Stretchable conductor material for 3D printing of vertical interconnection wires in multilayer stretchable electrons and preparation method of stretchable conductor material

Abstract

The invention belongs to the field of preparation of stretchable conductor materials, and provides a stretchable conductor material for 3D printing of vertical interconnection wires in multilayer stretchable electronics and a preparation method thereof.The preparation method comprises the steps that an elastomer matrix, an inhibitor, a coupling agent and a rheology modifier are mixed to be uniform, then a flow promoter is added, the mixture is mixed to be uniform and subjected to synchronous vacuum defoaming, and the stretchable conductor material is obtained; an organic carrier is obtained; adding the flocculent silver particles into a dispersing agent, and performing ultrasonic dispersion to obtain flocculent silver particle dispersion liquid; uniformly mixing the organic carrier and the flocculent silver particle dispersion liquid, and performing two-stage stirring and synchronous vacuum defoaming to obtain a stretchable conductor material; wherein the boiling point range of the dispersing agent is 60-100 DEG C, and the dispersing agent and the organic carrier are mutually soluble; and the flocculent silver particles account for 50-80% of the mass fraction of the stretchable conductor material. The prepared silver-based stretchable conductor material has high conductivity, high stretchability, low electrical hysteresis and low-temperature curing performance, stretchable VIA direct forming can be achieved through a direct-writing 3D printing process, and the silver-based stretchable conductor material is particularly suitable for electrical interconnection between different functional layers in a multi-layer stretchable electronic device. The stretchable conductor material is mainly composed of an elastomer matrix, a conductive filler, a rheology modifier, a silane coupling agent, a flow promoter, an inhibitor and the like.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of stretchable conductor material preparation, and particularly relates to a stretchable conductor material for 3D printing of multilayer stretchable electronic vertical interconnection wires and a preparation method thereof. BACKGROUND

[0002] The information disclosed in this Background section is for the purpose of increasing the understanding of the general background of the application and does not necessarily constitute an admission that this information constitutes prior art.

[0003] Multilayer stretchable electronics, as an important branch of flexible electronics, is an electronic device that maintains stable electrical function under mechanical deformation such as stretching, bending and compression. It is usually composed of multilayer elastic substrate, planar wire, vertical interconnection wire and electronic component. Due to its ability to stack different electronic components in the vertical direction and integrate components into three-dimensional space, it can effectively improve the functional density and spatial resolution of the device without increasing the lateral size of the electronic device. It is widely used in many fields such as electronic skin, wearable devices, implantable medical electronic devices and soft robots. A key difficulty in the manufacturing of multilayer stretchable electronics is how to achieve low-cost and simple manufacturing of high-performance stretchable vertical interconnection wires, which directly affects the stability of electrical connection between different functional layers and signal transmission latency of multilayer stretchable electronic devices during strain. Traditional manufacturing methods usually use physical drilling (such as laser ablation) combined with electroplating or filling liquid metal process to form vertical interconnection wires. However, the physical drilling method can damage the overall mechanical properties of the stretchable substrate layer, easily form stress concentration areas during strain, and the metal structure of electroplating generally has problems such as brittleness, which can easily crack during tensile strain, causing electrical connection failure. When using liquid metal filling, there are challenges such as difficulty in wetting regulation, incomplete filling and leakage under external force.

[0004] Additive manufacturing technology (3D printing) can realize the integrated formation of vertical interconnection wires and elastic body substrate, which can simplify the manufacturing process and effectively alleviate the stress concentration problem of the vertical interconnection wire area during strain. However, due to the performance bottleneck of stretchable conductor materials and the compatibility problem of materials and 3D printing process, the direct formation of high-performance (high conductivity, high stretchability, low electrical hysteresis, and good compatibility with the substrate) stretchable vertical interconnection wires (VIA) through 3D printing is still a difficult problem to be solved.

[0005] A study discloses a kind of for electric field driven jetting micro-nano 3D printing nano silver paste, by modified nano silver powder, organic carrier, polymer resin composition, but the above-mentioned silver paste is not stretchable, it is not related to the difficulty of the mutual restriction of the conductivity-stretchability-electrical hysteresis existing in stretchable conductor.

[0006] Therefore, it is urgent to develop a kind of high-performance stretchable conductor material, not only can perfectly adapt to 3D printing process requirements, also should have unique rheological properties, to realize the direct forming of VIA structure. SUMMARY

[0007] In order to solve the above problems, the present application provides a kind of silver-based stretchable conductor preparation method suitable for stretchable vertical interconnection wire direct writing 3D printing process.The maximum tensile rate of the stretchable conductor of the present application can be 200%, and the vertical interconnection wire can be directly formed, and after multiple stretching cycle tests, it still has lower electrical hysteresis.

[0008] In order to achieve the above purpose, the present application adopts the following technical solutions: The first aspect of the present application provides a preparation method of stretchable conductor material for 3D printing of vertical interconnection wire in multi-layer stretchable electronic device, comprising: The elastomer matrix, inhibitor, coupling agent and rheological modifier are mixed uniformly, then flow aids are added, mixed uniformly and vacuum degassed synchronously to obtain an organic carrier; The flocculent silver particles are added to the dispersant and ultrasonically dispersed to obtain a flocculent silver particle dispersion; The organic carrier and flocculent silver particle dispersion are mixed uniformly, two-stage stirring and vacuum degassing synchronously to obtain a stretchable conductor material; The dispersant has a boiling point range of 60-100 DEG C and is miscible with the organic carrier; The mass fraction of the flocculent silver particles in the stretchable conductor material is 50-80%.

[0009] The prepared stretchable conductor material can have high conductivity, high stretchability, low electrical hysteresis, good compatibility with the substrate, and can realize direct forming of vertical interconnection wire through 3D printing process.

[0010] The preparation method of the stretchable conductor material of the present application comprises the following features: First-stage regulation (dispersion): a dispersant with a specific boiling point is used to ultrasonically disperse the flocculent silver powder in a solvent containing the dispersant, to realize primary deagglomeration of the flocculent silver powder and obtain a dispersion solution.

[0011] Second-stage control (finalization): The elastomer matrix, rheology modifier, silane coupling agent, flow aid, and inhibitor are mixed evenly in a specific ratio, followed by vacuum degassing to obtain the organic carrier. The dispersion solution is then ground and stirred with the organic carrier. Since the dispersant has a boiling point range of 60-100℃ and is miscible with silicone rubber, it helps to temporarily reduce the viscosity of the system and promotes the effective dispersion of flocculent silver powder in the organic carrier. Subsequently, by controlling the temperature during grinding and stirring, after the dispersant evaporates, the inorganic rheology modifier can form a strong thixotropic network with the silicone rubber, allowing VIA to be directly printed.

[0012] A second aspect of the present invention provides a stretchable conductor material prepared by the method described above.

[0013] This invention provides a silver-based stretchable conductor material that combines high conductivity, high stretchability, low electrical hysteresis, and low-temperature curing properties. It can also be directly molded into stretchable VIAs using direct-write 3D printing, making it particularly suitable for electrical interconnections between different functional layers in multilayer stretchable electronic devices. The stretchable conductor material mainly consists of an elastomer matrix, conductive fillers, rheology modifiers, silane coupling agents, flow aids, and inhibitors.

[0014] A third aspect of the invention provides the application of the above-described stretchable conductor material in 3D-printed multilayer vertical interconnect wires.

[0015] Beneficial effects of the present invention (1) This invention develops a stretchable conductor material for 3D printing of vertical interconnect wires in multilayer stretchable electronics. By adjusting the rheological properties of the material, it can be perfectly adapted to the direct-write 3D printing process.

[0016] (2) Using flocculent silver particles (D50 300μm) with a large specific surface area and a large aspect ratio as conductive fillers solves the problem of mutual constraints between conductivity, tensile strength, and electrical hysteresis in stretchable conductors. The large specific surface area is beneficial to increasing the contact area between conductive fillers, reducing the percolation threshold, and improving conductivity, with a conductivity of up to 30,000 S / cm. Under mechanical deformation such as stretching, the large aspect ratio structure helps to maintain more conductive pathways and improve tensile strength, with a maximum stretching rate of 200%. Due to the irregular geometry of the flocculent silver particles, the mechanical friction between the conductive filler and the elastomer matrix is ​​enhanced. At the same time, the selection of specific coupling agents can better wrap around and anchor them on the surface of the flocculent silver particles. Through mechanical interlocking and chemical bonding, the interfacial bonding force between the silver particles and the elastomer is effectively enhanced, thereby effectively reducing electrical hysteresis.

[0017] (3) The developed stretchable conductor material enables direct 3D printing of VIA. The stretchable conductor material has a high storage modulus, shear thinning properties, and good thixotropic recoverability. After the material is extruded at the 3D printing nozzle, it can maintain a vertical structure without collapsing under gravity. By adjusting the printing process parameters, vertical interconnect wires of different diameters and heights can be obtained.

[0018] (4) Compared with existing silver pastes which require high-temperature sintering and curing at temperatures above 150°C, the stretchable conductor material proposed in this invention has the ability to cure at low temperatures, with a minimum curing temperature of 80°C, which effectively avoids the thermal damage that high temperatures may cause to electronic components and stretchable substrates.

[0019] (5) The printed stretchable vertical interconnect structure (VIA) has good interfacial bonding performance with the stretchable substrate layer, and the modulus of the two is similar. When the multilayer stretchable electronic device is subjected to tensile strain, the printed VIA structure can significantly alleviate the stress concentration phenomenon.

[0020] (6) The preparation method of the present invention is simple, practical and easy to promote. Attached Figure Description

[0021] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. Exemplary embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0022] Figure 1 The principle of stretchable VIA molding: (a) shear thinning properties; (b) printing process; (c) actual printing process; Figure 2 The results show the viscosity changes of stretchable conductor materials at different shear rates. Figure 3 The results show the modulus change of a stretchable conductor material under different shear stresses. Figure 4 The results of the three-stage thixotropic test of the stretchable conductor material; Figure 5 The variation of VIA cross-sectional radius under different printing speeds; Figure 6 VIA morphology changes at different printing speeds; (a) 0.1-1 mm / s, (b) 1-2 mm / s; Figure 7 Flowchart of VIA sample preparation process; Figure 8 Tensile cycle test at 50% elongation for VIA sample. Detailed Implementation

[0023] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of skill in the art. The reagents and raw materials used in this invention are readily available through conventional means, and unless otherwise specified, they are used in accordance with conventional methods in the art or product instructions. Similarly, unless otherwise specified, the test methods of this invention are performed in accordance with conventional methods in the art or industry-standard methods or practices. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to the methods of this invention. The preferred embodiments and materials described herein are for illustrative purposes only.

[0025] As shown in the background art, based on the practical application requirements of vertical interconnecting wires in multilayer stretchable electronic circuits, silver-based stretchable conductors should simultaneously meet the following properties: (1) It can meet the direct molding requirements of vertical interconnect wires (VIA) in multilayer stretchable electronics 3D printing. Therefore, the stretchable conductor material should have good thixotropic recoverability and high storage modulus. Good thixotropic recoverability and high storage modulus can enable the stretchable conductor to maintain its shape after extrusion without collapsing under gravity, thus realizing the direct molding of VIA. The stretchable conductor material should also have good rheological properties so that it can be smoothly extruded from the printing nozzle.

[0026] (2) It can meet the requirement of good interface bonding between the stretchable substrate and the stretchable VIA. Excellent interface bonding helps to ensure that the multilayer stretchable electronic device maintains stable electrical connection performance during long-term strain working cycle.

[0027] (3) Low-temperature curing performance. The stretchable conductor can be cured at low temperature (<150℃) to prevent damage to electronic components and stretchable substrate caused by high-temperature heating environment.

[0028] (4) Stretchable conductors should possess high conductivity, high stretchability, and low electrical hysteresis to meet the requirements of high-performance multilayer stretchable electronic interlayer electrical interconnection applications. Currently, the conductive fillers in silver-based stretchable conductors mainly employ spherical silver nanoparticles, silver nanosheets, silver nanowires, and combinations of two or three of these, but none of these methods have resolved the mutual constraints between conductivity, stretchability, and electrical hysteresis in stretchable conductors.

[0029] Therefore, this invention mainly proposes a method for preparing a stretchable conductor material for 3D printing of vertical interconnect wires in multilayer stretchable electronics, comprising: The elastomer matrix, inhibitor, coupling agent, and rheology modifier are mixed evenly, and then a flow aid is added. The mixture is then mixed evenly and simultaneously degassed under vacuum to obtain an organic carrier. Flocculent silver particles were added to a dispersant and ultrasonically dispersed to obtain a flocculent silver particle dispersion. The organic carrier and the flocculent silver particle dispersion were mixed evenly, and the mixture was stirred in two stages while being simultaneously degassed under vacuum to obtain a stretchable conductor material. The dispersant has a boiling point range of 60-100℃ and is miscible with the organic carrier. The flocculent silver particles account for 50-80% of the mass fraction of the stretchable conductor material. The use of flocculent silver particles has the following advantages: (1) Using flocculent silver particles (D50 300μm) with a large specific surface area and a large aspect ratio as conductive filler solves the problem of mutual constraint between conductivity, stretchability and electrical hysteresis in stretchable conductors. (2) Achieving high conductivity. The large specific surface area is conducive to increasing the mutual contact area between conductive fillers, reducing the percolation threshold and improving conductivity, with a conductivity of up to 30,000 S / cm. (3) Achieving a large stretchability. Under mechanical deformation such as stretching, the large aspect ratio structure is conducive to maintaining more conductive paths, improving stretchability, and the maximum stretchability reaches 200%. (4) Reducing electrical hysteresis. Due to the irregular geometry of the flocculent silver particles, the mechanical friction between the conductive filler and the elastomer matrix is ​​enhanced. At the same time, by selecting specific coupling agents, the particles can be better wrapped and anchored on the surface of the flocculent silver particles. Through mechanical interlocking and chemical bonding, the interfacial bonding force between the silver particles and the elastomer is effectively enhanced, thereby effectively reducing electrical hysteresis.

[0030] Preferably, the elastomer matrix is ​​a two-component liquid silicone rubber; more preferably, the two-component liquid silicone rubber is obtained by mixing silicone rubber monomers and a curing agent and then curing. The cured silicone rubber has an elongation at break greater than 250%.

[0031] The amount of elastomer matrix affects the performance of stretchable conductor materials. Therefore, this invention studies the mass fraction of elastomer matrix in stretchable conductor materials. Preferably, the mass fraction of elastomer matrix in stretchable conductor materials is 20-50% to obtain better performance.

[0032] The conductive filler is selected from flocculent silver particles with a large specific surface area and a high aspect ratio. The large specific surface area increases the contact area between the conductive fillers, reducing the seepage threshold. Simultaneously, under mechanical deformation such as tension, the irregular geometry of the flocculent silver particles enhances the mechanical friction between the conductive filler and the elastomer matrix, improving interfacial bonding and effectively reducing electrical hysteresis. Preferably, the particle size of the flocculent silver conductive filler is 100 nm-5 μm or 100-500 nm. A lower particle size facilitates high-resolution VIA printing.

[0033] Preferably, the rheology modifier is a clay mineral or nano-vaporized silica; the rheology modifier is an inorganic rheology modifier. By adjusting the amount of rheology modifier added, the storage modulus and yield stress of the stretchable conductor material can be effectively improved, which is beneficial to realizing the direct 3D printing of VIA.

[0034] The amount of rheology modifier affects the performance of stretchable conductor materials. Therefore, this invention studies the mass fraction of rheology modifier in stretchable conductor materials. Preferably, the mass fraction of rheology modifier in stretchable conductor materials is 1-7% to obtain better performance.

[0035] Preferably, the silane coupling agent is selected from at least one of KH550, KH560, KBM-403, Z-6011, and OFS-6040; the addition of the silane coupling agent can further improve the dispersibility of the conductive filler in the elastomer matrix and enhance the adhesion between the stretchable conductor and the substrate.

[0036] The amount of silane coupling agent used can affect the performance of stretchable conductor materials. Therefore, this invention studies the mass fraction of silane coupling agent in stretchable conductor materials. Preferably, the mass fraction of silane coupling agent in stretchable conductor materials is 0.5-4% to obtain better performance.

[0037] Preferably, the flow aid is selected from at least one of n-hexane, cyclohexane, undecane, and toluene; by adding an appropriate proportion of flow aid, the viscosity of the stretchable conductor material can be effectively adjusted, which is beneficial for its smooth extrusion at the nozzle. The preferred viscosity range for the stretchable conductor material at a shear rate of 0.1 1 / s is 5 × 10⁻⁶. 5 mPa·s~4×10 6 mPa·s.

[0038] The amount of flow aid can affect the performance of stretchable conductor materials. Therefore, this invention has studied the amount of flow aid. Preferably, the flow aid accounts for 5-30% of the mass fraction of the stretchable conductor material to obtain better performance.

[0039] Preferably, the inhibitor is 1-ethynylcyclohexanol; the addition of the inhibitor prevents the stretchable conductor material from undergoing a cross-linking reaction for an extended period at room temperature. When the heating temperature reaches the boiling point of the inhibitor, the inhibitor rapidly volatilizes, and the stretchable conductor quickly cross-links and solidifies.

[0040] The amount of inhibitor used can affect the performance of stretchable conductor materials. Therefore, this invention has studied the amount of inhibitor used. Preferably, the inhibitor accounts for 0.5-3% of the mass fraction of the stretchable conductor material to obtain better performance.

[0041] The present invention will be further described in detail below with reference to specific embodiments. It should be noted that the specific embodiments are explanations of the present invention and not limitations thereof.

[0042] Viscosity was measured using a German HAAKE MARS 40 rotational rheometer. The shear rate was set to 0.1-100 1 / s at a constant temperature to test the viscosity change of the material under different shear rates.

[0043] Conductivity was tested using a digital four-probe tester (Changzhou Anbo Precision Instruments Co., Ltd. AT516).

[0044] The modulus was tested using a German HAAKE MARS 40 rotational rheometer in dynamic oscillation mode. The shear strain was set to 0.01%-100%, which yielded the changes in the material's storage modulus and loss modulus under different shear stresses.

[0045] In the following examples and comparative examples, the flocculent silver particles were purchased from Fujian Fuxuan Technology Co., Ltd., CAg series.

[0046] Example 1 A stretchable conductor material for 3D printing vertical interconnect wires in multilayer stretchable electronics and its preparation method, comprising the following steps: (1) Preparation of organic carrier. PDMS (Dow Corning 184) was used as the elastomer matrix, and AEROSIL R106 hydrophobic fumed silica from Evonik GmbH was used as the rheology modifier. The PDMS monomer and curing agent were mixed uniformly at a weight ratio of 10:1, and then vacuum-treated to obtain the elastomer matrix. 20 g of the elastomer matrix was taken, and 0.1 g of 1-ethynylcyclohexanol inhibitor (boiling point 100℃), 1 g of KH560 coupling agent, and 0.6 g of fumed silica were added sequentially. After thorough stirring, 8.8 g of cyclohexane was added to adjust the overall viscosity of the system. The above mixture was thoroughly stirred in a planetary mixer and vacuum degassing was performed simultaneously (3000 r / min, 10 min) to finally obtain a uniform and stable organic carrier.

[0047] (2) Ultrasonic dispersion of flocculent silver particles. Using hexane (boiling point ~69℃) as a dispersant, 70g of flocculent silver particles were added to 200g of hexane solvent and ultrasonically dispersed for 30min using an ultrasonic cell disruptor at 1000W to obtain a well dispersed mixed solution.

[0048] (3) Stirring and Vacuum Degassing Treatment. The organic carrier and the dispersed mixture were initially stirred, and then transferred to a temperature-controlled double planetary mixer for high-shear stirring and vacuum degassing treatment. The double planetary mixer adopted a two-stage operating program: the first stage was at a speed of 1000 r / min for 2 min; the second stage was at a speed of 3000 r / min for 8 min, with a total operating time of 1 hour. The temperature was controlled below 80 ℃ during the treatment to promote the full volatilization of n-hexane, and finally a uniform stretchable conductor material with a silver content of 70 wt% was obtained.

[0049] The viscosity of the stretchable conductor material is 1.2 × 10⁻⁶. 5 After curing at 120℃ for 45 min, the conductivity was 28000 S / cm at mPa·s. Subsequently, 3D printing tests were conducted on the stretchable conductor material. It was loaded into a 10ml cartridge and printed using a dispensing needle with an inner diameter of 350 micrometers. The VIA printing speed was set to 2 mm / s, and float glass was selected as the printing substrate. The substrate was heat-treated at 120℃. The VIA printing results are as follows. Figure 1 As shown, the surface of the printed result is a stretchable conductor material that can be directly 3D printed into VIA.

[0050] Example 2 A stretchable conductor material for 3D printing vertical interconnect wires in multilayer stretchable electronics and its preparation method, comprising the following steps: (1) Preparation of organic carrier. Reinforced liquid silicone rubber (containing MQ resin) was used as the elastomer matrix, and AEROSIL R106 hydrophobic fumed silica from Evonik Industries, Germany, was used as the rheology modifier. The silicone rubber monomer and curing agent were mixed uniformly at a weight ratio of 10:1, and then vacuum-treated to obtain the elastomer matrix. 25 g of the elastomer matrix was taken, and 0.2 g of 1-ethynylcyclohexanol inhibitor (boiling point 120℃), 1 g of OFS-6040 coupling agent, and 0.8 g of fumed silica were added in sequence. After thorough stirring, 9 g of cyclohexane was added to adjust the overall viscosity of the system. The above mixture was thoroughly stirred in a planetary mixer and vacuum degassing was carried out simultaneously (3000 r / min, 10 min) to finally obtain a uniform and stable organic carrier.

[0051] (2) Ultrasonic dispersion of flocculent silver particles. Tetrahydrofuran was used as a dispersant. 65g of flocculent silver particles were added to 120g of tetrahydrofuran solvent and ultrasonically dispersed for 30min using an ultrasonic cell disruptor at 1000W to obtain a well dispersed mixed solution.

[0052] (3) Stirring and Vacuum Degassing Treatment. The organic carrier and the dispersed mixture were initially stirred, and then transferred to a temperature-controlled double planetary mixer for high-shear stirring and vacuum degassing treatment. The double planetary mixer adopted a two-stage operating program: the first stage was at a speed of 1000 r / min for 2 min; the second stage was at a speed of 3000 r / min for 8 min, with a total operating time of 1 hour. The temperature was controlled below 80 ℃ during the treatment to promote the full volatilization of tetrahydrofuran, and finally a uniform stretchable conductor material with a silver content of approximately 65 wt% was obtained.

[0053] The rheological properties of the stretchable conductor material were then tested. At a shear rate of 0.1 1 / s, the viscosity of the material was 2.6 × 10⁻⁶. 6 mPa·s, such as Figure 2 As shown. Figure 3 Data on modulus changes under different shear stresses show that in the low shear stress region (0-170 Pa), the storage modulus (G′) is significantly higher than the loss modulus (G″), which is crucial for the direct forming and shape retention of vertical interconnect wires during 3D printing. When the shear stress exceeds 230 Pa, the material's viscous properties outperform its elastic properties, resulting in flow behavior that facilitates smooth extrusion from the nozzle and reduces nozzle clogging.

[0054] 3D printing tests were conducted by loading the material into a 10ml cartridge and printing using a dispensing needle with an inner diameter of 350 micrometers. The printing pressure was fixed at 300 kPa. PDMS film was selected as the printing substrate, which was then heated to 130℃. The VIA printing results at printing speeds of 0.1 mm / s–2 mm / s are shown below. Figure 5 and Figure 6 As shown, the surface stretchable conductor material of the printed result can achieve direct 3D printing of VIA structures with different diameters.

[0055] Example 3 A stretchable conductor material for 3D printing vertical interconnect wires in multilayer stretchable electronics and its preparation method, comprising the following steps: (1) Preparation of organic carrier. Ecoflex was used as the elastomer matrix, and AEROSIL R106 hydrophobic fumed silica from Evonik GmbH was used as the rheology modifier. The silicone rubber monomer and curing agent were mixed uniformly at a weight ratio of 1:1, and then vacuum-treated to obtain the elastomer matrix. 10 g of the elastomer matrix was taken, and 0.1 g of 1-ethynylcyclohexanol inhibitor (boiling point 130℃), 0.5 g of OFS-6040 coupling agent, and 0.5 g of fumed silica were added in sequence. After thorough stirring, 4 g of cyclohexane was added to adjust the overall viscosity of the system. The mixture was thoroughly stirred in a planetary mixer and vacuum degassing was performed simultaneously (3000 r / min, 20 min) to finally obtain a uniform and stable organic carrier.

[0056] (2) Ultrasonic dispersion of flocculent silver particles. Tetrahydrofuran was used as a dispersant. 28g of flocculent silver particles were added to 60g of n-hexane solvent and ultrasonically dispersed for 30min using an ultrasonic cell disruptor at 1000W to obtain a well dispersed mixed solution.

[0057] (3) Stirring and Vacuum Degassing Treatment. The organic carrier and the dispersed mixture were initially stirred, and then transferred to a temperature-controlled double planetary mixer for high-shear stirring and vacuum degassing treatment. The double planetary mixer adopted a two-stage operating program: the first stage was at a speed of 1000 r / min for 2 min; the second stage was at a speed of 3000 r / min for 8 min, with a total operating time of 1 hour. During the operation, hexane was fully volatilized, and a uniformly mixed stretchable conductor material was finally obtained.

[0058] This invention tested the electrical stability of the stretchable VIA structure after subjected to multiple tensile strains. The VIA sample fabrication process flow diagram is shown below. Figure 7 As shown, the prepared sample underwent a 500-cycle tensile test at a 50% elongation rate: the VIA sample terminals were connected to a resistance tester, and then the sample was placed in the tensile cycle testing machine fixture for a 50% elongation rate tensile cycle test, with the tensile speed set to 10 mm / s. The resistance values ​​recorded by the resistance tester during the tensile process were exported and plotted. The test results are shown below. Figure 8 As shown, the results indicate that the initial resistance value and the maximum resistance value remain basically stable during each stretching, verifying that the VIA structure can maintain a stable mechanical structure and resistance change during repeated stretching / releasing, making it suitable for interlayer electrical interconnection in multilayer stretchable electronic devices.

[0059] Comparative Example 1 The difference from Example 1 is that the dispersant used is diethyl ether (boiling point approximately 34.6°C). Because its boiling point is much lower than the stirring and vacuum degassing process temperature, it easily undergoes violent vaporization in the initial mixing stage, disrupting the uniform dispersion of silver powder in the silicone rubber matrix, leading to silver particle agglomeration and damaging the continuity of the conductive network. Furthermore, the rapidly generated large number of bubbles are difficult to completely remove, resulting in numerous microporous defects remaining inside the final product, reducing its mechanical strength. After thermosetting at 120°C for 45 min, the prepared material has a volume conductivity of only 1.5 × 10⁻⁶. 4 S / cm, with a maximum elongation of only 60% (significantly lower than the maximum elongation of 200% in Example 1).

[0060] Comparative Example 2 The difference from Example 1 is that the dispersant is xylene (boiling point approximately 138°C). Due to its high boiling point, it is difficult to volatilize effectively during the stirring and vacuum degassing process of the stretchable conductor material, resulting in a lower viscosity of the prepared material (approximately 3 × 10⁻⁶). 3 The xylene content (mPa·s) caused over-spreading during 3D printing, affecting printing accuracy. Furthermore, residual xylene diluted the silver-based solid phase content, resulting in a volume conductivity of only 1.0 × 10⁻⁶ after thermosetting at 120°C for 45 min. 4 S / cm decreased significantly compared to Example 1.

[0061] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a stretchable conductor material for 3D printing vertical interconnect wires in multilayer stretchable electronics, characterized in that, include: The elastomer matrix, inhibitor, coupling agent, and rheology modifier are mixed evenly, and then a flow aid is added. The mixture is then mixed evenly and simultaneously degassed under vacuum to obtain an organic carrier. Flocculent silver particles were added to a dispersant and ultrasonically dispersed to obtain a flocculent silver particle dispersion. The organic carrier and the flocculent silver particle dispersion were mixed evenly, and the mixture was stirred in two stages while being simultaneously degassed under vacuum to obtain a stretchable conductor material. The dispersant has a boiling point range of 60-100℃ and is miscible with the organic carrier. The flocculent silver particles account for 50-80% of the mass fraction of the stretchable conductor material.

2. The method for preparing a stretchable conductor material for 3D printing vertical interconnect wires in multilayer stretchable electronics as described in claim 1, characterized in that, The elastomer matrix is ​​a two-component liquid silicone rubber; Alternatively, the two-component liquid silicone rubber is obtained by mixing silicone rubber monomers and a curing agent and then curing them.

3. The method for preparing a stretchable conductor material for 3D printing vertical interconnect wires in multilayer stretchable electronics as described in claim 1, characterized in that, The elastomer matrix accounts for 20-50% of the mass fraction of the stretchable conductor material.

4. The method for preparing a stretchable conductor material for 3D printing vertical interconnect wires in multilayer stretchable electronics as described in claim 1, characterized in that, The particle size of the flocculent silver conductive filler is 100 nm-5 μm or 100-500 nm.

5. The method for preparing a stretchable conductor material for 3D printing vertical interconnect wires in multilayer stretchable electronics as described in claim 1, characterized in that, The rheology modifier is a clay mineral or nano-fumed silica; Alternatively, the rheology modifier may account for 1-7% of the mass fraction of the stretchable conductor material.

6. The method for preparing a stretchable conductor material for 3D printing vertical interconnect wires in multilayer stretchable electronics as described in claim 1, characterized in that, The silane coupling agent is selected from at least one of KH550, KH560, KBM-403, Z-6011, and OFS-6040; Alternatively, the silane coupling agent may account for 0.5-4% of the mass fraction of the stretchable conductor material.

7. The method for preparing a stretchable conductor material for 3D printing vertical interconnect wires in multilayer stretchable electronics as described in claim 1, characterized in that, The flow aid is selected from at least one of n-hexane, cyclohexane, undecane, and toluene; Alternatively, the flow aid may constitute 5-30% of the mass fraction of the stretchable conductor material.

8. The method for preparing a stretchable conductor material for 3D printing vertical interconnect wires in multilayer stretchable electronics as described in claim 1, characterized in that, The inhibitor is 1-ethynylcyclohexanol; Alternatively, the inhibitor may constitute 0.5-3% of the mass of the stretchable conductor material.

9. The stretchable conductor material prepared by the method according to any one of claims 1-8.

10. The application of the stretchable conductor material of claim 9 in 3D printing of multilayer vertical interconnect wires.

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