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Systems and methods of manufacturing nanotube structuresRelated Patent Categories: Adhesive Bonding And Miscellaneous Chemical Manufacture, Methods, Surface Bonding And/or Assembly Therefor, With Permanent Bending Or Reshaping Or Surface Deformation Of Self Sustaining Lamina, Bending Of One Piece Blank And Joining Edges To Form Article, Hollow Cylinder ArticleSystems and methods of manufacturing nanotube structures description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070163702, Systems and methods of manufacturing nanotube structures. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application claims the benefit of the filing date of U.S. patent application Ser. No. 10/950,793, filed 28 Sep. 2004, U.S. Provisional Patent Application No. 60/577,678, filed 7 Jun. 2004, and U.S. Provisional Patent Application No. 60/565,610, filed on 27 Apr. 2004, the entire disclosures of all of which are hereby incorporated herein in their entireties by reference. BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates to nanotube manufacturing, and more specifically, to nanotubes and systems and methods for the formation and/or manufacture of nanotubes and nanotube structures. [0004] 2. Related Art [0005] Carbon nanotubes are tubular carbonaceous structures with mechanical, electrical, and chemical properties that make them potentially useful in many fields, including electronic, mechanical, and medical applications. For example, they exhibit exceptional strength, primarily due to the presence of strong sp.sup.2 bonds between the carbon atoms making up the tubes. Furthermore, they exhibit interesting electrical properties, such as the high conductivity of some tubes due to the alignment of carbon atoms along the long axis of the tubes. They likewise exhibit thermal properties that make them attractive for various uses, such as in heat sinks for computer chips. In addition, because they are hollow, they can hold, transport, and ultimately release substances. This property makes them quite useful for medical applications. Numerous studies are being conducted to identify other unique and useful properties of these small structures. [0006] A nanotube is a cylindrical carbon lattice having a basic lattice structure of a fullerene. Most nanotubes are capped at one or both ends by a half fullerene molecule. Nanotubes are characterized by having external diameters of one nanometer (1 nm) to only a few (e.g., 5-10) or tens (e.g., 50) nanometers. While many nanotubes are only a few times longer than they are wide, some have been fabricated having a length of millions of times greater than their width. Nanotubes can align themselves into rope-like structures, permitting fabrication of long wires of exceptional strength, yet relatively light weight. [0007] Nanotubes have been fabricated in two different types of basic structures: single-walled nanotubes (SWNT), and multi-walled nanotubes (MWNT). As their names imply, SWNTs are tubes having a single wall encasing an internal volume, whereas MWNTs are tubes in which a single internal volume is encased by multiple tubular wall structures arranged as nested cylinders. Due to their different structures, and due to the differences in the ease by which they can be produced, SWNTs and MWNTs are being targeted and used for different purposes (although many uses overlap). [0008] Currently, there are various known processes and methods for the production or manufacture of carbon nanotubes. These processes can include Arc Discharge, Laser Ablation, and Chemical Vapor Deposition. In the Arc Discharge method, a carbon-containing vapor is created by an arc discharge between two carbon electrodes, and carbon nanotubes self-assemble from the vapor. Unfortunately, this method results in high levels of impurities that are expensive to remove, if at all possible. In the Laser Ablation method, a high-energy laser beam impinges on a volume of carbon-containing feedstock gas. While the nanotubes produced by Laser Ablation are cleaner than those produced by Arc Discharge, the yield is significantly lower. In the Chemical Vapor Deposition method, carbon-containing gas is exposed to heated reactive metal, which causes formation of nanotubes on the heated surface of the metal. Chemical Vapor Deposition can be used on a large scale, but often and uncontrollably produces a mixture of SWNTs and MWNTs having a wide range of diameters, the SWNTs invariably being of poor quality. Furthermore, it requires purification of the nanotubes from the soot and metals present in the reaction. [0009] U.S. Pat. No. 6,455,021 discloses an arc discharge method, whereby a flow of a precursor gas is exposed to a plasma discharge at very high temperatures in the production carbon nanotubes. The nanotubes generated through this protocol, however, can include a high volume of contaminants. [0010] U.S. Pat. No. 6,331,690 discloses a laser ablation method in connection with the production of nanotubes, whereby a high-energy laser is focused at a carbon target. This method can produce nanotubes with relatively fewer contaminants than the arc discharge method, but the production rate can be low. The laser ablation method can also be capital-intensive. [0011] U.S. Pat. No. 6,689,674 discloses of a Chemical Vapor Deposition (CVD) method for the production of nanotubes, whereby a flow of precursor gas is heated and directed over a reactive metal surface. The use of CVD in the production of carbon nanotubes can generate a good yield and relatively fewer contaminants. However, the carbon nanotubes produced can have a number of defects. [0012] Due to the complexity of the fullerene lattice and the various ways it can be wrapped to form a cylinder or tube, nanotubes having different lattice conformations can have different physical properties. Three main classifications of nanotube lattices are used: zig-zag, chiral, and armchair. In general, the differences between these three classifications can be thought of as based on the orientation of a graphine sheet, before being wrapped into a tube, relative to a central axis along the tube. [0013] These presently available nanotube-manufacturing methodologies, as noted, can result in nanotubes with a spectrum of variability in their physical properties, including number of walls, length, diameter, and lattice structure. Thus, the current technologies do not permit one to pre-select and produce only one type of nanotube, having a single wall type, length, diameter, and lattice structure or conformation. The manufacturing cost associated with such high temperature growth processes is high due to the energy cost and time required with such batch type processes. [0014] Thus, there is a need for a reliable, consistent, controlled, and cost effective approach, so that nanotube structures may be generated within a mass production process with specificity as to length, diameter, and lattice structure, among other things. SUMMARY OF THE INVENTION [0015] The present invention addresses needs in the art by providing nanotubes having desirable characteristics. The invention also provides processes (referred to herein interchangeably as "methods") for producing nanotubes that are rapid, convenient, reliable, and relatively inexpensive. In addition, due to the processes of manufacturing, the nanotubes of the invention have an extremely low defect rate and are highly uniform in structure. Furthermore, the processes of the invention permit production of relatively long nanotubes of uniform structure, the length being primarily dependent on the length and quality of the graphene material used to fabricate the nanotubes. Thus, the present invention provides carbon nanotubes of relatively long length. In view of the above-described nanotubes and processes, the present invention provides systems and devices for fabrication of the nanotubes of the invention. [0016] In general, the process of the invention comprises use of mechanical force to curve nanometer thick materials, such as graphene sheets of approximately one atom thickness, along a single axis such that a circular or, more preferably, semi-circular, structure is formed from the material. The process further comprises use of mechanical force or electromagnetic radiation to cleave the curved material at selected points or along a selected lines parallel to the line of axis along which the curve was introduced. Upon cleavage of the curved material, two edges of the curved material are present, each running parallel to the other and each running along the axis of curvature of the material. Thus, the process of the invention is a mechanosynthesis process. According to one aspect of the process, the two edges are brought into close enough proximity that they can be joined to each other along their entire length, thus forming a tubular structure, which is a nanotube. According to another aspect, two different curved and cleaved materials are brought into close proximity such that a first edge of the first curved material is in close proximity to a first edge of the second curved material, and a second edge of the first curved material is in close proximity to the second edge of the second material. The edges that are in close proximity to each other are then joined, resulting in a tubular structure, or a nanotube. In yet a third aspect, the curved materials are brought into close proximity at the points where edges will be formed, then the edges are formed in both materials at the same, or essentially the same, time. This results in the cleaved edges from both sheets being placed into close proximity to each other immediately following cleavage. The process of joining in all aspects of the process can be spontaneous or can be mediated by application of energy or mechanical force. [0017] The processes of the invention can be applied to create essentially any length nanotube, the length being dependent primarily on the length and quality of the material being used as the nanotube material. Furthermore, because the process is controlled, at least in part, by mechanical, electromechanical, or electromagnetic means (i.e., not by chemical or biological syntheses), a high level of reproducibility and precision can be achieved, resulting in highly uniform nanotubes having pre-selected lengths, diameters, and wall structures. Thus, the present invention provides nanotubes of varying lengths, diameters, and wall structures. [0018] In its basic form, the system of the invention generally comprises a device that applies stress to a sheet of material that is suitable for formation of nanotubes; a device that cleaves the sheet of material at one or more points or along one or more lines along the sheet; and a device that feeds and/or removes the material. In embodiments, all of these functions are supplied by a single device, while in others, two or more different devices are provided to achieve these functions. In preferred embodiments, the system further comprises one or more devices that form the cleaved material into a shape that is capable of forming a generally round or tubular shape, or that form multiple cleaved sheets into shapes that are capable of forming into an overall round or tubular shape. The system may further comprise one or more devices that align and/or feed starting material into the device(s) that impart stress and/or cleave the starting material. In addition, the system may comprise one or more devices that accept and/or transport cleaved material and/or nanotubes. In addition, the system may comprise a holder for nanotubes or nanofibers awaiting formation into nanotubes. Furthermore, the system may comprise some or all of the devices and components necessary to fabricate materials that are suitable for use as nanotube materials, such as graphite/graphene. [0019] The system and method for manufacturing nanotube structures can be accomplished by mechanical means or mechanosynthesis process to allow for the formation or manufacture of nanotube structures with specificity and control as to length, diameter, and lattice structure, among other things. In general, the order in which several of the steps in the mechanosynthesis method of the invention can be performed may be interchanged. Thus, in the system of the invention, a particular device may be connected to certain other devices in one embodiment, whereas in other embodiments, the device may be connected to one or more other devices. Connections between the various devices can be made by any suitable mechanical connectors, the choice of which is not critical to construction of the devices and systems of the invention, or practice of the methods of the invention. In embodiments, some or all of the devices are rigidly connected to one or more other device. In embodiments, some or all of the devices are movably connected to one or more other device. The choice of the type of connection may be left to the discretion of the skilled artisan, and any suitable connections may be used. [0020] The present invention provides, in one embodiment, a system using mechanosynthesis action for manufacturing of nanotubes. The motive action for such a process for example, may be provided by external sources of energy including chemical, thermal, acoustic, electric field and/or magnetic field and/or mechanical torque interactions, or any combination thereof. [0021] In one embodiment, the present system incorporates the use of macroscopic rollers to enhance the ease and flexibility in motoring, braking, and other system operations during the manufacturing process. The rollers may be nanoscale or any scale in size, depending on the amount of torque capacity needed. In one such approach, rollers that are macroscopic in size with nanoscale surface features can provide for the integration across dimensional scales and on multi-functionality across various energetic domains, such as mechanics, fluidics, electromagnetics, optics, and biometric systems. Continue reading about Systems and methods of manufacturing nanotube structures... 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