Gallium-based liquid metal conductive paste with strain insensitive characteristic as well as preparation method and application of gallium-based liquid metal conductive paste

Abstract

The invention provides gallium-based liquid metal conductive paste with a strain insensitive characteristic and a preparation method and application thereof, and belongs to the technical field of electronic circuits. The gallium-based liquid metal conductive paste is prepared by mixing inorganic particles containing lone pair electrons with liquid metal, enabling the inorganic particles and the liquid metal to generate mechanochemical action under strong shearing force, and the paste is in a liquid state, a semi-solid paste state or a solid powder state with low surface tension according to different adding proportions of the inorganic particles. According to the invention, the conductive slurry is applied to various substrates through different processes, and strain-insensitive stretchable conductors with stretchability and high conductivity, such as liquid metal sheath core microfibers and liquid metal ion gel, are prepared. According to the invention, the tensile conductor prepared by adopting the gallium-based liquid metal conductive paste has the resistance change rate change of less than 15% under 200% strain, and the initial resistance is less than 1 ohm.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic circuits, and particularly to a gallium-based liquid metal conductive paste with strain-insensitive characteristics, a preparation method thereof, and an application thereof. Background Art

[0002] With the rapid development of intelligent electronics, the market demand for flexible conductors has increased rapidly. Non-stretchable conductors can no longer meet the needs of intelligent electronics, while stretchable conductors, due to their good stretching properties, can be applied to more special scenarios and have high application value. Liquid metals have extremely high electrical conductivity (for example, the electrical conductivity of gallium-indium alloy EGaIn is 3.4×106 S / m), good environmental adaptability, low melting point, and non-toxicity, and have the potential to prepare stretchable conductive materials.

[0003] However, in the prior art, the resistance of stretchable conductors prepared by ordinary processes will increase rapidly during stretching, causing the stretchable conductors to lose their conductive ability. How to prepare a strain-insensitive stretchable conductor with both stretchability and high conductivity is one of the current key research directions. Some researchers use the oxides on the surface of liquid metals for patterned printing to prepare stretchable conductor materials. However, liquid metals have high surface tension and fluidity, and it is difficult to maintain a given shape without structural support. For this technical problem, a common solution strategy is to encapsulate liquid metals in the hollow pipes of elastomers. For example, some researchers have fabricated composite fibers with good conductivity in the stretched state by injecting liquid metals into thermoplastic elastomers. However, the electrical conductivity of the conductive fibers prepared by this process still decreases with the increase of the stretching degree (in line with Ohm's law), and there is a risk of liquid metal leakage.

[0004] In view of this, it is necessary to design a gallium-based liquid metal conductive paste with strain-insensitive characteristics, a preparation method thereof, and an application thereof to solve the above problems. Summary of the Invention

[0005] In view of the technical problems existing in the background art, the present application provides a gallium-based liquid metal conductive paste with strain-insensitive characteristics, a preparation method thereof, and an application thereof, aiming to solve the technical problems that liquid metals are difficult to maintain a given shape without structural support, resulting in the electrical conductivity of strain-insensitive conductors prepared using liquid metals still decreasing with the increase of the stretching degree, and there is a risk of liquid metal leakage.

[0006] In a first aspect, an embodiment of the present application provides a gallium-based liquid metal conductive paste with strain-insensitive properties, wherein the gallium-based liquid metal conductive paste is an alloy composite material formed by inorganic particles containing lone pairs of electrons and liquid metal under mechanochemical action, wherein the mass proportion of the inorganic particles containing lone pairs of electrons is 5-33%, and the mass proportion of the liquid metal is 75-95%; in the gallium-based liquid metal conductive paste, the lone electron pairs of the inorganic particles containing lone pairs of electrons form a coordination bond with the empty orbitals of the liquid metal; the morphology of the gallium-based liquid metal conductive paste presents a liquid, semi-solid paste or solid powder with low surface tension depending on the proportion of inorganic particles added; the gallium-based liquid metal conductive paste has strain-insensitive properties, and the resistance change rate of the stretchable conductor prepared using the gallium-based liquid metal conductive paste under 200% strain is less than 15%, and the initial resistance is less than 1Ω.

[0007] Furthermore, the inorganic particles containing lone pair electrons are one or more of SiO2, Al2O3, TiO2, Fe3O4, aluminum nitride, and boron nitride.

[0008] Furthermore, the particle size of the inorganic particles containing lone pair electrons is 20-500 nm.

[0009] Furthermore, the liquid metal is a gallium-indium alloy or a gallium-indium-tin alloy, wherein the mass proportions of gallium, indium and tin are 62-95%, 5-22% and 0-16% respectively.

[0010] On the second aspect, the embodiments of the present application provide a method for preparing a gallium-based liquid metal conductive paste with strain-insensitive properties, wherein a strong shear force is applied to inorganic particles containing lone pairs of electrons and liquid metal using a mortar or a ball mill, so that a violent mechanochemical reaction occurs between the inorganic particles and the liquid metal, thereby forming a coordination bond between the lone electron pairs of the inorganic particles and the empty orbitals of the liquid metal, thereby obtaining a uniform liquid, semi-solid paste or solid powder gallium-based liquid metal conductive paste.

[0011] In the third aspect, an embodiment of the present application provides an application of a gallium-based liquid metal conductive paste with strain-insensitive properties, and the application refers to the preparation of a stretchable conductor using the gallium-based liquid metal conductive paste, specifically including scraping or printing the gallium-based liquid metal conductive paste on an electrospun elastic fiber mat, coating the gallium-based liquid metal conductive paste on the surface of a fiber or an ion gel, printing or printing the gallium-based liquid metal conductive paste on the surface of an elastomer, and using the gallium-based liquid metal conductive paste to continuously manufacture liquid metal sheath-core microfibers through a coaxial wet spinning process.

[0012] Further, in the application of continuously manufacturing liquid metal sheath-core microfibers by using the gallium-based liquid metal conductive paste through a coaxial wet spinning process, the preparation method of the liquid metal sheath-core microfibers comprises the following steps:

[0013] S1. Mix inorganic particles with lone pair electrons and liquid metal, and strongly grind them with an agate mortar at room temperature for 30 - 50 min to prepare a solid or semi-solid paste that is not easily flowable and has stable electrical conductivity, namely the gallium-based liquid metal conductive paste, which is used as the core layer paste;

[0014] S2. Add a polymer to a solvent, and magnetically stir it at room temperature until the polymer is completely dissolved to obtain a uniform and transparent sheath layer spinning solution;

[0015] S3. Inject the core layer paste and the sheath layer spinning solution prepared in steps S1 - S2 into syringes respectively, and perform coaxial wet spinning with a coaxial spinneret. The spun fibers are immersed in a coagulation bath;

[0016] S4. Take out the fibers spun in step S3 from the coagulation bath, and place them in a vacuum oven at 35 - 45 °C for drying for 10 - 20 min to obtain liquid metal sheath-core microfibers, namely a stretchable conductor with strain-insensitive characteristics.

[0017] Further, in step S1, the inorganic particles with lone pair electrons account for 5 - 33% of the mass of the gallium-based liquid metal conductive paste.

[0018] Further, in step S2, the polymer is thermoplastic polyurethane elastomer, styrene-butadiene-styrene block copolymer or linear triblock copolymer, the solvent is deionized water, N,N-dimethylformamide, tetrahydrofuran, dimethyl sulfoxide, isopropanol, sodium sulfate, toluene, dichloromethane, chloroform or ethanol, and the concentration of the sheath layer spinning solution is 10 - 50%.

[0019] Further, in step S3, the coagulation bath is composed of one or several of deionized water, ethanol, N,N-dimethylformamide, tetrahydrofuran, isopropanol, toluene, dichloromethane, chloroform, dimethyl sulfoxide and sodium sulfate.

[0020] The beneficial effects of this application are as follows:

[0021] The present invention provides a gallium-based liquid metal conductive paste with strain-insensitive characteristics, a preparation method thereof, and an application thereof. By mixing inorganic particles containing lone pair electrons with liquid metal under strong shear force, a liquid, semi-solid or solid paste with low surface tension is formed, that is, a gallium-based liquid metal conductive paste. By applying this paste to various substrates through different process technologies, a strain-insensitive stretchable conductor with both stretchability and high conductivity is prepared. For example, the gallium-based liquid metal conductive paste is scrape-coated or printed on an electrospun elastic fiber mat, the gallium-based liquid metal conductive paste is coated on the fiber surface, the gallium-based liquid metal conductive paste is printed or printed on the elastomer surface, and a liquid metal sheath-core microfiber is continuously manufactured by a coaxial wet spinning process using the gallium-based liquid metal conductive paste.

[0022] In the gallium-based liquid metal conductive paste provided in this application, the introduction of inorganic particles significantly enhances the overall stability of the composite material, moderately increases the overall resistance of the material, and promotes the formation of a porous conductive network embedded with nanoparticles inside the material to avoid drastic fluctuations in resistivity caused by too small resistance or cross-sectional area changes, so that the material can still maintain a stable resistance change under high stretching and cyclic stretching conditions.

[0023] The gallium-based liquid metal conductive paste prepared in this application has strain-insensitive characteristics and a resistance less than 1 Ω. The stretchable conductor prepared using the gallium-based liquid metal conductive paste has a resistance change rate change of less than 15% under 200% strain, and has excellent resistance stability, providing an innovative technical solution for manufacturing strain-insensitive conductive materials.

[0024] The above description is only an overview of the technical solution of this application. In order to be able to understand the technical means of this application more clearly, it can be implemented according to the content of the specification. And in order to make the above and other purposes, features and advantages of this application more obvious and understandable, the specific embodiments of this application are specifically given below. Description of the Drawings

[0025] In order to more clearly illustrate the technical solution of this application, the drawings used in this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0026] Figure 1 It is a scanning electron microscope (SEM) image of the gallium-based liquid metal conductive paste provided in Embodiment 1 of the present invention;

[0027] Figure 2 It is a combined image of the O, Al, and Ga energy-dispersive element spectrogram (EDS) and the physical image of the gallium-based liquid metal conductive paste provided in Embodiment 1 of the present invention.

[0028] Figure 3 SEM image of the liquid metal sheath-core microfiber provided in Embodiment 4 of the present invention;

[0029] Figure 4 Cross-sectional SEM image of the liquid metal sheath-core microfiber provided in Embodiment 4 of the present invention;

[0030] Figure 5 Cross-sectional SEM image of the liquid metal sheath-core microfiber provided in Comparative Example 1 of the present invention;

[0031] Figure 6 Graph of the change rate of resistance of the liquid metal sheath-core microfibers provided in Embodiments 4-6 and Comparative Example 1 of the present invention under different strains and its partial enlarged view;

[0032] Figure 7 Graph of the change rate of resistance of the liquid metal sheath-core microfiber provided in Embodiment 4 of the present invention under repeated cyclic stretching 100 times at 100% and 200% elongation rates;

[0033] Figure 8 Graph of the change rate of resistance of the liquid metal ion gels provided in Embodiment 7 and Comparative Example 2 of the present invention under different elongation rates; Detailed implementation manners

[0034] The embodiments of the technical solutions of the present application will be described in detail below with reference to the accompanying drawings. The following embodiments are only used to illustrate the technical solutions of the present application more clearly, so they are only examples and cannot be used to limit the protection scope of the present application.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "comprising" and "having" and any variations thereof in the specification and claims of this application and the above drawings are intended to cover non-exclusive inclusion.

[0036] In the description of the embodiments of this application, technical terms such as "first" and "second" are only used to distinguish different objects and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity, specific order or primary-secondary relationship of the indicated technical features. In the description of the embodiments of this application, "a plurality of" means more than two unless otherwise specifically defined.

[0037] Reference to "embodiments" in this document means that the specific features, structures, or characteristics described in connection with the embodiments can be included in at least one embodiment of the present application. The phrase appears in various places in the specification and does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0038] In the description of the embodiments of the present application, the term "and / or" is merely a description of the associated relationship of the associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this document generally represents an "or" relationship between the front and rear associated objects.

[0039] Due to its good stretching properties, stretchable conductors can be applied to more special scenarios and have high application value. However, in the prior art, the resistance of stretchable conductors prepared by ordinary processes increases rapidly during stretching, causing the stretchable conductors to lose their conductivity. In addition, during the process of preparing stretchable conductors using liquid metal, since it is difficult for liquid metal to maintain a given shape without structural support, there are also technical problems that the conductivity of the strain-insensitive conductors prepared using liquid metal still decreases as the stretching degree increases, and there is a risk of liquid metal leakage.

[0040] To solve the above technical problems, the present application provides a gallium-based liquid metal conductive paste with strain-insensitive characteristics, its preparation method and application. Among them, by mixing inorganic particles containing lone pair electrons with liquid metal under strong shear force, a liquid, semi-solid or solid paste with low surface tension is formed, that is, a gallium-based liquid metal conductive paste. By applying this paste to various substrates through different process technologies, a strain-insensitive stretchable conductor with both stretchability and high conductivity is prepared.

[0041] In the first aspect, the embodiments of the present application provide a gallium-based liquid metal conductive paste with strain-insensitive characteristics. The gallium-based liquid metal conductive paste is an alloy composite material formed by inorganic particles containing lone pair electrons and liquid metal under mechanochemical action. In the gallium-based liquid metal conductive paste, a coordination bond is formed between the lone pair electrons of the inorganic particles containing lone pair electrons and the empty orbitals of the liquid metal. The gallium-based liquid metal conductive paste has strain-insensitive characteristics. The resistance change rate of the stretchable conductor prepared using this gallium-based liquid metal conductive paste changes by less than 15% under 200% strain, and the initial resistance is less than 1Ω.

[0042] In some embodiments, the inorganic particles containing lone pair electrons are one or more of SiO2, Al2O3, TiO2, Fe3O4, aluminum nitride, and boron nitride, and the mass percentage is 5-33%.

[0043] In some embodiments, the particle size of the inorganic particles containing lone pair electrons is 20-500 nm.

[0044] In some embodiments, the liquid metal is a gallium-indium alloy or a gallium-indium-tin alloy, and the mass percentage is 75-95%. Among them, the mass percentages of the three metals gallium, indium, and tin are 62-95%, 5-22%, and 0-16% respectively.

[0045] In some embodiments, the morphology of the gallium-based liquid metal conductive paste presents a liquid with low surface tension, a semi-solid paste, or a solid powder according to the different proportions of the added inorganic particles. Preferably, when the morphology of the gallium-based liquid metal conductive paste is liquid, the mass percentage of the inorganic particles is 5-8%; when the morphology of the gallium-based liquid metal conductive paste is semi-solid, the mass percentage of the inorganic particles is 8-23%; when the morphology of the gallium-based liquid metal conductive paste is solid, the mass percentage of the inorganic particles is 23-33%.

[0046] In a second aspect, an embodiment of the present application provides a method for preparing a gallium-based liquid metal conductive paste with strain-insensitive characteristics. A mortar or ball mill is used to apply strong shear force to the inorganic particles containing lone pair electrons and the liquid metal, so that a violent mechanochemical action occurs between the inorganic particles and the liquid metal. Furthermore, a coordination bond is formed between the lone electron pairs of the inorganic particles and the empty orbitals of the liquid metal to obtain a uniform liquid, semi-solid paste, or solid powder gallium-based liquid metal conductive paste.

[0047] In a third aspect, an embodiment of the present application provides an application of a gallium-based liquid metal conductive paste with strain-insensitive characteristics, that is, a stretchable conductor is prepared by using the gallium-based liquid metal conductive paste. Specifically, it includes scraping or printing the gallium-based liquid metal conductive paste on an electrospun elastic fiber mat, coating the gallium-based liquid metal conductive paste on the surface of a fiber or an ion gel, printing or printing the gallium-based liquid metal conductive paste on the surface of an elastomer, and continuously manufacturing liquid metal sheath-core microfibers by using the gallium-based liquid metal conductive paste through a coaxial wet spinning process.

[0048] In some embodiments, in the application of continuously manufacturing liquid metal sheath-core microfibers by using the gallium-based liquid metal conductive paste through a coaxial wet spinning process, the preparation method of the liquid metal sheath-core microfibers includes the following steps:

[0049] S1. Mix inorganic particles with lone pair electrons and liquid metal, and strongly grind them in an agate mortar at room temperature for 30 - 50 min to prepare a solid or semi-solid slurry that is not easily flowable and has stable electrical conductivity, namely gallium-based liquid metal conductive slurry, which is used as the core layer slurry. Among them, the inorganic particles with lone pair electrons account for 5 - 33% of the mass of the gallium-based liquid metal conductive slurry.

[0050] S2. Add the polymer to the solvent and stir magnetically at room temperature until the polymer is completely dissolved to obtain a homogeneous and transparent sheath spinning solution. Among them, the polymer is thermoplastic polyurethane elastomer, styrene-butadiene-styrene block copolymer or linear triblock copolymer, the solvent is deionized water, N,N-dimethylformamide, tetrahydrofuran, dimethyl sulfoxide, isopropanol, sodium sulfate, toluene, dichloromethane, chloroform or ethanol, and the concentration of the sheath spinning solution is 10 - 50%.

[0051] S3. Inject the core layer slurry and the sheath spinning solution prepared in steps S1 - S2 into syringes respectively, and perform coaxial wet spinning with a coaxial spinneret. The spun fibers are immersed in a coagulation bath. Among them, the coagulation bath is composed of one or several of deionized water, ethanol, N,N-dimethylformamide, tetrahydrofuran, isopropanol, toluene, dichloromethane, chloroform, dimethyl sulfoxide and sodium sulfate.

[0052] S4. Take out the fibers spun in step S3 from the coagulation bath and place them in a vacuum oven at 35 - 45 °C for drying for 10 - 20 min to obtain liquid metal sheath-core microfibers, namely a stretchable conductor with strain-insensitive characteristics.

[0053] Some specific embodiments are listed below. It should be noted that the embodiments described below are exemplary and are only used to explain the present application, and should not be construed as a limitation to the present application. For those not specified in the embodiments, the techniques or conditions described in the literature in the field or according to the product instructions are followed. For reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0054] Example 1

[0055] Example 1 provides a preparation method of gallium-based liquid metal conductive slurry. Mix Al2O3 with a gallium-indium-tin alloy (the mass ratios of the three metals gallium, indium, and tin are 62%, 22%, and 16% respectively), and then put them into an agate mortar and strongly grind for 40 min to obtain gallium-based liquid metal conductive slurry. Among them, Al2O3 accounts for 16.7% of the mass of the conductive slurry, and the gallium-indium-tin alloy accounts for 82.3% of the mass of the conductive slurry.

[0056] The gallium-based liquid metal conductive paste prepared in Example 1 was characterized using a scanning electron microscope and an energy-dispersive spectrometer (EDS) to observe the mixing morphology of the inorganic particles and the liquid metal. See Figures 1 to 2 as shown. Among them, Figure 1 is the SEM image, Figure 2 and Figure 2 is a combined diagram of the energy-dispersive element spectrograms of O, Al, and Ga and the physical image. It can be seen that the inorganic particles Al2O3 are uniformly mixed in the liquid metal, forming a gallium-based liquid metal conductive paste with a semi-solid paste state of low surface tension.

[0057] Example 2

[0058] Example 2 provides a method for preparing a gallium-based liquid metal conductive paste. SiO2 and a gallium-indium-tin alloy (the mass ratios of the three metals gallium, indium, and tin are 62%, 22%, and 16% respectively) are mixed and then placed in an agate mortar and ground strongly for 40 min to obtain the gallium-based liquid metal conductive paste. Among them, SiO2 accounts for 15% of the mass of the conductive paste, the gallium-indium-tin alloy accounts for 85% of the mass of the conductive paste, and the morphology of the conductive paste is a semi-solid paste with a low surface tension.

[0059] Example 3

[0060] Example 3 provides a method for preparing a gallium-based liquid metal conductive paste. Fe3O4 and a gallium-indium-tin alloy (the mass ratios of the three metals gallium, indium, and tin are 62%, 22%, and 16% respectively) are mixed and then placed in an agate mortar and ground strongly for 40 min to obtain the gallium-based liquid metal conductive paste. Among them, Fe3O4 accounts for 20% of the mass of the conductive paste, the gallium-indium-tin alloy accounts for 80% of the mass of the conductive paste, and the morphology of the conductive paste is a semi-solid paste with a low surface tension.

[0061] Example 4

[0062] Example 4 provides a method for preparing liquid metal sheath-core microfibers prepared with a gallium-based liquid metal conductive paste, including the following steps:

[0063] S1. Al2O3 and a gallium-indium-tin alloy (the mass ratios of the three metals gallium, indium, and tin are 62%, 22%, and 16% respectively) are mixed at a mass ratio of 1:7.5 and ground strongly in an agate mortar at room temperature for 40 min to prepare a gallium-based liquid metal conductive paste as the core layer paste;

[0064] S2. Thermoplastic polyurethane elastomer is added to N,N-dimethylformamide and magnetically stirred at room temperature until the polymer is completely dissolved to obtain a uniform and transparent sheath layer spinning solution with a concentration of 20%;

[0065] S3. Inject the core layer slurry and the sheath layer spinning solution prepared in steps S1 - S2 into syringes respectively, and perform coaxial wet spinning using a coaxial spinneret. Set the flow rates of the outer phase and the inner phase to 10.5 mm / min and 10 mm / min respectively, and soak the spun fibers in deionized water for 0.5 - 24 h;

[0066] S4. Take out the fibers spun in step S3 from deionized water and place them in a vacuum oven at 40°C for drying for 15 min to obtain liquid metal sheath - core microfibers.

[0067] The morphology of the liquid metal sheath - core microfibers prepared in Example 4 was analyzed using a scanning electron microscope, and the SEM image is shown in Figures 3 to 4 As can be seen, the conductive slurry has been successfully injected into the fiber interior.

[0068] Comparative Example 1

[0069] Comparative Example 1 provides a method for preparing liquid metal sheath - core microfibers, which includes the following steps:

[0070] S1. Add thermoplastic polyurethane elastomer to N,N - dimethylformamide, and stir magnetically at room temperature until all the polymers are dissolved to obtain a uniform and transparent sheath layer spinning solution with a concentration of 20%;

[0071] S2. Use gallium - indium - tin alloy (the mass ratios of gallium, indium, and tin are 62%, 22%, and 16% respectively) as the core layer slurry. Inject the core layer slurry and the sheath layer spinning solution into syringes respectively, and perform coaxial wet spinning using a coaxial spinneret. Set the flow rates of the outer phase and the inner phase to 4.5 mm / min and 4 mm / min respectively, and soak the spun fibers in deionized water for 0.5 - 24 h;

[0072] S3. Take out the fibers spun in step S3 from deionized water and place them in a vacuum oven at 40°C for drying for 15 min to obtain liquid metal sheath - core microfibers.

[0073] The liquid metal sheath - core microfibers prepared in Comparative Example 1 were characterized using a scanning electron microscope, as shown in Figure 5 As shown, it is the cross - section SEM image of the liquid metal sheath - core microfibers. It can be seen that when directly using liquid metal as the core layer of the sheath - core microfibers, the structure of the fiber core layer is not stable enough, and a certain degree of leakage occurs.

[0074] Example 5

[0075] Example 5 is different from Example 4 in that the inorganic particles and their proportions used in step S1 are changed, that is, SiO2 and gallium-indium-tin alloy (the mass ratios of gallium, indium, and tin are 62%, 22%, and 16% respectively) are mixed at a mass ratio of 1:5.5, and strongly ground in an agate mortar at room temperature for 40 min to prepare a gallium-based liquid metal conductive paste as the core layer paste. The rest is the same as in Example 4 and will not be elaborated here.

[0076] Example 6

[0077] Example 6 is different from Example 4 in that the inorganic particles and their proportions used in step S1 are changed, that is, Fe3O4 and gallium-indium-tin alloy (the mass ratios of gallium, indium, and tin are 62%, 22%, and 16% respectively) are mixed at a mass ratio of 1:4, and strongly ground in an agate mortar at room temperature for 40 min to prepare a gallium-based liquid metal conductive paste as the core layer paste. The rest is the same as in Example 4 and will not be elaborated here.

[0078] The resistance change rates of the liquid metal sheath-core microfibers prepared in Examples 4-6 and Comparative Example 1 under tensile conditions were tested. Specifically, at room temperature (the tensile rate was fixed at 20 mm / min), conventional tensile tests were carried out on a vertical force gauge (MARK-10, ESM303), and the relationship between the resistance and strain of the liquid metal sheath-core microfibers was measured using an instrument (Keithley, DAQ6510).

[0079] Please refer to Figure 6 , which is the graph of the resistance change rate of the liquid metal sheath-core microfibers prepared in Examples 4-6 and Comparative Example 1 at different tensile rates and its partial enlarged view (the resistance change rate ranges from 0 to 30%, and the strain ranges from 0 to 200%). Among them, the liquid metal sheath-core microfibers prepared in Example 4 correspond to Al2O3 / LM, the liquid metal sheath-core microfibers prepared in Example 5 correspond to SiO2 / LM, the liquid metal sheath-core microfibers prepared in Example 6 correspond to Fe3O4 / LM, and the liquid metal sheath-core microfibers prepared in Comparative Example 1 correspond to Pur LM.

[0080] It can be seen that the resistance change rate of Pur LM increases significantly with the increase of strain during the stretching process, while the resistance change rates of Al2O3 / LM, SiO2 / LM, and Fe3O4 / LM are relatively stable. Among them, the resistance change rates of Al2O3 / LM and SiO2 / LM under 200% strain are both less than 15%, while the resistance change rate of Fe3O4 / LM is relatively large. This is because Fe3O4 itself has certain conductivity. After Fe3O4 is mixed with liquid metal to obtain a conductive paste, the sensitivity of the resistance of the conductive paste to change with strain is higher than that of the conductive paste prepared with the other two inorganic particles. This phenomenon endows the liquid metal sheath-core microfiber with certain magnetic and electromagnetic shielding properties, enabling it to be used in the fields of electromagnetic shielding and anti-interference. For example, it can be used for the flexible shielding layer of mobile phones / laptops to suppress 5G high-frequency signal interference, or for precision instruments in aerospace / military to protect them from electromagnetic pulse (EMP) or radar wave interference and improve the performance of stealth coatings, etc.

[0081] Further test the change diagram of the resistance change rate of Al2O3 / LM under repeated cyclic stretching 100 times at 100% and 200% stretching rates respectively. The test results are shown in Figure 7 As shown, it can be seen that the resistance of Al2O3 / LM remains stable under high-intensity cyclic stretching.

[0082] Example 7

[0083] Example 7 provides an application of printing a gallium-based liquid metal conductive paste on the surface of an elastomer. The specific steps are as follows:

[0084] S1, Mix monomer acrylic acid (AA) and ionic liquid 1-ethyl-3-methylimidazolium diethyl phosphate ([EMIM][DEP]) in a mass ratio of 1:1, add a modifier, a cross-linking agent, and a photoinitiator to obtain a mixed solution, and then cure the mixed solution under irradiation to obtain an ionic liquid gel;

[0085] S2, Mix gallium-indium-tin alloy (the mass ratios of gallium, indium, and tin are 62%, 22%, and 16% respectively) with Al2O3, where Al2O3 accounts for 16.7% of the total mass and the gallium-indium-tin alloy accounts for 82.3% of the total mass to obtain a gallium-based liquid metal conductive paste with printability, adjustable tensile resistance, and high conductivity;

[0086] S3, Using a screen printing template, coat the gallium-based liquid metal conductive paste obtained in step S2 on the ionic liquid gel obtained in step S1 to obtain a conductive layer with a specific pattern and a resolution of 1-10 microns;

[0087] S4. Drop the uncured mixed solution obtained in step S3 onto the conductive coating layer obtained in step S3, so that the solution covers the coating layer. Then, cure and seal the ionic liquid gel covering the conductive trace by irradiation to obtain a liquid metal ionic gel with strain-insensitive performance.

[0088] Comparative Example 2

[0089] Comparative Example 2 provides an application of directly coating a liquid metal on the surface of an ionic gel. The specific steps are as follows:

[0090] S1. Mix monomer acrylic acid (AA) and ionic liquid 1-ethyl-3-methylimidazolium diethyl phosphate ([EMIM][DEP]) in a mass ratio of 1:1, add a modifier, a cross-linking agent and a photoinitiator to obtain a mixed solution. Then, cure the mixed solution under irradiation to obtain an ionic liquid gel.

[0091] S2. Use a screen printing template to directly coat a gallium-indium-tin alloy (the mass percentages of gallium, indium and tin are 62%, 22% and 16% respectively) on the ionic liquid gel obtained in step S1 to obtain a conductive coating layer with a specific pattern and a resolution of 1-10 microns.

[0092] S3. Drop the uncured mixed solution obtained in step S1 onto the conductive coating layer obtained in step S2, so that the solution covers the coating layer. Then, cure and seal the ionic liquid gel covering the conductive trace by irradiation to obtain a liquid metal ionic gel.

[0093] Test the change diagrams of the resistance change rate of the liquid metal ionic gels prepared in Example 7 and Comparative Example 2 under different strains. The test results are shown in Figure 8 As shown. Among them, Example 7 corresponds to Al2O3 / LM, and Comparative Example 2 corresponds to LM. It can be seen that as the strain increases, the resistance change rate of LM increases significantly, while the resistance change rate of Al2O3 / LM changes less and is relatively stable.

[0094] The initial resistances (strain is 0%) of the liquid metal sheath-core microfibers and liquid metal ionic gels provided in Examples 4-7 and Comparative Examples 1-2 are shown in the following table.

[0095] Item Initial resistance (Ω) Example 4 0.73 Example 5 0.60 Example 6 0.45 Comparative Example 1 0.16 Example 7 0.57 Comparative Example 2 0.23

[0096] According to the above table, the initial resistances of Examples 4-7 are slightly higher than those of Comparative Examples 1-2, that is, the initial resistances of the liquid metal sheath-core microfibers and liquid metal ionic gels of the stretchable conductor materials prepared with gallium-based liquid metal conductive pastes are relatively high.

[0097] In summary, the present application provides a gallium-based liquid metal conductive paste with strain-insensitive characteristics. An inorganic particle containing lone pair electrons is mixed with a liquid metal under strong shear force to form a liquid, semi-solid or solid paste with low surface tension, that is, a gallium-based liquid metal conductive paste. The paste is applied to various substrates through different process technologies to prepare a strain-insensitive stretchable conductor with both stretchability and high conductivity, or a liquid metal ion gel with strain-insensitive performance. In the gallium-based liquid metal conductive paste provided by the present application, the introduction of inorganic particles significantly enhances the overall stability of the composite material, moderately increases the overall resistance of the material, and promotes the formation of a porous conductive network embedded with nanoparticles inside the material to avoid drastic fluctuations in resistivity caused by too small resistance or changes in cross-sectional area, so that the material can still maintain a stable resistance change under high stretching and cyclic stretching conditions.

[0098] It should be noted that the present application is not limited to the above embodiments. The above embodiments are only examples, and embodiments with the same composition and the same effect as the technical idea within the technical solution scope of the present application are included in the technical scope of the present application. In addition, within the scope of not departing from the gist of the present application, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways constructed by combining some constituent elements of the embodiments are also included in the scope of the present application.

Claims

1. A gallium-based liquid metal conductive paste with strain-insensitive characteristics, characterized in that, The gallium-based liquid metal conductive paste is an alloy composite material formed by inorganic particles with lone pair electrons and liquid metal under mechanochemical action. Among them, the mass ratio of the inorganic particles with lone pair electrons is 5-33%, and the mass ratio of the liquid metal is 75-95%; in the gallium-based liquid metal conductive paste, a coordination bond is formed between the lone pair electrons of the inorganic particles with lone pair electrons and the empty orbitals of the liquid metal; the morphology of the gallium-based liquid metal conductive paste presents a liquid with low surface tension, a semi-solid paste or a solid powder according to the different proportions of the added inorganic particles; the gallium-based liquid metal conductive paste has strain-insensitive characteristics, and the resistance change rate of the stretchable conductor prepared by using the gallium-based liquid metal conductive paste changes less than 15% under 200% strain, and the initial resistance is less than 1Ω.

2. The gallium-based liquid metal conductive paste with strain-insensitive characteristics according to claim 1, wherein The inorganic particles with lone pair electrons are one or more of SiO2, Al2O3, TiO2, Fe3O4, aluminum nitride, boron nitride.

3. The gallium-based liquid metal conductive paste with strain-insensitive characteristics according to claim 1, wherein, The particle size of the inorganic particles with lone pair electrons is 20-500nm.

4. The gallium-based liquid metal conductive paste with strain-insensitive characteristics according to claim 1, characterized in that The liquid metal is a gallium-indium alloy or a gallium-indium-tin alloy, among which the mass ratios of gallium, indium, and tin are 62-95%, 5-22%, and 0-16% respectively.

5. A method for preparing a gallium-based liquid metal conductive paste with strain-insensitive characteristics according to any one of claims 1-4, characterized in that, Use a mortar or ball mill to apply strong shear force to the inorganic particles with lone pair electrons and the liquid metal, so that a violent mechanochemical action occurs between the inorganic particles and the liquid metal, and then a coordination bond is formed between the lone pair electrons of the inorganic particles and the empty orbitals of the liquid metal to obtain a uniform liquid, semi-solid paste or solid powder gallium-based liquid metal conductive paste.

6. Application of the gallium-based liquid metal conductive paste with strain-insensitive characteristics according to any one of claims 1-4, characterized in that The application refers to preparing a stretchable conductor by using the gallium-based liquid metal conductive paste, specifically including scraping or printing the gallium-based liquid metal conductive paste on an electrospun elastic fiber mat, coating the gallium-based liquid metal conductive paste on the surface of fibers or ionic gels, printing or printing the gallium-based liquid metal conductive paste on the surface of an elastomer, and continuously manufacturing liquid metal sheath-core microfibers by using the gallium-based liquid metal conductive paste through a coaxial wet spinning process.

7. Application of the gallium-based liquid metal conductive paste with strain-insensitive characteristics according to claim 6, characterized in that, In the application of continuously manufacturing liquid metal sheath-core microfibers by using the gallium-based liquid metal conductive paste through a coaxial wet spinning process, the preparation method of the liquid metal sheath-core microfibers includes the following steps: S1, mix the inorganic particles with lone pair electrons and the liquid metal, and strongly grind them with an agate mortar at room temperature for 30-50 minutes to prepare a solid or semi-solid paste that is not easy to flow and has stable conductivity, that is, the gallium-based liquid metal conductive paste, and the gallium-based liquid metal conductive paste is used as the core layer paste; S2, add the polymer to the solvent, and magnetically stir at room temperature until the polymer is completely dissolved to obtain a uniform and transparent sheath layer spinning solution; S3, inject the core layer paste and the sheath layer spinning solution prepared in steps S1-S2 into syringes respectively, and perform coaxial wet spinning with a coaxial spinneret, and the spun fibers are immersed in a coagulation bath; S4. Take out the fibers spun in step S3 from the coagulation bath and dry them in a vacuum oven at 35 - 45°C for 10 - 20 min to obtain liquid metal sheath-core microfibers, i.e., a stretchable conductor with strain-insensitive characteristics.

8. Use of the gallium-based liquid metal conductive paste with strain-insensitive characteristics according to claim 7, characterized in that, In step S1, the mass ratio of the inorganic particles containing lone pairs of electrons is 5 - 33%.

9. Use of the gallium-based liquid metal conductive paste with strain-insensitive characteristics according to claim 7, characterized in that, In step S2, the polymer is thermoplastic polyurethane elastomer, styrene-butadiene-styrene block copolymer or linear triblock copolymer, the solvent is deionized water, N,N-dimethylformamide, tetrahydrofuran, dimethyl sulfoxide, isopropanol, sodium sulfate, toluene, dichloromethane, chloroform or ethanol, and the concentration of the sheath spinning solution is 10 - 50%.

10. Application of the gallium-based liquid metal conductive paste with strain-insensitive characteristics according to claim 7, characterized in that, In step S3, the coagulation bath is composed of one or more of deionized water, ethanol, N,N-dimethylformamide, tetrahydrofuran, isopropanol, toluene, dichloromethane, chloroform, dimethyl sulfoxide and sodium sulfate.

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