Method for producing a stretchable conductor of asymmetric structure and use thereof
By self-assembling silver nanowires with the asymmetric structure of waterborne polyurethane, the contradiction between conductivity and stretchability of stretchable conductor materials is resolved, realizing an environmentally friendly and simplified process for stretchable conductive films that can be widely used in wearable electronic devices.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- QINGDAO UNIV
- Filing Date
- 2023-05-17
- Publication Date
- 2026-06-02
AI Technical Summary
Existing stretchable conductor materials have a trade-off between conductivity and stretchability, and the manufacturing process is complex and the volatilization of organic solvents pollutes the environment and human health.
A method for preparing a stretchable conductor with an asymmetric structure is adopted. The stretchable conductive film with an asymmetric structure is formed by mixing silver nanowires with aqueous polyurethane. The process is simplified and the conductivity and stretchability are improved by using self-assembly technology and green solvent aqueous polyurethane emulsion.
It achieves a balance between conductivity and tensile strength, is environmentally friendly in its manufacturing process, is suitable for wearable electronic devices, and has self-healing and good adhesion properties, making it suitable for sensors and stretchable electrodes.
Smart Images
Figure CN116779241B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of stretchable conductor materials technology, specifically relating to a method for preparing an asymmetric stretchable conductor and its applications. Background Technology
[0002] Stretchable conductors have great application prospects in stretchable electronics and have received widespread attention. For example, they are used in flexible and stretchable electronic devices such as sensors, heating devices, light-emitting devices, electromagnetic shielding devices, capacitors, energy harvesting devices, and stretchable electronic circuits. As an important component of stretchable electronic devices, they have been extensively studied.
[0003] Structural engineering techniques have been used to endow electronic devices made from rigid electronic materials with deformability. However, this technique relies on expensive microfabrication processes. Furthermore, due to the inherent stiffness of electronic materials, localized mechanical mismatches occur between rigid electronic devices and soft substrates, leading to side effects such as limited long-term reliability. Stretchable conductors composed of conductive nanoscale fillers dispersed in a soft polymer matrix have become important candidate materials for flexible and stretchable electronic devices.
[0004] However, some stretchable conductive materials still have the following main problems:
[0005] (1) There is a trade-off between stretchability and electrical conductivity. Increasing the amount of conductive filler can achieve higher conductivity but reduce stretchability.
[0006] (2) The manufacturing process is complex and requires multiple manufacturing steps, which hinders its widespread application.
[0007] (3) The volatilization of organic solvents during the preparation process causes pollution to the environment and human body. Summary of the Invention
[0008] The purpose of this invention is to provide a method for preparing an asymmetric stretchable conductor. Another purpose of this invention is to provide an application of the asymmetric stretchable conductor.
[0009] To achieve the above objectives, the technical solution of the present invention is as follows:
[0010] A method for fabricating an asymmetric stretchable conductor includes the following steps performed sequentially:
[0011] 1) Synthesis of silver nanowires;
[0012] Synthetic waterborne polyurethane emulsions;
[0013] 2) After mixing and stirring the silver nanowires with water and the aqueous polyurethane emulsion, pour the mixture into a glass dish and let it stand so that the silver nanowires settle to the bottom of the mixture in the glass dish. Then, the water evaporates to achieve drying. Finally, peel the film off the glass dish to obtain a stretchable conductive film.
[0014] The lower layer of the stretchable conductive film is a hybrid layer of silver nanowires and aqueous polyurethane, while the upper layer is an aqueous polyurethane layer, exhibiting an asymmetric structure.
[0015] Preferably, in step 1), the synthesis of silver nanowires specifically involves: stirring and mixing an aqueous solution of silver nitrate and an aqueous solution of sodium chloride in the dark to produce silver chloride flocculation, then filtering to obtain filter residue, then washing the filter residue with pure water, and then vacuum drying to obtain silver chloride.
[0016] Then, polyvinylpyrrolidone was dissolved in ethylene glycol, stirred and heated, silver chloride was added, followed by silver nitrate, and the mixture was kept warm and stirred for a period of time. After cooling, deionized water was added to the solution for washing, and the mixture was redispersed in deionized water. After completion, a mixture of silver nanowires and water was obtained.
[0017] Preferably, the specifications of the silver nanowires are: length of 3 micrometers to 15 micrometers, outer diameter of 50 nm to 500 nm, and aspect ratio of 190 to 210.
[0018] Preferably, in step 1), the synthesis of the waterborne polyurethane emulsion specifically involves:
[0019] First, mix and stir polytetrahydrofuran, isophorone diisocyanate and dibutyltin dilaurate, and react at 63℃-66℃ for a period of time, then raise the temperature to 83℃-86℃ and react for a period of time.
[0020] Then dimethylolpropionic acid and 1,4-butanediol are added to carry out a chain extension reaction. Acetone is added during the reaction to adjust the viscosity.
[0021] The reaction temperature was then lowered and neutralized with triethylamine, followed by the addition of a deionized water dispersion system and stirring. Once completed, an aqueous polyurethane emulsion was obtained.
[0022] Preferably, the particle size of the waterborne polyurethane emulsion is 32nm-35nm.
[0023] Preferably, in step 2), the mass ratio of silver nanowires to aqueous polyurethane is (0.02-0.16):(0.45-1.40).
[0024] The silver nanowires prepared by any of the above-described methods for preparing asymmetric stretchable conductors have a silver nanowire content ≤ 0.243 mg / cm³. 2Stretchable conductive films are used as sensors.
[0025] The silver nanowires prepared by any of the above-described methods for preparing asymmetric stretchable conductors have a silver content ≥ 1.540 mg / cm². 2 The use of stretchable conductive films as stretchable electrodes.
[0026] A method for preparing an asymmetric stretchable conductor involves cutting a stretchable conductive film prepared by any one of the above-described methods into strips, and then winding and twisting them to obtain stretchable conductive fibers.
[0027] This application has achieved the following beneficial technical effects:
[0028] (1) This invention provides a silver nanowire (AgNW) / waterborne polyurethane (WPU) material, its preparation and application, wherein AgNW is used as a conductive filler and WPU is used as an elastic matrix. This invention solves the problem of the contradiction between conductivity and tensile properties. The stretchable conductor material prepared based on this scheme has excellent tensile properties, strength, adhesion, self-healing and electrical properties, and can be used as electrodes, sensors, etc., and can be applied to wearable electronic devices and other fields. At the same time, the preparation process is simple and the whole process is in a green and environmentally friendly system. The developed silver nanowire / waterborne polyurethane stretchable conductor has a wide potential application prospect in wearable electronic devices.
[0029] (2) In this invention, AgNW is uniformly dispersed in water-based polyurethane (WPU) with water as solvent, and a silver nanowire / water-based polyurethane stretchable conductive film with an asymmetric structure is formed by sedimentation self-assembly. The stretchable conductive film has excellent electrical and mechanical properties, good self-healing and adhesion. At the same time, stretchable conductive fibers can be obtained by using the film self-twisting method.
[0030] (3) The conductivity of the stretchable conductive film prepared by this invention is tunable, and the silver nanowire content is ≤0.243 mg / cm². 2 Stretchable conductive films with low silver nanowire content can be used as sensors to detect human joint movement and respiratory status due to their high strain sensitivity; silver nanowire content ≥1.540 mg / cm 2 Stretchable conductive films with high silver nanowire content are ideal materials for stretchable electrodes due to their low surface resistance, high conductivity, and low resistance variation.
[0031] (4) The process of this invention is simple, low in cost and highly controllable, which solves the problems of complex manufacturing process, multi-step manufacturing process and obstacles to wide application of traditional manufacturing.
[0032] (5) This invention is a green and environmentally friendly water-based system that solves the problem of the volatilization of organic solvents and pollution to the environment and human body in the traditional preparation process.
[0033] (6) The stretchable conductive film prepared by the present invention can utilize its self-healing properties to obtain conductive fibers by twisting, and the fiber length can be controlled by the self-healing properties. Attached Figure Description
[0034] Figure 1 This is a SEM image of the silver nanowires prepared in Example 1 of this invention;
[0035] Figure 2 These are cross-sectional scanning electron microscope images of the stretchable conductive films with asymmetric structures prepared in Examples 1-3 of this invention.
[0036] Figure 3 These are the stress-strain curves of the asymmetric stretchable conductive films prepared in Examples 1-3 of this invention;
[0037] Figure 4 These are the resistance changes of the stretchable conductive films with asymmetric structures prepared in Examples 1-3 of this invention under stretching conditions.
[0038] Figure 5 This refers to the change in relative resistance of the stretchable conductive film with an asymmetric structure prepared in Example 1 under different degrees of stretching;
[0039] Figure 6 The test is to detect the degree of bending of human joints (fingers) using the stretchable conductive film with an asymmetric structure prepared in Example 1.
[0040] Figure 7 The test is to detect the degree of bending of a human joint (wrist) using the stretchable conductive film with an asymmetric structure prepared in Example 1.
[0041] Figure 8 The test is performed on the degree of bending of a human joint (elbow joint) using the stretchable conductive film with an asymmetric structure prepared in Example 1.
[0042] Figure 9 The test is the detection of human respiration using the asymmetric stretchable conductive film prepared in Example 1.
[0043] Figure 10 The relative resistance-strain curve of the stretchable conductive thin film with an asymmetric structure prepared in Example 3 is shown.
[0044] Figure 11 These are images of the asymmetric stretchable conductive films prepared in Examples 1-3 of this invention adhered to various substrates.
[0045] Figure 12 These are the self-healing performance data of the stretchable conductive film with an asymmetric structure obtained in Example 1 of this invention;
[0046] Figure 13 These are the self-healing performance data of the stretchable conductive film with an asymmetric structure obtained in Example 3 of this invention;
[0047] Figure 14 This is a scanning electron microscope image of the cross-section of the stretchable conductive fiber prepared in Example 4 of the present invention.
[0048] Figure 15 This is a stretch photograph of the stretchable conductive fiber obtained in Example 4 of the present invention. Detailed Implementation
[0049] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. The described embodiments are only a part of the embodiments of the present invention, and not all of them. Therefore, all other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.
[0050] This application provides a method for preparing a stretchable conductor with an asymmetric structure, comprising the following steps performed sequentially:
[0051] 1) Synthesis of silver nanowires;
[0052] Synthetic waterborne polyurethane emulsions;
[0053] 2) After mixing and stirring the silver nanowires with water and the aqueous polyurethane emulsion, pour the mixture into a glass dish and let it stand so that the silver nanowires settle to the bottom of the mixture in the glass dish. Then, the water evaporates to achieve drying. Finally, peel the film off the glass dish to obtain a stretchable conductive film.
[0054] The lower layer of the stretchable conductive film is a hybrid layer of silver nanowires and aqueous polyurethane, while the upper layer is an aqueous polyurethane layer, exhibiting an asymmetric structure.
[0055] In one embodiment of this application, in step 1), the synthesis of silver nanowires specifically involves: stirring and mixing an aqueous solution of silver nitrate and an aqueous solution of sodium chloride in the dark to produce silver chloride flocculation, then filtering to obtain filter residue, then washing the filter residue with pure water, and then vacuum drying to obtain silver chloride.
[0056] Then, polyvinylpyrrolidone was dissolved in ethylene glycol, stirred and heated, silver chloride was added, followed by silver nitrate, and the mixture was kept warm and stirred for a period of time. After cooling, deionized water was added to the solution for washing, and the mixture was redispersed in deionized water. After completion, a mixture of silver nanowires and water was obtained.
[0057] In one embodiment of this application, the specifications of the silver nanowires are: a length of 3 micrometers to 15 micrometers, an outer diameter of 50 nm to 500 nm, and an aspect ratio of 190 to 210.
[0058] In one embodiment of this application, step 1) specifically involves synthesizing the aqueous polyurethane emulsion as follows:
[0059] First, mix and stir polytetrahydrofuran, isophorone diisocyanate and dibutyltin dilaurate, and react at 63℃-66℃ for a period of time, then raise the temperature to 83℃-86℃ and react for a period of time.
[0060] Then dimethylolpropionic acid and 1,4-butanediol are added to carry out a chain extension reaction. Acetone is added during the reaction to adjust the viscosity.
[0061] The reaction temperature was then lowered and neutralized with triethylamine, followed by the addition of a deionized water dispersion system and stirring. Once completed, an aqueous polyurethane emulsion was obtained.
[0062] In one embodiment of this application, the particle size of the aqueous polyurethane emulsion is 32nm-35nm.
[0063] In one embodiment of this application, in step 2), the mass ratio of silver nanowires to aqueous polyurethane is (0.02-0.16):(0.45-1.40).
[0064] This application provides a method for preparing a stretchable conductor with an asymmetric structure, specifically including the following steps performed sequentially:
[0065] 1) Synthesis of silver nanowires (AgNW):
[0066] First, silver chloride was synthesized. Since silver chloride is photosensitive, the synthesis was carried out in the dark. Silver nitrate aqueous solution (5 mL, 0.5 M) was mixed with sodium chloride aqueous solution (5 mL, 1 M) and stirred at 800 rpm for 1 min. After adding sodium chloride, silver chloride immediately flocculated. The precipitate was separated from the supernatant, washed once with ultrapure water, and then vacuum dried to obtain silver chloride.
[0067] Then, 3.4 g of polyvinylpyrrolidone (PVP) (58000MW) was dissolved in 200 mL of ethylene glycol in a 500 mL three-necked flask and stirred at 330 rpm to 160 °C. Once the solution reached a stable temperature, an excess of 0.25 g of freshly prepared silver chloride was added at once. After 5 min, 1.1 g of silver nitrate was added at once. The flask was sealed tightly with a stopper, and the reaction mixture was stirred at 160 °C for 24 min. Finally, the reaction was stopped and cooled to room temperature. The solution was washed three times with deionized water (ID) and redispersed in deionized water at a ratio of 1.47 wt%. After completion, a mixture of silver nanowires and water was obtained.
[0068] 2) Synthesis of waterborne polyurethane (WPU):
[0069] Pre-dried polytetrahydrofuran (PTMG) (20g), isophorone diisocyanate (IPDI) (8.7g), and dibutyltin dilaurate (DBTDL) (four drops) were added to a three-necked flask with a condenser on one side and an N2 tube on the other. The temperature was then set to 65°C and the stirring speed was 400 rpm for 1.5 hours. The temperature was then increased to 85°C and the stirring speed was 400 rpm for 1 hour.
[0070] Then add dimethylolpropionic acid (DMPA) (1.8g) and 1,4-butanediol (BDO) (0.6g) to the three-necked flask, and continue stirring for 3.5 hours to carry out the chain extension reaction. During the reaction, a small amount of acetone is added to adjust the viscosity of the system.
[0071] After the reaction is complete, lower the reaction temperature to 45°C and neutralize with triethylamine (TEA) (2 mL) for 15 minutes;
[0072] Finally, deionized water (60.4 mL) was added to the dispersion system at room temperature, and high-speed emulsification was carried out at 1000 rpm for 40 minutes to obtain an aqueous polyurethane emulsion.
[0073] 3) Fabrication of stretchable conductive films:
[0074] The mixture of silver nanowires and water with an aqueous polyurethane emulsion was mixed and stirred slightly before being poured into a glass dish. The mixture was left to stand so that the silver nanowires would settle to the bottom of the mixture. The mixture was allowed to evaporate and dry at room temperature. Finally, the film was peeled off from the glass dish to obtain a stretchable conductive film.
[0075] The lower layer of the stretchable conductive film is a hybrid layer of silver nanowires and aqueous polyurethane, while the upper layer is an aqueous polyurethane layer, exhibiting an asymmetric structure.
[0076] The silver nanowires prepared by the method for preparing the asymmetric stretchable conductor described in any one of the above claims in this application have a silver nanowire content ≤ 0.243 mg / cm³. 2 Stretchable conductive films are used as sensors.
[0077] The silver nanowires prepared by the method for preparing the asymmetric stretchable conductor described in any one of the above claims in this application have a silver content ≥ 1.540 mg / cm². 2 The use of stretchable conductive films as stretchable electrodes.
[0078] This application provides a method for preparing an asymmetric stretchable conductor, wherein the stretchable conductive film obtained by any of the above methods is cut into strips (5 mm wide), and then wound and twisted in a manner similar to "traditional paper rope rolling" to form a stretchable conductive fiber.
[0079] In this application, the silver nanowires are synthesized using the polyol method: the polyol method involves reducing the silver nanowires with a polyol at high temperature, while using a surfactant to prevent the aggregation of the colloidal nanostructures; freshly prepared silver chloride must be used during synthesis, and the container must be well sealed; advantages: simple, fast, and with few byproducts.
[0080] The advantages of synthesizing waterborne polyurethane emulsion in this application are: (1) Waterborne polyurethane is dispersed in water, which is a green material that is friendly and harmless to the human body and the environment;
[0081] (2) Due to the incompatibility of soft and hard segments, waterborne polyurethane has a certain degree of microphase separation, thus possessing excellent mechanical properties, low-temperature flexibility, wear resistance, corrosion resistance, etc.
[0082] (3) Isocyanate groups can react with monomers containing active hydrogen, such as hydroxyl, amino, carboxyl, and mercapto groups. Therefore, the structure is highly designable and can be easily modified at the molecular level.
[0083] The asymmetric structure of the stretchable conductive film in this application effectively solves the problem of the contradiction between conductivity and stretchability.
[0084] Working principle:
[0085] Adjusting the microstructure of conductive fillers in elastomers is an effective way to resolve the contradiction between conductivity and tensile strength. Stretchable conductive films can easily change the microstructure of conductive fillers in elastomers through simple precipitation self-assembly, forming an asymmetric structure, thus effectively solving the problem of the contradiction between conductivity and tensile strength.
[0086] The reason or working principle behind the excellent mechanical properties of the stretchable conductive film with asymmetric structure in this application:
[0087] Because the film has an asymmetric structure, the conductive filler is deposited on one side of the film, which causes less damage to the structure of the waterborne polyurethane elastomer. Therefore, the stretchable conductive film can still have good mechanical properties.
[0088] The reason or working principle behind the excellent electrical properties of the asymmetric stretchable conductive film of this application is as follows:
[0089] Because the thin film has an asymmetric structure and the conductive layer is deposited on one side of the film, the conductive path of the material is effectively improved, thus exhibiting good electrical properties.
[0090] The reason or working principle behind the good adhesion of the asymmetric stretchable conductive film of this application:
[0091] Due to hydrogen bonding, the adhesion mechanism of the film is that it can tightly bind with hydroxyl, carboxyl and amino groups on different substrate surfaces (glass, plastic, skin) to form hydrogen bonds, thus exhibiting good adhesion.
[0092] The reason or working principle behind the excellent self-healing properties of the stretchable conductive film with asymmetric structure in this application is as follows:
[0093] Hydrogen bonding plays a crucial role. Numerous hydrogen bonds exist between polyurethane chain segments. When water molecules enter the aqueous polyurethane network, the intermolecular hydrogen bonds open, forming a large number of free hydrogen bonds. After the films come into contact with each other, as the water molecules evaporate, the molecular groups on the film surface reassemble with each other through hydrogen bonds, achieving self-healing.
[0094] The methods and apparatus not described in detail in this invention are all prior art and will not be elaborated further.
[0095] To better understand the present invention, the following embodiments are provided for further detailed description of the present invention, but they should not be construed as limiting the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above-described invention are also considered to fall within the protection scope of the present invention.
[0096] Example 1
[0097] A method for fabricating an asymmetric stretchable conductor includes the following steps performed sequentially:
[0098] 1) Silver nanowires synthesized from polyols were directly dispersed in diluted, environmentally friendly, water-based polyurethane emulsion (water as solvent) to form a uniform dispersion solution, wherein the AgNW content was 0.243 mg / cm³. 2 ;
[0099] 2) Pour the mixture into a glass dish, let it stand and dry at room temperature, and peel it off from the glass dish after drying to obtain a stretchable conductive film with an asymmetric AgNW / WPU structure.
[0100] Example 2
[0101] In this Example 2, the preparation method of the asymmetric stretchable conductor is the same as that in Example 1, and the WPU content is also the same. The difference is that the AgNW content is 0.815 mg / cm³. 2 .
[0102] Example 3
[0103] In this Example 3, the preparation method of the asymmetric stretchable conductor is the same as that in Example 1, and the WPU content is also the same. The difference is that the AgNW content is 1.540 mg / cm³. 2 .
[0104] Cross-sectional electron microscopy images of the asymmetric stretchable conductive films with different conductive filler contents prepared in Examples 1-3 above are shown below. Figure 2 As shown, the lower layer of the film is an AgNW+WPU layer, and the upper layer is a pure WPU layer, exhibiting an asymmetric structure.
[0105] The mechanical properties of the asymmetric stretchable conductive films with different conductive filler contents prepared in Examples 1-3 above are as follows: Figure 3 As shown, this asymmetric stretchable conductive material has good tensile properties and excellent strength.
[0106] The resistance changes of the asymmetric stretchable conductive films with different conductive filler contents prepared in Examples 1-3 above under stretching are as follows: Figure 4 As shown in the figure, the horizontal axis represents time (stretching rate is 10 mm / min), and the vertical axis represents resistance. It can be seen from the figure that regardless of the AgNW content, the resistance of the sample increases with increasing stretching. In this invention, by controlling the AgNW content in the composite material, the sensitivity of the nanocomposite material can be flexibly adjusted and applied. Stretchable conductive films with low silver nanowire content, due to their high strain sensitivity, can be used as sensors to detect human joint movement and respiratory status (Example 1). Stretchable conductive films with high silver nanowire content, due to their low surface resistance, high conductivity, and low resistance change, are ideal materials for stretchable electrodes (Example 3).
[0107] The relative resistance of the stretchable conductive film with asymmetric structure prepared in Example 1 above varies under different degrees of stretching, as shown below. Figure 5As shown, this asymmetric stretchable conductive material can clearly distinguish different degrees of strain, and the relative resistance does not drift within the range of 0-80%, maintaining good stability.
[0108] The asymmetric stretchable conductive film prepared in Example 1 above can be used to detect the degree of bending of human joints. Figure 6 , 7 As shown in Figure 8, the bending-stretching behavior of the fingers, wrists, and elbows caused by different bending-deformations can be clearly identified.
[0109] Human respiratory detection, such as Figure 9 As shown, human respiratory signals are recorded, and the intensity and frequency of breathing can be distinguished based on changes in relative resistance.
[0110] The relative resistance-strain curve of the asymmetric stretchable conductive thin film prepared in Example 3 above is shown in the figure. Figure 10 As shown, the thin-film electrode has high deformation capability and very mild sensitivity. During stretching, the relative resistance changes slowly, and when stretched by 200%, the relative resistance changes to 23.06.
[0111] The adhesion of the asymmetric stretchable conductive films with different conductive filler contents prepared in Examples 1-3 above is as follows: Figure 11 As shown, the film can be firmly attached to various substrates.
[0112] The self-healing properties of the asymmetric stretchable conductive films with different conductive filler contents prepared in Examples 1 and 3 above are as follows: Figure 12 , 13 As shown, both films exhibited good self-healing efficiency, with self-healing efficiencies of 89.3% and 93%, respectively.
[0113] Example 4
[0114] (1) The AgNWs synthesized from polyols are directly dispersed into diluted green and environmentally friendly WPU (water as solvent) emulsion to form a uniform dispersion solution.
[0115] (2) Pour the mixture into a glass dish, let it stand and dry at room temperature, and peel it off from the glass dish after drying to obtain a conductive elastic film with an asymmetric AgNW / WPU structure.
[0116] (3) Cut the WPU / AgNW film into strips 5mm wide and twist them into stretchable conductive fibers using a method similar to traditional paper rolls.
[0117] The cross-sectional electron microscope image of the stretchable conductive fiber prepared in Example 4 above is shown below. Figure 14As shown, the conductive filler is spirally arranged in the elastomer, which allows the fibers to maintain both conductivity and tensile strength, while also saving costs.
[0118] Tensile photographs of the fibers prepared in Example 4 above are shown below. Figure 15 As shown, the elongation can reach 900%.
[0119] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims
1. A method for preparing a stretchable conductor with an asymmetric structure, characterized in that, The following steps are performed sequentially: 1) Synthesis of silver nanowires; Synthetic waterborne polyurethane emulsions; 2) After mixing and stirring the silver nanowires with water and the aqueous polyurethane emulsion, pour the mixture into a glass dish and let it stand so that the silver nanowires settle to the bottom of the mixture in the glass dish. Then, the water evaporates to achieve drying. Finally, peel the film off the glass dish to obtain a stretchable conductive film. The lower layer of the stretchable conductive film is a hybrid layer of silver nanowires and waterborne polyurethane, while the upper layer of the stretchable conductive film is a waterborne polyurethane layer, exhibiting an asymmetric structure. In step 1), the synthesis of the waterborne polyurethane emulsion specifically involves: First, mix and stir polytetrahydrofuran, isophorone diisocyanate and dibutyltin dilaurate, and react at 63℃-66℃ for a period of time, then raise the temperature to 83℃-86℃ and react for a period of time. Then dimethylolpropionic acid and 1,4-butanediol are added to carry out a chain extension reaction. Acetone is added during the reaction to adjust the viscosity. The reaction temperature was then lowered and neutralized with triethylamine, followed by the addition of a deionized water dispersion system and stirring. After this process, an aqueous polyurethane emulsion was obtained. The particle size of the waterborne polyurethane emulsion is 32nm-35nm; In step 2), the mass ratio of silver nanowires to waterborne polyurethane is (0.02-0.16):(0.45-1.40).
2. The method for preparing an asymmetric stretchable conductor according to claim 1, characterized in that, In step 1), the synthesis of silver nanowires is specifically as follows: In the dark, silver nitrate aqueous solution and sodium chloride aqueous solution are stirred and mixed to produce silver chloride flocs, which are then filtered to obtain filter residue. The filter residue is then washed with pure water and then vacuum dried to obtain silver chloride. Then, polyvinylpyrrolidone was dissolved in ethylene glycol, stirred and heated, silver chloride was added, followed by silver nitrate, and the mixture was kept warm and stirred for a period of time. After cooling, deionized water was added to the solution for washing, and the mixture was redispersed in deionized water. After completion, a mixture of silver nanowires and water was obtained.
3. The method for preparing an asymmetric stretchable conductor according to claim 2, characterized in that, Specifications of silver nanowires: length of 3 micrometers to 15 micrometers, outer diameter of 50 nm to 500 nm, and aspect ratio of 190 to 210.
4. The stretchable conductive film with a silver nanowire content ≤0.243 mg / cm³ prepared by the method for preparing the asymmetric stretchable conductor according to any one of claims 1-3 is used as a sensor.
5. The stretchable conductor with an asymmetric structure prepared by the method for preparing any one of claims 1-3. Stretchable conductive films with a silver nanowire content ≥1.540 mg / cm³ are used as stretchable electrodes.
6. A method for preparing a stretchable conductor with an asymmetric structure, characterized in that, The stretchable conductive film prepared by the method for preparing the asymmetric stretchable conductor according to any one of claims 1-3 is cut into strips and then wound and twisted to form a stretchable conductive fiber.