Method for preparing a laser-induced patterned graphene functional layer with conformal adhesion interface

Abstract

The application discloses a kind of preparation methods of conformal interface reinforced laser-induced patterning graphene functional layer, it is related to graphene functional layer preparation technical field.The present application includes step one, preparation gradient porous polyamide acid gel membrane;Step two, the surface of target substrate is textured, and gradient porous polyamide acid gel membrane is patterned and segmented again conformal transfer printing or conformal transfer printing again patterned segmentation, and composite structure is formed;Step three, the polyamide acid after transfer printing is obtained patterned polyimide precursor by gradient temperature thermal imidization;Step four, in patterned polyimide precursor, generate polymorphous graphene structure by laser-induced in situ, and the obtained polymorphous graphene structure is encapsulated and solidified.The present application can realize the preparation of region selective graphene functional layer, ensure the conformal of functional layer, guarantee complex pattern precision and alignment, avoid substrate body transformation, improve interface bonding force and encapsulation durability.

Description

Technical Field

[0001] This invention relates to the field of graphene functional layer preparation technology, and in particular to a method for preparing a conformal bonding interface enhanced laser-induced patterned graphene functional layer. Background Technology

[0002] Against the backdrop of the rapid development of wearable electronics, flexible / smart materials and devices, how to construct carbon-based patterned conductive functional layers in situ on the surface of substrates such as flexible fabrics and non-stretchable fiber-based composites, which are difficult to conformally bond, is of great significance for applications such as sensor manufacturing, electromagnetic interference shielding, and electrothermal conversion / heating.

[0003] Patent CN120211106A discloses a glass fiber fabric with electrothermal function and its preparation method. First, a graphene precursor polymer (the precursor for laser-induced graphene generation is typically a polyamic acid (PAA) solution / polyimide (PI) film, where the PAA solution must be heated to generate the PI film before it can be used for subsequent laser-induced graphene generation) is added to an organic solvent, and a precursor solution is obtained through stirring and ultrasonic treatment. Then, the glass fiber fabric is impregnated in the graphene precursor polymer solution, dried, and cured. Finally, laser-induced graphene is used to generate graphene in situ on the fabric surface, resulting in a glass fiber fabric with electrothermal function.

[0004] Patent CN118913080A discloses a method for fabricating a flexible strain sensor based on LIG. First, a white, filamentous mixture of polyimide analogs is prepared. Then, the mixture is brought into contact with one side of a fabric and allowed to stand at room temperature until a film is deposited on the bottom surface of the fabric. Finally, the film is laser-induced to generate laser-induced graphene, which is then encapsulated to obtain the product. This invention not only enables successful film formation on both the inside and outside of the fabric at room temperature to enhance adhesion, but also avoids damage to the fabric caused by laser induction, thus maximizing fabric performance.

[0005] Patent CN118516847A discloses a three-dimensional graphene-reinforced carbon fiber composite material, its preparation method, and its applications. A benzoxazine solution is coated onto a carbon fiber preform and dried. The carbon fiber preform, obtained through a laser treatment step, is then cleaned and dried to obtain the three-dimensional graphene-reinforced carbon fiber composite material. The prepared three-dimensional graphene-reinforced carbon fiber composite material possesses a three-dimensional porous all-carbon structure, exhibiting advantages such as low density, resistance to high and low temperatures, corrosion resistance, and good electrical conductivity, showing potential applications in fields such as thermal conductivity and electromagnetic shielding.

[0006] The aforementioned existing technology employs a process of immersing the entire fabric in a resin system and then curing it. After curing, the resin forms a continuous phase in the fiber gaps and on the surface, significantly restricting the relative slippage and bending deformation of the fabric fibers, thus causing the fabric to lose its original softness and breathability. Furthermore, the laser-induced graphene patterning is only applied to localized areas, meaning that the resin introduced and cured in areas not treated by the laser does not participate in the construction of the functional layer and is considered redundant material. Due to the lack of regional selectivity in its "overall impregnation-overall curing" process, it is impossible to form the necessary functional layer only in the target patterned area while preserving the fabric's inherent softness and breathability. Therefore, it inevitably leads to a decline in the overall performance of the fabric. Summary of the Invention

[0007] In view of the above-mentioned deficiencies of the prior art, the technical problem to be solved by the present invention is how to prepare a carbon-based conductive functional layer that is regionally selectively patterned on the surface of a target substrate and firmly bonded to the substrate without impregnating and curing the entire substrate or causing material transformation of the substrate body.

[0008] To achieve the above objectives, the present invention provides a method for preparing a conformal bonding interface enhanced laser-induced patterned graphene functional layer, comprising the following steps:

[0009] Step 1: Prepare a gradient porous polyamic acid gel membrane;

[0010] Step 2: Texture the surface of the target substrate, and pattern the gradient porous polyamic acid gel film by dividing it into sections and then conformally bonding and transferring it, or conformally bonding and transferring it and then patterning and dividing it to form a composite structure.

[0011] Step 3: Perform gradient heating thermal imidization on the transferred polyamic acid to obtain a patterned polyimide precursor;

[0012] Step 4: In situ generation of polymorphic graphene structures on patterned polyimide precursors via laser induction, followed by encapsulation and curing of the resulting polymorphic graphene structures.

[0013] Furthermore, the target substrate is a flexible fabric substrate or a fiber-reinforced composite planar, developable, and non-developable surface substrate, and the resin matrix of the flexible fabric substrate and the fiber-reinforced composite substrate satisfies the stability of the curing heating stage and the maximum curing temperature of 230℃.

[0014] Furthermore, in step one, a gradient porous polyamic acid gel membrane with different hierarchical structures is prepared using an adjustable solvent-inducible phase separation process. Step one includes the following steps:

[0015] The polyamic acid solution is evenly coated onto the surface of the release cloth;

[0016] Then, the coated polyamic acid solution is immersed in a coagulation bath and left to stand for 60–360 seconds to form a gradient porous polyamic acid gel membrane.

[0017] Subsequently, the gradient porous polyamic acid gel membrane was removed, and its surface moisture was removed using lint-free paper.

[0018] In step one, the polyamic acid solution is thermoplastic or thermosetting, with a solid content of 10-20 wt%, a viscosity of 5000-15000 cP, and a coating thickness of 20-300 μm. The release cloth is any one of Teflon, nylon, PET, or PTFE. The coagulation bath used is a mixture of anhydrous ethanol and deionized water in a volume ratio of 1:1 to 3:1.

[0019] Furthermore, step two includes the following steps:

[0020] The area of ​​the target substrate to be transferred is subjected to laser surface texturing treatment;

[0021] Next, anhydrous ethanol is sprayed onto the surface of the release cloth;

[0022] Then, for flexible fabric substrates and fiber-reinforced composite planar and developable target substrates, conformal bonding transfer and patterning segmentation or patterning segmentation and conformal bonding transfer are performed; for fiber-reinforced composite non-developable substrates, conformal bonding transfer and patterning segmentation are performed.

[0023] After hot pressing, allow the material to cool naturally and then remove the release cloth.

[0024] In step two, a laser is used for patterning and segmentation, and a hot-pressing process is used for conformal bonding and transfer.

[0025] The laser used for surface texturing was an ultrafast laser;

[0026] The laser used for patterned segmentation can be any one of CO2, nanosecond ultraviolet, infrared, green laser and ultrafast laser. The laser parameters for patterned segmentation are: scanning speed 50-200mm / s, frequency 50-80kHz, power 5-15W, and defocusing amount -10-+10mm.

[0027] The hot pressing process uses either flat plate hot pressing or vacuum bag hot pressing. The hot pressing process parameters are: temperature 100-150℃, pressure 0.1-1.0MPa, and hot pressing time 30-80s. The hot pressing laminate structure is: metal plate or vacuum bag - release cloth - target substrate - gradient porous polyamic acid gel film - release cloth - metal plate or vacuum bag.

[0028] Furthermore, in step three, the composite structure is placed in an oven for gradient heating and thermal imidization treatment.

[0029] The gradient heating thermal imidization process parameters are: 50-55℃ for 30-45 min, 70-75℃ for 30-45 min, 80-95℃ for 30-45 min, then heated to 230℃ for 1-1.5 h and then the power is cut off. The temperature is then maintained in the furnace for another 1-3 h.

[0030] Furthermore, in step four, the laser used for laser-induced processing is any one of CO2, ultraviolet, infrared, green laser, and ultrafast laser, and the laser parameters for laser-induced processing are scanning speed of 200-400 mm / s, line spacing of 0.05-0.2 mm, defocusing amount of -35-+35 mm, and power of 5-20 W.

[0031] Multimorphic graphene structures are three-dimensional conductive carbon structures with adjustable self-assembly sequences.

[0032] The encapsulation material used is a resin-based material.

[0033] Furthermore, after forming the polymorphic graphene structure, a portion of the polyimide precursor layer is retained as a bonding transition layer between the graphene and the target substrate.

[0034] Compared with the prior art, the present invention has the following advantages:

[0035] The graphene functional layer preparation method proposed in this invention can retain the original softness, air permeability and other properties of the matrix material; can improve the interfacial bonding strength between the functional layer and the matrix material, and ensure the performance and long-term durability of the functional layer; and can significantly improve the electromagnetic shielding effectiveness and broadband frequency selective wave transmission characteristics.

[0036] The following will further explain the concept, specific structure, and technical effects of the present invention in conjunction with the accompanying drawings, so as to fully understand the purpose, features, and effects of the present invention. Attached Figure Description

[0037] Figure 1 This is a schematic block diagram illustrating the steps of the conformal bonding interface enhancement laser-induced patterning graphene functional layer preparation method of the present invention.

[0038] Figure 2 This is a schematic diagram of the process flow for fabricating patterned LIG metasurface structures on high-silica flexible fabrics according to an embodiment of the present invention;

[0039] Figure 3 This is a schematic diagram of the process flow for fabricating patterned LIG metasurface structures on a non-developable surface of a dome structure according to an embodiment of the present invention;

[0040] Figure 4The patterned LIG metasurface structure prepared on the target substrate in this embodiment of the invention is as follows: (a) multimorphic three-dimensional LIG layer-by-layer self-assembly and (b) stable bonding of LIG-substrate interface. Detailed Implementation

[0041] The preferred embodiments of the present invention are described below with reference to the accompanying drawings to make the technical content clearer and easier to understand. The present invention can be embodied in many different forms, and the scope of protection of the present invention is not limited to the embodiments mentioned herein.

[0042] In the accompanying drawings, components with the same structure are indicated by the same numerical designation, and components with similar structures or functions are indicated by similar numerical designations. The dimensions and thicknesses of each component shown in the drawings are arbitrary, and the present invention does not limit the dimensions and thicknesses of each component. To make the illustrations clearer, the thickness of some components has been appropriately exaggerated in the drawings.

[0043] Currently, existing technologies have the following problems: the substrate surface is covered with a large amount of redundant precursor, the graphene is not firmly bonded to the substrate material, and the homogeneous precursor results in the generated graphene having a single structure and function.

[0044] To address the aforementioned problems, this invention proposes a method for preparing a conformal bonding interface-enhanced laser-induced patterned graphene functional layer, which can construct patterned carbon-based conductive metasurface structures on the surface of a target substrate, such as... Figure 1 As shown, it includes the following steps:

[0045] Step 1: Prepare a gradient porous polyamic acid gel membrane;

[0046] This step involves preparing gradient porous polyamic acid gel membranes with different hierarchical structures using an adjustable solvent-inducible phase separation process.

[0047] First, the polyamic acid solution is evenly coated onto the surface of the release cloth.

[0048] The polyamic acid solution has a solid content of 10–20 wt%, a viscosity of 5000–15000 cP, and a coating thickness of 20–300 μm. The coagulation bath used is a mixture of anhydrous ethanol and deionized water with a volume ratio of 1:1 to 3:1. The polyamic acid solution is thermoplastic or thermosetting, and the release cloth can be any of Teflon, nylon, PET, PTFE, etc.

[0049] Then, the coated thermoplastic polyamic acid solution is immersed in a coagulation bath and allowed to stand for 60–360 seconds to form a gradient porous polyamic acid gel membrane. The coagulation bath used is a mixture of anhydrous ethanol and deionized water with a volume ratio of 7:3.

[0050] Subsequently, the gradient porous polyamic acid gel membrane was removed, and its surface moisture was removed using lint-free paper.

[0051] Step 2: Texture the surface of the target substrate, and pattern the gradient porous polyamic acid gel film by dividing it into sections and then conformally bonding and transferring it, or conformally bonding and transferring it and then patterning and dividing it to form a composite structure.

[0052] The target substrate used in the graphene functional layer preparation method of this invention is a flexible fabric substrate or a fiber-reinforced composite material planar, developable, and non-developable surface substrate. The resin matrix of the flexible fabric substrate and the fiber-reinforced composite material substrate satisfies the stability of the curing heating stage and the maximum curing temperature is 230°C. The flexible fabric substrate can be any one of high-silica, carbon fiber, glass fiber, aramid fiber, etc. The reinforcement in the fiber-reinforced composite material can be any one of high-silica, carbon fiber, glass fiber, aramid fiber, etc. The developable surface can be a cylindrical surface, a conical surface, etc., and the non-developable surface can be an arc shell, a dome structure, etc.

[0053] In step two, for flexible fabric substrates and fiber-reinforced composite planar or developable surface target substrates, patterning and segmentation can be performed first, followed by conformal bonding and transfer, or conformal bonding and transfer can be performed first, followed by patterning and segmentation. For fiber-reinforced composite non-developable surface substrates, conformal bonding and transfer are performed first, followed by patterning and segmentation, to ensure the shape accuracy of the surface pattern.

[0054] First, the area of ​​the target substrate to be transferred is subjected to laser surface texturing treatment. The laser used for surface texturing treatment is an ultrafast laser such as a femtosecond or picosecond laser.

[0055] Next, anhydrous ethanol is sprayed onto the surface of the release cloth.

[0056] Then, for flexible fabrics, flat sheets, and developable target substrates, conformal bonding transfer and patterning segmentation or patterning segmentation and conformal bonding transfer are performed. For non-developable substrates, conformal bonding transfer and patterning segmentation are performed. Patterning segmentation is performed using a laser, and conformal bonding transfer is performed using a hot pressing process.

[0057] The laser used for patterned segmentation can be any one of CO2, nanosecond ultraviolet, infrared, green laser and ultrafast laser, with femtosecond and picosecond ultrafast lasers being preferred. The laser parameters for patterned segmentation are: scanning speed 50-200 mm / s, frequency 50-80 kHz, power 5-15 W, and defocusing amount -10 to +10 mm.

[0058] Depending on the shape of the substrate, either flat plate hot pressing or vacuum bag hot pressing is selected for the hot pressing process. The hot pressing process parameters are: temperature 100-150℃, pressure 0.1-1.0MPa, and hot pressing time 30-80s. The hot pressing laminate structure is: metal plate or vacuum bag - release cloth - target substrate - gradient porous polyamic acid gel film - release cloth - metal plate or vacuum bag.

[0059] Finally, allow the material to cool naturally after hot pressing, then remove the release cloth.

[0060] Step 3: Perform gradient heating thermal imidization on the transferred polyamic acid to obtain a patterned polyimide precursor;

[0061] In step three, the composite structure is placed in an oven for gradient heating and thermal imidization treatment.

[0062] The gradient temperature thermal imidization process parameters are: 50–55℃ for 30–45 min, 70–75℃ for 30–45 min, 80–95℃ for 30–45 min, then raised to 230℃ and held for 1–1.5 h before power is cut off, and the temperature is maintained in the furnace for another 1–3 h.

[0063] Step 4: In situ generation of polymorphic graphene structures on patterned polyimide precursors via laser induction, followed by encapsulation and curing of the resulting polymorphic graphene structures.

[0064] First, a laser is used to induce laser treatment on a patterned gradient porous polyimide precursor to form a multimorphic graphene structure.

[0065] The laser used for laser-induced processing can be any one of CO2, ultraviolet, infrared, green lasers, and ultrafast lasers (such as femtosecond and picosecond lasers). The laser parameters for laser-induced processing are: tracing speed 200-400 mm / s, line spacing 0.05-0.2 mm, defocusing amount -35-+35 mm, and power 5-20 W.

[0066] Among them, the multimorphic graphene structure is a three-dimensional conductive carbon structure with adjustable self-assembly sequence. By adjusting the non-solvent-induced phase separation process in step one, a gradient porous polyimide gel membrane with different hierarchical structures from top to bottom is prepared, thereby realizing the adjustable self-assembly sequence of the multimorphic graphene structure.

[0067] To further improve the interfacial bonding strength of the composite structure, a portion of the gradient porous polyimide precursor layer is retained after the formation of the multimorphic graphene structure as a bonding transition layer between the composite structure and the target substrate.

[0068] Then, the multimorphic graphene structures are encapsulated and cured. The encapsulation material used is a resin-based material.

[0069] The graphene functional layer preparation method of this invention can be applied to sensor manufacturing, electromagnetic interference shielding, and electrothermal conversion / heating. The graphene functional layer prepared by the graphene functional layer preparation method of this invention can be used in wearable electronics, flexible / smart materials and devices, etc.

[0070] The implementation and realization of the technical solution of the present invention will be further described below through specific embodiments. It should be noted that the implementation and realization of the technical solution of the present invention are not limited to the following embodiments.

[0071] Example 1

[0072] This embodiment constructs a patterned three-dimensional laser-induced graphene (LIG) metasurface structure on the surface of a high-silica flexible fabric substrate. The specific fabrication process is as follows: Figure 2 As shown, it includes the following steps:

[0073] Step 1: Preparation of gradient porous polyamic acid gel membrane

[0074] This step uses an adjustable solvent-induced phase separation process to obtain a gradient pore structure of "dense skin-porous core", providing a structural basis for subsequent high-precision patterning and thickness-direction energy deposition control.

[0075] First, a thermoplastic polyamic acid solution with a solid content of 15 wt%, a viscosity of approximately 13000 cP, and a film thickness of 150 μm is uniformly coated onto the smooth surface of a Teflon release cloth.

[0076] Then, the coated thermoplastic polyamic acid solution was immersed in a coagulation bath containing anhydrous ethanol / deionized water at a volume ratio of 7:3 and allowed to stand for 180 seconds to complete the solvent-inducing phase separation process. By controlling the composition ratio of the coagulation bath, the solvent system, and the phase separation time, the phase separation intensity of the ternary system can be regulated, thereby obtaining a gradient porous polyamic acid gel membrane (hereinafter referred to as the gel membrane) with a dense skin layer and a porous core layer.

[0077] Subsequently, the gradient porous polyamic acid gel membrane was removed, and its surface moisture was removed using lint-free paper.

[0078] The gel film prepared in this step has good extensibility and can be adhered to the surface of target substrates with different morphologies, such as flat plates, non-developable curved surfaces, and flexible fabrics.

[0079] Step 2: Texture the surface of the target substrate, pattern the gradient porous polyamic acid gel film, and then conformally bond and transfer it to the target substrate, or conformally bond and transfer it to the target substrate and then pattern it to form a composite structure. This step, without destroying the fiber continuity of the target substrate, constructs mechanically interlocking anchor points with high specific surface area and satisfying the force transmission law on the finite fiber surface through surface micro-nano texturing, so as to improve the interfacial bonding strength between the subsequent functional layer and encapsulation layer and the target substrate; at the same time, while maintaining the solvent / water content and extensibility of the gel film, high-precision patterning of the gel film is achieved, and the relative position of the pattern units is kept stable during the transfer process, reducing the risk of thermal impact and misalignment.

[0080] First, the areas of the high-silica flexible fabric substrate to be transferred are subjected to laser surface texturing treatment. Surface texturing is performed using ultrafast lasers such as femtosecond and picosecond lasers for scanning processing. Under the condition of not destroying the fiber continuity and not excessively weakening the fiber load-bearing capacity, a low spatial frequency, vertically oriented laser-induced periodic surface structure (LIPSS) is induced on the fiber surface. Through the LIPSS micro-nano structure, high specific surface area micro-nano undulations and directional textures are introduced on the finite fiber surface, forming mechanical interlocking anchor points that conform to the load transfer path. This provides a more effective mechanical interlocking interface for the subsequent transfer of the functional layer (gel film) and subsequent encapsulation resin, and together with the subsequent hot pressing, forms a more reliable interface bonding foundation, improving the interface peel resistance and durability reliability.

[0081] Next, anhydrous ethanol is sprayed onto the surface of the smooth Teflon release cloth; this allows the gel film to adhere to the Teflon release cloth and removes air from the bonding interface to form a tight bond.

[0082] Subsequently, femtosecond, picosecond, CO2, nanosecond ultraviolet, infrared, and green lasers were used to pattern the gel membrane, with femtosecond and picosecond lasers being preferred. Excess gel membrane was then peeled off, completing the preparation of the patterned gel membrane. The patterning of the gel membrane utilizes the liquid surface tension of ethanol, ensuring both adhesion between the patterned gel membrane and the Teflon release fabric and the removal of excess areas.

[0083] The laser parameters for patterning and segmenting the gel film were: scanning speed 80 mm / s, frequency 50 kHz, power 5 W, and defocusing amount 0. Anhydrous ethanol was introduced to reduce the heat accumulation effect during laser processing, thereby minimizing the risk of dehydration, melting, or deformation caused by the heat-affected zone. Simultaneously, the surface tension of the liquid was used to maintain the relative position of the segmented pattern units on the Teflon release fabric surface, reducing the overall misalignment probability caused by subsequent transfer operations.

[0084] Next, the patterned gel film is conformally bonded and transferred. During the transfer process, the Teflon release fabric carrying the patterned gel film is bonded to the surface of the textured target substrate, and then hot-pressed using a flatbed hot press.

[0085] The hot pressing process conditions are: temperature 125℃, pressure 0.1MPa, hot pressing time 60s, and the hot pressing laminate structure is aluminum alloy plate—Teflon—high silica flexible fabric—patterned gel film—Teflon—aluminum alloy plate.

[0086] Under hot-pressing conditions, the ethanol at the interface between the Teflon release fabric and the patterned gel film evaporates, reducing the interfacial tension between them and promoting their separation. Simultaneously, under pressure, the patterned gel film adheres tightly to the surface of the high-silica flexible fabric substrate, achieving interfacial fusion. After hot-pressing and natural cooling, the Teflon release fabric is removed, resulting in a composite structure with a patterned gel film locally formed on the surface of the high-silica flexible fabric substrate.

[0087] In step two, after texturing the surface of the high-silica flexible fabric target substrate, conformal bonding transfer can be performed first, followed by patterning and segmentation.

[0088] Step 3: Perform gradient-heat thermal imidization on the transferred polyimide acid to obtain patterned polyimide precursor.

[0089] This step selectively transfers the patterned precursor layer to the target area without impregnating and curing the entire target substrate, thus forming a tightly bonded interface.

[0090] The composite structure obtained in step two was placed in an oven for gradient heating thermal imidization treatment. The specific gradient heating thermal imidization process parameters were: 55℃ for 45 min, 75℃ for 45 min, 95℃ for 45 min, then heated to 230℃ for 1.5 h and the power was turned off, and the temperature was continued in the oven for 2-3 h.

[0091] Through the aforementioned gradient-heating thermal imidization treatment, moisture slowly escapes from the patterned gel film, reducing stress concentration caused by rapid evaporation and thus inhibiting the formation of defects such as cracks and pores, resulting in a tough patterned polyimide precursor layer. After thermal imidization curing, the patterned polyimide precursor retains its original gradient porous structure, and the pore structure may undergo scale changes due to pore expansion and local collapse during the curing process, giving it greater structural control space compared to homogeneous polyimide films. The porous structure enhances the design freedom and electromagnetic loss path construction capabilities in electromagnetic applications. This process yields a patterned polyimide precursor that is firmly bonded to a high-silica flexible fabric substrate, providing an interfacial basis for the subsequent in-situ generation of carbon-based conductive structures.

[0092] Step 4: In-situ generation of polymorphic graphene structures on patterned polyimide precursors via laser induction, followed by encapsulation and curing of the resulting polymorphic graphene structures.

[0093] This step controls the rate of moisture / residual solvent escape by segmented heating, suppressing defects such as cracks and pores, while preserving and stabilizing the gradient porous structure.

[0094] First, the patterned polyimide precursor obtained in step three is subjected to laser-induced treatment using femtosecond, picosecond, CO2, ultraviolet, infrared, and green lasers. The laser-induced parameters are: scanning speed 250 mm / s, line spacing 0.12 mm, defocusing amount +30 mm, and power 5 W, thereby generating a three-dimensional LIG metasurface structure in situ in the patterned area.

[0095] The aforementioned laser-induced process, by controlling the deposition of laser energy along the thickness direction of the patterned polyimide precursor, couples the porous structure with the energy deposition distribution, promoting the formation of a multi-morphological self-assembled three-dimensional conductive carbon structure. This three-dimensional conductive carbon structure, from top to bottom along the thickness direction, sequentially presents a layer of nanospherical particles (corresponding to the dense skin region), a layered stacked structure (corresponding to the skin-core transition region), and a porous carbon structure (corresponding to the porous core region).

[0096] To ensure the interfacial bonding strength of the composite structure, a portion of the polyimide precursor layer can be retained after the formation of the three-dimensional conductive structure as a bonding transition layer between the polyimide precursor layer and the high-silica flexible fabric substrate.

[0097] Then, the obtained LIG structure is encapsulated using a resin system as the encapsulation material and cured to allow the resin to penetrate into the porous LIG and the interface area of ​​the target substrate treated with laser texturing, forming a protective layer and improving structural stability and interface bonding reliability.

[0098] Example 2

[0099] This embodiment constructs a patterned LIG metasurface structure on the surface of a fiber-reinforced composite non-developable surface substrate.

[0100] Based on Example 1, the difference from Example 1 is that the non-developable surface of the target substrate is a dome structure. Step two involves texturing the surface of the target substrate, conformally bonding and transferring the gradient porous polyamic acid gel film to the target substrate, and then patterning and segmenting it to form a composite structure. All other steps are the same. The specific preparation process is as follows: Figure 3 As shown.

[0101] Because the gradient porous polyamic acid gel film obtained in step one has extensibility, in step two, the dome structure substrate is first conformally bonded and transferred, and then patterned and segmented by contour-focused focusing to ensure the shape accuracy of the curved pattern. Subsequently, steps three and four yield a patterned three-dimensional LIG metasurface structure and its encapsulation layer that are firmly bonded to the curved substrate. Figure 4 The image shows a patterned LIG metasurface structure prepared on a target substrate according to an embodiment of the present invention.

[0102] The method proposed in this invention can address and solve the technical problems of "regional selective construction, avoiding substrate transformation, ensuring the accuracy and alignment of complex patterns, improving interface adhesion, realizing three-dimensional programmable conductive structures and packaging durability", and the specific technical effects are as follows:

[0103] (1) A gradient porous gel membrane with a dense skin and a porous core was prepared by using a non-solvent-induced phase separation process and precisely controlling the composition of the coagulation bath and the phase separation time. This gel membrane can provide a complete surface bearing / processing interface, provide internal porous channels and adjustable structural space, and maintain high extensibility of the membrane. Therefore, it can achieve regional selective functionalization by "local membrane transfer" without overall impregnation and curing of the substrate. This fundamentally avoids the common constraints on the softness, air permeability and deformability of fabrics caused by redundant curing of non-functional areas due to overall impregnation and curing. Unlike most existing prefabricated PI, PET and other precursor films, the gel membrane made in this invention intentionally constructs a porous structure from the precursor step, laying a good precursor foundation for the subsequent generation of multi-morphological self-assembled three-dimensional LIG. The gel membrane of this invention has adjustable thickness, adjustable composition, and adjustable structure. It only requires a simple process of thoroughly mixing the loaded ions with polyamic acid and coating it to the target thickness. A morphologically stable gel membrane can be achieved through a phase separation step, avoiding the disadvantage of existing methods in terms of uncontrollable solution wetting thickness.

[0104] (2) Anhydrous ethanol is introduced into the interface between the gel film and the release cloth and nanosecond ultraviolet laser patterning is performed. The evaporation and heat absorption of ethanol and the heat conduction buffering effect will reduce the heat accumulation of laser processing, which will inevitably reduce the probability of dehydration, melting and deformation caused by heat-affected zone. At the same time, the liquid tension formed by ethanol at the interface will constrain the position of the patterned units after segmentation, thus improving the quality of the pattern boundary and maintaining the relative position stability of the array units, thereby meeting the requirements of dimensional accuracy and alignment consistency of complex high-resolution structures such as sensor electrodes and metasurface arrays.

[0105] (3) Using a flat plate heat transfer with specific temperature and pressure, the evaporation of ethanol during the heat transfer process will reduce the interfacial tension of the release cloth-gel film and promote natural peeling. Pressure and temperature together promote the tight adhesion and interfacial fusion between the gel film and the target substrate. Therefore, this process will inevitably form a stable patterned precursor layer connection on the surface of the target substrate, reducing the problem of limited interfacial bonding inherent in adhesive bonding / lamination.

[0106] (4) Gradient heating thermal imidization is performed on the local polyamic acid pattern area after transfer. The segmented heating reduces the rate of water and residual solvent evaporation, which inevitably weakens the stress concentration caused by rapid evaporation, thereby suppressing defects such as cracks and pores and preserving the gradient porous structure, providing a complete and controllable porous interface foundation for the subsequent construction of conductive structures.

[0107] (5) Laser induction under defocus conditions is used on gradient porous polyimide precursor. The deposition distribution of laser energy in the thickness direction can be modulated and coupled with the structural gradient of "dense skin-porous core". Therefore, it is possible to induce the formation of three-dimensional conductive carbon structures with different morphologies along the thickness direction in the same pattern area, expand the adjustable window of electrical / dielectric properties of carbon-based functional layers, and overcome the lack of spatial selectivity of overall furnace carbonization and the difficulty in achieving controllable deposition of energy in the thickness direction, resulting in a single morphology and limited performance control.

[0108] (6) The substrate surface is induced by femtosecond / picosecond laser to form a low-frequency, vertically oriented LIPSS texture. Without destroying the fiber continuity, it will inevitably increase the effective specific surface area and form mechanical interlocking anchor points that conform to the load transfer direction. Combined with the wetting and curing of porous LIG and interface by encapsulation resin, it will inevitably enhance the mechanical interlocking and anti-peeling ability between the functional layer / encapsulation layer and the substrate, and improve the interface stability and long-term functional retention under bending, friction and environmental aging conditions.

[0109] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A method for preparing a conformal bonding interface-enhanced laser-induced patterned graphene functional layer, characterized in that, The steps include the following: Step 1: Prepare gradient porous polyamic acid gel membranes with different hierarchical structures using an adjustable non-solvent-induced phase separation process; A polyamic acid solution is uniformly coated onto the surface of a release cloth. The polyamic acid solution is thermoplastic or thermosetting, and has a solid content of 10-20 wt%, a viscosity of 5000-15000 cP, and a coating thickness of 20-300 μm. The release cloth is any one of Teflon, nylon, PET, and PTFE. Then, the coated polyamic acid solution is immersed in a coagulation bath and left to stand for 60–360 seconds to form a gradient porous polyamic acid gel membrane. The coagulation bath used is a mixture of anhydrous ethanol and deionized water with a volume ratio of 1:1 to 3:

1. Subsequently, the gradient porous polyamic acid gel membrane was removed and its surface moisture was removed using lint-free paper. Step 2: The surface of the target substrate is textured, and the gradient porous polyamic acid gel film is patterned and segmented and then conformally bonded and transferred, or conformally bonded and transferred and then patterned and segmented to form a composite structure. The target substrate is subjected to laser surface texturing treatment on the area to be transferred. The target substrate is a flexible fabric substrate or a fiber-reinforced composite material planar, developable, and non-developable surface substrate. The resin matrix of the flexible fabric substrate and the fiber-reinforced composite material substrate meets the requirements of stability during the curing heating stage and a maximum curing temperature of 230°C. The laser used for surface texturing treatment is an ultrafast laser. Anhydrous ethanol is sprayed onto the surface of the release cloth; For the flexible fabric substrate and the fiber-reinforced composite planar and developable surface target substrate, conformal bonding transfer and patterning segmentation or patterning segmentation and conformal bonding transfer are performed. For the fiber-reinforced composite non-developable surface substrate, conformal bonding transfer and patterning segmentation are performed. Patterned segmentation is performed using a laser. The laser used for patterned segmentation can be any one of CO2, nanosecond ultraviolet, infrared, green laser, and ultrafast laser. The laser parameters for patterned segmentation are: scanning speed 50-200 mm / s, frequency 50-80 kHz, power 5-15 W, and defocusing amount -10 to +10 mm. Conformal bonding transfer is performed using a hot pressing process. The hot pressing process uses either a flat plate hot pressing process or a vacuum bag hot pressing process. The hot pressing process parameters are: temperature 100-150℃, pressure 0.1-1.0MPa, and hot pressing time 30-80s. The hot pressing laminate structure is: metal plate or vacuum bag - release cloth - target substrate - gradient porous polyamic acid gel film - release cloth - metal plate or vacuum bag. After hot pressing and natural cooling, the release cloth is removed, and after patterned segmentation, excess gradient porous polyamic acid gel film is peeled off. Step 3: Perform gradient heating thermal imidization on the transferred polyamic acid to obtain a patterned polyimide precursor; Step 4: In situ generation of polymorphic graphene structures on the patterned polyimide precursor by laser induction, and encapsulation and curing of the obtained polymorphic graphene structures.

2. The method for preparing a conformal bonding interface enhanced laser-induced patterned graphene functional layer as described in claim 1, characterized in that, In step three, the composite structure is placed in an oven for gradient heating and thermal imidization treatment.

3. The method for preparing a conformal bonding interface enhanced laser-induced patterned graphene functional layer as described in claim 2, characterized in that, The gradient heating thermal imidization process parameters are: 50-55℃ for 30-45 min, 70-75℃ for 30-45 min, 80-95℃ for 30-45 min, then heated to 230℃ for 1-1.5 h and the power is cut off, and the temperature is continued to be maintained in the furnace for 1-3 h.

4. The method for preparing a conformal bonding interface enhanced laser-induced patterned graphene functional layer as described in claim 1, characterized in that, In step four, the laser used for laser-induced processing is any one of CO2, ultraviolet, infrared, green laser and ultrafast laser. The laser parameters for laser-induced processing are scanning speed 200-400 mm / s, line spacing 0.05-0.2 mm, defocusing amount -35-+35 mm, and power 5-20 W. The multimorphic graphene structure is a three-dimensional conductive carbon structure with adjustable self-assembly sequence. The encapsulation material used is a resin-based material.

5. The method for preparing a conformal bonding interface enhanced laser-induced patterned graphene functional layer as described in claim 1, characterized in that, After forming the polymorphic graphene structure, a portion of the polyimide precursor layer is retained as a bonding transition layer between the graphene and the target substrate.

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