WO2018101724A1

WO2018101724A1 - Conductive flexible element

Info

Publication number: WO2018101724A1
Application number: PCT/KR2017/013767
Authority: WO
Inventors: 주영창; 이영주; 임승민; 양정권; 최광묵; 진민기; 이정호
Original assignee: 서울대학교산학협력단
Priority date: 2016-11-29
Filing date: 2017-11-29
Publication date: 2018-06-07

Abstract

The present invention relates to a conductive flexible element. The conductive flexible element (1) of the present invention comprises: a substrate unit (10); and an electrode unit (20) disposed on at least one surface of the substrate unit (10), wherein an auxetic structure (30) is inserted into the substrate unit (10).

Description

Conductive Flexible Element

The present invention relates to a conductive flexible element. More specifically, the present invention relates to a conductive flexible device in which the Poisson's ratio of the substrate portion and the electrode portion is adjusted to improve tensile properties, elasticity and reliability.

Recently, a lot of researches have been conducted on conductive flexible devices in which electrodes are formed on flexible substrates, away from conductive devices on which electrodes are formed on rigid substrates. In particular, the conductive flexible element may be applied to a flexible device, a wearable device, or the like, and furthermore, may be used as a sensor, an electrode, or the like, attached to the skin or in the human body.

Looking at the type of the prior art to ensure flexibility and bio-compatibility is as follows. First, as a technology focused on the structure of the metal electrode, the pattern of the metal electrode is made into a structure suitable for flexible characteristics such as wavy and horse-shoe. Secondly, as a technology focused on electrode materials, materials such as conductive polymers, CNTs, and graphene having excellent flexibility are employed.

As such, conventional conductive flexible devices are usually implemented by forming metal electrodes in a polymer material. The conductive flexible device thus implemented may be exposed to external forces such as pulling and folding. In this case, defects such as cracking and buckling may be caused by the difference in physical properties between the metal and the polymer material. There was a problem that occurred.

Elastic matching among the physical properties between the metal and the polymer material in the conductive flexible device becomes important. This is because when exposed to external forces such as pulling and folding, defects are generated at the interface because the metal and the polymer have different stretching properties. The Poisson's ratio, which means the ratio between the transverse strain and the longitudinal strain due to the vertically applied stress, can be considered as a value reflecting this stretching property.

1 is a graph showing Young's modulus and Poisson's ratio for various materials. 2 is a schematic diagram showing elastic mismatching between a metal and a polymeric material.

In FIG. 1, the Poisson's ratio of the elastomer is about 0.5, and the Poisson's ratio of the metal corresponds to about 3.5. As shown in FIG. 2A, an elastic polymer may be used as a support substrate, and a conductive thin film may be manufactured by bonding a metal thin film to an upper portion thereof. When an external force acts in a specific direction of the conductive flexible device, as shown in FIG. 2B, the elastic polymer substrate and the metal thin film may have different transverse and vertical strains according to the Poisson's ratio. As a result, as shown in (c) of FIG. 2, when a mismatch due to the difference of Poisson's ratio accumulates at the interface between the polymer substrate and the metal thin film, the interface adhesion is weakened or the metal thin film is damaged, thereby reducing the reliability of the flexible device. May result.

The present invention has been made to solve various problems including the above problems, and an object of the present invention is to provide a conductive flexible device capable of reducing the Poisson's ratio difference between the substrate material and the electrode material of the conductive flexible device.

In addition, an object of the present invention is to provide a conductive flexible device having improved tensile properties, elasticity and reliability.

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 substrate portion; And an electrode part disposed on at least one surface of the substrate part, wherein the substrate part is provided with a conductive flexible element into which an aoxetic structure is inserted.

In addition, according to an embodiment of the present invention, the substrate portion may be made of an elastic material.

In addition, according to an embodiment of the present invention, the Poisson's ratio of the substrate may be 0.47 to 0.52.

In addition, according to an embodiment of the present invention, the electrode portion may be made of a metal material.

In addition, according to an embodiment of the present invention, the electrode unit may include at least one of Au, Ag, Al, Cu, Ti.

In addition, according to an embodiment of the present invention, the Poisson's ratio of the electrode part may be 0.31 to 0.41.

In addition, according to an embodiment of the present invention, the oxetic structure may have a Poisson's ratio having a negative value.

In addition, according to an embodiment of the present invention, the oxtic structure may be made of an elastic material.

In addition, according to an embodiment of the present invention, an oxtic structure may be inserted into the substrate to reduce the Poisson's ratio.

According to one embodiment of the present invention made as described above, there is an effect that can reduce the Poisson's ratio difference between the substrate material and the electrode material of the conductive flexible device.

And, according to one embodiment of the present invention, there is an effect that can improve the tensile properties, elasticity and reliability.

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

1 is a graph showing Young's modulus and Poisson's ratio for various materials.

2 is a schematic diagram showing elastic mismatching between a metal and a polymeric material.

3 is a diagram illustrating non-auxetic and oxetic.

4 is a view showing an oxtic structure according to an embodiment of the present invention.

5 is a schematic diagram illustrating a manufacturing process of a conductive flexible device according to an embodiment of the present invention.

6 to 8 illustrate a process and results of measuring Poisson's ratio of the PDMS to which the oxtic structure according to the embodiment of the present invention is coupled and the PDMS according to the comparative example.

9 shows a conductive flexible device according to an embodiment of the present invention and a conductive flexible device according to a comparative example.

10 is a graph showing the tensile fatigue properties with or without the oxtic structure according to an embodiment of the present invention.

1: conductive flexible element

10: substrate portion

20: electrode part

30: oxtic structure

DETAILED DESCRIPTION The following detailed description of the invention refers to the accompanying drawings that show, by way of illustration, specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the 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 characteristics described herein may be embodied in other embodiments without departing from the spirit and scope of the invention with respect to one embodiment. In addition, it is to be understood that the location or arrangement of individual components within each disclosed embodiment may be changed without departing from the spirit and scope of the invention. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present invention, if properly described, is defined only by the appended claims, along with the full range of equivalents to which such claims are entitled. In the drawings, like reference numerals refer to the same or similar functions throughout the several aspects, and length, area, thickness, and the like may be exaggerated for convenience.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily implement the present invention.

3 is a diagram illustrating non-auxetic and oxetic.

Referring to FIG. 3A, when a general material, that is, non-auxetic materials, is stressed inside the material, the material expands in the corresponding direction and contracts in the vertical direction. Therefore, the Poisson's ratio, which means the ratio between the transverse strain and the longitudinal strain due to the vertical stress occurring inside the material, is positive.

Referring to (b) of FIG. 3, on the contrary, auxetic materials (or materials having an auxetic structure) may extend in a direction perpendicular to the corresponding direction when stress is applied to the material. . Thus, Poisson's ratio has a negative number.

4 shows an oxtic structure 30 according to an embodiment of the invention.

Referring to FIG. 4A, the conductive flexible device 1 of the present invention may be implemented to include an oxtic structure 30. While the prior arts focus on the structure of the electrode, the material of the electrode and the like, the conductive flexible element 1 of the present invention is characterized by focusing on adjusting the structure of the substrate portion 10. The conductive flexible device 1 having the oxtic structure 30 having the oxtic structure 30 inserted into the substrate 10 may be implemented.

The oxtic structure 30 may have a unit border in which a pair of triangles face each other, and vertex portions of the triangles overlap each other and are integrally connected. Such a unit border may have a shape in which the unit border is repeatedly arranged in the horizontal direction and the vertical direction. However, the oxtic structure 30 is not necessarily limited to this shape, and as long as the Poisson's ratio has a negative number, the oxtic structure 30 can be employed as the oxetic structure 30 of the present invention.

Referring to FIG. 4B, when a stress is applied to the oxtic structure 30, it may be extended 30 ′ in both the direction in which the stress is applied and the direction perpendicular thereto. That is, it may be extended 30 'in the direction in which the area occupied by the oxtic structure 30 becomes larger.

The oxtic structure 30 is preferably made of an elastic material so that when the stress is applied and released, the oxtic structure 30 'can be restored to its original form 30. FIG. 4C illustrates an embodiment in which the oxtic structure 30 is formed of an elastic silicone rubber.

5 is a schematic view showing a manufacturing process of the conductive flexible device 1 according to an embodiment of the present invention.

Referring to FIG. 5A, first, the substrate 10 and the oxtic structure 30 are prepared.

In order to secure flexibility and elasticity, the substrate unit 10 is preferably made of an elastic material. The elastic material may be composed of any one material selected from the group of elastomers of FIG. 1. The elastic material may have a Poisson's ratio of about 0.47 to 0.52. In the present specification, it is assumed that the substrate portion 10 made of PDMS (polydimethylsiloxane) is used.

The oxtic structure 30 may have a structure and a material described with reference to FIG. 4.

Next, referring to FIG. 5B, the oxtic structure 30 may be inserted into the substrate portion 10. The insertion of the oxtic structure 30 means that the substrate portion 10 and the oxtic structure 30 are manufactured, respectively, and then inserted into the substrate portion 10 by inserting the oxtic structure 30 into the substrate portion 10. Rather, it should be understood to include forming the oxtic structure 30 to be embedded in the substrate 10 in the process of forming the substrate 10.

For example, after the oxtic structure 30 is disposed on the glass, the glass and the oxtic structure 30 are coated with a solution mixed with a PDMS base and a curing agent 10: 1 on the glass, and then cured to form a PDMS substrate ( 10) and the oxtic structure 30 may be integrally formed.

Next, referring to FIG. 5C, the electrode part 20 may be formed on at least one surface of the substrate part 10. The electrode unit 20 may be formed by attaching a metal foil, or using a known thin film forming method such as printing, plating, physical vapor deposition (PVD), chemical vapor deposition (CVD), etc. without limitation. Can be.

The electrode unit 20 is preferably in the form of a wire having an electrode pattern such as a wave, horse-shoe, etc., so as to be suitable for the flexible property, but is not necessarily limited thereto. The material of the electrode unit 20 may be made of a material selected from the metal group of FIG. 1, that is, Au, Ag, Al, Cu, Ti, or the like. The metal material may have a Poisson's ratio of about 0.31 to 0.41.

The conductive flexible device 1 of the present invention is characterized in that it is adjusted to have a Poisson's ratio lower than the original Poisson's ratio of the substrate portion 10 as the oxtic structure 30 is inserted into the substrate portion 10.

For example, the PDMS substrate portion 10 has a Poisson's ratio of about 0.5, and the Cu electrode portion 20 has a Poisson's ratio of about 0.34. When the oxtic structure 30 having the negative Poisson's ratio is inserted into the PDMS substrate 10, the Poisson's ratio of the PDMS substrate 10 is lower than 0.5. That is, when the stress is applied to the PDMS substrate portion 10, it should be elongated in the stress application direction and reduced in the direction perpendicular to the stress application direction. It is also extended in the direction perpendicular to the direction, it can be prevented to some extent to shrink the PDMS substrate portion 10 in the vertical direction. As a result, the Poisson's ratio of the PDMS substrate portion 10 into which the oxtic structure 30 is inserted may be reduced.

When the Poisson's ratio of the PDMS substrate portion 10 into which the oxtic structure 30 is inserted is reduced to a degree similar to that of the Cu electrode portion 20, it acts on the interface between the PDMS substrate portion 10 and the Cu electrode portion 20. The stress can be reduced, and the occurrence of defects such as cracks and buckling in the electrode portion 20 can be reduced.

6 to 8 illustrate a process and results of measuring Poisson's ratio of the PDMS to which the oxtic structure according to the embodiment of the present invention is coupled and the PDMS according to the comparative example. 6 to 8, a change in Poisson's ratio of the substrate part 10 according to whether the oxtic structure 30 is inserted without looking at the electrode part 20 will be described.

Referring to FIG. 6, a PDMS substrate part having a thickness of 2 mm was manufactured according to a comparative example [FIG. 6A] (hereinafter, a “comparative sample”), and according to the example [FIG. 6B). A PDMS substrate part 10 having a thickness of 2 mm and having an oxtic structure 30 of Si rubber inserted therein was manufactured (hereinafter, an “sample”). In addition, while tensioning the comparative sample and the example sample using the tensile strength test equipment, the distance between the recognition points (marked with red dots) in each sample was measured to calculate the strain rate.

As shown in Fig. 7A, the Poisson's ratio was measured for three recognition points of Positions (1), (2), and (3) while pulling the comparative example sample. As a result, as in FIG. 7B, Poisson's ratio data at Positions (1), (2), and (3) of the comparative sample was measured to be about 0.71, 0.82, and 0.74.

In addition, as shown in Fig. 8A, the Poisson's ratio was measured for three recognition points of Positions (1), (2) and (3) while the Example sample was stretched. As a result, as in FIG. 8B, Poisson's ratio data at Positions (1), (2), and (3) of the example samples were measured to be about 0.23, 0.28, 0.44.

As a result of performing a 2-sample T test to confirm the significant difference between the example sample to which the oxetic structure 30 was applied and the comparative sample to which the oxetic structure 30 was not applied, the Poisson's ratio before applying the oxtic structure 30 was 0.76, It decreased to 0.32 after application.

9 shows a conductive flexible element 1 according to an embodiment of the present invention and a conductive flexible element 5 according to a comparative example. 10 is a graph showing the tensile fatigue properties with or without the oxtic structure according to an embodiment of the present invention.

Referring to FIG. 9, the conductive flexible device 1 of the present invention inserts / couples the oxtic structure 30 to the PDMS substrate portion 10 and bonds the Cu electrode portion 20. The Cu electrode unit 20 is preferably disposed to correspond to the direction in which the unit edge of the oxtic structure 30 is repeatedly arranged, but is not limited thereto. In the conductive flexible element 5 of the comparative example, the Cu electrode portion 20 was bonded to the PDMS substrate portion 10. The thickness of the board | substrate part 10 was 2 mm, and the thickness of the electrode part 20 was 2 micrometers.

Using the sample of Figure 9, the tensile strength was tested under the test conditions of the tensile force applied, 5% elongation, frequency 0.05 Hz. Referring to FIG. 10, the conductive flexible element 5 of the comparative example does not exceed 10 tensile tests and the electrode portion 20 breaks to show a high resistance value, whereas the conductive flexible element 1 of the embodiment is about 1000 times. It can be seen that the tensile fatigue property of the flexible element 1 in which the oxtic structure 30 is inserted / coupled by maintaining the property is excellent.

The Poisson's ratio is about 0.5 in the case of the polymer material not applied to the oxetic structure, and the Poisson's ratio is reduced to 0.3 in the case of the same polymer material in which the oxetic structure is applied. Since the Poisson's ratio of the metal is about 0.3, the tensile properties can be improved by adjusting the Poisson's ratio of the polymer and the metal material to a similar level through the oxetic structure.

As described above, the present invention has an effect of reducing the Poisson's ratio difference between the substrate material and the electrode material of the conductive flexible device by inserting the oxtic structure in the polymer substrate. In addition, by improving tensile properties, elasticity, and reliability, there is an effect applicable to a flexible device, a wearable device, and the like.

Although the present invention has been shown and described with reference to preferred embodiments as described above, it is not limited to the above embodiments and various modifications made by those skilled in the art without departing from the spirit of the present invention. Modifications and variations are possible. Such modifications and variations are intended to fall within the scope of the invention and the appended claims.

Claims

A substrate portion; And

An electrode portion disposed on at least one surface of the substrate portion

Including,

An oxetic structure is inserted into the substrate portion, the conductive flexible device.
The method of claim 1,

The substrate portion is made of an elastic material, conductive flexible device.
The method of claim 2,

Poisson's ratio of the substrate portion is 0.47 to 0.52, the conductive flexible device.
The method of claim 1,

The electrode unit is made of a metal material, conductive flexible device.
The method of claim 4, wherein

The electrode unit includes at least one of Au, Ag, Al, Cu, Ti, conductive flexible device.
The method of claim 4, wherein

Poisson's ratio of the electrode portion is 0.31 to 0.41, conductive flexible device.
The method of claim 1,

Wherein the oxtic structure has a Poisson's ratio of a negative value.
The method of claim 7, wherein

The oxtic structure is made of an elastic material, conductive flexible device.
The method of claim 1,

An oxtic structure is inserted into the substrate to reduce the Poisson's ratio.