A method of fabricating a flexible fiber integrated circuit

Abstract

The present application belongs to the technical field of intelligent electronic devices, and particularly relates to a preparation method of a flexible fiber integrated circuit. The method comprises the following steps: taking a micron-level polymer elastomer film as a base material, taking a high-modulus island-shaped polymer film as a buffer layer, and using an electronic device micro-nano processing preparation process and a multi-layer roll film assembly method to prepare the flexible fiber integrated circuit. The present application uses the high-modulus island-shaped polymer film layer as the buffer layer, which greatly enhances the stability of the performance of the electronic device when the electronic device on the fiber platform undergoes various deformations. The roll film method introduces the advanced high-precision preparation process (such as photolithography, etching, etc.) of the planar electronic device into the preparation of the fiber electronic device, realizes the integration of various high-precision and high-density electronic devices at the micro-nano scale, including resistors, capacitors, transistors, diodes and the like. The inner roll and the outer roll improve the protection of the electronic device and the convenience of electrode leading-out, respectively, and expand the application range of the fiber integrated circuit, such as in-vivo implantation, weaving into electronic fabrics and the like.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of intelligent electronic devices, and particularly relates to a preparation method of a flexible fiber integrated circuit. BACKGROUND

[0002] Wearable devices are a new generation of electronic devices, which have advantages such as light weight, flexibility, high integration and multi-functionality. Among them, fiber electronic devices can be integrated with fabrics through weaving methods. Compared with traditional flexible planar membrane devices, fiber electronic devices have higher flexibility, deformation stability and do not lose the air permeability of fabrics, and have a wide application prospect in emerging fields such as Internet of Things, artificial intelligence and health monitoring. High-precision and large-scale electronic device integration is the basis for modern information technology applications. However, the existing preparation process of fiber electronic devices is based on simple coating or extrusion process, and special fibers loaded with functional materials are obtained, and then the device is assembled through wrapping, twisting and weaving. The size of the fiber device obtained by the existing technology is at least in the millimeter level. How to realize the patterned deposition of functional materials and the integration of micro electronic devices in the micron scale of a single fiber is still a problem that cannot be solved, thereby limiting the development of fiber electronic devices to high integration and functionalization. Therefore, the present application develops a preparation method of a roll film to form a multi-layer electronic integrated structure inside the fiber, and obtains a flexible fiber electronic integrated circuit. At the same time, through device structure design (such as adding a high modulus island-shaped structure buffer layer), the stability of the fiber integrated circuit under various deformations is ensured. SUMMARY

[0003] The present application aims to solve the problem that the current preparation process of fiber electronic devices can only prepare millimeter-level functional devices and cannot prepare micron-scale high-precision and high-integration fiber electronic devices. The present application provides a preparation method of a flexible fiber integrated circuit.

[0004] The preparation method of the flexible fiber integrated circuit provided by the present application has the following specific steps:

[0005] (1) preparing a coiled high molecular substrate;

[0006] (2) preparing a high modulus polymer buffer layer;

[0007] (3) preparing a conductive circuit with good conductivity;

[0008] (4) preparing a functional material film layer to realize the function of electronic devices;

[0009] (5) the polymer substrate obtained in step (1), the polymer buffer layer obtained in step (2), the conductive path obtained in step (3) and the functional material film layer obtained in step (4) are prepared into a multi-layer flexible fiber integrated circuit in a roll film mode; the roll film mode can be divided into an outer roll film and an inner roll film according to the positions of the devices; during the roll film process, the elastomer film is separated from the low surface energy substrate, and the films are adhered to each other to form a stable fiber structure; after the roll film process is completed, the films carrying the devices are stacked in the form of layer-by-layer winding to become a fiber integrated circuit with a diameter of 50-5000 microns.

[0010] In the present application, the polymer substrate in step (1) is composed of a low surface energy substrate and an elastomer film. The low surface energy substrate is a smooth plane modified by perfluorination, and the specific material is any one of a fluorinated graft modified silicon wafer, a polyester sheet and the like. The specific material of the elastomer film can be any one of a silicone rubber, a polyurethane, a styrene-butadiene-styrene block copolymer (SBS), a hydrogenated styrene-butadiene block copolymer (SEBS) and the like. The thickness of the elastomer film is 2-30 microns, and the film is prepared by a spin coating method, a blade coating method or a spraying method.

[0011] In the present application, the polymer buffer layer with high modulus in step (2) is made of a polymer material with higher modulus, such as any one of polyvinyl alcohol, polyimide, polystyrene, polyethylene terephthalate, polyethylene, polypropylene and the like. The polymer buffer layer is prepared by a spin coating method, a spraying method or a blade coating method, and can also be made into a patterned island-shaped buffer layer by a photoetching-development method, a screen printing method, a film printing method and the like. Then, the circuit and the electronic element are prepared on the buffer layer. Since the island-shaped buffer layer has a higher modulus than the substrate, the stability of the electronic element is maintained when the whole film is deformed.

[0012] In the present application, the material used in the conductive circuit in step (3) can be any one of various conductive metals such as gold, silver, copper and the like; or any one of other conductive materials such as a carbon nanotube, a conductive nanowire, graphene, a polymer conductive material (such as PEDOT) and the like. The preparation method can be a spin coating method, a spraying method, a screen printing method, a film printing method, a photoetching-deposition-stripping process, an etching process and the like.

[0013] In the present application, the functional material film layer in step (4) includes a conductor, a semiconductor and an insulator material, such as any one of graphene, a carbon nanotube, a metal nanowire, a metal nanofilm, an organic conjugated material, an inorganic semiconductor material, a polymer dielectric, an oxide dielectric and the like. The functional material film layer can be prepared by a photoetching-deposition-stripping process, an etching process, a screen printing method, a film printing process, a spin coating method and the like.

[0014] In the present application, the roll film method in step (5) can be divided into two forms: inner roll with circuit on the top of the film and outer roll with circuit on the bottom of the film. The inner roll method can lead the electrode to the two ends of the fiber, and the circuit is completely hidden in the elastic substrate, which maximally protects the stability of the circuit; the outer roll method needs to transfer the elastic film used for inner roll to another low surface energy substrate first, and then perform the roll operation, which can directly expose the electrode to the surface of the fiber, and is convenient for leading out the electrode in the interweaving situation. After the roll film is completed, the film carrying the device is stacked in the form of layer-by-layer winding to form a fiber integrated circuit with a diameter of 50-5000 microns.

[0015] The overall preparation process of the steps and the device structure of the present application are shown in Figure 1 The device cross section is a multi-layer structure.

[0016] The present application has the advantages that: the present application mainly develops a roll film preparation method, introduces micro-nano processing technology of planar devices into fiber electronic devices, and forms a fiber electronic integrated circuit with multi-functionality and high integration. At the same time, through the device structure design (such as adding a high modulus island-shaped structure buffer layer), the stability of the fiber integrated circuit under various deformations is ensured, so that the fiber integrated circuit can play the advantages of flexibility and weavability of the fiber. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 It is a schematic diagram of inner roll and outer roll assembly of fiber integrated circuit.

[0018] Figure 2 It is a schematic diagram of fiber integrated circuit.

[0019] Figure 3 It is a photo of fiber integrated circuit.

[0020] Figure 4 It is a performance test data diagram of fiber internal functional circuit NAND gate, NOR gate and OR gate. DETAILED DESCRIPTION

[0021] The present application will be further understood in combination with the specific implementation cases, but the specific details of the implementation cases are only used to illustrate the present application, and do not represent all the technical solutions under the concept of the present application, so they should not be understood as a limitation on the overall technical solution of the present application. Some non-essential additions and modifications that do not deviate from the concept of the present application, such as simple replacement or substitution of technical features with the same or similar technical effects, all belong to the protection scope of the present application.

[0022] Example 1: A flexible fiber integrated circuit preparation method

[0023] Step 1: Preparation of rollable polymer elastomer substrate film

[0024] Select the substrate with low adhesion to silicone rubber PDMS-601, such as FOTs treated silicon wafer, PET sheet, etc. to spin-coat the silicone rubber PDMS-601 on the substrate at a speed of 5000 rpm for 150 seconds. Put the substrate with uncured PDMS layer into an 80℃ oven for 10 minutes. A 10 micron thick polymer elastomer substrate film can be obtained.

[0025] Step 2: Preparation of high modulus polymer buffer layer

[0026] First, configure the high molecular negative photoresist, which is composed of 7% mass fraction of polyvinyl alcohol aqueous solution and 0.35% mass fraction of diazonium photosensitizer. After hydrophilic oxygen treatment of the elastomer substrate film at a power of 150w for 1.5min, spin-coat the negative photoresist, with the spin-coating parameters as follows: speed 3000 rpm, time 30s. The film thickness is 5-30 microns. Then put the substrate into a 60℃ oven for 1min to remove excess solvent, and then perform a standard photoetching-developing process, with deionized water at 60℃ as the developing solution. Finally, a patterned high modulus polymer buffer layer is obtained.

[0027] Step 3: Preparation of flexible metal circuit with good conductivity

[0028] Take the silicone elastomer substrate with buffer layer, spin-coat positive photoresist (S1813) on it at a speed of 3000 rpm for 1min, and then perform photoetching of the circuit pattern after pre-baking on a 60℃ constant temperature heating table for 1min, and then develop. Then use vacuum thin film deposition process to deposit conductive metal Cr / Au on the developed photoresist, with thicknesses of 5 / 50 nanometers respectively. After the completion of metal thin film deposition, immerse the device in acetone to remove the excess photoresist and metal. Leave the patterned metal conductive path.

[0029] Step 4: Preparation of high-precision electronic components

[0030] Here, the preparation method of transistor devices is taken as an example to demonstrate the preparation of high-precision electronic components.

[0031] First, take the semi-finished device which has already been patterned with metal vias, and perform a photo-etching-deposition-peeling process to prepare the source-drain electrodes of the transistor, which includes the following steps: (1) spin-coat positive photoresist (S1813) at 3000 rpm for 1 min, pre-bake at 60°C for 1 min, then perform photo-etching of the source-drain electrodes of the transistor, and develop. The channel length of the transistor can be 2-20 nm. (2) use vacuum thin film deposition process to deposit conductive metal Cr / Au on the developed photoresist, with thickness of 5 / 50 nm respectively. (3) after the completion of metal thin film deposition, immerse the device in acetone to remove the excess photoresist and metal, leaving the metal source-drain electrodes with channels.

[0032] Subsequently, spin-coat organic polymer semiconductor material solution (P3HT) on the device at 3000 rpm for 30 seconds, and dry the solvent in a 60°C oven for 1 min. The organic polymer semiconductor material solution is prepared by dissolving 5 mg of P3HT material and 5 mg of SEBS in 1 ml of toluene. Then use thin film printing process to print the dielectric gel layer solution on the transistor channel, and after ensuring that the printed area completely covers the channel and the electrodes, place it in a 60°C oven for 1 min to dry the solvent. The dielectric gel layer solution is prepared by mixing PVDF-HFP, EMI-TFSI, and ethyl acetate in a ratio of 1:4:20.

[0033] Finally, perform the above-mentioned photo-etching-deposition-peeling process again on the device to prepare the top electrode gate. Thus the preparation of the transistor is completed.

[0034] Step 5: Assembly and preparation of the device

[0035] Place the prepared elastomer substrate and device upwards / downwards on a substrate with low adhesion to thin films, then use a film pushing piece to push the elastomer film up and curl from one side, and the way of curling the device upwards to form fibers is called inside-out, and the way of curling the device downwards to form fibers is called outside-out (as shown in Figure 1 ). The outside-out way can directly expose the electrode to the surface of the fiber, thus improving the efficiency of connecting the external circuit.

[0036] As Figure 2 , the flexible integrated circuit is distributed in each layer inside the fiber, greatly improving the utilization rate of fiber space. At the same time, due to the existence of the buffer layer, the resistance of the flexible metal circuit prepared by the above method can remain stable when the fiber is subjected to various dynamic deformations such as bending, stretching, twisting, and pressure, and the resistance change is within 5%. The on-off ratio of the flexible transistor prepared by the above method is 10 5The above, the turn-on voltage is as low as -1.5V, and the turn-on current can reach 10mA, which meets the requirements of modern transistor applications. The size of the transistor can be as small as 30μm*30μm. Therefore, 100000 transistors can be integrated inside a 1cm fiber through the above preparation process, which has practical application potential. The flexible fiber integrated circuit prepared by the above method is shown in FIG. 1, wherein the fiber diameter is only 200μm, and the functional circuits are tightly stacked inside the fiber. At the same time, the internal functional circuits such as NAND gate, NOR gate, and OR gate can work well (as shown in FIG. 2). Figure 3 Figure 4

[0037] Embodiment 2: A flexible fiber integrated circuit preparation method

[0038] Step 1: Preparation of a rollable polymer elastomer substrate film

[0039] A substrate with low adhesion to silicone rubber PDMS-601 is selected, such as a silicon wafer treated by FOTs and a PET sheet, and the silicone rubber PDMS-601 is uniformly spin-coated on the substrate at a speed of 5000rpm for 300 seconds. The substrate with the uncured PDMS layer is placed in an 80℃ oven for curing for 10 minutes. A 5-micron-thick rollable polymer elastomer substrate film is obtained.

[0040] Step 2: Preparation of a high-modulus polymer buffer layer

[0041] First, a polymer negative photoresist is configured, which is configured from 7% by mass fraction of polyvinyl alcohol aqueous solution and 0.35% by mass fraction of potassium dichromate photosensitizer. After the elastomer substrate film is subjected to hydrophilic oxygen treatment at a power of 50w for 2 minutes, the negative photoresist is spin-coated, and the spin-coating parameters are as follows: speed 3000rpm, time 30s. The film thickness is 5-30 microns. Then, the substrate is placed in a 60℃ oven for baking for 1 minute, and after removing the excess solvent, a standard photoetching-development process is performed, and the developing solution is 60℃ deionized water. Finally, a patterned high-modulus polymer buffer layer is obtained.

[0042] Step 3: Preparation of a flexible polymer circuit with good conductivity

[0043] First, a conductive polymer solution is configured: 13% by mass fraction of isopropyl alcohol is mixed with PEDOT:PSS solution (PH1000), and stirred in a constant-temperature water bath at 40℃ for 1h.

[0044] ​​Take the silicon rubber substrate with a buffer layer, after the elastomer substrate film is treated with hydrophilic oxygen at a power of 50w for 2min, cover a mask plate with circuit gap on it. Spray the prepared PEDOT conductive polymer solution on the mask plate by spray gun, after the solution is dried, remove the mask plate, leave the patterned polymer conductive path.

[0045] Step 4: preparation of high-precision electronic components

[0046] Here, the preparation method of transistor devices is taken as an example to show the preparation of high-precision electronic components.

[0047] First, take the semi-finished device with patterned polymer path, and perform a spray process to prepare the source and drain electrodes of the transistor, which includes the following steps: (1) configure the conductive polymer solution: mix 13% mass fraction of isopropyl alcohol with PEDOT: PSS solution (PH1000), and stir in a constant temperature water bath at 40 degrees Celsius for 1h. (2) take the silicon rubber substrate with a buffer layer, after the elastomer substrate film is treated with hydrophilic oxygen at a power of 50w for 2min, cover a mask plate with circuit gap on it. Spray the prepared PEDOT conductive polymer solution on the mask plate by spray gun, after the solution is dried, remove the mask plate, leave the patterned polymer conductive path.

[0048] Subsequently, the patterned organic polymer semiconductor material solution (P3HT) is printed in the device channel by thin film printing, and the solvent is dried in a 60℃ oven for 1min. The organic polymer semiconductor material solution is prepared by dissolving 7mg P3HT material and 3mg SEBS in 1ml toluene, and 1% mass fraction of terpineol is added to adjust the volatility of the solution for printing. Then the dielectric gel layer solution is printed on the transistor channel using the thin film printing process, and after ensuring that the printed area completely covers the channel and the electrode, it is placed in a 60℃ oven for 1min to dry the solvent. The dielectric gel layer solution is prepared by mixing PVDF-HFP, EMI-TFSI and ethyl acetate in a ratio of 1:4:20.

[0049] Finally, the device is subjected to the above-mentioned spray PEDOT: PSS solution process again to prepare the top electrode gate. Thus the preparation of the transistor is completed.

[0050] Step 5: assembly and preparation of the device

[0051] Place the prepared elastomer substrate and device upwards on a substrate with low thin film adhesion, then use a film pushing piece to push the elastomer film from one side and curl it to form an inner curled fiber. The inner curled fiber electrode is led out from both ends of the fiber.

[0052] The fiber integrated circuit prepared by the method has electrodes of conductive polymer materials, and thus the fiber as a whole has better flexibility. The fiber can stably work under a larger deformation (30%).

Claims

1. A method of fabricating a flexible fiber integrated circuit, comprising: The specific steps are as follows: (1) preparing a rollable polymer substrate; the polymer substrate is composed of a low surface energy substrate and an elastomer film; the low surface energy substrate is a smooth plane modified by fluorine groups or alkane chains; the elastomer film is any one of silicone rubber, polyurethane, styrene-butadiene-styrene block copolymer (SBS) or hydrogenated styrene-butadiene block copolymer (SEBS); the thickness of the elastomer film is 1-50 microns; (2) preparing a high modulus polymer buffer layer; the polymer buffer layer uses high modulus polymer materials, specifically any one of polyvinyl alcohol, polyimide, polystyrene, polyethylene terephthalate, polyethylene or polypropylene; the high modulus polymer material can completely cover the surface of the polymer substrate, the polymer buffer layer adopts a patterned island structure, and the thickness of the polymer buffer layer is 50 nanometers-5 microns; (3) preparing a conductive path with good conductivity; (4) preparing a functional material film layer to realize the function of electronic devices; (5) using a roll film method, the polymer substrate obtained in step (1), the polymer buffer layer obtained in step (2), the conductive path obtained in step (3) and the functional material film layer obtained in step (4) are prepared to obtain a multilayer flexible fiber integrated circuit; the roll film method can be divided into outer roll film and inner roll film according to the position of the device; during the roll film process, the elastomer film is separated from the low surface energy substrate, and the films are attached to each other to form a stable fiber structure; after the roll film is completed, the film carrying the device becomes a fiber integrated circuit with a diameter of 50-5000 microns in the form of layer-by-layer winding stack.

2. The production method according to claim 1, characterized by, The material used in the conductive path with good conductivity in step (3) is various conductive metals or other conductive materials; the various conductive metals are specifically any one of gold, silver or copper; the other conductive materials are specifically any one of carbon nanotubes, conductive nanowires, graphene or high molecular conductive materials.

3. The preparation method according to claim 1, characterized in that, The functional material film layer in step (4) is any one of conductor, semiconductor or insulator material, which can be prepared by photolithography-deposition-stripping process, etching process, screen printing, thin film printing process or spin coating process.

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