Abstract:
An electrode lead of a pacemaker includes a metal conductive core, a carbon nanotube film, and an insulator. The metal conductive core defines an extending direction. The carbon nanotube film at lest partially surrounds the metal conductive core and is electrically insulated from the metal conductive core. The insulator is located between the metal conductive core and the carbon nanotube film. The carbon nanotube film includes a plurality of carbon nanotubes substantially extending along the extending direction of the metal conductive core. A bared part is defined at one end of the electrode lead. A pacemaker using the above mentioned electrode lead is also disclosed.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims all benefits accruing under 35 U.S.C. §119 from China Patent Application No. 201110333521.5, filed on Oct. 28, 2011 in the China Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
       BACKGROUND 
       [0002]    1. Technical Field 
         [0003]    The present disclosure relates to an electrode lead based on carbon nanotubes and a pacemaker using the electrode lead. 
         [0004]    2. Discussion of Related Art 
         [0005]    Pacemakers are electronic therapeutic devices which can be implanted into human bodies. The pacemakers can emit pulse currents to stimulate organs. 
         [0006]    The pacemaker includes a pulse generator and an electrode lead. The pulse generator is electrically connected with the electrode lead. The electrode lead includes a connector, an electrode lead, and an electrode tip. The connector is electrically connected with the pulse generator. The connector and the electrode tip are located at two opposite ends of the electrode lead. The electrode lead includes a plurality of metal wires. The connector and the electrode tip are electrically connected with the metal wires. However, the electrode lead composed of the metal wires has poor strength and ductility, and is easily broken due to repeat distortions. Thus, the lifetimes of the lead electrode and the pacemaker using the lead electrode are reduced. 
         [0007]    What is needed, therefore, is to provide an electrode lead and a pacemaker using the same, which can overcome the shortcomings as discussed above. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    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. 
           [0009]      FIG. 1  is a schematic view of one embodiment of a heart pacemaker. 
           [0010]      FIG. 2  is a stepped, cross-sectional view of part of the electrode lead shown in  FIG. 1 . 
           [0011]      FIG. 3  shows a scanning electronic microscope (SEM) image of a carbon nanotube film used in  FIG. 1 . 
           [0012]      FIG. 4  shows a process schematic view for making the carbon nanotube film shown in  FIG. 4  from a carbon nanotube array. 
           [0013]      FIG. 5  shows a schematic view of one embodiment of a heart pacemaker. 
           [0014]      FIG. 6  is a stepped, cross-sectional view of part of the electrode lead shown in  FIG. 5 . 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    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. 
         [0016]    Referring to  FIG. 1 , one embodiment of a pacemaker  100  includes a pulse generator  10  and an electrode lead  20  electrically connected with the pulse generator  10 . The electrode lead  20  has a connector  30  and a bared part  40  opposite to the connector  30 . The electrode lead  20  has a proximal end and a distal end opposite to the proximal end. The connector  30  is located at the proximal end the electrode lead  20 , and the bared part  40  is located at the distal end of the electrode lead  20 . The electrode lead  20  is electrically connected with the pulse generator  10  through the connector  30 . The pulse generator  10  can generate pulse signals to stimulate organs of living beings via the electrode lead  20 . 
         [0017]    The pulse generator  10  can include a shell (not labeled), a power source (not shown), and a control circuit (not shown). The power source and the control circuit are packaged in the shell. The power source can provide power for the control circuit. Batteries can be used as the power source, such as lithium ion batteries, fuel cells, and physical power batteries. In one embodiment, a lithium-iodine battery is the power source. The control circuit can include an output circuit and a sensing circuit. The output circuit can be used to generate the pulse signals. The sensing circuit can be used to receive electrical signals generated by the stimulated organs and feed these electrical signals back to the output circuit. The output circuit can adaptively adjust to output proper pulse signals according to the feedback of the sensing circuit. The organs can be a heart, brain, or stomach of living beings. In one embodiment, the organ is the heart of a human being. The pulse signals can be a square wave pulsing current. A pulse width of the pulse signals can be in a range from about 0.5 milliseconds to about 0.6 milliseconds. The pulse current can be generated by a charging-discharging process of a capacitor in the control circuit. The shell used for packaging can prevent an interaction between the power source, the control circuit and the living being in which the pacemaker is implanted. A material of the shell can be a metal or alloy, which is biocompatible, corrosion resistant, and structurally tough or rigid. In one embodiment, the material of the shell is titanium. 
         [0018]    The electrode  20  can include a metal conductive core, a carbon nanotube film, and an insulator (not labeled) located between the metal conductive core and the carbon nanotube film. The insulator can include a first insulated layer, a shield layer, and a second insulated layer. Referring  FIG. 2 , the electrode lead  20  can include a metal conductive core  21 , a first insulated layer  22  winding round the metal conductive core  21 , a shield layer  23  wrapping around the first insulated layer  22 , a second insulated layer  24  winding around the shield layer  23 , a carbon nanotube film  25  wrapping round the second insulated layer  24 , and a coating layer  26  winding around the carbon nanotube film  25 . A part of the carbon nanotube film  25  is exposed through the coating layer  26 . The carbon nanotube film  23  includes a number of carbon nanotubes substantially oriented along a same direction. The carbon nanotubes substantially extend along an axial direction of the metal conductive core  21 . 
         [0019]    The electrode lead  20  can further include a ring electrode (not shown) located on the carbon nanotube film  25  exposed from the coating layer  26 . The ring electrode is electrically connected with the carbon nanotube film  25 . 
         [0020]    The bared part  40  is a part of the metal conductive core  21  exposed from the first insulated layer  22 , the shield layer  23 , the second insulated layer  24 , the carbon nanotube film  25 , and the coating layer  26  in order. A length of the bared part  40  can range from about 0.5 millimeters to about 2 millimeters. The shape of the bared part  40  is spiral. The bared part  40  acts as an electrode head of the electrode lead  20 . In use, the bared part  40  contacts living cells and carries pulse current signals generated from the pulse generator  10  to the cells. The bared part  40  acts as both the stimulating electrode and the sensing electrode. The bared part  40  can be fixed to an organ and tissue to prevent the electrode lead  20  from sliding or falling off the organ and tissue. 
         [0021]    The metal conductive core  21  can be a hollow spiral structure with a certain elasticity to improve the lifetime of the electrode lead  20 . The hollow spiral structure is formed by twisting the linear shaped metal conductive core  21 . In one embodiment, the metal conductive core  21  is spirally twisted around a linear supporter, and then the linear supporter is removed to form the hollow spiral metal conductive core  21 . A diameter of a coil formed by the hollow spiral metal conductive core  21  can range from about 4 millimeters to about 6 millimeters. In one embodiment, the diameter of the coil is about 5 millimeters. A thread pitch of the hollow spiral conductive structure  21  can be in a range from about 0 millimeters to about 10 millimeters. In one embodiment, the thread pitch is about 0 millimeters. In other embodiments, the metal conductive core  21  is a linear structure with a solid structure or a hollow structure. 
         [0022]    The metal conductive core  21  has good electrical conductivity. A material of the metal conductive core  21  can be MP35N®, 35NLT®, stainless steel, carbon fiber, tantalum, titanium, zirconium, niobium, titanium alloy, copper, silver, platinum, platinum-yttrium alloy, or platinum-palladium alloy. MP35N® is an alloy including 35Co-35Ni-20Cr-10Mo, with a weight percentage of titanium being about 1% in the MP35N®. 35NLT® is also an alloy including 35Co-35Ni-20Cr-10Mo with a weigh percentage of titanium being about 0.01% in the 35NLT®. In one embodiment, the material of the metal conductive core  21  can be platinum. 
         [0023]    Materials of the first and second insulated layers  22 ,  24  can be silicone, polyurethane, polytetrafluoroethylene, silicone-polyurethane copolymer, polyethylene, polypropylene, polystyrene, polystyrene foam, or nanoclay-polymer composite material. The polymer material in the nanoclay-polymer composite material can be silicone, polyurethane, or polyolefin such as polyethylene or polypropylene. In one embodiment, the first and second insulated layers  22 ,  24  are made of polystyrene foam. The materials of the first insulated layer  22  and the second insulated layer  24  are not limited, as long as the first and second insulated layers  22 ,  24  can function as electrical insulators. 
         [0024]    The shield layer  23  shields electromagnetic interference or outer signal interference. A material of the shield layer  23  can be an electrical conductive material, such as metal or carbon nanotubes. In one embodiment, the shield layer  23  consists of copper. 
         [0025]    Referring to  FIG. 3 , the carbon nanotube film  25  is a free-standing film. The carbon nanotube film  25  includes a plurality of carbon nanotubes that can be arranged substantially parallel to a surface of the carbon nanotube film. A large number of the carbon nanotubes in the carbon nanotube film can be oriented along a preferred orientation, meaning that a large number of the carbon nanotubes in the carbon nanotube film are arranged substantially along a same direction. In the carbon nanotube film, 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 carbon nanotube film, and has a small if not negligible effect on the larger number of the carbon nanotubes in the carbon nanotube film arranged substantially along the same direction. 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 some carbon nanotubes located substantially side by side in contact with each other cannot be excluded. 
         [0026]    Referring to  FIG. 4 , a method for making the carbon nanotube film  25  can include: 
         [0027]    S 1 , providing a carbon nanotube array; and 
         [0028]    S 2 , selecting a carbon nanotube segment from the carbon nanotube array using a tool, and drawing the carbon nanotube segment at a predetermined speed, thereby pulling out a continuous carbon nanotube drawn film including a plurality of carbon nanotube segments joined end-to-end by van der Waals attractive force therebetween. 
         [0029]    In step S 1 , the carbon nanotube array is formed on a substrate. The carbon nanotube array consists of carbon nanotubes. The carbon nanotubes can be single-wall carbon nanotubes, double-wall carbon nanotubes, multi-wall carbon nanotubes, or any combinations thereof. Diameters of the carbon nanotubes can be from about 0.5 nanometers to about 50 nanometers. Lengths of the carbon nanotubes can be from about 50 nanometers to about 5 millimeters. In one embodiment, the lengths of the carbon nanotubes can be from about 100 micrometers to about 900 micrometers. In one embodiment, the carbon nanotubes are multi-wall carbon nanotubes, and the carbon nanotubes are substantially parallel to each other and substantially perpendicular to the substrate. 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. 
         [0030]    In step S 2 , the pulling direction can be substantially perpendicular to the growing direction of the carbon nanotube array. 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. This process of pulling produces a substantially continuous and uniform carbon nanotube film having a predetermined width. 
         [0031]    A method for wrapping the carbon nanotube film  25  around the second insulated layer  24  includes drawing a carbon nanotube film from a carbon nanotube array. One end of the carbon nanotube film is adhered to an outer surface of the second insulated layer  24 , and the carbon nanotubes in the carbon nanotube film substantially extend along the axial direction of the metal conductive core  21 . The carbon nanotube film or the metal conductive core  21  with the second insulated layer  24  is rotated to wind the carbon nanotube film around the outer surface of the second insulated layer  24 . The carbon nanotube film has a large surface, therefore the carbon nanotube film can adhere to the second insulated layer  24  by van der Waals force. In one embodiment, an adhesive layer is coated on the second insulated layer  24 , and then the carbon nanotube film is adhered to the second insulated layer  24  by the adhesive layer. 
         [0032]    The coating layer  26  can be fabricated by a biocompatible material, such as silicone or polyurethane. In one embodiment, the material of the coating layer  26  is polyurethane. 
         [0033]    A working process of the pacemaker  100  acting on a heart described below. The electrode lead  20  is implanted to the heart of a human with the bared part  40  used as the electrode head contacting the heart. The pulse signals are generated by the pulse generator  10  and transmitted to the bared part  40  to stimulate the heart. A heartbeat frequency or a series of heartbeat frequencies can be sensed by detecting potential differences between the bared part  40  and the pulse generator  10 . The potential differences are fed back to the pulse generator  10  to adjust the pulse signals to make the heart beat normally. 
         [0034]    The carbon nanotubes have excellent mechanical strength and toughness. Accordingly, the carbon nanotube film  25  consisting of the carbon nanotubes have excellent mechanical strength and toughness. If the electrode lead  20  is stretched by a drawing force, the metal conductive core  21  will be elongated along the stretching direction. The carbon nanotube film  25  wrapping around the metal conductive core  21  can prevent the metal conductive core  21  from breaking due to a friction force between the carbon nanotube film  25  and the metal conductive core  21 . Thus, the electrode lead  20  does not break easily under the same drawing force, and the electrode lead  20  is still electrically conductive. The mechanical strength, toughness, and life of the electrode lead  20  are improved. 
         [0035]    The carbon nanotubes in the carbon nanotube film  23  extend substantially along the extending direction of the metal conductive core  21 . The carbon nanotubes have good electrical conductivity along the extending direction of the carbon nanotubes because the carbon nanotube axial conductivity is excellent and the carbon nanotube axial conductive path is short. Therefore, the electrical conductivity of the electrode lead  20  can be improved. Thus, the sensitivity and the efficiency of the pacemaker  100  are improved. 
         [0036]    Referring to  FIG. 5  and  FIG. 6 , one embodiment of a pacemaker  200  is also provided. The pacemaker  200  includes a pulse generator  10  and an electrode lead  60 . The electrode lead  60  includes a proximal end and a distal end opposite to the proximal end. A connector  30  is at the proximal end the electrode lead  60 , and the bared part (not labeled) is the distal end of the electrode lead  60 . 
         [0037]    The electrode lead  60  includes the metal conductive core  21 , the first insulated layer  22  winding around the metal conductive core  21 , the carbon nanotube film  25  wrapping around the first insulated layer  22 , the second insulated layer  24  winding around the carbon nanotube film  25 , the shield layer  23  wrapping around the second insulated layer  24 , and the coating layer  26  winding around the shield layer  23 ; and the electrode lead  60 . A part of the carbon nanotube film  25  is exposed from the second insulated layer  24 , the shield layer  23  and the coating layer  26  in order. 
         [0038]    The electrode lead  60  can include a ring electrode (not shown) located on the exposed part of the carbon nanotube film  25 . The ring electrode is exposed from the second insulated layer  24 , the shield layer  23 , and the coating layer  26 . The ring electrode is electrically connected with the carbon nanotube film  25 . 
         [0039]    The electrode lead  60  can further include an electrode head  70  fixed on the bared part. The electrode head  70  is electrically connected with the electrode lead  60 . Thus, the electrode head  23  can be used to transfer the pulse signals produced from the pulse generator  10  to the organ of the human body, to stimulate the organ of the human body. 
         [0040]    A material of the electrode head  70  can be metal or alloy having an excellent conductivity, such as platinum-iridium alloy. A porous material to ensure biocompatibility can be coated on an outer surface of the electrode head  70 . In addition, the porous material can increase the contact area between the electrode head  70  and the human body, thereby increasing the sensitivity and sensing efficiency of the pacemaker. The porous material can be activated carbon, carbon fiber, carbon nanotubes, or titanium-nitrogen alloy. 
         [0041]    The electrode lead  60  can further include a fixture  50  located on the distal end of the electrode lead  60 . Thus, the fixture  50  can be opposite to and away from the connector  30 . A material of the fixture  50  can be a polymer, such as polyurethane or silicon rubber. The fixture  50  can include a fixing ring  51  and a plurality of fixing wings  52 . The fixing ring  51  can be a cylindrical structure. The plurality of fixing wings  52  can be rod-shaped. The plurality of fixing wings  52  forms a branch axis diverging from a center line or axis of the fixing ring  51 , to form a barb structure. A diverging direction deviates from the extending direction of the electrode lead  20 . An angle between the extending direction of each fixing wing  52  and the center line of the fixing ring  51  can be in a range from about 30 degrees to about 60 degrees. The fixture  50  can be fixed to the organ with the fixing wings  52  wrapped around by the fibrous tissue. The fixture  50  can also be a protrusion or helical structure as long as the electrode lead  20  can be tightly fixed to the organ by fibrous tissues. 
         [0042]    Other characteristics of the pacemaker  200  are the same as those of the pacemaker  100 . 
         [0043]    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. 
         [0044]    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.