Preparation method and application of repairable low-temperature curing slurry based on liquid metal microcapsules and conductive filler

Abstract

The invention discloses a preparation method and application of repairable low-temperature curing slurry based on liquid metal microcapsules and conductive filler, and belongs to the field of flexible circuits. The invention aims to solve the problems that the existing liquid metal and conductive filler are poor in compatibility, agglomeration or intermetallic compounds are easy to form, the repairing effect generated in the circuit deformation process is greatly weakened, and small-particle-size liquid metal particles are difficult to crack and repair the circuit in the circuit deformation process. The method comprises: 1, preparing an elastomer solution; 2, preparing a liquid metal capsule; and 3, preparing the liquid metal capsule / conductive filler / elastomer ink. The method is applied to plane printing, complex structure surface printing and multi-layer stretchable flexible circuit printing. The invention is used for preparation and application of the repairable low-temperature curing slurry based on the liquid metal microcapsule and the conductive filler.

Description

Technical Field

[0001] The invention belongs to the field of flexible circuits. Background Art

[0002] In recent years, electronic products have been rapidly updated towards miniaturization, portability, and multifunctionality. Traditional rigid electronic products cannot work properly in large deformation service environments due to poor mechanical and biocompatibility. Traditional printed circuits mostly use a percolation network constructed by rigid conductive fillers as a conductive structure, which results in a high probability that the printed circuit will destroy its percolation network structure during stretching, bending, and torsion, thereby causing a short circuit. Liquid metal has attracted widespread attention as a material that combines the electrical and thermal conductivity of metals with the flexible fluidity of liquids. However, the spontaneously generated semiconductor oxide layer on the surface of liquid metal particles increases its percolation threshold as a conductive filler, making it impossible to construct a conductive network structure formed by mutual contact between fillers like traditional conductive fillers. For the above challenges, combining liquid metal with traditional rigid metal particle conductive fillers is an ideal solution. However, due to the wettability of the oxide layer on the surface of the liquid metal, the phagocytosis of the liquid metal during the mixing process causes the liquid metal particles and the filler to agglomerate, which in turn greatly weakens the repair effect of the liquid metal during the circuit deformation process. In addition, for high-resolution direct writing printing, the appropriate particle size is a necessary factor for the stable extrusion of the slurry. When using a precision dispensing needle (<100μm), large-size particles and the agglomeration of particles between the granular liquid metal and the conductive filler increase the risk of needle clogging. Although reducing the particle size of the liquid metal particles reduces the risk of needle clogging, small-size liquid metal particles are more difficult to break during the deformation of the circuit to repair the circuit. Therefore, it is crucial to reduce the degree of agglomeration between the liquid metal and the conductive filler and to increase the ability of the liquid metal particles to break at a small particle size to repair the circuit. Summary of the invention

[0003] The present invention aims to solve the problems that the existing liquid metal and conductive filler have poor compatibility, are easy to form agglomerates or intermetallic compounds, resulting in a significant weakening of the repairing effect during circuit deformation, and small-sized liquid metal particles are difficult to break and repair the circuit during circuit deformation. The present invention further provides a preparation method and application of a repairable low-temperature curing slurry based on liquid metal microcapsules and conductive fillers.

[0004] A method for preparing a repairable low-temperature curing slurry based on liquid metal microcapsules and conductive fillers is carried out according to the following steps:

[0005] 1. Preparation of elastomer solution:

[0006] dissolving the elastomer in a volatile solvent to obtain an elastomer solution;

[0007] 2. Preparation of liquid metal capsules:

[0008] The liquid metal is added to a solution containing a surfactant, and then the liquid metal is crushed into particles with a particle size distribution of 50 nm to 200 μm, and finally heated and stirred for 1 h to 24 h at a temperature of 30° C. to 80° C. and a stirring speed of 100 r / min to 1000 r / min to obtain liquid metal capsules coated with the surfactant;

[0009] 3. Preparation of liquid metal capsules / conductive fillers / elastomer inks:

[0010] The elastomer solution and the liquid metal capsules coated with the surfactant are mixed evenly, and then the conductive fillers are added in batches and mixed evenly to obtain a repairable low-temperature curing slurry based on the liquid metal microcapsules and the conductive fillers;

[0011] Alternatively, the conductive filler is first added to the elastomer solution in batches and mixed evenly, and then the liquid metal capsules coated with the surfactant are added and mixed evenly to obtain a repairable low-temperature curing slurry based on liquid metal microcapsules and conductive fillers.

[0012] An application of a repairable low-temperature curing slurry based on liquid metal microcapsules and conductive fillers, which is used for flat printing, complex structure surface printing and multi-layer stretchable flexible circuit printing; and the forming method is one of screen printing, direct ink writing printing with a dispensing needle with an inner diameter of 1μm to 0.8mm, and laser engraving mask printing, or a combination of several of them.

[0013] The beneficial effects of the present invention are:

[0014] 1. The present invention prepares functionalized liquid metal particles with a surfactant coated on the surface of the oxide layer, thereby improving the ability of the liquid metal particles to repair circuit cracks, which is beneficial to the repairing effect of the liquid metal particles on the circuit.

[0015] 2. The liquid metal particles of the present invention are coated with silver flakes and evenly dispersed without forming agglomerates and intermetallic compounds. The liquid metal has good compatibility with the conductive filler, which can enhance the repair effect produced during the circuit deformation process and solve the problem that small-sized liquid metal particles are difficult to break and repair the circuit during the circuit deformation process.

[0016] 3. The present invention proposes a method for preparing a liquid metal / conductive filler / elastomer high conductivity ink and a strategy for realizing curved surface forming flexible circuits and multi-layer flexible circuits. No high temperature treatment is required. After low temperature curing at 25°C to 150°C, the conductivity can reach up to 10 6 In addition, after the ink is cured and encapsulated, it still has excellent resistance stability even at a high stretching rate of 1000% (R / R0<5 under 1000% axial stretching).

[0017] 4. Due to the presence of the initial conductive rigid metal particle filler, the ink only needs to be cured at low temperature to obtain the initial conduction capability without the need for subsequent sintering and activation treatment, which greatly simplifies the use of liquid metal-based flexible circuit ink. In addition, since the elastomer in the ink solidifies after the solvent evaporates, compared to pure liquid metal, the flexible circuit printed by this method does not require packaging treatment, and there is no need to worry about the circuit being easily erased due to the liquid state, and it can be used directly without leakage.

[0018] 5. The present invention combines the high conductivity of solid silver sheet filler and the flexible stretchability of liquid metal. The initial conductivity is provided by the rigid metal particle conductive filler. Liquid metal microcapsules of different particle sizes are used as the repair soft conductive filler in the ink. During the stretching process, the oxide layer coated with the active agent on the surface of the liquid metal particles breaks, and the internal liquid metal flows out to compensate for the damage of the silver sheet conductive network. It can achieve a high initial conductivity while meeting good deformation ability (bending, twisting, stretching, etc.), has excellent electromechanical coupling performance, and can still maintain the circuit conduction even at ultra-high stretching rate (>1000%) for 0° to 180° bending. The conductivity does not decay during 10,000 stretch-release cycles at 100% strain.

[0019] 6. The present invention can realize efficient production of flat surfaces and simple curved surfaces through screen printing, and can also print circuits on certain complex surfaces (curved surfaces, slits, etc.) through the strategy of direct ink writing (DIW) additive manufacturing, solving the problem of difficult circuit molding on complex surfaces. It can save materials and achieve high-precision printing. In addition, the ability to conduct electricity can be obtained by low-temperature curing, which further broadens its selectivity for flexible substrates. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a SEM image of liquid metal particles after ultrasonic crushing in step 2 of Example 1;

[0021] Figure 2 This is a SEM image of the liquid metal capsule coated with a surfactant prepared in step 2 of Example 1;

[0022] Figure 3 This is a microscopic morphology of the surface of the repairable low-temperature curing slurry based on liquid metal microcapsules and conductive fillers after curing prepared in step 3 of Example 1;

[0023] Figure 4 The conductivity of the repairable low-temperature curing slurry based on liquid metal microcapsules and conductive fillers prepared in step 3 of Example 1 after curing;

[0024] Figure 5 This is a photo of the circuit after curing in step 3 of Example 2;

[0025] Figure 6 The resistance change of the circuit after 1000% axial stretching after curing in step 3 of embodiment 3, a is the resistance change during the stretching process, and b is the resistance change rate; in the figure, R0 is the initial resistance, and R is the resistance after stretching;

[0026] Figure 7 The resistance change of the circuit after curing in step 3 of embodiment 3 during the 100% axial stretch-release cycle;

[0027] Figure 8 The resistance change of the circuit after curing in step 3 of embodiment 3 during 180° bending within 400 minutes;

[0028] Fig. 9 This is a demonstration of the 1000% axial stretching conduction capability of the circuit after curing in step 3 of embodiment 3. DETAILED DESCRIPTION

[0029] Specific implementation method 1: This implementation method is a method for preparing a repairable low-temperature curing slurry based on liquid metal microcapsules and conductive fillers, which is carried out according to the following steps:

[0030] 1. Preparation of elastomer solution:

[0031] dissolving the elastomer in a volatile solvent to obtain an elastomer solution;

[0032] 2. Preparation of liquid metal capsules:

[0033] The liquid metal is added to a solution containing a surfactant, and then the liquid metal is crushed into particles with a particle size distribution of 50 nm to 200 μm, and finally heated and stirred for 1 h to 24 h at a temperature of 30° C. to 80° C. and a stirring speed of 100 r / min to 1000 r / min to obtain liquid metal capsules coated with the surfactant;

[0034] 3. Preparation of liquid metal capsules / conductive fillers / elastomer inks:

[0035] The elastomer solution and the liquid metal capsules coated with the surfactant are mixed evenly, and then the conductive fillers are added in batches and mixed evenly to obtain a repairable low-temperature curing slurry based on the liquid metal microcapsules and the conductive fillers;

[0036] Alternatively, the conductive filler is first added to the elastomer solution in batches and mixed evenly, and then the liquid metal capsules coated with the surfactant are added and mixed evenly to obtain a repairable low-temperature curing slurry based on liquid metal microcapsules and conductive fillers.

[0037] This specific embodiment uses an elastomer solution as the filler loading phase of the slurry, has good wettability to a variety of materials (such as plastics, ceramics, polymers, metal sheets / plates, etc.), and can achieve stable printing or printing on a variety of substrates.

[0038] The beneficial effects of this embodiment are:

[0039] 1. This embodiment prepares functionalized liquid metal particles with a surfactant coated on the surface of the oxide layer, which improves the ability of the liquid metal particles to repair circuit cracks and is beneficial to the repairing effect of the liquid metal particles on the circuit.

[0040] 2. In this embodiment, the liquid metal particles are coated with silver sheets and evenly dispersed without forming agglomerates and intermetallic compounds. The liquid metal has good compatibility with the conductive filler, which can enhance the repair effect produced during the circuit deformation process. At the same time, it solves the problem that small-sized liquid metal particles are difficult to break and repair the circuit during the circuit deformation process.

[0041] 3. This embodiment proposes a method for preparing a liquid metal / conductive filler / elastomer high conductivity ink and a strategy for realizing curved surface forming flexible circuits and multi-layer flexible circuits. No high temperature treatment is required. After low temperature curing at 25°C to 150°C, the conductivity can reach up to 10 6 In addition, after the ink is cured and encapsulated, it still has excellent resistance stability even at a high stretching rate of 1000% (R / R0<5 under 1000% axial stretching).

[0042] 4. Due to the presence of the initial conductive rigid metal particle filler, the ink only needs to be cured at low temperature to obtain the initial conduction capability without the need for subsequent sintering and activation treatment, which greatly simplifies the use of liquid metal-based flexible circuit ink. In addition, since the elastomer in the ink solidifies after the solvent evaporates, compared to pure liquid metal, the flexible circuit printed by this method does not require packaging treatment, and there is no need to worry about the circuit being easily erased due to the liquid state, and it can be used directly without leakage.

[0043] 5. This embodiment combines the high conductivity of solid silver sheet filler and the flexible stretchability of liquid metal. The initial conductivity is provided by the rigid metal particle conductive filler. Liquid metal microcapsules of different particle sizes are used as the repair soft conductive filler in the ink. During the stretching process, the oxide layer coated with the active agent on the surface of the liquid metal particles breaks, and the internal liquid metal flows out to compensate for the damage of the silver sheet conductive network. It can achieve a high initial conductivity while meeting good deformation capabilities (bending, twisting, stretching, etc.), has excellent electromechanical coupling performance, and can still maintain the circuit conduction even at ultra-high stretching rates (>1000%) for 0° to 180° bending. The conductivity does not decay during 10,000 stretch-release cycles at 100% strain.

[0044] 6. This embodiment can realize efficient production of flat surfaces and simple curved surfaces through screen printing, and can also print circuits on certain complex surfaces (curved surfaces, slits, etc.) through the strategy of direct ink writing (DIW) additive manufacturing, solving the problem of difficult circuit molding on complex surfaces. It can save materials and achieve high-precision printing. In addition, the ability to conduct electricity can be obtained by low-temperature curing, which further broadens its selectivity for flexible substrates.

[0045] Specific embodiment 2: This embodiment is different from specific embodiment 1 in that: the elastomer described in step 1 is polypropylene, polycarbonate, polyurethane, nylon, polyetheretherketone or polyethersulfone; the volatile solvent described in step 1 is DBE solvent, dimethylacetamide, dimethylformamide, dichlorothionyl, deionized water, acetone, banana oil, volatile oil, butyl lactate, carbon disulfide, carbon tetrachloride, coal tar solvent, diacetone alcohol, ethyl acetate or ethanol; the mass ratio of the elastomer described in step 1 to the volatile solvent is 1: (1-10). Others are the same as specific embodiment 1.

[0046] Specific embodiment 3: This embodiment differs from specific embodiment 1 or 2 in that: in step 1, the elastomer is dissolved in a volatile solvent at a temperature of 25°C to 150°C and a magnetic stirring speed of 100 r / min to 2500 r / min to obtain an elastomer solution. The rest is the same as specific embodiment 1 or 2.

[0047] Specific implementation method 4: This implementation method is different from any one of specific implementation methods 1 to 3 in that: the volume ratio of the mass of the surfactant to the solvent in the surfactant-containing solution described in step 2 is 1g: (10-100) mL; the surfactant is one of silane coupling agent, sodium lignin sulfonate, sodium alginate, PVP, starch, benzalkonium chloride, benzalkonium bromide, benzalkonium chloride, sodium dodecyl sulfate and sodium fatty alcohol polyoxyethylene ether sulfate or a combination of several thereof; the solvent is ethanol or acetone; the liquid metal described in step 2 is room temperature liquid metal or liquid metal with a melting point below 240°C; the volume ratio of the mass of the liquid metal described in step 2 to the surfactant-containing solution is 1g: (3-8) mL. Others are the same as specific implementation methods 1 to 3.

[0048] The liquid metal is gallium, gallium-indium eutectic (75wt% Ga, 25wt% In), gallium-indium-tin eutectic (Ga:In:Sn68.5wt%:21.5wt%:10wt%).

[0049] Specific implementation mode 5: This implementation mode is different from specific implementation modes 1 to 4 in that: the crushing described in step 2 is shear crushing or ultrasonic crushing; the shear crushing is specifically under the condition of a shear rate of 1000r / min to 2000r / min, shear crushing for 30min to 300min, and obtaining particles with a particle size distribution of 200nm to 30μm; the ultrasonic crushing is specifically under the condition of an ice water bath or a normal temperature water bath, an ultrasonic probe 2mm to 10mm away from the liquid metal droplet and an ultrasonic power of 100W to 720W, ultrasonic crushing for 5s to 60min, obtaining particles with a particle size distribution of 50nm to 200μm, and each ultrasonic crushing of 2g of liquid metal. The rest is the same as specific implementation modes 1 to 4.

[0050] Specific implementation method six: This implementation method is different from any one of specific implementation methods one to five in that: the mass ratio of the elastomer solution described in step three to the liquid metal capsule coated with a surfactant is 1:(0.5-8); the mass ratio of the elastomer solution described in step three to the conductive filler is 1:(0.25-8); the conductive filler described in step three is one or a combination of Ag particles, Au particles, Fe particles, Al particles, Cu particles, Ni particles, graphene, carbon nanotubes and graphite powder; the average particle size of the conductive filler described in step three is 500nm-20μm; in step three, the viscosity of the repairable low-temperature curing slurry based on liquid metal microcapsules and conductive fillers is regulated by adding a diluent, and the diluent is acetone, dimethylacetamide, ethanol or deionized water. The rest is the same as specific implementation methods one to five.

[0051] Specific embodiment 7: This embodiment is different from Specific embodiments 1 to 6 in that: the mixing described in step 3 is specifically mixed by grinding or a planetary vacuum stirring deaerator; when a planetary vacuum stirring deaerator is used, the stirring is performed for 1 min to 4 min at a rotation speed of 500 r / min to 2500 r / min. The rest is the same as Specific embodiments 1 to 6.

[0052] Specific embodiment eight: This embodiment is an application of a repairable low-temperature curing slurry based on liquid metal microcapsules and conductive fillers, which is used for flat printing, complex structure surface printing and multi-layer stretchable flexible circuit printing; and the forming method is one of screen printing, direct ink writing printing with a dispensing needle with an inner diameter of 1μm to 0.8mm, and laser engraving mask printing, or a combination of several of them.

[0053] This specific implementation method can realize non-stop printing of multi-layer flexible circuits through a multi-material printer, and complete the integration and packaging of electronic devices (resistors, capacitors, crystal oscillators, sensors, chips, etc.).

[0054] This specific implementation method constructs a printing path through G code and a curved surface scanning tool to control the microelectronic printer to accurately control the printing of circuits on complex surfaces (such as curved surfaces, slits, etc.).

[0055] In this specific implementation method, after the circuit is printed, it is cured at 25°C to 150°C for 0.5h to 24h, and no other treatment is required to obtain 10 3 S / m~10 6 Conductivity in S / m.

[0056] Specific embodiment 9: This embodiment is different from specific embodiment 8 in that: before printing the repairable low-temperature curing slurry based on liquid metal microcapsules and conductive fillers, it is first ground by three rollers for 1 to 10 times, and the roller spacing is 3 μm to 100 μm; when screen printing is used, the mesh number of the screen printing is 40 to 420 meshes. The rest is the same as specific embodiment 8.

[0057] Specific embodiment 10: This embodiment differs from specific embodiment 8 or 9 in that: when it is used for printing on a complex structure surface, the complex structure is a curved structure or a slit structure, and the printing thickness is 20μm to 200μm; when it is used for printing a multi-layer stretchable flexible circuit, a through hole is provided on the multi-layer dielectric layer, and the through hole is filled with liquid metal as an interlayer connection; the dielectric layer is silicone rubber, polyurethane or thermoplastic elastomer. Others are the same as specific embodiment 8 or 9.

[0058] The following examples are used to verify the beneficial effects of the present invention:

[0059] Embodiment 1:

[0060] A method for preparing a repairable low-temperature curing slurry based on liquid metal microcapsules and conductive fillers is carried out according to the following steps:

[0061] 1. Preparation of elastomer solution:

[0062] Under the conditions of a temperature of 80° C. and a magnetic stirring speed of 200 r / min, the elastomer is dissolved in a volatile solvent and stirred for 5 h to obtain an elastomer solution;

[0063] The elastomer is polyurethane (TPU);

[0064] The volatile solvent is DBE solvent;

[0065] The mass ratio of the elastomer to the volatile solvent is 25:75;

[0066] 2. Preparation of liquid metal capsules:

[0067] The liquid metal is added to a solution containing a surfactant, and then the liquid metal is crushed into particles with a particle size of 3 μm to 8 μm. Finally, the mixture is heated and stirred for 5 hours at a temperature of 60° C. and a stirring speed of 200 r / min to obtain liquid metal capsules coated with the surfactant.

[0068] The volume ratio of the surfactant mass to the solvent in the surfactant-containing solution is 1g:80mL; the surfactant is silane coupling agent KH570; and the solvent is acetone;

[0069] The liquid metal is EGaIn gallium-indium eutectic (75wt% Ga, 25wt% In) with a melting point of 16°C;

[0070] The mass ratio of the liquid metal to the volume ratio of the solution containing the surfactant is 1 g:4 mL;

[0071] The crushing is ultrasonic crushing; the ultrasonic crushing is specifically carried out under the conditions of ice water bath, ultrasonic probe 8mm away from liquid metal droplet and ultrasonic power 360W, ultrasonic crushing for 40s, and each ultrasonic crushing 2g of liquid metal;

[0072] 3. Preparation of liquid metal capsules / conductive fillers / elastomer inks:

[0073] The elastomer solution and the liquid metal capsules coated with the surfactant are mixed evenly, and then the conductive fillers are added in batches and mixed evenly to obtain a repairable low-temperature curing slurry based on the liquid metal microcapsules and the conductive fillers;

[0074] The mass ratio of the elastomer solution to the liquid metal capsule coated with the surfactant is 1:1.5;

[0075] The mass ratio of the elastomer solution to the conductive filler is 1:1.5;

[0076] The conductive filler is flaky Ag particles; the average particle size of the conductive filler is 5 μm;

[0077] In step 3, the viscosity of the repairable low-temperature curing slurry based on liquid metal microcapsules and conductive fillers is regulated by adding a diluent; at a shear rate of 1 / 30s -1 Under the condition of , the viscosity is 5025mPa·s; the diluent is acetone;

[0078] The two mixing steps described in step 3 are carried out according to the following steps: first, stir at a speed of 500 r / min for 30 s, then stir at a speed of 1000 r / min for 1 min, then stir at a speed of 2500 r / min for 1 min, and finally stir at a speed of 500 r / min for 30 s.

[0079] At a temperature of 80°C, the repairable low-temperature curing slurry based on liquid metal microcapsules and conductive fillers prepared in Example 1 was cured for 5 hours. The average conductivity of the five samples was 1.26×10 6 S / m.

[0080] Embodiment 2:

[0081] A printing method of a repairable low-temperature curing slurry based on liquid metal microcapsules and conductive fillers prepared by Example 1:

[0082] 1. Grinding:

[0083] The repairable low-temperature curing slurry based on liquid metal microcapsules and conductive fillers was ground by three rollers, the roller spacing was transitioned from 90 μm to 20 μm, and the difference between the inlet and outlet roller spacing was progressively increased from 70 μm to 2 μm each time, and the grinding was repeated 5 times to obtain the ground slurry;

[0084] 2. Printing complex structure surface circuits through DIW printing:

[0085] The ground slurry was loaded into the dispensing needle tube, and the printing path was controlled by the G code. Under the conditions of the inner diameter of the needle being 150 μm, the height of the needle being 100 μm from the printing surface, the printing speed being 5 mm / s to 10 mm / s, and the pressure being 8 Psi to 15 Psi, the linear circuit was printed on the surface of a polyethylene plastic hemisphere with a diameter of 5 cm by the DIW technology to obtain the printed circuit;

[0086] The thickness of the printed circuit is 0.2mm; the width of the linear circuit is 0.3mm;

[0087] 3. Flexible circuit curing and electronic device integration:

[0088] The printed circuit was cured at 80°C for 30 minutes to obtain a cured circuit, and the LED lamp pins were moistened with EGaIn liquid metal (75wt% Ga, 25wt% In), and then fixed on the cured circuit, and a drop of ground slurry was added to the connection, and then cured again at 80°C for 3 minutes, and finally 503 silicone was used to fill the connection and cured at 80°C for 2 minutes to obtain the circuit after integrating the first layer of electronic devices;

[0089] The thickness of the circuit after curing is 60 μm;

[0090] 4. Packaging:

[0091] Under the conditions of temperature of 60°C, inner diameter of needle of 400μm, distance between needle height and printing surface of 200μm, printing speed of 5mm / s and pressure of 10Psi, PDMS (Dow Corning 184) with a thickness of 200μm was printed as an encapsulation layer on the circuit after the integration of the first layer of electronic devices by DIW technology. The printing process was simultaneously cured, and then the temperature was 80°C and cured for 30min to complete the encapsulation of the first layer of circuit.

[0092] 5. Multi-layer circuit printing:

[0093] Repeat steps 2 to 4, fill the reserved through holes with EGaIn liquid metal (75wt% Ga, 25wt% In) to complete the interlayer electrical connection, and obtain a curved surface printed multilayer circuit;

[0094] 6. Leading out of circuit ports:

[0095] The copper foil was wetted with EGaIn liquid metal (75wt% Ga, 25wt% In) and fixed at the reserved port. A drop of ground slurry was added to the connection, and then cured again at 80°C for 3 minutes. Finally, 503 silicone was used to fill the connection and cured at 80°C for 2 minutes.

[0096] Embodiment 3: This embodiment is different from Embodiment 2 in that: in step 2, the linear circuit is printed on the surface of the polyurethane flat substrate by DIW technology; in step 3, the circuit after curing is 5 mm wide and 2 cm long, with 5 mm reserved at both ends for connecting copper foil. The rest is the same as Embodiment 2.

[0097] Figure 1 This is a SEM image of liquid metal particles after ultrasonic crushing in step 2 of Example 1; it can be seen from the figure that under the action of ultrasound, the liquid metal is crushed into relatively regular spherical particles.

[0098] Figure 2 The SEM image of the liquid metal capsule coated with surfactant prepared in step 2 of Example 1; and Figure 1 In comparison, the morphology of liquid metal particles changed after being coated with surfactant.

[0099] Figure 3 This is a microscopic morphology of the surface of the repairable low-temperature curing slurry based on liquid metal microcapsules and conductive fillers after curing prepared in step three of Example 1; as can be seen from the figure, the liquid metal particles are coated with silver flakes and evenly dispersed, and no agglomerates or intermetallic compounds are formed.

[0100] Figure 4The conductivity of the repairable low-temperature curing slurry based on liquid metal microcapsules and conductive fillers prepared in step 3 of Example 1 after curing; it can be seen from the figure that the conductivity of the five parallel experimental samples is higher than 10 6 S / m.

[0101] Figure 5 This is a photo of the circuit after curing in step 3 of Example 2. As can be seen from the figure, a pattern similar to a mosquito coil structure is printed on the hemispherical plastic surface, with a line width of 0.3 mm.

[0102] Under the axial tensile rate of 1mm / s, the resistance change of the test circuit during the stretching process; Figure 6 The resistance change of the circuit after 1000% axial stretching after curing in step three of Example 3, a is the resistance change during the stretching process, and b is the resistance change rate; R0 in the figure is the initial resistance, and R is the resistance after stretching; it can be seen from the figure that even under the condition of 1000% axial stretching, the circuit is still conductive and the resistance change rate (R / R0) is less than 5.

[0103] Under an axial tensile rate of 1 mm / s, the resistance change of the test circuit after 10,000 stretch-release cycles; Figure 7 The resistance change of the circuit after curing in step 3 of Example 3 during the 100% axial stretch-release cycle; as can be seen from the figure, the resistance change in 10,000 stretch-release cycles always varies within 0.8 to 1.2Ω and shows good periodicity.

[0104] Test the resistance change of the circuit during 2000 bends from 0° to 180° at a bending rate of 1mm / s; Figure 8 The resistance change of the circuit after curing in step 3 of Example 3 during 180° bending within 400 minutes; as can be seen from the figure, the resistance change during the bending process is less than 0.02Ω, and almost no change occurs.

[0105] Connect the circuit to a multimeter, and the displayed numbers are the resistances under different stretching states; Fig. 9 The 1000% axial stretching conduction capability of the circuit after curing in step 3 of embodiment 3 is demonstrated; as can be seen from the figure, the circuit can still maintain its conduction capability under ultra-high stretching rate.

Claims

1. A method for preparing a repairable low-temperature curing slurry based on liquid metal microcapsules and conductive fillers, characterized in that It is carried out in the following steps:

1. Preparation of elastomer solution: dissolving the elastomer in a volatile solvent to obtain an elastomer solution; 2. Preparation of liquid metal capsules: The liquid metal is added to a solution containing a surfactant, and then the liquid metal is crushed into particles with a particle size distribution of 50 nm to 200 μm, and finally heated and stirred for 1 h to 24 h at a temperature of 30° C. to 80° C. and a stirring speed of 100 r / min to 1000 r / min to obtain liquid metal capsules coated with the surfactant; 3. Preparation of liquid metal capsules / conductive fillers / elastomer inks: The elastomer solution and the liquid metal capsules coated with the surfactant are mixed evenly, and then the conductive fillers are added in batches and mixed evenly to obtain a repairable low-temperature curing slurry based on the liquid metal microcapsules and the conductive fillers; Alternatively, the conductive filler is first added to the elastomer solution in batches and mixed evenly, and then the liquid metal capsules coated with the surfactant are added and mixed evenly to obtain a repairable low-temperature curing slurry based on liquid metal microcapsules and conductive fillers.

2. The method for preparing a repairable low-temperature curing slurry based on liquid metal microcapsules and conductive fillers according to claim 1, characterized in that The elastomer described in step one is polypropylene, polycarbonate, polyurethane, nylon, polyetheretherketone or polyethersulfone; the volatile solvent described in step one is DBE solvent, dimethylacetamide, dimethylformamide, dichlorothionyl, deionized water, acetone, banana oil, volatile oil, butyl lactate, carbon disulfide, carbon tetrachloride, coal tar solvent, diacetone alcohol, ethyl acetate or ethanol; the mass ratio of the elastomer described in step one to the volatile solvent is 1:(1-10).

3. The method for preparing a repairable low-temperature curing slurry based on liquid metal microcapsules and conductive fillers according to claim 1, characterized in that In step 1, the elastomer is dissolved in a volatile solvent at a temperature of 25° C. to 150° C. and a magnetic stirring speed of 100 r / min to 2500 r / min to obtain an elastomer solution.

4. The method for preparing a repairable low-temperature curing slurry based on liquid metal microcapsules and conductive fillers according to claim 1, characterized in that The volume ratio of the surfactant mass to the solvent in the surfactant-containing solution described in step 2 is 1g:(10-100)mL; the surfactant is one of silane coupling agent, sodium lignin sulfonate, sodium alginate, PVP, starch, benzalkonium chloride, benzalkonium bromide, benzalkonium chloride, sodium dodecyl sulfate and sodium polyoxyethylene fatty alcohol sulfate, or a combination of several thereof; the solvent is ethanol or acetone; the liquid metal described in step 2 is room temperature liquid metal or liquid metal with a melting point below 240°C; the volume ratio of the liquid metal described in step 2 to the surfactant-containing solution is 1g:(3-8)mL.

5. The method for preparing a repairable low-temperature curing slurry based on liquid metal microcapsules and conductive fillers according to claim 1, characterized in that The crushing described in step 2 is shear crushing or ultrasonic crushing; the shear crushing is specifically carried out under the condition of a shear rate of 1000r / min to 2000r / min, shear crushing for 30min to 300min, and obtaining particles with a particle size distribution of 200nm to 30μm; the ultrasonic crushing is specifically carried out under the conditions of an ice water bath or a normal temperature water bath, an ultrasonic probe 2mm to 10mm away from the liquid metal droplet and an ultrasonic power of 100W to 720W, ultrasonic crushing for 5s to 60min, obtaining particles with a particle size distribution of 50nm to 200μm, and 2g of liquid metal is crushed each time by ultrasonication.

6. The method for preparing a repairable low-temperature curing slurry based on liquid metal microcapsules and conductive fillers according to claim 1, characterized in that The mass ratio of the elastomer solution described in step three to the liquid metal capsules coated with surfactant is 1:(0.5~8); the mass ratio of the elastomer solution described in step three to the conductive filler is 1:(0.25~8); the conductive filler described in step three is one or a combination of Ag particles, Au particles, Fe particles, Al particles, Cu particles, Ni particles, graphene, carbon nanotubes and graphite powder; the average particle size of the conductive filler described in step three is 500nm~20μm; in step three, the viscosity of the repairable low-temperature curing slurry based on liquid metal microcapsules and conductive fillers is regulated by adding a diluent, and the diluent is acetone, dimethylacetamide, ethanol or deionized water.

7. The method for preparing a repairable low-temperature curing slurry based on liquid metal microcapsules and conductive fillers according to claim 1, characterized in that The uniform mixing described in step three is specifically performed by grinding or a planetary vacuum stirring deaerator; when a planetary vacuum stirring deaerator is used, stirring is performed for 1 min to 4 min at a rotation speed of 500 r / min to 2500 r / min.

8. The use of a repairable low-temperature curing slurry based on liquid metal microcapsules and conductive fillers prepared as claimed in claim 1, characterized in that It is used for flat printing, complex structure surface printing and multi-layer stretchable flexible circuit printing; The forming method is one of screen printing, direct ink writing printing with a dispensing needle with an inner diameter of 1 μm to 0.8 mm, and laser engraving mask printing, or a combination of several of them.

9. The use of a repairable low-temperature curing slurry based on liquid metal microcapsules and conductive fillers according to claim 8, characterized in that Before printing, the repairable low-temperature curing slurry based on liquid metal microcapsules and conductive fillers is first ground with three rollers for 1 to 10 times, with the roller spacing being 3 μm to 100 μm; when screen printing is used, the mesh size of the screen printing is 40 to 420 meshes.

10. The use of a repairable low-temperature curing slurry based on liquid metal microcapsules and conductive fillers according to claim 8, characterized in that When it is used for printing on a complex structure surface, the complex structure is a curved structure or a slit structure, and the printing thickness is 20μm to 200μm; when it is used for printing a multi-layer stretchable flexible circuit, through holes are set on the multi-layer dielectric layer, and the through holes are filled with liquid metal as an interlayer connection; the dielectric layer is silicone rubber, polyurethane or thermoplastic elastomer.

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