News Column

Patent Issued for Method for Manufacturing Carbon Nanotube Containing Conductive Micro Wire and Sensor Including the Micro Wire

February 26, 2014



By a News Reporter-Staff News Editor at Journal of Engineering -- According to news reporting originating from Alexandria, Virginia, by VerticalNews journalists, a patent by the inventors Choi, WooSeok (Pohang, KR); Lim, Guenbae (Pohang, KR); An, Tae-Chang (Pohang, KR), filed on October 15, 2008, was published online on February 11, 2014.

The assignee for this patent, patent number 8647490, is Postech Academy-Industry Foundation (Pohang, KR).

Reporters obtained the following quote from the background information supplied by the inventors: "(a) Field of the Invention

"The present invention relates to a method for manufacturing a micro wire. More particular, the present invention relates to a method for manufacturing a micro wire, a sensor including the micro wire, and a method for manufacturing the sensor, having improved production efficiency.

"(b) Description of the Related Art

"Recently, attention to nanotechnology for manufacturing nano-scaled components and devices has increased, and intensive research thereof has been conducted.

"Methods for manufacturing nano-scaled components and devices may be classified to a top-down method and a bottom-up method. In the top-down method, unwanted portions are removed from a film or a mass to manufacture nano-scaled components. In the bottom-up method, small blocks are stocked by self assembly to manufacture nano-scaled components.

"The bottom-up method may be judged to solve problems of the top-down method, and intensive research thereof has been conducted. The bottom-up method is currently applied to manufacture one-dimensional nano-scaled components such as metal or oxide micro wires, and polymer micro/nano wires. Since the one-dimensional nano-scaled components have excellent electrical, thermal, mechanical, optical characteristics, they may be used for various nano-scaled devices such as electrical devices, optical devices, and chemical/bio sensors.

"However, the bottom-up method may be possible only in the research. According to the bottom-up method, a micro wire can be manufactured only when strict conditions are maintained for a long time using expensive equipment. Thus, production efficiency of the micro wire is extremely low. Further, it is difficult to adjust the shape and the location of the micro wire.

"The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art."

In addition to obtaining background information on this patent, VerticalNews editors also obtained the inventors' summary information for this patent: "The present invention has been made in an effort to provide a method for manufacturing a micro wire having advantages of improving production efficiency and adjusting a shape and location of the micro wire.

"Another embodiment of the present invention provides a sensor including a micro wire and a method for manufacturing the sensor having advantages of improving production efficiency and adjusting a shape and location of the micro wire.

"According to an embodiment of the present invention, a method for manufacturing a micro wire includes applying a three-dimensional electric field to a solution for forming a micro wire. The three-dimensional electric field facilitates formation of the micro wire having improved characteristics.

"The method for manufacturing the micro wire may further include providing an electrode assembly including a substrate, and a first electrode and a second electrode formed on the substrate with a space therebetween to which the solution is provided. The space may have a first width and a second width that is smaller than the first width. The three-dimensional electric field is applied to the solution by applying a voltage to the first electrode and the second electrode. Since the space between the first electrode and the second electrode has the first and second widths, a portion where the width of the space is changed exists in the space. The three-dimensional electric field is generated at the portion.

"The width of the space may gradually decrease toward the inside of the substrate. Accordingly, the three-dimensional electric field can be uniformly formed with a large area.

"Each of the first electrode and the second electrode may include an opposing portion. The opposing portion of the first electrode and the opposing portion of the second electrode may face each other while forming the space therebetween. An area where the three-dimensional electric field is applied can be increased by the opposing portions, thereby further facilitating the formation of the micro wire.

"At least one of the opposing portions of the first electrode and the second electrode may have a quadrangular shape. Selectively, at least one of the opposing portions of the first electrode and the second electrode may have a width that gradually decreases toward the other opposing portion.

"In the exemplary embodiment, the shape and location of the micro wire can be adjusted by changing shapes of the first electrode and the second electrode so that the micro wire has excellent characteristics that are appropriate for applications of the micro wire.

"The providing of the electrode assembly may include providing the substrate, forming a groove on the substrate, and forming the first and second electrodes. The first electrode may be formed on at least a first surface of the groove, and the second electrode may be formed on at least a second surface of the groove facing the first surface. The electrode assembly applying the three-dimensional electric field can be easily manufactured by a simple process of forming the groove on the substrate.

"The providing of the electrode assembly may include providing the substrate, forming a first oxidation layer on the substrate, forming a groove on the substrate and the first oxidation layer, removing the first oxidation layer, forming a second oxidation layer on the substrate, and forming the first and second electrodes on the second oxidation layer. The first electrode may be formed at least a portion corresponding to a first surface of the groove, and the second electrode may be formed at least a portion corresponding to a second surface of the groove facing the first surface. The second oxidation layer may protect the first and second electrodes and insulate the substrate from the first and second electrodes.

"The substrate may be a silicon substrate. Accordingly, the groove of a notch shape can be easily formed by the etching characteristic of silicon.

"The three-dimensional electric field may be generated by applying an AC voltage to the first and second electrodes. Thus, the present exemplary embodiment does not need expensive equipment for generating electric signals having complicated waveforms. The shape and the location of the micro wire can be adjusted by changing the frequency of the AC voltage.

"The AC voltage may have frequency of 10 kHz to 10 MHz. The frequency of the AC voltage may be selected to be appropriate for the formation of the micro wire. Thus, the present invention is not limited to the above frequency.

"In the providing of the solution to the space, the solution may be dripped to the space or the electrode assembly may be immersed in the solution. Thus, in the exemplary embodiment, an appropriate method may be used according to the circumstances.

"The micro wire may include a conductive polymer. The conductive polymer has excellent flexibility, chemical stability, and biocompatibility, unlike a metal, and thus can be applicable to various devices.

"The solution may include a solvent, a monomer of the conductive polymer, and a catalyst. The catalyst facilitates polymerization of the monomer of the conductive polymer.

"The catalyst may include a material selected from a group consisting of carbon nanotubes (CNT) and gold nanoparticles. Various materials may be used as the catalyst. For example, the catalyst may be integrated at a predetermined portion and concentrate a current at the portion. Thus, the polymerization of the monomer of the conductive polymer can be facilitated by concentrating the current.

"The monomer of the conductive polymer may include one or more materials selected from a group consisting of pyrrole, aniline, acetylene, thiophene, isothiophene, phenylene, toluidine, azine, acene, azulene, pyridine, and indole.

"The solution may be formed by mixing the catalyst with the solvent, and adding the monomer of the conductive polymer to the solvent mixed with the catalyst. The weight % of the catalyst to the solution may be 0.01 to 5. Preferably, the weight % of the catalyst may be 0.01 to 1.

"The shape and the location of the micro wire can be adjusted by appropriately changing the ratio of the catalyst to the monomer of the conductive polymer.

"The micro wire manufactured by the exemplary embodiment may be used for various nano-scaled or micro-scaled devices in a state in which the micro wire is separated from the electrode assembly or in a state in which the micro wire is connected to the electrode assembly.

"The micro wire may have a diameter of a few nanometers to several hundred micrometers. According to another embodiment of the present invention, a method is provided for manufacturing a sensor, including providing an electrode assembly including a substrate, a first electrode, and a second electrode, providing a solution for forming a micro wire to a space, and applying a three-dimensional electric field to the solution to form a micro wire connected to the first electrode and the second electrode. The first electrode and the second electrode are formed on the substrate, and form the space therebetween. The space has a first width and a second width that is smaller than the first width. The three-dimensional electric field facilitates formation of the micro wire having improved characteristics. Also, since the micro wire of the sensor is connected to the first electrode and the second electrode, the conventional processes in which the micro wire is separately formed and connected to the electrodes can be omitted.

"A width of the space may gradually decrease toward the inside the substrate. Accordingly, the three-dimensional electric field can be uniformly formed with a large area, and the micro wire of the sensor can be stably formed.

"Each of the first electrode and the second electrode may include an opposing portion. The opposing portion of the first electrode and the opposing portion of the second electrode may face each other while forming the space therebetween. An area where the three-dimensional electric field is applied can be increased by the opposing portions, thereby further facilitating the formation of the micro wire.

"At least one of the opposing portions of the first electrode and the second electrode may have a quadrangular shape. Selectively, at least one of the opposing portions of the first electrode and the second electrode may have a width that gradually decreases toward the other opposing portion.

"In the exemplary embodiment, the shape and location of the micro wire can be adjusted by changing shapes of the first electrode and the second electrode so that the micro wire has excellent characteristics that are appropriate for applications of the micro wire.

"The providing the electrode assembly may include providing the substrate, forming a groove on the substrate, and forming the first and second electrodes. The first electrode may be at least formed on a first surface of the groove, and the second electrode may be at least formed on a second surface of the groove facing the first surface. The electrode assembly applying the three-dimensional electric field can be easily manufactured by a simple process of forming the groove on the substrate.

"The providing of the electrode assembly may include providing the substrate, forming a first oxidation layer formed on the substrate, forming a groove on the substrate and the first oxidation layer, removing the first oxidation layer, forming a second oxidation layer on the substrate, and forming the first and second electrodes on the second oxidation layer. The first electrode may be formed at least a portion corresponding to a first surface of the groove, and the second electrode may be formed at least a portion corresponding to a second surface of the groove facing the first surface. The second oxidation layer may protect the first and second electrodes and insulate the substrate from the first and second electrodes.

"The substrate may be a silicon substrate. Accordingly, the groove of a notch shape can be easily formed by the etching characteristic of silicon.

"The three-dimensional electric field may be generated by applying an AC voltage to the first and second electrodes. Thus, the present exemplary embodiment does not need expensive equipment for generating electric signals having complicated waveforms. The shape and the location of the micro wire can be adjusted by changing the frequency of the AC voltage.

"The AC voltage may have frequency of 10 kHz to 10 MHz. The frequency of the AC voltage may be selected to be appropriate for the formation of the micro wire. Thus, the present invention is not limited to the above frequency.

"In the providing of the solution to the space, the solution may be dripped to the space or the electrode assembly may be immersed in the solution. Thus, in the exemplary embodiment, an appropriate method may be used according to the circumstances.

"The micro wire may include a conductive polymer. The conductive polymer has excellent flexibility, chemical stability, and biocompatibility, unlike a metal, and thus can be applicable to various devices.

"The solution may include a solvent, a monomer of the conductive polymer, and a catalyst. The catalyst facilitates polymerization of the monomer of the conductive polymer.

"The catalyst may include a material selected from a group consisting of carbon nanotubes (CNT) and gold nanoparticles. Various materials may be used as the catalyst. For example, the catalyst may be integrated at a predetermined portion, and may concentrate current at the portion. Thus, the polymerization of the monomer of the conductive polymer can be facilitated by concentrating the current.

"The monomer of the conductive polymer may include one or more materials selected from a group consisting of pyrrole, aniline, acetylene, thiophene, isothiophene, phenylene, toluidine, azine, acene, azulene, pyridine, and indole.

"The solution may be formed by mixing the catalyst with the solvent, and adding the monomer of the conductive polymer to the solvent mixed with the catalyst. The weight % of the catalyst to the solution may be 0.01 to 5. Preferably, the weight % of the catalyst may be 0.01 to 1.

"The shape and the location of the micro wire can be adjusted by appropriately changing the ratio of the catalyst to the monomer of the conductive polymer.

"The micro wire may have a diameter of a few nanometers to several hundred micrometers. A sensor according to an exemplary embodiment includes a substrate having a groove, a first electrode and a second electrode formed on the substrate and forming a space therebetween, and a micro wire electrically connecting the first electrode to the second electrode. The space has a first width and a second width that is smaller than the first width.

"The width of the space may gradually decrease toward the inside the substrate. The groove may have a notch shape in cross-section.

"Each of the first electrode and the second electrode may include an opposing portion. The opposing portion of the first electrode and the opposing portion of the second electrode may face each other while forming the space therebetween. At least one of the opposing portions of the first electrode and the second electrode may have a quadrangular shape. Selectively, at least one of the opposing portions of the first electrode and the second electrode may have a width that gradually decreases toward the other opposing portion.

"The substrate may be a silicon substrate. An oxidation layer may be further included between the substrate and the first and second electrodes.

"The micro wire may include a conductive polymer. The micro wire may further include a catalyst. The catalyst may include a material selected from a group consisting of carbon nanotubes (CNT) and gold nanoparticles. The micro wire may have a diameter of a few nanometers to several hundred micrometers."

For more information, see this patent: Choi, WooSeok; Lim, Guenbae; An, Tae-Chang. Method for Manufacturing Carbon Nanotube Containing Conductive Micro Wire and Sensor Including the Micro Wire. U.S. Patent Number 8647490, filed October 15, 2008, and published online on February 11, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=72&u=%2Fnetahtml%2FPTO%2Fsearch-bool.html&r=3590&f=G&l=50&co1=AND&d=PTXT&s1=20140211.PD.&OS=ISD/20140211&RS=ISD/20140211

Keywords for this news article include: Silicon, Fullerenes, Nanoparticle, Nanotechnology, Carbon Nanotubes, Emerging Technologies, Postech Academy-Industry Foundation.

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Source: Journal of Engineering


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