Patent Publication Number: US-2012045644-A1

Title: Carbon nanotube wire composite structure and method for making the same

Description:
RELATED APPLICATIONS 
     This application claims all benefits accruing under 35 U.S.C. §119 from China Patent Application No. 201010260100.X, filed on Aug. 23, 2010 in the China Intellectual Property Office, the disclosure of which is incorporated herein by reference. This application is related to applications entitled “CARBON NANOTUBE WIRE STRUCTURE AND METHOD FOR MAKING THE SAME”, filed **** (Atty. Docket No. US33402); “MARCOSCOPIC CARBON NANOTUBE TUBE STRUCTURE AND METHOD FOR MAKING THE SAME”, filed **** (Atty. Docket No. US33568); “APPARATUS FOR MAKING CARBON NANOTUBE COMPOSITE WIRE STRUCTURE”, filed **** (Atty. Docket No. US33569) and “CARBON NANOTUBE COMPOSITE TUBE STRUCTURE AND METHOD FOR MAKING THE SAME”, filed **** (Atty. Docket No. US34823). 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a carbon nanotube composite wire structure and a method for making the same. 
     2. Discussion of Related Art 
     Carbon nanotubes can be composed of a plurality of coaxial cylinders of graphite sheets. Carbon nanotubes have received a great deal of interest since the early 1990s. Carbon nanotubes have interesting and potentially useful electrical and mechanical properties. Due to these and other properties, carbon nanotubes have become a significant focus of research and development for use in electron emitting devices, sensors, transistors, and other devices. 
     It is becoming increasingly popular for carbon nanotubes to be used to make composite materials. Composites of carbon nanotubes and metals, semiconductors, or polymers have qualities of the materials used in the composite. Generally, a carbon nanotube metal composite includes metal particles and carbon nanotubes. The method for producing the carbon nanotube metal composite includes a stirring step or a vibration step of distributing the carbon nanotubes in the metal particles, or includes a step of dispersing the metal particles in a carbon nanotube film or a carbon nanotube wire including the carbon nanotubes. However, the metal particles in the carbon nanotube metal composite are in metal powder form. The method for making the carbon nanotube metal composite is complicated and may be harmful to the environment. 
     What is needed, therefore, is to provide a carbon nanotube composite wire structure, a method for making the same, and an apparatus for making the same, to overcome the above-described shortcomings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Many aspects of the embodiments can be better understood with references to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the embodiments. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
         FIG. 1  shows a scanning electron microscope (SEM) image of a pressed carbon nanotube film. 
         FIG. 2  shows an SEM image of a flocculated carbon nanotube film. 
         FIG. 3  shows an SEM image of a drawn carbon nanotube film. 
         FIG. 4  shows an SEM image of an untwisted carbon nanotube wire. 
         FIG. 5  shows an SEM image of a twisted carbon nanotube wire. 
         FIG. 6  is a front view of one embodiment of an apparatus partially cut-away for making a carbon nanotube composite wire structure. 
         FIG. 7  is a top view of the apparatus shown in  FIG. 6  partially cut-away. 
         FIG. 8  is an isometric view of a face plate of the apparatus shown in  FIG. 6 . 
         FIG. 9  shows an SEM image of one embodiment of a carbon nanotube composite wire structure. 
         FIG. 10  is a cross-sectional view of the carbon nanotube composite wire structure shown in  FIG. 9 . 
         FIG. 11  illustrates one embodiment of a method for making a carbon nanotube composite wire structure using the apparatus shown in  FIG. 6 . 
     
    
    
     DETAILED DESCRIPTION 
     The disclosure is illustrated by way of example and not by way of limitation in the figures of the accompanying drawings in which like references indicate similar elements. It should be noted that references to “an” or “one” embodiment in this disclosure are not necessarily to the same embodiment, and such references mean at least one. 
     A carbon nanotube composite wire structure includes a conductive thread structure and a carbon nanotube layer wrapped around the conductive thread structure. The carbon nanotube layer is a consecutive structure and wound on the conductive thread structure from one end of the conductive thread structure to the other end of the conductive thread structure. The carbon nanotube layer comprises a plurality of carbon nanotubes. The carbon nanotubes are connected via van der Waals force therebetween, and are uniformly located on the entire surface of the conductive thread structure along an axis of the conductive thread structure. 
     The conductive thread structure is configured to support the carbon nanotubes, thus the conductive thread structure should have a certain strength and toughness. The conductive thread structure can be a consecutive structure with a large length-diameter ratio. The conductive thread structure can have a fixed shape. The cross-section of the conductive thread structure can be circle-shaped, triangle-shaped, rectangle-shaped or ellipse-shaped. The material of the conductive thread structure can be metal. The metal can be gold, silver, copper, aluminum, or an alloy such as copper-tin alloys. The conductive thread structure can be a metal thread or a metal string. The conductive thread structure can also be a conductive composite thread structure, such as coating an aluminum layer on a surface of copper-tin alloys thread, or plating a metal layer on a fiber thread. A diameter of the conductive thread structure can be selected as desired. In one embodiment, the conductive thread structure is a gold thread with a diameter of about 18 microns (μm), or an aluminum thread with a diameter of about 25 μm. 
     The carbon nanotube layer can be formed by a carbon nanotube structure tightly wrapping around the conductive thread structure along the axis of the conductive thread structure. The carbon nanotube layer can be a free-standing structure wrapping the entire surface of the conductive thread structure. In one embodiment, the carbon nanotube composite wire structure comprises the conductive thread structure and the carbon nanotube structure wrapping the entire surface of the conductive thread structure. 
     The carbon nanotube structure comprises a plurality of carbon nanotubes and can be orderly or disorderly aligned. The disorderly aligned carbon nanotubes are carbon nanotubes arranged along many different directions, such that the number of carbon nanotubes arranged along each different direction can be almost the same (e.g. uniformly disordered), and/or entangled with each other. The orderly aligned carbon nanotubes are carbon nanotubes arranged in a consistently systematic manner, e.g., most of the carbon nanotubes are arranged approximately along a same direction or have two or more sections with most of the carbon nanotubes arranged approximately along a same direction (different sections can have different directions). The carbon nanotubes can be single-walled, double-walled, and/or multi-walled carbon nanotubes. The diameters of the single-walled carbon nanotubes range from about 0.5 nanometers (nm) to about 50 nm. The diameters of the double-walled carbon nanotubes range from about 1 nm to about 50 nm. The diameters of the multi-walled carbon nanotubes range from about 1.5 nm to about 50 nm. 
     The free-standing carbon nanotube structure may have a planar shape or a linear shape. The carbon nanotube structure can include at least one carbon nanotube film, at least one carbon nanotube wire structure, or the combination of the carbon nanotube film and the carbon nanotube wire structure. 
     Referring to  FIG. 1 , the carbon nanotube film can also be a pressed carbon nanotube film formed by pressing a carbon nanotube array down on the substrate. The carbon nanotubes in the pressed carbon nanotube array are arranged along a same direction or along different directions. The carbon nanotubes in the pressed carbon nanotube array can rest upon each other. Adjacent carbon nanotubes are attracted to each other and combined by van der Waals attractive force. An angle between a primary alignment direction of the carbon nanotubes and a surface of the pressed carbon nanotube array is about 0 degrees to approximately 15 degrees. The greater the pressure applied, the smaller the angle obtained. If the carbon nanotubes in the pressed carbon nanotube array are arranged along different directions, the carbon nanotube structure can be isotropic. The thickness of the pressed carbon nanotube array can range from about 0.5 nm to about 1 mm. The length of the carbon nanotubes can be larger than 50 μm. Clearances can exist in the carbon nanotube array. Therefore, micropores can exist in the pressed carbon nanotube array and be defined by the adjacent carbon nanotubes. Examples of the pressed carbon nanotube film are taught by US PGPub. 20080299031A1 to Liu et al. 
     Referring to  FIG. 2 , the carbon nanotube film can be a flocculated carbon nanotube film formed by a flocculating method. The flocculated carbon nanotube film can include a plurality of long, curved, disordered carbon nanotubes entangled with each other. A length of the carbon nanotubes can be greater than 10 centimeters. In one embodiment, the length of the carbon nanotubes is in a range from about 200 microns to about 900 μm. Further, the flocculated carbon nanotube film can be isotropic. Here, “isotropic” means the carbon nanotube film has properties identical in all directions substantially parallel to a surface of the carbon nanotube film. The carbon nanotubes can be substantially uniformly distributed in the carbon nanotube film. The adjacent carbon nanotubes are acted upon by the van der Waals attractive force therebetween, thereby forming an entangled structure with micropores defined therein. The thickness of the flocculated carbon nanotube film can range from about 1 μm to about 1 millimeter (mm) In one embodiment, the thickness of the flocculated carbon nanotube film is about 100 μm. 
     Referring to  FIG. 3 , the carbon nanotube film can also be a drawn carbon nanotube film formed by drawing a film from a carbon nanotube array. Examples of the drawn carbon nanotube film are taught by U.S. Pat. No. 7,045,108 to Jiang et al. The thickness of the drawn carbon nanotube film can be in a range from about 0.5 nm to about 100 μm. 
     The drawn carbon nanotube film includes a plurality of carbon nanotubes that are arranged substantially parallel to a surface of the drawn carbon nanotube film. A large number of the carbon nanotubes in the drawn carbon nanotube film can be oriented along a preferred orientation, meaning that a large number of the carbon nanotubes in the drawn carbon nanotube film are arranged substantially along the same direction. An end of one carbon nanotube is joined to another end of an adjacent carbon nanotube arranged substantially along the same direction by van der Waals attractive force. A small number of the carbon nanotubes are randomly arranged in the drawn carbon nanotube film, and has a small if not negligible effect on the larger number of the carbon nanotubes in the drawn carbon nanotube film arranged substantially along the same direction. It can be appreciated that some variation can occur in the orientation of the carbon nanotubes in the drawn carbon nanotube film. Microscopically, the carbon nanotubes oriented substantially along the same direction may not be perfectly aligned in a straight line, and some curve portions may exist. It can be understood that contact between some carbon nanotubes located substantially side by side and oriented along the same direction cannot be totally excluded. 
     More specifically, the drawn carbon nanotube film can include a plurality of successively oriented carbon nanotube segments joined end-to-end by van der Waals attractive force therebetween. Each carbon nanotube segment includes a plurality of carbon nanotubes substantially parallel to each other, and joined by van der Waals attractive force therebetween. The carbon nanotube segments can vary in width, thickness, uniformity, and shape. The carbon nanotubes in the drawn carbon nanotube film are also substantially oriented along a preferred orientation. The width of the drawn carbon nanotube film relates to the carbon nanotube array from which the drawn carbon nanotube film is drawn. 
     The carbon nanotube structure can include more than one drawn carbon nanotube film. An angle can exist between the orientation of the carbon nanotubes in adjacent films, stacked, and/or coplanar. Adjacent carbon nanotube films can be combined by only the van der Waals attractive force therebetween without the need of an additional adhesive. An angle between the aligned directions of the carbon nanotubes in two adjacent drawn carbon nanotube films can range from about 0 degrees to about 90 degrees. Spaces are defined between two adjacent carbon nanotubes in the drawn carbon nanotube film. If the angle between the aligned directions of the carbon nanotubes in adjacent drawn carbon nanotube films is larger than 0 degrees, the micropores can be defined by the crossed carbon nanotubes in adjacent drawn carbon nanotube films. 
     The carbon nanotube wire structure can also include at least one carbon nanotube wire. If the carbon nanotube wire structure includes a plurality of carbon nanotube wires, the carbon nanotube wires can be substantially parallel to each other to form a bundle-like structure or twisted with each other to form a twisted structure. The bundle-like structure and the twisted structure are two kinds of linear shaped carbon nanotube structures. 
     The carbon nanotube wire itself can be untwisted or twisted. Referring to  FIG. 4 , treating the drawn carbon nanotube film with a volatile organic solvent can obtain the untwisted carbon nanotube wire. In one embodiment, the organic solvent is applied to soak the entire surface of the drawn carbon nanotube film. During the soaking, adjacent substantially parallel carbon nanotubes in the drawn carbon nanotube film will bundle together, due to the surface tension of the organic solvent as it volatilizes, and thus the drawn carbon nanotube film will be shrunk into an untwisted carbon nanotube wire. The untwisted carbon nanotube wire includes a plurality of carbon nanotubes substantially oriented along a same direction (i.e., a direction along the length direction of the untwisted carbon nanotube wire). The carbon nanotubes are substantially parallel to the axis of the untwisted carbon nanotube wire. In one embodiment, the untwisted carbon nanotube wire includes a plurality of successive carbon nanotubes joined end to end by van der Waals attractive force therebetween. A length of the untwisted carbon nanotube wire can be arbitrarily set as desired. A diameter of the untwisted carbon nanotube wire ranges from about 0.5 nm to about 100 μm. Examples of the untwisted carbon nanotube wire are taught by US Patent Application Publication US 2007/0166223 to Jiang et al. 
     Referring to  FIG. 5 , the twisted carbon nanotube wire can be obtained by twisting a drawn carbon nanotube film using a mechanical force to turn the two ends of the drawn carbon nanotube film in opposite directions. The twisted carbon nanotube wire includes a plurality of carbon nanotubes helically oriented around an axial direction of the twisted carbon nanotube wire. In one embodiment, the twisted carbon nanotube wire includes a plurality of successive carbon nanotubes joined end to end by van der Waals attractive force therebetween. The length of the carbon nanotube wire can be set as desired. A diameter of the twisted carbon nanotube wire can be from about 0.5 nm to about 100 μm. 
     The twisted carbon nanotube wire can be treated with a volatile organic solvent, before or after being twisted. After being soaked by the organic solvent, the adjacent substantially parallel carbon nanotubes in the twisted carbon nanotube wire will bundle together, due to the surface tension of the organic solvent when the organic solvent volatilizes. The specific surface area of the twisted carbon nanotube wire will decrease, and the density and strength of the twisted carbon nanotube wire will be increased. 
     If the carbon nanotube layer comprises drawn carbon nanotube films or untwisted carbon nanotube wires, the carbon nanotube composite wire structure can include the conductive thread structure and the drawn carbon nanotube films winding around the conductive thread structure by van der Waals force therebetween, or can include the conductive thread structure and the untwisted carbon nanotube wires wrapping around the conductive thread structure via van der Waals force therebetween. The carbon nanotube layer in the carbon nanotube composite wire structure is composed of carbon nanotubes. Most of the carbon nanotubes can be located on the surface of the conductive thread structure, and most of the adjacent carbon nanotubes substantially extending along a same direction can be joined end-to-end via van der Waals force therebetween. Furthermore, most of the carbon nanotubes can substantially spirally extend along the axis of the conductive thread structure, and most of the carbon nanotubes and the axis of the conductive thread structure cooperatively define an angle larger than 0 degrees and less than or equal to 90 degrees. Carbon nanotubes in each of the drawn carbon nanotube films or each of the untwisted carbon nanotube wires substantially extend along a same direction. The angles defined between most of the carbon nanotubes in the carbon nanotube composite wire structure and the axial of the conductive thread structure can be substantially equal to each other. 
     If the carbon nanotube layer in the carbon nanotube composite wire structure comprises flocculated carbon nanotube films, the flocculated carbon nanotube films can be combined by van der Waals force therebetween and wrap around the entire surface of the conductive thread structure. The flocculated carbon nanotube film can be composed of a plurality of carbon nanotubes entangled with each other. The carbon nanotubes can be substantially tightly and uniformly positioned on the surface of the conductive thread structure. 
     If the carbon nanotube layer in the carbon nanotube composite wire structure comprises pressed carbon nanotube films, the pressed carbon nanotube films can be tightly joined via van der Waals force therebetween and wrap around the entire surface of the conductive thread structure. If the pressed carbon nanotube film includes a plurality of disordered carbon nanotubes, the carbon nanotubes can be disorderly, uniformly, and tightly arranged along the axial direction of the conductive thread structure. The pressed carbon nanotube film includes carbon nanotubes substantially resting upon each other. The carbon nanotubes can be uniformly and tightly arranged along the axis of the conductive thread structure, and adjacent carbon nanotubes are attracted to each other and combined by van der Waals attractive force. An angle between a primary alignment direction of the carbon nanotubes and a surface of the conductive thread structure can be 0 degrees to approximately 15 degrees. 
     If the carbon nanotube layer in the carbon nanotube composite wire structure comprises twisted carbon nanotube wire, the twisted carbon nanotube wire can be tightly combined via van der Waals force therebetween and can be wound substantially around the entire surface of the conductive thread structure without gaps. The carbon nanotubes in the twisted carbon nanotube wire can be uniformly positioned on the surface of the conductive thread structure. 
     The carbon nanotubes have excellent mechanical properties such as toughness, and can improve the mechanical properties of the composited materials. The carbon nanotubes are uniformly located on the surface of the conductive thread structure by van der Waals force. The carbon nanotube composite wire structure including the carbon nanotubes are especially tough and can have good mechanical properties. If tension is applied to the carbon nanotube composite wire, friction forces can be formed between the carbon nanotubes and the conductive thread structure. The friction forces can aid in preventing the conductive thread structure from being broken. The carbon nanotube composite wire structure can be lengthened from about 5% to about 10% times the length of the conductive thread structure. Properties of the carbon nanotube composite wire structure are not only related to the properties of the conductive thread structure, but also affected by the structure and weight of the carbon nanotube layer. 
     A method for making the above mentioned carbon nanotube composite wire structure is provided. The method includes the following steps: 
     (a), providing the conductive thread structure and the carbon nanotube structure; and 
     (b), winding the carbon nanotube structure around the conductive thread structure. 
     The step (b) can include the following steps: (b1), adhering one end of the carbon nanotube structure to the conductive thread structure; and (b2), rotating the conductive thread structure with the carbon nanotube structure, and simultaneously moving the conductive thread structure or the carbon nanotube structure along a fixed direction. 
     It can be understood that the step (b) can further include collecting the carbon nanotube composite wire structure. 
     In one embodiment, if the carbon nanotube structure is drawn carbon nanotube film or untwisted carbon nanotube wire, the step (a) can include providing the conductive thread structure and at least one carbon nanotube array, and drawing a carbon nanotube film or an untwisted carbon nanotube wire from the carbon nanotube array to form the carbon nanotube structure. The step (b) can include attaching the carbon nanotube structure to the conductive thread structure, and rotating the conductive thread structure or the carbon nanotube structure to wind the carbon nanotube structure around the conductive thread structure. While winding the carbon nanotube structure, the carbon nanotube structure can be continuously drawn from the at least one carbon nanotube array. 
     Referring to  FIG. 6 ,  FIG. 7 , and  FIG. 8 , one embodiment of an apparatus  100  for making a carbon nanotube composite wire structure is provided. The apparatus  100  can include a supply unit  20 , a wrapping unit  30 , a collecting unit  40 , and a support  50 . The supply unit  20  supplies a linear structure. The wrapping unit  30  can load at least one carbon nanotube array thereon. A carbon nanotube structure (not shown) can be drawn from the at least one carbon nanotube array. The carbon nanotube structure can be at least one drawn carbon nanotube film, at least one untwisted carbon nanotube wire, or a combination thereof. The wrapping unit  30  is to wrap the carbon nanotube structure around the linear structure, thereby forming the carbon nanotube composite wire structure. The collecting unit  40  can drive the linear structure to move along a fixed direction and collect the carbon nanotube composite wire structure. The support  50  can support the supply unit  20 , the wrapping unit  30 , and the collecting unit  40 . 
     The support  50  can be a planar structure. The supply unit  20 , the wrapping unit  30 , and the collecting unit  40  can be fixed on a same surface of the support  50 . The support  50  can be made of metal such as steel or aluminum. 
     The supply unit  20  can include a pedestal  22 , a guiding shaft  24 , a bobbin  16 , and two collars  26 . The pedestal  22  is substantially perpendicular to the support  50  by fixing one end of the pedestal  22 . One end of the guiding shaft  24  is fixed on the pedestal  22 , and the other end is suspended. The guiding shaft  24  is substantially perpendicular to the pedestal  22 . The bobbin  16  is hung on the guiding shaft  24 , and can be freely moved around the guiding shaft  24 . The bobbin  16  is for winding a linear structure thereon. The linear structure can be a conductive thread structure or a non-conductive thread structure. The non-conductive thread structure can be a carbon fiber, an artificial fiber such as Kevlar, or a natural fiber. The natural fiber can be spider silk or silkworm silk. The conductive thread structure can be a metal thread, a conductive polymer thread, or a combination thereof. The two collars  26  can be mounted on the guiding shaft  24  and fixed at two opposite sides of the bobbin  16  to prevent the bobbin  16  from falling from the guiding shaft  24 . The number of the collar  26  is not restricted to two, and can be one, three, or more, provided the bobbin  16  is hung at the guiding shaft  24 . 
     The wrapping unit  30  can be configured to load a carbon nanotube array with a growing substrate for growing the carbon nanotube array. The wrapping unit  30  can include a drive mechanism  32 , a hollow rotating shaft  34 , two bearings  33 , two braces  35 , a face plate  36 , and a covering element  38 . The drive mechanism  32  is positioned at one end of the hollow rotating shaft  34  close to the supply unit  20 . The face plate  36  is located at the other end of the hollow rotating shaft  34 . The two bearings  35  are separately harnessed to the hollow rotating shaft  34 . Each brace  35  is coupled with a bearing  33  to support the hollow rotating shaft  34 . 
     The drive mechanism  32  drives the hollow rotating shaft  34  to rotate. The hollow rotating shaft  34  is rotated to allow the face plate  36  to rotate. The drive mechanism  32  can include an actuator  320  and a first motor  328 . The actuator  320  is driven by the first motor  328 . The actuator  320  can include a first belt pulley  322 , a second belt pulley  324 , and a belt  326 . The first belt pulley  322  is mounted on the first motor  328 . The second belt pulley  324  is separated from the first belt pulley  322 , and mounted on the hollow rotating shaft  34 . The belt  326  is harnessed to the first belt pulley  322  and the second belt pulley  324 . The first belt pulley  322  can be rotated under the first motor  328 . The first belt pulley  322  can drive the second belt pulley  324  to rotate by the belt  328 . The second belt pulley  324  drives the hollow rotating shaft  34  to rotate. Therefore, a speed of the first motor  328  can control a rotating speed of the hollow rotating shaft  34 . The structure of the drive mechanism  32  is not restricted by the above description, provided the drive mechanism  32  can drive the hollow rotating shaft  34  to rotate. 
     The hollow rotating shaft  34  is substantially parallel to the support  50 . A block nut  342  is screwed on one end of the hollow rotating shaft  34  close to the second belt pulley  324 . The block nut  342  is positioned on the hollow rotating shaft  34  close to the supply unit  20  to prevent the second belt pulley  324  from falling off. The hollow rotating shaft  34  defines an invisible axis  344 . The invisible axis  344  can substantially overlap with the linear structure when the linear structure passes through the hollow rotating shaft  34 . The invisible axis  344  and the highest position of the guiding shaft  34  are kept substantially on the same line. In this content, “the highest position” is assigned to the longest distance between the hollow rotating shaft  34  and the support  50 . The hollow rotating shaft  34  can be rotated clockwise or anti-clockwise around the invisible axis  344  by the driving mechanism  32 . 
     The two braces  35  are fixed on the support  50  and separately located between the driving mechanism  32  and the face plate  36 . The second belt pulley  324  is positioned between one of the two braces  35  and the block nut  342 . Thus, the second belt pulley  324  cannot move along the extending direction of the hollow rotating shaft  34 . 
     The face plate  36  is suspended over the support  50  and harnessed on the hollow rotating shaft  34 . As such, the face plate  36  can accompany the hollow rotating shaft  34  to rotate around the invisible axis  344 . The hollow rotating shaft  34  is driven by the first motor  328 , such that the rotating speed of the face plate  36  is controlled by the motor  328 . The shape of the face plate  36  is similar to a frustum pyramid, such as a triangular frustum pyramid, a quadrangular frustum pyramid, a pentangular frustum pyramid, a hexangular frustum pyramid, or a heptangular frustum pyramid. The face plate  36  has a plurality of side surfaces. A support stage  362  protrudes from each side surface. A plurality of support stages  362  loads the carbon nanotube array. Each support stage  362  can define an angle with the invisible axis  344 , and can face the collecting unit  40 . A plurality of support stages  362  uniformly surrounds the hollow rotating shaft  34 . In one embodiment, the shape of the face plate  36  is similar to a hexangular frustum pyramid. Six support stages  362  protrude from the side surfaces of the hexangular frustum pyramid. Each support stage  362  can define the angle of about 45 degrees with the invisible axis  344 . 
     The covering element  38  can define a chamber  382  therein to receive the face plate  36 . Thus, the covering element  38  can prevent the carbon nanotube arrays from being thrown off from the face plate  36 . The covering element  38  can also keep the carbon nanotube arrays free from dust and other contaminations. It can be understood that the covering element  38  is a selected structure. 
     The collecting unit  40  is fixed on the support  50  close to the face plate  36 . The collecting unit  40  can include a second motor  42  and a collecting shaft  44  fixed on the second motor  42 . The collecting shaft  44  is suspended over the support  50 . The collecting shaft  44  defines an invisible axis  442  substantially perpendicular to the invisible axis  344  of the hollow rotating shaft  34 . The highest point of the collecting shaft  44  from the support  50  is substantially kept at a same line with the invisible axis  344 . The collecting shaft  44  can rotate around the invisible axis  442  under the second motor  42 . As such, the linear structure can be driven along a line, and the carbon nanotube composite wire structure can be collected on the surface of the collecting shaft  44 . Therefore, the second motor  42  can control the rotating speed of the collecting shaft  44 . The second motor  42  can also control the collecting speed of the carbon nanotube composite wire structure. 
     The apparatus  100  can further include two locating elements  60 . Each locating element  60  defines a locating hole. The center of the locating hole and the invisible axis  344  of the hollow rotation shaft  34  are substantially maintained at a same line. The two locating elements  60  are configured to ensure the linear structure is sustained at substantially a same plane and does not contact the inner wall of the hollow rotation shaft  34 . One locating element  60  is fixed between the supply unit  20  and the wrapping unit  30 , thus the linear structure is suspended in the hollow rotation shaft  34 . The other locating element  60  is positioned between the wrapping unit  30  and the collecting unit  40 , thus the carbon nanotube composite wire structure made by the apparatus  100  and the highest position of the collecting shaft  44  can substantially stay on the same plane. The number of the locating element  60  can be selected as desired. 
     A method for making a carbon nanotube composite wire structure using the apparatus  100  can include the following steps: 
     S 10 , providing a linear structure using the supply unit  20 ; 
     S 20 , passing the linear structure through the wrapping unit  30 , and fixing the linear structure on the collecting unit  40 ; 
     S 30 , providing a carbon nanotube structure by the wrapping unit  30 , and adhering one end of the carbon nanotube structure to the linear structure; and 
     S 40 , rotating the face plate  36  and moving the linear structure along a fixed direction to wind the carbon nanotube structure around the linear structure. 
     The step S 10  can include the steps: winding the linear structure around the bobbin  16 ; hanging the bobbin  16  with the linear structure on the guiding shaft  24 ; and limiting the bobbin  16  between the two collars  26 . The bobbin  16  with the linear structure coiled thereon can be moved around the guiding shaft  24 . 
     The step S 20  can include the steps: passing a free end of the linear structure through the hollow rotation shaft  34 ; and fixing the free end of the linear structure on the surface of the collecting shaft  44 . It can be understood that the linear structure can pass through the two locating holes  62  in sequence before the linear structure is fixed on the collecting shaft  44 . The linear structure substantially overlaps the invisible axis  344 . 
     In one embodiment, the carbon nanotube structure can be at least one drawn carbon nanotube film, at least one untwisted carbon nanotube wire, or combinations thereof, and the step S 30  can include the following sub-steps: 
     S 31 , providing at least one carbon nanotube array grown on a growing substrate; 
     S 32 , fixing the growing substrate on the face plate  36 ; and 
     S 33 , drawing a drawn carbon nanotube film or an untwisted carbon nanotube wire from each carbon nanotube array using a stretching tool, and adhering one end of the carbon nanotube film or the untwisted carbon nanotube wire to the linear structure. 
     In step S 31 , the carbon nanotube array is composed of a plurality of carbon nanotubes. The plurality of carbon nanotubes can be single-walled carbon nanotubes, double-walled nanotubes, multi-walled carbon nanotubes, or any combination thereof. In one embodiment, the plurality of carbon nanotubes comprises substantially parallel multi-walled carbon nanotubes. The carbon nanotube array is essentially free of impurities such as carbonaceous or residual catalyst particles. The carbon nanotube array can be a super aligned carbon nanotube array. A method for making the carbon nanotube array is unrestricted, and can be by chemical vapor deposition methods or other methods. 
     In step S 32 , each growing substrate with the carbon nanotube array grown thereon is fixed on the support stage  362  by adhesive, mechanical tools or vacuum absorption. 
     In step S 33 , each carbon nanotube film or untwisted carbon nanotube wire can be formed by selecting one or more carbon nanotubes having a predetermined width from each carbon nanotube array, and pulling the carbon nanotubes at a substantially uniform speed to form carbon nanotube segments that are joined end to end to achieve the uniform drawn carbon nanotube film or untwisted carbon nanotube wire. During the pulling process, as the initial carbon nanotube segments are drawn out, other carbon nanotube segments are also drawn out end to end due to van der Waals force between ends of adjacent segments. The stretching tool can be a ruler, tweezers, or an adhesive tape. 
     It is noted that because the carbon nanotubes in the carbon nanotube array have a high purity and a high specific surface area, the drawn carbon nanotube film or untwisted carbon nanotube wire is adhesive. As such, the carbon nanotube film or untwisted carbon nanotube wire can be adhered to the surface of the linear structure directly and a plurality of drawn carbon nanotube films or untwisted carbon nanotube wires can be adhered to a surface one after another. 
     It is noted that the covering element  38  is opened to expose the face plate  36  to surroundings in step S 32  and step S 33 . 
     The step S 40  can include: operating the drive mechanism  32  to rotate the face plate  36 , and simultaneously controlling the collecting unit  40  to pull the linear structure along a line, such that the carbon nanotube structure winds around the linear structure. Specifically, the second motor  42  is operated to drive the collecting shaft  44  to rotate around the invisible axis  442  thereof, such that the linear structure can be continuously supplied by the supply unit  20  and move towards the collecting shaft  44 . As such the drawn carbon nanotube film or untwisted carbon nanotube wire can be continuously drawn from each carbon nanotube array. Simultaneously, the first motor  328  is operated to make the actuator  320  move along a predetermined direction, such that the hollow rotating shaft  34  is rotated around the invisible axis  344  thereof. Thus, the face plate  36  is rotated around the invisible axis  344  of the hollow rotating shaft  34 , and the at least one carbon nanotube array located on the face plate  36  is also rotated around the invisible axis  344  of the hollow rotating shaft  34 . As such, the drawn carbon nanotube film or the untwisted carbon nanotube wire is stretched from each carbon nanotube array, and wrapped around the surface of the linear structure, thereby forming the carbon nanotube composite wire structure. If the second motor  42  drives the collecting shaft  44  to rotate, the carbon nanotube composite wire can automatically wind around the collecting shaft  44 . Thus, the carbon nanotube composite wire can be continuously manufactured and automatically collected on the collecting shaft  44 . It is noted that when the wrapped unit  30  is operated, the covering element  38  should keep in a close situation to make sure the face plate  36  is covered by the covering element  38 . 
     It can be understood that if the face plate  36  is maintained at a certain rotating speed, the quicker the collecting shaft  44  rotates, the quicker the speed of the collecting shaft  44  driving the linear structure. The linear structure can move quicker, the thinner the carbon nanotube layer in the carbon nanotube composite wire structure. If the face plate  36  is sustained at a certain rotating speed, the more slowly the collecting shaft  44  rotates, the slower the collecting shaft  44  drives the linear structure, the linear structure can move slowly, such that the thicker the carbon nanotube layer in the carbon nanotube composite wire structure. If the collecting shaft  44  is maintained at a certain speed, the quicker the face plate  36  rotates, the quicker the speed of the carbon nanotube structure is wound on the linear structure, the thicker carbon nanotube layer in the carbon nanotube composite wire structure. If the collecting shaft  44  is maintained at a certain speed, the slower the face plate  36  rotates, the slower the speed of the carbon nanotube structure is wound on the linear structure, and the thinner the carbon nanotube layer in the carbon nanotube composite wire structure. Therefore, the rotating speeds of the collecting shaft  44  and the face plate  36  cooperatively affect the thickness of the carbon nanotube layer. Thus, the thickness of the carbon nanotube layer can be controlled by the work speeds of the second motor  42  and the first motor  328 . 
     Therefore, the apparatus  100  can continuously produce the carbon nanotube composite wire structure and be applied in industry. 
     The disclosure can be further set forth by an example of a carbon nanotube gold thread composite wire structure. 
     Referring to  FIG. 9  and  FIG. 10 , one embodiment of a carbon nanotube gold thread composite wire structure  10  is provided. The carbon nanotube gold thread composite wire structure  10  has a diameter of about 40 μm. The carbon nanotube gold thread composite wire structure  10  consists of a gold thread  12  with a diameter of about 18 μm and a carbon nanotube layer  14  surrounding the gold thread  12 . The carbon nanotube layer  14  is composed of a plurality of carbon nanotubes  142 . The carbon nanotubes  142  are tightly and uniformly located on the surface of the gold thread  12 . The carbon nanotube layer  14  winds around the gold thread  12  from one end of the gold thread  12  to the other opposite end of the gold thread  12 . 
     Specifically, six drawn carbon nanotube films spiraling about the gold thread  12  upwards along the axial direction of the gold thread  12  form the carbon nanotube gold thread composite wire structure  10 . Most of the carbon nanotubes  142  arranged along a same direction are joined end-to-end via van der Waals force. The six drawn carbon nanotube films wrap the entire surface of the gold thread  12  across the lengthwise direction of the gold thread  12 . 
     Furthermore, most of the carbon nanotubes  142  spirally extend along the axis of the gold thread  12 . Most of the carbon nanotubes  142  and the axis of the gold thread  12  cooperatively define an angle (not labeled) of about 45 degrees. In addition, most of the carbon nanotubes  142  in each drawn carbon nanotube film substantially extend along a same direction, as such angles defined between most of the carbon nanotubes  142  and the axis of the gold thread  12  have the same degrees. 
     The carbon nanotube gold thread composite wire structure  10  has good mechanical properties, especially toughness. The carbon nanotube gold thread composite wire structure  10  can be lengthened from about 5% to about 10% of the length of the gold thread  12 . 
     Referring to  FIG. 11 , a method for making the carbon nanotube gold thread composite wire structure  10  is provided. The method can include providing the gold thread  12  and the carbon nanotube structure, and winding the carbon nanotube structure around the gold thread  12 . The method can be performed by using the apparatus  100 . Specifically, the method realized using the apparatus  10  can include the following steps: 
     S 100 , providing the gold thread  12  using the supply unit  20 ; 
     S 200 , passing the gold thread  12  through the hollow rotation shaft  34  and fixing the free end of the gold thread  12  on the collecting shaft  44 ; 
     S 300 , forming six drawn carbon nanotube films  15  by the wrapping unit  30 , and adhering the six drawn carbon nanotube films  15  to the gold thread  12 ; and 
     S 400 , rotating the face plate  36 , and simultaneously rotating the collecting shaft  44 . 
     In step S 100 , the gold thread  12  winds around the bobbin  16 . The bobbin  16  with the gold thread  12  coiled is hung on the guiding shaft  24  and fixed between the two collars  26 . 
     The step S 200  can be performed by pulling the gold thread  12  from the bobbin  16 , passing the gold thread  12  through one of the two locating holes  62 , the hollow rotation shaft  34 , and the other locating hole  62  in sequence, and fixing the free end of the gold thread  12  on the collecting shaft  44 . The gold thread  12  substantially overlaps with the invisible axis  344  of the hollow rotating shaft  34 . 
     In step S 300 , the six carbon nanotube arrays  18  with growing substrates (not labeled) are provided. The covering element  38  is opened to expose the face plate  36 . The six growing substrates are adhered to the support stages  362  one by one using double faced adhesive tape. The six drawn carbon nanotube films  15  are orderly drawn from the six carbon nanotube arrays  18 . Next, the six drawn carbon nanotube films  15  are adhered to the gold thread  12 . The covering element  38  is then closed to cover the face plate  36  in the chamber  382  of the covering element  38 . 
     The step S 400  can include: operating the drive mechanism  32  to rotate the face plate  36 , and controlling the collecting unit  40  to move the gold thread  12  along a line, such that the six drawn carbon nanotube films  15  can spirally wind around the gold thread  12 . Specifically, the second motor  42  and first motor  328  are operated. The collecting shaft  44  is rotated clockwise around the invisible axis  442  of the collecting shaft  44 . The gold thread  12  is continuously pulled out and moved towards the collecting unit  40 , and simultaneously the six drawn carbon nanotube films  15  are continuously drawn from the six carbon nanotube arrays  18 , and the first motor  328  drives the actuator  320 . The actuator  320  drives the hollow rotating shaft  34  to rotate around the invisible axis  344  of the hollow rotating shaft  34 . The hollow rotating shaft  34  drives the face plate  36  to rotate around the invisible axis  344 . The six carbon nanotube arrays  18  and the six carbon nanotube films  15  are rotated around the invisible axis  344  accompanying the rotation of the face plate  36 . The moving direction of the gold thread  12  can be substantially perpendicular to the rotation of the face plate  36 . The six drawn carbon nanotube films  15  spirally wind around the gold thread  12 , thereby forming the carbon nanotube gold thread composite wire structure  10 . The carbon nanotube gold thread composite wire structure  10  automatically winds around the collecting shaft  44  as the collecting shaft  44  rotates. Thus, when the collecting unit  40  and the wrapping unit  30  are operating, the gold thread  12  can be continuously pulled, the six drawn carbon nanotube films  15  can be continuously drawn from the carbon nanotube arrays  18  and wind around the gold thread  12 , and the carbon nanotube gold thread composite wire structure  10  is continuously wrapped on the collecting shaft  44 . Therefore, the carbon nanotube composite wire is continuously manufactured. 
     In one embodiment, the carbon nanotube composite wire structure can be a carbon nanotube aluminum thread composite wire structure with a diameter of about 50 μm. The carbon nanotube aluminum thread composite wire structure can include an aluminum thread with the diameter of about 25 μm and a plurality of carbon nanotubes spirally arranged along the axial direction of the aluminum thread. 
     According to the above descriptions, the carbon nanotube composite wire structure, and the method and apparatus for making the carbon nanotube composite wire structure of the present disclosure have the following advantages. 
     First, because the carbon nanotubes  142  have excellent mechanical properties and can be a good strengthening material, the carbon nanotubes  142  are uniformly positioned around the gold thread  12 , and as such the carbon nanotube gold thread composite wire structure  10  has good mechanical properties. For example, the carbon nanotube gold thread composite wire structure  10  can be lengthened from 5% to 10% of the length of the gold thread  12 . Therefore, the carbon nanotube gold thread composite wire structure  10  can be widely applied, such as acting as a conductive wire. 
     Second, the carbon nanotube gold thread composite wire structure  10  can be made by winding the carbon nanotube structure around the gold thread  12 , so the method is simple and easy to produce. In addition, in the method, the liquid agent is unnecessary and the carbon nanotube structure and the gold thread  12  are macroscopic, therefore the method is friendly to the environment. 
     Third, the apparatus  10  includes the face plate  36  and the collecting shaft  44 . The face plate  36  is rotated around the invisible axis  344  of the hollow rotating shaft  34 . The collecting shaft  44  is rotated around the invisible axis  442  thereof. Thus, the carbon nanotube structure can be automatically wound around the linear structure, and the carbon nanotube composite wire structure can be automatically collected on the collecting shaft  44 . Therefore, the apparatus  10  can continuously and automatically produce and collect the carbon nanotube composite wire structure. The method for making the carbon nanotube composite wire structure is simple and environmentally friendly. Thus, the carbon nanotube composite wire structure can be practical in industry. 
     It is to be understood that the above-described embodiment is intended to illustrate rather than limit the disclosure. Variations may be made to the embodiment without departing from the spirit of the disclosure as claimed. The above-described embodiments are intended to illustrate the scope of the disclosure and not restricted to the scope of the disclosure. 
     It is also to be understood that the above description and the claims drawn to a method may include some indication in reference to certain steps. However, the indication used is only to be viewed for identification purposes and not as a suggestion as to an order for the steps.