WO2019198908A1

WO2019198908A1 - Piezoelectric coaxial fiber and method for manufacturing same

Info

Publication number: WO2019198908A1
Application number: PCT/KR2018/016958
Authority: WO
Inventors: 최승태; 렁틴탐
Original assignee: 중앙대학교 산학협력단
Priority date: 2018-04-10
Filing date: 2018-12-31
Publication date: 2019-10-17
Also published as: KR20190118406A; KR102168312B1

Abstract

The present invention relates to a piezoelectric coaxial fiber and a method for manufacturing same, the piezoelectric coaxial fiber comprising: a core electrode formed as a conductive polymer compound; a piezoelectric polymer layer formed on an outer periphery of the core electrode; an external electrode formed as a conductive polymer compound and positioned on an outer periphery of the piezoelectric polymer layer to have a co-axis with the core electrode and the piezoelectric polymer layer; and a protective layer made of an insulating material and formed on an outer periphery of the external electrode, wherein the piezoelectric polymer layer is configured to allow crystals of a piezoelectric polymer material to be oriented in one direction.

Description

Piezoelectric Coaxial Fiber and Manufacturing Method Thereof

The present invention relates to a piezoelectric element capable of converting external pressure or mechanical vibration into electrical energy, and more particularly, a piezoelectric coaxial fiber having a one-dimensional fiber shape to be applied to wearable computers, smart clothes, and the like, and a method of manufacturing the same. It is about.

Recently, as various portable electronic devices, such as wearable computers and smart wears, such as human clothes or wearables have been developed, the need for a portable power source capable of driving for a long time and minimizing the burden of carrying This is increasing rapidly.

In response to these demands, energy harvesting techniques have been proposed that can convert kinetic energy of people who produce continuous energy into new power sources. In other words, if the power supply using the energy generated from the movement of the human body is a continuous energy supply source that is not limited by time and space, it is due to the problem of the existing power supply medium can be solved.

Among the energy harvesting techniques, many studies have been conducted because piezoelectric materials can be operated based on human body movements such as heart rate, respiration, muscle contraction, and eye movement. Among them, in order to implement a wearable weaving energy harvesting device, a technology in which a piezoelectric energy harvesting device in a three-dimensional or two-dimensional form is transformed into a one-dimensional fiber form has been developed. The energy harvesting device in the form of fibers (hereinafter referred to as 'piezoelectric fibers') can be sufficiently used as a material of cloth because it has an excellent degree of freedom.

In accordance with the trend of technology development of piezoelectric fibers, various researches have been made on technologies for manufacturing piezoelectric fibers of various structures and shapes.

The present invention has been made in view of the above, in providing a piezoelectric coaxial fiber having a coaxial shape, providing a structure of the piezoelectric coaxial fiber exhibiting improved piezoelectric (power generation) performance and mass production of coaxial piezoelectric fibers It is a technical object of the present invention to provide a method for producing a piezoelectric coaxial fiber capable of a continuous process.

According to one embodiment of the invention, the step of manufacturing a preform coated with a piezoelectric polymer material on the outer side of the conductive polymer material; Drawing the preform to form a coaxial fiber body comprising a core electrode and a crystal oriented piezoelectric polymer layer; Forming an external electrode by coating a conductive polymer material on the outer side of the coaxial fiber body; And forming a protective layer by coating an insulating material on an outer surface of the external electrode.

In addition, the piezoelectric polymer material is PVDF, PVDF-TrFE, PVDF-TrFE-CFE. It may comprise any one of PVDF-HFP.

In addition, the core electrode may be formed of a conductive polymer composite containing a low melting point metal. Here, the low melting point metal may include at least one or one or more alloys of indium and tin.

In addition, the drawing of the preform may be made by a hot drawing method.

In addition, by monitoring the diameter of the coaxial fiber body during the drawing, it is possible to control the process conditions based on the monitoring results.

Further, after drawing of the preform, annealing the coaxial fiber body may be further performed.

In addition, before forming the external electrode, a step of polarizing the piezoelectric polymer layer may be further performed by applying a voltage to the coaxial fiber body.

In addition, the polarization treatment may be performed using a corona discharge.

According to another embodiment of the present invention, there is provided a piezoelectric coaxial fiber produced by the method of manufacturing the piezoelectric coaxial fiber.

According to another embodiment of the present invention, the core electrode formed of a conductive polymer composite; A piezoelectric polymer layer formed outside the core electrode; An external electrode formed on the outer side of the piezoelectric polymer layer to have a coaxial with the core electrode and the piezoelectric polymer layer, and formed of a conductive polymer composite; And a protective layer of an insulating material formed on an outer side of the external electrode, wherein the piezoelectric polymer layer is provided so that crystals of the piezoelectric polymer material are oriented in one direction.

In addition, crystals of the piezoelectric polymer material constituting the piezoelectric polymer layer may be oriented in the length direction of the piezoelectric nanofibers.

In addition, crystals of the piezoelectric polymer material constituting the piezoelectric polymer layer may be configured to be polarized in the radial direction of the piezoelectric nanofibers.

In addition, the piezoelectric polymer material is PVDF, PVDF-TrFE, PVDF-TrFE-CFE. It may comprise any one of the PVDF-HFP.

In addition, the core electrode may further include conductive particles of silver or copper in the form of at least one of nano or micro particles, nano wires, nano or micro flakes.

In addition, the external electrode may include at least one of PEDOT: PSS, Ag nanowires, Ag micro / nano particles, carbon black, graphite, graphene, Ag-coated Cu micro or nanoparticles. It may be formed of the included composite material.

According to an embodiment of the present invention, by oriented the crystal of the piezoelectric polymer material in one direction through a drawing process to provide an effect of providing a piezoelectric coaxial fiber of improved piezoelectric performance.

In addition, according to an embodiment of the present invention, by applying the drawing process to the production of the piezoelectric coaxial fiber to further improve the crystallinity of the piezoelectric polymer layer as well as to enable continuous fabrication of the piezoelectric coaxial fiber (piezoelectric coaxial fiber) It has the effect of enabling mass production of.

Furthermore, according to an embodiment of the present invention, the crystallinity of the piezoelectric polymer material may be doubled by performing an annealing process after the drawing process.

In addition, by using a mixture of metal particles having a form of nano or micro particles, nano wires, nano or micro flakes in the conductive polymer composite used in the core electrode, there is an advantage that can have a high electrical conductivity with a small amount have.

In addition, as a subsequent process, polarization through corona discharge is performed prior to coating of the external electrode so that complete piezoelectric properties are expressed, thereby providing a manufacturing method optimized for continuous production of piezoelectric coaxial fibers.

1 is a view showing the internal structure of a piezoelectric coaxial fiber according to an embodiment of the present invention.

Figure 2 is a flow chart showing a method for producing a piezoelectric coaxial fiber according to an embodiment of the present invention.

FIG. 3 is a conceptual view illustrating a drawing process during the manufacturing process of the piezoelectric coaxial fiber shown in FIG. 2.

4 is a diagram schematically showing a crystal orientation form of a piezoelectric polymer material of piezoelectric coaxial fiber.

FIG. 5 is a conceptual diagram schematically showing a polarization treatment step in the manufacturing process of the piezoelectric coaxial fiber shown in FIG. 2. FIG.

6 is a conceptual diagram schematically showing an outer electrode coating and a protective layer coating during the manufacturing process of the piezoelectric coaxial fiber shown in FIG.

7 is a conceptual diagram illustrating an external electrode coating and a protective layer coating method according to another embodiment.

8 is a graph showing the results of X-ray diffraction analysis with or without annealing and polarization treatment in the production of piezoelectric coaxial fibers.

As the invention allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the written description. However, this is not intended to limit the present invention to specific embodiments, it should be understood to include all transformations, equivalents, and substitutes included in the spirit and scope of the present invention. In the following description of the present invention, if it is determined that the detailed description of the related known technology may obscure the gist of the present invention, the detailed description thereof will be omitted.

Terms such as first and second may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprises" or "having" are intended to indicate that there is a feature, number, step, action, component, part, or combination thereof described on the specification, and one or more other features. It is to be understood that the present invention does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, components, or a combination thereof.

Hereinafter, an embodiment of a piezoelectric coaxial fiber and a method of manufacturing the same according to the present invention will be described in detail with reference to the accompanying drawings, in the following description with reference to the accompanying drawings, the same or corresponding components are given the same reference numerals. And duplicate description thereof will be omitted.

Referring to FIG. 1, the piezoelectric coaxial fiber 100 according to the present embodiment includes a core electrode 10, a piezoelectric polymer layer 20, an external electrode 30, and a protective layer 40. The piezoelectric coaxial fiber 100 may have a fiber shape having a diameter of 120 to 140 μm.

The core electrode 10 is disposed at the center of the piezoelectric coaxial fiber and is formed of a conductive polymer composite. The conductive polymer composite is a polymer material in which no yield occurs under bending deformation, and has a structure containing a metal or a metal alloy. The core electrode 10 may have a diameter of 20 to 30 μm.

The piezoelectric polymer layer 20 is made of a piezoelectric polymer material in which polarization occurs due to mechanical deformation such as stretching or compression by an external physical force, and is formed on the outer side of the core electrode 10. Such piezoelectric polymer materials should also not yield under bending deformation, and such materials include polyvinylidene fluoride (PDVF), PVDF-TrFE, PVDF-TrFE-CFE. PVDF-HFP or the like may be used, or a material in which these materials are mixed may be used. In addition, the piezoelectric polymer layer 20 may have a form in which a plurality of layers are stacked, and may have a form in which layers of different materials are alternately stacked. The piezoelectric polymer layer 20 may have a diameter of 60 to 80μm.

According to the present embodiment, the piezoelectric polymer layer 20 is configured such that crystals of the piezoelectric polymer material are oriented in one direction. Specifically, the crystals of the piezoelectric polymer material constituting the piezoelectric polymer layer 20 are oriented in the longitudinal direction of the piezoelectric nanofibers, and the piezoelectric properties may be further improved through such a crystal structure.

In addition, the crystals of the piezoelectric polymer material constituting the piezoelectric polymer layer 20 are configured to be polarized in the radial direction of the piezoelectric nanofibers, thereby securing excellent piezoelectric properties by arranging molecular dipoles in a radial direction.

Crystal orientation and polarization of such piezoelectric polymer materials will be described later in detail.

The external electrode 30 is formed on the outer side of the piezoelectric polymer layer 20 to be coaxial with the core electrode 10 and the piezoelectric polymer layer 20, and is formed of a conductive polymer composite having high elasticity and electrical conductivity. The conductive polymer composite used for the external electrode 30 may also have a structure containing a metal or a metal alloy like the core electrode 10.

The protective layer 40 is formed as an insulating material on the outer side of the external electrode 30 and functions to physically protect the internal structure from the outside. The protective layer 40 may be formed of a polymer material such as polyurethane or polyvinyl alcohol as an insulator having high elasticity, and may use a material that exhibits a heat dissipation function, a water repellency function, and the like, as necessary.

2 is a flowchart illustrating a method of manufacturing a piezoelectric coaxial fiber according to an embodiment of the present invention, and a method of manufacturing the piezoelectric coaxial fiber according to the present embodiment will be described with reference to the following.

First, the piezoelectric polymer material 20 'is coated on the outer side of the conductive polymer material 10' to prepare a preform (S10). The preform A (see FIG. 3) is manufactured to have a diameter of several tens to several hundred times larger than the diameter of the target piezoelectric coaxial fiber.

Next, the preform A is drawn to form a coaxial fiber body B. FIG. FIG. 3 shows a drawing process in the manufacturing process of the piezoelectric coaxial fiber shown in FIG. 2. As the preform A passes through the hole of the mold (not shown), its diameter is reduced to several tens to several hundreds, so that the coaxial fiber body B is formed. Here, the coaxial fiber body B has a configuration in which the piezoelectric polymer layer 20 is formed outside the core electrode 10.

Drawing of the preform (A) may be made by a hot drawing method, for this purpose, a heating furnace (F) may be installed at the front end of the mold. According to this the preform (A) is drawn after heating to a temperature above the melting point of 200 ℃ or more. In this drawing process, the diameter of the coaxial fiber body B output from the metal mold | die can be monitored (S25), and process conditions (for example, drawing speed etc.) can be controlled based on a monitoring result.

According to the present embodiment, a material having a similar melting point may be used as the conductive polymer material 10 'and the piezoelectric polymer material 20' so as to be suitable for the hot drawing process. In the case of the present embodiment, PVDF of a lower price than other materials is used as the piezoelectric polymer material 20 ', and in this case, a conductive polymer composite containing a low melting point metal may be used as the conductive polymer material 10'. For reference, as the low melting point metal used herein, indium, tin, and alloys thereof, and the like, and such low melting point metals such as indium, tin, and alloys thereof may have a size of less than 10 μm.

On the other hand, conductive particles such as silver or copper, in the form of nano or micro particles, nano wires, nano or micro flakes and the like may be contained in the polymer material. The conductive particles may also be in the form of a conductive material coated on the surface of the nano or micro particles (eg, Ag-Coated Cu micro / nano-paticles). As such, when metal particles such as spherical particles, wires, and flakes are mixed and used, a conductive polymer composite having high electrical conductivity even with a small content can be made, which makes it more suitable for a hot drawing process.

According to the drawing process, the crystals of the piezoelectric polymer material constituting the piezoelectric polymer layer 20 are oriented along the length direction of the piezoelectric coaxial fiber, and FIG. 4 schematically shows the crystal orientation of the piezoelectric polymer material (PVDF). have. According to the drawing process, as shown in FIG. 4, molecular chains of PVDF are lined along the length direction of the piezoelectric coaxial fiber, and through such structural features, piezoelectric properties may be improved. For example, when PDVF is used at a lower price than the PVDF-TrFE, the crystallinity is increased through the drawing process, thereby achieving piezoelectric properties equivalent to those using PVDF-TrFE.

Referring back to FIG. 2, annealing or sintering is performed on the coaxial fiber body B formed through the drawing process S20 (S30). Annealing or sintering refers to a process of heating the coaxial fiber body (B) at a predetermined temperature (for example, 140 ° C.) and then cooling it, through which the crystallinity of the piezoelectric polymer layer 20 can be further improved, and the metal The junction between the particles can be formed to further increase the electrical conductivity. Here, it will be preferable to use photosintering so that only the metal particles can be instantaneously heated up without melting the piezoelectric polymer material.

As a next step, the piezoelectric polymer layer 20 is polarized by applying a voltage to the coaxial fiber body B (S40). The piezoelectric properties of coaxial piezoelectric fibers are highly dependent on the degree of dipole arrangement. In the case of disordered dipole arrangement, piezoelectric properties do not occur, and perfect piezoelectric properties are expressed through a polarization process in which dipoles are arranged in the same direction. do.

Corona discharge may be used for the polarization treatment of the fiber structure manufactured through the continuous process as in the present embodiment, and FIG. 5 schematically illustrates the polarization treatment process through the corona discharge.

Referring to FIG. 5, one (or more) needle tip functions as an electrode for voltage application, the needle tip being spaced a certain distance (several millimeters) from the surface of the coaxial fiber body (B). The ground electrode is connected to the core electrode 10. When a high voltage is applied, corona discharge occurs from the needle tip. Accordingly, the piezoelectric polymer material crystals are polarized in the radial direction of the coaxial fiber body 20. The polarization treatment through corona discharge may be performed a plurality of times along the outer circumference of the coaxial fiber body B, or may be performed by arranging a plurality of needle tips along the outer circumference of the coaxial fiber body B.

On the other hand, the annealing process (S30) described above is an additional or optional process for further improving the piezoelectric properties of the piezoelectric coaxial fiber 100, the polarization treatment step (S40), performing only one of these processes or It would also be possible to proceed to the next step without carrying out the process.

Referring back to FIG. 2, as an next step, an external electrode 30 is formed outside the coaxial fiber body B (S50). This may be formed by coating a conductive polymer material on the outer side of the coaxial fiber body (B). As the material of the external electrode 30, among PEDOT: PSS, Ag nanowires, Ag micro / nano particles, Carbon Black, Graphite, Graphene, Ag-coated Cu micro / nano particles, Composite materials containing one or more may be used.

Next, an insulating material is coated on the outer side of the external electrode 30 to form the protective layer 40 (S60). Coating process (S50) of the external electrode 30 and the coating process (S60) of the protective layer 40 can be performed using a single coating apparatus 200, Figure 6 is an external electrode coating and protective layer coating using the same The process is shown schematically.

Referring to FIG. 6, the coating apparatus 200 includes two material chambers partitioned from each other, and is configured such that the conductive polymer material and the insulating material supplied into each chamber are sequentially coated on the outer surface of the coaxial fiber body B. have.

Meanwhile, in addition to the above method, the external electrode 30 and the protective layer 40 may be coated using the dip coating apparatus 310, the thermal tube 320, and the die coating apparatus 330 as shown in FIG. 7. It is possible. According to this, after the external electrode 30 is formed on the outer side of the coaxial fiber body B using the dip coating apparatus 310, the external electrode 30 is thermally cured using a heat tube, and then die coating. The device 330 is used to form the protective layer 40 outside the external electrode 30.

This method is useful when a composite material containing conductive particles such as PEDOT: PSS and Ag nanowires is used as the material of the external electrode 330. The conductive particles such as PEDOT: PSS and Ag nanowires are mixed in a solvent. This is because it is possible to thermally harden the solvent by volatilizing the solvent in the heat tube 320 after the dip coating. In FIG. 7, the protective layer 40 is coated by a die coating method, but the protective layer 40 may also be coated using a dip coating method.

When the coating of the external electrode 30 and the protective layer 40 is completed, all the layers of the piezoelectric coaxial fiber 100 are formed, after which the piezoelectric coaxial fiber 100 is cured (S70) to complete the manufacturing process. By monitoring the diameter of the piezoelectric coaxial fiber 100, the curing step (S70) (S75) can be controlled to the process conditions based on the monitoring results.

8 is a graph showing the results of X-ray diffraction analysis with or without annealing and polarization treatment when manufacturing piezoelectric coaxial fibers.

In general, PVDF-based polymers have α-, β-, γ-, and δ-crystals as crystal structures. Among them, the crystals most affecting piezoelectricity are β-crystals in which dipoles are arranged to one side.

Referring to the graph of FIG. 8, it can be seen that in bulk PVDF, the material exhibits an almost amorphous state, and the peaks are blunt and wide. It can be seen that for coaxial fibers that are not annealed after the drawing process, the peaks are clear and sharp in comparison.

In the case of coaxial fibers subjected to the annealing process, almost all of the nonpolar α-crystals were converted into β-crystals, and in the case of polarized piezoelectric coaxial fibers after annealing, the conversion into full β-crystals It is confirmed that it is done.

Although the foregoing has been described with reference to specific embodiments of the present invention, those skilled in the art may vary the present invention without departing from the spirit and scope of the present invention as set forth in the claims below. It will be understood that modifications and changes can be made.

Claims

Manufacturing a preform coated with a piezoelectric polymer material on an outer surface of the conductive polymer material;

Drawing the preform to form a coaxial fiber body comprising a core electrode and a crystal oriented piezoelectric polymer layer;

Forming an external electrode by coating a conductive polymer material on the outer side of the coaxial fiber body; And

A method of manufacturing a piezoelectric coaxial fiber comprising coating an insulating material on the outside of the external electrode to form a protective layer.
The method of claim 1,

The piezoelectric polymer material is PVDF, PVDF-TrFE, PVDF-TrFE-CFE. A method for producing a piezoelectric coaxial fiber comprising any one of PVDF-HFP.
The method of claim 1,

The core electrode is a piezoelectric coaxial fiber manufacturing method, characterized in that formed of a conductive polymer composite containing a low melting point metal.
The method of claim 3,

The low melting point metal is at least one of indium, tin or a method of producing a piezoelectric coaxial fiber, characterized in that at least one alloy.
The method of claim 1,

The drawing of the preform is a method of producing a piezoelectric coaxial fiber, characterized in that the hot drawing method.
The method of claim 1,

The method of manufacturing a piezoelectric coaxial fiber, characterized in that for monitoring the diameter of the coaxial fiber body, the process conditions are controlled based on the monitoring result.
The method of claim 1,

After drawing the preform, further comprising annealing the coaxial fiber body.
The method of claim 1,

And forming a polarization treatment of the piezoelectric polymer layer by applying a voltage to the coaxial fiber body before forming the external electrode.
The method of claim 8,

The polarization treatment is a method of producing a piezoelectric coaxial fiber, characterized in that using a corona discharge (corona discharge).
A piezoelectric coaxial fiber produced by the manufacturing method according to any one of claims 1 to 9.
A core electrode formed of a conductive polymer composite;

A piezoelectric polymer layer formed on the periphery of the core electrode;

An external electrode formed on the outer side of the piezoelectric polymer layer to have a coaxial with the core electrode and the piezoelectric polymer layer, and formed of a conductive polymer composite; And

It includes a protective layer of an insulating material formed on the outer periphery of the external electrode,

The piezoelectric polymer layer is a piezoelectric coaxial fiber, characterized in that the crystals of the piezoelectric polymer material is configured to be oriented in one direction.
The method of claim 11,

Crystals of the piezoelectric polymer material constituting the piezoelectric polymer layer is oriented in the longitudinal direction of the piezoelectric nanofibers.
The method of claim 11,

Crystals of the piezoelectric polymer material constituting the piezoelectric polymer layer is configured to be polarized in the radial direction of the piezoelectric nanofibers.
The method of claim 11,

The piezoelectric polymer material is PVDF, PVDF-TrFE, PVDF-TrFE-CFE. Piezoelectric coaxial fiber comprising any one of PVDF-HFP.
The method of claim 11,

The core electrode is a piezoelectric coaxial fiber, characterized in that formed of a conductive polymer composite containing a low melting point metal.
The method of claim 15,

The low melting point metal is at least one of the indium, tin or piezoelectric coaxial fiber, characterized in that it comprises at least one alloy.
The method of claim 11, wherein the core electrode,

A piezoelectric coaxial fiber further comprising conductive particles of silver or copper having in the form of nano or micro particles, nano wires, nano or micro flakes.
The method of claim 11,

The external electrode may include one or more of PEDOT: PSS, Ag nanowires, Ag micro / nanoparticles, carbon black, graphite, graphene, Ag-coated Cu micro or nanoparticles. Piezoelectric coaxial fiber, characterized in that formed from a composite material.