Flexible transparent polyimide electrode with self-healing and superhydrophobic properties and preparation method thereof

Abstract

The present invention relates to a method for manufacturing a flexible transparent polyimide electrode having self-healing and superhydrophobic properties. The invention provides a method for manufacturing a transparent polyimide electrode that self-heals even when damaged, thereby preventing a decrease in electrode resistance, and possesses superhydrophobic properties to maintain electrode resistance even when in contact with water.

Description

Technology Field

[0001] The present invention relates to a method for manufacturing a flexible transparent polyimide electrode having self-healing and superhydrophobic properties, wherein the electrode self-heals even if damaged so that the electrode resistance does not decrease, and the electrode maintains its resistance even when in contact with water due to its superhydrophobic properties. Background Technology

[0002] Polyimide (PI) is a polymer of imide monomers, generally produced through the polymerization of dianhydride and diamine, or dianhydride and diisocyanate, and is a polymer that refers to all polymers containing repeating units of Chemical Formula 1 below.

[0003] <Chemical Formula 1>

[0004]

[0005] Polyimides possess excellent mechanical strength, chemical resistance, weather resistance, and heat resistance based on the chemical stability of their imide rings. Furthermore, they offer advantages such as ease of synthesis, the ability to form thin films, and the elimination of the need for crosslinking agents for curing. Due to their outstanding electrical properties, they are gaining attention as high-performance polymer materials in fields ranging from microelectronics to optics.

[0007] Over the past decade, various microelectrodes for measuring biosignals have been fabricated and reported, most of which are fabricated using silicon-based Micro Electro Mechanical System (MEMS) technology.

[0008] However, while current silicon microelectrodes possess various advantages such as ease of microfabrication using MEMS technology and biocompatibility, they have the disadvantage of being unable to ensure flexibility due to the material's inherent characteristics of being sharp and brittle, which can cause damage to adjacent organs or tissues when implanted in the body due to body movements. Recently, to overcome this, various microelectrodes utilizing flexible printed circuit boards (FPCBs) are being developed.

[0009] Flexible printed circuit boards are manufactured by exposing an electrode pattern to a flexible copper clad laminate (FCCL) substrate material in an intaglio manner and creating a final substrate through chemical etching. In this flexible copper clad laminate, polyimide, parylene, SU-8, polydimethylsiloxane, etc. are used as the insulating film layer, and gold, copper, etc., which have excellent conductivity are used as the conductive metal layer laminated to the insulating film layer.

[0010] Since these microelectrodes are inserted into the human body or similar structures to measure biological signals and remain attached to the biological surface for extended periods, material flexibility is required as mentioned above; furthermore, stability is particularly critical to ensure that the electrode pattern does not change and stable performance is maintained even during prolonged use. However, microelectrodes manufactured using conventional methods fail to meet the required level of stability, and research in this area is currently ongoing.

[0011] Microelectrode manufacturing methods generally include casting, deposition / plating, and lamination methods. Recently, however, a deposition / plating method is being actively researched in which a conductive seed layer is deposited on a polyimide layer using a physicochemical method and a copper foil is formed using an economical electroplating process. In this case, a gold layer is mainly applied as the conductive seed layer. This manufacturing method improves the stability of the electrode pattern relatively due to the excellent adhesion between the polyimide layer and the gold layer.

[0012] However, in the case of microelectrodes manufactured in this manner, the impedance of the gold layer is too high to be suitable for measuring biosignals of microcurrents. To lower this impedance, a manufacturing method is generally performed in which another metal is electroplated onto the gold layer, which serves as a conductive seed layer, through a separate electroplating process. However, when a separate metal is plated onto the conductive seed layer through such an electroplating process, the adhesion of this metal plating layer weakens in environments exposed to biological tissue fluid. Consequently, the plating layer easily peels off or is damaged over time, leading to phenomena such as distortion or interruption of biosignals, which resulted in the inability to accurately measure biosignals.

[0013] Polyimide, a synthetic polymer material containing imide bonds that has recently been widely applied in many industrial fields such as liquid crystal alignment films for displays, batteries, and aerospace, exhibits good wear resistance, strength, and chemical resistance. In particular, it possesses significantly superior heat resistance compared to other plastic materials; however, its distinctive yellow color limits its use as a substrate for transparent electrodes. Therefore, to apply polyimide to transparent electrodes, various methods are being employed to develop colorless, transparent polyimide by limiting the charge transfer complex theory, which is the cause of the yellow color.

[0014] The above-mentioned metal-based transparent electrode material can be applied as a flexible transparent electrode by directly coating it onto a colorless transparent polyimide substrate or by coating it onto another host substrate and then transferring it onto the colorless transparent polyimide substrate. However, when transparent electrodes manufactured by this method are actually applied to devices, there is a disadvantage in that electrical conductivity is significantly reduced due to oxidation caused by reactions with oxygen and moisture when exposed to high-temperature and high-humidity environments during subsequent manufacturing processes or to the surrounding atmosphere, as nanomaterials have a large specific surface area. Additionally, due to weak adhesion to the substrate, the electrode may easily detach from the colorless transparent polyimide substrate due to external mechanical stimuli. Therefore, there is a need to protect the above-mentioned transparent electrode material from external environments or mechanical stimuli by embedding it inside the colorless transparent polyimide substrate, rather than simply coating or transferring it onto the substrate.

[0016] Accordingly, the inventors of the present invention confirmed that oligoimide-liquid metal nanocapsules and silver nanowires exist on the surface of a transparent polyimide film so that electricity flows and it can be used as an electrode, and by creating nanoprotrusions, it exhibits superhydrophobicity so that there is no change in electrical resistance even when in contact with water, and even if the electrode surface is damaged, liquid metal flows out to regenerate the surface electrical network so that the resistance does not drop, and thus completed the present invention. Prior art literature

[0018] Republic of Korea Registered Patent No. 10-1308024 Republic of Korea Registered Patent No. 10-1117441 Republic of Korea Registered Patent No. 10-1829174 The problem to be solved

[0019] The present invention aims to provide a flexible transparent polyimide electrode having self-healing and superhydrophobic properties, in which oligoimide-liquid metal nanocapsules and silver nanowires exist on the surface of a transparent polyimide film so that electricity can flow and it can be used as an electrode, and by creating nanoprotrusions, it exhibits superhydrophobicity so that there is no change in electrical resistance even when in contact with water, and even if the electrode surface is damaged, liquid metal flows out to regenerate the surface electrical network so that the resistance does not drop, and a method for manufacturing the same. means of solving the problem

[0020] The present invention relates to a method for manufacturing a flexible transparent polyimide electrode having self-healing and superhydrophobic properties, wherein the electrode self-heals even if damaged, so that the electrode resistance does not drop, and possesses superhydrophobic properties to maintain electrode resistance even when in contact with water. Specifically, after manufacturing a transparent polyimide and an oligoimide-liquid metal nanocapsule, the oligoimide-liquid metal capsule and silver nanowires are coated onto a substrate, then a transparent polyimide is coated thereon, and after sintering, the film is peeled off from the substrate. Accordingly, the film is manufactured as an oligoimide-liquid metal nanocapsule layer, a silver nanowire layer, and a transparent polyimide film layer, and the electrode exhibits superhydrophobic properties due to the nanoprotrusions of the oligoimide-liquid metal nanocapsule, and the electrode resistance does not drop even if damaged, as liquid metal flows out. Effects of the invention

[0021] The present invention has the technical effect of providing a flexible transparent polyimide electrode having self-healing and superhydrophobic properties, and a method for manufacturing the same, wherein oligoimide-liquid metal nanocapsules and silver nanowires exist on the surface of a transparent polyimide film so that electricity can flow and it can be used as an electrode, and by creating nanoprotrusions, it exhibits superhydrophobicity so that there is no change in electrical resistance even when in contact with water, and even if the electrode surface is damaged, liquid metal flows out to regenerate the surface electrical network so that the resistance does not drop. Brief explanation of the drawing

[0022] FIG. 1 illustrates a method for manufacturing a flexible transparent polyimide electrode having self-healing and superhydrophobic properties according to the present invention. Specific details for implementing the invention

[0023] The present invention will be explained in more detail below through examples and / or experimental examples. However, this is intended to aid in understanding the invention and is not intended to limit the scope of the invention.

[0024] Example 1

[0025] 1. Preparation of Oligoimide-Liquid Metal Nanocapsules

[0026] 50 ml of water and ethanol in a 7:3 volume ratio and 0.914 g (0.002 mol) of 6FDA were added to a 250-mL 3-neck round-bottom flask replaced with nitrogen gas, and dicarboxylic acid was carried out by stirring at 70 ℃ for 6 hours.

[0027] 0.5 g of liquid gallium and 0.659 g (0.002 mol) of TFMB were added to the above reaction mixture and ultrasonically dispersed for 1 hour to form monomer salt-liquid metal capsules. The above solution was centrifuged at 3,000 rpm to purify and heated to 200 ℃ to prepare oligoimide-liquid metal nanocapsules.

[0028] 2. Preparation of transparent polyimide solution

[0029] 160 g of dimethylacetamide (DMAc) was added to a 500-mL three-necked cylinder flask purged with nitrogen gas, and 17.44 g (0.054 mol) of 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (2,2'-TFDB) was added and stirred for 1 hour to dissolve. Then, 3.2 g (0.011 mol) of biphenyltetracarboxylic dianhydride (BPDA) and 19.36 g (0.044 mol) of 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) were added and reacted at room temperature for 24 hours.

[0030] Pyridine (8.5 g) and acetic anhydride (22 g) were added to the above reaction mixture and stirred for 6 hours. Then, pure polyimide powder was obtained by precipitating in 10 L of methanol and drying. Afterward, the powder was dissolved in dimethylacetamide at 14 wt% to prepare a transparent polyimide solution.

[0031] 3. Fabrication of Flexible Transparent Polyimide Electrodes with Self-Healing and Superhydrophobic Properties

[0032] The oligoimide-liquid metal capsules and silver nanowires prepared above were dispersed in 50 ml of ethanol, and then coated onto a glass substrate using a spray coater at a speed of 100 mm / s for 10 seconds. After bar-coating the solution prepared in step 1 onto the coated glass substrate, the solution was heated to 80°C under vacuum to produce a 20 µm thick film, thereby manufacturing a flexible transparent polyimide electrode having self-healing and superhydrophobic properties.

Claims

Claim 1 delete Claim 2 delete Claim 3 delete Claim 4 (a) a step of preparing an oligoimide-liquid metal capsule by a process comprising a dicarboxylic acid step, a monomer salt-liquid metal capsule formation step, and a heating step; (b) a step of coating the oligoimide-liquid metal capsule and silver nanowires on a substrate; and (c) a step of coating a transparent polyimide solution on the coated substrate prepared in step (b) and then peeling it off, a method for preparing a polyimide electrode composition. Claim 5 delete Claim 6 A method for preparing a polyimide electrode composition, wherein the monomer-liquid metal capsule forming step comprises adding liquid gallium and TFMB to a dicarboxylic acid reactant. Claim 7 A method for manufacturing a polyimide electrode composition according to claim 6, wherein 0.5g of the liquid gallium and 0.659g of the TFMB are mixed. Claim 8 A method for manufacturing a polyimide electrode composition, wherein, in paragraph 4, the monomer salt-liquid metal capsule forming step is performed by ultrasonic dispersion. Claim 9 A method for preparing a polyimide electrode composition according to claim 8, wherein the ultrasonic dispersion is performed for 1 hour. Claim 10 A method for manufacturing a polyimide electrode composition according to claim 4, wherein the heating is performed by heating to a temperature of 200°C. Claim 11 A method for manufacturing a polyimide electrode composition, wherein, in paragraph 4, the monomer salt-liquid metal capsule forming step further includes a purification step by centrifugation. Claim 12 A method for manufacturing a polyimide electrode composition according to claim 11, wherein the centrifugation is performed at a speed of 3,000 rpm. Claim 13 A method for preparing a polyimide electrode composition according to claim 4, wherein step (b) involves dispersing an oligoimide-liquid metal capsule and a silver nanowire in ethanol and then coating it onto a glass substrate using a spray coater. Claim 14 A method for manufacturing a polyimide electrode composition according to claim 13, wherein the coating is applied at a speed of 100 mm / s for 10 seconds. Claim 15 A method for manufacturing a polyimide electrode composition, characterized in that, in claim 4, it further comprises the step of manufacturing a transparent polyimide solution. Claim 16 A method for preparing a polyimide electrode composition according to claim 15, wherein the preparation of the transparent polyimide solution comprises: (1) mixing and stirring dimethylacetamide (DMAc) and 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (2,2'-TFDB); (2) mixing and reacting biphenyltetracarboxylic dianhydride (BPDA) and (2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride, 6FDA); (3) adding pyridine and acetic anhydride to the reaction mixture and stirring; (4) precipitating to obtain polyimide powder; and (5) dissolving the polyimide powder in a solvent. Claim 17 A method for preparing a polyimide electrode composition according to claim 16, wherein in step (1) above, 160 g of DMAc and 17.44 g of 2,2'-TFDB are mixed. Claim 18 A method for preparing a polyimide electrode composition according to claim 16, wherein 3.2g of BPDA and 19.36g of 6FDA are mixed in step (2) above. Claim 19 A method for preparing a polyimide electrode composition according to claim 16, wherein 8.5 g of pyridine and 22 g of acetic anhydride are added in step (3) above. Claim 20 A method for preparing a polyimide electrode composition, wherein, in the above step (4), the precipitation is precipitated in methanol. Claim 21 A method for preparing a polyimide electrode composition, wherein in step (5) above, the solvent is dimethylacetamide. Claim 22 A method for manufacturing a polyimide electrode composition, wherein, in claim 4, the coating of step (c) is heated under vacuum after bar-coating. Claim 23 A method for manufacturing a polyimide electrode composition according to claim 22, wherein the heating is to heat to 80°C. Claim 24 A polyimide electrode composition manufactured by the manufacturing method of any one of claims 4, 6 to 23. Claim 25 A polyimide electrode comprising the composition of claim 24. Claim 26 In claim 25, the above electrode is a polyimide electrode comprising a film with a thickness of 20 μm. Claim 27 In claim 25, the polyimide electrode is characterized in that, when the electrode surface is damaged, liquid metal flows out to regenerate the surface electrical network so that the resistance does not drop.

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