Three-dimensional composite film and preparation method thereof

Abstract

The invention belongs to the technical field of three-dimensional micro-nano manufacturing, and discloses a three-dimensional composite film and a preparation method thereof.The method comprises the steps that a conductive functional structure is prepared on the surface of a prepared high-molecular polymer composite double-layer stress film; the high-molecular polymer composite double-layer stress film comprises a first high-molecular polymer film and a second high-molecular polymer film arranged on the surface of the first high-molecular polymer film, and the swelling ratio of the first high-molecular polymer film is different from that of the second high-molecular polymer film; the conductive functional layer is prepared on the surface of the second high-molecular polymer film; then cutting to obtain a planar composite double-layer stress film; and the planar composite double-layer stress film is subjected to swelling deformation in a solvent, and the three-dimensional composite film in a preset shape is obtained. According to the method, a stress difference introduction strategy based on a swelling mechanism is utilized, so that integrated curling forming manufacturing of the flexible polymer functional film is realized.

Description

Technical Field

[0001] The invention belongs to the technical field of three-dimensional micro-nano manufacturing, and specifically relates to a three-dimensional composite film and a preparation method thereof. Background Art

[0002] Self-curling technology is a three-dimensional micro-nano self-assembly technology that uses internal gradient stress or external force to drive a two-dimensional film into a three-dimensional configuration. It is compatible with typical planar micro-nano manufacturing processes, can realize multi-level three-dimensional micro-nano structure manufacturing, and can selectively carry or integrate a variety of functional materials. While greatly improving the miniaturization and integration of devices, it can also introduce other effects or functions, such as realizing the regulation of the band structure of functional materials, optimizing and enhancing electrical / optical properties, etc., effectively solving the problem of low applicability of two-dimensional planar devices in small spaces, and thus has become a hot spot in current cutting-edge scientific research.

[0003] However, the currently commonly used self-curling technology is mainly applicable to semiconductor materials. Based on the difference in lattice constants of semiconductor materials, the purpose of releasing the internal stress of the double-layer semiconductor film is achieved by selectively etching the sacrificial layer, thereby achieving stress mismatch and realizing the assembly of three-dimensional self-curling microtubes, spiral structures, etc. under the drive of stress difference. This semiconductor self-curling technology often requires the introduction of a sacrificial layer during the processing process. The high etching selectivity between the sacrificial layer and the stress film is the key to the successful release of stress. In principle, the sacrificial layer must be removed without etching / damaging the stress film, which increases the process difficulty and manufacturing cost while also greatly limiting the range of material selection. Therefore, developing a new self-curling forming and manufacturing process with simple process, low cost, and a wide range of material selection to overcome the problems and shortcomings of the existing technology is of great practical significance for the further development of self-curling technology in the field of three-dimensional electronic devices. Summary of the invention

[0004] In order to solve the problems existing in the prior art, the purpose of the present invention is to provide a three-dimensional composite film and a preparation method thereof. The present invention utilizes a stress difference introduction strategy based on the swelling mechanism to achieve integrated curling and forming manufacturing of flexible polymer functional films.

[0005] To achieve the above object, the technical solution adopted by the present invention is as follows: A method for preparing a three-dimensional composite film comprises the following steps: A conductive functional structure is prepared on the surface of a prepared high molecular polymer composite double-layer stress film; the high molecular polymer composite double-layer stress film comprises a first high molecular polymer film and a second high molecular polymer film disposed on the surface of the first high molecular polymer film, the swelling rate of the first high molecular polymer film is different from the swelling rate of the second high molecular polymer film; the conductive functional layer is prepared on the surface of the second high molecular polymer film; Cutting the high molecular polymer composite double-layer stress film with the conductive functional layer prepared thereon to obtain a planar composite double-layer stress film; The planar composite double-layer stress film is swelled and deformed in a solvent to obtain a three-dimensional composite film with a preset shape.

[0006] Preferably, the final shape of the three-dimensional composite film is controlled by controlling the thickness of the first polymer film, the thickness of the second polymer film, the inner angle of the planar composite double-layer stress film and the side length ratio of the planar composite double-layer stress film.

[0007] Preferably, the planar composite double-layer stress film has a shape of a parallelogram. When the inner angle of the planar composite double-layer stress film is 90°, the three-dimensional composite film has a shape of a rolled tube structure.

[0008] Preferably, the planar composite double-layer stress film has a shape of a parallelogram. When the inner angle of the planar composite double-layer stress film is not equal to 90°, the shape of the three-dimensional composite film is a spiral structure.

[0009] Preferably: the preparation process of the first high molecular polymer film comprises: spin coating a first high molecular polymer precursor solution on the front side of the silicon wafer by spin coating, and obtaining the first high molecular polymer film after drying and peeling; The preparation process of the second high molecular polymer film includes: spin coating a second high molecular polymer precursor liquid on the front side of the silicon wafer by spin coating, and obtaining the second high molecular polymer film after drying and stripping.

[0010] Preferably, the first high molecular polymer film and the second high molecular polymer film are prepared into the high molecular polymer composite double-layer stress film by heat pressing.

[0011] Preferably, the first high molecular polymer film is a polyvinyl chloride film, and the second high molecular polymer film is a polyimide film.

[0012] Preferably, the solvent is acetone.

[0013] The present invention also provides a three-dimensional composite film, which is prepared by the preparation method of the present invention as described above.

[0014] Preferably, the conductive functional structure is a conductive layer or an electrode structure.

[0015] Compared with the prior art, the present invention has the following beneficial technical effects: In the preparation method of the three-dimensional composite film of the present invention, since the swelling rate of the first polymer film is different from that of the second polymer film, after the planar composite double-layer stress film is placed in a solvent, the first polymer film and the second polymer film will, under the action of the solvent, cause the planar composite double-layer stress film to swell unevenly and generate internal stress inside, thereby inducing the planar composite double-layer stress film to undergo uneven deformation, and finally obtaining a three-dimensional composite film. In the present invention, the final shape of the three-dimensional composite microfilm can be controlled by the swelling rate and thickness of the first polymer film, the swelling rate and thickness of the second polymer film, the shape of the planar composite double-layer stress film after cutting, and the selected solvent. It can be seen that the present invention utilizes a stress difference introduction strategy based on the swelling mechanism to achieve integrated curling and forming manufacturing of flexible polymer functional films. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematic diagram of the preparation process of the three-dimensional composite film in an embodiment of the present invention; In the figure: 1-high molecular polymer film with no swelling effect or low swelling rate, 2-high molecular polymer film with relatively high swelling rate, 3-rolled tube structure, 4-spiral structure, among which, is the inner angle of the planar composite film, L is the length of the planar composite film, W is the width of the planar composite film, and H is the height of the planar composite film. DETAILED DESCRIPTION

[0017] Hereinafter, the specific embodiments of the present application will be described in detail with reference to the accompanying drawings. According to these detailed descriptions, those skilled in the art can clearly understand the present application and can implement the present application. Without violating the principles of the present application, the features in the various embodiments can be combined to obtain new implementations, or certain features in certain embodiments can be replaced to obtain other preferred implementations.

[0018] The main ideas and principles used in the technical solution of the present invention are as follows: Swelling is a phenomenon in which the volume of a polymer expands in a solvent, which is caused by the diffusion of the solution molecules inside. Under the action of the solvent, the asymmetry of the microstructure of the polymer film will cause uneven swelling, and internal stress will be generated inside the polymer film, thereby inducing the polymer film to bend or twist and deform.

[0019] The technical solution of the present invention is a flexible self-curling method based on swelling induction, which is mainly aimed at a flexible double-layer film composed of high molecular polymers with different swelling rates.

[0020] Selection of swelling polymer film materials: The selection of polymer film determines the magnitude of stress difference, which directly affects the geometric structure of the self-curling three-dimensional structure. The present invention is directed to polymer films with different swelling rates. The bottom film is a polymer material with swelling effect, and the top film is a polymer material with no swelling or low swelling effect, which ultimately achieves the matching of double-layer stress films. For the above-selected double-layer stress film type, a corresponding solvent is selected. The selection of the solvent can be directly selected based on experimental results or known solvents corresponding to known materials.

[0021] For details, see Figure 1 The method for preparing the three-dimensional composite film of the present invention comprises the following steps: A conductive functional structure is prepared on the surface of a prepared high molecular polymer composite double-layer stress film; wherein the high molecular polymer composite double-layer stress film comprises a first high molecular polymer film and a second high molecular polymer film disposed on the surface of the first high molecular polymer film, and the swelling rate of the first high molecular polymer film is different from the swelling rate of the second high molecular polymer film; the conductive functional layer is prepared on the surface of the second high molecular polymer film; Cutting the high molecular polymer composite double-layer stress film with the conductive functional layer prepared thereon to obtain a planar composite double-layer stress film; The planar composite double-layer stress film is swelled and deformed in a solvent to obtain a three-dimensional composite film with a preset shape.

[0022] In the above scheme of the present invention, a three-dimensional composite film of a preset shape can be obtained by controlling the swelling rate and thickness of the first polymer film, the swelling rate and thickness of the second polymer film, the shape of the planar composite double-layer stress film after cutting, and the selected solvent.

[0023] The shape of the three-dimensional composite film can be theoretically calculated based on the above parameters, pre-set, and then obtained through experimental verification; it can also be obtained through multiple experiments. Specifically, the control variable method can be used to study the internal angle of the geometric shape of the double-layer film in different planes. , thickness, aspect ratio and the intrinsic relationship between the self-curling configuration and the characteristic size of the configuration, further explore the regulation mechanism of external physical factors such as temperature, time, etc. and the characteristic size of the self-curling configuration, characterize and analyze important parameters such as the micromorphology and characteristic size of the three-dimensional curling structure, reveal the influence of process parameters on the self-curling microstructure and morphology, and realize the preparation of different self-curling configurations. The final shape of the above-mentioned three-dimensional composite film of the present invention can be determined by the above-mentioned two methods. The present invention does not limit the specific method. The main task of the present invention is to provide the above-mentioned preparation ideas and mechanisms, and the final shape of the three-dimensional composite film can be set according to the needs of the user.

[0024] The above scheme of the present invention can prepare a typical three-dimensional composite film with a roll tube structure and a spiral structure. Specifically, when preparing capacitors of the above two structures, the shape of the planar composite double-layer stress film is a long strip, and the typical long strip is a rectangle (in this case, the inner angle is 90°) or a parallelogram (in this case, the inner angle is not equal to 90°). Correspondingly, when the inner angle of the shape of the planar composite double-layer stress film is 90°, the final shape of the obtained three-dimensional composite film is a roll tube structure. When the inner angle of the shape of the planar composite double-layer stress film is not equal to 90°, the shape of the obtained three-dimensional composite film is a spiral structure. At this time, the spiral angle is closely related to the size of the inner angle, and the final shape of the spiral structure can be obtained through multiple tests. The corresponding relationship between film parameters (such as parameters of the first high molecular polymer film (such as material, thickness, swelling rate), parameters of the second high molecular polymer film (such as material, thickness, swelling rate), the inner angle of the planar composite double-layer stress film and the side length ratio of the planar composite double-layer stress film) and the final shape of the solvent and the three-dimensional composite film can be established through multiple implementations, so that a three-dimensional composite film of a preset shape can be quickly obtained in actual preparation. The specific method can be operated by those skilled in the art according to actual conditions, and the present invention does not limit it in detail.

[0025] A typical method for preparing the three-dimensional composite film of the present invention comprises the following steps: Step 1, spin coating a polymer precursor solution with a high swelling rate on the front side of the silicon wafer by a spin coating method, and obtaining a polymer film with a high swelling rate after high temperature drying and stripping process; Step 2, spin coating a polymer precursor solution without swelling effect on the front side of the silicon wafer by spin coating, and obtaining a polymer film without swelling effect after high temperature drying and stripping process; Step 3, compounding the films obtained in step 1 and step 2 by hot pressing to prepare a polymer composite double-layer stress film with different swelling rates; wherein the polymer without swelling effect is used to make the upper layer of the flexible double-layer composite film, and the polymer with high swelling rate is used to make the bottom layer of the flexible double-layer composite film; Step 4, preparing a conductive functional structure on the surface of the high molecular polymer composite double-layer stress film; Step 5: Cut the high molecular polymer composite double-layer stress film with conductive functional structure by laser cutting to prepare different body geometric dimensions (such as inner angle θ , thickness d, aspect ratio L / W, etc.), and placing the planar composite double-layer stress film in a quantitative solvent to achieve the preparation of different self-curling coils or spiral configurations. Among them, by adjusting the geometric dimensions of the double-layer composite film body (such as the inner angle θThe microscopic morphology and characteristic size of the self-curling configuration can be regulated by adjusting the thickness H, aspect ratio L / W, etc., to achieve the preparation of multi-level self-curling configurations such as tubular and spiral shapes.

[0026] When selecting a solvent in the above solution of the present invention, it is necessary to select a corresponding solvent according to the above selected double-layer stress film type.

[0027] In the above solution of the present invention, the conductive functional structure can be a conductive layer or an electrode structure: When the conductive functional structure adopts a conductive layer and the internal angle is not equal to 90°, the three-dimensional composite micro-film can be directly used as a flexible strain sensor, and the conductive layer can adopt a graphene layer generated by laser induction; When the conductive functional structure adopts a conductive electrode structure and the internal angle is equal to 90°, the three-dimensional composite micro-film can be further processed into a supercapacitor. Specifically, a liquid crystal electrolyte can be added to the three-dimensional composite micro-film to obtain a micro-supercapacitor. Specifically, the electrode structure can adopt an interdigitated electrode. When preparing the conductive functional structure, a positive electrode needs to be prepared on one side of the interdigitated electrode and a negative electrode needs to be prepared on the other side.

[0028] The present invention provides a feasible embodiment. In this embodiment, a polyvinyl chloride / polyimide (PVC / PI) double-layer composite film is taken as an example, wherein the thickness of the PVC film is 50-100 microns, the thickness of the PI is 30-100 microns, and acetone is selected as a solvent to realize the preparation of the above-mentioned micro supercapacitor.

[0029] The main technical indicators that the micro supercapacitor can achieve are as follows: 1. Curling rate ≥ 20 μm / s, minimum curling radius ≤ 300 μm; 2. The projected area of ​​the supercapacitor is reduced by 3 times, the capacitance and energy density are increased by 3 times, the electrochemical impedance is ≤100 Ω, and the energy storage area capacitance is 21 mF cm -2 , areal energy density 15.9 μWh cm -2 .

[0030] In the present invention, the double-layer composite film after hot pressing is subjected to the action of the solvent, when the internal stress F of the high-swelling polymer is large enough, the stress-released double-layer film tends to roll into a tube and its topological structure. By adjusting the shape of the planar film, the preparation of different self-rolling configurations can be achieved, such as when the internal angle 90 o When the inner angle is not equal to 90, the double-layer flat film will curl into a coiled tube structure under the action of the corresponding solvent; oWhen the double-layer planar film is rolled up into a spiral structure, the microscopic morphology and characteristic size of the self-rolling configuration can be adjusted by adjusting the geometric dimensions of the double-layer composite film (such as thickness H, aspect ratio L / W, etc.), and the preparation of multi-level self-rolling configuration can be achieved.

[0031] It can be seen from the above scheme that the technical solution of the present invention has the following characteristics: ① The present invention abandons the preparation and selective etching process of the etching layer in the existing self-curling process, simplifies the preparation process, improves operational safety, and can further reduce processing costs.

[0032] ② The process method of the present invention is based on the swelling mechanism, has a wide range of material options, a short reaction time, can be manufactured on a large scale, and can control the configuration and performance through process parameters.

[0033] ③ Based on the reversibility of the swelling process, the present invention can realize the controllable and repeated switching of flexible three-dimensional / two-dimensional structures, improve the flexibility of functional device processing, and overcome the problem of poor stability of the curled structure.

[0034] The realization of the above new ideas and new methods of the present invention is expected to solve the problems and shortcomings that are common in the existing three-dimensional assembly technology research, such as high cost, complex process flow, time-consuming, narrow range of optional materials, and poor controllability. It provides an effective new mechanism and new process for three-dimensional micro-nano assembly technology, promotes the further development of three-dimensional assembly technology, and has broad application prospects in the fields of flexible electronic device development and on-chip laboratory construction.

[0035] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and implementation modes. They can be fully applied to the fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the equivalent scope of the claims, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A method for preparing a three-dimensional composite film, characterized in that: The process includes the following: A conductive functional structure is prepared on the surface of a prepared high molecular polymer composite double-layer stress film; the high molecular polymer composite double-layer stress film comprises a first high molecular polymer film and a second high molecular polymer film disposed on the surface of the first high molecular polymer film, the swelling rate of the first high molecular polymer film is different from the swelling rate of the second high molecular polymer film; the conductive functional layer is prepared on the surface of the second high molecular polymer film; Cutting the high molecular polymer composite double-layer stress film with the conductive functional layer prepared thereon to obtain a planar composite double-layer stress film; The planar composite double-layer stress film is swelled and deformed in a solvent to obtain a three-dimensional composite film with a preset shape.

2. The method for preparing a three-dimensional composite micro-film according to claim 1, characterized in that: The final shape of the three-dimensional composite micro-film is controlled by controlling the thickness of the first polymer film, the thickness of the second polymer film, the inner angle of the planar composite double-layer stress film and the side length ratio of the planar composite double-layer stress film.

3. The method for preparing a three-dimensional composite film according to claim 1, characterized in that: The shape of the planar composite double-layer stress film is a parallelogram. When the inner angle of the planar composite double-layer stress film is 90°, the shape of the three-dimensional composite film is a rolled tube structure.

4. The method for preparing a three-dimensional composite film according to claim 1, characterized in that: The shape of the planar composite double-layer stress film is a parallelogram. When the inner angle of the shape of the planar composite double-layer stress film with the preset body geometric dimensions is not equal to 90°, the shape of the three-dimensional composite film is a spiral structure.

5. The method for preparing a three-dimensional composite film according to claim 1, characterized in that: The preparation process of the first high molecular polymer film comprises: spin coating a first high molecular polymer precursor solution on the front side of the silicon wafer by spin coating, and obtaining the first high molecular polymer film after drying and peeling; The preparation process of the second high molecular polymer film includes: spin coating a second high molecular polymer precursor liquid on the front side of the silicon wafer by spin coating, and obtaining the second high molecular polymer film after drying and stripping.

6. The method for preparing a three-dimensional composite film according to claim 1, characterized in that: The first high molecular polymer film and the second high molecular polymer film are prepared into the high molecular polymer composite double-layer stress film by hot pressing.

7. The method for preparing a three-dimensional composite film according to claim 1, characterized in that: The first high molecular polymer film is a polyvinyl chloride film, and the second high molecular polymer film is a polyimide film.

8. The method for preparing a three-dimensional composite film according to claim 7, characterized in that: The solvent used is acetone.

9. A three-dimensional composite film, characterized in that: The three-dimensional composite film is prepared by the method for preparing a three-dimensional composite film according to any one of claims 1 to 8.

10. A three-dimensional composite film according to claim 9, characterized in that: The conductive functional structure is a conductive layer or an electrode structure.

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