Impedance-matching flexible SDBD electrodes for skin surface treatment applications

Abstract

The present invention provides an impedance-matching flexible SDBD electrode for skin surface treatment applications. The high-voltage electrode and the ground electrode are arranged alternately on the SDBD electrode layer, an air gap is left between the high-voltage electrode and the ground electrode, the high-voltage electrode is connected to the positive pulse high-voltage potential interface of the power supply, the ground electrode is connected to the ground potential interface of the power supply, the ground electrode line wraps the high-voltage electrode line, the high-voltage electrode and the ground electrode surface are first crimped with polyimide, and then the human body contactable film material is crimped on the polyimide, the control electrode arranged at the bottom of the SDBD electrode layer is a whole layer of copper foil, the area wraps the entire plasma discharge area, and the control electrode and the ground electrode are connected to a matching impedance network. The present invention solves the problems of uneven discharge of flexible electrodes and breakdown during normal operation, especially in the actual application process, under the condition that the flexible electrode is bent at will, uniform discharge can be guaranteed, and normal operation can be stable at the same time, the electrode surface temperature is low, and the electrical safety and reliability.

Description

Technical Field

[0001] The invention belongs to the field of flexible SDBD electrodes and relates to an impedance matching flexible SDBD electrode for skin surface treatment application. Background Art

[0002] In our daily lives, our skin is often damaged due to various conditions. These injuries may be potentially devastating and may even lead to death. Timely treatment of such wounds has become a very important issue. Early treatment methods were mostly based on experience and traditional therapies, such as using herbs, alcohol, etc. to clean wounds, simple cloth or plant fiber bandages, etc. With the development of medicine, especially the discovery of aseptic techniques and antibiotics, wound treatment has made significant progress. Since the discovery of antibiotics in the early 20th century, they have greatly changed the field of medicine and enabled many infectious diseases to be controlled. However, the problem of bacterial resistance has emerged almost as soon as antibiotics began to be widely used. The earliest example can be traced back to the 1940s, when penicillin-resistant Staphylococcus aureus quickly emerged shortly after penicillin was introduced into clinical practice. Since then, with the invention and use of new antibiotics, various resistant strains have also continued to emerge. Due to the rapid development of bacterial resistance, existing antibiotics are no longer effective in treating infections in some cases. Although the development of new drugs is the key to addressing this problem, the development of new antibiotics has been slow in recent years, mainly due to the high cost and low return rate. Addressing the problem of bacterial resistance requires multidisciplinary collaboration. The initial application of plasma in the biomedical field was the sterilization of food and equipment. In 1996, Laroussi confirmed that atmospheric pressure glow discharge plasma has a strong inactivation effect on bacteria. Subsequently, plasma has been increasingly used in the biomedical field, especially cold plasma close to or slightly above room temperature, which will not cause obvious thermal damage to the human body and biological tissues, will not pollute the surrounding environment, and will not cause thermal deformation and damage to medical devices. It can effectively inactivate various bacteria, fungi, viruses and other pathogenic microorganisms, making up for the shortcomings of high-pressure steam sterilization, chemical and nuclear radiation methods. At present, plasma has achieved very good research results in sterilization, material surface modification, dental treatment, beauty, hemostasis and anti-inflammatory, wound healing, skin disease treatment and tumor treatment, and there are no signs of side effects or complications. Therefore, combining plasma with the field of clinical medicine can be used as an auxiliary surgery or to assist drugs in treating diseases.

[0003] As a common plasma discharge method, dielectric barrier discharge (DBD) discharge can generate stable plasma at room temperature and pressure. Because of its simple device structure and high energy utilization rate, it has become one of the most commonly used plasma production methods. The principle is to place one or more layers of insulating medium in the discharge space. The insulating medium can be suspended in the discharge space or covered on the electrode. Due to the presence of the medium, the DC current will be prevented from passing through. Therefore, the dielectric barrier discharge is usually driven by AC and pulse power supply. When the intensity of the alternating electric field applied to the positive and negative electrodes reaches the gas breakdown strength, the gas between the electrodes breaks down and a discharge channel is generated. Dielectric barrier discharge (DBD) has been widely used in applications and research in the fields of ozone synthesis, material surface modification, and environmental pollutant treatment. Dielectric barrier discharge (DBD) is the most commonly used method to generate low-temperature plasma, but direct body phase discharge (VDBD) plasma treatment of biological bodies may cause damage to the biological body. Surface dielectric barrier discharge (SDBD) is a simple, flexible, portable and scalable method for generating low-temperature plasma. It can evenly and effectively treat the wound surface and is very suitable for treating the surface of biological bodies.

[0004] SDBD electrodes can be designed as flexible electrode materials based on different substrate materials. The high-voltage metal electrodes and low-voltage metal electrodes are made bendable by printing and crimping, so as to match the skin surface processing capabilities of different complex parts of the human body. However, in the process of continuous promotion and application, the current flexible SDBD electrodes have application problems such as uneven discharge (especially under bending conditions), severe electrode heating, frequent breakdown during normal operation, and poor electrical safety in treating human skin. Summary of the invention

[0005] 1. Technical problems to be solved:

[0006] The current flexible SDBD electrodes have problems such as uneven discharge, especially under bending conditions, severe electrode heating, frequent breakdown during normal operation, and poor electrical safety in dealing with human skin.

[0007] 2. Technical solution:

[0008] In order to solve the above problems, the present invention provides an impedance-matching flexible SDBD electrode for skin surface treatment, comprising three electrodes, wherein a high-voltage electrode and a ground electrode are alternately arranged on the SDBD electrode layer, an air gap is left between the high-voltage electrode and the ground electrode, the high-voltage electrode is connected to the positive pulse high-voltage potential interface of the driving power supply, and the ground electrode is connected to the ground potential interface of the driving power supply. At the same time, the ground electrode wire wraps the high-voltage electrode wire and is in the same layer of the SDBD electrode, polyimide is first crimped on the surface of the high-voltage electrode and the ground electrode, and then a thin film material contactable by the human body is crimped on the polyimide, a regulating electrode is provided at the bottom layer of the SDBD electrode layer, and the regulating electrode is a whole layer of copper skin, which covers the area of ​​the plasma discharge area formed by the entire high and low voltage electrodes, and the regulating electrode and the ground electrode are connected to a matching impedance network.

[0009] Furthermore, a through hole is provided, and the through hole passes through the human body contactable thin film material and the SDBD electrode layer.

[0010] Furthermore, the through hole is located between electrode groups, and the edge of the through hole should have a certain distance from the electrode group, and the electrode group includes a plurality of high-voltage electrodes and a ground electrode.

[0011] Furthermore, the human body contactable film material is a polyurethane film.

[0012] Furthermore, the matching impedance network is a combination of one or more of a resistor R, a capacitor C, and an inductor L.

[0013] 3. Beneficial effects:

[0014] The present invention solves the problems of uneven discharge of flexible electrodes and breakdown during normal operation, especially in actual application, even under conditions where the flexible electrodes can be bent at will, uniform discharge can be ensured, while stable normal operation can be achieved, the electrode surface temperature is low, and electrical safety and reliability are achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the planar structure of the three-electrode flexible SDBD electrode.

[0016] Figure 2 It is a schematic diagram of the cross-sectional structure of the three-electrode flexible SDBD electrode.

[0017] Figure 3 It is a schematic diagram of the processing structure of thin film materials that can be contacted by the human body.

[0018] Figure 4 This is a physical picture of the flexible SDBD electrode.

[0019] Figure 5 This is a schematic diagram of the COMSOL electric field simulation results, where Figure 5a is the electric field distribution diagram corresponding to the control and electrode-ground electrode directly connected with a matching impedance of one megohm. Figure 5 b is the electric field distribution diagram corresponding to the control and the electrode-ground electrode is not connected to the matching impedance of one megohm. Figure 5 c is the electric field distribution diagram of the corresponding control and electrode-ground electrode directly connected with matching impedance of ten megohms. Figure 5 d is the electric field distribution diagram corresponding to the regulation and the electrode-ground electrode matching impedance is 10 megohms.

[0020] Figure 6 It is the COMSOL simulation curve.

[0021] Figure 7 This is the Saber simulation result diagram.

[0022] Figure 8 This is a comparison experiment diagram of the feasibility test of the impedance matching SDBD discharge state control. Figure 8 a is a schematic diagram of the electrode cross-section structure. Figure 8 b is the result diagram of electrode thermal breakdown. Figure 8 c is a photograph of electrode discharge.

[0023] Fig. 9 The test experiment diagram of the dual-medium structure flexible SDBD electrode in the flat state, where Fig. 9 a is a schematic diagram of the electrode structure section. Fig. 9 b is the electrode discharge photo, Fig. 9 c is the voltage and current waveform when the electrode discharges. Fig. 9 d is the electrode discharge thermal equilibrium temperature diagram, Fig. 9 e is the human body contact diagram.

[0024] Fig.10 The operating test experiment diagram of the dual-medium structure flexible SDBD electrode under the extreme bending state, where Fig.10 a is a photo of electrode discharge, Fig.10 b is the voltage and current waveform when the electrode discharges. Fig.10 c is the electrode discharge thermal equilibrium temperature diagram, Fig.10 d is the human body contact diagram. DETAILED DESCRIPTION

[0025] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0026] like Figure 1 and Figure 2 As shown, the present invention proposes a three-port flexible electrode structure, wherein the first port 1 is a high voltage electrode, the second port 2 is a ground electrode, and the third port 3 is a regulating electrode.

[0027] The high-voltage electrode is connected to the positive pulse high-voltage potential interface of the driving power supply, and port 2 is connected to the ground potential interface of the driving power supply. At the same time, the ground electrode line wraps the high-voltage electrode line and is in the same layer as the SDBD electrode, with a layer of polyimide dielectric material glued on the surface. Then, a thin film material that can be touched by the human body is crimped on the polyimide.

[0028] In one embodiment, the human body contactable film material is a polyurethane (PU) film.

[0029] Medical human-contactable films are mainly polyethylene (PE) films and polyurethane (PU) films. In the industrial processing of flexible SDBD electrodes, the flexible SDBD electrodes are formed by crimping copper electrode lines on polyimide films, and then crimping the required films. The crimping process adopts a hot crimping process, and the temperature of the hot crimping furnace is 180°C (for polyimide film substrates). If the temperature in the furnace is lowered, the crimping will not be tight and the film will fall off easily. However, the melting point of PE material is 100°C-130°C, and the melting point of PU material is between 100°C-200°C, depending on the manufacturer's doping of PU material films. Therefore, PE materials cannot realize the processing of flexible electrodes, so only PU films can be selected to process human-contactable electrode materials.

[0030] A PU film is applied to the electrode separately, because the medical PU film has high air permeability, good elasticity and high lightness. The material is breathable and water-permeable, and the molecular spacing is large. It is easy to arc and break down under high-voltage pulse driving conditions, and it will also have an adverse effect on the contactability of the human body. The internal high-voltage electrode will directly discharge directly to the human body through the molecular gap of the material, and the electrical safety cannot be guaranteed. Therefore, it is necessary to adopt a structural design of dual-medium surface materials, such as Figure 3 and Figure 4 As shown, the design of the dual dielectric material will not affect the discharge process and can also ensure that the SDBD electrode is in direct contact with the skin surface.

[0031] A specific air gap length d (d>=1mm) is left between the two electrodes. Driven by the pulse voltage electric field, the air at the air gap position undergoes air gas breakdown, generating discharge plasma, which adheres to the air gap interval and contacts the target skin to achieve skin surface treatment.

[0032] In one embodiment, between a pair of high-voltage electrodes and a ground electrode, the ground electrode is designed to surround the entire high-voltage electrode, thereby ensuring that the electric field forms a complete electric field closed curve between the high voltage and the nearest wrapped ground electrode, and will not form an electric field superposition effect on the discharge interval of adjacent groups and affect the discharge state of other groups, thereby solving the problem of discharge consistency and uniformity between different electrode groups.

[0033] In one embodiment, the regulating electrode is a whole layer of copper sheet, which is located at the bottom layer of the SDBD electrode, and its area covers the plasma discharge area formed by the entire high and low voltage electrodes to achieve the function of uniform electric field. Due to the flexible thin sheet shape of the flexible electrode, discharge resonance will occur during the discharge process. This resonance will cause mechanical vibration of the thin sheet electrode, resulting in a lot of noise during the operation of the whole device, affecting the user experience during use. The regulating electrode is a whole piece of copper sheet. Under the condition that the flexible state of the SDBD electrode sheet is not affected, the weight of the electrode sheet is increased, so that the electrical resonance noise of the discharge of the entire SDBD electrode sheet is not easy to resonate mechanically with the electrode sheet during the discharge process, which greatly reduces the discharge noise problem caused by mechanical resonance, and can further promote the industrial application of flexible electrode plasma source whole device.

[0034] In one embodiment, the electrical connection interfaces of the three-electrode flexible SDBD electrodes are designed on the same surface, and the ground electrode and the control electrode can be directly connected to the matching impedance network Z according to the driving pulse power form, the discharge intensity requirement, and the bending degree of the flexible SDBD electrode under actual application conditions. The matching impedance network Z can be a resistor R, a capacitor C, an inductor L, or any circuit combination unit.

[0035] In order to improve the safety of the flexible SDBD electrode, the present invention connects a suitable impedance network between the ground electrode and the control electrode to improve the safety and service life of the flexible electrode. If the ground electrode and the control electrode are directly connected, the equivalent capacitance of the entire electrode will be increased, the discharge power of the entire electrode will be increased, and the electric field will be stronger near high voltage; if the ground electrode and the control electrode are not connected to anything, when the electrode is driven by a power supply, induced charges will be generated on the copper of the control electrode. When running for a long time, a large amount of charge will accumulate on the metal copper. During use, the copper of the control electrode may discharge with the low potential, thereby damaging the electrode and even endangering the safety of the user. Through COMSOL software simulation, we can see the effect of matching impedance on the entire counter electrode electric field. Figure 5 As shown, Figure 5 a. Figure 5 b、Figure c、 Figure 5 d respectively correspond to four situations: the control and electrode ground electrodes are directly connected, not connected, the matching impedance is one megohm, and the matching impedance is ten megohms.

[0036] In one embodiment, a through hole is designed between the impedance-matching flexible SDBD electrode groups, running through the entire flexible SDBD electrode, to solve the problem that the ozone concentration generated by the flexible SDBD electrode during therapeutic applications is too high, exceeds the national medical equipment standards, and cannot be realized in product design and application. The through hole is designed to be located between the electrode groups, and the size of the through hole does not need to be specifically designed, and will not affect the discharge.

[0037] In one embodiment, the edge of the through hole must be at a certain distance from the electrode group, and the through hole cannot be opened directly to the edge of the electrode group. The radius of the electrode through hole of the present invention is 0.6 mm, and the distance between the center of the through hole and the low-voltage electrode of the electrode group is 1.6 mm.

[0038] In the COMSOL software simulation, the electrodes were selected as Figure 6 For the ten points shown in a, draw their electric field change curves and draw the corresponding point-line graphs, such as Figure 6 The addition of impedance between the control electrode and the ground electrode can change the surface electric field distribution of the electrode. Impedances of 10 megohms and 1 megohm can improve the uniformity of the local electric field between the electrodes, allowing the entire electrode to produce a more uniform discharge.

[0039] From the simulation curve results, it can be seen that when the control electrode and the ground electrode are directly connected, the electric field strength is obviously higher than that in the other three cases. In the cases of no grounding, one megohm resistor, and ten megohm resistor, the field strength is different only in some areas. Figure 6 c and Figure 6 As shown in Figure 5, this is because different matching impedances can affect the field strength of the local area of ​​the electrode. In actual use, the addition of matching impedance can make the local electric field on the electrode surface more uniform, avoiding excessive local field strength during normal operation, causing severe heat generation and thermal breakdown of the local area of ​​the electrode, and damaging the electrode. By using Saber to simulate the voltage changes between the local areas of the electrode under different impedance conditions, such as Figure 7 As shown. Through the simulation results of Saber, we can see that under different impedance conditions, the Ua voltage will be different. , under different impedance conditions, the local field strength between electrodes is also different.

[0040] For the designed electrodes, we conducted the following experiments to test the electrodes to simulate their actual working conditions. For the medical human-contactable material processing structure mentioned above, we made a single-dielectric SDBD electrode with polyimide as the impedance medium. The ground electrode and the control electrode were directly connected, and a matching impedance (10 megohms) was connected between the ground electrode and the control electrode. Experiments were conducted for comparison. The experimental results show that under the same power input conditions, direct connection between the ground electrode and the control electrode will make the flexible electrode unable to maintain long-term stable operation and may burn through the electrode. The addition of matching impedance allows the flexible electrode to achieve the required performance well.

[0041] The flexible SDBD with a single-layer dielectric structure can well meet our requirements for the normal operation of the flexible electrode under the action of matching impedance. The reduction of the dielectric layer can effectively reduce the thickness of the electrode. Moreover, because of the lack of a layer of dielectric, the capacitance of the entire electrode will become smaller. The reduction of the equivalent capacitance can reduce the power required for the electrode discharge. However, the breakdown field strength of different insulating media is also different. The experimental results are as follows: Figure 8 Figure a shows the results of the single-layer medical PU material dielectric experiment. A medical PU film is applied separately on the metal electrode. Although the medical PU material has a certain insulation strength, a very high voltage must be applied to enable the electrode to discharge (under the microsecond power supply conditions used in this experiment, it needs to reach about 5kV). However, because the material of the medical PU film is breathable and water-permeable, and the molecular spacing is large, it is easy to arc and break down under high-voltage pulse driving conditions, and it will also have an adverse effect on the human body's accessibility. The internal high-voltage electrode will directly pass through the molecular gap of the material and discharge directly to the human body, and the electrical safety cannot be guaranteed. The flexible electrode using polyimide as a single-layer dielectric can discharge the electrode well under the same power supply conditions because the insulation strength of polyimide is very high. Figure 8 As shown in b, if a flexible electrode with a single-layer dielectric structure is required, the choice of the dielectric layer is very important.

[0042] In order to meet our requirements for performance and application scenarios, a dual-medium structure is used to design flexible electrodes. Fig. 9 As shown in a, the normal stable operation test was carried out, and a 700W high-power microsecond power pulse power supply was used to drive it. The input voltage was 15V, the pulse frequency was 1kHz, the electrode equivalent electrode capacitance was 291pF (measured by the bridge at a frequency of 100Hz), and the matching impedance was 10 megohms. The discharge luminescence photos and electrical waveforms were shown in Fig. 9 b and 9c. It can be seen that the peak discharge voltage is about 5kV and the peak discharge current is 100mA. After a ten-minute normal stability test, the highest electrode surface temperature was measured to be about 42 degrees. Fig. 9 d, and there is no discomfort when touching the electrodes with hands. Fig. 9 As shown in e.

[0043] Flexible electrodes often need to work in a bent state. We simulated the bent state and subjected the electrode to extreme bending. Given the same microsecond pulse drive parameters, the characteristic test results are as follows: Fig.10As shown. It can be seen that high curvature bending does strengthen the discharge, and the pulse amplitude voltage remains unchanged at about 5kV, but the discharge current filaments increase significantly and the thermal equilibrium temperature also increases. The experiment was run normally for 10 minutes, and the highest hot spot temperature reaching the final thermal equilibrium was about 60℃. The human body can touch it normally, and there is no abnormality in the operation of the electrode.

Claims

1. An impedance matching flexible SDBD electrode for skin surface treatment, comprising three electrodes, characterized in that: The high-voltage electrode and the ground electrode are arranged alternately on the SDBD electrode layer, with an air gap between the high-voltage electrode and the ground electrode. The high-voltage electrode is connected to the positive pulse high-voltage potential interface of the driving power supply, and the ground electrode is connected to the ground potential interface of the driving power supply. At the same time, the ground electrode wraps the high-voltage electrode and is located in the SDBD electrode layer. Polyimide is first crimped on the surface of the high-voltage electrode and the ground electrode, and then a thin film material that can be contacted by the human body is crimped on the polyimide. A control electrode is provided at the bottom layer of the SDBD electrode layer. The control electrode is a whole layer of copper skin, and the copper skin area wraps the entire plasma discharge area formed by the high-voltage electrode and the ground electrode. The control electrode and the ground electrode are connected to a matching impedance network.

2. The impedance matching flexible SDBD electrode for skin surface treatment as claimed in claim 1, characterized in that: A through hole is also provided, and the through hole passes through the human body contactable thin film material and the SDBD electrode layer.

3. The impedance matching flexible SDBD electrode for skin surface treatment as claimed in claim 2, characterized in that: The through hole is located between electrode groups, and the edge of the through hole should be at a certain distance from the electrode group. The electrode group includes a plurality of high-voltage electrodes and a ground electrode.

4. The impedance matching flexible SDBD electrode for skin surface treatment as claimed in claim 1, characterized in that: The human body contactable film material is a polyurethane film.

5. The impedance matching flexible SDBD electrode for skin surface treatment as claimed in claim 1, characterized in that: The matching impedance network is a combination of one or more of a resistor R, a capacitor C, and an inductor L.

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