KR100675333B1 - Apparatus for separation of nanotube - Google Patents

Abstract

The present invention relates to a device for separating nanotubes by using electrophoresis, wherein the spaces of the inlet (2a) and the outlet (2b) of the dispersion solution dispersed in a medium in which nanotubes having different properties are dielectric properties ( A structure 20 having a 2) and an electrode 1 forming a non-uniform distribution of an electric field in at least one cross section of the structure such that the nanotube solution passes through the nanotube solution and is subjected to the electrophoretic force. It is easy to construct and high productivity, so that it is possible to separate and collect nanotubes of desired properties in large quantities, and also does not damage nanotubes during the separation process. Suitable.

Nanotube, Separation, Carbon Nanotube

Description

Apparatus for separation of nanotube             

1 is a view showing a two-dimensional nanotube separation apparatus according to an embodiment of the present invention,

2 is a view showing a two-dimensional nanotube separation apparatus according to another embodiment of the present invention,

3 is a view showing a nanotube separation apparatus having a three-dimensional structure according to another embodiment of the present invention;

4 is a view showing a nanotube separation apparatus of a three-dimensional structure according to another embodiment of the present invention,

5 is a view showing a nanotube separation apparatus of a three-dimensional structure according to another embodiment of the present invention,

6 is a view showing an example of the structure of the apparatus of the present invention so that the electric field distribution is significantly different from the inlet side to the outlet side;

7 is a view showing the coating of the nanotube adhesion preventing material on the electrode surface of the device of the present invention.

The present invention relates to the separation of nanotubes, which are difficult to control physically and chemically, in the production process according to metallic properties by electrochemical methods. In particular, the nanotubes are separated according to properties to collect nanotubes having desired properties. It relates to an electrochemical nanotube separation device. With this device, semiconducting nanotubes can be separated from metallic nanotubes or metallic nanotubes from non-metallic nanotubes. Using the separated and collected nanotubes according to their characteristics, the probe of the scanning probe microscope (SPM), the field emission display, the fuel cell, the carbon nanotube field effected transistor (CNT-FET), It can be used in all fields such as data storage, chemical sensor, and bio sensor.

Carbon nanotube (CNT) is a representative material of nanotubes. Since its discovery by Ijima of Japan in the early 1990s, carbon nanotubes (CNT) have been used for research in many fields such as industry because of its outstanding performance. It is actively underway. Carbon nanotubes have the shape of long, thin tubes, single-walled nanotubes (SWNT) with single-walled walls, and multi-walled nanotubes with multi-walled walls (MWNT). ) have. In general, the diameter of SWNT is less than 1nm, MWNT is about 10-100nm, but it is possible to make the diameter smaller or larger depending on the manufacturing conditions and methods. Similarly, the length of the nanotubes is generally about several micrometers in length at the time of manufacture, but recently, cases of developing nanotubes having a length of mm have been reported. These CNTs are lighter than aluminium, have tens of times more strength than ordinary iron, have a greater ability to carry current than copper, and are very resistant to chemical and physical environments. In addition, since the shape of the tube has a large surface area has the advantage that can be attached or fixed a lot of other chemicals have been studied as a fuel cell.

CNTs generally have semiconducting or metallic properties at the time of manufacture. By using these properties, CNTs can be utilized as FETs, Single Electron Transistors (SETs), and nanowires. In addition, it has been developed for the field emission display (Lamp) and the field to produce an electron (Electron) and X-ray (X-ray) by applying a current. And AFM (Atomic Force Microscope) generally uses pyramid-shaped pointed shape at the end of the cantilever, but carbon nanotubes are attached to the end of the pyramid. This is because using a tip with a very high aspect ratio and large elasticity is advantageous for the measurement. Carbon nanotube tips offer performance in the measurement, manipulation, and manufacturing of AFM due to their sharpness, high aspect ratio, high mechanical stiffness, high elasticity, and control of chemical components. It is known to have ideal properties to improve. These nanotube tips are advantageous for measuring long lifetimes, narrow and deep structures, and have a high resolution of less than 1 nm. In addition, this type of probe may be used as a CFM (chemical force microscope) or a bio sensing probe by attaching a specific chemical by manipulating the end of the CNT. In addition, the field of using CNTs is being researched for applications to chemical and biological sensors, composite materials, nano memories, nano computers, and the like.

There are many challenges for these nanotubes to be applied to various industries. One of the very important tasks is to prepare only nanotubes having desired properties by controlling in advance that nanotubes having different properties are made in a mixed state when manufacturing nanotubes. However, no method has yet been developed to make this productive. Therefore, many researchers are attempting to separate nanotubes having desired properties from the mixture of nanotubes having various properties already produced. Recently, Krupke conducted experiments using dielectrophoresis to separate metallic nanotubes from nonmetallic or semiconducting nanotubes on SWNTs and attach them to the desired electrodes. These SWNTs are not completely separated because they are in the form of bundles, but theoretically demonstrated the possibility of using dielectrophoresis to separate metallic nanotubes from semiconducting nanotubes and attach them to the desired electrodes. In addition, several experimental studies have been conducted, but there is no productive method for separating and collecting semiconducting nanotubes and metallic nanotubes required for the actual industry. It is also possible to separate metallic nanotubes from semiconducting nanotubes, but there has never been a way to reverse them. In addition, separation alone is not the only factor. Once separated, they should be able to be easily collected without damage and stored in a form that can be used to build other devices.

It is a main object of the present invention to provide a device for separating nanotubes, which are difficult to control physically and chemically, in production, according to metallic properties by electrochemical methods.

According to the present invention to achieve the above object is provided a nanotube separation apparatus for moving separation of nanotubes having different properties to a desired position by using dielectrophoresis.

More specifically, according to the present invention, a structure having an inlet and an outlet so that the nanotube solution dispersed in a medium in which the nanotube is dielectric may flow, and the nanotube solution is subjected to the electrophoretic force through the structure. A nanotube separation device having an electrode for forming a non-uniform distribution of electric fields in at least one cross section of the structure is provided.

Hereinafter, the present invention will be described in more detail.

The nanotube separation apparatus of the present invention is a medium having dielectric properties in a state in which non-metallic nanotubes including semiconductors and metallic nanotubes are mixed. After the dispersed solution is placed on the electrode, a voltage is applied to at least one cross section of the structure in which the solution is allowed to flow in and out according to negative dielectrophoresis and positive dielectrophoresis in the medium. It is a device that separates nanotubes with different properties by using a distribution of non-uniform electric fields.

Dielectrophoretic force utilized in the present invention is to place a dielectric material placed in a medium in a non-uniform electric field so that the gradient of the electric field is large. It means to make genetic material move. Dielectrophoresis is widely used in biological processes to separate DNA or cells. Recently, it is also used to move or assemble nanoscale materials.

Positive dielectrophoresis refers to a phenomenon in which a material having a larger polarizability than a medium moves toward a high electric field strength. In contrast, in a material having a polarization less than a medium, the electric field moves toward a lower intensity. It is called negative hereditary electrophoresis. The polarization then depends on the frequency of the voltage and the dielectric constant of the solution and the material to form the applied electric field.

Carbon nanotubes usually have very large dielectric constants in the metal type and close to about 1 in the semiconductor type. Therefore, as a method of separating nanotubes, a medium in which nanotubes are spread is applied at a specific frequency by using a dielectric constant larger than a semiconductor type and having a smaller dielectric type than a metal type, so that the electric field strength and the electric field strength are lowest. Two kinds of nanotubes, each with different properties, can be separated by moving toward them.

The medium used is advantageous to prevent chemically or physically damaging the nanotubes, and if a specific molecule or chemical reaction is caused by first modifying the nanotubes, the nanotubes may be treated after necessary chemical treatment. After the separation or depending on the nature of the nanotubes can be subjected to chemical treatment. In general, the electrodes are manufactured in a structure in which the voltage difference can be clearly different so that both positive and negative dielectric phenomena can appear at the same time, but it is desirable to make them easy to be separated and separated from each other by a certain distance or more. Do.

In the device of the present invention, a structure in which a fluid can flow in and out of a solution, and the nanotubes having different properties can be collected and separated into desired areas by having a difference in electric field strength in at least one cross section of the structure. It is desirable to.

Hereinafter, the present invention will be described with reference to the accompanying drawings which illustrate preferred embodiments of the present invention.

The principle of separating nanotubes by the present invention through the device shown in FIG. In FIG. 1, when a voltage is applied to an electrode (hatched portion 1) of the structure 20 as shown in the figure, an electric field is formed in a space portion (not hatched portion: 2) inside the electrodes. In particular, such an electric field has a distribution of a strong electric field (electromagnetic field) in a region where the distance between the electrodes is narrow, and a weak electric field is formed at the central portion of FIG. In this structure, when a nanotube solution dispersed in a medium in which metal nanotubes (M) and semiconductor nanotubes (S) have dielectric properties is surrounded by electrodes, an appropriate frequency is selected to select an electric field. When the metal nanotube (M) is applied to the positive field, the electric field is moved in the strong direction, the semiconductor nanotube (S) is subjected to the negative dielectric, it is moved to the central portion of the weak electric field. Therefore, when the electric field is placed in the reservoir 3 'at the end of the strong side, it is possible to collect only the metallic nanotubes (M) here. Likewise, if the reservoir is placed at the center of the weak electric field, only the semiconductor nanotubes (S) can be collected.

In particular, the type of voltage applied at this time may be provided in the form of alternating current (AC) or a mixture of alternating current and direct current (DC).

Based on this basic principle, various types of devices can be considered to effectively separate large quantities of nanotubes by characteristics at high speed and in large quantities.

For example, in the two-dimensional structure, as shown in FIG. 1, the electrode 1 may be properly disposed so that one kind of nanotube moves outward and the other kind of nanotube moves inward to separate. .

이는 극성이 다른 자석을 가까이하면 자기장의 세기가 커지고, 멀리하면 자기장의 세기가 약해지는 이치이다.
따라서 전기장(전기자기장)은 두 전극의 사이부분(5)에서 가장 큰 값을 가지게 되고, 중앙부분(4)에서는 가장 약한 전기장을 가지게 된다. 따라서 양의 유전영동(Positive dielectrophoresis)을 받는 나노튜브는 바깥쪽으로 이동하게 되고, 음의 유전영동(Netive dielectrophoresis)을 받는 나노튜브는 안쪽으로 이동하게 된다. 이러한 평면 구조물의 경우에 나노튜브가 모이는 위치에 적절한 구멍과 같은 저장소를 제공하면 나노튜브를 분리하는 것이 가능하게 된다. 2 shows another structure 20 using the same principle. When voltage is applied to each of the two sealed rectangular electrodes 1, the intensity B of the electric magnetic field (electric field) is generated according to the right-handed law of framing as follows.

This is because the strength of the magnetic field increases when the magnets of different polarity are close, and the strength of the magnetic field becomes weaker when the magnets are different from each other.
Therefore, the electric field (electromagnetic field) has the largest value in the portion 5 between the two electrodes, and has the weakest electric field in the central portion 4. Thus, nanotubes subjected to positive dielectrophoresis move outward, and nanotubes subjected to negative dielectrophoresis move inward. In the case of such planar structures, it is possible to separate the nanotubes by providing a suitable hole-like reservoir at the location where the nanotubes gather.

In addition, as a further example of the invention, the two-dimensional cross-sectional structure of FIG. 1 may be expanded in three dimensions as shown in FIG. 3 for more effective separation. In the case of the three-dimensional structure of FIG. 3, when the nanotube solution dispersed in the medium having dielectric properties flows into the inlet port 2a of the space part 2 between the electrodes 1, the dispersion solution flows through the dispersion solution passage part. In the process of reaching the outlet 2b, the semiconductor nanotubes are gathered toward the center with a large distance between the electrodes, that is, a weak electric field, and the metal nanotubes have a narrow gap between the electrodes, that is, a strong electric field. They are gathered toward the edge and move. At this time, if the velocity of the moving fluid has a greater force than the nanotubes staying in the gap, the nanotubes in the dispersion solution introduced through the inlet port 2a are dispersed inwards and outwards depending on the property, and then the outlet port 2b direction. Will be moved to. At this time, the length of the tube and the flow rate of the flowing dispersion solution should be designed to separate the nanotubes well.

In this way, the separated nanotubes can be collected at a location where the nanotubes are gathered. For example, as shown in FIG. 3, when the double tube type reservoir 3 is disposed at the end of the outlet port 2b, the metal nanotubes can be collected in the storage portion 3b, and the semiconductor type is stored in the storage portion 3a. Nanotubes can be collected.

It may also be implemented differently from the above of the nanotube separation apparatus of the present invention.

For example, as illustrated in FIG. 4, the nanotube separation device may be configured by making the electrode 1 spirally wound on the outer portion of the tubular structure 20 in a double shape or by arranging the cathode and the anode to cross each other. have. In this way, when the electrode is disposed, a very large electric field is distributed at the intersection of the anode and the cathode. In contrast, the central portion of the tube has a relatively small electric field distribution. In particular, if the arrangement of the electrode to be symmetrical with respect to the center as shown in Figures 3 and 4 it is possible to ensure that the nanotubes subjected to the negative electrophoresis exactly centered.

5 shows a case of the structure 20 in which the electrode 1 is formed asymmetrically. In this electrode, the strength of the electric field in the up and down direction is large and the top is small, so that the nanotubes subjected to positive dielectrophoretic force move downwards according to the electric field intensity, and are subjected to negative dielectric electrophoretic force. The nanotubes move upwards. Therefore, by connecting the means for providing a separate collection place on the top and bottom, respectively, it is possible to separate the nanotubes according to the desired properties.

6 shows that the nanotube dispersion solution enters the inlet 2a of the space 2 and exits the outlet 2b. The difference between the size and the gradient of the electric field is small, and on the outlet side, the difference between the size and the gradient of the electric field inside and outside is greater than the inlet side. FIG. 6 shows that the gap between the electrodes is gradually narrowed toward the outlet rather than the gap between the electrodes at the inlet side at the edge of the space 2 of the structure 20, and the electrodes are moved toward the outlet rather than the gap between the electrodes at the inlet side at the center. It shows the case where the interval of is gradually widened.

Considering this case, once the nanotubes begin to separate in and out according to their properties at the inlet (2a), they become stronger at the edges of the structure space when they go toward the outlet (2b) to increase the separation efficiency. In addition, since the outlet 2b has a larger area of the electric field than the inlet 2a as a whole, the medium or the nanotubes tend to move toward the outlet.

In addition, in the space part 2 of the structure 20, the side of the outlet portion 2b has a larger gradient of the electric field, and the center portion of the outlet portion 2b has a weaker magnitude or gradient of the electric field, and thus receives positive dielectric force. Nanotubes will move towards the edge of the outlet, and nanotubes subjected to negative dielectrophoretic forces will move toward the center of the outlet, resulting in much higher separation rates, and the ability of the nanotubes to move faster from the inlet to the outlet with the solution. have.

In the same manner as in the apparatus of FIG. 5, the gap between the electrodes at the lower part of the space part 2 is gradually narrowed from the inlet port 2a toward the outlet port 2b, and the gap between the electrodes at the upper part of the space part 2. By making it gradually wider from the inlet (2a) toward the outlet (2b) can obtain a similar effect to the above.

FIG. 7 shows that the nanotube adhesion preventing material 2c (hatched portion in the figure) is applied to the surfaces of the electrodes in contact with the nanotube solution. In general, nanotubes are attached on the electrodes by Van der Waals forces or chemical bonds, and as the attached force increases, the nanotubes are not attached by the flowing fluid and remain attached to the electrode surface. Effective separation becomes difficult. Therefore, when nanomaterials do not adhere well on the electrode surface, the nanotubes slide and move on the applied material as the solution moves. The nanotube anti-stick material may be, for example, a hydrophilic material if the nanotubes are hydrophobic, or a hydrophobic material if the nanotubes are hydrophilic. The nanotube adhesion preventing material is preferably selected as a material that does not interfere with the formation of an electric field, such as a polymer-based material.

As described above, the present invention is a device for separating nanotubes prepared by mixing in different dielectric constants according to their properties, and is easy to configure, and has high productivity to separate and collect nanotubes having desired properties in large quantities. In addition, it does not cause any damage to the nanotubes during the separation process, so it is very suitable for application to nanotube-related applications after collection. For example, a scanning probe microscope (SPM) using a nanotube, a field emission display, a fuel cell, a carbon nanotube field effected transistor (CNT-FET), a data storage, a chemical sensor, a bio It is possible to use separated nanotubes in all fields such as sensors.

Claims (5)

The nanotube includes a structure 20 having an inlet and an outlet so that the nanotube solution dispersed in a medium having a dielectric property, and within the structure 20 is subjected to the electrophoretic force as the nanotube solution passes through And an electrode (1) for forming a non-uniform distribution of electric fields in at least one cross section of the structure. The nanotube separation device according to claim 1, wherein the shape of the electrode of the cross section is three-dimensionally formed along the direction in which the solution flows. The device of claim 1, wherein the structure separating the nanotubes comprises one or more nanotube reservoirs capable of recovering at least one property of the nanotubes along the path of travel of the structure. The nanotube separation apparatus according to claim 1, wherein the electrodes at the inlet and the outlet of the nanotube solution are arranged to have a difference in size or gradient of an electric field. The nanotube separation apparatus of claim 1, wherein an anti-adhesion material is further applied to an electrode surface in contact with the nanotube solution so that the nanotubes do not adhere to the electrode surface.

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