Medical electromagnetic shielding composite material and preparation method thereof

Abstract

The invention provides a medical electromagnetic shielding composite material and a preparation method thereof, and belongs to the technical field of functional composites.The electromagnetic shielding composite material comprises an MXene / kapok pulp mixed layer; the surface of one side of the MXene / kapok pulp mixed layer is coated with a graphene oxide coating, and the surface of the other side of the MXene / kapok pulp mixed layer is provided with a PAN nanofiber membrane; the MXene / kapok pulp mixed layer comprises a modified kapok pulp layer and MXene randomly distributed in the modified kapok pulp layer in a three-dimensional manner. According to the composite material, through the structural design, electromagnetic shielding leading to absorption is achieved, and secondary pollution is effectively avoided. The air permeability and moisture permeability of the kapok fibers improve the medical comfort level. The GO protective layer obviously enhances the environmental stability of MXene. The material integrates efficient and stable electromagnetic shielding, biocompatibility and use comfort, and has wide application prospects in the fields of wearable medical equipment, electromagnetic shielding dressings and the like.

Description

Technical Field

[0001] This invention relates to a medical electromagnetic shielding composite material and its preparation method, belonging to the field of electromagnetic shielding composite material preparation technology. Background Technology

[0002] With societal development, the number of electronic products used in the medical field is increasing, posing a potential threat to the normal operation of medical equipment. Many sophisticated medical devices, such as electrocardiographs, electroencephalograms, MRI systems, and various monitoring instruments, are highly susceptible to electromagnetic interference, leading to misdiagnosis or treatment errors. Electromagnetic interference not only affects the performance of medical equipment but may also pose potential risks to patients' health. Therefore, developing efficient electromagnetic shielding materials to ensure the stable and reliable operation of medical equipment in complex electromagnetic environments, and to protect the physical and mental health of medical personnel and patients, has become an important research direction. Traditional electromagnetic shielding materials mainly use metallic materials, such as copper, aluminum, and steel. These materials have excellent conductivity and electromagnetic shielding effectiveness, but they also have some significant drawbacks, such as high density, difficulty in processing, susceptibility to corrosion, and poor comfort, limiting their application in the medical field. In addition, the processing of metallic materials is complex and costly, and in certain special medical environments, the chemical stability of metallic materials may not meet the requirements for long-term use. In recent years, with the rapid development of materials science and nanotechnology, various novel electromagnetic shielding composite materials have emerged, providing new ideas for solving the above problems. These new materials mainly include conductive polymer composites, carbon-based composites, and MXene-based composites. They have attracted widespread attention due to their advantages such as lightweight, high flexibility, ease of processing, and environmental friendliness.

[0003] Conductive polymers (CPs), such as polyaniline (PAni), polypyrrole (PPy), and polythiophene, are often combined with various fillers to improve their mechanical strength, processability, and electromagnetic shielding effectiveness due to their ability to be synthesized chemically or electrochemically, their good conductivity, and environmental stability. Carbon-based materials, such as carbon nanotubes (CNTs), graphene, and carbon fibers (CFs), possess excellent conductivity, are lightweight, and have a high specific surface area, making them ideal for preparing highly efficient electromagnetic shielding materials. Combining carbon materials with a polymer matrix can fully leverage the advantages of carbon materials while improving the mechanical and processability properties of the polymer. MXenes, a class of novel two-dimensional transition metal carbides or nitrides, exhibit excellent conductivity, a large specific surface area, and tunable surface chemistry, showing great application potential in the field of electromagnetic shielding.

[0004] Patent application CN116903989A discloses an electromagnetic shielding carbon fiber composite material, its preparation process, and a shell for medical devices. Phosphorus graphite powder or graphene powder is diluted with anhydrous ethanol or acetone aqueous solution and then sprayed onto the surface of carbon fiber filaments. Multiple surface treatments of the carbon fiber filaments improve the electromagnetic shielding effect and the production efficiency of the carbon fiber composite material. Patent application CN119730212 discloses an MXene-based electromagnetic shielding composite material. Both of these methods have high preparation costs, complex processes, and poor dispersibility.

[0005] Based on existing technologies, the development of materials that also provide highly efficient electromagnetic shielding still faces the following main drawbacks and challenges: 1. In medical applications, the overall performance of conductive polymers such as polyaniline and polypyrrole is insufficient to meet requirements. Their intrinsic conductivity is low, often necessitating large filler volumes or thicknesses to achieve effective shielding performance (SE), which contradicts the thinness and flexibility required for medical devices or dressings. More importantly, these materials exhibit poor mechanical properties, such as brittleness and environmental stability under varying humidity and temperature conditions. In medical environments involving prolonged contact with bodily fluids or repeated sterilization, their shielding performance is prone to degradation, resulting in insufficient reliability and durability, posing potential safety risks.

[0006] 2. The main obstacles to the medical application of carbon-based materials lie in their inherent shielding mechanisms and processing difficulties. Graphene or carbon nanotubes are prone to agglomeration in polymer matrices, leading to uneven conductive networks. This not only limits shielding effectiveness but also makes their shielding mechanism primarily based on electromagnetic wave reflection. This strong electromagnetic reflection can cause secondary electromagnetic pollution in medical spaces where sophisticated electronic equipment is used intensively, interfering with the normal operation of other sensitive medical instruments. This is something that medical electromagnetic compatibility (EMC) requirements strive to avoid.

[0007] 3. MXene is extremely sensitive to moisture and oxygen, and it will rapidly oxidize and degrade in humid environments, leading to a permanent loss of shielding effectiveness. Medical environments such as wound dressings and surgical gowns inevitably come into contact with moisture, bodily fluids, or require steam sterilization, which makes it impossible to guarantee the long-term service stability of pure MXene materials, greatly increasing the risks of medical applications. Summary of the Invention

[0008] To address the aforementioned technical problems, this invention provides a medical electromagnetic shielding composite material and its preparation method.

[0009] To solve the above-mentioned technical problems, the objective of this invention is achieved as follows: The present invention relates to a medical electromagnetic shielding composite material, comprising an MXene / kapok pulp mixed layer; one side surface of the MXene / kapok pulp mixed layer is coated with a graphene oxide coating, and the other side surface is provided with a PAN nanofiber membrane; The MXene / kapok pulp mixture layer includes a modified kapok pulp layer and MXene randomly distributed in three dimensions within the modified kapok pulp layer.

[0010] Based on the above scheme and as a preferred embodiment of the above scheme: the modified kapok pulp layer uses kapok pulp treated with NaOH.

[0011] The present invention also relates to a method for preparing a medical electromagnetic shielding composite material, wherein modified kapok pulp is mixed with MXene and then vacuum filtered onto a PAN nanofiber membrane to form an MXene / kapok pulp mixed layer. After drying, graphene oxide is sprayed onto the other side of the MXene / kapok pulp mixed layer to form a graphene oxide coating.

[0012] Based on the above scheme and as a preferred embodiment of the above scheme, the synthesis process of MXene is as follows: LiF and HCl were thoroughly mixed in a polytetrafluoroethylene beaker and stirred continuously. Then, the MAX phase powder was gradually added to the solution while stirring. Place the mixture in a centrifuge tube and centrifuge; discard the supernatant, add deionized water to the precipitate in the centrifuge tube, resuspend, and then treat in an ultrasonic bath. Repeat the centrifugation-resuspending-ultrasonic process until the pH of the supernatant reaches the set value, and collect the lower precipitate.

[0013] Based on the above scheme and as a preferred embodiment of the above scheme, the preparation process of the modified kapok pulp is as follows: Kapok fibers are cut into 1-2 mm segments and mechanically pulped in water to produce kapok pulp. Then, the kapok pulp is treated with NaOH solution according to a set liquid-to-solid ratio. After rinsing to remove residual alkali, it is dried to obtain modified kapok pulp meal.

[0014] Based on the above scheme and as a preferred embodiment of the above scheme: the preparation process of the PAN nanofiber membrane 2 is as follows: PAN is dissolved in DMF solvent and stirred to obtain a uniform spinning solution; The spinning solution was loaded into a spinning syringe and extruded through a micro-infusion pump to perform electrospinning and produce a PAN nanofiber membrane.

[0015] The beneficial effects of this invention are as follows: The medical electromagnetic shielding composite material and its preparation method involved in this invention use NaOH to pretreat kapok pulp to enhance the hydrophilicity of kapok fibers, which are then combined with MXene sheets to construct a kapok-MXene conductive network with excellent hydrophilicity, moisture permeability and a three-dimensional porous structure. The multiple reflection and scattering units constructed together are designed to preferentially promote the absorption loss of electromagnetic waves, so that the electromagnetic shielding mechanism of the material changes from reflection-dominated to absorption-dominated (absorption loss accounts for more than 70%). Attached Figure Description

[0016] Figure 1 This is a process flow diagram of the preparation method of medical electromagnetic shielding composite materials; Figure 2 This is a schematic diagram of the structure of a medical electromagnetic shielding composite material; Figure 3 These are actual photos of medical electromagnetic shielding composite materials; Figure 4 This is a scanning electron microscope image of kapok pulp; Figure 5 This is a scanning electron microscope image of kapok pulp after NaOH treatment; Figure 6 This is a scanning electron microscope image of kapok pulp mixed with MXene after NaOH treatment; Figure 7 This is a scanning electron microscope image of a medical electromagnetic shielding composite material; Figure 8 This is a diagram showing the electromagnetic shielding data of medical electromagnetic shielding composite materials. Detailed Implementation

[0017] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. The given embodiments are merely illustrative of the invention and not intended to limit its scope. The embodiments provided below can serve as a guide for further improvements by those skilled in the art and do not constitute a limitation on the invention in any way. Unless otherwise specified, the experimental methods in the following embodiments are conventional methods, performed according to the techniques or conditions described in the literature in the art or according to the product instructions. Unless otherwise specified, the materials, reagents, etc., used in the following embodiments are commercially available.

[0018] Example 1 This embodiment relates to a medical electromagnetic shielding composite material, comprising an MXene / kapok pulp hybrid layer; one surface of the MXene / kapok pulp hybrid layer is coated with a graphene oxide coating 3, and the other surface is provided with a PAN nanofiber membrane 2; the MXene / kapok pulp hybrid layer includes a modified kpok pulp layer 4 and MXene 1 three-dimensionally randomly distributed within the modified kpok pulp layer 4. The modified kpok pulp layer uses kpok pulp treated with NaOH. MXene exhibits a three-dimensional random distribution within the kpok pulp fibers, and some MXene enters into the kpok pulp fibers.

[0019] After entering the material, electromagnetic waves are repeatedly reflected in the hollow kapok fiber channels, MXene / GO stacking interface and pores, which simultaneously excites various energy dissipation mechanisms such as interface polarization, dipole polarization and conductive loss, ultimately converting electromagnetic energy into heat energy and dissipating it.

[0020] The preparation method of medical electromagnetic shielding composite material includes the following steps: synthesis of MXene, preparation of modified kapok pulp, preparation of PAN nanofiber membrane and preparation of medical electromagnetic shielding composite material.

[0021] The synthesis of MXene was as follows: 2 g of LiF was thoroughly mixed with 40 mL of 9 mol / L HCl in a polytetrafluoroethylene beaker and stirred continuously for 30 minutes. Then, 2 g of MAX phase powder was gradually added to the solution, and the mixture was stirred continuously at 35°C for 24 hours. The resulting mixture was evenly distributed into four centrifuge tubes and centrifuged at 9000 rpm for 10 minutes. After discarding the supernatant, 40 mL of deionized water was added to the precipitate in each centrifuge tube, and the mixture was resuspended and treated in a high-power ultrasonic bath (750 W) for 10 minutes. The centrifugation-resuspending-ultrasonic process was repeated until the pH of the supernatant reached 5. Finally, the lower precipitate was collected for later use.

[0022] The preparation process of modified kapok pulp is as follows: kapok fibers are cut into 1-2 mm segments and mechanically beaten in water for 2 hours to make pulp. Then, the pulp is treated with 1 g / L NaOH solution at 50°C for 30 minutes at a liquid-to-solid ratio of 1:220. After thoroughly rinsing to remove residual alkali, it is dried at 40°C for 48 hours.

[0023] The kapok pulp used was observed using a scanning electron microscope, such as... Figure 4 As shown in the figure, the untreated raw kapok pulp fibers exhibit a flat, ribbon-like morphology.

[0024] The modified kapok pulp was observed using a scanning electron microscope, such as... Figure 5As shown in the image, the kapok fibers, after treatment, regain their original hollow cylindrical tubular structure, becoming fuller and more three-dimensional. Because the fibers expand and stretch from a flat state, the number of support points between them decreases, reducing compression and thus forming a larger, more interconnected three-dimensional porous network.

[0025] The preparation process of PAN nanofiber membrane was as follows: 5.6 g of PAN was dissolved in 34.4 g of DMF solvent, and the solution was continuously magnetically stirred at 70°C for 4 hours to obtain a uniform spinning solution. 20 mL of the spinning solution was loaded into a syringe and extruded at a rate of 0.05 mL / min using a micro-infusion pump. Electrospinning was performed under conditions of 0.03 MPa air pressure and 50 cm nozzle-receiver distance, and the PAN nanofiber membrane was successfully prepared.

[0026] The preparation process of the medical electromagnetic shielding composite material is as follows: NaOH-treated kapok pulp is mixed with MXene and then vacuum filtered onto a PAN nanofiber membrane. After vacuum drying at 50°C, a GO dispersion is sprayed onto the membrane to obtain the medical electromagnetic shielding composite material, namely the PAN / KNM / GO shielding material. In the PAN / KNM / GO shielding material, the amount of modified kapok pulp is 0.0085 g / cm², the amount of MXene is 0.0016 g / cm², and the amount of GO is 0.0016 g / cm². The amount of PAN is independent of the electromagnetic shielding performance, so the areal density of the PAN nanofiber membrane can be selected according to actual needs, specifically within the range of 0.023 g / cm². The amounts of the above components can be adjusted according to actual requirements.

[0027] The modified kapok pulp mixed with MXene was observed using a scanning electron microscope, such as... Figure 6 As shown in the figure, MXene nanosheets were successfully and uniformly loaded onto the surface of kapok fibers.

[0028] The medical electromagnetic shielding composite material was observed using a scanning electron microscope, such as... Figure 7 As shown, the material exhibits a distinct multilayered structure and abundant pore distribution. When electromagnetic waves enter the porous material, they undergo repeated reflection and scattering at numerous gas-solid interfaces. This process is similar to that of the multilayered structure, but more random and dense. Each reflection and scattering is accompanied by partial energy absorption. This significantly extends the propagation path of electromagnetic waves within the material, providing ample opportunities for energy dissipation and substantially enhancing absorption loss.

[0029] Natural kapok fibers were pretreated with NaOH solution to expose the hydroxyl groups on their surface through chemical means, thereby significantly enhancing the hydrophilicity of the kapok fibers. Using this modified kapok fiber as a carrier, it was combined with MXene sheets to construct a kapok-MXene conductive network with excellent hydrophilicity, moisture permeability, and a three-dimensional porous structure.

[0030] A multi-level, stable interface structure is formed between the kapok-MXene conductive network and the PAN nanofiber network. After NaOH treatment, the hydroxyl groups on the surface of the kapok fibers form strong hydrogen bonds with the oxygen-containing functional groups on the MXene / GO sheets. Simultaneously, the PAN nanofiber network provides mechanical support and fixation for the kapok skeleton.

[0031] A multi-reflection and scattering unit was constructed by combining the hollow structure of kapok fibers treated with NaOH with MXene sheets with high specific surface area. This structure was designed to preferentially promote the absorption loss of electromagnetic waves, so that the electromagnetic shielding mechanism of the material changes from reflection-dominated to absorption-dominated (absorption loss accounts for more than 70%).

[0032] A dense, continuous protective layer composed of GO is formed on the surface of the kapok-MXene porous network structure. This protective layer acts as a physical barrier, specifically designed to prevent water and oxygen from contacting the internal MXene, thereby achieving antioxidant protection for the MXene.

[0033] Comparative Example 1 The shielding material used in this comparative example is a PAN / GO shielding material. The specific preparation process is as follows: a 5 wt% GO dispersion is uniformly sprayed onto a PAN nanofiber membrane using a spray method. In the PAN / GO shielding material, the amount of GO is 0.0032 g / cm².

[0034] Comparative Example 2 The shielding material involved in this comparative example is a PAN / MXene / GO shielding material. The specific preparation process is as follows: equal masses of MXene and GO are dispersed in water, and after 30 minutes of sonication and 1 hour of stirring, a 5 wt% MXene / GO dispersion is obtained. This dispersion is then sprayed onto a PAN nanofiber membrane. In the PAN / MXene / GO mixture, the amount of MXene is 0.0016 g / cm², and the amount of GO is 0.0016 g / cm².

[0035] Comparative Example 3 The shielding material involved in this comparative example is a PAN / KM / GO shielding material. The specific preparation process is as follows: kapok pulp and MXene are mixed, then vacuum filtered and pressed onto a PAN nanofiber membrane. After vacuum drying at 50°C, a GO dispersion is sprayed onto the mixture. In the PAN / KM / GO shielding material, the amount of kapok pulp is 0.0085 g / cm², the amount of MXene is 0.0016 g / cm², and the amount of GO is 0.0016 g / cm².

[0036] Electromagnetic shielding tests were conducted on Example 1, Comparative Example 1, Comparative Example 2, Comparative Example 3, and the PAN nanofiber membrane. The experimental results are shown in the figure below. Figure 8 As shown in the figure, the composite material exhibits excellent shielding performance in the 0.5-3 GHz range. Among them, the PAN / KNM / GO composite material demonstrates the best overall shielding performance, with an average shielding effectiveness of up to 31.9 dB. This is mainly attributed to the unique porous structure of its middle layer. The kapok pulp modified with sodium hydroxide not only retains higher porosity but also introduces a large number of oxygen-containing functional groups. These functional groups are tightly bound to MXene nanosheets through strong hydrogen bonding, significantly increasing the loading of MXene on the fiber surface and inside, thereby constructing a continuous and efficient conductive network.

[0037] In comparison, the average shielding effectiveness of the PAN / KM / GO composite material (without NaOH treatment) is 25.0 dB, which, while still good, is slightly lower than that of PAN / KNM / GO. This is because the untreated kapok fiber structure is relatively flat and has a small specific surface area, resulting in limited MXene loading and weakened conductive network integrity and interfacial polarization capability. The shielding performance of PAN / GO and PAN / MXene / GO composite materials further declines, reaching only 20.6 dB and 15.6 dB respectively. This is mainly due to the lack of the hollow structure and multi-level pores provided by kapok fibers, which prevents effective multiple reflections and attenuation of electromagnetic waves. In particular, the simple physical mixing of GO and MXene in PAN / MXene / GO leads to poor interfacial bonding, limiting charge transport and polarization relaxation, thus reducing the overall shielding efficiency.

[0038] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A medical electromagnetic shielding composite material, characterized in that, It includes an MXene / kapok pulp mixture layer; one side of the MXene / kapok pulp mixture layer is coated with a graphene oxide coating (3), and the other side is provided with a PAN nanofiber membrane (2). The MXene / kapok pulp mixture layer includes a modified kapok pulp layer (4) and MXene (1) randomly distributed in three dimensions within the modified kapok pulp layer (4).

2. The medical electromagnetic shielding composite material according to claim 1, characterized in that, The modified kapok pulp layer used is kapok pulp treated with NaOH.

3. A method for preparing a medical electromagnetic shielding composite material, characterized in that, After mixing modified kapok pulp with MXene, the mixture was vacuum filtered onto a PAN nanofiber membrane (2) to form an MXene / kapok pulp mixed layer. After drying, graphene oxide was sprayed onto the other side of the MXene / kapok pulp mixed layer to form a graphene oxide coating (3).

4. The method for preparing a medical electromagnetic shielding composite material according to claim 3, characterized in that, The synthesis process of MXene is as follows: LiF and HCl were thoroughly mixed in a polytetrafluoroethylene beaker and stirred continuously. Then, the MAX phase powder was gradually added to the solution while stirring. Place the mixture in a centrifuge tube and centrifuge; discard the supernatant, add deionized water to the precipitate in the centrifuge tube, resuspend, and then treat in an ultrasonic bath. Repeat the centrifugation-resuspending-ultrasonic process until the pH of the supernatant reaches the set value, and collect the lower precipitate.

5. The method for preparing a medical electromagnetic shielding composite material according to claim 3, characterized in that, The preparation process of the modified kapok pulp is as follows: Kapok fibers are cut into 1-2 mm segments and mechanically pulped in water to produce kapok pulp. Then, the kapok pulp is treated with NaOH solution according to a set liquid-to-solid ratio. After rinsing to remove residual alkali, it is dried to obtain modified kapok pulp meal.

6. The method for preparing a medical electromagnetic shielding composite material according to claim 3, characterized in that, The preparation process of the PAN nanofiber membrane (2) is as follows: PAN is dissolved in DMF solvent and stirred to obtain a uniform spinning solution; The spinning solution was loaded into a spinning syringe and extruded through a micro-infusion pump to perform electrospinning and produce a PAN nanofiber membrane.

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