WO2021151123A1

WO2021151123A1 - Plasma generating unit and handheld plasma device containing the same

Info

Publication number: WO2021151123A1
Application number: PCT/VN2021/000002
Authority: WO
Inventors: Thi Hong Lien LUONG
Original assignee: Luong Thi Hong Lien
Priority date: 2020-01-21
Filing date: 2021-01-20
Publication date: 2021-07-29

Abstract

The invention refers to a plasma generating unit and a handheld cold plasma device that uses this plasma generating unit. The plasma generating unit according to the invention consists of electrodes and a dielectric barrier whose outer surface is hydrophobic allowing use in high humidity environments and ensuring stable and uniform plasma generation. The plasma generating unit according to the invention can have many different shapes, adapted to each objective and treatment site.

Description

PLASMA GENERATING UNIT AND HANDHELD PLASMA DEVICE

CONTAINING THE SAME

Technical field

The invention relates to a set of plasma generating units with hydrophobic outer surfaces.

The invention also refers to a device including parts for high-voltage pulse generating unit and a set of specified plasma generating units.

Background

The application of cold plasma to disinfect and promote the wound healing has become very popular.

Recent studies have shown that using the direct dielectric barrier discharge with floating electrodes has a much higher therapeutic (bactericidal) effect than the gas exchange principle (or plasma jet) (see diagrams compare direct plasma versus plasma jet in bactericidal tests as shown in Figures 1 to 3).

In the principle of direct plasma generation, unlike the indirect principles, the patient's body acts as the second electrode of the plasma electrode pair and the total plasma's current flow through the patient's body. This current promotes a wound healing.

One of the characteristics of direct plasma DBD is that the stability and uniformity of the plasma in the space between two electrodes is greatly affected by the distance between the active electrode (the plasma generating unit itself) and the passive electrode (the patient's tissue and skin). At the same time in the space between two electrodes there must have air to enable the plasma to be generated. In general, the distance between the two electrodes does not exceed a few millimeters to ensure that the plasma streams are not too concentrated, do not need high electrical energy that causes tingling, or even local bums.

Nowadays, there are many inventions interested in the stmcture of the plasma generating unit to optimize the efficiency of plasma production.

The publication of patent application number W02012097904 mentioned the dielectric barrier stmcture with protruding points to create the space between the generating unit and the wound surface. This structure does not allow it to move on the wound surface, so at the protruding points, the wound will not be treated.

Some DBD generating units are semispherical form for the purpose of generating a plasma in a circle surrounding the contact point, in an area where the distance between the two electrode surfaces is small enough to have plasma. This type of generating unit allows for easy movement on the treated surface. However, the ratio of effective area (where plasma generated) to contact area of this type of generating unit is usually not high.

In a humid environment, if on the outer surface of the dielectric barrier there are parts covered by a layer of conductive water, the plasma streams will be interrupted at those parts. Especially in the case of the generating unit who’s in contact with a wet surface. Phenomenon related to surface tension of hydrophobic materials will cause water to lift- up around the contact point and restrict the active area.

Typically, in case the surface to be treated is too wet, sprayed plasma (gas exchange) is used. But as we already know, these systems are relatively complex, cumbersome and expensive.

Regarding materials used for electrodes, US Patent No. US8725248B2 or scientific paper in 2008 “Nanosecond-Pulsed Uniform Dielectric-Barrier Discharge” shows that, to increase the lifetimes of the generating unit and reduce the energy consumption lost for heating the generating unit, the air bubbles formed between the electrode and the dielectric barrier should be minimized. Accordingly, the device proposed in these documents uses a liquid electrode in a dielectric housing.

In some other patents, for example the US Patent US8388618 B2, they are interested in the generating unit used in endoscopic surgery, in which the structure of the generating unit is relatively complex with the blowing and aspirating gas system.

Therefore, there is a need for a direct DBD plasma device that contains a plasma generating unit with a simple structure that optimizes plasma forming efficiency, durability and is able to be used in environments highly-rated in humidity, or on wet surface. Summary of the invention

It's an objective of the present invention to provide a direct DBD plasma generating unit with a dielectric barrier that uses hydrophobic material or a hydrophobic-treated outer surface that can be used in environments of high-rate humidity ensuring uniform and stable plasma emission with a long service life.

This invention also provides a handheld cold plasma device containing the plasma generating unit for a wide variety of clinical applications and is capable of being used by the patient himself. The device is capable of creating a uniform cold plasma, avoiding pains and ensuring safety, stability, ease of use and maintenance with minimal cost.

The apparatus according to the invention is programmed to be suitable for various applications such as: disinfection of open wounds, abrasions, postoperative wounds, chronic wounds, bums, skin disorder and diseases, oral hygiene or gynecological hygiene as recommended by a doctor. There is also an antiseptic aid for open or endoscopic surgeries.

Brief description of drawings

Figure 1 shows a P. aeruginosa killing test on agar using a direct DBD plasma (left) and a plasma jet (right).

Figure 2 shows killing time of P. aemginosa bacteria in a solution using direct DBD plasma and plasma jet.

Figure 3 shows a diagram showing bacteria killing time on damaged and healed skin using direct DBD plasma and plasma jet.

Figure 4 A is a perspective view of a plasma generating unit according to an embodiment of the invention and

Figure 4B is a longitudinal cross-section of this generating unit

Figure 5A is a longitudinal cross-section of the generating unit shows the region of plasma produced when in contact to the wound

Figure 5B is a perpendicular projection of the wound surface shows the active area of plasma generated Figure 6A is a longitudinal cross-section of the generating unit with hydrophobic surface showing the plasma area created when the wound is wet.

Figure 6B is a perpendicular projection of the wound surface shows the area of plasma generated when the surface is wet

Figure 7 shows the hydrophobic properties of the dielectric grid to ensure that no water can pass through but the air can still circulate

Figure 8 is a perspective view of a plasma generating unit according to one embodiment of the invention.

Figure 9 is a perspective view of a plasma generating unit according to other embodiment of the invention

Detailed description of illustrative embodiments

The following detailed description is provided to help the reader in gaining a comprehensive understanding of the equipment and the method described herein. The various parameters, variations and equivalents of the devices and methods described herein will be apparent to others skilled in the art.

It should be noted that the terms used in the invention description are not intended to limit the invention but are used only to allow a clear and consistent understanding of the invention.

Accordingly, it is apparent to others skilled in the art that the following description of the invention is provided for the illustrative purposes only and is not intended to limit the invention as determined by the accompanying claims and their equivalents.

The plasma generating unit according to the invention consists of an electrode covered with an insulating material, in which the outer layer facing the surface to be treated acts as a dielectric barrier.

Because of the high moisture content of the tissue and skin surface, in order to ensure the stability and uniformity of the generated plasma, the outer surface of the dielectric barrier must have a good hydrophobicity to avoid the formation of a water layer, reducing the surface resistance of the dielectric barrier, disrupting the formation of plasma in areas with this water layer.

In addition, to facilitate plasma creation with the lowest possible electrical energy, the selection of materials with a negative electrostatic coefficient (electron donation) as a dielectric barrier increases the potential for excitation, ionizing activity facilitate the generation of efficient plasma. In the electrostatic material list, the more placed at the bottom of the list, the more negative electrostatic the material is. For example, Teflon or some of the materials in the Fluoropolymer material group have both very high negative electrostatic properties and very good hydrophobicity, which will be better for use as a dielectric barrier.

However, Teflon has slightly weak mechanical properties. In cases where high mechanical strength is required, another dielectric material can be used and the outer surface of the dielectric barrier can be treated to obtain the desired performance e.g. by the polytetrafluorethylene polymerization treatment (PTFE) or fluorinated ethylene- propylene (FEP) polymerized by plasma on the dielectric barrier outer surface.

In order to avoid air bubbles or vacuum space forming between the electrode and the dielectric barrier which reduces the lifetimes, the generating unit can be produced by over molding. However, for small production series, this investment is too expensive, so the method used is usually cold casting by vacuum suction (for example pouring epoxy to fill the space inside the generating unit).

Examples

For different applications, different treatment areas, there will be different generating units.

Example 1

For wide and relatively flat treated surfaces, the dielectric barrier will have a constant thickness in the discharge zone. The generating unit has a multilayer structure with a concave form and convex-shaped electrode in the middle (Figures 4 A, B) specially designed so that the plasma discharge area around the contact circle between the generating unit and the treated surface is maximum (Fig. 5 A, B). That means, the concave zone has a depth equivalent to the distance optimum of discharge, plus the deformation of the treated surface under contact pressure. The best convex radius is at least 3 times the optimum discharge distance. For example, for an impulse generating unit with voltage of 6kV, the maximum plasma discharge distance is about 2mm, and the optimal is about 1mm. Generally convex radius is calculated so that the effective area is the highest. Usually it is between 4mm and 10mm.

In order to avoid air bubbles trapped between the electrode and the dielectric barrier, the electrode is a metal mesh or a perforated plate. In order for the electrodes to perfectly adhere to the complex 3D surface of the dielectric barrier, a good conductive varnish (containing metal particles or graphene e.g. corrosion resistant varnish zinc 300) is used as base layer adhesive lining electrodes with the dielectric barrier. This technique ensures that the electric field is transferred evenly across the surface inside the dielectric barrier.

For surfaces to be treated that are narrow or difficult to access, the contact part of the generating unit may be concave on one side and convex on the other (like a spoon).

Example 2

For endoscopic applications, the generating unit consists of a metal tube electrode portion coated with insulation thick enough that there will be no discharge except in the area with terminal grooves (Figure 8). There is a hydrophobic treatment mesh around the end part to prevent liquid from the treated area to fill inside and obstruct the space between this mesh and the grooves where the plasma is generated. The protective principle of this mesh (Figure 7) is that it does not allow water to penetrate but is very breathable, allowing the plasma to be released from grooves to the environment outside the mesh. Usually the size of the mesh pore is not more than a few hundred micrometers.

These grooves can be circled and can also run along the axis. The depths of these grooves match the plasma's optimum discharge distance.

Another structure of the terminal section doesn’t use hydrophobic protective meshes, but thanks to a brush-shaped hydrophobic dielectric layer with a bristles length not exceeding the optimum electrical room spacing and sufficient bristling density, provide the hydrophobic effect. Plasma is formed in the space between these bristles, example Figure 9.

Beneficial effect of the invention

With the hydrophobic treatment on the surface, the plasma generating unit according to the invention is capable of optimizing plasma forming performance in wet environments.

The plasma generating unit according to the invention are designed with shapes that are suitable for different processing locations.

With an electrically conductive varnish covering the active electrode in the assembly process, the structure of the plasma generating unit according to the invention is free from residual air bubbles, increasing its lifetimes.

Devices using this generating units can automatically detect the type of generating unit inserted and activate the appropriate therapy program.

Claims

1. A plasma generating unit consists of an electrode covered with an insulating material, in which the outer layer facing the surface to be treated and acting as a dielectric barrier has a hydrophobic character.

2. The plasma generating unit according to claim 1 , wherein the dielectric layer uses a hydrophobic material such as Teflon with a smooth outer surface.

3 . The plasma generating unit according to claim 1 , wherein the outer surface of the dielectric barrier has a hydrophobic treatment.

4. The plasma generating unit according to one of claims 1 to 3, wherein the electrode is a metal mesh or perforated metal plate coated with conductive varnish to facilitate adhesion to the dielectric barrier.

5. The plasma generating unit according to claim 4, in which the conductive varnish is the corrosion-resistant zinc varnish.

6. The plasma generating unit according to one of the claims 1 to 5, in which the generating unit is convex at the outer contour and concave in the middle.

7. The plasma generating unit according to claim 6, in which the convex radius is at least 3 times the distance of the optimum discharge.

8. The plasma generating unit according to claim 6 or 7, in which the convex radius is between 4mm and 10mm.

9. The plasma generating unit according to one of claims 1 to 5, wherein the generating unit has a spoon shape with a concave face and a convex face.

10. The plasma generating unit according to one of claims 1 to 5, where the generating unit also comprises tube electrodes, in which:

• the terminal in contact with the surface to be treated is covered with grooves; • The surface of the tubular electrode is covered with an insulating layer of sufficient thickness so that no discharge is observed except in the grooved area which is thinner to ensure plasma generation.

11. The plasma generating unit according to claim 10, in which the head is surrounded by a fine hydrophobic mesh to prevent the liquid presented in the treatment area from filling the grooves.

12. The plasma generating unit according to one of claims 1 to 5 where the generating unit consists of a tubular electrode, in which: the dielectric barrier in contact with the surface to be treated is in the form of a brush with a sufficiently thick bristle density to produce a hydrophobic effect, preferably the space between the bristles not exceeding a few hundred micrometers.

13. A handheld cold plasma device includes a system converting the energy from an electrical source into a series of high voltage pulses and connect to the plasma generating unit according to one of the claims from 1 to 12.

14. The handheld cold plasma device according to claims 13 in which the generating unit can be changed easily as desired.