactive nitrogen and oxygen species, contacting this with water to form a mixture, and then directing it towards the object to be sterilized.

[0010] · Patent EP 2052097 B1 (Plasma Surface Treatment Using Dielectric Barrier Discharges, Boulos et al.) describes a surface coating treatment using a plasma torch that supplies a coating material to the plasma torch.

[0011] In another known approach, the object to be treated is placed near where the plasma generation electrodes are located. Typically, as exemplified in the following documents, the electrodes are arranged in a sandwich or fabric-like manner.

[0012] · Patent Application Publication US 20120039747 A1 (Treating Device for Treating a Body Part of a Patient with a Non-thermal Plasma, Morfill et al) discloses a plasma generation electrode configuration in which a dielectric insulator is sandwiched between two electrodes, one in the form of a plate and the other in the form of a wire mesh. Surface discharge occurs on the surface of the dielectric insulator in the voids of the wire mesh. A similar sandwich electrode configuration is also disclosed in Patent Application Publication US 20180206321 A1 (Electrode Assembly and Plasma Source for Generating a Non-Thermal Plasma, and Method for Operating a Plasma Source, Morfill et al), covering the outermost sides (upper and lower) of the electrodes with additional dielectric insulators to form a five-layer structure.

[0013] · Also, Patent Application Publication US 20120039747 A1 discloses another configuration in which one set of electrodes is insulated and another set is exposed or insulated. This configuration is also disclosed in Patent US 7037468 B2 (Decontamination of Fluids or Objects contaminated with Chemical or Biological Agents Using a Distributed Plasma Reactor, Hammerstrom et al) and Patent Application Publication US 2005 / 0249646 A1 (Gas Treatment Apparatus, Iwama et al). In this configuration, plasma generation discharge occurs at the intersection of the intersecting electrodes.

[0014] Furthermore, in another known approach, as shown in the following example, an object to be processed is placed between a high-voltage electrode and a ground electrode.

[0015] · Patent US9295280 B2 (Method and Apparatus for Cold Plasma Food Contact Surface Sanitation, Jacofsky et al.) describes using plasma for surface sanitation where the treated surface serves as the ground electrode or a ground rod assembly is placed beneath the surface being treated (i.e., the surface being treated is sandwiched between the high-voltage electrode and the ground electrode).

[0016] In these prior approaches, additional mechanisms are required to deliver charged particles and other reactive species to the surface being treated by sandwiching the object to be processed between the high-voltage and ground electrodes or by confining the plasma generation discharge to the intersection of the dielectric surface and the electrode pair. Therefore, there is a desire to develop methods and devices that can generate plasma directly on or above the surface to be sanitized without the need for special delivery and configurational arrangements and without encircling the surface to be treated with the device. SUMMARY OF THE INVENTION

[0017] In view of the above-mentioned drawbacks present in the prior art, based on the above principles, the method and device of the present invention provide a process for generating plasma directly on or above the surface to be sanitized. This objective is achieved by using a plasma trail device.

[0018] The plasma rail device of the present invention embodies a novel method and device designed to generate plasma near or slightly above the surface for surface treatment, specifically surface sterilization. The device generally includes a pair of high-voltage electrodes and ground electrodes arranged with alternating polarities, that is, the high-voltage electrodes and ground electrodes are arranged alternately and powered by an AC power supply. The high-voltage electrodes are covered with an insulating dielectric. The ground electrodes may be bare or covered with an insulating dielectric. The pair of electrodes is powered by an AC power supply having a high-voltage electrode connected to the high-voltage end of the power supply and a ground electrode connected to the low-voltage end of the power supply. Discharge is generated in the space between the pair of electrodes and on the surface of the object to be treated.

[0019] In a first preferred embodiment, a system for surface treatment and sterilization is provided that includes: (a) at least one pair of electrodes, a high-voltage electrode and a ground electrode, where the high-voltage electrode is covered with a dielectric material providing electrical insulation and the ground electrode is bare or covered with a dielectric material; (b) a frame for holding and arranging the electrodes at a predetermined, preferably adjustable distance towards the surface to be treated; (c) a power supply for supplying a high-voltage alternating current to the electrodes; Thereby, the electrodes generate plasma in the space between the electrodes and on the surface of the object to be treated.

[0020] The power supply may be adjustable to adjust the amplitude, waveform period, and shape of the voltage applied to the electrodes so as to maximize plasma activity and minimize the generation of unwanted by-product gases. The insulator of the electrodes may be in the form of a dielectric tube made of glass or a plate.

[0021] The conductors of the electrodes may be made from a conductive sheet, mesh, or deposit.

[0022] The voltage supplied may be in the range of 10 kilovolts to 50 kilovolts.

[0023] The waveform period is 10 -1ms~10 2 It can be in the range of ms.

[0024] The distance between the pair of electrodes is preferably in the range of 1 mm to about 20 mm. The distance between the electrode and the surface to be treated is preferably in the range of 0 mm to 20 mm.

[0025] The method may further include adjusting the amplitude, waveform period, and shape of the voltage applied to the electrodes in order to maximize plasma activity and minimize the generation of unwanted by-product gases.

[0026] The device of the present invention has a high-voltage AC power source for controlling the amplitude, waveform period, and shape of the voltage applied to the electrodes, and as a result, operates with a plasma discharge under selected conditions. The high-voltage AC power source can be a high-voltage generator. The amplitude, waveform period, and shape of the voltage applied to the electrodes can be adjusted according to the desired treatment intensity and treatment time in a plurality of reactors. The system generally consists of a plurality of reactors arranged in alternating high-voltage electrodes and ground electrodes, and the configuration and overall size can be designed to provide appropriate treatment intensity and time.

[0027] The high-voltage electrode is covered with an insulator. The ground electrode can be bare or covered with an insulator. The insulating electrode includes an insulator that can be in the form of a dielectric tube or plate.

[0028] The system may further include a blower unit for driving air over the object to be treated in order to reduce heating of the object surface.

[0029] Generating plasma for directly treating the surface is an advantage of discharge generation on the surface of the object to be treated.

[0030] Another advantage is that a discharge occurs directly above the surface of the object to be treated in order to generate plasma for directly treating the surface.

[0031] A further advantage of at least one embodiment of the present invention is to provide a method and device for generating plasma directly on or above the surface of an object to be processed (including sterilization) without the need for the delivery or configurational arrangement of charged ions and reactive species, thereby overcoming the drawbacks of the prior art.

[0032] The various novel features characterizing the invention are pointed out particularly in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages, and the specific objects attained by its use, reference should be made to the drawings and the following description which illustrate preferred embodiments of the invention.

Brief Description of the Drawings

[0033] Hereinafter, specific embodiments of the invention will be illustratively described with reference to the following attached drawings.

[0034]

Figure 1

Figure 2

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Figure 9

Best Mode for Carrying Out the Invention

[0035] Here, a preferred embodiment of the present invention will be referred to in detail.

[0036] Referring now to the drawings, FIG. 1 generally shows the system components of a surface treatment system 1 including an electrode assembly 10 having a high voltage electrode 20 and a low voltage electrode 30, and an associated power supply 4 and controller 5. The power supply and controller generate and maintain a discharge having specific plasma parameters predetermined and controlled by a high voltage AC power supply. As shown in FIG. 1, the electrodes 20, 30 can be connected to a high voltage AC power supply 4 having an electronic control unit 5. The power supply 4 can supply a voltage sufficient to cause dielectric breakdown and plasma generation directly on or above the surface of the object to be treated (including sterilization) without the need for the delivery of charged ions and active species. The voltage supplied to the electrodes 20, 30 can be controlled within the range of 10 kilovolts to 50 kilovolts. The waveform period can be controlled within the range of 10 -1 ms to 10 2 ms.

[0037] Figure 2 shows a preferred embodiment of the electrode assembly 10 including the high-voltage electrode 20 and the low-voltage electrode 30. The electrodes are held in place by holders 11 and 12. In addition to the planar form, the assembly can take other forms such as a cylinder or a sphere. As shown in Figure 3, the high-voltage electrode 20 has a conductor 21 covered with an insulator 22 and a wire connection portion 23 to a power source. The low-voltage electrode 30 has a conductor 31 that can be bare or covered with an insulator 32 and a wire connection portion 33 to a power source. The insulator can be made of a dielectric material such as glass or ceramic in the form of a cylindrical tube as in this preferred embodiment. They can also be in the form of plates or made of any insulating or dielectric material. The insulator can also be in the form of a dielectric coating. The electrode conductors 21, 31 of the electrodes 21, 31 can be made of a conductive sheet, mesh, or deposit. The distance between the pair of electrodes 20, 30 can be in the range of about 1 mm to about 20 mm. A discharge is caused in the space surrounded by the electrodes to generate plasma on the surface of the object to be treated and thereon.

[0038] The electrodes can take other shapes. For example, they can take a wavy voltage electrode 120 as shown in Figure 4, and the same is true for the low-voltage electrode 130. The electrode assembly is not limited to the form of rails. In the embodiment shown in Figure 5, the ground electrode 230 is a conductive sheet having a circular notch for accommodating the insulated high-voltage electrode 220. Figure 6 shows another embodiment in which the insulated high-voltage electrode 320 is disposed in a hexagonal cutout of the ground electrode plate 330. Although the embodiments are shown in a planar form, the assembly can take other forms such as a cylinder or a sphere. As an additional feature shown in Figures 7a and 7b, the high-voltage electrodes 220 attached to the support 221 can be recessed behind the ground electrode plate 230 when not in use as shown in Figure 7a and moved to the operating position when they are used for surface treatment and sterilization as shown in Figure 7b. Another embodiment includes moving the ground electrode plate 230 so as to flash with the high-voltage electrode during surface treatment use.

[0039] It has been confirmed by comparative tests that the prototype device of the present invention (see Fig. 8) has better surface sterilization performance than the prototype device according to the prior art. In this test, bacteria were pre-loaded in a Petri dish and treated with corresponding devices operating under equivalent plasma conditions. In the photo of Fig. 9, each "dot" on the Petri dish represents a colony of bacteria. Fig. 9c is a "control" where the Petri dish has not been treated with any device, showing the initial concentration of bacteria. Fig. 9a shows the result of the Petri dish treated with the device of the present invention (the device shown in Fig. 8). Fig. 9b shows the result of the Petri dish treated with the device according to the prior art. Comparing Fig. 9a and Fig. 9b, the number of bacterial colonies in Fig. 9a is much less, indicating that the device of the present invention sterilizes the surface more effectively.

[0040] The electrode and frame assembly (e.g., according to the preferred embodiment of Fig. 2) can be applied to a smooth surface in a state where the surface of the electrodes (20, 30) is stationary on the surface to be treated or on the surface to be treated at a distance not greater than the separation between the electrodes (20, 30). In the preferred embodiment shown in Fig. 2, the separation between the electrodes (20, 30) can be in the range of 1 mm to 20 mm. The distance between the electrode surface and the surface to be treated can be in the range of 0 mm to 20 mm. A typical treatment time is from a fraction of a second to several seconds. The device of the present invention can simultaneously sterilize the air by sending air into the gap space between the electrode surface and the surface to be treated (e.g., using a fan).

[0041] In an alternative embodiment as shown in Fig. 5, the high-voltage electrode 220 can be attached to the movable support 221 to optimize the distance between the electrode tip and the surface to be treated.

[0042] The surface treatment is not limited to a surface smaller in size than the electrode assembly. The electrode assembly can be used to treat a large surface by sliding or moving it on the surface to be treated. Alternatively, the surface to be treated can also be moved under the electrode assembly. For example, the electrode assembly can be placed on the rubber handrail of an escalator, and the area under the electrode assembly can be continuously moved. Since the electrodes are placed on the surface where they move, physical contact can be avoided, and mechanical wear and breakage can be eliminated.

[0043] The treatment time for disinfecting the surface under the electrode assembly is several seconds. For an electrode assembly the size of a small notebook computer, the surface of a desk can be effectively disinfected in a few minutes. By attaching the electrode assembly to a mobile device (robot or drone), the mobile electrode assembly can disinfect the surface of a room in a few minutes. By flowing air through the gap space between the electrode surface and the surface to be treated (e.g., by the movement of the mobile device or using a fan), the device can simultaneously disinfect the air.

[0044] In the case of a curved surface, the frame (11, 12 in Figure 2) holding the electrodes can be shaped to curve according to the curvature of the surface to be treated. Furthermore, the holders (11, 12 in Figure 2) in the preferred embodiment can be made of a flexible material or configured in the form of a flexible chain so that the electrodes can be adapted to any curved surface. In an alternative embodiment as shown in Figure 5, the high-voltage electrode 220 is attached to a flexible support 221 together with a flexible ground electrode 230, the tip of the electrode can be adapted to any curved surface, and an optimal distance can be maintained between the tip of the electrode and the surface to be treated.

[0045] In the present invention, the distance between the electrode surface and the surface to be treated does not need to be fixed and can be varied within a reasonable range of 0 mm to 20 mm. Therefore, the device can disinfect not only smooth surfaces but also non-flat surfaces with surface irregularities of up to 20 mm.

[0046] In the device of the present invention, due to the structure and arrangement of the electrodes, it can be easily applied onto the surface of the object to be treated with the disinfectant. Compared with the devices of the prior art, the device of the present invention has a simple structure, is flexible, and is more effective in treating the surface. There is no particular need to ground the surface of the object, that is, the object to be treated substantially becomes a part of the electrical circuit. In the case of the frame, the basic requirement is that it can hold and arrange the electrodes at the necessary short distance towards the treatment surface. As long as the frame can meet such requirements, it can be constructed in various shapes and materials in various ways. For example, it can be made of a flexible material to treat a curved or irregular surface. Also, a fan mechanism for directing air towards the treatment surface can be incorporated. It can also have a wheel or slide mechanism to facilitate movement on the surface being treated. In the present invention, plasma treatment can be applied to various objects, for example, treating the surface of the button panel of an elevator and other structures in a shared area to reduce the infection and spread of viruses and bacteria in the community. This is because, unlike the devices of the prior art, there is no need to place the object between the electrodes. In addition to the uniqueness of the present invention to overcome some of the complexities of the prior art developments, the device of the present invention can disinfect the surface better than the devices of the prior art.

[0047] It should be understood that the expressions and terms employed herein are for the purpose of description and should not be regarded as limiting. Although the basic novel features of the present invention applicable to the preferred embodiments of the present invention have been described and pointed out heretofore, it will be understood that various omissions, substitutions, and changes can be made by those skilled in the art without departing from the spirit of the present invention in the form and details of the illustrated embodiments. The present invention is not limited by the above-described embodiments presented as examples, but can be modified in various ways within the scope of protection defined by the appended claims. Since the essence of the present invention lies not in technical difficulties or complexities but in the novel idea itself, it will be further understood that the present invention can be practiced without reference to these specific examples. If the idea is known, implementing it is within the scope of ordinary skill in the art.

Claims

Claim 1 A device for treating a surface, comprising: (a) at least a pair of electrodes arranged at a distance of 1 to 20 mm from each other and capable of generating plasma; (b) a frame for holding and positioning the electrodes facing the surface to be treated at a distance of 0 to 20 mm; (c) a power source for supplying a high-voltage alternating current to the electrodes; (d) a controller for controlling the generation and treatment process of the plasma, wherein the frame has a plurality of wheels for facilitating the movement of the device on the surface to be treated. Claim 2 The device according to claim 1, wherein one electrode has a high voltage and is insulated by a dielectric material, and the other electrode has a low voltage and is either insulated or bare. Claim 3 The device according to claim 1, wherein one electrode has a conductor in the form of a conductive sheet, mesh, wire, or deposit. Claim 4 The device according to claim 1, wherein the frame has a flat surface parallel to the plane formed by the electrodes, the distance in the vertical direction with respect to the plane is 0 mm to 20 mm, and the distance between the electrodes and the surface to be treated is determined. Claim 5 The device according to claim 1, wherein the frame has a curved surface adapted to the surface to be treated. Claim 6 The device according to claim 1, wherein the frame has a flexible surface capable of changing its shape suitable for the surface to be treated. Claim 7 The device according to claim 1, wherein the frame houses a fan or blower for sending air towards the surface to be treated. Claim 8 The device according to claim 1, wherein the frame has a sliding surface for facilitating the movement of the device on the surface to be treated. Claim 9 The device according to claim 1, wherein the power source can supply electricity with a voltage between 10 kV and 50 kV. Claim 10 The device according to claim 1, wherein the controller adjusts the power source and controls the amplitude, waveform period, and shape of the voltage applied to the electrodes to maximize plasma treatment and minimize the generation of unnecessary by-product gases. Claim 11 The waveform period is 10 －１ ms to 10 ２ ms, and the device according to claim 10 is in this range.

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