Flexible conductive composite material insensitive to strain / temperature change and preparation method and application thereof

Abstract

The invention discloses a flexible conductive composite material insensitive to strain / temperature change and a preparation method and application thereof. The conductive composite material comprises liquid metal and a cured polymer, the liquid metal is distributed in the cured polymer so as to form a communicating channel in the cured polymer, and the liquid metal forms a continuous phase structure in the polymer so as to form a polymer / liquid metal bicontinuous phase network structure. By designing the bicontinuous phase of the liquid metal / flexible polymer, the conductive composite material which is insensitive to temperature change and deformation is prepared, and the conductive composite material can show remarkable conductive stability under the condition of large-range temperature change or various mechanical deformations. The invention develops a new idea for multifunctional application of the flexible conductive composite material in an extremely complex environment.

Description

Technical Field

[0001] The present invention relates to the field of conductive materials, in particular to a flexible conductive composite material that is insensitive to both strain and temperature change, and a preparation method and application thereof. Background Art

[0002] Conductive polymer composites are flexible, have good conductivity, and have excellent cyclic stability. They are widely used in soft robotics development, biomedicine, electromagnetic shielding protection, flexible energy storage, and wearable devices. With the continuous development of flexible electronic technology, the application scenarios of conductive polymers have become more complex, and higher requirements have been placed on the structural and performance stability of materials under large deformations and wide temperature ranges. Specifically, when used as wires or electrodes, resistance changes caused by mechanical deformation or temperature changes may impair signal conduction, resulting in the failure to achieve the intended function. The design of the calibration system can reduce this effect, but it usually requires complex circuits, which ultimately sacrifices signal fidelity.

[0003] Conventional conductive composites typically consist of a flexible elastomeric matrix and one or more conductive fillers, such as carbon nanomaterials, metallic materials, and transition metal carbides / nitrides. When polymer composites undergo significant temperature fluctuations, the vastly different thermal expansion coefficients between the polymer matrix and the conventional filler cause separation at the interface, severely disrupting the percolation network. Furthermore, under various mechanical deformations, the significant modulus mismatch between the conventional filler and the polymer matrix can cause separation at the interface, resulting in significant changes in the material's resistivity.

[0004] In the field of stretchable conductors, low-modulus conductive materials such as liquid metals (LM) and ionic liquids have gradually attracted attention due to their excellent fluidity and conductivity. However, ionic liquids have low intrinsic conductivity and structural instability at high temperatures, which significantly limits their application in wide-temperature conductive polymer composites. Currently, researchers have conducted a lot of research in the field of LM conductive polymer composites. Most of these studies focus on the change in resistance of the material under mechanical deformation, while its conductive behavior in high-temperature environments remains to be systematically studied. Therefore, further work is still needed to develop elastomeric materials with high conductivity and stable conductivity over a wide temperature range or under various mechanical deformations. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0006] A conductive composite material, comprising: liquid metal and a solidified polymer; the liquid metal is distributed in the solidified polymer to form connecting channels in the solidified polymer, and the liquid metal forms a continuous phase structure in the polymer, thereby forming a polymer / liquid metal dual-continuous phase network structure.

[0007] According to an embodiment of the present invention, under varying temperature and / or stress conditions, the solidified polymer deforms, causing the connecting channels to deform, and the continuous phase structure formed by the liquid metal also deforms synchronously.

[0008] According to an embodiment of the present invention, the dual continuous phase network structure is as follows Figure 2 shown.

[0009] According to an embodiment of the present invention, the liquid metal is selected from at least one or two or more of gallium, a gallium-indium eutectic alloy, a gallium-indium-tin alloy, a bismuth-tin alloy, and a bismuth-tin-lead-indium alloy. Exemplarily, the liquid metal is a gallium-indium eutectic alloy, with a mass ratio of gallium to indium of 3:1.

[0010] According to an embodiment of the present invention, the raw material of the solidified polymer includes a flexible polymer, and optionally includes or excludes a high molecular compound.

[0011] According to an embodiment of the present invention, the polymer compound is selected from at least one or two or more of polyurethane, polyvinyl alcohol, polysiloxane, and polyoxyethylene.

[0012] According to an embodiment of the present invention, the flexible polymer is selected from at least one of polyurethane polymers, polyborosiloxane polymers, polysilazane polymers, and polysiloxane polymers.

[0013] Preferably, the polyurethane polymer is selected from at least one of polyester polyurethane, polyether polyurethane, polycaprolactone polyurethane, polycarbonate polyurethane, etc. Exemplarily, the polyurethane polymer is polybutylene adipate-diphenylmethane diisocyanate-1,4-butanediol.

[0014] Preferably, the polyborosiloxane polymer is at least one selected from polyphenylborosiloxane, cross-linked poly[methyl(boroxy)siloxane-co-dimethylsiloxane], and the like.

[0015] Preferably, the polysiloxane polymer is at least one selected from polydimethylsiloxane, polymethylphenylsiloxane, and polycyanosiloxane.

[0016] According to an embodiment of the present invention, the polymer compound and the flexible polymer may be the same or different, which is not specifically limited in the present invention.

[0017] According to an embodiment of the present invention, the mass ratio of liquid metal to flexible polymer is 1-15:0.1-5, for example, 10:1.

[0018] According to an embodiment of the present invention, the mass ratio of the liquid metal to the polymer compound is 1-10:0-1, for example, 1:1 or 1:0.

[0019] According to an embodiment of the present invention, under elevated temperature and / or stress conditions, the relative resistance change rate of the conductive composite material is no more than 10%.

[0020] According to an embodiment of the present invention, under a temperature reduction condition, the relative resistance change rate of the conductive composite material is no more than 80%.

[0021] According to an exemplary embodiment of the present invention, under elevated temperature conditions (temperature range is 323K-523K), the relative resistance change rate of the conductive composite material is no more than 8%, for example, 3%.

[0022] According to an exemplary embodiment of the present invention, when the tensile strain is 170%, the relative resistance change rate of the conductive composite material is no more than 1.3%; when the compressive strain is 50%, the relative resistance change rate of the conductive composite material is no more than 0.3%.

[0023] The present invention also provides a method for preparing the conductive composite material, the method comprising:

[0024] S1) The method for preparing the liquid metal-flexible polymer precursor is selected from method 1 or method 2:

[0025] Method 1: A polymer compound is dissolved in a solvent, and then liquid metal is added. The liquid metal is dispersed by physical methods to prepare a liquid metal dispersion. Liquid metal particles are obtained by centrifugation and filtration. The liquid metal particles are coated with a polymer compound. The liquid metal particles are added to a flexible polymer and mixed to obtain a liquid metal-flexible polymer precursor.

[0026] Method 2: Add liquid metal to flexible polymer and mix well to obtain liquid metal-flexible polymer precursor;

[0027] S2) curing the liquid metal-flexible polymer precursor to obtain a liquid metal / polymer composite material;

[0028] S3) activating the liquid metal / polymer composite material of step S2) using mechanical force to obtain the conductive composite material.

[0029] According to an embodiment of the present invention, in S1), the polymer compound is selected from at least one or two or more of polyurethane, polyvinyl alcohol, polysiloxane, and polyoxyethylene.

[0030] According to an embodiment of the present invention, in S1), the solvent is selected from at least one of deionized water, ethanol, acetone, tetrahydrofuran, n-hexane, and ethyl acetate.

[0031] According to an embodiment of the present invention, in S1), the usage ratio of the polymer compound and the solvent is not particularly limited, as long as the polymer compound can be dissolved.

[0032] According to an embodiment of the present invention, in S1), the mass ratio of the polymer compound to the liquid metal is 1:10 to 50, for example, 1:20, 1:30, or 1:40.

[0033] According to an embodiment of the present invention, in S1), the liquid metal is selected from at least one or two or more of gallium, a gallium-indium eutectic alloy, a gallium-indium-tin alloy, a bismuth-tin alloy, and a bismuth-tin-lead-indium alloy. Exemplarily, the liquid metal is a gallium-indium eutectic alloy, with a mass ratio of gallium to indium of 3:1.

[0034] According to an embodiment of the present invention, in S1), the physical method is selected from at least one of shear dispersion, splashing, injection, and ultrasonic dispersion.

[0035] According to the embodiment of the present invention, in S1), in method one, the liquid metal is wrapped by the polymer compound during dispersion to form liquid metal particles, thereby improving the compatibility of the liquid metal particles in the matrix (such as a flexible polymer), and can greatly shorten the dispersion time when mixing in the flexible polymer.

[0036] According to an embodiment of the present invention, in S1), the liquid metal particles may also be cleaned using methods known in the art, such as using alcohol for cleaning.

[0037] According to an embodiment of the present invention, the size of the liquid metal particles is 1-100 μm, for example, 15 μm.

[0038] According to an embodiment of the present invention, in S1), the flexible polymer is provided by a solution of a flexible polymer, wherein the solution of the flexible polymer comprises a flexible polymer and a solvent, and the solvent has the meaning as described above.

[0039] According to an embodiment of the present invention, the flexible polymer is selected from at least one of polyurethane polymers, polyborosiloxane polymers, polysilazane polymers, and polysiloxane polymers.

[0040] Preferably, the polyurethane polymer is selected from at least one of polyester polyurethane, polyether polyurethane, polycaprolactone polyurethane, polycarbonate polyurethane, etc. Exemplarily, the polyurethane polymer is polybutylene adipate-diphenylmethane diisocyanate-1,4-butanediol.

[0041] Preferably, the polyborosiloxane polymer is at least one selected from polyphenylborosiloxane, cross-linked poly[methyl(boroxy)siloxane-co-dimethylsiloxane], and the like.

[0042] Preferably, the polysiloxane polymer is at least one selected from polydimethylsiloxane, polymethylphenylsiloxane, and polycyanosiloxane.

[0043] According to an embodiment of the present invention, in S1), the mass ratio of the liquid metal to the flexible polymer is 1-15:0.1-5, for example, 10:1.

[0044] According to an embodiment of the present invention, in S1), in method 1, the mass ratio of liquid metal to polymer compound is 1-10:1, for example, 1:1.

[0045] According to an embodiment of the present invention, in S1), in method 1, the polymer compound and the flexible polymer may be the same or different, and are not specifically limited in the present invention.

[0046] According to an embodiment of the present invention, in S1), in method 1, the mixing and dispersion time is 1-30 minutes, for example, 20 minutes.

[0047] According to an embodiment of the present invention, in S1), in method 2, the mixing and dispersion time is 1-3 hours, for example, 2 hours.

[0048] According to an embodiment of the present invention, in S2), the curing and forming specifically includes: placing the liquid metal-flexible polymer precursor in a container, removing bubbles and solvents under low pressure, then covering the surface of the liquid metal-flexible polymer precursor with a polymer film, and curing and forming at a certain temperature.

[0049] Preferably, the container is selected from a forming mold or a flat plate known in the art.

[0050] Preferably, the polymer film is at least one selected from polytetrafluoroethylene film, polyimide film, and poly(p-phenylene benzobisoxazole) film.

[0051] Preferably, the curing temperature is 25-150°C, for example, 50°C or 100°C.

[0052] Preferably, the low pressure is 10 -1 ~10 -5 Pa, for example, 10 -2 Pa, 10 -3 Pa, 10 -4 Pa.

[0053] According to an embodiment of the present invention, in S3), the mechanical force activation is mechanical pressure activation, which specifically includes the following steps:

[0054] S301 , extruding the liquid metal / polymer composite material obtained in step S2) under a pressure of 0.1 to 5 MPa; after extrusion, obtaining the conductive composite material.

[0055] Preferably, in step S301 , the liquid metal / polymer composite material may be optionally cut into appropriate sizes known in the art before being extruded.

[0056] Preferably, in step S301 , the extrusion can be performed using a device known in the art, such as under a pressure plate.

[0057] Preferably, in step S301 , extrusion may be performed under a condition of covering with a polymer film, and then the polymer film may be peeled off.

[0058] The inventors discovered that when solidified at a certain temperature, the flexible polymer forms a solidified polymer, with the liquid metal distributed within the solidified polymer. Under mechanical activation, the liquid metal interconnects and forms a continuous phase structure within the polymer, thereby forming a polymer / liquid metal bicontinuous phase network structure. Because the conductive composite material of the present invention has a bicontinuous phase network structure, even if the solidified polymer deforms under varying temperatures and / or stress conditions, the liquid metal can automatically fill the deformed interconnecting channels, thereby forming a bicontinuous phase network structure with solid-liquid synergistic deformation, thereby maintaining stable electrical conductivity in the conductive composite material of the present invention.

[0059] The present invention also provides applications of the conductive composite material in the field of conductors, such as stretchable conductors, stretchable electromagnetic shielding materials, and high and low temperature electromagnetic shielding materials. Preferably, the stretchable conductor comprises the conductive composite material.

[0060] The present invention has the following beneficial effects:

[0061] By designing a liquid metal / flexible polymer bicontinuous phase, this invention produces a conductive composite material that is both insensitive to temperature fluctuations and deformation. This conductive composite material exhibits remarkable conductive stability under wide temperature variations and various mechanical deformations. This invention opens up new possibilities for the multifunctional application of flexible conductive composite materials in extremely complex environments. Specifically:

[0062] (1) The present invention uses mechanical pressure to construct a dual-continuous phase network of flexible polymer / liquid metal. After the liquid metal is connected, the liquid metal forms a highly tortuous continuous phase structure. At the same time, the liquid metal / polymer composite material forms a structure similar to a communicating vessel. The deformation of the matrix around the liquid metal is similar to the change in the shape of the container of the communicating vessel. In order to balance the pressure at each point, the liquid metal will automatically fill the gaps at the interface to form a new shape of the path, stably maintaining the conductive network. This adaptive interface reconstruction behavior effectively ensures the topological continuity of the conductive path of the composite material, thereby maintaining good conductivity under various deformations such as stretching, compression, bending, and twisting. When the tensile strain is 170%, the relative resistance change rate is only 1.3%.

[0063] (2) The isotropic volume expansion behavior of the polymer when heated produces a more complex strain distribution in three-dimensional space. The isotropic volume expansion of the matrix surrounding the liquid metal is similar to the vertical container of a communicating vessel becoming deeper and wider, but the liquid metal can automatically fill the newly created space. This solid-liquid cooperative deformation mechanism can enable the liquid metal / polymer to maintain stable conductivity in a high-temperature environment. At a temperature of 510K, the relative resistance change rate is only 8%.

[0064] (3) In a low-temperature environment, when the temperature drops to the supercooling temperature of the liquid metal, the liquid metal undergoes a phase change, solidifies, and expands, contacting adjacent liquid metals to form more conductive pathways, compensating for the damaged conductive network. At the same time, the lattice vibration of the liquid metal weakens as the temperature drops, and electron scattering decreases, resulting in a decrease in the intrinsic resistance of the liquid metal. These two factors together compensate for the damage to the percolation network caused by low temperature, allowing the liquid metal / polymer to maintain stable conductivity in a low-temperature environment.

[0065] (4) The present invention proposes to use a liquid metal / polymer dual-continuous phase network to realize a flexible conductive polymer that is doubly insensitive to deformation and temperature, opening up a design idea for multifunctional conductive polymers used in complex and extreme environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] Figure 1 This is the element distribution result of the liquid metal prepared in Example 1 of the present invention after being dispersed in a polydimethylsiloxane solution.

[0067] Figure 2 This is a scanning electron microscope image of the liquid metal / polymer composite material prepared in Example 1 of the present invention.

[0068] Figure 3 This is a curve showing the relationship between the resistance change rate and the tensile strain of the liquid metal / polymer composite material prepared in Example 1 of the present invention during uniaxial stretching.

[0069] Figure 4This is a curve showing the relationship between the resistance change rate and the tensile strain of the liquid metal / polymer composite material prepared in Example 1 of the present invention during compression.

[0070] Figure 5 This is a resistance change rate-time curve of the liquid metal / polymer composite material prepared in Example 1 of the present invention during a complete bending process.

[0071] Figure 6 This is a resistance change rate-time curve of the liquid metal / polymer composite material prepared in Example 1 of the present invention during the complete twisting process.

[0072] Figure 7 This is a resistance change rate-temperature relationship curve of the liquid metal / polymer composite material prepared in Example 2 of the present invention during the heating process.

[0073] Figure 8 This is a resistance change rate-temperature relationship curve of the liquid metal / polymer composite material prepared in Example 3 of the present invention during the cooling process. DETAILED DESCRIPTION

[0074] The technical solutions of the present invention will be described in further detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanations of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are encompassed within the scope of protection that the present invention is intended to protect.

[0075] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0076] Example 1:

[0077] Preparation of conductive composite materials:

[0078] S1) Preparation of a liquid metal-flexible polymer precursor: 3g of polydimethylsiloxane was dissolved in 30ml of n-hexane solvent and stirred thoroughly, followed by the addition of 5g of liquid metal, wherein the liquid metal was a gallium-indium eutectic alloy with a gallium to indium mass ratio of 3:1. The liquid metal was dispersed by shear dispersion to obtain a liquid metal dispersion; the mixture was centrifuged, the supernatant was removed, and the mixture was washed with alcohol and filtered to obtain liquid metal particles; the liquid metal particles were added to a flexible polymer solution (specifically, liquid polydimethylsiloxane (PDMS) and n-hexane solvent in a mass ratio of 1:5) with a liquid metal to PDMS mass ratio of 10:1, and the mixture was stirred thoroughly and mixed for 20 minutes to obtain a liquid metal-flexible polymer precursor.

[0079] S2) placing the liquid metal-flexible polymer precursor in a PTFE mold and -1The bubbles and solvent are removed under a low pressure of Pa, a polymer film (the polymer film is a polytetrafluoroethylene film) is attached to the uppermost layer of the mixture, and the mixture is cured and formed at 130°C; after demolding, a liquid metal / polymer composite material is obtained.

[0080] S3) Activating the liquid metal / polymer composite material: Activating the liquid metal / polymer composite material obtained in S3 using mechanical force to obtain a flexible, highly conductive elastomer material that is insensitive to both strain and temperature changes;

[0081] The mechanical force activation method in S3 is mechanical pressure activation, which specifically includes the following steps:

[0082] S301 , cutting the liquid metal / polymer composite material with the polymer film obtained in S2 into a suitable size.

[0083] S302 , placing the cut liquid metal / polymer composite material with the polymer film under a pressure plate, and pressing the material downward with a pressure of 0.7 MPa.

[0084] S303, after pressing down, the liquid metal particles inside the material are interconnected, see Figure 2 The size of the liquid metal particles is about 15 μm. Subsequently, the attached polymer film is peeled off to obtain a flexible and highly conductive elastomer material, which is a liquid metal / polymer conductive composite material.

[0085] Deformation test:

[0086] The two ends of the liquid metal / polymer conductive composite obtained in step S3) were connected to a digital source meter (KEITHLEY 2440, Keithley Instruments, Inc., USA) and a texture analyzer (TA-XTC-20, Shanghai Baosheng Industrial Development Co., Ltd.) were used to measure the resistance change rate of the liquid metal / polymer conductive composite under uniaxial tension and compression. When the tensile strain was 170%, the resistance change rate of the liquid metal / polymer conductive composite was 1.3%, and when the compressive strain was 50%, the resistance change rate of the liquid metal / polymer conductive composite was 0.3%. For details, see Figure 3 、 Figure 4 .

[0087] In combination with a digital source meter, the resistance change rate of the material under bending and twisting is measured. The resistance change rate of the liquid metal / polymer conductive composite material fluctuates within a very small range. Figure 5 、 Figure 6 .

[0088] Example 2:

[0089] The preparation steps of the liquid metal / polymer conductive composite material of this embodiment are basically the same as those of Example 1, except that the flexible polymer solution used is a polyurethane solution, specifically including polybutylene adipate-diphenylmethane diisocyanate-1,4-butanediol and ethyl acetate solvent.

[0090] Temperature test:

[0091] The liquid metal / polymer conductive composite material obtained above was placed on a hot stage, and the temperature change of the material was measured using a thermal imager (FOTRIC228S-M50-B3s, Shanghai Thermal Imaging Technology Co., Ltd.). The two ends of the liquid metal / polymer conductive composite material were connected to a digital source meter to measure the resistance change rate of the material during the heating process (temperature change range 323K-523K). Figure 7 .

[0092] Example 3:

[0093] The preparation steps of the liquid metal / polymer conductive composite material of this embodiment are basically the same as those of Example 1, except that the flexible polymer solution used is a polyborosiloxane solution, specifically including cross-linked poly[methyl(boroxy)siloxane-co-dimethylsiloxane] and ethyl acetate solvent.

[0094] Cooling test:

[0095] The liquid metal / polymer conductive composite material obtained above was combined with a physical property measurement system (PPMS) (QuantumDesign PPMS-9) to measure the resistance change rate of the material during the cooling process (temperature change range 100K-300K). For details, see Figure 7 .

[0096] Example 4

[0097] The preparation steps of the liquid metal / polymer conductive composite material of this embodiment are basically the same as those of Example 1, except that: in step S1), no polymer compound is added, and liquid metal particles are directly added to the flexible polymer solution and mixed and dispersed to obtain a liquid metal-flexible polymer precursor. The dispersion time is specifically 2 hours.

[0098] Comparative Example 1

[0099] The preparation steps of the liquid metal / polymer conductive composite material of this comparative example are basically the same as those of Example 1, except that no polymer film is used in step S2).

[0100] Deformation tests were performed on the materials of Example 4 and Comparative Example 1 with reference to Examples 1-3, and the test results are as follows: when the tensile strain is 150%, the resistance change rate of the liquid metal / polymer conductive composite material of Example 4 is 1.3%; when the tensile strain is 150%, the resistance change rate of the liquid metal / polymer conductive composite material is 10.2%.

[0101] The test results above demonstrate that the resistance change rate of the liquid metal / polymer conductive composite material prepared by the present invention under deformation conditions is less than 1.3%; under elevated temperature conditions, the resistance change rate is less than 8%; and under reduced temperature conditions, the resistance change rate is less than 80%. In contrast, when no polymer film is used, the resistance change rate of the prepared material under deformation conditions is 10.2%. This demonstrates that the conductive properties of the liquid metal / polymer conductive composite material prepared by the present invention are minimally affected by deformation or temperature fluctuations, indicating dual insensitivity to strain and temperature changes.

[0102] In addition, it can be seen from Examples 1 and 4 that, during the preparation process, when a polymer compound is added, the dispersion time for preparing the liquid metal-flexible polymer precursor can be greatly shortened; when the polymer compound is not added and the liquid metal is directly dispersed in the flexible polymer solution, the performance of the liquid metal / polymer conductive composite material finally obtained is basically the same.

[0103] The above describes exemplary embodiments of the present invention. However, the scope of protection of this application is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc. made by those skilled in the art within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A conductive composite material, characterized in that The conductive composite material includes: liquid metal and solidified polymer; the liquid metal is distributed in the solidified polymer to form a connecting channel in the solidified polymer, and the liquid metal forms a continuous phase structure in the polymer, thereby forming a polymer / liquid metal dual-continuous phase network structure.

2. The conductive composite material according to claim 1, wherein Under varying temperature and / or stress conditions, the solidified polymer deforms, causing the connecting channels to deform, and the continuous phase structure formed by the liquid metal also deforms synchronously; According to an embodiment of the present invention, the liquid metal is selected from at least one or two or more of gallium, gallium-indium eutectic alloy, gallium-indium-tin alloy, bismuth-tin alloy, and bismuth-tin-lead-indium alloy; The raw material of the solidified polymer includes a flexible polymer, and optionally includes or excludes a high molecular compound; The polymer compound is selected from at least one or two or more of polyurethane, polyvinyl alcohol, polysiloxane, and polyoxyethylene; The flexible polymer is selected from at least one of polyurethane polymers, polyborosiloxane polymers, polysilazane polymers, and polysiloxane polymers.

3. The conductive composite material according to claim 1 or 2, characterized in that: The mass ratio of liquid metal to flexible polymer is 1-15:0.1-5; The mass ratio of liquid metal to polymer compound is 1-10:0-1; Under elevated temperature and / or stress conditions, the relative resistance change rate of the conductive composite material is no more than 10%; Under cooling conditions, the relative resistance change rate of the conductive composite material is no more than 80%.

4. The method for preparing the conductive composite material according to any one of claims 1 to 3, characterized in that: The preparation method comprises: S1) The method for preparing the liquid metal-flexible polymer precursor is selected from method 1 or method 2: Method 1: A polymer compound is dissolved in a solvent, and then liquid metal is added. The liquid metal is dispersed by physical methods to prepare a liquid metal dispersion. Liquid metal particles are obtained by centrifugation and filtration. The liquid metal particles are coated with a polymer compound. The liquid metal particles are added to a flexible polymer and mixed to obtain a liquid metal-flexible polymer precursor. Method 2: Add liquid metal to flexible polymer and mix well to obtain liquid metal-flexible polymer precursor; S2) curing the liquid metal-flexible polymer precursor to obtain a liquid metal / polymer composite material; S3) activating the liquid metal / polymer composite material of step S2) using mechanical force to obtain the conductive composite material.

5. The preparation method according to claim 4, characterized in that In S1), the polymer compound is selected from at least one or two or more of polyurethane, polyvinyl alcohol, polysiloxane, and polyoxyethylene; S1), wherein the solvent is selected from at least one of deionized water, ethanol, acetone, tetrahydrofuran, n-hexane, and ethyl acetate; S1), the mass ratio of the polymer compound to the liquid metal is 1:10 to 50; In S1), the liquid metal is selected from at least one or two or more of gallium, gallium-indium eutectic alloy, gallium-indium-tin alloy, bismuth-tin alloy, and bismuth-tin-lead-indium alloy.

6. The preparation method according to claim 4 or 5, characterized in that In S1), the physical method is selected from at least one of shear dispersion, splashing, injection, and ultrasonic dispersion; The size of the liquid metal particles is 1-100 μm; According to an embodiment of the present invention, in S1), the flexible polymer is provided by a solution of a flexible polymer, and the solution of the flexible polymer comprises a flexible polymer and a solvent; The flexible polymer is selected from at least one of polyurethane polymers, polyborosiloxane polymers, polysilazane polymers, and polysiloxane polymers.

7. The preparation method according to any one of claims 4 to 6, characterized in that In S1), the mass ratio of the liquid metal to the flexible polymer is 1-15:0.1-5; S1), in method 1, the mass ratio of liquid metal to polymer compound is 1-10:1; In S1), in method 1, the mixing and dispersing time is 1-30 minutes; in method 2, the mixing and dispersing time is 1-3 hours.

8. The preparation method according to claim 4, characterized in that In S2), the curing and forming specifically includes: placing the liquid metal-flexible polymer precursor in a container, removing bubbles and solvents under low pressure, then covering the surface of the liquid metal-flexible polymer precursor with a polymer film, and curing and forming at a certain temperature; The polymer film is selected from at least one of a polytetrafluoroethylene film, a polyimide film, and a poly(p-phenylene benzobisoxazole) film; The curing temperature is 25-150°C; The low pressure refers to 10 -1 ~10 -5 Pa.

9. The preparation method according to claim 4, characterized in that In S3), the mechanical force activation is mechanical pressure activation, which specifically includes the following steps: S301 , extruding the liquid metal / polymer composite material obtained in step S2) under a pressure of 0.1 to 5 MPa; after extrusion, obtaining the conductive composite material.

10. Use of the conductive composite material according to any one of claims 1 to 3 in the field of conductors.

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