KR20070112657A - Carbon nanotube sensor and method for manufacturing the same - Google Patents

Abstract

A carbon nano-tube sensor and a method for manufacturing the same are provided to use carbon nano-tube paste as a detection member to detect the dielectric constant variation, the variation of the conductivity, the pH, and the humidity. A carbon nano-tube sensor includes electrodes(23), a sensing film(22), and a substrate(21). The sensing film is connected between the electrodes and coated with paste including a carbon nano-tube or nano materials. The substrate is provided with the electrode and the sensing film. The sensing film measures at least one among conductivity, dielectric constant, pH, and humidity of a material adsorbed on the carbon nano-tube or the nano-material. The electrode includes one selected among Al, Pt, Au, and Mo. The electrode includes a carbon nano-tube.

Description

Carbon nanotube sensor and method for manufacturing the same

1 is a perspective view of a sensor using carbon nanotubes according to the present invention.

FIG. 2 is a cross-sectional view taken along line II of FIG. 1.

3 is a schematic perspective view of a sensor using carbon nanotubes according to the present invention;

4 is a cross-sectional view taken along the line II-II of FIG.

5 is a perspective view of another sensor using carbon nanotubes according to the present invention.

6 is an electron micrograph of a carbon nanotube applied to a sensing film of the present invention.

7 is a perspective view of a sensor using carbon nanotubes according to an embodiment of the present invention.

8 is a cross-sectional view taken along the line IV-IV of FIG.

<Description of the symbols for the main parts of the drawings>

11, 21: substrate 12, 22: sensing film

13, 23: electrode 14, 24: lead wire

25: first insulating layer 26: second insulating layer

The present invention relates to a carbon nanotube sensor and a manufacturing method thereof, and more particularly, to an electric conductivity sensor, a dielectric constant change sensor, a pH sensor, a humidity sensor, and the sensors that can be applied using the properties of carbon nanotubes. It relates to a method for manufacturing a carbon nanotube sensor that can be.

Carbon nanotubes are sp ² bonds in which graphite is rolled round, and the surface area per unit area is very wide, so it has excellent adsorption capacity for gas molecules or ions.

The carbon nanotubes have a form such as a single-walled nanotube, a multiwall nanotube, or a nanotube rope structure.

In addition, carbon nanotubes have the characteristics of a conductor or a semiconductor, such as a metal, and has the property of changing electrical conductivity according to the adsorption of gas molecules or ions.

The degree of ion adsorption varies depending on the state of the material absorbed into the carbon nanotubes having good adsorption properties. When the carbon nanotubes are used as the sensing bodies, the carbon nanotubes act as molecular units, thereby adsorbing the carbon nanotubes. It can be used as a device that can measure changes in the electrical properties of materials, pH, humidity, and the like.

However, the application of the sensor for checking the change of the electrical properties, pH, humidity using the carbon nanotubes has a problem that can not guarantee the measurement sensitivity due to the sensitivity or the fluid disturbance effect.

The present invention has been made to solve the above problems, the object is to provide a carbon nanotube sensor that can detect the change in dielectric constant and electrical conductivity of the material, pH, humidity, etc. using the carbon nanotube as a sensor It is for.

The present invention also provides a method for manufacturing a carbon nanotube sensor having excellent measurement sensitivity in manufacturing a conductivity, capacitance, pH, and humidity sensor using the carbon nanotube.

Carbon nanotube sensor according to the present invention for realizing the above object, the electrode is applied to the power, the sensing film is connected between the electrode and the carbon nanotube or a paste containing a nanomaterial is applied, and the electrode, the And a substrate on which a sensing film is mounted, wherein the sensing film measures at least one of electrical conductivity, dielectric constant, pH, and humidity of a material adsorbed on the carbon nanotube or nanomaterial.

In addition, in the carbon nanotube sensor according to the present invention, the electrode is characterized in that it comprises at least one of Al, Pt, Au or Mo.

In addition, in the carbon nanotube sensor according to the present invention, the electrode is characterized in that made of carbon nanotubes.

In addition, in the carbon nanotube sensor according to the present invention, the electrode or the sensing film is characterized in that the branch is branched in the form of a comb.

In addition, in the carbon nanotube sensor according to the present invention, a first insulating layer between the electrode pattern or the substrate, a second insulating layer is included between the electrode pattern and the sensing layer, the insulating layer is a silicon oxide film or nitride film It characterized in that it comprises a.

Meanwhile, in the method of manufacturing a carbon nanotube sensor according to the present invention, after coating a photosensitive agent on a substrate, exposing and etching, patterning a catalyst on the substrate, patterning an electrode on the substrate, and the substrate Covering the electrode thereon, and depositing a carbon nanotube paste mixed with a binder, alpha-tefinol, carbon nanotubes, glass frit.

In addition, in the method of manufacturing a carbon nanotube sensor according to the present invention, the step of patterning the electrode on the substrate is characterized in that it is carried out by CVD, printing, evaporating or sputtering.

In the method of manufacturing a carbon nanotube sensor according to the present invention, the depositing of the carbon nanotube paste may be performed by screen, printing or spraying.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a schematic perspective view for explaining a driving mechanism of the electric conductivity detection sensor using carbon nanotubes according to the present invention, and FIG. 2 is a cross-sectional view taken along the line I-I of FIG.

1 and 2, an electric conductivity detection sensor using carbon nanotubes according to the present invention is an electrode 13 to which power is applied, a carbon nanotube connected between the electrode 13 and sensing a change in electric conductivity or And a sensing layer 12 formed of nanomaterials, a substrate 11 on which the sensing layer 12 and the electrode 13 are mounted.

Here, the substrate 11 of the sensor is made of glass or silicon, and is made of a metal material selected from Al, Pt, Au, Mo.

Carbon nanotubes formed by being deposited and grown on the substrate 11 are connected as bridges between the electrodes 13 as the sensing film 12.

In addition, the electrode 13 is connected to the power supply by the lead wire 14, the lead wire 14 is attached to the electrode 13 to make the entire closed circuit.

The electrode 13 may be made of indium tin oxide (ITO) or a metal, and may be formed of carbon nanotubes in the same manner as the sensing layer 12.

The carbon nanotubes connected as the sensing layer 12 may be deposited using a semiconductor process, a screen printing technique, or a direct growth method.

When the sensing film 12 is formed of carbon nanotubes, when a direct current voltage is applied, the electrical resistance changes according to the amount of change of ions adsorbed on the carbon nanotubes, thereby detecting a change in electrical conductivity. It becomes possible.

On the other hand, as another embodiment of the carbon nanotube sensor according to the present invention with reference to Figure 3, 4 for the description of the dielectric constant change detection sensor using carbon nanotubes.

FIG. 3 is a schematic perspective view for explaining a driving mechanism of the dielectric constant change detection sensor using carbon nanotubes, and FIG. 4 is a cross-sectional view taken along line II-II of FIG.

3 and 4, the dielectric constant change detection sensor using the carbon nanotubes is an electrode 23 to which power is applied, and a paste including carbon nanotubes or nanomaterials connected to the electrode 23 and detecting the dielectric constant change. And a substrate 21 on which the sensing film 22, the sensing film 22, and the electrode 23 are mounted.

Here, glass or silicon is used as the substrate 21 of the sensor.

The electrode 23 may be formed of indium tin oxide (ITO) or a metal, and may be formed of carbon nanotubes in the same manner as the sensing layer 22.

In the dielectric change detection sensor, although carbon nanotubes are deposited and screen printed on the electrode 23 made of metal or ITO, the electrode 23 may be formed of carbon nanotubes.

In addition, referring to Figure 3, in the permittivity change detection sensor, the electrode 22 is more preferably branched in the form of a comb pattern, in this case the carbon nanotubes functioning as the sensing film 22 is the electrode Since it is deposited on (22), the surface area of the capacitive measuring electrode is widened, so that the measurement sensitivity can be greatly improved.

3 and 4, the sensing film may be formed by screen printing carbon nanotubes on the base electrode in the form of a comb electrode using a photolithography process or by using a direct growth method.

When the screen printing method is used to measure the dielectric constant change in the sensor, the width of the comb electrode is 100 μm or less, the electrode gap is 100 μm or less, and in the direct growth method, the distance between the electrodes is preferably 50 μm or less.

 In addition, the carbon nanotubes used in the sensor membrane 22 of the sensor have a small size and ion adsorption and storage functions, and have a high surface area per unit area, so that the sensitivity is high, the response speed is high, and the physical and chemical durability is excellent. There is this.

5 is a perspective view of a dielectric constant change detection sensor of another embodiment using carbon nanotubes according to the present invention, and FIG. 6 is an electron micrograph of carbon nanotubes applied to the sensing film of the present invention.

The sensor illustrated in FIG. 5 covers an electrode pattern 23 to which power is applied, a substrate 21 on which the electrode pattern 23 is formed, and the electrode pattern 23, and a predetermined portion of the entire area of the substrate 21. It includes a sensing film 23 made of carbon nanotubes deposited on.

In the embodiments shown in FIGS. 3 and 4, the carbon nanotubes as the sensing film are deposited only on the electrode 23, but the sensing film shown in FIG. 5 is a paste containing carbon nanotubes or nanomaterials. The electrode patterns 23 are completely covered, and are entirely formed on a predetermined portion of the substrate 21.

In the case of FIG. 5, between the carbon nanotube particles of the sensing film 22, the carbon nanotube particles and the neighboring carbon nanotube particles have a minute capacitance, and as a result, the capacitance value It is possible to ensure a more fine sensitivity that can detect the amount of change of.

Referring to FIGS. 5 and 6, the carbon nanotubes functioning as the sensing film 22 cause a change in electric capacity according to a change amount of ions adsorbed on the carbon nanotubes when a voltage is applied, thereby changing the dielectric constant. Will be detected.

In addition, the detection sensor using the carbon nanotubes as the sensing films 12 and 22 forms a large number of electrodes in a small area by using micromachining technology to manufacture a high-sensitivity sensor, and can make the sensor standard constant.

On the other hand, the electrical conductivity change sensor and the dielectric constant change sensor manufactured by depositing the carbon nanotubes can be manufactured in a new order compared to the existing manufacturing method.

As a first method, a manufacturing process of a carbon nanotube sensor using a semiconductor process technology is performed. First, a lithography step including a photoresist coating, exposure, and etching process is performed on a substrate.

Second, first patterning a catalyst, such as methane gas, on the substrate,

Third, it is preferable that the carbon nanotubes are grown on the substrate after the patterning of the electrodes on the substrate.

As a second method, a manufacturing process of a carbon nanotube sensor using a screen printing technique is performed. First, after performing a lithography step including a photoresist coating, exposure, and etching process on a substrate,

Secondly, a binder and alpha-tefinol are mixed and heated to dissolve,

Third, the carbon nanotubes are first mixed with glass frit and alpha-tefinol, and then mixed with the melted material.

Fourth, after the step of patterning the electrode on the substrate, it is preferable that the step of the step of screen printing and sintering the carbon nanotubes on the substrate.

Here, the step of patterning the electrode on the substrate is preferably performed by CVD, printing, evaporating or sputtering.

In addition, the depositing of the carbon nanotube paste is preferably performed by screen, printing or spraying.

Now, the application of the pH sensor and the humidity sensor in the carbon nanotube sensor according to the present invention will be described.

The acidity of the material adsorbed on the carbon nanotubes changes over time. For example, in the case of engine oils, the acidity gradually decreases as the oil is used.

This means that as acidification proceeds, the material adhered to the carbon nanotubes gradually increases in electrical conductivity while the resistance thereof decreases.

Therefore, in order to detect a change in electrical conductivity as shown in FIG. 1 and FIG. 2, a resistance sensor using carbon nanotubes can be applied as a detection sensor for immediately checking acidity (pH).

On the other hand, the content of water (H ₂ O) contained in the material adsorbed on the carbon nanotubes has a large influence on the capacitance value.

This is because carbon nanotubes react very sensitively to moisture and have very good adsorption properties.

In the sensor, the capacitive sensor measures the capacitance of the dielectric between two electrodes, d is the separation distance, A is the cross-sectional area, ε _r is the relative dielectric constant, and ε _o is the vacuum dielectric constant. Suppose that the capacitance value is

It is determined by C = ε _r ε _o (A / d).

At this time, while the relative dielectric constant of air is 4, the relative dielectric constant of water (H ₂ O) reaches 80.

Therefore, the larger the content of water (H ₂ O) in the material adsorbed on the carbon nanotubes, the larger the capacitance value appears.

Therefore, the capacitive sensor of FIGS. 3 and 5 can be applied as a sensor capable of detecting the content of water (H ₂ O) as a humidity sensor.

7 is an embodiment of a dielectric constant and humidity sensor using carbon nanotubes according to the present invention, and FIG. 8 is a cross-sectional view taken along line IV-IV of FIG. 7.

7 and 8 are formed of carbon nanotube paste covering all of the electrode patterns 23 as well as being entirely coated on a predetermined portion of the substrate 21.

In addition, referring to FIG. 8, an oxide or nitride-based first insulating layer 25 is deposited between the substrate 21 and the electrode pattern 23 to insulate the substrate 21 from the electrode pattern 23. An oxide or nitride-based second insulating layer 26 may be formed between the electrode pattern 23 and the sensing layer 22 to form a sensor for measuring capacitance.

This is possible when the substrate 21 is a semiconductor or conductor such as silicon or a metal thin film.

When the substrate 21 is silicon, the oxide, which is the first insulating layer 25 formed between the substrate 21 and the electrode pattern 23, may be formed of silicon oxide (SiO ₂ ). One insulating layer 25 may be formed of a nitride film.

In FIG. 7 and FIG. 8, forming an oxide or nitride-based second insulating layer 26 between the electrode pattern 23 and the sensing layer 22 is performed by the electrode pattern 23 and the sensing layer 22. This makes the capacitance easier to measure and increases the yield of the sensor.

Referring to FIG. 8, it can be seen that the carbon nanotube particles form the sensing layer 22 and are covered between and over the insulating layer 26 as well as the electrode 23.

6, 7, and 8, the carbon nanotubes functioning as the sensing film 22 cause a change in capacitance according to a change amount of ions adsorbed to the carbon nanotubes when a voltage is applied. The change in permittivity is detected.

As described above, according to the present invention, the carbon nanotube paste is used as a sensor to detect or measure a change in dielectric constant, a change in electrical conductivity, pH, humidity, and the like of the material.

In addition, the manufacturing method of the sensor using the carbon nanotube paste according to the present invention has the advantage that can be easily manufactured while increasing the measurement sensitivity of the sensor.

Claims (8)

An electrode to which power is applied; A sensing film connected between the electrodes and coated with a paste including carbon nanotubes or nanomaterials; And And a substrate on which the electrode and the sensing film are mounted, wherein the sensing film measures at least one of electrical conductivity, dielectric constant, pH, and humidity of the material adsorbed on the carbon nanotube or the nanomaterial. sensor. The method of claim 1, The electrode is a carbon nanotube sensor, characterized in that made of a metal material selected from Al, Pt, Au, Mo. The method of claim 1, The electrode is a carbon nanotube sensor, characterized in that made of carbon nanotubes. The method of claim 1, The electrode or the sensing film is carbon nanotube sensor, characterized in that the branch is branched in the form of a comb. The method of claim 1, And a first insulating layer between the electrode pattern or the substrate, and a second insulating layer between the electrode pattern and the sensing layer, wherein the insulating layer includes a silicon oxide film or a nitride film. After coating the photoresist on the substrate, exposing and etching; Patterning a catalyst on the substrate; Patterning an electrode on the substrate; And Covering the electrode on the substrate and depositing a carbon nanotube paste containing a binder, alpha-tefinol, carbon nanotubes, glass frit. The method of claim 6, Patterning an electrode on the substrate is a method of manufacturing a carbon nanotube sensor, characterized in that carried out by CVD, printing, evaporating or sputtering. The method of claim 6, The depositing of the carbon nanotube paste is carried out by screen, printing or spraying method of manufacturing a carbon nanotube sensor.

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