KR20140008631A - Dry type ionic polymer actuator and method for fabricating the same - Google Patents

Abstract

The present invention relates to a dry ionic polymer actuator, to which graphene buckypaper electrodes with low moisture permeability and hydrophobic properties are applied, and a manufacturing method thereof. According to the present invention, the problem of the reduced performance due to a long time operation of the ionic polymer actuator can be solved by using a graphene electrode which does not have cracks compared with a traditional platinum electrode and has high electrical conductivity and hydrophobic properties as an electrode of the ionic polymer actuator. Also, manufacturing costs and time of the ionic polymer actuator can be reduced by using the graphene electrode which uses low-cost graphite. [Reference numerals] (AA) Start; (BB) End; (S101) Generate oxide graphite; (S102) Obtain oxide graphene; (S103) Generate oxide graphene buckypaper; (S104) Generating graphene buckypaper; (S105) Graphene buckypaper & ionic polymer hot pressing

Description

Dry type ionic polymer actuator and method for manufacturing the same {Dry type ionic polymer actuator and method for fabricating the same}

The present invention relates to an ionic polymer actuator and a manufacturing method thereof, and more particularly, to a dry ionic polymer actuator using a graphene bucky paper electrode having a low water permeability and hydrophobic characteristics, and a manufacturing method thereof.

Electroactive polymer (EAP) whose volume or length is changed by external electrical stimulation is lighter and easier to process than piezoelectric material (PZT) or shape memory alloy (SMA). It has biomimetic and biocompatible and low power. Therefore, it has been used as an electroactive material, and recently, research on ionic polymer metal composite (IPMC) among mechanical polymers has been actively conducted.

Conventional ionic polymer metal composite (IPMC) is a composite of a fluorine-substituted ionic polymer membrane and a conductive metal is composed of a metal electrode coated on both sides of the nafion (nafion) membrane.

When an electric field is applied to the metal electrode, the membrane partially expands and bends as a result of ion movement inside the membrane, and the degree of deformation is adjustable according to voltage or frequency applied to electrodes located on both surfaces of the membrane.

In addition, the ionic polymer metal composite (IPMC) has a fast response even at a relatively low voltage of 10V or less, and the deformation is large, thus enabling low power driving and having a fast response at high frequencies.

In addition, it has the advantage that it can be utilized as an actuator material that can be driven in vivo by including a polymer material having excellent softness and excellent biocompatibility with excellent moisture content.

By using the ionic polymer metal composite (IPMC) having such advantages can be designed a light and flexible small actuator, it can be applied to a variety of applications, such as artificial muscles and micro robots and micro pumps to mimic the biological function in the medical field.

However, in the conventional ionic polymer metal composite (IPMC), the electroless plating process used for electrode stacking is performed through a complicated process such as pretreatment, ion adsorption process, and reduction process, which requires considerable manufacturing time and ensures electrode performance reproducibility. There is difficulty. In addition, there is a problem of the surface characteristics of the platinum electrode generated through a plurality of cracks.

The problem to be solved by the embodiment of the present invention by using a graphene bucky paper that improves the surface electrical conductivity and hydrophobic properties through the reduction process as an electrode to prevent performance degradation during long time operation, and to reduce the manufacturing time and manufacturing cost A dry ionic polymer actuator and a method for producing the dry ionic polymer actuator are provided.

In order to solve the above problems, the present invention, by producing a graphite oxide synthesized from the starting material (graphite) through the Hummers' method (hummer's method), and oxidized from the graphite oxide by using ultrasonic grinding and centrifugation Providing graphene, preparing a graphene oxide buckypaper using vacuum filtration, reducing the graphene oxide bucky paper to produce graphene bucky paper, and the graphene bucky In one embodiment, a method of manufacturing a dry ionic polymer actuator comprising providing paper as a pair of electrodes and positioning and thermocompressing an ionic polymer between the pair of electrodes is provided.

Here, the step of providing the graphene oxide, the graphene oxide is produced through an external energy source such as heat or microwave.

In addition, the step of producing the graphene bucky paper using the reducing agent such as hydrogen iodide (hydrogen iodide, HI) acid and hydrazine and sodium borohydride or the oxidation through a heat treatment of 500 ℃ or more in a reducing gas environment such as argon and hydrogen Reduce graphene bucky paper.

In addition, the ionic polymer includes a cation and a water molecule or an ionic liquid.

In addition, the ionic polymer is an ionic polymer such as Nafion and sulfonated polyimide (SPI), porous polymer such as polyurethane and polydimethylsiloxane (PDMS), and chitosan and cellulose Biopolymers or combinations thereof.

According to an embodiment of the present invention by using a graphene electrode having a high electrical conductivity, low moisture permeability and hydrophobic characteristics as the electrode of the ionic polymer actuator, which does not have the same crack as the conventional platinum electrode, it occurs during long time operation of the ionic polymer actuator. This can solve the problem of poor performance. In addition, by using a graphene electrode made from low-cost graphite, it is possible to reduce the manufacturing time and manufacturing cost of the ionic polymer actuator, and to implement a dry type ionic polymer actuator.

1 is an ionic polymer graphene composite (IPGC) actuator and an ionic polymer metal composite (IPMC) actuator according to an embodiment of the present invention.
2 is a flowchart sequentially illustrating a manufacturing process of graphene bucky paper according to an embodiment of the present invention.
3 is a scanning electron microscopy (SEM) image of the surface of graphene bucky paper according to an embodiment of the present invention.
4 is a thickness change image of the graphene bucky paper according to an embodiment of the present invention.
FIG. 5 is a cross-sectional scanning electron microscope (SEM) image and a transmission electron microscopy (TEM) image of graphene bucky paper according to an embodiment of the present invention.
6 is a chemical structure of graphene oxide and reduced graphene oxide according to an embodiment of the present invention.
7 is a Raman spectrum and XPS spectrum results of graphene bucky paper according to an embodiment of the present invention.
8 is XPS C1s spectrum results of graphene oxide and reduced graphene oxide according to an embodiment of the present invention.
9 is a contact angle comparison result of the graphene bucky paper before and after the pressing technique according to an embodiment of the present invention.
10 is a time-dependent performance characteristics of the ionic polymer graphene composite (IPGC) actuator and the ionic polymer metal composite (IPMC) actuator according to an embodiment of the present invention.
11 is a harmonic response characteristic of the ionic polymer graphene composite (IPGC) actuator and the ionic polymer metal composite (IPMC) actuator after drying the specimen according to an embodiment of the present invention.

Hereinafter, 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 carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

Means that a particular feature, region, integer, step, operation, element and / or component is specified and that the presence or absence of other features, regions, integers, steps, operations, elements, and / It does not exclude addition.

1 is an ionic polymer graphene composite (IPGC) actuator and an ionic polymer metal composite (IPMC) actuator according to an embodiment of the present invention.

In FIG. 1, (a) shows a phenomenon in which an ionic polymer graphene composite (IPGC) actuator having a hydrophobic electrode floats in water, and (b) shows ionic polymer graphene composite (IPGC) floating in water and water. Sitting ionic polymer metal composite (IPMC) actuators are shown simultaneously.

The ionic polymer graphene composite (IPGC) can be utilized not only in a dry actuator having a hydrophobic graphene electrode, but also in an actuator that is not wet with water, and can be applied to various fields as well as an active biomedical apparatus.

2 is a flowchart sequentially illustrating a manufacturing process of graphene bucky paper according to an embodiment of the present invention.

First, graphite is used as a starting material to produce graphite oxide through the Hummers method (Summer's method) (S101).

In this case, the method of producing the graphite oxide may be performed using an external energy source such as heat or microwave.

Subsequently, graphene oxide is obtained from the graphite oxide using ultrasonic grinding and centrifugation (S102), and graphene oxide bucky paper is produced using vacuum filtration (S103).

Then, the graphene bucky paper is produced by reducing the graphene oxide bucky paper using hydrogen iodide (HI) acid as a reducing agent (S104).

Lastly, the graphene bucky paper is used as a pair of electrodes, and an ionic polymer is placed between the pair of electrodes to be thermocompressed (S105).

As a result of the thermocompression bonding, a ionic polymer graphene composite (IPGC) actuator having a sandwich structure such as graphene bucky paper-ionic polymer-graphene bucky paper is produced.

3 is a scanning electron microscopy (SEM) image of the surface of graphene bucky paper according to an embodiment of the present invention.

At this time, the thickness and quality of the graphene bucky paper is determined according to the size of the graphene oxide nanosheets, the concentration of the graphene oxide solution and the amount of the graphene oxide filtered from the vacuum filter used for electrode production.

Accordingly, the graphene bucky paper having a smooth surface and a predetermined thickness may be generated according to the concentration of the graphene oxide solution and the amount of the graphene oxide filtered in the vacuum filter used for fabricating the electrode.

Figure 4 shows the thickness change image of the graphene bucky paper according to an embodiment of the present invention, it can be seen that the graphene bucky paper is generated to have a variety of thickness.

Figure 5 (a) shows the cross-sectional characteristics of the graphene bucky paper through a scanning electron microscope (SEM) image analysis, (b) and (c) is a layered layer of graphene nanosheets used in the production of graphene bucky paper Structure and crystallinity are shown through transmission electron microscopy (TEM) image analysis.

In Figure 5 (a) shows that the cross section of the graphene bucky paper has a porous interlayer structure, through which it can be confirmed that the graphene bucky paper has a low moisture permeability and can float on water.

In addition, it can be confirmed that the graphene synthesized through (b) of FIG. 5 has a structure having 4 to 5 layers, and that the graphene synthesized through (c) of FIG. 5 has a single crystal structure. have.

FIG. 6 illustrates chemical structures of graphene oxide and reduced graphene oxide according to an embodiment of the present invention.

Looking at the chemical structure of the graphene oxide in Figure 6, it consists of a plurality of hydroxyl groups (epoxy group), epoxy group (epoxy group) and carboxyl group (carboxyl group), through such functional groups the graphene oxide High oxygen content and hydrophilic character.

This can be confirmed through the XPS spectrum shown in FIG.

The reduced graphene oxide has a plurality of oxygen is reduced to show a low oxygen content, thereby increasing the electrical conductivity of the surface.

Referring to the Raman spectrum of FIG. 7A, defects generated during oxidation using a chemical method (Humers method) and restoration of sp2 carbon by a reduction process using hydrogen iodide (HI) acid are shown. It can be seen that this increases the 2D peak.

This means that the purity and quality of the graphene nanosheets as shown in (b) and (c) as the high crystallinity and functional groups of the graphene nanosheets are reduced.

In addition, the D peak is due to an unaligned property, and in particular, the increase of the D peak in graphene bucky paper is interpreted as a result of excessive oxidation process.

Looking at the C1s peak of the graphene oxide in Figure 8 (a) and (b), it can be seen that the C-O peak is reduced and the C-C peak is more sharp through the reduction process.

Table 1 below shows the comparison of physical properties between graphene oxide bucky paper and graphene bucky paper.

Sample Atomic Composition Ratio (C: O) Electrical conductivity thickness Contact Angle (°) Graphene Oxide Bucky Paper 72.5: 27.5 - <1 μm 70 (hydrophilic) Graphene Bucky Paper 88.5: 11.5 > 500S / cm <1 μm 97 (hydrophobic)

In Table 1, it can be seen that graphene oxide has a high oxygen content by various functional groups including oxygen, and thus the electrical conductivity is low enough to be impossible to measure and has a low contact angle due to hydrophilicity.

On the other hand, graphene bucky paper has a reduced oxygen content through the reduction process by hydrogen iodide (hydrogen iodide, HI) acid, and it can be seen that it has a high electrical conductivity and a high contact angle by the restoring property of sp2 bond.

This means that the surface properties of graphene bucky paper changed from hydrophilic to hydrophobic.

9 is a sandwich structure of graphene bucky paper-ionic polymer-graphene bucky paper by hot pressing near the glass transition temperature (~ 100 ° C.) of nafion used as an ionic polymer. The contact angle measurement results before and after thermocompression bonding of the ionic polymer graphene composite (IPGC) having a.

In FIG. 9, it can be seen that there is almost no change in the contact angle before and after thermocompression, and thus, even after the ionic polymer graphene composite (IPGC) actuator is manufactured after thermocompression, the electrical conductivity of the graphene bucky paper electrode ( > 500 S / cm) is maintained, it can be seen that the hydrophobic properties for water droplets are also maintained.

In addition, it can be seen that the thermocompression process does not significantly affect the electrodes of the graphene bucky paper.

Figure 10 illustrates the performance over time of the ionic polymer graphene composite (IPGC) actuator and the conventional ionic polymer metal composite (IPMC) actuator according to an embodiment of the present invention.

Referring to Figure 10, the ionic polymer graphene composite (IPGC) actuator according to an embodiment of the present invention shows that the operating performance in the air is maintained over time.

On the other hand, it can be seen that the ionic polymer metal composite (IPMC) actuator deteriorates over time in the air.

This is due to the crack shape of the surface of the platinum electrode of the ionic polymer metal composite (IPMC) actuator, and due to the crack shape, a large amount of water flows out of the ionic polymer during large deformation operation of the ionic polymer metal composite (IPMC) actuator. As operating time increases, performance decreases.

However, the ionic polymer graphene composite (IPGC) actuator according to an embodiment of the present invention maintains long-term operation performance by the hydrophobicity and water leakage prevention characteristics of the graphene bucky paper electrode obtained by reducing the graphene oxide bucky paper. Can be.

Table 2 below is an experiment to check whether the ionic polymer graphene composite (IPGC) actuator and the conventional ionic polymer metal composite (IPMC) actuator according to an embodiment of the present invention after drying for 48 hours at 60 ℃ The result is.

Sample Before drying after drying After operation Ionic Polymer Graphene Composite (IPGC) 0.045 g 0.045 g 0.045 g Ionic Polymer Metal Composites (IPMC) 0.078 g 0.069 g 0.069 g

In Table 2, in the case of the ionic polymer graphene composite (IPGC) according to an embodiment of the present invention, the weight change does not occur before and after drying, and almost no water leakage occurs due to graphene bucky paper electrode characteristics. Can be confirmed.

However, in the case of the ionic polymer metal composite (IPMC), the weight change occurred before and after drying, indicating that a considerable amount of water leakage occurred.

For this reason, the conventional ionic polymer metal composite (IPMC) actuator after the operation is hardly operated and the ionic polymer graphene composite (IPGC) according to an embodiment of the present invention is dry because it shows an excellent harmonic response characteristics as shown in FIG. It can be confirmed that it is applicable to the type actuator.

While the present invention has been particularly shown and described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. Belongs.

Claims (6)

Producing a synthetic graphite oxide from graphite, which is a starting material, through a Hummer's method,
Providing graphene oxide from the graphite oxide using ultrasonic grinding and centrifugation,
Preparing a graphene oxide buckypaper using vacuum filtration,
Reducing the graphene oxide bucky paper to produce graphene bucky paper,
Providing the graphene bucky paper as a pair of electrodes, and
Positioning and thermocompressing the ionic polymer between the pair of electrodes. The method of claim 1,
Providing the graphene oxide,
A method for producing a dry ionic polymer actuator for producing the graphene oxide through an external energy source such as heat or microwave. The method of claim 1,
Generating the graphene bucky paper,
Dry ionic polymer that reduces the graphene oxide bucky paper by using a reducing agent such as hydrogen iodide (HI) acid, hydrazine and sodium borohydride, or by heat treatment over 500 ° C. in a reducing gas environment such as argon and hydrogen. Method of manufacturing the actuator. The method of claim 1,
The ionic polymer is a method of producing a dry ionic polymer actuator comprising a cation and a water molecule or an ionic liquid. The method of claim 1,
The ionic polymers include ionic polymers such as Nafion and sulfonated polyimide (SPI), porous polymers such as polyurethane and polydimethylsiloxane (PDMS), and biopolymers based on chitosan and cellulose. Or a combination thereof. A dry type ionic polymer actuator prepared according to the method for producing a dry type ionic polymer actuator according to any one of claims 1 to 5.

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