CN115359949B - Conductive microsphere, stretchable conductor and preparation method thereof - Google Patents
Conductive microsphere, stretchable conductor and preparation method thereof Download PDFInfo
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Abstract
本发明涉及一种导电微球、可拉伸导体及其制备方法，属于柔性电子领域。本发明提供一种可拉伸导体，所述可拉伸导体包括封装层和置于封装层内部的导电微球；其中，所述导电微球为以高分子弹性体微球为核，导电填料为壳形成的具有核壳结构的微球。本发明提供的新型可拉伸导体，具有高电导率、大应变下高电导率保持和软的力学特征；制得的具有密堆积结构的可拉伸导体具有更优异的性能：初始电导率可达67185S/cm，断裂伸长率为602％，在高达445％的拉伸应变下保持到>100S/cm的高电导率；在1％应变下的弹性模量为0.53MPa。
The present invention relates to a conductive microsphere, a stretchable conductor and a preparation method thereof, and belongs to the field of flexible electronics. The present invention provides a stretchable conductor, the stretchable conductor comprising an encapsulation layer and a conductive microsphere disposed inside the encapsulation layer; wherein the conductive microsphere is a microsphere having a core-shell structure formed by a polymer elastomer microsphere as a core and a conductive filler as a shell. The novel stretchable conductor provided by the present invention has high conductivity, high conductivity retention under large strain and soft mechanical characteristics; the obtained stretchable conductor with a densely packed structure has more excellent performance: the initial conductivity can reach 67185S/cm, the elongation at break is 602%, and the high conductivity of >100S/cm is maintained under a tensile strain of up to 445%; the elastic modulus under 1% strain is 0.53MPa.
Description
Technical Field
The invention relates to a conductive microsphere, a stretchable conductor and a preparation method thereof, belonging to the field of flexible electronics.
Background
Stretchable conductors are a material that maintains high electrical conductivity under stretching conditions, the most fundamental of which is to maintain high electrical conductivity under strain conditions to ensure undisturbed operation of the electronic components to which they are attached under complex deformation conditions. Therefore, stretchable conductors play an irreplaceable role in the fields of flexible displays, stretchable batteries, electronic skin, soft robots, and the like.
The traditional method for preparing the stretchable conductor is to directly fill conductive components such as metal nano particles or nano wires into an elastic polymer matrix, and further process the conductive components into the stretchable conductor in different forms such as fibers, films or ink, but the stretchable conductor has certain disadvantages. For example, the introduction of a large amount of conductive filler greatly reduces the stretchability of the material due to the high volume filler content required to reach the percolation value, and in addition, the surface of the conductive component is always surrounded by an insulating polymer matrix layer due to the limitation of processing conditions during blending. The polymer insulation inhibits the efficient transport of electrons, resulting in a decrease in conductivity of the stretchable conductor of several orders of magnitude compared to the filler itself, and finally, the high volume filling of the rigid conductive component inevitably strengthens the polymer matrix, resulting in a significant modulus increase exhibited by the final composite.
To solve the above problems, the choice of a "soft" conductive component filled polymer elastomer appears to be able to impart satisfactory properties to the conductor. For example, many liquid metal filled polymer composites are currently being investigated, which utilize the flowability and conductivity of the liquid metal itself to enable the final conductor to exhibit low modulus, high draw ratio, and strain-enhanced conductivity, etc. This "soft" solution is an important idea to solve the above problems, but the fluid properties of the liquid metal itself make it very easy to migrate and leak under dynamic strain, and it is also very difficult to form a well compatible stable interface with other electronic components.
Disclosure of Invention
Based on the defects, the invention aims to provide a novel stretchable conductor (conductive soft filler), which is prepared by encapsulating conductive microspheres by a flexible material, wherein the conductive microspheres are microspheres with core-shell structures formed by a high polymer elastomer and the conductive filler, and the obtained stretchable conductor has high conductivity, high conductivity retention under large strain and soft mechanical characteristics.
The technical scheme of the invention is as follows:
The invention provides a stretchable conductor, which comprises a packaging layer and conductive microspheres arranged in the packaging layer, wherein the conductive microspheres are microspheres with core-shell structures, which are formed by taking polymer elastomer microspheres as cores and conductive fillers as shells.
Further, the polymer elastomer includes silicone rubber, natural rubber, polyurethane elastomer, styrene-butadiene-styrene rubber, ethylene-octene rubber, etc.
Further, the packaging layer material is high-elasticity resin.
Still further, the highly elastic resin includes Ecoflex series elastomer, polyurethane elastomer, polybutadiene, polyisoprene, butyl rubber, ethylene-propylene copolymer elastomer or styrene-butadiene rubber. The high elastic resin and the high molecular elastomer may be the same.
Further, the conductive filler comprises conductive metal, carbon-based conductive material and conductive polymer material.
Further, the conductive metal comprises silver, copper or nickel, the carbon-based conductive material comprises graphene or carbon nanotubes and the like, and the conductive polymer material comprises polypyrrole, polythiophene or polyaniline.
The conductive microsphere is prepared by preparing a high polymer elastomer microsphere, and then firmly coating a conductive filler on the surface of the high polymer elastomer to form the microsphere with a core-shell structure.
The preparation method of the conductive microsphere comprises the steps of synthesizing the high-molecular elastomer microsphere by adopting a suspension polymerization mode, placing the high-molecular elastomer microsphere into a conductive filler (such as carbon conductive filler) solution or a solution containing a conductive filler precursor (such as conductive metal or conductive high-molecular material) to enable the conductive filler or the conductive filler precursor to be swelled and fully absorbed, and then applying a reducing agent or converting the precursor into the conductive filler by polymerization to obtain the conductive microsphere with the core-shell structure.
In order to improve the conductivity of the stretchable conductor, the conductive microspheres with core-shell structures can be further subjected to the following treatment before being packaged, wherein the conductive microspheres with core-shell structures are closely pulled together by a solvent evaporation method to form microspheres with closely-packed three-dimensional network structures.
Furthermore, the method for processing the conductive microspheres before packaging comprises the steps of dispersing the conductive microspheres with core-shell structures in a solvent, volatilizing the solvent at room temperature, and generating a liquid bridge between adjacent microspheres due to solvent volatilization, wherein the local stress generated by the liquid bridge can reach kilopascals or even megapascals, and is enough to pull the adjacent microspheres together, so that the conductive microspheres with closely packed three-dimensional conductive networks are formed by solvent volatilization induction. The liquid bridge refers to a small liquid column between solids, i.e. a section of liquid that connects between two solid surfaces.
Further, in the treatment process performed before packaging the conductive microspheres, the mass ratio of the conductive microspheres to the solvent is 1:2-1:10, for example, 1:2, 1:4, 1:6, 1:8 and 1:10 can be adopted.
Further, in the treatment process performed before the encapsulation of the conductive microspheres, the solvent is at least one of methanol, ethanol, chloroform, water, acetone or n-heptane.
The second technical problem to be solved by the invention is to provide a preparation method of the stretchable conductor, wherein the preparation method is to encapsulate the conductive microspheres by adopting an encapsulation material.
The preparation method of the stretchable conductor comprises the steps of firstly preparing high-molecular elastomer microspheres, then firmly coating conductive filler on the surface of the high-molecular elastomer to form the microspheres with core-shell structures, and finally packaging by using packaging materials.
The preparation method of the stretchable conductor comprises the steps of firstly preparing high polymer elastomer microspheres, then firmly coating conductive filler on the surface of the high polymer elastomer to form microspheres with core-shell structures, dispersing the conductive microspheres with the core-shell structures in a solvent, volatilizing the solvent at room temperature, generating a liquid bridge between adjacent microspheres due to solvent volatilization, and pulling the adjacent microspheres together by local stress generated by the liquid bridge to kilopascals or even megapascals, so that the conductive microspheres with closely stacked three-dimensional conductive networks are formed by solvent volatilization induction, and finally packaging the conductive microspheres by packaging materials.
Further, when the polymer elastomer and the encapsulation material are silicone rubber and the conductive filler is conductive metal, the preparation method of the stretchable conductor comprises the following steps:
1) Synthesizing high molecular elastomer microsphere by suspension polymerization;
2) Activating the polymer elastomer microsphere, immersing the polymer elastomer microsphere in a conductive metal precursor solution to fully swell the polymer elastomer and adsorb the conductive metal precursor, and then adding a reducing agent to reduce metal ions into metal simple substances to prepare the conductive microsphere with a core-shell structure;
3) Dispersing the obtained conductive microspheres in a solvent, pouring the solvent into a mold for drying, volatilizing the solvent to cause the conductive microspheres to form conductive microspheres with close-packed three-dimensional conductive networks, pouring a packaging material for packaging and curing, thus obtaining the stretchable conductor.
Further, in step 2), the conductive metal precursor solution may be selected from a tetrahydrofuran solution or an isopropanol solution containing silver trifluoroacetate.
Further, in step 2), the reducing agent is hydrazine hydrate, ascorbic acid, sodium citrate or sodium sulfite.
In the step 2), the method for activating the polymer elastomer microspheres before immersing the polymer elastomer microspheres in the conductive metal precursor solution comprises the steps of treating the polymer elastomer microspheres in a plasma environment for 10-30 min (30 min) and with power of 200-600W (600W).
Further, in the step 3), the solvent is at least one selected from methanol, ethanol, chloroform, water, acetone or n-heptane, and preferably, the solvent is water. Here, a solvent which does not swell the polymer elastomer and has a large surface tension is selected.
Further, in the step 3), the mass ratio of the conductive microspheres to the solvent is 1:2-1:10, for example, 1:2, 1:4, 1:6, 1:8 and 1:10, and the final effect is not obviously different.
The third technical problem to be solved by the invention is to provide a preparation method of the conductive microsphere, which comprises the steps of firstly preparing a high polymer elastomer microsphere, then firmly coating a conductive filler on the surface of the high polymer elastomer to form a microsphere with a core-shell structure by taking the high polymer elastomer microsphere as a core and taking the conductive filler as a shell (namely coating the conductive filler on the surface of the high polymer elastomer microsphere).
The preparation method of the conductive microsphere comprises the steps of synthesizing the high-molecular elastomer microsphere by adopting a suspension polymerization mode, placing the high-molecular elastomer microsphere into a conductive filler (such as carbon conductive filler) solution or a solution containing a conductive filler precursor (such as conductive metal or conductive high-molecular material) to enable the conductive filler or the conductive filler precursor to be swelled and fully absorbed, and then applying a reducing agent or converting the precursor into the conductive filler by polymerization to obtain the conductive microsphere with the core-shell structure.
Further, when the polymer elastomer is silicon rubber and the conductive filler is metal, the preparation method of the conductive microsphere comprises the steps of firstly synthesizing the polymer elastomer microsphere in a suspension polymerization mode, then activating the surface of the polymer elastomer microsphere, then soaking the activated polymer elastomer microsphere in a conductive metal precursor solution to enable the polymer elastomer to fully swell and adsorb the conductive metal precursor, and finally reducing the conductive metal precursor to obtain the conductive microsphere.
Further, when the polymer elastomer is silicone rubber and the conductive filler is metal, the preparation method of the conductive microsphere comprises the following steps:
(1) Adding an organic solvent (diluent) into liquid silicone rubber (Sylgard 184) to obtain liquid silicone rubber mixed solution, wherein the content of the diluent is 0% -20% (volume ratio) of the liquid silicone rubber;
(2) Slowly dripping the silicon rubber mixed solution obtained in the step (1) into a poor solvent with high-speed shearing, then heating to 40-90 ℃ and reducing the shearing rate to continue the reaction, wherein the volume ratio of the poor solvent to the silicon rubber precursor mixed solution is 4:1-20:1 and is preferably 10:1, the high-speed shearing rate is 5000-18000 rpm and is preferably 15000rpm, the high-speed shearing time is 5-20 min and is preferably 10min, the shearing rate is reduced to 500-1000 rpm and is preferably 1000rpm, and the shearing time is 10-60 min and is preferably 30 min;
(3) Carrying out suction filtration and drying on the solution obtained in the step (2) to obtain silicon rubber microspheres, treating the microspheres in a plasma environment for 5-30 min, and activating the surfaces of the microspheres for later use;
(4) Swelling the silicon rubber microspheres obtained in the step (3) in a conductive metal precursor solution, adsorbing the conductive metal precursor for 5-50 min, and then dropwise adding a reducing agent solution to fully reduce metal ions;
(5) And (3) carrying out suction filtration on the solution obtained in the step (4), washing the solution with deionized water for at least 3 times, and drying the solution to obtain the polymer elastomer/conductive filler microsphere (such as silicon rubber@silver microsphere) with a core-shell structure.
Further, in the step (1), the organic solvent for diluting the silicone rubber is selected from one of n-hexane, isopropanol, tetrahydrofuran, methylene chloride and xylene. Preferably, the diluent is isopropanol or tetrahydrofuran, more preferably n-hexane.
In the step (4), the time for adsorbing the conductive metal precursor solution by the silicone rubber microspheres is 5-50 min, for example, 5,10,15,20,25,30,35,40,45, and 50min, and preferably, the precursor adsorption time is 40min.
The invention has the beneficial effects that:
The invention provides a novel stretchable conductor, which is prepared by encapsulating conductive microspheres by a flexible material, wherein the conductive microspheres are microspheres with core-shell structures formed by a high polymer elastomer and conductive fillers, and the obtained stretchable conductor has the mechanical characteristics of high conductivity, high conductivity retention under large strain and softness. The stretchable conductor with the close-packed structure has more excellent performance, namely the initial conductivity can reach 67185S/cm, the elongation at break is 602%, the high conductivity of >100S/cm is kept under the tensile strain of 445%, and the elastic modulus under the strain of 1% is 0.53MPa.
Drawings
Fig. 1 shows an electron microscope and an element distribution diagram of the conductive microsphere with a core-shell structure obtained in example 4, and fig. 1 shows that the synthesized silicon rubber @ silver microsphere has a regular spherical morphology, and a layer of compact silver nanoparticles is coated on the surface of the microsphere.
Fig. 2 shows the morphology of the microsphere conductive network (left side of fig. 2) of the close-packed (example 4) and loose-packed (example 5) stretchable conductors and the corresponding conductivity result (right side of fig. 2), wherein the close-packed conductive network is compact in packing of the microspheres to form a structure similar to hexagonal close-packed structure, the microspheres are mainly in physical contact, polymer insulation layers are fewer, the structure is favorable for conducting electrons between the microspheres in an ohmic conduction mode, the conductivity of the conductors is improved, the distance between the microspheres in the loose-packed structure is far, a polymer matrix insulation layer exists between the microspheres, the existence of the insulation layer can enable the transfer of electrons from ohmic conduction to tunnel transition, so that the conductivity is reduced, and the initial conductivity of the stretchable conductors with the close-packed result can reach 67185S/cm and is higher by an order of magnitude than that of the initial conductivity of the conductors with the non-close-packed result according to the conductivity test result.
Fig. 3 is a graph showing evolution of the conductive network under stretching (strain of 0-400%) of the close-packed stretchable conductor obtained in example 4 (stretching direction is horizontal direction), and from fig. 3, it is known that the volume of the silicone rubber is almost unchanged under stretching (poisson ratio of 0.5), so that the close-packed conductive network can be well maintained under high strain, the conductive network structure is almost unchanged under 200% strain, cracks and gaps appear under 300% strain, but the conductive network formed by the microspheres in the stretching direction is still continuous, the conductive network is not obviously destroyed until 400% of the conductive network is damaged, and conductivity is drastically reduced after further stretching.
Fig. 4 shows the results of initial conductivity and conductivity under strain of the stretchable conductor, as shown in fig. 4, example 4 was still able to maintain a higher conductivity under tension, 820S/cm at 400% strain, 100S/cm at 445% strain, wherein example 1 was an activated silicone rubber microsphere immersed in silver ink for 10min, example 2 was an activated silicone rubber microsphere immersed in silver ink for 20min, and so on to example 4, and example 5 was a change in conductivity under strain of the stretchable conductor with loosely packed conductive network.
FIG. 5 shows the tensile stress-strain curves of pure Sylgard 184 silicone rubber and pure Ecoflex 0050 silicone rubber, and the close-packed stretchable conductors obtained in examples 1 to 5. As can be seen from FIG. 5, the elongation at break and tensile strength of the pure Ecoflex matrix were 940% and 2.9MPa, respectively, the conductivity was reduced from 940% to 843% after the introduction of the close-packed silicone rubber @ silver microspheres, and was reduced to 602% with the extension of the silver precursor adsorption time, the elongation at break and tensile strength of the stretchable conductors obtained in example 4 were 602% and 4.3MPa, respectively, and the elongation at break and tensile strength of the stretchable conductors obtained in example 5 were 698% and 3.6MPa, respectively.
Fig. 6 shows the tensile modulus of the stretchable conductors and the silicone rubber obtained in examples 1 to 5, and it is understood from fig. 6 that the stretchable conductors obtained in the present invention exhibit "soft" mechanical behavior.
Detailed Description
The invention provides a novel stretchable conductor, which is prepared by encapsulating conductive microspheres by a flexible material, wherein the conductive microspheres are microspheres with three-dimensional conductive network structures formed by high polymer elastomers and conductive fillers, and the obtained stretchable conductor has the mechanical characteristics of high conductivity, high conductivity retention under large strain and softness.
Preferably, a three-dimensional close-packed conductive network can be constructed by solvent evaporation to induce close-packed "soft" conductive microspheres, which then cast an elastomeric matrix that also exhibits the ability to remain tightly connected under strain, thereby allowing the conductor to exhibit better conductivity and stability. The key point of the high-conductivity stretchable soft conductor is that the silicon rubber@silver microspheres with a core-shell structure and the volatilizing-induced conductive microspheres are prepared through close packing, wherein the synthesized silicon rubber microspheres are placed in silver ink for different time and reduced to prepare silver-plated microspheres in the first step, the silver-plated microspheres are dispersed in a solvent, the solvent volatilizes to cause close packing of the microspheres, and then the Ecoflex 0050 silicon rubber with high stretchability is poured, wherein the two silicon rubbers are similar in polarity, good in compatibility and free from interface compatibility problem, so that the soft conductor with high elongation at break is obtained.
Embodiments of the present invention will be described in detail below with reference to examples, but it will be understood by those skilled in the art that the following examples are only for illustrating the present invention and should not be construed as limiting the scope of the present invention. The specific conditions are not noted in the examples and are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or apparatus used were conventional products available commercially without the manufacturer's attention.
Examples 1-4 preparation of stretchable conductors with close-packed conductive networks
1. Elastic microsphere of synthetic silicon rubber
The method comprises the steps of adding 4mL of normal hexane to 22mL of liquid silicone rubber precursor (brand: sylgard 184, manufacturer: dow Corning) comprising AB two components (namely a liquid matrix and a curing agent), completely mixing the liquid matrix and the curing agent in a weight ratio of 10:1 when the liquid matrix and the curing agent are used to dilute the precursor mixed solution, slowly injecting the uniform mixed solution into 200mL of 70 ℃ warm water through a syringe needle (10G), maintaining the warm water at a high speed (15000 rpm) during injection, tearing the continuous silicone rubber precursor mixture under a strong shearing environment, breaking into micrometer particles with slow curing, transferring the system to mechanical stirring at 1000rpm for 30min after 15min, finally, pumping the solution to obtain silicone rubber microspheres, washing the silicone rubber microspheres with deionized water for multiple times, and drying and storing the silicone rubber microspheres at 60 ℃.
2. Preparation of core-shell silicon rubber @ silver microspheres
Firstly, preparing AgCF 3 COO/THF solution (silver ink) with the concentration of Ag + being 800mg/mL, treating the pre-dried silicon rubber microsphere in an air plasma environment for 30min (600W) to activate the surface of the pre-dried silicon rubber microsphere (the surface is not activated and a conductive silver layer cannot be firmly combined on the surface of the microsphere and is easy to fall off), then, respectively soaking the activated silicon rubber microsphere in the silver ink for 10min (example 1), 20min (example 2), 30min (example 3) and 40min (example 4) to fully swell and adsorb a silver precursor, then, dripping an ethanol solution (with the volume ratio of 1:1 diluted) of hydrazine hydrate into a microsphere solution with the silver precursor adsorbed by the silver precursor to reduce Ag + in the microsphere into elemental silver to obtain silicon rubber@silver microsphere, washing the silicon rubber@silver microsphere with deionized water for multiple times, and thoroughly drying at 60 ℃ to obtain the silicon rubber@silver microsphere with a core-shell structure.
3. Preparation of stretchable flexible conductors with close-packed structures
Dispersing silicon rubber @ silver microspheres in deionized water at a mass ratio of 1:10 (the mass ratio of the microspheres to the deionized water), pouring the solution into a polytetrafluoroethylene mold (length, width, height, 100mm, 10 mm), volatilizing the solvent at room temperature, wherein a liquid bridge is generated between adjacent microspheres due to solvent volatilization, the local stress (> 13 KPa) caused by the liquid bridge is enough to pull the adjacent particles together, thereby realizing solvent volatilization induction to form the silicon rubber @ silver microspheres with a three-dimensional close-packed conductive network, then preparing a precursor solution by mixing Ecoflex 0050 silicon rubber mixture (manufacturer: smooth-On) at room temperature, slowly pouring the precursor solution into the mold deposited with the close-packed conductive microspheres, fully penetrating gaps between the microspheres, and transferring the mold to a vacuum condition, and curing the mold for 24 hours at a temperature of 25 ℃ to obtain the stretchable conductor.
Example 5 preparation of stretchable conductors with loosely stacked conductive networks
1. Elastic microsphere of synthetic silicon rubber
The method comprises the steps of adding 4mL of n-hexane to 22mL of liquid silicone rubber precursor (brand: sylgard 184, manufacturer: dow Corning) comprising two components of AB (namely a liquid matrix and a curing agent) and completely mixing the liquid matrix and the curing agent in a weight ratio of 10:1 when the liquid matrix and the curing agent are used to dilute the precursor mixed solution, slowly injecting the uniform mixed solution into 200mL of 70 ℃ warm water through a syringe needle (10G) and maintaining high-speed shearing (15000 rpm) during injection, tearing the continuous silicone rubber mixture into micrometer particles under a strong shearing environment, crushing the micrometer particles and carrying out slow curing, transferring the system to mechanical stirring at 1000rpm for 30min after 15min, and finally collecting silicone rubber microspheres by suction filtration solution, washing the silicone rubber microspheres with deionized water for multiple times, and drying and storing the silicone rubber microspheres at 60 ℃.
2. Preparation of core-shell silicon rubber @ silver microspheres
Firstly, preparing AgCF 3 COO/THF solution (silver ink) with the concentration of Ag + being 800mg/mL, treating the pre-dried microspheres in an air plasma environment for 30min (600W) to activate the surfaces of the microspheres, then soaking the activated silicone rubber microspheres in the silver ink for 40min to fully swell and adsorb silver precursors, then dripping ethanol solution (1:1 dilution, volume ratio) of hydrazine hydrate into the swelled microsphere solution adsorbed with the silver precursors to reduce Ag + into elemental silver, and obtaining the core-shell silicone rubber@silver microspheres after suction filtration and collection, washing the core-shell silicone rubber@silver microspheres with deionized water for a plurality of times, and thoroughly drying the core-shell silicone rubber@silver microspheres at 60 ℃.
3. Preparation of stretchable flexible conductors with loosely packed structures
The preparation method comprises the steps of directly adding silicon rubber @ silver microspheres into a polytetrafluoroethylene die (length, width and height are 100mm, 10 mm) according to a certain mass, then mixing Ecoflex 0050 silicon rubber mixture at room temperature to prepare a precursor solution, slowly pouring the precursor solution into the die deposited with the close-packed conductive microspheres to enable the precursor solution to fully permeate gaps among the microspheres, transferring the die to a vacuum condition, and curing at the temperature of 25 ℃ for 24 hours to obtain the stretchable conductor.
The surface morphology of the silicone rubber @ silver microspheres and the distribution of the microspheres in the stretchable conductor were observed using a scanning electron microscope (FEI-SEM, quanta 650 ESEM), an optical microscope (OLYMPUS BX 51), the initial conductivity of the conductor was measured using a low resistance tester (JK 2512 BDC), the stress-strain curve of the conductor was recorded using a universal tensile tester (SANS CMT 40000), and the conductivity of the conductor at different tensile strains was measured using a combination of a universal tensile tester and a comprehensive IV performance tester (JCY 3100).
The structure and performance test results of the stretchable conductors prepared in embodiments 1-5 of the present invention are shown in fig. 1-6.
As can be seen from FIG. 2, the optimum initial conductivity of the stretchable conductor with a close-packed structure (the conductivity of the stretchable conductor at 0 strain) was 67185S/cm (example 4), whereas the initial conductivity of the stretchable conductor with a loose-packed structure obtained without adding a solvent (example 5) was only 3043S/cm, and the tensile elongation at break and modulus of the close-packed stretchable conductor obtained in example 4 were 602%,0.79MPa, and the conductivity under stretching was 820S/cm (400% strain), respectively.
According to the result, the conductive microsphere with the close-packed network structure can be prepared by adopting a solvent volatilization mode, a liquid bridge can be generated between adjacent particles by solvent volatilization, the tension of the liquid bridge can reach kilopascals or even megapascals, so that adjacent particles with a certain distance are tightly pulled together, the prepared conductive microsphere is packaged by a packaging material (liquid Ecoflex silicone rubber), and the poured liquid Ecoflex silicone rubber has higher elongation at break and low elastic modulus, and is good in compatibility with the conductive microsphere, so that the flexible conductor with high stretchability and ultrahigh conductivity is obtained.
Claims (6)
1. A method of making a stretchable conductor, comprising the steps of:
1) Synthesizing high molecular elastomer microsphere by suspension polymerization;
2) The method comprises the steps of activating a high polymer elastomer microsphere, immersing the high polymer elastomer microsphere in a conductive metal precursor solution to enable the high polymer elastomer to fully swell and adsorb the conductive metal precursor, and then adding a reducing agent to reduce metal ions into a metal simple substance to prepare the conductive microsphere with a core-shell structure, wherein the conductive metal precursor solution is selected from tetrahydrofuran solution or isopropanol solution containing silver trifluoroacetate, and the reducing agent is hydrazine hydrate, ascorbic acid, sodium citrate or sodium sulfite;
3) Dispersing the obtained conductive microspheres in a solvent, pouring the solvent into a mould for drying, and volatilizing the solvent to lead the conductive microspheres to form conductive microspheres with close-packed three-dimensional conductive networks;
The polymer elastomer and the packaging are made of silicon rubber;
The stretchable conductor comprises an encapsulation layer and conductive microspheres arranged in the encapsulation layer, wherein the conductive microspheres are core-shell conductive microspheres which are formed by taking polymer elastomer microspheres as cores and conductive fillers as shells.
2. The method for preparing a stretchable conductor according to claim 1, wherein the mass ratio of the conductive microspheres to the solvent is 1:2-1:10.
3. The method of preparing a stretchable conductor according to claim 2, wherein the mass ratio of the conductive microspheres to the solvent is 1:2, 1:4, 1:6, 1:8 or 1:10.
4. The method of producing a stretchable conductor according to claim 1 or 2, wherein the solvent is at least one of methanol, ethanol, chloroform, water, acetone, or n-heptane.
5. The method for preparing the stretchable conductor according to claim 1, wherein in the step 2), the method for performing the activation treatment before immersing the polymer elastomer microspheres in the conductive metal precursor solution is that the polymer elastomer microspheres are treated in a plasma environment for 10-30 min with a power of 200-600W.
6. A stretchable conductor produced by the method of any of claims 1 to 5.
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