Non-invasive plasma surface modification apparatus and method

Abstract

The application discloses a non-invasive plasma surface modification device and method, which comprises a high-voltage electrode, a direct-current pulse voltage electrode and a porous electrode; an alternating current voltage or a pulse voltage is applied between the high-voltage electrode and the porous electrode to generate plasma, and electrons, ions and free radicals in the plasma can pass through the porous electrode; a pulse electric field is applied between the direct-current pulse voltage electrode and the porous electrode and is directed to the porous electrode, in a pulse duration, electrons are bombarded to a sample to be treated under the action of the electric field, excitation states and / or un-bonded particles are formed on the surface of the sample, in a pulse gap time, a reverse electric field directed to the sample is formed between the electrons adsorbed on the surface of the sample and the porous electrode, ions and / or free radicals move to the surface of the sample, and bond with the excitation states and / or un-bonded particles on the surface of the sample, so that physical etching damage to the surface of the sample is avoided when a grafting forming group is formed.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of plasma surface modification, in particular to a non-damaging plasma surface modification device and method. BACKGROUND

[0002] Plasma surface modification is a technology that uses active particles such as ultraviolet light, high-energy electrons, excited-state particles, ions, and free radicals in plasma to change the physical or chemical properties of the material surface. It can change the types and quantities of functional groups on the material surface, adjust the surface energy, and thus impart variable wettability, adhesion, antibacterial properties, and other properties to the material. Polymer materials have wide applications in biomedical, composite materials, and other fields due to their excellent processability and use performance. However, the surface energy of polymer materials is usually low, which limits their applications in printing, coating, and adhesion. Therefore, plasma surface modification can activate the surface of polymer materials without affecting the bulk properties of the materials, and impart the desired surface properties.

[0003] Through different working gases, plasma surface modification can achieve different types of surface changes of polymer materials. For example, using oxygen or air as the gas source can introduce carboxyl, hydroxyl, aldehyde, ketone, and other oxygen-containing functional groups on the surface of polymer materials; using nitrogen or ammonia as the gas source can introduce amino, amide, imine, and other nitrogen-containing functional groups on the surface of polymer materials; using inert gases such as argon or helium as the gas source can generate free radicals or cross-linking reactions on the surface of polymer materials. These different types of functional groups can provide different chemical reaction sites or biological recognition sites, thereby achieving the functionalization of the surface of polymer materials. CN115332036A discloses a plasma surface modification device and method based on ion implantation, which generates ions in the plasma generation zone by applying a direct current pulse negative voltage to the lower electrode, and the ions accelerate towards the lower electrode under the action of the electric field to achieve ion implantation on the treated material. In the usual plasma surface modification process, a thin plasma sheath layer is formed at the interface between the plasma and the material. Due to the much higher electron mobility than ions, a strong electric field is formed inside the sheath layer pointing towards the treated material. The ions in the plasma repeatedly bombard the treated material under the action of the strong electric field, causing physical damage to the surface of the polymer material, such as roughening, crack formation, delamination, and other effects. These damages can reduce the mechanical strength and durability of the polymer material, and may affect its function in specific applications.

[0004] In summary, the plasma surface activation modification is an effective method, which can improve the surface function of the polymer material without affecting the bulk characteristics of the polymer material. However, the plasma surface modification will also cause physical etching damage to the surface of the polymer material, and affect the mechanical strength and durability. At present, there is no method for realizing the plasma surface modification without avoiding the physical etching damage to the surface of the material. SUMMARY

[0005] In order to solve the problem of physical damage to the surface of the polymer material caused by the plasma surface activation modification, the application provides a non-damage plasma surface modification device and method.

[0006] The technical problem of the application is solved by the following technical scheme:

[0007] A non-damage plasma surface modification device comprises a high-voltage electrode, a direct-current pulse voltage electrode and a porous ground electrode between the high-voltage electrode and the direct-current pulse voltage electrode; wherein an alternating current voltage or a pulse voltage is applied between the high-voltage electrode and the porous ground electrode to generate plasma, and the electrons, ions and free radicals in the plasma can pass through the porous ground electrode; wherein a pulse electric field directed to the porous ground electrode is applied between the direct-current pulse voltage electrode and the porous ground electrode, and during the pulse duration, the electrons are bombarded to the sample to be processed under the action of the electric field, and the excited state and / or unbound particles are formed on the surface of the sample, while during the pulse gap time, a reverse electric field directed to the sample is formed between the electrons adsorbed on the surface of the sample and the porous ground electrode, and the ions and / or free radicals move to the surface of the sample and bond with the excited state or / and unbound particles on the surface of the sample to form a group.

[0008] In some embodiments, the duty cycle of the direct-current pulse voltage is preferably 50% or less.

[0009] In some embodiments, the amplitude of the direct-current pulse voltage is preferably 10V or more.

[0010] In some embodiments, the frequency of the direct-current pulse voltage is preferably 1000Hz or more.

[0011] In some embodiments, the processing time of the direct-current pulse voltage is preferably 10s or more.

[0012] In some embodiments, one side of the high-voltage electrode and the direct-current pulse voltage electrode towards the porous ground electrode is respectively provided with a dielectric barrier material.

[0013] In some embodiments, the sample to be processed is a non-metallic material containing covalent bond such as polymer material.

[0014] The application also provides a non-invasive plasma surface modification method using the device, comprising the following steps:

[0015] S1, applying an alternating voltage or a pulse voltage between the high-voltage electrode and the porous electrode to generate plasma, and the electrons, ions and radicals in the plasma can pass through the porous electrode;

[0016] S2, applying a pulse electric field directed to the porous electrode between the direct current pulse voltage electrode and the porous electrode, and during the pulse duration, the electrons are bombarded to the sample to be processed under the action of the electric field, and the excited state and / or unbound particles are formed on the surface of the sample, and during the pulse gap time, a reverse electric field directed to the sample is formed between the electrons adsorbed on the surface of the sample and the porous electrode, and the ions and / or radicals move to the surface of the sample, bond with the excited state and / or unbound particles on the surface of the sample, and form groups by grafting.

[0017] In some embodiments, different gas components and proportions for generating plasma are selected as required.

[0018] In some embodiments, the duty cycle, amplitude, frequency and processing time of the direct current pulse voltage are selected as required.

[0019] The beneficial effects of the application compared with the prior art include:

[0020] The plasma surface modification device provided by the application applies a periodic pulse electric field directed to the porous electrode between the direct current pulse voltage electrode and the porous electrode when the electrons, ions and radicals in the plasma pass through the porous electrode, and during the pulse duration, the electrons are bombarded to the sample to be processed under the action of the electric field, and the excited state and / or unbound particles are formed on the surface of the sample, and during the pulse gap time, a reverse electric field directed to the sample is formed between the electrons adsorbed on the surface of the sample and the porous electrode, and the ions and / or radicals move to the surface of the sample, bond with the excited state and / or unbound particles on the surface of the sample, and form groups by grafting, thereby achieving a grafting effect and realizing a phased surface modification effect of pre-activation of high-energy electrons and post-bonding of ions / radicals on the surface of the sample. Thus, the application effectively avoids the problem of physical etching of the sample surface by high-energy ions in the sheath layer formed when the plasma directly contacts the sample in the method of the prior art, and realizes a non-invasive plasma surface modification effect. Since no physical etching damage is caused to the surface of the sample material, the mechanical strength and durability of the sample material are improved. The application can be applied in all technical fields requiring modification of the surface of a material, and the focus can be on high polymer materials.

[0021] Other beneficial effects of the embodiments of the application will be further described below. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of a damage-free plasma surface modification device in an embodiment of the present invention;

[0023] The reference numerals are as follows:

[0024] 1-high-frequency high-voltage electrode, 2-mesh ground electrode, 3-DC pulse voltage electrode, 4-sample to be processed, 5-AC dielectric barrier material, 6-DC dielectric barrier material, 7-plasma, 8-high-frequency AC voltage, 9-DC pulse voltage. DETAILED DESCRIPTION

[0025] The present invention will be further described below with reference to the accompanying drawings and in combination with preferred embodiments. It should be noted that, unless there is a conflict, the embodiments and features in the embodiments of the present application can be combined with each other.

[0026] It should be noted that the directional terms such as left, right, up, down, top, and bottom in this embodiment are merely relative concepts, or are based on the normal use status of the product, and should not be considered as restrictive.

[0027] Plasma surface activation modification is an effective method for improving the surface functionality of polymer materials without affecting their inherent properties. However, existing plasma surface activation modification methods result in the formation of a plasma sheath on the sample surface during direct plasma contact with the sample. The high-energy ions in the sheath physically etch the sample surface, causing physical damage to the polymer sample, affecting its mechanical strength and durability. Currently, there are no methods for plasma surface modification that can avoid physical etching damage to the material surface.

[0028] To solve the above problems, the present invention proposes a device for achieving damage-free plasma surface modification in stages based on high-energy electron activation and ion / radical bonding, such as Figure 1 As shown, the plasma surface modification device includes a high-voltage electrode, a DC pulse voltage electrode 3, and a porous ground electrode located between the high-voltage electrode and the DC pulse voltage electrode. An AC voltage or a pulse voltage is applied between the high-voltage electrode and the porous ground electrode to generate plasma. In one embodiment, the high-voltage electrode is a high-frequency AC high-voltage electrode 1, and the porous ground electrode is a mesh ground electrode 2. A high-frequency AC voltage 8 is applied between the high-frequency AC high-voltage electrode 1 and the mesh ground electrode 2 to generate plasma 7. A DC pulse voltage 9 is applied between the mesh ground electrode 2 and the DC pulse voltage electrode 3, directed toward the mesh ground electrode 2, forming a strong pulsed electric field between the mesh ground electrode 2 and the DC pulse voltage electrode 3.

[0029] The duty cycle of the direct current pulse voltage 9 is preferably 50% or less, the amplitude is preferably 50V or more, the frequency is preferably 1000Hz or more, and the processing time is preferably 10s or more; the high-frequency alternating current high-voltage electrode 1 is provided with an alternating current dielectric barrier material 5 on the side facing the mesh electrode 2, and the direct current pulse voltage electrode 3 is provided with a direct current dielectric barrier material 6 on the side facing the mesh electrode 2.

[0030] The non-invasive plasma surface modification principle proposed in the embodiment of the application is described as follows:

[0031] The non-invasive plasma surface modification method includes two stages of high-energy electron activation and ion / free radical bonding. In the high-energy electron activation stage, the covalent bonds on the surface of the treated object are broken by high-energy electrons to generate un-bonded active atoms or molecules; in the ion / free radical bonding stage, the un-bonded electrons in the ions or free radicals recombine with the un-bonded atoms or molecules on the surface of the treated object material to form new groups.

[0032] Specifically, under the action of bipolar diffusion, the electrons and ions or free radicals in the plasma 7 generated between the high-frequency alternating current high-voltage electrode 1 and the mesh electrode 2 can pass through the mesh electrode 2.

[0033] During the pulse duration of the direct current pulse voltage, an electric field strength directed towards the mesh electrode 2 is formed between the mesh electrode 2 and the direct current pulse voltage electrode 3, and positive ions will rebound back to the plasma generation area under the action of the electric field, while electrons will be bombarded towards the treated sample 4 under the action of the strong pulse electric field. In the embodiment of the application, the treated sample 4 is a high polymer material. The high-energy electrons break the covalent bonds on the surface of the treated sample 4 to form un-bonded molecules and atoms.

[0034] During the pulse gap time in the same cycle of the direct current pulse voltage, the external electric field strength between the mesh electrode 2 and the direct current pulse voltage electrode 3 is zero. Since part of the high-energy electrons are adsorbed on the surface of the treated sample 4, a low potential is formed on the surface of the treated sample 4, and an electric field strength directed towards the treated sample 4 is formed between the low potential and the mesh electrode 2 (the electric field direction is opposite to that in the previous stage). The ions or free radicals that pass through the mesh electrode 2 will move towards the treated sample 4 under the action of the electric field strength directed towards the treated sample 4, and bond with the treated sample 4.

[0035] When the ions or radicals are adsorbed on the surface of the sample 4 to be treated, the un-bonded particles will form new un-bonded radicals under the bombardment of the high-energy electrons in the next cycle pulse duration, and the radicals will continue to bond with the un-bonded molecular atoms on the surface of the sample 4 to be treated to graft new groups. The plasma surface modification avoids the physical etching of the high-energy ions in the sheath layer to the surface of the sample 4 to be treated in the process of directly contacting the plasma 7 with the sample 4 to be treated, and realizes the non-damage plasma surface modification effect.

[0036] The embodiment of the present application also proposes a non-damage plasma surface modification method, which is specifically described as follows:

[0037] The embodiment adopts the AC plasma surface modification device proposed in the foregoing embodiments of the present application, as shown in the figure. Figure 1 The dielectric barrier material 5 and the direct current dielectric barrier material 6 adopt organic glass, and a mesh-shaped electrode 2 containing an insulating dielectric barrier is arranged between the high-frequency AC high-voltage electrode 1 and the direct current pulse voltage electrode 3. The high-frequency AC high-voltage electrode 1 is connected to the high-frequency AC voltage 8, the mesh-shaped electrode 2 is connected to the ground, and the direct current pulse voltage electrode 3 is connected to the direct current pulse voltage 9. The electrode structure is placed in a sealed discharge cavity, a specific working gas is introduced, and the pressure is extracted.

[0038] S1, the high-frequency AC voltage 8 is applied between the high-frequency AC high-voltage electrode 1 and the mesh-shaped electrode 2, and the plasma 7 is generated. The charged particles in the plasma 7 will diffuse between the mesh-shaped electrode 2 and the direct current pulse voltage electrode 3 under the principle of bipolar diffusion, wherein the charged particles include electrons, ions and radicals.

[0039] S2, the direct current pulse voltage 9 is applied between the mesh-shaped electrode 2 and the direct current pulse voltage electrode 3. In the pulse duration, the electrons will accelerate to the direct current pulse voltage electrode 3 under the action of the strong electric field, and the positive ions will rebound back to the plasma 7 generation area under the action of the electric field.

[0040] In the pulse duration, the high-energy electrons can realize the activation of the sample 4 to be treated, and generate un-bonded molecules and atoms.

[0041] In the pulse gap time of the same cycle, the low potential formed by the accumulated electrons on the surface of the sample 4 to be treated will promote the ions and radicals to move to the surface of the sample 4 to be treated, and bond with the excited state and / or un-bonded particles on the surface of the sample 4 to be treated.

[0042] And the unbound particles will be reactivated by high-energy electrons during the next cycle pulse, and bond with the excited state and / or unbound particles on the surface of the sample 4 to be treated, and form groups by grafting, wherein the unbound particles include unbound molecules or atoms. The formation of the traditional plasma surface modification sheath is avoided, and the non-damaging plasma surface modification effect can be achieved. The plasma composition and the direct current pulse cycle and frequency can be controlled according to actual needs.

[0043] In different embodiments, the method for generating high-energy electrons includes plasma or electron gun, and the specific method for generating high-energy electrons is not limited, and the type of working gas required for ion / free radical generation is not limited, and different gas components and proportions can be selected according to needs. The migration method of ion / free radical is not limited. Specifically, high-energy electrons can be generated by an electron gun to bombard the object to be treated, instead of the method of generating electrons by plasma and accelerated by a pulse electric field. As long as the method is based on the activation of high-energy electrons in the early stage, and the ion / free radical bonding is implemented in stages to achieve the surface modification effect in the later stage, it is within the scope of the present application.

[0044] Compared with the prior art, the plasma surface modification device proposed in the present application applies a periodic pulse electric field directed to the porous ground electrode between the direct current pulse voltage electrode and the porous ground electrode when the electrons, ions and free radicals in the plasma pass through the porous ground electrode; during the pulse duration, the electrons are bombarded to the sample to be treated under the action of the electric field, and the excited state and / or unbound particles are formed on the surface of the sample; during the pulse gap time, the electrons adsorbed on the surface of the sample form a reverse electric field directed to the sample between the sample and the porous ground electrode, and the ions and / or free radicals move to the surface of the sample and bond with the excited state and / or unbound particles on the surface of the sample to form groups by grafting, thereby achieving a staged surface modification effect of activating high-energy electrons in the early stage and bonding ions / free radicals in the later stage on the surface of the sample. Thus, the present application effectively avoids the problem that the high-energy ions in the sheath layer formed when the plasma directly contacts the sample to be treated in the method of the prior art physically etch the surface of the sample to be treated, and achieves a non-damaging plasma surface modification effect. Since the sample material surface will not be physically etched and damaged, the mechanical strength and durability of the sample material can be improved. The non-damaging plasma surface modification method proposed in the embodiments of the present application can be applied in all technical fields requiring surface modification of materials, especially in the surface modification of high polymer materials.

[0045] The above further describes the present application in conjunction with specific / preferred embodiments, and cannot be deemed to limit the specific implementation of the present application to these descriptions. For those skilled in the art to which the present application belongs, without departing from the concept of the present application, they can make several substitutions or variations to the described embodiments, and these substitutions or variations shall be deemed to fall within the protection scope of the present application. In the description of the present application, the description of the terms "an embodiment", "some embodiments", "a preferred embodiment", "an example", "a specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are contained in at least one embodiment or example of the present application. In the present application, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In the case of no mutual contradiction, those skilled in the art can combine and combine the different embodiments or examples described in the present application and the features of the different embodiments or examples. Although the embodiments of the present application and their advantages have been described in detail, it should be understood that various changes, substitutions and modifications can be made herein without departing from the scope of protection of the patent application.

Claims

1. A non-destructive plasma surface modification device, characterized in that: It comprises a high-voltage electrode, a DC pulse voltage electrode and a porous ground electrode located between the high-voltage electrode and the DC pulse voltage electrode; wherein, an AC voltage or a pulse voltage is applied between the high-voltage electrode and the porous ground electrode to generate plasma, and the electrons, ions and free radicals in the plasma can pass through the porous ground electrode; wherein, a pulse electric field directed toward the porous ground electrode is applied between the DC pulse voltage electrode and the porous ground electrode, during the pulse duration, the electrons bombard the sample to be processed under the action of the electric field, forming excited states and / or unbonded particles on the sample surface, and during the pulse interval, a reverse electric field directed toward the sample is formed between the electrons adsorbed on the sample surface and the porous ground electrode, and the ions and / or free radicals move to the sample surface, bond with the excited states and / or unbonded particles on the sample surface, and graft to form groups.

2. The damage-free plasma surface modification device according to claim 1, characterized in that: The duty cycle of the DC pulse voltage is less than 50%.

3. The damage-free plasma surface modification device according to claim 1, wherein: The amplitude of the DC pulse voltage is greater than 10V.

4. The damage-free plasma surface modification device according to claim 1, wherein: The frequency of the DC pulse voltage is above 1000 Hz.

5. The damage-free plasma surface modification device according to claim 1, wherein: The treatment time of the DC pulse voltage is more than 10s.

6. The damage-free plasma surface modification device according to any one of claims 1 to 5, characterized in that: The high voltage electrode and the DC pulse voltage electrode are respectively provided with dielectric barrier materials on one side facing the porous ground electrode.

7. The damage-free plasma surface modification device according to any one of claims 1 to 5, characterized in that: The sample to be processed is a non-metallic material containing covalent bonds, such as a polymer material.

8. A non-destructive plasma surface modification method using the apparatus according to any one of claims 1 to 7, characterized in that: The steps include: S1. Applying an AC voltage or a pulse voltage between the high-voltage electrode and the porous ground electrode to generate plasma, wherein electrons, ions, and free radicals in the plasma can pass through the porous ground electrode; S2. A pulse electric field pointing to the porous ground electrode is applied between the DC pulse voltage electrode and the porous ground electrode. During the pulse duration, the electrons bombard the sample to be processed under the action of the electric field, forming excited states and / or unbonded particles on the sample surface. During the pulse interval, a reverse electric field pointing to the sample is formed between the electrons adsorbed on the sample surface and the porous ground electrode. The ions and / or free radicals move to the sample surface, bond with the excited states and / or unbonded particles on the sample surface, and graft to form groups.

9. The method for non-destructive plasma surface modification of the device according to claim 8, characterized in that: Different gas components and proportions for generating plasma are selected according to needs.

10. The damage-free plasma surface modification method of the device according to claim 8 or 9, characterized in that: The duty cycle, amplitude, frequency and processing time of the DC pulse voltage are selected as needed.

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