Stretchable wire comprising liquid metal particles and method of making the same

Abstract

The present invention relates to a stretchable composite material comprising a stretchable substrate; and liquid metal particles formed within the stretchable substrate.

Description

Technical Field

[0001] This invention relates to a stretchable wire containing liquid metal particles and a method for preparing the same. Background Technology

[0002] Stretchable wires are crucial for manufacturing stretchable mechanical devices such as wearable electronics, soft robots, prosthetics, and electronic skin. Typically, methods for fabricating stretchable wires include forming a corrugated metal wire structure on a stretchable substrate to prevent breakage during stretching; and incorporating conductive materials into stretchable polymers. Furthermore, to integrate these wires into the semiconductor components necessary for electronic devices, they must be produced using current semiconductor manufacturing photolithography processes, achieving high resolution and large-area fabrication capabilities in addition to electrical properties.

[0003] However, when metal wires are made into a wavy shape, it is difficult to achieve high integration of the wires due to geometric limitations, and the degree of stretching is also limited by the inherent mechanical properties of the metal itself. In addition, when stretchable polymers are mixed with conductive materials to prepare stretchable wires, although high stretch ratios can be achieved, the problem is that the conductivity is lower than that of metal materials, and it is difficult to process them using photolithography technology.

[0004] Currently, in order to achieve high conductivity at the metal level and high elongation of stretchable polymer composites, research is being actively conducted on methods for preparing high-resolution, high-elongation, and high-conductivity wires. These methods utilize liquid metal particles as conductive materials and polymer composites prepared using polymers, and further pattern the wires using photolithography.

[0005] The above-mentioned background technology was acquired or learned by the inventors during the development of this invention, and should not be construed as necessarily being a generally known technology disclosed before the application for this invention. Summary of the Invention

[0006] Technical problems to be solved To ensure both high electrical conductivity at the metallic level and high elongation of the stretchable polymer composite, liquid metal particles can be used as conductive materials and combined with polymers to prepare polymer composites. Taking gallium-indium alloy as a representative liquid metal as an example, because it is liquid at room temperature, it can be stretched without restriction and possesses high electrical conductivity at the metallic level (3.4 × 10⁻⁶). 6 S / m).

[0007] However, the drawbacks of this liquid metal include its high surface tension, making it difficult to pattern and prone to contamination. Furthermore, the surface of granular liquid metal has an insulating oxide film, which hinders the flow of current even when particles are in contact.

[0008] To address the aforementioned problems, this invention aims to provide a high-resolution, high-conductivity, and high-strength conductive substrate and its fabrication method.

[0009] However, the technical problem to be solved by the present invention is not limited to the issues mentioned above, and other issues not mentioned will be clearly understood by those skilled in the art through the following description.

[0010] Technical methods for solving problems The stretchable composite material of the present invention may include: a stretchable substrate; and liquid metal particles formed within the stretchable substrate.

[0011] According to one embodiment, in the stretchable composite material, the liquid metal particles are 50% to 95% by weight.

[0012] According to one embodiment, the liquid metal particles comprise at least one selected from the group consisting of gallium-indium alloys, gallium, gallium-indium-tin alloys, gallium-indium-silver alloys, and gallium-indium-copper alloys.

[0013] The stretchable conductor substrate of the present invention may include: a stretchable substrate; and a conductor formed on the stretchable substrate and comprising the stretchable composite material described in the present invention.

[0014] According to one embodiment, the stretchable substrate comprises at least one selected from the group consisting of polydimethylsiloxane (PDMS), Ecoflex, Dragon Skin, and styrene-butadiene copolymer (SEBS).

[0015] According to one embodiment, the ratio of the thickness of the conductor to the diameter of the liquid metal particle is from 1:0.01 to 1:1.

[0016] According to one embodiment, the conductivity of the wire is 10. 5 S / m to 10 6 S / m, tensile strength is 50% to 200%.

[0017] According to one embodiment, the resistance change rate of the conductor is less than 15% when stretched by 50%.

[0018] The method for fabricating a stretchable conductive substrate of the present invention may include the following steps: preparing a substrate on which a carbon thin film is formed; forming and patterning a photoresist on the carbon thin film; forming a stretchable composite material on the patterned photoresist; removing the patterned photoresist to form a pattern of the stretchable composite material; forming a stretchable substrate on the carbon thin film and the stretchable composite material, thereby forming a stretchable conductive substrate containing the pattern of the stretchable composite material; and separating the stretchable conductive substrate from the substrate and removing the carbon thin film from the stretchable conductive substrate.

[0019] According to one embodiment, the step of removing the patterned photoresist to form the pattern of the stretchable composite material further includes the step of irradiating the substrate on which the pattern of the stretchable composite material is formed with microwaves.

[0020] According to one embodiment, the step of removing the carbon film from the stretchable conductive substrate is performed by a plasma etching process.

[0021] According to one embodiment, the steps of preparing a substrate with a carbon thin film, forming a stretchable composite material on the patterned photoresist, or forming a stretchable substrate on the carbon thin film and the stretchable composite material, thereby forming a stretchable wire substrate containing a pattern of the stretchable composite material, are carried out using at least one of spin coating, spraying, ultrasonic spraying, dip coating, and screen printing.

[0022] According to one embodiment, in the step of removing the patterned photoresist to form the pattern of the stretchable composite material, the spacing of the pattern of the stretchable composite material is from 10 μm to 1000 μm.

[0023] According to one embodiment, in the step of preparing a substrate with a carbon thin film, the carbon thin film comprises at least one selected from the group consisting of polyethyleneimine (PEI), polyacrylic acid (PAA), and polyvinylpyrrolidone (PVP), and has a thickness of 5 nm to 50 nm, formed at a temperature of 300°C to 350°C.

[0024] Invention Effects The present invention can provide a stretchable conductor substrate comprising a stretchable composite material and a method for preparing the same.

[0025] The stretchable conductive substrate comprising a stretchable composite material according to the present invention achieves high conductivity using liquid metal particles and also possesses high stretchability, capable of being stretched by more than 100%, and even when stretched by 50%, it achieves a resistance change of less than 15%. Furthermore, by employing existing photolithography processes, high resolution at the 10μm level can be achieved, enabling large-area patterning at the wafer size. Attached Figure Description

[0026] Figure 1 These are schematic diagrams and actual images of a stretchable wire substrate before and after carbon film removal, according to an embodiment of the present invention.

[0027] Figure 2 This is a schematic diagram of a method for preparing a stretchable conductive substrate according to an embodiment of the present invention.

[0028] Figure 3 This is a schematic diagram and SEM image of a method for forming a stretchable composite material pattern on a carbon thin film on a substrate according to an embodiment of the present invention.

[0029] Figure 4 This is a graph showing the rate of change of resistance of a 10 μm wire when stretched by 50% according to an embodiment of the present invention. Detailed Implementation

[0030] The embodiments will now be described in detail with reference to the accompanying drawings. However, various modifications can be made to the embodiments, and the scope of this disclosure is not limited to these embodiments. It should be understood that all modifications to the embodiments, their equivalents, and even their substitutions are included within the scope of this invention.

[0031] The terminology used in the embodiments is for illustrative purposes only and is not intended to limit the scope. Unless the context clearly indicates that they have different meanings, the singular form encompasses the plural form. In this specification, terms such as "comprising" or "having" are used to express the presence of the features, numbers, steps, operations, constituent elements, accessories, or combinations thereof described in the specification, and do not exclude the possibility of the presence or additional inclusion of one or more other features, numbers, steps, operations, constituent elements, accessories, or combinations thereof.

[0032] Unless otherwise defined, all terms, including technical or scientific terms used herein, shall have the ordinary meaning as understood by one of ordinary skill in the art to which the examples pertain. Terms commonly used, such as those defined in dictionaries, shall be understood as having the meaning in the relevant technical context and, unless explicitly defined in this specification, shall not be interpreted as having an idealized or overly formal meaning.

[0033] The embodiments disclosed in this specification are described in detail with reference to the accompanying drawings. Identical or similar components are assigned the same reference numerals, regardless of the reference numerals, and repeated descriptions are omitted. Furthermore, in describing the embodiments disclosed in this specification, detailed descriptions of relevant prior art will be omitted if it is determined that such detailed descriptions may obscure the spirit of the embodiments disclosed in this specification.

[0034] Furthermore, when describing the constituent elements of an embodiment, terms such as first, second, A, B, (a), and (b) may be used to describe the constituent elements of the embodiment. The use of these terms is solely for the purpose of distinguishing one constituent element from others, but the nature, order, etc., of the constituent elements are not limited by the terms. When referring to a constituent element being "connected" or "coupled" to another constituent element, it should be understood that it can be directly connected or directly coupled to the other constituent element, but other constituent elements may also exist between them.

[0035] When a constituent element has a common function with a constituent element of any embodiment, the same name is used in descriptions in other embodiments. Unless otherwise stated, the description disclosed in one example embodiment is applicable to other embodiments, and its detailed description will be omitted.

[0036] The stretchable wire containing liquid metal particles and its preparation method according to the present invention will now be described in detail with reference to the embodiments and accompanying drawings. However, the present invention is not limited to these embodiments and drawings.

[0037] The stretchable composite material of the present invention includes: a stretchable substrate; and liquid metal particles formed within the stretchable substrate.

[0038] According to one embodiment, the stretchable composite material of the present invention uses a stretchable substrate; and liquid metal particles formed in the stretchable substrate as a conductive material, thereby producing a stretchable composite material that ensures high elongation and high conductivity at the metal level.

[0039] According to one embodiment, when a typical liquid metal gallium-indium alloy is used as the liquid metal particles, it can be stretched without restriction because it is liquid at room temperature and has high electrical conductivity at the metal level (3.4 × 10⁻⁶). 6 However, its disadvantages include high surface tension, making it difficult to pattern and prone to contamination. To solve these problems, an ultrasonic pulverizer can be used to disperse liquid metal in particle form into a solution containing a stretchable substrate to produce a stretchable composite ink, thereby creating the stretchable composite material of this invention.

[0040] According to one embodiment, in the stretchable composite material, the liquid metal particles are 50% to 95% by weight.

[0041] According to one embodiment, in the stretchable composite material, the liquid metal particles are 50% to 95% by weight; 60% to 95% by weight; 65% to 95% by weight; 70% to 95% by weight; 75% to 95% by weight; 80% to 95% by weight; 85% to 95% by weight; 50% to 90% by weight; 50% to 80% by weight; 50% to 70% by weight; 50% to 60% by weight.

[0042] According to one embodiment, in the stretchable composite material, if the content of the liquid metal particles is less than 50% by weight, a liquid metal particle film may not be formed due to insufficient liquid metal particles; if the content exceeds 95% by weight, a uniform liquid metal particle film may be difficult to form due to low polymer content.

[0043] According to one embodiment, the liquid metal particles may comprise at least one selected from the group consisting of gallium-indium alloys, gallium, gallium-indium-tin alloys, gallium-indium-silver alloys, and gallium-indium-copper alloys.

[0044] According to one embodiment, gallium (Ga) is a rare post-transition metal that is soft, silvery in color, and has a melting point of 29.8°C, remaining liquid even at room temperature. Furthermore, due to its high stretchability and low resistivity, gallium-based liquid metals are easily applied to stretchable composite materials. However, gallium has an electronegativity of 1.8, similar to that of aluminum (1.6), another easily oxidized metal, and its ionization energy is 570 kJ / mol, making it a metal prone to oxidation. If gallium forms an alloy with a base metal lacking oxidation resistance, an oxide film easily forms on the alloy surface. If an insulating oxide film exists on the alloy surface, current may be unable to flow even when liquid metal particles are in contact.

[0045] According to one embodiment, when an antioxidant metal is added to the gallium to form an alloy, the alloy formed by the gallium and the antioxidant metal also possesses antioxidant properties due to the presence of the antioxidant metal, which can reduce or inhibit the formation of a surface oxide film. The stretchable composite material according to an embodiment of the present invention does not lose conductivity and has both reliability and economic benefits.

[0046] The stretchable conductor substrate of the present invention includes: a stretchable substrate; and a conductor formed on the stretchable substrate and comprising the stretchable composite material of the present invention.

[0047] Figure 1These are schematic diagrams and actual images of a stretchable wire substrate before and after carbon film removal, according to an embodiment of the present invention.

[0048] See Figure 1 Before the carbon film is removed, the stretchable wire substrate 100 includes a carbon film 110, a stretchable composite material 120, and a stretchable substrate 130.

[0049] According to one embodiment, the carbon film 110 can be removed by an oxygen plasma etching process.

[0050] In addition, see Figure 1 The stretchable wire substrate 150 after removing the carbon film includes a stretchable composite material 120 and a stretchable substrate 130. The stretchable wire substrate 150 includes a stretchable substrate 130; and a wire formed on the stretchable substrate 130 and comprising the stretchable composite material 120.

[0051] According to one embodiment, the stretchable substrate may include at least one selected from the group consisting of polydimethylsiloxane (PDMS), Ecoflex, Dragon Skin, and styrene-butadiene copolymer (SEBS).

[0052] According to one embodiment, the stretchable substrate can be a substrate with stretchability and flexibility, and can be in the form of a thin sheet. Preferably, it can be a polydimethylsiloxane (PDMS) substrate. PDMS is a stretchable polymer material with homogeneous isotropic properties. Optically, it remains transparent even at a thickness of 300 nm and exhibits excellent durability, without degradation of physical properties even after long-term use.

[0053] According to one embodiment, the stretchable substrate, as a flexible substrate, can be made of a bendable or stretchable insulating material. For example, the stretchable substrate can be made of silicone rubber, such as polydimethylsiloxane (PDMS); or of an elastomer, such as polyurethane (PU), thereby possessing flexibility. However, the material of the stretchable substrate is not limited to these.

[0054] According to one embodiment, the stretchable substrate is a flexible substrate whose expansion and contraction are reversible. Furthermore, its elastic modulus can range from several megapascals (MPa) to several hundred megapascals, and its elongation at break can be over 100%. The thickness of the lower substrate can range from 10 micrometers (µm) to 1 millimeter (mm), but is not limited thereto.

[0055] According to one embodiment, the ratio of the wire thickness to the diameter of the liquid metal particle (wire thickness: liquid metal particle diameter) can be from 1:0.01 to 1:1.

[0056] According to one embodiment, the ratio of the wire thickness to the diameter of the liquid metal particle can be 1:0.01 to 1:1; 1:0.05 to 1:1; 1:0.1 to 1:1; 1:0.2 to 1:1; 1:0.3 to 1:1; 1:0.5 to 1:1; 1:0.6 to 1:1; 1:0.7 to 1:1; 1:0.8 to 1:1; 1:0.9 to 1:1; 1:0.01 to 1:0.9; 1:0.01 to 1:0.7; 1:0.01 to 1:0.5; 1:0.01 to 1:0.3; 1:0.01 to 1:0.1; 1: 0.01 to 1 : 0.05.

[0057] According to one embodiment, if the ratio of the wire thickness to the diameter of the liquid metal particle exceeds the specified range, then in the method for preparing the stretchable wire substrate of the present invention, during the step of forming photoresist on the carbon thin film and performing patterning, there may be a problem that the pattern resolution and thickness of the photoresist used for patterning are inappropriate.

[0058] According to one embodiment, the conductivity of the wire is 10. 5 S / m to 10 6 S / m, tensile strength is 50% to 200%.

[0059] According to one embodiment, the conductivity of the wire is 10. 5 S / m to 10 6 S / m; 2 10 5 S / m to 10 6 S / m; 3 10 5 S / m to 10 6 S / m; 4 10 5 S / m to 10 6 S / m; 5 10 5S / m to 10 6 S / m; 6 10 5 S / m to 10 6 S / m; 7 10 5 S / m to 10 6 S / m; 8 10 5 S / m to 10 6 S / m; 9 10 5 S / m to 10 6 S / m; 10 5 S / m to 0.9 10 6 S / m; 10 5 S / m to 0.7 10 6 S / m; 10 5 S / m to 0.5 10 6 S / m; 10 5 S / m to 0.3 10 6 S / m; 10 5 S / m to 0.2 10 6 S / m.

[0060] According to one embodiment, the tensile strength of the conductor is 50% to 200%; 50% to 180%; 50% to 150%; 50% to 120%; 50% to 100%; 50% to 80%; 70% to 200%; 90% to 200%; 100% to 200%; 120% to 200%; 150% to 200%; 170% to 200%.

[0061] According to one embodiment, if the conductivity of the wire is less than 10... 5 If the conductivity is less than S / m, the current cannot flow due to insufficient conductivity, or it will be difficult to use in photolithography. If the stretchability is less than 50%, the wire cannot be highly integrated. Furthermore, if the conductivity and stretchability of the wire exceed the above ranges, it may not be possible to pattern the wire through photolithography, thus making it impossible to produce high-resolution, high-stretchability, and high-conductivity wires.

[0062] According to one embodiment, when the conductor is stretched by 50%, its resistance change rate can be less than 15%.

[0063] Figure 4 This is a graph showing the rate of change of resistance of a 10 μm wire when stretched by 50% according to an embodiment of the present invention.

[0064] See Figure 4 It can be confirmed that when the conductor is stretched by 50%, its resistance change rate is less than 15%.

[0065] According to one embodiment, the wire is formed on the stretchable substrate and comprises the stretchable composite material of the present invention, the stretchable composite material may include a stretchable substrate and liquid metal particles formed within the stretchable substrate.

[0066] According to one embodiment, the wire comprises the liquid metal particles, and the method for preparing the stretchable wire substrate of the present invention may include the step of irradiating with microwaves, thereby generating conductivity between the liquid metal particles.

[0067] According to one embodiment, since the liquid metal particles are conductive, the wire can be a highly conductive and highly tensile wire.

[0068] According to one embodiment, the wires can be produced using photolithography to achieve high resolution at the 10 μm level and to enable large-area patterning at the wafer size.

[0069] The method for preparing a stretchable conductive substrate of the present invention may include the following steps: preparing a substrate on which a carbon thin film is formed; forming and patterning a photoresist on the carbon thin film; forming a stretchable composite material on the patterned photoresist; removing the patterned photoresist to form a pattern of the stretchable composite material; forming a stretchable substrate on the carbon thin film and the stretchable composite material to form a stretchable conductive substrate including the pattern of the stretchable composite material; and separating the stretchable conductive substrate from the substrate and removing the carbon thin film from the stretchable conductive substrate.

[0070] Figure 2 This is a schematic diagram of a method for preparing a stretchable conductive substrate according to an embodiment of the present invention.

[0071] See Figure 2 The first step is to prepare a substrate 230 with a carbon thin film 220 and spin-coat photoresist 210 onto the carbon thin film 220.

[0072] Figure 2 The second step shown is the patterning of the photoresist 210. According to one embodiment, the photoresist 210 may be AZ 2070 or AZ 4330, but is not limited thereto.

[0073] Figure 2 The third step shown is to spin-coat the stretchable composite material 240 onto the patterned photoresist 210.

[0074] Figure 2The fourth step shown is to remove the patterned photoresist 210 to form the pattern of the stretchable composite material 240.

[0075] After completion Figure 2 After the fourth step shown, microwaves can be irradiated onto the patterned stretchable composite material 240 to make it conductive.

[0076] Figure 2 The fifth step shown is to spin-coat the stretchable substrate 250 onto the carbon film 220 and the patterned stretchable composite material 240, thereby forming a stretchable wire substrate including the pattern of the stretchable composite material 240.

[0077] Figure 2 The sixth step shown is to separate the stretchable wire substrate by immersing the substrate 230 in water. The carbon film 220 has weak adhesion to the substrate 230, and by immersing the carbon film 220 in water, it can be separated from the substrate 230. This can be used to transfer a target object from one substrate to another using the carbon film 220.

[0078] According to one embodiment, the method of immersing the carbon film 220, which has a weak adhesion to the substrate 230, in water to separate it from the substrate 230 can be the same method used when transferring a target object that has been heat-treated at a temperature below 300°C from one substrate to another.

[0079] Figure 2 The seventh step shows that the stretchable wire substrate 200 separated from the substrate 230 includes the carbon film 220, the patterned stretchable composite material 240 and the stretchable substrate 250.

[0080] Figure 2 The eighth step illustrates that the stretchable wire substrate 260 after removing the carbon film includes the patterned stretchable composite material 240 and the stretchable substrate 250. The stretchable wire substrate 260 may include the stretchable substrate 250; and wires formed on the stretchable substrate 250 and including the stretchable composite material 240.

[0081] According to one embodiment, the removal of the carbon thin film 220 can be carried out by an oxygen plasma etching process.

[0082] According to one embodiment, the step of removing the patterned photoresist to form the stretchable composite material pattern may include irradiating a substrate on which the stretchable composite material pattern is formed with microwaves.

[0083] According to one embodiment, the method may further include the step of irradiating microwaves onto a substrate on which the stretchable composite material pattern is formed, such that the substrate on which the stretchable composite material pattern is formed can absorb microwaves to raise its temperature, thereby generating conductivity between liquid metal particles formed within the stretchable substrate contained in the stretchable composite material through the heat.

[0084] According to one embodiment, the substrate on which the stretchable composite material pattern is formed is a substrate capable of absorbing microwaves, and the main reason for the conductivity between the liquid metal particles is that the substrate on which the stretchable composite material pattern is formed absorbs microwaves, rather than the liquid metal particles absorbing microwaves.

[0085] According to one embodiment, the step of removing the carbon film from the stretchable conductive substrate can be achieved by a plasma etching process.

[0086] According to one embodiment, the step of removing the carbon film from the stretchable conductive substrate can be performed by a plasma etching process using O2 gas. For example, when removing the carbon film from the stretchable conductive substrate, an O2 plasma etching process can be used, in which O2 gas is introduced at a flow rate of 50 sccm to 100 sccm and a power of 200 W to 250 W is applied for 1 to 3 minutes.

[0087] According to one embodiment, the steps of preparing a substrate with a carbon thin film, forming a stretchable composite material on the patterned photoresist, or forming a stretchable substrate on the carbon thin film and the stretchable composite material to form a stretchable wire substrate containing the pattern of the stretchable composite material are carried out using at least one of spin coating, spraying, ultrasonic spraying, dip coating, and screen printing.

[0088] Figure 3 These are schematic diagrams and SEM images of a method for forming a stretchable composite material pattern on a carbon thin film on a substrate according to an embodiment of the present invention.

[0089] Figure 3 The first step shown illustrates a patterning step performed on a carbon thin film 220 formed on a substrate 230 and a photoresist 210 formed on the carbon thin film 220. According to one embodiment, the photoresist 210 may be AZ 2070 or AZ4330, but is not limited thereto. See also Figure 3 The first step of the SEM image shows the patterned photoresist 210.

[0090] Figure 3 The second step illustrates the process of spin-coating the stretchable composite material 240 onto the patterned photoresist 210. See also... Figure 3The SEM image from the second step shows that the pattern of the photoresist 210 becomes blurred due to spin-coating the stretchable composite material 240 onto the patterned photoresist 210.

[0091] Figure 3 The third step illustrates the process of forming the pattern of the stretchable composite material 240 by removing the patterned photoresist 210. See also... Figure 3 The SEM image from the third step shows the patterned stretchable composite material 240.

[0092] According to one embodiment, in the step of removing the patterned photoresist to form the pattern of the stretchable composite material, the spacing of the pattern of the stretchable composite material is from 10 μm to 1000 μm.

[0093] According to one embodiment, in the step of removing the patterned photoresist to form the pattern of the stretchable composite material, the spacing of the pattern of the stretchable composite material is 10 μm to 1000 μm; 10 μm to 900 μm; 10 μm to 800 μm; 10 μm to 700 μm; 10 μm to 500 μm; 10 μm to 400 μm; 10 μm to 300 μm; 10 μm to 200 μm; 10 μm to 100 μm; 50 μm to 1000 μm; 100 μm to 1000 μm; 200 μm to 1000 μm; 300 μm to 1000 μm; 500 μm to 1000 μm; 700 μm to 1000 μm; 900 μm to 1000 μm.

[0094] According to one embodiment, in the step of removing the patterned photoresist to form the pattern of the stretchable composite material, if the spacing of the pattern of the stretchable composite material is less than 10 μm, there may be a problem that the patterned photoresist cannot be removed.

[0095] The pattern may include at least one of the following groups selected from straight lines, curves, grids, meshes, polygons, circles, ellipses, arcs, fans, and combinations thereof, preferably including straight lines.

[0096] According to one embodiment, in the step of preparing a substrate with a carbon thin film, the carbon thin film comprises at least one selected from the group consisting of polyethyleneimine (PEI), polyacrylic acid (PAA), and polyvinylpyrrolidone (PVP), and has a thickness of 5 nm to 50 nm, and is formed at a temperature of 300°C to 350°C.

[0097] According to one embodiment, in the step of preparing a substrate with a carbon thin film, the step of forming the carbon thin film may further include the following steps: spin-coating at least one of the group consisting of polyethyleneimine (PEI), polyacrylic acid (PAA) and polyvinylpyrrolidone (PVP) onto the substrate to form a thin film, and then irradiating it with microwaves.

[0098] According to one embodiment, most polymers undergo carbonization and thermal decomposition at temperatures above 300°C, making them difficult to use for transferring thin films onto substrates that have undergone microwave irradiation heat treatment. However, according to one embodiment of the invention, the carbon thin film is formed at a temperature of 300°C to 350°C and remains stable below 300°C, thus making it suitable for use on substrates that have undergone microwave irradiation heat treatment.

[0099] The present invention will now be described in more detail through examples.

[0100] However, the following embodiments are merely examples of the present invention, and the content of the present invention is not limited to the following embodiments.

[0101] Example SEBS-g-ma was dissolved in toluene as a stretchable matrix, and then 20% by weight of liquid metal (EGaln) was added. The stretchable composite material containing liquid metal particles was then prepared by ultrasonic treatment (20 min).

[0102] To transfer the target material from one substrate to another, a polyacrylic acid (PAA) polymer is first spin-coated (3000 rpm, 30 sec) onto a silicon substrate to form a thin film. Then, the film is microwave-treated at 300°C for 1 minute to convert the polymer film into a carbon film, forming a sacrificial layer. A photoresist (AZ2070 or AZ 4330) is patterned on the silicon substrate with the carbon film. Finally, a stretchable composite material containing ink-like liquid metal particles is spin-coated (2000 rpm, 30 sec) onto the patterned photoresist. The substrate coated with the stretchable composite material is then immersed in acetone to remove the photoresist, thereby patterning the stretchable composite material.

[0103] Conductivity was achieved by irradiating a patterned stretchable composite material with microwaves at 340°C for 1 minute. The conductive stretchable composite material containing liquid metal particles was then spin-coated onto a patterned substrate using PDMS to create a stretchable substrate. The spin-coating height (500 rpm, 30 seconds) was higher than the stretchable composite material pattern, thus fabricating a stretchable conductive substrate containing the stretchable composite material pattern. Subsequently, a silicon substrate was immersed in water to remove the stretchable conductive substrate from the silicon substrate, and a carbon film was removed by O2 plasma treatment (200 W, 3 minutes).

[0104] The embodiments have been described above with reference to the accompanying drawings. Those skilled in the art should understand that various modifications and equivalent embodiments can be made based on these drawings. Suitable results can also be obtained if the described techniques are performed in a different order, and / or if the constituent elements of the described systems, architectures, devices, or circuits are combined in different ways, and / or replaced or substituted by other components or their equivalents.

[0105] Therefore, other embodiments, examples, and equivalents of the claims should be interpreted as being included within the scope of protection of the claims.

Claims

1. A stretchable composite material, characterized in that, include: Stretchable substrate; as well as Liquid metal particles formed within the stretchable substrate.

2. The stretchable composite material according to claim 1, characterized in that, In the stretchable composite material, the liquid metal particles are 50% to 95% by weight.

3. The stretchable composite material according to claim 1, characterized in that, The liquid metal particles comprise at least one selected from the group consisting of gallium-indium alloys, gallium, gallium-indium-tin alloys, gallium-indium-silver alloys, and gallium-indium-copper alloys.

4. A stretchable conductor substrate, characterized in that, include: Stretchable substrate; and A wire formed on the stretchable substrate and comprising the stretchable composite material as claimed in claim 1.

5. The stretchable conductor substrate according to claim 4, characterized in that, The stretchable substrate comprises at least one selected from the group consisting of polydimethylsiloxane (PDMS), Ecoflex, Dragon Skin, and styrene-butadiene copolymer (SEBS).

6. The stretchable conductor substrate according to claim 4, characterized in that, The ratio of the thickness of the conductor to the diameter of the liquid metal particle is from 1:0.01 to 1:

1.

7. The stretchable conductor substrate according to claim 4, characterized in that, The conductivity of the wire is 10. 5 S / m to 10 6 S / m, Tensile strength ranges from 50% to 200%.

8. The stretchable conductor substrate according to claim 4, characterized in that, When the conductor is stretched by 50%, the resistance change rate is less than 15%.

9. A method for preparing a stretchable conductive substrate, characterized in that, Includes the following steps: Preparing a substrate with a carbon thin film; Photoresist is formed and patterned on the carbon film; A stretchable composite material is formed on the patterned photoresist; The patterned photoresist is removed to form the pattern of the stretchable composite material; A stretchable substrate is formed on the carbon film and the stretchable composite material, thereby forming a stretchable wire substrate incorporating a pattern of the stretchable composite material; and The stretchable wire substrate is separated from the substrate, and the carbon film is removed from the stretchable wire substrate.

10. The method for preparing a stretchable conductive substrate according to claim 9, characterized in that, The step of removing the patterned photoresist to form the pattern of the stretchable composite material further includes the following steps: A substrate on which the pattern of the stretchable composite material is formed by microwave irradiation.

11. The method for preparing a stretchable conductive substrate according to claim 9, characterized in that, The step of removing the carbon film from the stretchable conductive substrate is performed by a plasma etching process.

12. The method for preparing a stretchable conductive substrate according to claim 9, characterized in that, The steps of preparing a substrate with a carbon thin film, forming a stretchable composite material on the patterned photoresist, or forming a stretchable substrate on the carbon thin film and the stretchable composite material, thereby forming a stretchable wire substrate containing a pattern of the stretchable composite material, are carried out using at least one of spin coating, spraying, ultrasonic spraying, dip coating, and screen printing.

13. The method for preparing a stretchable conductive substrate according to claim 9, characterized in that, In the step of removing the patterned photoresist to form the pattern of the stretchable composite material, The spacing of the patterns in the stretchable composite material is from 10 μm to 1000 μm.

14. The method for preparing a stretchable conductive substrate according to claim 9, characterized in that, In the step of preparing a substrate with a carbon thin film, The carbon film comprises at least one selected from the group consisting of polyethyleneimine (PEI), polyacrylic acid (PAA), and polyvinylpyrrolidone (PVP). The thickness is formed to be 5 nm to 50 nm. It is formed at a temperature of 300℃ to 350℃.

Images