Method of manufacturing a self-healable flexible microwave device
By using an improved polyimide film and room-temperature wet process to fabricate flexible microwave devices, the problem of performance degradation caused by damage during use has been solved, resulting in higher bending resistance and service life, while reducing manufacturing costs.
Patent Information
- Application Number
- CN202210216393.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-03-07
- Publication Date
- 2026-05-15
- Estimated Expiration
- 2042-03-07
AI Technical Summary
Existing flexible microwave devices are easily damaged by factors such as chemicals, external forces, light and heat during long-term use, leading to the formation of microcracks and affecting their performance and service life.
An improved polyimide film was used as the substrate, and the self-healing performance was improved by utilizing the π-π stacking effect. Flexible microwave devices were fabricated by a room temperature wet process. Combined with surface modification and in-situ self-metallization process, the tight adhesion between the metal layer and the substrate was ensured, and the bending resistance of the device was enhanced.
It improves the bending resistance and service life of flexible microwave devices, reduces the manufacturing difficulty and cost, enhances the adhesion of the metal layer, avoids cracks and wear, and improves conductivity reliability.
Smart Images
Figure CN116780201B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of flexible microwave devices, specifically relating to a method for manufacturing a self-healing flexible microwave device, specifically a method for manufacturing a flexible microwave antenna / filter. Background Technology
[0002] In recent years, compared with traditional rigid electronic devices, flexible electronic devices have received widespread attention and research from scholars due to their advantages such as bendability and light weight. [1,2] Flexible electronic devices include sensors. [3] Transmission lines [4] and antenna [5] And many other flexible components. Flexible filters are an important part of the radio frequency front end. [2,6,7] The performance of flexible radio frequency devices (RFDs) significantly impacts the overall performance of the flexible RF system. Flexible electronic devices hold great promise for future development. With the increasing integration and intelligence of wireless communication systems, novel microwave and millimeter-wave devices possessing transparent, flexible, and tunable characteristics have significant application value in both military and civilian communications.
[0003] Clearly, flexible microwave antennas / filters are crucial components of flexible wireless communication systems, and their performance directly impacts the overall system performance. During use, flexible microwave devices inevitably suffer damage, trauma, and breakage due to prolonged exposure to chemicals, external forces, light, and heat. The formation of microcracks not only degrades the basic performance of flexible microwave devices but also severely affects their lifespan.
[0004] Due to its excellent mechanical properties, flexibility, and dielectric properties, polyimide (PI) film has become one of the commonly used substrates for flexible electronic products. [8,9] Currently, traditional techniques for fabricating flexible devices based on polyimide substrates include photolithography.
[10] and printing technology [7,8] These traditional processes typically require complex handling steps, expensive experimental equipment, and strict environmental control during device fabrication.
[11] Furthermore, it is difficult for metal layers to achieve excellent adhesion on smooth polyimide films.
[0005] In our prior application CN2022100007490, we disclosed a method for manufacturing a bend-resistant flexible microwave device: identical patterned metal antennas are fabricated on two polyimide films of identical size and shape. The flexible microwave device is obtained based on surface modification and in-situ self-metallization processes. Specifically: one polyimide film is bent to fabricate a patterned metal antenna on its convex side; the other polyimide film is bent to fabricate a patterned metal antenna on its concave side; the patterned metal antennas on the two films are identical in size and shape; this yields two identical polyimide films with patterned silver metal on their surfaces, forming a flexible microwave antenna / filter; the two polyimide films with patterned metal layers are then stacked face-to-face in the same orientation (with the patterned silver metal layers facing each other) in a flat state, and then hot-pressed to obtain the final flexible microwave antenna / filter. The aforementioned flexible microwave device can withstand tens of thousands of bends without significantly reducing its electrical performance. However, it was found that under certain special circumstances, the polyimide film itself (not the metal layer) may break after thousands of bends, requiring further improvement.
[0006] The relevant references are as follows:
[0007] [1] ZHANG
[0008] [2] JIANG Y, ZHAO Y, ZHANG L, et al. Flexible film bulk acousticwave filters toward radiofrequency wireless communication[J]. Small, 2018,14(20).
[0009] [3] Li Jia, Huang Chun, Zhang Jian, et al. Flexible strain sensor based on silver nanoparticle / polyamic acid composite structure [J]. Journal of Nantong University (Natural Science Edition), 2019, 18(1):1-8.
[0010] [4] NIKOOBAKHT A, AGHAEI J, KHATAMI R, et al. Stochasticflexibletransmission operation for coordinated integration of plug-inelectric vehicles and renewable energy sources[J]. Applied Energy, 2019, 238:225-238.
[0011] [5] PAN T S, DAI L L, CHEN S H, et al. Low-impedanceflexibleArchimedean-equiangular spiral antenna[J]. IEEE Antennas andWirelessPropagation Letters, 2019, 18(9):1789-1793.
[0012] [6] ZHAO M J, ZHANG Y, LIU S, et al. UWB flexible filter with lowlossand excellent stopband performance[J]. Microwave and OpticalTechnologyLetters, 2017, 59(1):194-197.
[0013] [7] ZHAO M J, ZHANG Y. Compact wearable 5-GHz flexible filter[J].Electronics Letters, 2017, 53(10):661-663.
[0014] [8] LIU S Y, MONCION C, ZHANG J W, et al. Fully passiveflexiblewireless neural recorder for the acquisition of neuropotentials froma rat model[J]. ACS Sensors, 2019, 4(12):3175-3185.
[0015] [9] RODRIGUES F, RIBEIRO JF, ANACLETO PA, et al. Fabrication and characterization of polyimide-based 'smooth' titanium nitridemicroelectrode arrays for neural stimulation and recording[J]. Journal ofNeural Engineering, 2019, 17(1):016010.
[0016]
[10] LI RQ, GUO YX, CHEN W, et al. Aflexible liquid-metal alloy bandpass filter[J]. International Journal of RF andMicrowave Computer-AidedEngineering, 2018, 28(5):e21265. DOI:10.1002 / mmce.21265.
[0017]
[11] KHALEEL H R. Design and fabrication of compact inkjet printed antennas for integration within flexible and wearable electronics[J]. IEEETransactions on Components, Packaging and Manufacturing Technology, 2014,4(10):1722-1728. Summary of the Invention
[0018] To address the aforementioned technical problems, the present invention aims to provide a method for manufacturing a self-healing flexible microwave device, thereby further improving the bending resistance of the flexible microwave device. In this invention, the flexible microwave device refers to a flexible microwave antenna / filter. This invention was supported by the Major Project of Natural Science Research of Jiangsu Higher Education Institutions (17KJA470007), the Jiangsu Provincial Industry-University-Research Cooperation Project (BY2019128), the Nantong Municipal Science and Technology Project (JC2019112), and the Open Project of Nantong University-Nantong Intelligent Information Technology Joint Research Center (KFKT2016A05).
[0019] In this invention, polyimide (PI) thin film material was selected as the substrate for the flexible filter. Due to its excellent chemical resistance, low dielectric constant, and outstanding thermal stability, polyimide thin film has become one of the commonly used flexible substrates in flexible electronics. To reduce the fabrication difficulty, this paper studies a room-temperature wet process, resulting in a dense and continuous metal layer with good adhesion between the films, meeting the requirements of flexible circuits.
[0020] To demonstrate that room-temperature wet processing can be used to fabricate filters, this paper designs, fabricates, and tests a bandpass filter based on a flexible polyimide substrate. This filter exhibits a center frequency of 2.4 GHz, a relative bandwidth of 80.8%, a return loss greater than 20 dB, and a minimum insertion loss of less than 0.6 dB. Furthermore, the filter's mechanical properties were tested under bending, curling, and folding conditions, as well as the adhesion between the metal and the substrate; all performance characteristics were well maintained. The results indicate that the flexible filter fabricated using this technique possesses good mechanical flexibility and metal adhesion, demonstrating the feasibility of using room-temperature wet processing for flexible filter fabrication.
[0021] An improved polyimide film with self-healing properties was used as the flexible substrate material. Self-healing polymer materials are generally classified into two types: extrinsic self-healing materials and intrinsic self-healing materials. Extrinsic self-healing materials achieve their healing properties through the addition of an external healing agent; while intrinsic self-healing materials achieve their self-healing process through inherent properties of the material itself. Intrinsic self-healing materials typically achieve healing through the reversible recombination of covalent or non-covalent bonds.
[0022] Common reversible covalent bonds include: DA reaction, disulfide bond, carbon-carbon double bond [2+2] cycloaddition, allyl sulfide, anthracene, acylhydrazone bond, etc. Common non-covalent interactions include: hydrogen bonding, ionic bonding, coordination, π-π stacking, etc.
[0023] Since this invention uses an improved polyimide (PI) film material as the substrate of the flexible filter in an attempt to improve its self-healing properties, we chose π-π stacking as the improvement direction for the polyimide film, as an organic polymer. π-π stacking occurs between electron-deficient aromatic groups and electron-rich aromatic groups. Because π-π stacking is thermally reversible, it is often used as a thermo-induced self-healing material.
[0024] Under a nitrogen atmosphere, a diamino-terminated polysiloxane, 3,3',4,4'-biphenyltetracarboxylic acid dianhydride, and a chain extender were dissolved and mixed in a polar solvent and reacted at room temperature to obtain a colorless and transparent polysiloxane-polyamic acid block copolymer. The resulting product was reacted at 150–200 °C for 6–12 h. After the reaction, the product was coated onto a glass substrate, dried to remove the solvent, and then peeled off from the glass substrate to obtain a polysiloxane-polyimide block copolymer film for subsequent fabrication of flexible microwave antennas. The polyimide film referred to in this article refers to a polysiloxane-polyimide block copolymer film.
[0025] Chain extenders, also known as chain growth agents, are substances that react with functional groups on linear polymer chains to extend the molecular chain and increase the molecular weight. They are crucial for the synthesis of polyurethane adhesives and sealants, directly affecting the mechanical and processing properties of the products. Typically, chain extenders are low-molecular-weight, multifunctional alcohol or amine compounds containing hydroxyl or amino groups.
[0026] Commonly used alcohol chain extenders include 1,4-butanediol (BDO), 1,6-hexanediol, glycerol, trimethylolpropane, diethylene glycol (DEG), triethylene glycol, neopentyl glycol (NPG), sorbitol, and diethylaminoethanol (DEAE). Amine chain extenders include MOCA and liquid MOCA modified with formaldehyde, ethylenediamine (DA), and N,N-dihydroxy(diisopropyl)aniline (HPA). Hydroquinone di(β-hydroxyethyl) ether (HQEE) is also used as a chain extender in polyurethane adhesives; its heat resistance, hardness, and elasticity are higher than those of commonly used chain extenders. Commonly used chain extenders are small molecule alcohols containing di or polyhydroxyl groups, amino and imino compounds, or ether alcohols. The principle of chain extenders is that in production, compounds containing active hydrogen react with isocyanate end-group prepolymers, causing the molecular chain to diffuse and lengthen, thereby achieving resin curing and molding.
[0027] In this invention, the chain extender used is one or more of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane and low molecular weight bi-terminated amino polysiloxane.
[0028] Regarding the improvement of polyimide films, I would like to thank my colleagues in the organic synthesis field of the School of Chemistry and Chemical Engineering at Nantong University for their help.
[0029] Identical patterned metal antennas are fabricated on two polyimide films of identical size and shape. Specifically, one polyimide film is bent to create a patterned metal antenna on its convex side; the other polyimide film is bent to create a patterned metal antenna on its concave side; the patterned metal antennas on the two films are identical in size and shape; thus, a flexible microwave antenna / filter with patterned silver metal on the surface of two identical polyimide films is obtained.
[0030] The two polyimide films with patterned metal layers are stacked face-to-face in the same orientation in a flat state (the faces with patterned silver metal layers are bonded together), and then hot-pressed to obtain the final flexible microwave antenna / filter.
[0031] Preferably, the two polyimide films are bent with the same preset radius of curvature.
[0032] Preferably, the manufacturing method of the above-mentioned flexible microwave antenna / filter includes the following steps:
[0033] (0) The flexible microwave antenna / filter is simulated using HFSS simulation software. The structural parameters are optimized through simulation to obtain the theoretically optimized size parameters of the flexible microwave antenna / filter.
[0034] (1) The polyimide film was surface modified in KOH solution, followed by ion exchange in AgNO3 solution. After the reaction was completed, the polyimide film was washed and dried.
[0035] (2) Using the size parameters of the flexible microwave antenna / filter obtained in step (1), a mask layer is printed on the dried modified polyimide film, and then a reduction reaction is carried out in H2O2 solution to obtain a flexible microwave antenna / filter with a patterned metallized polyimide film surface.
[0036] The manufacturing methods (1) and (2) for flexible microwave antennas / filters are as follows:
[0037] (1) Select two polyimide films of the same size and shape;
[0038] Two polyimide films were bent according to a preset radius of curvature. The convex and concave sides of the two polyimide films were surface modified in KOH solution. Then, the convex and concave sides were ion exchanged in AgNO3 solution under the same bending state. After the reaction was completed, the polyimide films were cleaned and dried.
[0039] (2) Print identical mask layers in the same direction on two polyimide films modified and dried in step (1), and then perform a reduction reaction in H2O2 solution to obtain two identical polyimide film surface patterned flexible microwave antennas / filters, which are then cleaned and dried respectively.
[0040] The process includes the following after step (2):
[0041] (3) Two polyimide films are stacked face to face in the same orientation in a flat state (the metal surfaces with patterns are attached). Before stacking, metal wire terminals are led out and then hot-pressed to obtain the final flexible microwave antenna / filter.
[0042] It is worth noting that the manufacturing method of the flexible microwave antenna / filter proposed in this invention is applicable to any flexible microwave antenna / filter, and is not limited to a certain type of flexible microwave antenna or filter.
[0043] In this invention, the polyimide film has a self-healing function: the reversibility of the π-π stacking effect between polyimide segments and the high flexibility of polysiloxane segments give the polyimide film excellent self-healing properties, which can effectively extend the service life of flexible microwave devices.
[0044] Because the antenna structure is chemically grown from a polyimide substrate, it exhibits excellent adhesion to the substrate and is less prone to cracking. Furthermore, since the metallic silver conductive layers prepared from the convex and concave sides of two polyimide films are in two states respectively, when they are stretched flat and then hot-pressed together, the two metallic silver conductive layers will be in close contact and merge into a single conductive layer. They are subjected to both bending compressive stress and bending tensile stress, which complement each other to a certain extent. Regardless of the direction of bending stress in the final hot-pressed flexible microwave antenna / filter, the metallic silver conductive layer will maintain tight conductivity, eliminating stress at any level. This results in stronger overall bending resistance, a higher number of fault-free bending cycles, and greater conductive reliability. This technology is simple, requires no expensive equipment or vacuum conditions, and significantly reduces manufacturing costs.
[0045] Another unexpected advantage is that, since the metallic silver conductive layers prepared from the convex and concave sides of two polyimide films are stretched and flattened face to face and then hot-pressed together, the two metallic silver conductive layers will be in close contact and merged to form a single conductive layer. The conductive layer is located inside the hot-pressed polyimide film. Therefore, no matter whether the flexible microwave antenna / filter is bent, crumpled, wrinkled, or rubbed, the metallic silver conductive layer is protected by the polyimide film and will not be thinned or cracked by external friction, further enhancing its bending and wear-resistant mechanical properties.
[0046] It is important to emphasize that the use of an improved polyimide film with self-healing properties as the flexible substrate material aims to enhance the bending resistance of the polyimide film itself, thus providing self-healing functionality. Furthermore, the use of two polyimide films, with their convex and concave sides respectively, stretched face-to-face and then hot-pressed together, aims to enhance the bending resistance of the patterned metal layer and prevent cracking and wear. In other words, this invention contains these two improvements (inventive points).
[0047] The inventors have now explained the working principle, technical solution, and technical effects of this invention. Attached Figure Description
[0048] Figure 1 The main reaction process for metallizing the surface of polyimide films.
[0049] Figure 2 Schematic diagram of a room-temperature wet process for fabricating flexible microwave devices based on polyimide films.
[0050] Figure 3 This invention relates to a flexible microwave filter obtained by a room-temperature wet process.
[0051] Figure 4 The main reaction process for preparing polyimide films in this invention.
[0052] Figure 5 : An optimal simulation diagram of a flexible bandpass filter in this invention. Detailed Implementation
[0053] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the following description is provided in conjunction with the appendix. Figure 1-4 The preferred embodiments and specific implementation methods, structures, features, and effects according to the present invention are described in detail below. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.
[0054] To meet the development needs of flexible electronic devices in wireless communication systems, a foldable bandpass filter based on a polyimide flexible substrate was designed, fabricated, and tested.
[0055] This filter employs a coplanar waveguide structure and is fabricated using self-assembly technology. Testing revealed that the filter has a center frequency of 2.5 GHz, a relative bandwidth of 15.9%, a minimum insertion loss of 0.71 dB, and an in-band return loss greater than 20 dB. To test the filter's conformal characteristics, bending and folding tests were conducted. The test results show that the filter's performance remains essentially consistent across straight, bent, and folded states. Flexible filters fabricated using self-assembly technology hold promise as components of future flexible communication systems.
[0056] As a specific embodiment, the flexible microwave device is a flexible microwave filter, obtained based on surface modification and in-situ self-metallization processes, as detailed below:
[0057] Before formally manufacturing the flexible microwave antenna, the design and simulation are first carried out according to the expected performance indicators. The flexible microwave device is simulated using HFSS simulation software, and the structural parameters are optimized through simulation to obtain the theoretically optimized size parameters of the flexible microwave device.
[0058] Wireless LAN (WLAN) communication systems typically operate in the 2.4 GHz band. However, with technological advancements, an increasing number of IT devices are using this band. When multiple devices operate simultaneously, it obviously impacts network performance within the WLAN. To alleviate the congestion issue of the 2.4 GHz band, the 5 GHz band was proposed. The 5 GHz band primarily represents the 5.15-5.875 GHz frequency range, offering advantages such as reducing network congestion and improving signal quality.
[0059] Design a miniaturized flexible bandpass filter that can be applied to the 5 GHz band. Its specific specifications are shown in Table 1.
[0060]
[0061] A flexible microwave filter with a completed structural design was fabricated using a room-temperature wet process. The room-temperature wet process used in this invention is as follows: Figure 1 As shown, potassium hydroxide solution was used as a strong alkali for surface modification, silver ammonia solution was used for ion exchange, and hydrogen peroxide was used as a reducing agent. The surface of the polyimide first reacted with KOH solution; after the amide bonds were attacked, they opened to form polyamic acid (PAA), thus modifying the film surface. Then, ion exchange with silver ammonia solution transformed the PAA layer formed in the previous step into a silver-doped layer. Finally, reduction treatment with hydrogen peroxide reduced the silver ions adsorbed on the film surface to metallic silver, while also generating a large amount of oxygen.
[0062] Two pieces of polyimide film of identical size and shape are cut and selected;
[0063] One of the polyimide films is bent according to a preset radius of curvature. The convex side of the polyimide film is surface modified in KOH solution. Then, the convex side is ion exchanged in AgNO3 solution under the same bending state. After the reaction is completed, the polyimide film is cleaned and dried.
[0064] Another polyimide film was bent with the same preset radius of curvature. The concave side of the polyimide film was surface modified in KOH solution. Then, the concave side was ion exchanged in AgNO3 solution under the same bending state. After the reaction was completed, the polyimide film was cleaned and dried.
[0065] Identical mask layers were printed in the same direction on two modified and dried polyimide films, followed by a reduction reaction in H2O2 solution to obtain two flexible dual-notch ultrawideband antennas with metallized polyimide film surface patterns. The antennas were then cleaned and dried.
[0066] The main process steps are as follows:
[0067] a. Cleaning
[0068] The cleanliness of the polyimide surface directly affects the performance of the final composite film. Therefore, the polyimide film is first thoroughly cleaned with a large amount of anhydrous ethanol and acetone solution before the reaction begins.
[0069] b. Hydrolysis reaction
[0070] Prepare 100 ml of KOH solution with a concentration of 4 mol / L. To ensure complete dissolution of the KOH solid in the solution, the prepared KOH solution is usually left to stand overnight and used the next day. Immerse the cleaned membrane in the prepared potassium hydroxide solution to allow for hydrolysis, and remove it after 3 hours. To prevent unreacted hydroxide ions from reacting chemically with other treatment solutions in subsequent experiments, after surface modification, the membrane surface is rinsed with plenty of deionized water and ultrasonically cleaned to remove any residual solution.
[0071] c. Ion exchange
[0072] Prepare 100 ml of a 0.04 mol / L silver ammonia solution. It is important to note that the silver ammonia solution should be used immediately to prevent evaporation and affecting experimental results. Place the previously cleaned membrane in the prepared silver ammonia solution for ion exchange reaction, which should last for 2 hours to ensure sufficient replacement of potassium ions and silver ammonia complex ions on the membrane surface. Similarly, to prevent residual silver salt solution from affecting subsequent experimental procedures, after the reaction is complete, remove the membrane for cleaning and allow it to air dry at room temperature.
[0073] d. Reduction reaction
[0074] Prepare 1000 ml of hydrogen peroxide solution with a concentration of 0.01 mol / L. Immerse the dried film in the prepared hydrogen peroxide solution for rapid reduction; a smooth metal layer is obtained after 30 seconds.
[0075] For the chemical reactions and steps involved in the above process, please refer to [link / reference]. Figure 1 and Figure 2 .
[0076] Referring to Figure 6 in the specification of prior application 2022100007490, two polyimide films are then stacked face-to-face in the same orientation (with the patterned metal surfaces touching) in a flat state. Before stacking, metal wire terminals are led out, and then hot-pressed to form the final flexible dual-notch ultra-wideband antenna.
[0077] The obtained flexible bandpass antenna is subjected to electrical performance testing. If the test results deviate from the expected values, the parameters are adjusted, and the previous steps are returned to re-simulate and redesign or adjust the room temperature wet process parameters to remanufacture the flexible microwave antenna. If the test results meet the expected values, the parameters in the previous steps are fixed and the flexible microwave antenna is mass-produced.
[0078] The technique involves surface modification of the polyimide film in KOH solution, ion exchange in AgNO3 solution (Aladdin Company, Shanghai), and reduction reaction in H2O2 solution, ultimately achieving surface metallization of the polyimide film. All experimental steps were performed at room temperature.
[0079] The flexible dual-notch ultra-wideband antenna was simulated using HFSS simulation software, which is based on the finite element method. The simulation model of the polyimide substrate has a thickness of 50.8 μm and a dielectric constant of 3.5. Performance was optimized through simulation to improve structural parameters. The flexible microwave antenna, with its structural design completed in the previous steps, was fabricated using a room-temperature wet process, as detailed below:
[0080] After cleaning the polyimide film, two polyimide films were bent according to a preset radius of curvature. The convex and concave sides of each film were first immersed in a 4 mol / L KOH solution for 3 h. This step ensures that the polyimide film is chemically modified into polyamic acid through the cleavage of the surface imide rings. Subsequently, the convex and concave sides of the two polyimide films were immersed in 0.02 mol / L AgNO3 (99.8%) and NH3⋅H2O for 2 h to ensure K… + Replace with Ag + .
[0081] After cleaning and drying, the two treated polyimide films are pasted onto an A4 sheet of paper. Then, carbon ink is printed onto the polyimide film using a regular printer as a mask layer for the reduction of metallic silver. Next, the polyimide film with the mask pattern is immersed in a 30% H2O2 solution to ensure that the silver ions are completely reduced to silver.
[0082] Finally, the two polyimide films are stacked face to face in the same orientation in a flat state (the sides with the patterned metal are attached). Preferably, metal wire terminals are led out before stacking, and then hot-pressed to obtain the final flexible microwave filter, as shown in Figure 6 of the specification of the prior application 2022100007490.
[0083] As another embodiment, a flexible microwave filter is manufactured using a process similar to that described above, such as... Figure 3 As shown.
[0084] In this invention, such as Figure 4 As shown, π-π stacking is chosen as the improvement direction for polyimide films. π-π stacking occurs between electron-deficient and electron-rich aromatic groups. Due to its thermal reversibility, π-π stacking is often used as a thermo-induced self-healing material. Under a nitrogen atmosphere, diamino-terminated polysiloxane, 3,3',4,4'-biphenyltetracarboxylic acid dianhydride, and a chain extender are dissolved and mixed in a polar solvent and reacted at room temperature to obtain a colorless and transparent polysiloxane-polyamic acid block copolymer. The resulting product is reacted at 150–200 °C for 6–12 h. After the reaction, it is coated onto a glass substrate, dried to remove the solvent, and peeled off from the glass substrate to obtain a polysiloxane-polyimide block copolymer film for use in the manufacture of flexible microwave devices. The polyimide film referred to in this article refers to a polysiloxane-polyimide block copolymer film.
[0085] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A method for manufacturing a self-healing flexible microwave device, characterized in that: The manufacturing method specifically includes the following steps: (1) An improved polyimide film with self-healing function is used as a flexible substrate material. The polyimide segments in the polyimide film have reversible π-π stacking interaction, which makes the polyimide film have self-healing properties. Two pieces of polyimide film of identical size and shape are cut and selected; One of the polyimide films is bent according to a preset radius of curvature. The convex side of the polyimide film is surface modified in KOH solution. Then, the convex side is ion exchanged in AgNO3 solution. After the reaction is completed, the polyimide film is cleaned and dried. Another polyimide film is bent with the same preset radius of curvature. The concave side of the polyimide film is surface modified in KOH solution. Then the concave side is ion exchanged in AgNO3 solution. After the reaction is completed, the polyimide film is cleaned and dried. (2) Print identical mask layers in the same direction on two polyimide films after modification and drying in step (1), and then perform a reduction reaction in H2O2 solution to obtain two identical polyimide films with patterned silver metal flexible microwave antennas / filters. (3) Two polyimide films are flat and aligned in the same direction, with the surfaces of the patterned silver metal layer bonded together, and then hot-pressed to obtain the final flexible microwave antenna / filter.
2. The manufacturing method as described in claim 1, characterized in that: The polyimide film is a polysiloxane-polyimide block copolymer film.
3. The manufacturing method as described in claim 2, characterized in that: The polyimide film preparation process is as follows: Under a nitrogen atmosphere, a double-terminated amino polysiloxane, 3,3',4,4'-biphenyltetracarboxylic acid dianhydride, and a chain extender are dissolved and mixed in a polar solvent and reacted at room temperature to obtain a colorless and transparent polysiloxane-polyamic acid block copolymer; the obtained product is reacted at 150-200°C for 6-12 hours; after the reaction, it is coated on a glass substrate, dried to remove the solvent, and peeled off from the glass substrate to obtain a polysiloxane-polyimide block copolymer film for use in the manufacture of flexible microwave devices.
4. The manufacturing method as described in claim 1, characterized in that: Before step (1), there is also step (0): the flexible microwave antenna / filter is simulated by simulation software, and the structural parameters are optimized by simulation to obtain the theoretically optimized size parameters of the flexible microwave antenna / filter; the obtained size parameters are used to print the mask layer in step (2).
5. The manufacturing method as described in claim 1, characterized in that: Step (1) is operated as follows: After cleaning the polyimide film, the polyimide film is first immersed in KOH solution; this step ensures that the polyimide film is chemically modified into polyamic acid through the cleavage of the imide rings on the surface; subsequently, the surface-modified side of the film is immersed in AgNO3 and NH3⋅H2O to ensure that K + Replace with Ag + Clean and dry.
6. The manufacturing method as described in claim 1, characterized in that: In step (2), carbon ink is printed onto a polyimide film using a regular printer as a mask layer for the reduction of metallic silver; then, the polyimide film with the mask pattern is immersed in an H2O2 solution to ensure the silver ions Ag are reduced. + It is completely reduced to metallic silver.
7. The manufacturing method as described in claim 3, characterized in that: The chain extender used is one or more of 1,3-bis-3-aminopropyl-1,1,3,3-tetramethyldisiloxane and diamino-terminated polysiloxane.
8. The manufacturing method as described in claim 1, characterized in that: In step (2), two identical flexible microwave antennas / filters with patterned silver metal on the surface of polyimide films are obtained, and then cleaned and dried respectively.
9. The manufacturing method as described in claim 1, characterized in that: In step (3), metal wire terminals are led out before stacking and then hot-pressed.
10. The manufacturing method as described in claim 7, characterized in that: The preparation process of the improved polyimide film with self-healing function is as follows: 。