WO2021207771A1

WO2021207771A1 - Portable cold plasma sterilization device

Info

Publication number: WO2021207771A1
Application number: PCT/VN2021/000008
Authority: WO
Inventors: Thi Hong Lien LUONG
Original assignee: Luong Thi Hong Lien
Priority date: 2020-04-06
Filing date: 2021-04-02
Publication date: 2021-10-14

Abstract

The invention related to the portable cold plasma sterilization device to effectively and quickly sterilize the porous tools and objects for health protection against infections such as daily face masks, gloves, bandages, gauzes, makeup sponge, makeup brush, etc. The device according to the invention includes a power supply unit connected to a high voltage pulse generating system (1), a sterilization part (2) containing a plasma generator (2.1) according to the principle of Dielectric Barrier Discharge (DBD) on the mesh electrode (2.2).

Description

PORTABLE COLD PLASMA STERILIZATION DEVICE

Technical field

The invention relates to a portable cold plasma device for the sterilization of small, porous and flat objects. More specifically, the invention relates to a device that generates a cold plasma according to the principle of Dielectric Barrier Discharge (DBD) on the surface of a mesh electrode to sterilize objects such as face masks, gloves, wiper, makeup sponge, etc.

Background

With the growing need for protection against bacteria, viruses, and fungi, the use of disposable protective devices is wasteful and not environmentally friendly. For example, an effective protective face mask should be replaced after at most 4 hours of continuous use, or after each removal.

For a good sterilization of the foam material form like fabric, felt, nonwoven fabric, cotton, gauze, etc., in addition to solutions using autoclaves with humidity and high temperature (temperature of steam above 125°C for at least 20 minutes), objects that cannot withstand these conditions are often used other technologies such as CEb- CEbO, H-CHO gas, gamma or beta radiation, and low-pressure plasma in the form of plasma autoclaves. The radioactive systems as well as the low-pressure plasma sterilizers are cumbersome, complex, and take a long time to process, and these are suitable only for the needs of concentrated sterilization with large volumes. The use of CEb-CEbO gas must be very careful because it is very toxic and unstable, potentially explosive when exposed to oxygen in the air. H-CHO gas has the upper hand because it is less dangerous, however the processing time is still long, from one to two hours.

For many years, studies of cold plasma have proven that the sterilization of plasma is very effective, with the very important advantage that the sterilization time can be very short, only a few minutes of contact with the surface is enough to sterilization at 99.99%.

An article titled "Impact of food model (micro) structure on the microbial inactivation efficacy of cold atmospheric plasma" in 2017 investigated the possibility of cold plasma using Helium gas as a medium in different media such as in solution, on solid or porous surfaces (membrane filters). It is effective on all those three media with time variations between 3 and 10 minutes. There are many different principles for generating cold plasma in air, such as technologies that use gas exchange at low-pressure or atmospheric pressure. Systems using those principles are often complex and cumbersome.

Patent Document No. TW200938010 mentioned a compact handheld plasma device using the principle of atomized plasma, with the exchange gas being air at normal pressure. However, recent studies have shown that the use of the principle of direct discharge through the dielectric barrier has a higher bactericidal effect on plasma contact surfaces than the use of gas exchange principle (Figure 7) because the plasma is not diluted in the blown gas and is not expelled too quickly out of the surface to be sterilized.

Up to now, there is no device or invention referring to the use of the principle of direct discharge through the dielectric barrier for the sterilization of porous objects.

Summary of the invention

It's an objective of the present invention to provide a portable cold-plasma sterilization device to effectively and quickly sterilize tools and small porous objects for health protection against infections such as face masks, gauze, makeup sponge, makeup brushes, etc.

The device according to the invention includes a power supply unit connected to a high frequency high voltage pulse generating system and a sterilization part containing a plasma generator according to the principle of Dielectric Barrier Discharge (DBD) on the mesh electrode.

The device according to the invention also include a moving system arranged inside the sterilization part to provide a relative movement of the plasma generator on the mesh electrode surface or to move both on the surface to be sterilized.

The device according to the invention also includes a vibrating and/or pressing system located inside the sterilization part to increase the exchange of gas inside and outside the porous object consequently increasing the permeability of the plasma.

The device according to the invention also includes an additional air circulation part (not shown in the figures) arranged inside the sterilization part providing internal plasma circulation, from the plasma generator side to the object, to increase the penetrability of plasma into the object to be sterilized without diluting the plasma density in the sterilization part. The device according to the invention can be provided with heating unit to increase the temperature inside the sterilization part thus supporting the drying of the objects during sterilization. It can be combined with an electric fan device to blow hot air to the object surface or transfer heat to the mesh electrode in direct contact with the surface to be sterilized.

Advantageous effects of the invention

The device generates a cold plasma covering evenly and penetrating deeply into the porous layers of the object, to ensure the optimal sterilization. The device is compact so it can be carried in the bag, safe and easy to use and with minimum maintains cost.

Different from existing devices, the device according to the invention focuses on solving the problem of sterilizing the small cloth objects such as face masks, gloves, gauze, makeup sponge etc. that the user can easily carry.

The technology generating plasma directly on the surface to be sterilized with the principle of DBD on the mesh electrode contacting the object permits a closed minimum gas space without the need for a cumbersome air regulating system or the need to lower internal pressure. By the device according to invention, the objects can be sterilized in just a few minutes, ten seconds for a smooth surface to ten minutes for a laminated face mask.

Another feature of this device compared to other sterilization devices such as a compact UV light sterilization device is that it produces plasma with more efficiency and lower energy, the sterilization is still very good, plasma penetrates easily in porous objects that UV light cannot handle.

The principle of the dielectric barrier discharge through the surface of the mesh electrode is the one that do not use gas exchangers. It has the advantage of being compact, convenient, inexpensive and does not use consumable materials (inert gas,

...)

Furthermore, this device can also be used to sterilize other small non-porous objects such as knives, scissors, surgical suture needles, dental accessories, etc.

Brief description of drawings

Figure 1 is a perspective view of the device according to the invention; Figure 2 is a perspective view of the device according to the invention in which the cover of the sterilization box is opened;

Figure 3 is a schematic diagram showing how to generate plasma in the sterilization part;

Figure 4 is a perspective view of the device representing the motion system carrying plasma generator;

Figure 5 an exploded perspective view of the electrical impulse generating system of the device according to the invention;

Figure 6 an exploded perspective view of the sterilization part of the device according to the invention;

Figure 7 shows a P. aeruginosa bactericidal test on agar using a direct DBD plasma (left) and a spray plasma (right);

Figure 8 shows a schematic representation of a descending sine-shaped electric pulse emitted by a high frequency-high voltage transformer in the device according to the invention;

Figure 9 shows the structure of the sterilization part for an application of the device according to present invention.

Detailed description of the invention

The following detailed description is provided to help the reader in gaining a comprehensive understanding of the device described herein. The various parameters, variations and equivalents of the devices 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 portable cold plasma sterilization device according to the invention comprises:

- a high voltage pulse generating system 1, in which this system includes: - an electronic control circuit board 1.3,

- a high frequency-high voltage transformer 1.6,

- user control panel 1.4,

- an insulating sheath 1.1 exposing only a sterilization part connection

1.7 and a power supply connection 1.2

- a power supply 1.5 in which the power supply of the device can be either a normal battery, a rechargeable battery or any other power supply that gives the circuit board a direct or alternating current.

- a sterilization part 2 in which this part includes:

- a plasma generator 2.1 using the dielectric barrier discharge (DBD) principle;

- a storage compartment to store the objects to be sterilized 2.3;

- a mesh electrode 2.2 provided inside the storage compartment between the plasma generator 2.1 and the objects to be sterilized 2.3 and connected to the ground wire (neutral wire) of the electrical impulse generating system.

As shown in figure 3, the sterilization part consists of a DBD plasma generator 2.1 connected to the output of the transformer coil 1.6, a mesh electrode 2.2 in parallel and possibly in contact with the dielectric barrier of the generator 2.1. The object to be sterilized 2.3 comes in contact with the mesh electrode on the other side of the generator. All are housed inside a storage compartment. This compartment is closed during operation thanks to the housing 2.8 and cover 2.7 and opens only when stopped. The mesh electrode 2.2 is connected to the ground wire (neutral wire) of the high voltage pulse generating system 1 to close the circuit.

Inside the sterilization part, there may also be a moving system 2.6 to move the generator 2.1 relatively to the surface of the mesh electrode 2.2 or to move both the generator and the mesh electrode on the surface of the object to be sterilized 2.3 or vice versa to move the object to be sterilized back and forth through the active area of the generator if the generator size is smaller than the size of the surface to be sterilized.

In addition, in the sterilization part 2, there may be a vibrating systen 2.4 and/or pressing system 2.5 acting on the porous object to increase the air exchange inside and outside of the object and increase the penetration of plasma. The device according to the invention may be provided with an additional air circulation part, for example an electric fan, inside a closed sterilization box to push plasma from the generator side to the layer of the object to be sterilized, thereby increasing the penetration of the plasma into the object to be sterilized evenly.

The device according to the invention can be provided with heating unit which increases the temperature inside the sterilization part in order to support the drying of the objects during sterilization. It can be combined with an electric fan device to blow hot air to the surface of the object or transfer heat to the mesh electrode in direct contact with the surface to be sterilized.

The basic feature of the control circuit board 1.3 is to convert direct current from the power source to a series of electrical pulses transmitted to a high frequency high voltage transformer 1.6 according to predetermined programs with pre programmed pulse parameters in the circuit microcontroller/microprocessor. The control electronic circuit receives control commands and pulse parameters from the user control panel 1.4 and/or from the smart device connected to it through the IoT connectivity.

The elementary electrical pulse that produces a series of electrical impulses generated by the high-frequency high voltage transformer is a damped sinusoidal pulse. The characteristic of this pulse is that the first sinusoidal half has a high amplitude but a short width while the second sinusoidal half has a smaller amplitude but larger width to create capacitive balance and generate a polarized plasma. The polarity sign of the plasma stream depends on the polarity sign of the first sinusoidal half. The shape of such electrical pulses empowers the activation of the plasma's formation from air with as little energy as possible while still producing a mixture of highly efficient reactive ingredients.

The oscillation frequency of the sine wave is calculated to match a frequency (a few kHz to a few hundred kHz) that consistently forms a plasma in the air with tiny streams (no more than a few tens of micrometers). The oscillation frequency of the sine wave also depends on the output voltage, the distance between the electrodes, etc. An example of an application in a portable cold plasma device according to the present invention is to have an oscillation frequency of lOOkHz with the highest pulse voltage about 6 kV to create a uniform plasma within the distance between the electrodes less than 1 mm.

In order to optimize the conversion of electrical energy into the plasma, the important technical features of a mesh electrode structure are the cross-sectional shape of the wire mesh, the thickness of the mesh, the porosity of the electrode and the size of the pores.

The shape of the wire mesh cross-section should be such that the projected area being perpendicular to the dielectric barrier is as small as possible. In the case the mesh electrode is in contact with the dielectric barrier, it is advisable to choose a mesh wire with circular cross-section so that the contact area would only be small contact points. However, other shapes of wire mesh cross-sections are possible and the inventions is not limited to the wire mesh with circular cross-section.

The thickness of the mesh electrodes should be as small as possible and the porosity of the mesh electrodes should be as high as possible, as long as it still ensures the necessary mechanical strength and electrical conductivity. Optimal parameters of the porosity should be between 50% and 90%. The thickness of the mesh is not more than the optimal discharge distance. This distance depends on the electric field between the two electrodes. For example, for a pulse generator with a voltage of 6 kV and a dielectric barrier’s thickness of less than 1 mm, the maximum plasma discharge distance is about 2 mm and the optimal is about 1 mm. This is the distance produced by the small, uniform, and continual plasma stream on the surface of the electrode. However, the invention is not limited by the thickness of this mesh.

The size of the pores of the mesh electrode should be selected in a range from 0.5 to 3 times the optimal discharge distance, the optimal is 1 time but also not less than 0.5 mm. The pore shape can be round, oval, square, rectangle, honeycomb, triangle, etc. The above pore size is the smallest size. The largest size is not limited.

The mesh electrode can also be part of the object itself, covering the sterilized surface of the object and connecting to the device during processing.

The processing time of the device can be adjusted according to the thickness of the object to be sterilized manually or automatically according to the preset program depending on the thinness or lightness of the object measured by device.

Examples For different usage needs, there will be different architectures of the device.

One of the applications of the present invention is a personal device. In this case, it is not necessary to have an automatic vibrating and pressing system but use your hand to press repeatedly on the elastic cover (2.7 and 2.8) of the sterilization box, or gently shake the sterilization box with your hand if the object is solid during handling.

The system of moving the generator can be done manually (pull the handle connected to the generator) or pull the object repeatedly through the plasma generating area. Thus, the device will be simple, compact and inexpensive and suitable for individual needs.

Another structure may not require a cover the incubator-type sterilization part contains the generator and mesh electrodes. The sterilization part is formed by placing the incubator over a surface containing the object to be sterilized or a portion of the surface to be sterilized. The user can move the sterilization incubator on the surface of the object to be sterilized during handling such as an iron or step-by-step interruption. This structure of the device allows to sterilize the large objects.

For the needs of many people, such as schools, hospitals, clinics, factories, hotels, etc., the device can be fully automated. In this case, there will be two generators working together on the top and bottom of the sterilization box to increase efficiency and reduce processing time.

The moving system of the generators will be performed automatically by the motion system 2.62 connected to the motor 2.61. This motor is controlled by electronic control circuit 1.3 or a separate electronic circuit. There are also sensors 2.63 that help control the operation of the motion system so that during processing, the generator is moved steadily to create a uniform plasma across the surface to be processed.

To ensure safety, a sensor 2.9 is connected to the control electronic circuit 1.3 to automatically stop the operation when the cover 2.7 is opened, or in the absence of a cover, when the incubator is not closed.

Another motion system acts like a printer, placing the object to be sterilized into a conveyor or an opening. The motion system will automatically push the object to be sterilized through the plasma generating area at the appropriate speed to thoroughly sterilize this object. For objects in the form of bags, socks, gloves, etc. which need to be sterilized inside, the plasma generator can be designed according to the principle as shown in figure 9.

Figure 9 shows a structure of the sterilization part for an application of the present invention. In which the plasma generator is an electrode plate 2.11 connected to a high frequency-high voltage transformer 1.6 surrounded by a dielectric barrier 2.12 for both sides and surrounding of the generator. The mesh electrode 2.2 can be a double plate or two separate plates clamped on either side of the generator and connected to the ground circuit of the control board 1.3. The object to be sterilized 2.3 is enveloped in the outside of these mesh electrodes.

In addition, both aforementioned types of generators can be combined for sterilizing inside and outside of the pocket shaped objects to shorten sterilizing time.

For rigid, non- foldable face masks, the sterilization box can be designed with a mannequin- shaped structure. The principle of a plasma bulb can be used as a generator in combination with a mesh electrode covering the outside of the bulb.

Another application of the invention is integrated on production lines of small products that need to be sterilized before packaging. In the industrial revolution 4.0, this technology has the advantage of being very compact, easy to install or remove from the automation production line, creating the ability to change quickly on demand.

Claims

WHAT IS CLAIMED

1. A portable cold plasma sterilization device includes: a power supply (1.5); a high voltage pulse generating system (1); a sterilization part (2) includes a plasma generator (2.1) and a storage compartment for storing the object to be sterilized; characterized in that the device also includes: a mesh electrode (2.2) which is located in the storage compartment between the plasma generator (2.1) and the object to be sterilized and connected to the neutral wire (ground wire) of the electrical impulse generating system or ground.

2. The device according to claim 1, in which the high-voltage pulse generating system (1) consists of high frequency high voltage transformer is capable of converting the electrical pulse of the control circuit into a damped sinusoidal pulse characterized by the first sinusoidal half having a high amplitude but a short width while the second sinusoidal half having a smaller amplitude but larger width to create capacitive balance and generate a polarized plasma.

3. The device according to claim 1 or claim 2 in which the plasma generator is operated according to the principle of Dielectric Barrier Discharge (DBD).

4. The device according to any one of claims 1 to 3, in which, inside the sterilization part, there is also a motion system to relatively move the generator on the mesh electrode surface or move both of them on the surface of the object to be sterilized or move the object to be sterilized back and forth through the plasma generating area.

5. The device according to any one of claims 1 to 4, in which, inside the sterilization part, there is a vibrating and/or pressing system acting on the porous object to increase the gas exchange inside and outside of the object to increase the penetration of plasma.

6. The device according to any one of claims 1 to 5, in which, inside the sterilization part there is a gas circulation system to create plasma circulation inside the closed sterilization part from the generator side to the object to be sterilized to increase the penetrability of plasma in the object to be sterilized without diluting the plasma density in the sterilization part.

7. The device according to any one of claims 1 to 6, in which inside the sterilization part, a heating unit is provided to increase the temperature inside the sterilization part so that the drying of the objects is promoted.

8. The device according to claim 7, in which inside the sterilization part, a hot air fan is provided to circulate air inside the sterilization part.

9. The device according to claim 7 or 8, wherein the heating unit transfers heat to the mesh electrode, increasing the temperature of the electrode in contact with the surface to be sterilized.

10. The device according to any one of claims 1 to 9, in which the mesh wire cross- section of the mesh electrode is circular.

11. The device according to any one of claims 1 to 10, wherein the porosity of the mesh electrode is between 50% and 90%.

12. The device according to any one of claims 1 to 11, wherein the thickness of the mesh is not more than the optimal discharge distance.

13. The device according to any one of claims 1 to 12, in which the size of the pores of the mesh electrodes is in the range from 0.5 to 3 times of the optimal discharge distance, preferably 1 time but not less than 0.5mm.

14. The device according to any one of claims 1 to 13, in which the mesh electrode is detachable, completely independent from the device and connected only when the device is active.

15. The device according to claim 14, in which the mesh electrode is a part covering the surface of the object to be sterilized and is connected to the device during the sterilization.