Preparation method of Ag-NW conductive film based on water-water transfer printing activator interface

Abstract

The invention provides a preparation method of an Ag-NW conductive film based on a water-water transfer printing activating agent interface, which comprises the following steps: firstly, promoting Ag-NWs to be enriched in a water transfer printing activating agent phase through a Malangori convection effect; ag-NWs in a water transfer printing activator phase spontaneously form a conductive film with an ordered array structure, and the whole interface assembly process can be completed in only 2 seconds, so that the preparation efficiency is remarkably improved. Besides, the prepared Ag-NW conductive thin film has high conductivity, high mechanical flexibility and excellent transfer flexibility, can be easily transferred to any substrate surface through a liquid phase transfer method, and is beneficial to promotion of large-scale industrial production of the Ag-NW conductive thin film.

Description

Technical Field

[0001] The present invention relates to the field of Ag-NW conductive films, and particularly to a preparation method of an Ag-NW conductive film based on the interface of a water-water transfer activator. Background Art

[0002] Conductive films constructed with metal layers are widely used in flexible circuits, sensors, electromagnetic shielding and other fields due to their high conductivity. Currently, common methods for preparing conductive films in industry, such as printing methods and Mayer rod coating methods, are widely used because of their low equipment costs and suitability for large-scale production requirements. However, with the continuous development of technology, the conductive films prepared by these two preparation methods are difficult to meet the high requirements of existing functional devices for the quality and performance of conductive films due to low precision and material utilization rate. In addition, although other methods for preparing conductive films, such as the template method and photolithography method, can prepare conductive films with high resolution and excellent stability, their high costs, time-consuming preparation processes and great difficulty in batch production have greatly limited their wide application.

[0003] Regarding the assembly and preparation of Ag-NW conductive films, many schemes have been proposed by researchers, such as methods using external field regulation, precision printing, Langmuir–Blodgett (LB) technology, and surface modification. Although certain progress has been made in achieving the ordered structure of the films and improving the preparation efficiency by these methods for preparing Ag-NW conductive films, there are still some limitations in practical applications. For example, although the external field regulation and precision printing methods have a certain degree of flexibility, their operating space is relatively limited and it is difficult to meet the requirements for large-scale preparation of Ag-NW conductive films; while the LB technology can achieve a highly ordered arrangement of nanowires, it requires special equipment and has a complex operation process and great transfer difficulty, significantly increasing the cost and time; although the surface modification technology can improve the interaction between nanomaterials, thereby simplifying the operation process and improving the preparation efficiency, its modification process is time-consuming and costly, limiting its popularization in practical applications. A series of traditional preparation methods of the above-mentioned Ag-NW conductive films are generally accompanied by problems such as complex operation, low efficiency, and great transfer difficulty.

[0004] In recent years, due to its advantages such as simple operation, low cost, and high preparation efficiency, the interface assembly technology has become a research hotspot in the field of conductive thin film preparation and has received extensive attention and research. Through the interface assembly technology, the uniform distribution of nanoparticles, nanosheets, carbon nanotubes, and nanorods can be achieved, and then high-performance conductive thin films can be prepared. For example, Shi et al. successfully prepared a highly conductive Ag-NW conductive thin film through the three-phase interface assembly technology of oil-water-air. This technology only needs to drop the Ag-NWs aqueous dispersion onto the surface of chloroform, and a water-oil-gas three-phase interface can be spontaneously formed, inducing the efficient assembly of Ag-NWs at the interface, and finally preparing an Ag-NW conductive thin film with excellent performance. This method greatly simplifies the complex process of traditional Ag-NW conductive thin film preparation and improves the preparation efficiency. However, despite its significant advantages, there are still certain limitations in its assembly process. Since the assembly process of the Ag-NW conductive thin film will first occur in the edge region where the water phase contacts the substrate, and then gradually expand to the entire water-air interface, the assembly preparation of the Ag-NW conductive thin film is restricted by a specific space and it is difficult to meet the requirements of large-scale industrial production. Therefore, finding a strategy for efficiently preparing Ag-NW conductive thin films is of great significance for promoting the industrial production of Ag-NW conductive thin films.

[0005] The existing water transfer printing technology is commonly used for pattern transfer. The main components of the water transfer printing activator are organic solvents, surfactants, and film-forming resins. In the common pattern water transfer printing process in industry, the action mechanism of the water transfer printing activator is divided into three steps: First, the water transfer printing activator will dissolve the PVA film on the surface of the pattern layer, causing the pattern layer to detach and float on the water surface; Second, the surfactants rich in the water transfer printing activator can modify the surface of the substrate, enabling the pattern layer to adhere to the substrate surface; Finally, the film-forming resins rich in the water transfer printing activator can act as adhesives to firmly bond the pattern layer to the substrate surface, completing the transfer.

[0006] There is currently no relevant report on the preparation of Ag-NW conductive thin films using the water-water transfer printing activator interface. Summary of the Invention

[0007] The purpose of the present invention is to overcome the shortcomings and deficiencies existing in the prior art, and to provide a preparation method of an Ag-NW conductive thin film based on the water-water transfer printing activator interface.

[0008] The technical solution adopted by the present invention is as follows: A preparation method of an Ag-NW conductive thin film based on the water-water transfer printing activator interface, comprising the following steps: S1. Disperse Ag-NWs into solvent A, and add a water transfer printing activator solution and mix evenly to obtain a mixed solution; S2. Drop the mixed solution obtained in step S1 onto the water surface to form an Ag-NW conductive film.

[0009] During the film formation of Ag-NWs, due to the density difference between the water transfer activator and water and the insolubility of the water transfer activator, a surface tension gradient is generated at the liquid surface, thus triggering the Marangoni convection effect. Driven by the Marangoni convection effect, Ag-NWs are rapidly enriched in the water transfer activator phase. Subsequently, due to the volatilization of the volatile components (such as acetone, etc.) contained in the water transfer activator, the rapid dispersion and arrangement of Ag-NWs in the water transfer activator phase are further accelerated, thus improving the film formation efficiency. Compared with general surfactants, the water transfer activator has functions such as wetting, dissolving, volatilizing, and bonding, rather than simply reducing the surface tension.

[0010] Preferably, in step S1, the mass-volume ratio of Ag-NWs to the water transfer activator solution is 10:(0.4 - 2) g / L.

[0011] Preferably, in step S1, the volume ratio of solvent A to the water transfer activator solution is (1 - 5):1.

[0012] Preferably, in step S1, the solvent A is ethanol.

[0013] Preferably, in step S1, the water transfer activator solution comprises the following components: Acetone 60% - 70%; Ethyl acetate 10% - 15%; Isopropyl alcohol 10% - 15%; Ethylene glycol monobutyl ether 3% - 5%; TX-10 1% - 2%; PVB resin 1% - 2%.

[0014] Preferably, it further includes step S3: S3. Transfer the Ag-NW conductive film obtained in step S2 to the substrate by the liquid phase transfer method and dry it to obtain the Ag-NW conductive film loaded on the substrate.

[0015] Among them, the tool for transfer can be a dropper, or other instruments with liquid transfer and control functions such as a separatory funnel, a syringe, etc.; the substrate can be PET, PDMS, a glass plate, copperplate paper, non-woven fabric, etc.

[0016] Preferably, in step S3, the substrate is PET or PDMS.

[0017] Preferably, it further includes step S4: S4. Wash and dry the Ag-NW conductive film loaded on the substrate obtained in step S3.

[0018] Preferably, the washing in step S4 includes the following steps: S4-1. Immerse the Ag-NW conductive film loaded on the substrate in a sodium borohydride solution for 0.1 - 2 min and then take it out. This step can further improve the conductivity of the Ag-NW conductive film. S4-2. Remove the excess sodium borohydride on the surface of the Ag-NW conductive film.

[0019] Preferably, an ethanol solution is used to remove the excess sodium borohydride on the surface of the Ag-NW conductive film.

[0020] Preferably, the solvent of the sodium borohydride solution is a mixed solution of water and ethanol with a volume ratio of 1:1, and the concentration of the sodium borohydride solution is 0.01 - 0.5 mol / L.

[0021] Preferably, in steps S3 and S4, the drying temperature is 60 - 80 °C and the drying time is 5 - 15 min. The drying equipment is not limited to oven heating and can also be other heating equipment such as a heating plate.

[0022] The beneficial effects of the present invention are as follows: 1. In the present invention, aiming at the problems of complex operation, low efficiency, and great transfer difficulty existing in the preparation of Ag-NW conductive films by traditional interfacial assembly technology, a strategy for preparing Ag-NW conductive films based on water-water transfer activator interfacial assembly is innovatively proposed. This strategy first promotes the enrichment of Ag-NWs in the water transfer activator phase through the Marangoni convection effect. Then, driven by the anisotropic capillary force, the Ag-NWs in the water transfer activator phase spontaneously form a conductive film with an ordered array structure. Based on the above mechanism, the entire interfacial assembly process can be completed in only 2 s, significantly improving the preparation efficiency. In addition, the Ag-NW conductive film prepared based on this strategy has high conductivity, high mechanical flexibility, and excellent transfer flexibility, and can be easily transferred to the surface of any substrate by the liquid phase transfer method.

[0023] 2. The method for preparing the Ag-NW conductive film of the present invention is simple, effective, and fast, and can be operated in an atmospheric environment.

[0024] 3. The preparation of the Ag-NW conductive film of the present invention has the advantages of simple operation, high efficiency, and easy transfer, which helps to promote the large-scale industrial production of Ag-NW conductive films. Description of the Drawings

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, obtaining other drawings without creative efforts still belongs to the scope of the present invention.

[0026] Figure 1 Process schematic diagram of the preparation method of the Ag-NW conductive film of the present invention; Figure 2 Optical photograph of the (a) Ag-NW conductive film prepared in Example 1 of the present invention; (b, c) SEM images of the PET / AgNW conductive film at low magnification and high magnification; Figure 3 Process diagram of the preparation of the Ag-NW conductive film in Example 1 of the present invention; Figure 4 Conductivity diagrams of the (a) PET / AgNW conductive film and (b) PDMS / AgNW conductive film prepared in Example 1 of the present invention; Figure 5 Changes in the surface resistance of the (a) PET / AgNW conductive film and (b) PDMS / AgNW conductive film prepared in Example 1 of the present invention during cyclic testing at a fixed bending diameter and twisting angle; (c, d) Changes in the surface resistance of the PDMS / AgNW conductive film at different bending diameters and twisting angles; Figure 6 Process diagram of the transfer of the Ag-NW conductive film in Example 1 of the present invention; Figure 7 Patterned (a) on the PET substrate and (b) on different substrates of the Ag-NW conductive film prepared in Example 1 of the present invention; Detailed implementation manners

[0027] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings.

[0028] Example 1 This example provides a preparation method of an Ag-NW conductive film based on the water-water transfer activator interface, including the following steps: Step S1: Uniformly disperse 10 mg of Ag-NWs into 2 mL of ethanol, and add 0.6 mL of the water transfer activator solution thereto, and mix well.

[0029] Step S2: Use a dropper to drop the mixed solution obtained in Step S1 onto the circular water surface with a diameter of 10 cm at a rate of 0.25 mL / min drop by drop to form an Ag-NW conductive film with a diameter of 10 cm.

[0030] Step S3: Suck out the Ag-NW conductive film prepared in Step S2 through a dropper and transfer it onto a PET substrate, and perform a drying treatment at 70 °C to obtain an Ag-NW conductive film with PET as the substrate, that is, a PET / AgNW conductive film.

[0031] Step S4: Spin-coat 200 μL of PDMS solution evenly on the surface of the PET / AgNW conductive film. After drying at 70 °C, through a mechanical peeling operation, the Ag-NWs on the PET surface can be completely transferred onto the PDMS film to obtain an Ag-NWs conductive film with PDMS as the substrate, that is, a PDMS / AgNW conductive film.

[0032] Step S5: Immerse the Ag-NWs conductive films with different substrates prepared in Steps S3 and S4 in a sodium borohydride (NaBH 4 ) solution with a concentration of 0.01 - 0.5 mol / L using water and ethanol with a volume ratio of 1:1 as the solvent for 30 s, and then wash the residual NaBH 4 clean with ethanol and dry at 70 °C for 2 min to obtain clean PET / AgNW and PDMS / AgNW conductive films on the surface.

[0033] Example 2 The difference between the preparation method provided in this example and that in Example 1 is only that in Step S1, the addition amount of the water transfer printing activator solution is 1 mL.

[0034] Example 3 The difference between the preparation method provided in this example and that in Example 1 is only that in Step S1, the addition amount of the water transfer printing activator solution is 2 mL.

[0035] Example 4 The difference between the preparation method provided in this example and that in Example 1 is only that in Step S1, the addition amount of the water transfer printing activator solution is 0.5 mL.

[0036] Example 5 The difference between the preparation method provided in this example and that in Example 1 is only that in Step S1, the addition amount of the water transfer printing activator solution is 0.4 mL.

[0037] The composition of the water transfer printing activator solution used in the embodiments of the present invention is as follows: acetone 60%-70%; ethyl acetate 10%-15%; isopropyl alcohol 10%-15%; ethylene glycol monobutyl ether 3%-5%; TX-10 1%-2%; PVB resin 1%-2%. After testing, the effects achieved by the water transfer printing activator solution within the above proportion range are basically the same when applied to the embodiments of the present invention.

[0038] In Examples 1-5, the ratio of the water transfer printing activator solution to Ag-NWs was adjusted, and the tested effects were basically the same. Now, taking the Ag-NW conductive film prepared in Example 1 as an example, its characterization and effects are described.

[0039] As Figure 2 As shown in Figure 2 (a), the optical photograph of the Ag-NW conductive film assembled in Example 1 shows the characteristics of the Ag-NW conductive film prepared by water-water transfer printing activator interface assembly, which is uniform, smooth, and has a metallic luster. To explore the structural characteristics of the Ag-NW conductive film prepared by water-water transfer printing activator interface assembly, the morphology of PET / AgNW was characterized by SEM. As shown in

[0040] To verify that the strategy of preparing Ag-NW conductive film by water-water transfer printing activator interface assembly can significantly improve the preparation efficiency, we precisely recorded the complete process and the required time from the moment a drop of the mixed solution (water transfer printing activator, ethanol, and Ag-NWs) dripped onto the water surface to the formation of the film by the assembly of Ag-NWs at this interface. As shown in Figure 3 the process of preparing the Ag-NW conductive film by water-water transfer printing activator interface assembly. The results show that it only takes 2 s for Ag-NWs to quickly complete the assembly of the Ag-NW conductive film at the water-water transfer printing activator interface. Therefore, the preparation of the Ag-NW conductive film by water-water transfer printing activator interface assembly significantly improves the preparation efficiency of the Ag-NW conductive film and lays a solid foundation for the efficient large-scale production of the Ag-NW conductive film.

[0041] To evaluate the electrical conductivity of the Ag-NW conductive film prepared by water-water transfer printing activator interface assembly, we tested the conductivity of the PET / AgNW conductive film and the PDMS / AgNW conductive film with a two-probe four-probe tester. The test results show that compared with the PDMS / AgNW conductive film ((2.8±0.1)×10 5Compared with (S / m), the PET / AgNW conductive film has better conductivity ((3.2 ± 0.1) × 10 5 S / m). This result indicates that the Ag-NW conductive film prepared by interface assembly based on the water-water transfer activator has excellent conductive performance, can meet the requirements of functional devices for high conductivity, and provides a solid foundation for the application of Ag-NW conductive films in various functional devices.

[0042] To explore the mechanical flexibility of the Ag-NW conductive film prepared by interface assembly based on the water-water transfer activator, we conducted bending and twisting tests on the PET / AgNW conductive film and the PDMS / AgNW conductive film respectively. As Figure 5 shown in (a, b), under the conditions of a bending diameter of 20 mm and a twisting angle of 180°, after 10,000 cycles of testing, the change in surface resistance (ΔR / R0) of the PET / AgNW and PDMS / AgNW conductive films did not exceed 0.14. Both the PET / AgNW and PDMS / AgNW conductive films exhibited excellent mechanical flexibility. In addition, compared with the PET substrate, the PDMS substrate has higher softness and flexibility. Especially after complete curing, the PDMS substrate can further enhance the adhesion with Ag-NWs, thus significantly improving the durability and stability of the conductive film. Given these advantages of the PDMS substrate, we further evaluated the mechanical flexibility of the PDMS / AgNW conductive film. As Figure 5 shown in (c, d), under the test conditions of different twisting angles and bending diameters, the change in surface resistance of the PDMS / AgNW conductive film remained at an extremely low level, with the maximum increase of less than 0.01. These test results indicate that the strategy of interface assembly based on the water-water transfer activator endows the Ag-NW conductive film with excellent mechanical flexibility, laying a solid foundation for its wide application in the field of flexible functional devices.

[0043] As Figure 6 shown is the transfer process of the Ag-NW conductive film prepared by interface assembly based on the water-water transfer activator. The Ag-NW conductive film that has been prepared by interface assembly at the water-water transfer activator interface is sucked out by the liquid phase transfer method, and then dropped on the PET surface, and the Ag-NW conductive film can be easily transferred onto the PET substrate. Based on this process, after multiple transfers and drying treatments, finally, an Ag-NW conductive film with any area size and intact without damage can be prepared, proving that the Ag-NW conductive film prepared by interface assembly based on the water-water transfer activator has good transfer flexibility.

[0044] The transfer flexibility of the Ag-NW conductive film was further verified. Based on the transfer flexibility of the Ag-NW conductive film, the patterning application of the Ag-NW conductive film on different substrates can be realized. As Figure 7 shown in (a), precise patterning of the Ag-NW conductive film prepared by interfacial assembly based on a water-water transfer activator was achieved on a PET substrate through diverse pattern templates. The patterns prepared on the PET substrate not only have high clarity, but also the pattern distribution of the transferred Ag-NW conductive film is uniform, demonstrating flexible transfer and printing performance.

[0045] To verify the applicability of the Ag-NW conductive film prepared by interfacial assembly based on a water-water transfer activator on different substrates, three representative substrate materials, namely, rough copperplate paper, smooth glass, and porous non-woven fabric, were selected in addition to the commonly used PET and PDMS. The Ag-NW conductive film was transferred onto the above various substrates by a liquid-phase transfer method. As Figure 7 shown in (b), the Ag-NW conductive film prepared in the present invention can be successfully transferred onto the above various substrates, and the transferred patterns are clear and uniform, regardless of the characteristics of the substrate materials, achieving high-quality patterning.

[0046] The foregoing disclosure is only for the preferred embodiments of the present invention, and of course, it cannot be used to limit the scope of the rights of the present invention. Therefore, equivalent changes made according to the claims of the present invention still fall within the scope covered by the present invention.

Claims

1. A method for preparing a Ag-NW conductive film based on a water-water transfer activator interface, characterized in that: The steps include: S1, dispersing Ag-NWs into solvent A, adding water transfer activator solution and mixing evenly to obtain a mixed solution; S2. Dropping the mixed solution obtained in step S1 onto a water surface to form an Ag-NW conductive film.

2. The method for preparing a Ag-NW conductive film based on a water-water transfer activator interface according to claim 1, characterized in that: In step S1, the mass volume ratio of Ag-NWs to water transfer activator solution is 10:(0.4-2) g / L.

3. The method for preparing a Ag-NW conductive film based on a water-water transfer activator interface according to claim 1, characterized in that: In step S1, the volume ratio of solvent A to water transfer activator solution is (1-5):

1.

4. The method for preparing a Ag-NW conductive film based on a water-water transfer activator interface according to claim 1, characterized in that: In step S1, the solvent A is ethanol.

5. The method for preparing a Ag-NW conductive film based on a water-water transfer activator interface according to claim 1, characterized in that: In step S1, the water transfer activator solution comprises the following components: Acetone 60%-70%; Ethyl acetate 10%-15%; Isopropyl alcohol 10%-15%; Ethylene glycol butyl ether 3%-5%; TX-10 1%-2%; PVB resin 1%-2%.

6. A method for preparing a Ag-NW conductive film based on a water-water transfer activator interface according to any one of claims 1 to 5, characterized in that: The step S3 is also included: S3, transferring the Ag-NW conductive film obtained in step S2 to a substrate by a liquid phase transfer method and drying the Ag-NW conductive film supported on the substrate.

7. The method for preparing a Ag-NW conductive film based on a water-water transfer activator interface according to claim 6, characterized in that: In step S3, the substrate is PET or PDMS.

8. The method for preparing a Ag-NW conductive film based on a water-water transfer activator interface according to claim 6, characterized in that: The step S4 is also included: S4, washing and drying the Ag-NW conductive film loaded on the substrate obtained in step S3.

9. The method for preparing a Ag-NW conductive film based on a water-water transfer activator interface according to claim 8, characterized in that: The washing in step S4 comprises the following steps: S4-1, immersing the Ag-NW conductive film loaded on the substrate in a sodium borohydride solution for 0.1-2 min and then taking it out; S4-2. Remove excess sodium borohydride on the surface of the Ag-NW conductive film.

10. The method for preparing a Ag-NW conductive film based on a water-water transfer activator interface according to claim 8, characterized in that: In steps S3 and S4, the drying temperature is 60-80° C. and the drying time is 5-15 min.

Images