KR102116281B1 - Stretchable conductor and method of fabricating thereof - Google Patents

Abstract

The present invention relates to a stretchable conductor and a method for manufacturing the stretchable conductor according to an embodiment of the present invention, a composite elastic substrate comprising a first elastic layer and a second elastic layer laminated on the first elastic layer; And an elastic polymer in which a conductive metal is dispersed, and a conductive layer formed on at least a portion of the composite elastic substrate, wherein the second elastic layer has a larger elastic modulus than the first elastic layer.

Description

Stretchable conductor and its manufacturing method {STRETCHABLE CONDUCTOR AND METHOD OF FABRICATING THEREOF}

The present invention relates to a stretchable conductor and a method for manufacturing the same. More specifically, by forming a conductor layer on a substrate comprising an elastic body and a hydrogel (Hydrogel), it relates to a stretchable conductor having improved stretchability and a method for manufacturing the same.

Recently, electronic devices have been developed in the form of wearable devices, soft robotics, and body-attached types using materials having excellent elasticity. The material with excellent elasticity can be manufactured in the form of clothing, and can be well attached to an object having a curved surface, such as a human skin or an organ.

In the study of these flexible electronic devices, the most important part is the conductive layer and the substrate. The conductive layer and the lower substrate should have low elastic modulus, so that the elasticity should be good, and the conductive properties should not change due to deformation. Accordingly, research on flexible electronic devices has been focused on the development of conductive materials.

Most of the substrates used as a conventional stretchable material are silicone rubber, polyethylene naphthalate (PEN), and polyurethane-based polymers. The above materials have elastic modulus values of tens of kPa to Mpa. If a substrate having a low modulus of elasticity is used, it can be used as a stretchable device that is convenient to wear and can be attached to the skin.

On the other hand, research on organic-based conductors to ensure that the conductor layer formed on the substrates also has elasticity has been continued. There has been a development of a stretchable conductor using PEDOT: PSS as a well-known organic material conductive material, but the conductivity still has limitations because it does not reach the metal. Accordingly, research results for manufacturing a conductor by patterning a metal to have a microstructure have also been reported.

Accordingly, an object of the present invention is to provide a stretchable conductor having superior properties than a previously reported conductor, including a composite elastic substrate having a low modulus of elasticity and a stretchable conductor layer.

The present invention also aims to improve the elasticity of the conductor by preventing the dehydration of the substrate when forming the conductor electrode by transferring the conductor layer to the composite elastic substrate using a water-soluble tape.

However, these problems are exemplary, and the scope of the present invention is not limited thereby.

According to an aspect of the present invention for solving the above problems, a composite elastic substrate including a first elastic layer and a second elastic layer laminated on the first elastic layer and an elastic polymer in which conductive metal is dispersed, It includes a conductor layer formed on at least a portion of the composite elastic substrate, the second elastic layer is provided with an elastic conductor having a larger elastic modulus than the first elastic layer.

In addition, according to an embodiment of the present invention, the first elastic layer may include a hydrogel, and the second elastic layer may include silicone rubber.

In addition, according to an embodiment of the present invention, the conductive metal may include any one of silver (Ag), copper (Cu), and gold (Au), and the elastic polymer may include silicone rubber. have.

Further, according to an embodiment of the present invention, the conductive metal is dispersed in a flake form in the elastic polymer, and the content of the conductive metal may be 75 to 85 parts by weight based on 100 parts by weight of the conductive layer .

Further, according to an embodiment of the present invention, the first elastic layer may be about 3 to 50 times thicker than the thickness of the second elastic layer.

Further, according to an embodiment of the present invention, when the length of the composite elastic substrate is increased in one direction, the conductor layer may be lengthened in the one direction while being in contact with the second elastic layer.

Further, according to an embodiment of the present invention, the conductor layer and the second elastic layer may be stretched at the same ratio as the first elastic layer.

In addition, according to an embodiment of the present invention, the composite elastic substrate can be stretched to 1600% to 1800% of the initial length.

And, according to another aspect of the present invention for solving the above problems, (a) preparing a conductive layer ink in which a conductive metal is dispersed in an elastic polymer (b) laminating the first elastic layer and the second elastic layer A method of manufacturing a stretchable conductor is provided, comprising the step of manufacturing a composite elastic substrate and (c) transferring a conductor layer formed of the conductor layer ink to at least a portion on the composite elastic substrate.

In addition, according to an embodiment of the present invention, the step (a), (a1) mixing the prepolymer and the crosslinking agent of the elastic polymer, and stirring it with a solvent to prepare a mixture and (a2) the mixture to the And adding flakes of conductive metal.

In addition, according to an embodiment of the present invention, the elastic polymer comprises a silicone rubber (Silicon rubber), the conductive metal comprises any one of silver (Ag), copper (Cu) and gold (Au), The solvent includes methyl-iso-butyl-ketone (MIBK), with respect to 100 parts by weight of the conductive layer ink, 68.5 parts by weight to 71.5 parts by weight of the flakes of the conductive metal, and the elasticity Polymer 14.5 parts by weight to 16.5 parts by weight, the solvent may include 13.5 parts by weight to 15.5 parts by weight.

In addition, according to an embodiment of the present invention, the step (b), (b1) preparing a first elastomer solution by mixing the first elastomer unit and a crosslinking agent, (b2) the second elastomer unit and a crosslinking agent Applying a mixture to the polymer film and curing it to form a second elastic layer, (b3) applying a binder on the second elastic layer, (b4) on the second elastic layer coated with the binder It may include the step of applying the first elastic solution to the solution and curing it, forming a first elastic layer on the second elastic layer and (b5) removing the polymer film.

In addition, according to an embodiment of the present invention, the first elastic layer may include a hydrogel, and the second elastic layer may include silicone rubber.

In addition, according to an embodiment of the present invention, step (c) comprises: (c1) applying the conductor layer ink to a Teflon film, (c2) heat-treating the applied conductor layer ink and applying the elasticity Curing the polymer to form a conductor layer, (c3) separating the conductor layer from the Teflon film using a water-soluble tape, and (c4) separating the separated conductor layer into a second elastic layer of the composite elastic substrate. It may include the step of transferring to at least a portion of the formed surface, and removing the water-soluble tape.

According to an embodiment of the present invention made as described above, including a composite elastic substrate having a low modulus of elasticity and a conductor layer having elasticity, it is possible to provide a stretchable conductor having superior properties than a previously reported conductor.

In addition, the present invention has an effect of preventing the dehydration of the substrate when the conductor electrode is formed by improving the elasticity of the conductor by transferring the conductor layer to the composite elastic substrate using a water-soluble tape.

Of course, the scope of the present invention is not limited by these effects.

1 is a schematic diagram showing the configuration of a stretchable conductor according to an embodiment of the present invention.
2 is a schematic view showing a cross section of a stretchable conductor.
3 is a schematic diagram showing a method of manufacturing a stretchable conductor according to an embodiment of the present invention.
4 is a flow chart showing a method of manufacturing a stretchable conductor.
5 is a scanning electron microscope (SEM) photograph showing a cross-section of a stretchable conductor according to an embodiment of the present invention.
6 is a scanning electron microscope (SEM) photograph showing a cross section of a conductor layer in which silver (Ag) flakes of a stretchable conductor according to an embodiment of the present invention are dispersed.
7 is a photograph showing the result of measuring the maximum degree of stretch of the stretchable conductor according to an embodiment of the present invention.
8 is a photograph showing stress evaluation results of a conductor substrate according to Comparative Examples and Examples of the present invention and a stress-strain graph.
9 is a photograph showing a result of evaluation of stretchability of a conductor layer formed on a stretchable conductor according to Comparative Examples and Examples of the present invention.
10 is a scanning electron microscope (SEM) photograph showing the surface of a conductor layer according to Comparative Examples and Examples of the present invention.
11 is a graph showing a result of measuring a change in resistance when stretching a stretchable conductor according to Comparative Examples and Examples of the present invention.
12 is a scanning electron microscope (SEM) photograph showing a form in which silver (Ag) flakes are dispersed in a conductor layer according to Comparative Examples and Examples of the present invention.
13 is a photograph showing a wire test for LEDs using a stretchable conductor according to an experimental example of the present invention.
14 is a photograph showing an experiment of a smart patch pressure sensor using a stretchable conductor according to an experimental example of the present invention.

For a detailed description of the present invention, which will be described later, reference is made to the accompanying drawings that illustrate, by way of example, specific embodiments in which the invention may be practiced. These examples are described in detail enough to enable those skilled in the art to practice the present invention. It should be understood that the various embodiments of the present invention are different, but need not be mutually exclusive. For example, certain shapes, structures, and properties described herein may be implemented in other embodiments without departing from the spirit and scope of the invention in relation to one embodiment. In addition, it should be understood that the location or placement of individual components within each disclosed embodiment can be changed without departing from the spirit and scope of the invention. Therefore, the following detailed description is not intended to be taken in a limiting sense, and the scope of the present invention, if appropriately described, is limited only by the appended claims, along with all ranges equivalent to those claimed. In the drawings, similar reference numerals refer to the same or similar functions across various aspects, and length, area, thickness, and the like may be exaggerated for convenience.

In this specification, terms such as “include” or “have” are intended to designate the existence of the described features, numbers, steps, actions, components, parts, or combinations thereof, one or more other features or numbers, It should be understood that the existence or addition possibilities of steps, actions, components, parts or combinations thereof are not excluded in advance.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings in order to enable those skilled in the art to easily implement the present invention.

The present invention relates to a stretchable conductor having excellent elasticity because a conductive layer in which a conductive metal is dispersed is formed on a composite elastic substrate having a low modulus of elasticity.

1 is a schematic view showing the configuration of a stretchable conductor according to an embodiment of the present invention, and FIG. 2 is a schematic view showing a cross section of the stretchable conductor 10.

1 and 2, the stretchable conductor 10 of the present invention is a composite elastic substrate comprising a first elastic layer 110 and a second elastic layer 120 stacked on the first elastic layer 110 ( 100) and an elastic polymer 210 in which the conductive metal 220 is dispersed, and includes a conductor layer 200 formed on at least a portion of the composite elastic substrate 100, and the second elastic layer 120 is The elastic modulus may be greater than that of the first elastic body layer 110.

The stretchable conductor 10 of the present invention may include a composite elastic substrate 100 and a conductor layer 200. The composite elastic substrate 100 has excellent elasticity because it has a low modulus of elasticity. In addition, the conductive layer 200 is formed on at least a portion of the composite elastic substrate 100, and the conductive metal 220 is dispersed to be used as an electrode or an electric wire. In addition, the conductor layer 200 includes the elastic polymer 210 and is excellent in elasticity like the composite elastic substrate 100.

The composite elastic substrate 100 includes a first elastic layer 110 and a second elastic layer 120. It may have excellent elasticity, including layers made of at least two different materials, and improve contact force with the conductive layer 200 formed on the composite elastic substrate 100. It can be understood that the expansion and contraction of the composite elastic substrate 100 includes not only elongation and contraction in one direction, but also being made in various directions, such as bending and bending.

The first elastic body layer 110 may include a material having a lower elastic modulus than the second elastic body layer 120. For example, the first elastic layer 110 may include a hydrogel. Since the first elastic body layer 110 has a low elastic modulus of 0.01 N / mm ² or less, the composite elastic substrate 100 may have excellent elasticity. In addition, when the first elastic layer 110 is formed by including a hydrogel containing moisture therein, the elasticity of the composite elastic substrate 100 can be maximized.

The second elastic layer 120 is stacked on the first elastic layer 110, and may include a material having a larger elastic modulus than the first elastic layer 110. For example, the second elastic layer 120 may include silicone rubber, and more preferably, Ecoflex. A layer in contact with the conductor layer 200 formed on the composite elastic substrate 100, and is stacked on the first elastic layer 110. The second elastic layer 120 may have a very thin film shape than the first elastic layer 110. For example, the first elastic layer 110 may have a thickness of about 0.1 to 1 mm, and the second elastic layer 120 may have a thickness of about 10 to 50 μm. Alternatively, the first elastic layer 110 may be about 3 to 50 times thicker than the thickness of the second elastic layer 120. The second elastic layer 120 has a larger elastic modulus than the first elastic layer 110, but is stacked so as to have a thinner thickness than the first elastic layer 110 and is closely bonded to the first elastic layer 110, The elastic modulus of the second elastic body layer 120 can minimize the effect on the elasticity of the composite elastic substrate 100. That is, by maintaining the elastic modulus of the first elastic body layer 110 and the composite elastic substrate 100 at a similar level, the composite elastic substrate 100 may have excellent elasticity.

In this case, the second elastic body layer 120 may be attached by the first elastic body layer 110 and a binder. When the composite elastic substrate 100 is manufactured, the first elastic body layer 110 and the second elastic body layer 120 are simultaneously attached by attaching the first elastic body layer 110 and the second elastic body layer 120 using a binder. It can be stretched in the longitudinal direction. As an example, the binder may be benzophenone.

Meanwhile, the conductor layer 200 may include the elastic polymer 210 in which the conductive metal 220 is dispersed. The conductive metal 220 included in the conductor layer 200 may provide a conductive path in the stretchable conductor 10. The conductive metal 220 may be electrically connected to each other in a dispersed state within the conductor layer 200 to provide a conductive path. For example, the conductive metal 220 may include silver (Ag), copper (Cu), gold (Au), and the like, and preferably silver (Ag).

At this time, the conductive metal 220 may be dispersed in the form of flakes in the elastic polymer 210. When the conductor layer 200 is stretched in the longitudinal direction along with the composite elastic substrate 100, the conductive metal 220 dispersed in the form of flakes can be electrically connected to each other while being rearranged on the elastic polymer 210. Therefore, it is possible to maintain the conductive path. Therefore, the content of the conductive metal 220 can be adjusted so that the spacing between the conductive metals 220 can be rearranged when the conductor layer 200 is stretched.

Depending on the content of the conductive metal 220, the conductive properties of the conductor layer 200 may change during stretching of the composite elastic substrate 100. When the conductive metal 220 is excessive, the rigidity of the conductor layer 200 may increase due to aggregation of the conductive metal 220, thereby deteriorating elasticity. And, when the conductive metal 220 is in a small amount, when the conductor layer 200 is stretched, the rearrangement effect of the conductive metal 220 that occurs to maintain the conductive path may be reduced. Then, the connection between the conductive metals 220 is not maintained in the process of stretching the conductor layer 200, so that the conductive path is broken, thereby losing the function as an electrode or an electric wire. Therefore, it is necessary to adjust the content of the conductive metal 220 of the conductor layer 200. For example, the content of the conductive metal 220 may be 75 to 85 parts by weight compared to 100 parts by weight of the conductor layer 200, and more preferably 80 parts by weight.

The conductor layer 200 may be stretched and including the elastic polymer 210. When formed on the composite elastic substrate 100 including only the conductive metal 220, when the composite elastic substrate 100 is stretched in the longitudinal direction, the conductive path of the conductive metal is cut off and a defect occurs in the conductive layer 200 Can be. The conductor layer 200 of the present invention may be stretched along with the composite elastic substrate 100 including the elastic polymer 210 having elasticity. For example, the elastic polymer 210 may include silicone rubber, and more preferably, it may be Ecoflex.

According to an embodiment of the present invention, when the length of the composite elastic substrate 100 increases in one direction, the conductor layer 200 may increase in length in one direction while being in contact with the second elastic layer 120. have. When the composite elastic substrate 100 including the first elastic body layer 110 excellent in elasticity is stretched in the longitudinal direction, the conductor layer 200 is also stretched in the longitudinal direction together, in an electronic device including the elastic conductor 10 The conductive path can be kept long.

At this time, the second elastic layer 120 may also serve as a bridge that bonds the first elastic layer 110 and the conductor layer 200. When the conductor layer 200 is directly formed on the first elastic layer 110, since the two layers have different characteristics, when the first elastic layer 110 stretches in the longitudinal direction, the conductor layer 200 slides It may not be stretched in the longitudinal direction. This means that only the substrate is stretched from the stretchable conductor, and the conductor layer 200 serving as an electrode or electric wire can be fixed. However, when forming the composite elastic substrate 100 with the second conductor layer 120 interposed between the first elastic layer 110 and the conductor layer 200, the first elastic layer 110 is stretched and contracted in the longitudinal direction. When the second elastic layer 120 is in contact with the conductor layer 200 to prevent slipping, the composite elastic substrate 100 and the conductor layer 200 can be stretched and contracted with the same behavior.

According to an embodiment of the present invention, when the length of the composite elastic substrate 100 increases in one direction, the conductor layer 200 may increase in length in the range of 1600% to 1800% compared to the initial one-way length. The stretchable conductor 10 of the present invention includes a composite elastic substrate 100 having excellent stretchability, and a final stretch length compared to a length in an initial one direction may be 16 to 18 times.

In addition, the conductive layer 200 of the stretchable conductor 10 may have a small change in resistance value before and after stretching in one direction. As described above, when the thickness of the second elastic layer 120 is thinly stacked, the composite elastic substrate 100 may maintain the properties of the first elastic layer 110 at a similar level. Since the first elastic layer 110 has a lower modulus of elasticity than the second elastic layer 120, it has excellent elasticity and high stability against hysteresis. This means that the initial characteristics can be maintained when the stretched conductor 10 is stretched in the longitudinal direction and then restored to the initial state. Therefore, a change in resistance value before and after stretching of the conductor layer 200 serving as a conductor of the stretchable conductor 10 is small, and there is an effect of excellent stability.

As described above, the stretchable conductor 10 of the present invention is excellent in stretchability, including the composite elastic substrate 100 and the conductor layer 200. In addition, since it has high stability against repeated execution, it is possible to maintain conductivity characteristics before and after stretching.

Hereinafter, a method of manufacturing the stretchable conductor 10 according to an embodiment of the present invention will be described with reference to FIGS. 3 and 4.

3 is a schematic diagram showing a method of manufacturing the stretchable conductor 10 according to an embodiment of the present invention, and FIG. 4 is a flow chart showing a method of manufacturing the stretchable conductor 10.

3 and 4, the method of manufacturing the stretchable conductor 10 of the present invention includes: (a) preparing a conductive layer ink in which a conductive metal is dispersed in an elastic polymer (S100), (b) a first elastic layer And laminating a second elastic layer to produce a composite elastic substrate (S200) and (c) transferring a conductive layer formed of a conductive layer ink to at least a portion of the composite elastic substrate (S300).

First, (a) preparing a conductive layer ink (S100) will be described. The conductive layer ink includes the aforementioned conductive metal 220, an elastic polymer 210, and a solvent. (A) The step (S100) of preparing the conductor layer ink comprises: (a1) mixing the prepolymer and the crosslinking agent of the elastic polymer 210, and stirring it with a solvent to prepare a mixture; and (a2) the conductive metal ( 220) may be added.

It is prepared in a partially polymerized form by mixing a pre-polymer and a crosslinking agent of the polymerized and uncured elastic polymer 210. Then, a solvent is added to prepare a mixture, and the conductive metal 220 is added in a flake form to prepare a conductive layer ink. As an example, the solvent may include methyl-iso-butyl-ketone (MIBK).

The conductor layer ink may be transferred to the composite elastic substrate 100 by forming the conductor layer 200, and the conductive properties and blurring of the conductor layer 200 may be adjusted according to the content ratio of the conductor layer ink. For example, with respect to 100 parts by weight of the conductive layer ink, the conductive metal 220 may contain 68.5 parts by weight to 71.5 parts by weight of the elastic polymer 210, 14.5 parts by weight to 16.5 parts by weight, and 13.5 parts by weight to 15.5 parts by weight of the solvent Can be. As described above, since the conductive properties of the conductive layer 200 may be changed when the composite elastic substrate 100 is stretched according to the content of the conductive metal 220, the content of the conductive metal 220 of the ink of the conductive layer is adjusted. There is a need.

In addition, when forming the conductor layer 200, a smear phenomenon may be formed on the conductor layer 200 by interacting with a film to which the conductor layer ink is applied. When the content of the solvent is large, the viscosity of the conductive layer ink may be lowered, which may increase smearing. It is possible to suppress blurring by increasing the influence of the viscosity of the conductive layer ink rather than interacting with the film. Therefore, it is possible to control the bleeding phenomenon when the conductor layer 200 is formed by adjusting the solvent content of the conductor layer ink. For example, the conductive layer ink may have a conductive metal: elastic polymer: solvent content of 7.2g: 1.6g: 1.5g.

Next, the composite elastic substrate 100 may be manufactured by applying a first elastic solution to the second elastic layer 120 with a binder.

According to an embodiment of the present invention, (b) preparing a composite elastic substrate 100 comprises: (b1) preparing a first elastomer solution by mixing a first elastomer unit and a crosslinking agent, (b2) a second Forming a second elastic layer 120 by applying a mixture comprising an elastomeric unit and a crosslinking agent on a polymer film and curing it, (b3) applying a binder on the second elastic layer 120, (b4) ) A step of forming a first elastic layer 110 on the second elastic layer 120 and (b5) polymer by applying a first elastic solution on the second elastic layer 120 coated with a binder and curing it, And removing the film.

First, (b1) a first elastomer solution is prepared by mixing the first elastomer unit and a crosslinking agent. The first elastic layer 110 may be, for example, a hydrogel, and a first elastic solution in a state that is not completely cured is prepared by mixing a hydrogel unit and a crosslinking agent.

Then, (b2) a mixture comprising a second elastic unit and a crosslinking agent is prepared. A mixture comprising a second elastomeric unit and a crosslinking agent in a completely uncured state, such as a first elastomeric solution, is prepared. Then, the mixture is applied on a polymer film and cured to form a second elastic layer 120. At this time, the step of applying the mixture may be performed by a spin coating method. The polymer film may be a film that can be commonly used, for example, a PET film. The mixture is spin coated on a PET film and cured to form a second elastic layer 120. Preferably, the second elastic layer 120 may be formed in the form of a thin film.

Next, (b3) a binder capable of bonding the first elastic layer 110 and the second elastic layer 120 is coated on the second elastic layer 120, and (b4) the second elastic body coated with the binder The first elastic body solution is coated on the layer 120 and cured to form the first elastic layer 110 on the second elastic layer 120. The binder may be applied on the second elastic layer 120 with a material such as benzophenone, and the first elastic solution may be applied to have a specific shape. The applied first elastic body solution is cured by performing a heat treatment process to form the first elastic body layer 110.

Finally, by removing the polymer film (b5), a composite elastic substrate 100 including the second elastic layer 120 stacked on the first elastic layer 110 is manufactured. At this time, the first elastic layer 110 and the second elastic layer 120 are attached by a binder.

Then, the conductive layer 200 is transferred to at least a portion of the composite elastic substrate 100 to manufacture the stretchable conductor 10.

According to an embodiment of the present invention, (c) the step of transferring the conductor layer 200, (c1) the step of applying the conductor layer ink to a Teflon film, (c2) heat treatment of the applied conductor layer ink And curing the elastic polymer 210 to form the conductor layer 200, (c3) separating the conductor layer 200 from the Teflon film using a water-soluble tape, and (c4) the separated conductor layer 200 It may include the step of transferring to the at least a portion of the surface of the second elastic layer 120 of the composite elastic substrate is formed, and removing the water-soluble tape.

When forming the conductor layer 200, a heat treatment process is required to cure the elastic polymer 210 and sinter the conductive metal 220. At this time, when printing and heat-treating the conductor layer ink directly on the composite elastic substrate 100, the first elastic layer 110 of the composite elastic substrate 100 may be cured by heat treatment or moisture may be removed. This causes a problem of deteriorating the elasticity of the stretchable conductor 10. Therefore, in order to solve the above problems, the present invention manufactures the stretchable conductor 10 by transferring the conductor layer 200 onto the composite elastic substrate 100 using a water-soluble tape.

First, (c) the step of transferring the conductor layer 200, (c1) the conductor layer ink is applied to a Teflon film, (c2) the applied conductor layer ink is heat treated and the elastic polymer 210 is cured. To form the conductor layer 200. Since the Teflon film is a non-adhesive material, the adhesive force with the conductor layer 200 is relatively weak. Therefore, there is an advantage of easy separation of the conductor layer 200 by a water-soluble tape to be described later. In addition, even if a heat treatment process of the conductor layer ink is performed, there is an advantage that it is not deformed due to the stability of the Teflon film.

The heat treatment step may be performed through three steps. Heat treatment at a low temperature in step 1 to evaporate the solvent and cure the elastomer 210. Then, the uncured elastic polymer 210 is cured through heat treatment in steps 2 and 3 in which the temperature is relatively high, and the conductive metal 220 is sintered. The above heat treatment process is only an example of the present invention, but is not limited thereto. Through the above process, the conductor layer 200 is formed on the Teflon film using the conductor layer ink.

Next, the conductor layer 200 formed on the Teflon film is separated from the Teflon film using (c3) water-soluble tape, and (c4) the separated conductor layer 200 is the second elastic layer of the composite elastic substrate 100 (120) is transferred to at least a portion of the formed surface, and the water-soluble tape is removed to prepare a stretchable conductor (10).

Since the adhesion between the conductor layer 200 and the water-soluble tape is stronger than the adhesion between the conductor layer 200 and the Teflon film, the conductor layer 200 can be easily separated using the water-soluble tape. The conductive layer 200 attached to the water-soluble tape is transferred to one surface on which the second elastic layer 120 of the composite elastic substrate 100 is formed. As described above, when the composite elastic substrate 100 is stretched, the conductor layer 200 may be stretched in contact with the second elastic layer 120, so that the surface contacting the first elastic layer 110 The second elastic body layer 120, which is the opposite surface of, is transferred to one surface. And, it can be dissolved in water to remove the water-soluble tape.

Since the elastic conductor 10 manufactured by the above method performs a heat treatment process for curing the elastic polymer 210 of the conductor layer 200 and sintering the conductive metal 220 on the Teflon film, the composite elastic substrate by heat treatment It has an advantage of preventing deformation of (100) and not deteriorating elasticity. In addition, since the conductor layer 200 is transferred using a water-soluble tape, the post-treatment process also has an advantage.

As described above, the method for manufacturing the stretchable conductor 10 of the present invention has an effect of not reducing the stretchability of the composite elastic substrate 100 by transferring the conductor layer 200 using a water-soluble tape.

Hereinafter, examples and experimental examples for helping understanding of the present invention will be described. However, the following Examples and Experimental Examples are only to help understanding of the present invention, and the Examples and Experimental Examples of the present invention are not limited to the following Examples and Experimental Examples.

Example 1: Preparation of a stretchable conductor having a hydrogel / ecoplex composite elastic substrate

1) Preparation of Ag flake ink and conductive polymer layer

First, a conductor layer ink containing a conductive metal for forming a conductor layer is prepared. Prepare silver (Ag) flakes as the conductive metal and eco-flex as the elastic polymer.

The prepolymer of the elastic polymer Ecoplex and the crosslinking agent are mixed for 5 minutes at a ratio of 1: 1 (w / w), and the solvent methyl-iso-butylketone (MIBK) is added. And mix for 10 minutes. Then, silver (Ag) flakes are added to the above-mentioned mixed solution, stirred for 5 hours and stirred. At this time, the content ratio of the mixed solution (silver flake: Ecoflex: MIBK) is mixed to be 7.2 g: 1.6 g: 1.5 g to prepare a conductive layer ink.

The conductor layer ink is printed on a Teflon film, and heat treatment in three steps is performed to form the conductor layer 200. In the heat treatment step, first, heat treatment is performed at a temperature of 60 ° C. for 1 hour to evaporate the solvent MIBK and partially cure the elastic polymer echoplex. Then, by heat treatment at 110 ° C. for 2 hours and 130 ° C. for 2 hours, the conductor layer ink is completely cured and the silver flake is sintered. Through the above process, a conductor layer 200 in which silver flakes are dispersed in a Teflon film is formed.

2) Preparation of hydrogel solution

A hydrogel solution included in the first elastic layer 110 of the composite elastic substrate 100 is prepared. Prepare sodium alginate (Na (C ₆ H ₈ O ₆ ) _n ) in which calcium sulfate (CaSO ₄ ) is bound by an ionic crosslinking agent. Then, an acrylamide monomer is prepared to form a polyacrylamide structure.

First, the sodium alginate and acrylamide are mixed in distilled water in a weight ratio of 9: 1, stirred for 24 hours and stirred to obtain a mixture. Then, ammonium persulfate (Ammonium persulfate, (NH ₄ SO ₄ ) ₂ ) is added as a photoinitiator for the polymerization of acrylamide, and N, N-methylenebisacrylamide is added as a crosslinking agent. . After the mixture was stirred for 1 hour, 0.06 g of calcium sulfate was dissolved in 10 mL of water and then added as a crosslinking agent, and N, N, N ', N'-tetramethylethylenediamine (a crosslinking accelerator for polyacrylamide) N, N, N ', N'-tetramethylethylenediamine, TEMED). Through the above process, a hydrogel solution included in the first elastic layer is prepared.

3) Preparation of composite elastic substrate

A composite elastic substrate is prepared by using the hydrogel solution prepared in "2) Preparation of hydrogel solution" and Ecoflex, a silicone rubber.

As the second elastic layer 120, an ecoplex that is silicone rubber is prepared. The prepolymer and crosslinking agent of Ecoflex were mixed in a weight ratio of 1: 1 (w / w) for 5 minutes, and the prepared mixture was spin coated at a speed of 3000 rpm to have a thickness of 250 μm on the PET film to form an Ecoflex thin film. do. Then, the thin film is cured for 12 hours to planarize the surface of the thin film.

Subsequently, the first elastic layer 110 and the second elastic layer 120 are attached to the binder, and the surface treatment with benzophenone (Benzophenon) on the eco-flex thin film layer. This is performed by preparing an ethanol solution containing 2 wt% of benzophenone (dipping) into the Ecoplex thin film.

Then, after pouring the hydrogel solution prepared in "2) Preparation of hydrogel solution in the form of a film on the Ecoflex thin film, and curing with UV / O ₃ for 5 minutes, it is placed in a Humidity box for 24 hours. A composite elastic substrate 10 (hydrogel / ecoplex) in which the first elastic layer 110 including the hydrogel and the second elastic layer 120 including the eco-flex thin film are stacked is prepared by the above method.

4) Ag conductor layer transfer

The conductive polymer layer 200 in which silver flakes are dispersed in “1) Preparation of Ag Flake Ink and Conductor Polymer Layer” is transferred to the composite elastic substrate 100 to prepare a stretchable conductor 10.

First, the conductor layer 200 formed on the Teflon film is removed using a water-soluble tape. This is transferred onto the composite elastic substrate 100 removed from the PET film, and dissolved in distilled water to remove the water-soluble tape.

Through the process of 1) to 4), it is possible to manufacture a stretchable conductor according to an embodiment of the present invention. At this time, the prepared elastic conductor is hereinafter referred to as "Example 1".

Comparative Example 1: Preparation of stretchable conductor of hydrogel substrate (DNHG)

In Example 1, a conductor (DNHG) was prepared in the same manner except that the hydrogel / ecoplex composite elastic substrate prepared in “3) Preparation of Composite Elastic Substrate was manufactured as a hydrogel substrate. The conductor thus prepared is hereinafter referred to as "Comparative Example 1".

Comparative Example 2: Preparation of stretchable conductor of ecoflex substrate (ECO-T)

In Example 1, the conductor (ECO-T) was prepared in the same manner, except that the hydrogel / ecoflex composite elastic substrate prepared in "3) Preparation of Composite Elastic Substrate" was manufactured as an ecoflex substrate. The conductor thus prepared is hereinafter referred to as "Comparative Example 2".

Comparative Example 3: Preparation of stretchable conductor of ecoflex substrate (ECO-P)

In Example 1, a hydrogel / ecoplex composite elastic substrate prepared in "3) Preparation of Composite Elastic Substrate" was prepared as a hydrogel substrate, and a conductive layer containing silver flakes was formed on the substrate by printing. Prepares the conductor (ECO-P) in the same way. The conductor thus prepared is hereinafter referred to as "Comparative Example 3".

5 is a scanning electron microscope (SEM) photograph showing a cross-section of a stretchable conductor according to an embodiment of the present invention. Referring to FIG. 5, the elastic conductor 10 of Example 1 is attached with a hydrogel layer, which is the first elastic layer 110, and an eco-flex layer, which is the second elastic layer 120, and is stacked to form a composite elastic substrate. It forms (100). At this time, the eco-flex layer has a thickness of 30 μm and is relatively thin. In addition, a conductor layer 200 in which silver flakes 220 are dispersed is formed on the upper portion.

6 is a scanning electron microscope (SEM) photograph showing a cross section of a conductor layer in which silver (Ag) flakes of a stretchable conductor according to an embodiment of the present invention are dispersed.

Referring to FIG. 6A, the conductor layer 200 of Example 1 is about 40 μm thick. And, as shown in (b) and (c) of Figure 6, silver (Ag) flake 220 is dispersed in the conductor layer 200, the average particle size of the flake is a value of about 1 to 3 ㎛ You can see that it has.

Hereinafter, the properties of the stretchable conductor produced in this embodiment will be described.

Experimental Example 1: Evaluation of stretchability of stretchable conductor

First, with reference to FIGS. 7 to 9, the elasticity evaluation of the conductors according to the examples and comparative examples will be described.

First, the maximum degree of stretching was evaluated using the stretchable conductor 10 of Example 1. The maximum stretch length of the stretchable conductor 10 in which the conductor layer 200 was formed on the composite elastic substrate 100 of Example 1 was measured. The stretchable conductor 10 of Example 1 is formed on a PET film, and it is fixed with an epoxy film. And the PET film and Example 1 were stretched in the longitudinal direction using a machine, and the results are shown in FIG. 7.

7 is a photograph showing the result of measuring the maximum degree of stretch of the stretchable conductor according to an embodiment of the present invention.

Referring to FIG. 7, Example 1 formed on the initial PET film had a length of 4 mm, but when stretched to the maximum, the length was 75.2 mm. That is, Example 1 has an elasticity of 1780%.

Next, using the stretched conductors prepared in Example 1, Comparative Examples 1 and 2, when the conductor was stretched in the longitudinal direction, the stress change of the conductor and the degree of stretching of the conductor layer were evaluated. First, only the substrates of Examples 1 and Comparative Examples 1 and 2 were manufactured, and the stress change when stretched by 400% in the longitudinal direction, respectively, was measured, and the results are shown in FIG. 8.

8 is a photograph showing stress evaluation results of a conductor substrate according to Comparative Examples and Examples of the present invention and a stress-strain graph.

According to (a) of FIG. 8, when three different substrates are stretched 400% in the longitudinal direction, it can be seen that the extent of each stretch is similar. It can be seen that the composite elastic substrate of Example 1 is excellent in elasticity, such as the hydrogels and Ecoflex of Comparative Examples 1 and 2.

However, according to FIG. 8 (b), the substrates have different elastic modulus. Example 1 and Comparative Examples 1 and 2 of the stress-strain graph, according to each of the tensile modulus (Tensile modulus) has a value of each of ^{0.005N / mm 2, 0.004N / mm} 2 and 0.69N / mm ^2. This is because the composite elastic substrate of Example 1 has a thin eco-flex thin film formed on the hydrogel substrate of Comparative Example 1, and thus may have a tensile force coefficient of almost the same level as that of Comparative Example 1. When the conductor has a low modulus of elasticity, conformal contact is possible on a curved surface, and a high level of stability can be obtained even when the surface is moved.

In addition, by evaluating the stress-strain graph when each substrate was stretched 300% in the longitudinal direction and then restored to its initial state, the hysteresis characteristics of the substrate were evaluated, and the results were shown in FIG. 8 (c). Shown. It can be seen that, compared to the ecoflex substrate of Comparative Example 2, the substrates including the hydrogel layers of Example 1 and Comparative Example 1 were better stretched in the longitudinal direction and then restored to the initial state. That is, the composite elastic substrate of Example 1 includes the hydrogel layer as the first elastic layer, and has a low elastic modulus and excellent hysteresis characteristics, and thus has excellent elasticity.

Then, the elasticity was evaluated using the conductors of Example 1, Comparative Examples 1 and 2 in which a conductor layer containing silver (Ag) flakes was formed, and the results are shown in FIG. 9.

9 is a photograph showing a result of evaluation of stretchability of a conductor layer formed on a stretchable conductor according to Comparative Examples and Examples of the present invention.

FIG. 9 (a) shows the initial state of the conductors according to Example 1, Comparative Examples 1 and 2, and FIG. 9 (b) shows the conductor layer formed on the substrate when the substrates of the conductors are stretched 100%. It shows the degree of stretching.

Referring to (a) and (b) of FIG. 9, in the case of Example 1 and Comparative Example 2 including the echoplex layer on the substrate of the stretchable conductor, the length of the conductor layer also increases when the substrate is stretched in the longitudinal direction. , In the case of Comparative Example 1 containing only a hydrogel, it can be seen that the conductor layer does not extend in the longitudinal direction.

The conductive layer in which silver (Ag) flakes are dispersed is hydrophobic, and the hydrogel has hydrophilic properties. In the case of Comparative Example 1 in which the hydrophilic hydrogel layer had a conductor layer directly formed thereon, even if a silver flake conductor layer was formed on the substrate, it was not attached due to different characteristics, and the conductor layer did not stretch while sliding when the substrate stretched in the longitudinal direction. On the other hand, in the case of Example 1 and Comparative Example 2 in which a hydrophobic ecoflex layer was formed on the substrate, when the substrate was stretched by fixing the hydrophobic conductor layer without slipping by the echoplex layer, the conductor layer may also be stretched.

9 (c) is an SEM photograph showing a cross section of the stretchable conductor 10 of Example 1. The hydrophobic ecoflex layer 120 is well attached to the conductive layer 200 in which silver (Ag) flakes 220 transferred thereon are dispersed, and the hydrophilic hydrogel layer 110 at the bottom is also used for the benzophenone binder. It can be seen that it is well attached. That is, the eco-flex layer, which is the second elastic layer 120 of Example 1, may serve to connect the conductor layer 200 and the first elastic layer 110 having different characteristics. Due to this, the elasticity of the conductor layer 200 may be improved together with the hydrogel layer 110 having a low elastic modulus and excellent elasticity.

Experimental Example 2: Evaluation of elastic conductor history

Next, by using the conductors according to Example 1, Comparative Examples 2 and 3 above, a history evaluation according to longitudinal stretching is performed. The conductors according to Example 1, Comparative Examples 2 and 3 above have different substrates or different methods of forming a conductor layer.

First, in order to confirm the clarity of the conductor layer according to the method of forming the conductor layers of Examples 1 and 2 and 3, the surface of the conductor layer was measured with a scanning electron microscope and shown in FIG. 10.

10 is a scanning electron microscope (SEM) photograph showing the surface of a conductor layer according to Comparative Examples and Examples of the present invention. 10 (a) to 10 (c) show the conductor layers of Comparative Example 3, Comparative Example 2, and Example 1, respectively. In the case of Comparative Example 3, since a direct printing method was used for the formation of the conductor layer, it can be seen that the blurring phenomenon was large in the conductor layer pattern on the substrate. On the other hand, in the case of Comparative Example 2 and Example 1, since the transfer was carried out using a water-soluble tape, the blurring phenomenon in the conductor layer pattern on the substrate was small. This is because when the conductor layer is transferred from the Teflon film, the remaining conductor layer ink is removed. That is, since the conductor layer is formed by transferring using a water-soluble tape, a clear conductor pattern can be formed.

In addition, when evaluating the hysteresis of the conductor, the change (ΔR / R ₀ ) of the resistance value to the initial resistance value was measured when stretching in the longitudinal direction. The conductor is broken by stretching, or the resistance value change when 100% stretched and restored is measured, and the results are shown in FIG. 11.

11 is a graph showing a result of measuring a change in resistance when stretching a stretchable conductor according to Comparative Examples and Examples of the present invention.

Referring to (a) of FIG. 11, it can be seen that the conductors of Example 1, Comparative Examples 2 and 3 have different maximum stretchable lengths and different resistance values. In the case of Comparative Example 2 (ECO-T), it is possible to stretch up to 600%, and in the case of Comparative Example 3 (ECO-P), it is possible to stretch up to 500%. Even if the same echo-flex substrate is used, it can be seen that when the conductor layer is directly printed as in Comparative Example 3, the echo-flex of the substrate is excessively hardened during the heat treatment process of silver (Ag) flakes, and thus the elasticity is slightly reduced. On the other hand, in the case of the stretchable conductor 10 including the composite elastic substrate 100 of Example 1, since the conductor layer was transferred using a water-soluble tape so that the substrate had excellent stretchability and the substrate was not cured, 1780% It is possible to stretch.

Referring to (b) of FIG. 11, it can be seen that the conductors of Examples 1, Comparative Examples 2, and 3 were stretched 100% and then recovered in a different form of resistance when recovering. In the case of Example 1 and Comparative Example 2, the graph of change in resistance value during stretching and recovery has a relatively linear shape, but in Comparative Example 3, it can be seen that the change in resistance value during recovery is not constant. have.

This means that when the conductors of Embodiment 1 and Comparative Example 2 are stretched and stretched in the longitudinal direction, the change in resistance value has stable characteristics. In particular, in the case of ECO-P in which the conductor layer of Comparative Example 3 was formed by a printing method, the change in resistance value is not constant, because the recovery mechanism after stretching is different from Example 1 and Comparative Example 2. Comparative Example 3 follows the recovery mechanism of the Ecoflex substrate because the conductor layer was formed directly on the Ecoflex substrate, whereas Example 1 and Comparative Example 2 form a different physical contact with the substrate because the conductor layer was formed by being transferred. Therefore, when the conductor layer is formed by transferring using a water-soluble tape, it can have a more stable resistance value recovery characteristic.

And, Figure 11 (c) is a graph showing a change in resistance value when the 50% stretch and recovery process of Example 1 was repeated 1000 times. Referring to this, it can be seen that the stretchable conductor of Example 1 does not have a large change in resistance value along the longitudinal stretch, and has stable resistance value change characteristics even after repeated several times.

After stretching the conductors of Example 1 and Comparative Example 400 by 400%, the form in which silver (Ag) flakes on the conductor layer were dispersed was observed with a scanning electron microscope and the results are shown in FIG. 12.

12 is a scanning electron microscope (SEM) photograph showing a form in which silver (Ag) flakes are dispersed in a conductor layer according to Comparative Examples and Examples of the present invention. Referring to FIG. 12, when the conductor is stretched 400% in the longitudinal direction, a certain level of conductivity is maintained, but a cavity is formed on the conductor layer. At this time, as the silver (Ag) flakes are rearranged in the conductor layer, conductivity may be partially recovered, and there is a difference in rearrangement characteristics depending on the type of the substrate. In the stretched state at 400%, the interval between silver (Ag) flakes was larger in Comparative Example 3 than in Example 1. This means that the conductor of Comparative Example 3 has a large resistance due to stretching, and rearrangement of the conductive path of silver (Ag) flakes is suppressed. Therefore, since the conductor of Example 1 has excellent rearrangement characteristics of the conductive path of the silver flake for stretching, the conductive path is rearranged so that the change in resistance value due to stretching is small.

Experimental Example 3: Performance test of stretchable conductor

A performance test of an electronic device that can be manufactured using the stretchable conductor of Example 1 is performed.

First, the flexible conductor of Example 1 is used as a wire for LEDs, and the change in the LED light source during the stretching of the wires is tested. 13 is a photograph showing a wire test for LEDs using a stretchable conductor according to an experimental example of the present invention.

Referring to FIG. 13, the stretchable conductor of Example 1 is arranged in the form of “KIST” to form a wire, and a green LED light source is connected. Then, the change in the LED light source was measured by increasing the "KIST" wire by 200%. As a result, since the stretched conductor of Example 1 maintains the conductor properties even when stretched in the longitudinal direction, it can be seen that light enters the LED.

In addition, a smart patch capable of being attached to the human body was manufactured by manufacturing the pressure sensor to which the elastic conductor of Example 1 was connected. The smart patch was prepared by forming a PEDOT thin film on the stretchable conductor of Example 1, and forming a gold (Au) thin film electrode having a microstructure thereon.

After attaching the manufactured smart patch to the back of the hand, bending the finger, pinning it, and then applying pressure to the pressure sensor again to observe the functional change as a pressure sensor, and the results are shown in FIG. 14.

14 is a photograph showing an experiment of a smart patch pressure sensor using a stretchable conductor according to an experimental example of the present invention. Referring to FIG. 14, the stretchable conductor of Example 1 is able to maintain initial conductivity characteristics even after being stretched and recovered in the longitudinal direction by bending a finger.

The present invention has been illustrated and described with reference to preferred embodiments, as described above, but is not limited to the above embodiments and is varied by those skilled in the art to which the present invention pertains without departing from the spirit of the present invention. Modifications and modifications are possible. Such modifications and variations are to be regarded as falling within the scope of the invention and appended claims.

10: elastic conductor
100: composite elastic substrate
110: first elastic layer
120: second elastic body layer
200: conductor layer
210: elastomer
220: conductive metal

Claims (14)

A composite elastic substrate including a first elastic layer and a second elastic layer laminated on the first elastic layer; And
A conductive layer including an elastic polymer in which a conductive metal is dispersed, and formed on at least a portion of the composite elastic substrate
Including,
The second elastic body layer has a larger elastic modulus than the first elastic body layer,
The first elastic layer is a hydrogel, the second elastic layer is 10㎛ to 50㎛ thick silicone rubber (Silicon rubber), the elastic polymer comprises a silicone rubber (Silicon rubber),
The conductive metal is dispersed in a flake form in the elastic polymer,
When the conductive layer is referred to as 100 parts by weight, the content of the conductive metal is 75 parts by weight to 85 parts by weight,
When the length of the composite elastic substrate increases in one direction, the conductor layer extends in one direction while in contact with the second elastic layer, and the conductor layer and the second elastic layer are the first elastic layer Stretched in the same ratio as, the composite elastic substrate can be stretched to 1600% to 1800% of the initial length,
Elastic conductor. delete According to claim 1,
The conductive metal includes any one of silver (Ag), copper (Cu), and gold (Au),
The elastic polymer is a silicone rubber (Silicon rubber), a stretchable conductor. delete According to claim 1,
The first elastic layer is a stretchable conductor that is 3 to 50 times thicker than the thickness of the second elastic layer. delete delete delete (A) preparing a conductive layer ink in which a conductive metal is dispersed in an elastic polymer;
(b) stacking the first elastic body layer and the second elastic body layer to produce a composite elastic substrate; And
(c) transferring a conductor layer formed of the conductor layer ink to at least a portion on the composite elastic substrate.
Including,
Step (b) is,
(b1) preparing a first elastic solution by mixing the first elastic unit and a crosslinking agent;
(b2) forming a second elastic layer having a thickness of 10 µm to 50 µm by applying a mixture comprising a second elastic unit and a crosslinking agent on a polymer film using a spin coating method and curing the mixture;
(b3) applying a binder on the second elastic layer;
(b4) forming a first elastic layer on the second elastic layer by applying the first elastic solution on the second elastic layer coated with the binder and curing the solution; And
(b5) removing the polymer film
It includes,
The second elastic body layer has a larger elastic modulus than the first elastic body layer,
The first elastic layer is a hydrogel, the second elastic layer is 10㎛ to 50㎛ thick silicone rubber (Silicon rubber), the elastic polymer comprises a silicone rubber (Silicon rubber),
The conductive metal is dispersed in a flake form in the elastic polymer,
When the conductive layer is referred to as 100 parts by weight, the content of the conductive metal is 75 parts by weight to 85 parts by weight,
When the length of the composite elastic substrate increases in one direction, the conductor layer extends in one direction while in contact with the second elastic layer, and the conductor layer and the second elastic layer are the first elastic layer Stretched in the same ratio as, the composite elastic substrate can be stretched to 1600% to 1800% of the initial length, the method of manufacturing a stretchable conductor. The method of claim 9,
Step (a) is,
(a1) mixing the prepolymer of the elastic polymer and a crosslinking agent, and stirring the mixture with a solvent to prepare a mixture; And
(a2) adding flakes of the conductive metal to the mixture
A method of manufacturing a stretchable conductor comprising a. The method of claim 10,
The elastic polymer comprises a silicone rubber (Silicon rubber),
The conductive metal includes any one of silver (Ag), copper (Cu), and gold (Au),
The solvent comprises a methyl-iso-butyl-ketone (Methyl-iso-butyl-ketone, MIBK), a method for producing a stretchable conductor. delete delete The method of claim 9,
Step (c) is,
(c1) applying the ink of the conductor layer to a Teflon film;
(c2) heat-treating the applied conductor layer ink and curing the elastic polymer to form a conductor layer;
(c3) separating the conductor layer from the Teflon film using a water-soluble tape; And
(c4) transferring the separated conductor layer to at least a portion of one surface on which the second elastic layer of the composite elastic substrate is formed, and removing the water-soluble tape;
A method of manufacturing a stretchable conductor comprising a.

Images