Flexible electromagnetic shielding film

Abstract

The invention provides a flexible electromagnetic shielding film and a preparation method thereof. The preparation method comprises the following steps: mixing metal gallium and metal indium in a preset proportion to prepare a gallium-indium alloy; the preparation method comprises the following steps: putting a preset mass of gallium-indium alloy into an isopropanol solution, and treating through an ultrasonic cell disruption system to obtain a liquid metal particle suspension; stirring magnetic functional nanoparticles, an electrostatic spinning high-molecular elastomer and a solvent at normal temperature for a preset time to obtain an electrostatic spinning homogeneous solution; treating the electrostatic spinning homogeneous solution by adopting an electrostatic spinning process to obtain a magnetic nanofiber membrane; and spraying the liquid metal particle suspension onto the magnetic nanofiber membrane by adopting an electrostatic spraying process to obtain the flexible electromagnetic shielding film. According to the flexible electromagnetic shielding film and the preparation method thereof, the problem that the stability of an existing shielding material is reduced under the stretching effect can be solved.

Description

Technical Field

[0001] The present invention relates to the technical field of electromagnetic shielding material preparation, and more specifically, to a flexible electromagnetic shielding film and a preparation method thereof. Background Art

[0002] With the advent of the 5G era, electronic devices tend to be high-frequency and highly integrated, which inevitably brings some serious problems such as electromagnetic radiation and electromagnetic interference, seriously affecting the normal operation of electronic devices and the secure transmission of information, and even causing harm to the human body.

[0003] Electromagnetic wave shielding materials can effectively protect electronic devices and the human body by cutting off the transmission path of electromagnetic waves, and are one of the most effective means to solve electromagnetic radiation and electromagnetic wave pollution at present. Although traditional metal-based electromagnetic shielding materials have good electromagnetic shielding performance, their shielding mechanism is single, mainly based on reflection, and limitations such as high density, high thickness, easy corrosion, non-stretchable or attenuation of electromagnetic shielding efficiency under stretching are difficult to meet the growing needs of emerging fields such as flexible electronic devices. Therefore, people are committed to developing flexible new electromagnetic shielding materials with ultra-thin and stable shielding efficiency under stretching.

[0004] Flexible electromagnetic shielding materials are usually composed of a flexible substrate and an electromagnetic shielding loss material. Currently, there are mainly two preparation strategies for flexible electromagnetic shielding materials:

[0005] (1) Incorporating conductive fillers into elastomeric composites. However, for the shielding materials prepared by this method, the separation of solid conductive fillers caused by stretching will lead to a decrease in conductivity, making the conductivity and stretchability incompatible, and the shielding efficiency decreases under deformation. The introduction of magnetic particles can improve impedance matching and electromagnetic wave attenuation, and promote electromagnetic wave absorption. The electromagnetic shielding efficiency can be improved by introducing magnetic functional nanoparticles.

[0006] (2) Encapsulating conductive porous / multilayer structures with an elastic matrix; providing multiple interfaces by constructing a multilayer porous structure, having the advantages of reflection and absorption of multiple interfaces, being able to perform multiple reflections and absorptions on electromagnetic waves, and improving the shielding performance. The electromagnetic shielding efficiency of the shielding materials obtained by this method is high, but the stretching is limited, and the inherent rigid porous structure is easy to break.

[0007] Based on this, there is an urgent need for a film material and a preparation method thereof that can still have a stable electromagnetic shielding effect under stretching. Summary of the Invention

[0008] In view of the above problems, the purpose of the present invention is to provide a flexible electromagnetic shielding film to solve the problem of reduced stability of existing shielding materials under stretching.

[0009] The flexible electromagnetic shielding film provided by the present invention is a multi-layer structured composite film composed of an elastic matrix magnetic fiber porous film and a liquid metal particle conductive film alternatingly; wherein,

[0010] The number of layers of the multi-layer structured composite film is at least two layers.

[0011] In addition, preferably, the flexible electromagnetic shielding film is made by an electrospinning process and an electrostatic spraying process based on an electrospinning homogeneous solution containing magnetic powder and a liquid metal particle suspension.

[0012] In addition, preferably, the content of magnetic powder in the electrospinning homogeneous solution is 0 to 85 wt%; and / or, the content of liquid metal in the liquid metal particle suspension is 0 to 50 Vol%.

[0013] In addition, preferably, the thickness of the flexible electromagnetic shielding film is 10 to 1000 μm; and / or, the stretching range of the flexible electromagnetic shielding film is 0 to 600%.

[0014] On the other hand, the present invention also provides a preparation method of the flexible electromagnetic shielding film as described above, and the preparation method includes:

[0015] Respectively prepare a liquid metal particle suspension and an electrospinning homogeneous solution containing magnetic powder;

[0016] Based on the electrospinning homogeneous solution and the liquid metal particle suspension, the flexible electromagnetic shielding film is made by an electrospinning process and an electrostatic spraying process.

[0017] In addition, preferably, the process of preparing the liquid metal particle suspension includes:

[0018] Mix a preset ratio of gallium metal and indium metal to make a gallium-indium alloy;

[0019] Take a preset mass of the gallium-indium alloy and place it in an isopropanol solution, and obtain the liquid metal particle suspension after being processed by an ultrasonic cell disruption system.

[0020] In addition, preferably, the process of preparing the electrospinning homogeneous solution includes:

[0021] Stir magnetic functional nanoparticles, an electrospinning polymer elastomer and a solvent at room temperature for a preset time to obtain the electrospinning homogeneous solution.

[0022] In addition, preferably, during the process of preparing the electrospinning homogeneous solution,

[0023] The magnetic functional nanoparticles include at least one of nano-scale Fe powder, Ni powder, Co powder, Fe3O4 powder, and FeNi powder; and / or,

[0024] The electrospun polymer elastomer includes at least one of thermoplastic polyurethane, block copolymer, and thermoplastic elastomer; and / or,

[0025] The solvent includes at least one of tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide, acetone, dichloromethane, toluene, and ethyl acetate.

[0026] In addition, a preferred solution is that the process of making the flexible electromagnetic shielding film based on the liquid metal particle suspension and the electrospun homogeneous solution through the electrospinning process and the electrostatic spraying process includes:

[0027] Processing the electrospun homogeneous solution by the electrospinning process to obtain a magnetic nanofiber membrane;

[0028] Spraying the liquid metal particle suspension onto the magnetic nanofiber membrane by the electrostatic spraying process to obtain the flexible electromagnetic shielding film.

[0029] In addition, a preferred solution is that the electromagnetic shielding absorption loss of the flexible electromagnetic shielding film is regulated by regulating the content of magnetic powder in the electrospun homogeneous solution; and,

[0030] The conductivity of the flexible electromagnetic shielding film is regulated by regulating the content of liquid metal in the liquid metal particle suspension.

[0031] Compared with the prior art, the flexible electromagnetic shielding film provided by the present invention is a multi-layer structured composite film composed of an elastic matrix magnetic fiber porous film and a liquid metal particle conductive film alternately, with a thin thickness, good flexibility, and its electromagnetic shielding mechanism mainly based on absorption loss, and the electromagnetic shielding performance is stable under tensile action; in addition, the preparation method of the flexible electromagnetic shielding film provided by the present invention is prepared by using the electrospinning process and the electrostatic spraying process, and the obtained flexible electromagnetic shielding film has the advantages of rich porous structure, ultra-thin, flexibility, easy processing, etc. Its rich porous structure is beneficial to multi-stage reflection at the hole interface, and the magnetic functional particles can improve the absorption attenuation of electromagnetic waves through magnetic loss, thereby improving the shielding performance.

[0032] To achieve the above and related purposes, one or more aspects of the present invention include the features that will be described in detail later and particularly pointed out in the claims. The following description and the accompanying drawings detail certain exemplary aspects of the present invention. However, these aspects indicate only some of the various ways in which the principles of the present invention can be used. In addition, the present invention is intended to include all these aspects and their equivalents. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Other objects and results of the present invention will become more apparent and easier to understand by referring to the following description in conjunction with the drawings and the content of the claims. In the drawings:

[0034] Figure 1 is a topographical view of the (magnetic fiber / LM multi-layer structured) flexible electromagnetic shielding film provided by the present invention (the left side is the macroscopic view and the right side is the microscopic view);

[0035] Figure 2 is a cyclic fatigue diagram of the (magnetic fiber / LM multi-layer structured) flexible electromagnetic shielding film provided by the present invention;

[0036] Figure 3 is a diagram for characterizing the electromagnetic shielding performance of the flexible electromagnetic shielding film prepared by the preparation method of the (magnetic fiber / LM multi-layer structured) flexible electromagnetic shielding film provided in Example 1 of the present invention under tension;

[0037] Figure 4 is a diagram for characterizing the electromagnetic shielding performance of the flexible electromagnetic shielding film prepared by the preparation method of the (magnetic fiber / LM multi-layer structured) flexible electromagnetic shielding film provided in Example 2 of the present invention under tension.

[0038] In all the drawings, the same reference numerals indicate similar or corresponding features or functions. DETAILED DESCRIPTION OF THE INVENTION

[0039] In the following description, for the purpose of illustration, in order to provide a comprehensive understanding of one or more embodiments, many specific details are set forth. However, it is obvious that these embodiments can also be implemented without these specific details. In other instances, well-known structures and devices are shown in block diagram form for the convenience of describing one or more embodiments.

[0040] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention; the terms "first", "second", "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance; in addition, unless otherwise clearly specified and defined, the terms "installed", "connected", "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0041] Figure 1 The microscopic morphology of the (magnetic fiber / LM multi-layer structured) flexible electromagnetic shielding film provided by the present invention is shown. Figure 2 It is the cyclic fatigue diagram of the (magnetic fiber / LM multi-layer structured) flexible electromagnetic shielding film provided by the present invention.

[0042] Combined Figure 1 with Figure 2 It can be seen that the flexible electromagnetic shielding film provided in Embodiment 1 of the present invention is a multi-layer structured composite film (i.e., a magnetic nanofiber / LM multi-layer structured flexible film) alternately composed of an elastic matrix magnetic fiber porous film and a liquid metal particle conductive film; moreover, the multi-layer structured composite film has a multi-layer structure (at least two layers).

[0043] It should be noted that the elastic matrix magnetic fiber porous film is made by an electrospinning process from an electrospinning homogeneous solution containing magnetic powder, and the liquid metal particle conductive film is formed by spraying a liquid metal particle suspension onto the surface of the elastic matrix magnetic fiber porous film through an electrostatic spraying process. Moreover, the liquid metal in the liquid metal particle suspension, as an intrinsically flexible conductive material, has both a nearly zero Young's modulus and a high electrical conductivity. After experimental tests, it is a good choice for developing flexible and stretchable electromagnetic shielding materials; the electrospun nanofiber mat (equivalent to the elastic matrix magnetic fiber porous film) has the advantages of rich porous structure, light weight, ultra-thin, flexibility, cost-effectiveness, easy processing, etc. After experimental tests, it can provide comprehensive good performance for electromagnetic shielding.

[0044] The flexible electromagnetic shielding film provided by the present invention composites an intrinsic flexible conductive material LM (liquid metal) with magnetic functional nanoparticles having high magnetic permeability (particles in the electrospun homogeneous solution containing magnetic powder), and designs a three-dimensional network structure for it through electrospinning to improve the absorption and attenuation of electromagnetic waves, thereby preparing a thin and light flexible electromagnetic shielding material with stable electromagnetic shielding performance under tensile deformation provided by the present invention.

[0045] It should be noted that the flexible electromagnetic shielding film provided by the present invention is made by an electrospinning process (the electrospun homogeneous solution containing magnetic powder adopts the electrospinning process) and an electrostatic spraying process (the liquid metal particle suspension adopts the electrostatic spraying process) based on the liquid metal particle suspension and the electrospun homogeneous solution containing magnetic powder.

[0046] In addition, it should also be noted that the content of magnetic powder in the electrospun homogeneous solution provided by the present invention is usually set to 0 - 85 wt%, and the content of magnetic powder in the electrospun homogeneous solution is preferably selected from any content among 0, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85. Of course, the content range between any two values can also be selected; the higher the content of magnetic powder in the electrospun homogeneous solution, the better the electromagnetic shielding effect of the formed flexible electromagnetic shielding film. By regulating the content of magnetic powder to control the electromagnetic shielding absorption loss, the electromagnetic shielding performance of the flexible electromagnetic shielding film can be regulated.

[0047] The content of liquid metal in the liquid metal particle suspension is usually set to 0 - 50 Vol%, and the content of LM is preferably selected from any content among 0, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50. Of course, the content range between any two values can also be selected; the higher the content of liquid metal in the liquid metal particle suspension, the higher the conductivity of the formed flexible electromagnetic shielding film, and the higher the electromagnetic shielding effect of the electromagnetic shielding film.

[0048] The thickness of the flexible electromagnetic shielding film is usually set to 10 - 1000 μm, and the thickness of the flexible electromagnetic shielding film is preferably selected from any thickness among 10, 50, 100, 150, 200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, 1000. Of course, the thickness range between any two values can also be selected;

[0049] The stretching range of the flexible electromagnetic shielding film is usually 0 to 600%, and the stretching deformation of the flexible electromagnetic shielding film can be selected from any deformation amount or the deformation range between any two values among 0, 50, 100, 150, 200, 250, 300, 350, 400, 450, 500, 550, 600; the electromagnetic shielding effectiveness of the flexible electromagnetic shielding film is adjustable and the shielding effectiveness is stable under stretching, and the shielding effectiveness range is 5 to 100 dB.

[0050] To further illustrate the preparation process of the flexible electromagnetic shielding film provided by the present invention, the preparation method of the flexible electromagnetic shielding film provided by the present invention will be described below by way of examples.

[0051] Example 1

[0052] Figure 3 It is a characterization diagram of the electromagnetic shielding performance of the flexible electromagnetic shielding film (magnetic fiber / LM multi-layer structure type) prepared by the preparation method of the flexible electromagnetic shielding film provided in Example 1 of the present invention under stretching. Combined with Figures 1 to 3 , the present invention provides a preparation method of a flexible electromagnetic shielding film, and the preparation method includes:

[0053] Prepare a liquid metal particle suspension and an electrospinning homogeneous solution containing magnetic powder respectively;

[0054] Based on the electrospinning homogeneous solution and the liquid metal particle suspension, the flexible electromagnetic shielding film is made by an electrospinning process and an electrostatic spraying process.

[0055] Specifically, the process of preparing the liquid metal particle suspension generally includes:

[0056] Mix a preset ratio of gallium metal and indium metal to form a gallium-indium alloy;

[0057] Take a preset mass of the gallium-indium alloy and place it in an isopropanol solution, and obtain the liquid metal particle suspension after being processed by an ultrasonic cell disruption system.

[0058] For example, high-purity gallium metal (99.99%) and indium (99.995%) with mixing ratios of 75 wt% and 25 wt% respectively are mixed to obtain a gallium-indium alloy (EGaIn). Take 25 g of EGaIn and place it in 100 ml of an isopropanol solution, and obtain a liquid metal (LM) particle suspension after ultrasonic treatment for 30 min by an ultrasonic cell disruption system. After standing for 20 min, the settled and separated liquid metal slurry is transferred to a syringe for use in the subsequent electrostatic spraying process.

[0059] On the other hand, the process of preparing the electrospinning homogeneous solution includes:

[0060] The electrospinning homogeneous solution is obtained by stirring magnetic functional nanoparticles, electrospinning polymer elastomers, and a solvent at room temperature for a preset time.

[0061] For example, FeNi nano magnetic powder is used as the magnetic functional nanoparticles, TPU particles are used as the electrospinning polymer, and a tetrahydrofuran / N,N-dimethylformamide mixed system is used as the solvent (volume ratio 1:1). The homogeneous solution with a FeNi magnetic powder mass ratio of 30 wt% is obtained by mechanical stirring at room temperature for 72 h, and the above solution is transferred to a syringe for use in the subsequent electrospinning process.

[0062] Furthermore, the process of fabricating the flexible electromagnetic shielding film based on the electrospinning homogeneous solution and the liquid metal particle suspension through electrospinning and electrostatic spraying processes includes:

[0063] The electrospinning homogeneous solution is processed by electrospinning to obtain a magnetic nanofiber membrane; the liquid metal particle suspension is sprayed onto the magnetic nanofiber membrane by electrostatic spraying to obtain the flexible electromagnetic shielding film.

[0064] For example, the above homogeneous solution and LM slurry (liquid metal particle suspension) are prepared into a multi-layer structure composite electromagnetic shielding film through electrospinning and electrostatic spraying processes; among them, when preparing the magnetic nanofiber membrane by electrospinning, the solution pumping rate is preferably 0.1 mm / min, and the film is collected by a rotating drum wrapped with aluminum foil. Then the EGaIn slurry (i.e., the liquid metal particle suspension) is evenly sprayed on the magnetic nanofibers, and the pumping rate of EGaIn electrostatic spraying is preferably 1 mm / min; and, the thickness of the prepared multi-layer structure composite electromagnetic shielding film is preferably 200 μm, and any part of the film can be cut for further performance characterization of the homogeneous solution and LM slurry to prepare a multi-layer structure composite electromagnetic shielding film.

[0065] It should be noted that in this embodiment, the fabricated multi-layer structure composite flexible and stretchable electromagnetic shielding film has a porous network structure, a thickness of 200 μm, an LM volume ratio of 35 Vol%, and a tensile strain of 100%; the film has good flexibility and strong processability; after 1000 fatigue cycles in the 100% tensile range, the electromagnetic shielding effectiveness is maintained at 60 dB, which can shield 99.9999% of electromagnetic waves, and the specific shielding effectiveness (SSE) can reach 300 dB / mm.

[0066] In addition, it should be noted that during the preparation of the electrospinning homogeneous solution, other conductive particles can also be selected as the magnetic functional nanoparticles, for example, it can include at least one of nano-scale Fe powder, Ni powder, Co powder, Fe3O4 powder, and FeNi powder; in addition, other polymers can also be selected as the electrospinning polymer elastomer, for example, it can include at least one of thermoplastic polyurethane, block copolymer, and thermoplastic elastomer; furthermore, other solvents can also be used as the solvent for the electrospinning homogeneous solution, for example, it can include at least one of tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide, acetone, dichloromethane, toluene, and ethyl acetate solvent.

[0067] Example 2

[0068] Figure 4 This is a characterization diagram of the electromagnetic shielding performance of the flexible electromagnetic shielding film prepared by the preparation method of the (magnetic fiber / LM multi-layer structure type) flexible electromagnetic shielding film provided in Example 2 of the present invention under tension. Combining Figure 1 , Figure 2 and Figure 4 , the present invention further provides a preparation method of a flexible electromagnetic shielding film, and its specific method includes:

[0069] The first step is to obtain a gallium-indium alloy (EGaIn) by mixing high-purity gallium (99.99%) and indium (99.995%) at a mixing ratio of 75 wt% and 25 wt% respectively. Take 25 g of EGaIn and place it in 100 ml of isopropyl alcohol solution, and obtain a liquid metal (LM) particle suspension after ultrasonic treatment for 30 min by an ultrasonic cell disruption system. After standing for 20 min, the settled liquid metal slurry is transferred to a syringe in batches;

[0070] The second step is to use FeNi nano magnetic powder as the magnetic functional nanoparticle, TPU as the electrospinning polymer, and a tetrahydrofuran / N,N-dimethylformamide mixed system as the solvent (volume ratio 1:1), and stir at room temperature for 72 h by mechanical stirring to obtain homogeneous solutions with FeNi magnetic powder mass ratios of 10 wt%, 50 wt%, and 70 wt% respectively, and transfer the above solutions to syringes respectively;

[0071] In the third step, the above homogeneous solution and LM slurry are prepared into a multi-layered composite electromagnetic shielding film through electrospinning and electrostatic spraying processes. When preparing the magnetic nanofiber film, the solution pumping rate is 0.1 mm / min, and the film is collected on a rotating drum wrapped with aluminum foil. Then, the EGaIn slurry is evenly sprayed on the magnetic nanofibers, and the pumping rate of EGaIn electrostatic spraying is 1 mm / min. The prepared multi-layered composite electromagnetic shielding film has a thickness of 200 μm, and the volume ratio of LM is 35 Vol%. Any part of the film can be cut for further performance characterization.

[0072] In this embodiment, the multi-layered composite flexible and stretchable electromagnetic shielding film has a porous network structure with a thickness of 200 μm. The tensile strains at 10 wt%, 50 wt%, and 70 wt% are 150%, 90%, and 40% respectively. The film has good flexibility and strong processability. Its electromagnetic shielding effectiveness is 46 dB (10 wt%), 65 dB (50 wt%), and 76 dB (70 wt%) respectively. As the magnetic powder content increases, the electromagnetic shielding effectiveness improves.

[0073] It should be noted that in this embodiment (Embodiment 2), different from Embodiment 1, the electromagnetic shielding absorption loss can be regulated by controlling the magnetic powder content, thereby regulating the electromagnetic shielding effectiveness. As the magnetic powder content increases, the tensile properties of the film decrease, but its electromagnetic shielding effectiveness increases, and it can be selected according to actual needs.

[0074] Embodiment 3

[0075] The present invention provides another method for preparing a flexible electromagnetic shielding film, and the specific method includes:

[0076] In the first step, high-purity gallium (99.99%) and indium (99.995%) with mixing ratios of 75 wt% and 25 wt% respectively are mixed to obtain a gallium-indium alloy (EGaIn). Different gradients of EGaIn are placed in 100 ml of isopropanol solution, and after ultrasonic treatment for 30 min by an ultrasonic cell disruption system, a liquid metal (LM) particle suspension is obtained. After standing for 20 min, the settled and separated liquid metal slurry is transferred to a syringe in batches;

[0077] In the second step, FeNi nano magnetic powder is used as the magnetic functional nano particle, TPU particles are used as the electrospinning polymer, and tetrahydrofuran / N,N-dimethylformamide is used as the solvent (volume ratio 1:1). The mixture is stirred at room temperature for 72 h by mechanical stirring to obtain a homogeneous solution with 30 wt% of FeNi magnetic powder, and the above solution is transferred to a syringe;

[0078] In the third step, the above homogeneous solution and LM slurry are prepared into a multi-layer structured composite electromagnetic shielding film through electrospinning and electrostatic spraying processes. When preparing TPU magnetic nanofibers, the solution pumping rate is 0.1 mm / min, and the film is collected by a rotating drum wrapped with aluminum foil. Then, the EGaIn slurry is evenly sprayed on the magnetic nanofibers, and the pumping rate of EGaIn electrostatic spraying is 1 mm / min. The thickness of the prepared multi-layer structured composite electromagnetic shielding film is 200 μm, and the volume ratios of LM are 10 Vol%, 20 Vol%, and 30 Vol% respectively. Any part of the film can be cut for further performance characterization.

[0079] In this embodiment, the multi-layer structured flexible and stretchable electromagnetic shielding film has a porous network structure, with a thickness of 200 μm. The tensile strains at 10 Vol%, 20 Vol%, and 30 Vol% are 180%, 160%, and 135% respectively. The film has good flexibility and strong processability. Its electromagnetic shielding effectiveness is 1.99 dB (10 Vol%), 9.23 dB (20 Vol%), and 27.21 dB (30 Vol%) respectively. As the LM content increases, the electromagnetic shielding effectiveness improves.

[0080] It should be noted that in this embodiment (Embodiment 3), different from Embodiment 1, the conductivity of the film can be regulated by controlling the LM content, so as to achieve the purpose of regulating the electromagnetic shielding effectiveness of the film. As the LM content increases, the tensile properties of the film decrease, but its electromagnetic shielding effectiveness increases, and it can be selected according to actual needs.

[0081] From the above specific implementation manners, it can be seen that the flexible electromagnetic shielding film and its preparation method provided by the present invention have at least the following advantages:

[0082] 1. The flexible electromagnetic shielding film prepared by using the flexible electromagnetic shielding film provided by the present invention has a thin thickness, good flexibility, and its electromagnetic shielding mechanism is mainly absorption loss; the electrospun magnetic nanofiber membrane (elastic matrix magnetic fiber porous membrane, that is, the magnetic nanofiber membrane made by the electrospinning process) has the advantages of rich porous structure, ultra-thin, flexibility, and easy processing. Its rich porous structure is conducive to multi-stage reflection at the hole interface, and the magnetic functional particles can improve the absorption and attenuation of electromagnetic waves through magnetic loss, thereby improving the shielding performance. In the frequency range of 8 - 12 GHz, 99.9999% of electromagnetic waves can be shielded.

[0083] 2. The flexible electromagnetic shielding film prepared by using the flexible electromagnetic shielding film provided by the present invention has stable electromagnetic shielding performance under stretching. Under the stretching state, the highly fluid LM maintains its excellent conductivity through the flow compensation mechanism, and thus a stable electromagnetic shielding performance under stretching is obtained. In the 100% stretching range, the shielding performance is stable at about 60 dB.

[0084] 3. The flexible electromagnetic shielding film prepared by using the flexible electromagnetic shielding film provided by the present invention has good tensile stability. After 1000 tensile cycles, the shielding performance of the film is improved.

[0085] 4. The process of the method for preparing the flexible electromagnetic shielding film provided by the present invention is simple and can be prepared in large quantities.

[0086] As described above with reference to Figures 1 to 4 The flexible electromagnetic shielding film according to the present invention is described by way of example. However, those skilled in the art should understand that various improvements can be made to the above-mentioned flexible electromagnetic shielding film proposed by the present invention without departing from the content of the present invention. Therefore, the protection scope of the present invention should be determined by the content of the appended claims.

Claims

1. A flexible electromagnetic shielding film; characterized in that, The flexible electromagnetic shielding film is a multi-layer structure composite film composed of an elastic matrix magnetic fiber porous film and a liquid metal particle conductive film alternately; wherein, The multi-layer structure composite film has at least two layers.

2. The flexible electromagnetic shielding film according to claim 1, characterized in that: The flexible electromagnetic shielding film is made through an electrostatic spinning process and an electrostatic spraying process based on an electrostatic spinning homogeneous solution containing magnetic powder and a liquid metal particle suspension.

3. The flexible electromagnetic shielding film according to claim 2, characterized in that: The content of magnetic powder in the electrospinning homogeneous solution is 0 to 85 wt %; and / or, The content of liquid metal in the liquid metal particle suspension is 0-50 Vol%.

4. The flexible electromagnetic shielding film according to claim 2, characterized in that: The thickness of the flexible electromagnetic shielding film is 10 to 1000 μm; and / or, The stretching range of the flexible electromagnetic shielding film is 0-600%.

5. A method for preparing a flexible electromagnetic shielding film according to any one of claims 1 to 4, characterized in that: The preparation method comprises: preparing a liquid metal particle suspension and an electrospinning homogeneous solution containing magnetic powder respectively; The flexible electromagnetic shielding film is manufactured based on the electrostatic spinning homogeneous solution and the liquid metal particle suspension through an electrostatic spinning process and an electrostatic spraying process.

6. The method for preparing a flexible electromagnetic shielding film according to claim 5, characterized in that: The process of preparing the liquid metal particle suspension comprises: Mixing metal gallium and metal indium in a preset ratio to form a gallium-indium alloy; A preset mass of gallium-indium alloy is placed in an isopropanol solution and treated by an ultrasonic cell disruption system to obtain the liquid metal particle suspension.

7. The method for preparing a flexible electromagnetic shielding film according to claim 6, characterized in that: The process of preparing the electrospinning homogeneous solution comprises: The magnetic functional nanoparticles, the electrospinning polymer elastomer and the solvent are stirred at room temperature for a preset time to obtain the electrospinning homogeneous solution.

8. The method for preparing a flexible electromagnetic shielding film according to claim 7, characterized in that: In the process of preparing the electrospinning homogeneous solution, The magnetic functional nanoparticles include at least one of nano-sized Fe powder, Ni powder, Co powder, Fe3O4 powder, and FeNi powder; and / or, The electrospinning polymer elastomer includes at least one of thermoplastic polyurethane, block copolymer and thermoplastic elastomer; and / or, The solvent includes at least one of tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide, acetone, dichloromethane, toluene and ethyl acetate.

9. The method for preparing a flexible electromagnetic shielding film according to claim 7, characterized in that: The process of manufacturing the flexible electromagnetic shielding film based on the electrospinning homogeneous solution and the liquid metal particle suspension through an electrospinning process and an electrostatic spraying process comprises: The electrospinning homogeneous solution is treated by an electrospinning process to obtain a magnetic nanofiber membrane; The liquid metal particle suspension is sprayed onto the magnetic nanofiber film by an electrostatic spraying process to obtain the flexible electromagnetic shielding film.

10. The method for preparing a flexible electromagnetic shielding film according to any one of claims 5 to 9, characterized in that: The electromagnetic shielding absorption loss of the flexible electromagnetic shielding film is regulated by regulating the content of magnetic powder in the electrospinning homogeneous solution; and, The conductivity of the flexible electromagnetic shielding film is regulated by regulating the content of liquid metal in the liquid metal particle suspension.

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