Abstract:
A device which converts mechanical deformation in electrical current, these mechanical deformations are generated as a result of liquid pressure over a part of the device. This device is integrated within an implantable lead and inserted into the cardiovascular system of a patient. The purpose of the device is to charge a battery which stores energy for various uses of other implantable devices.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority to U.S. provisional patent application having Ser. No. 60/944,515, titled “Carbon Nano-tube Power Cell”, that was filed 17 Jun. 2007, which is incorporated herein by reference 
    
    
     BACKGROUND OF INVENTION 
     The present invention relates to a miniature power generating device suitable for implantation so as to generate power required by implanted medical devices. 
     While implantable medical devices, such as Pacemakers, ICD&#39;s and other grow in increasing sophistication, they all require a source of power. It is most convenient for the patient to implant a battery with the device to avoid the needs for leads to an external power source, which can be a source of infection, inflammation and the like. However, batteries have a limited life requiring eventual replacement, and or placing design constraints on the device power consumption and hence functionality such that it is much less than what might be achieved with a non-invasive device. 
     Hence there is a need for high density and high efficiency power generating cell that is bio-compatible for implantable medical device that either replaces or supplements a battery, being powered off energy generated by or available from the living organism. 
     SUMMARY OF INVENTION 
     In the present invention, the first object is achieved by providing a plurality of metallic carbon nanotubes (multiwalled or single walled) in contact with opposing electrodes in fluid communication between two flexible reservoirs containing an electrolytic fluid 
     At least about a portion of one of the two lobes that forms the dumb bells shaped device is in tactile communication with the blood, such that each pulse causes repeated contraction and hence pumping of the contained fluid through the carbon nano-tubes or channels to produce a charge. 
     The above and other objects, effects, features, and advantages of the present invention will become more apparent from the following description of the embodiments thereof taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic illustration of the flow with respect to the metallic nanotubes and electrodes in a portion of the nano-tube portion of device  100 . 
         FIG. 2  is a graph of flow induced voltage as a function of bias voltage for a prior art carbon nano-tube assembly. 
         FIG. 3  is a representative charging circuit for device  100 . 
         FIG. 4  is a partially cut away perspective view of a portion of the flow cell  400  of device  100 . 
         FIG. 5  is a cross-sectional elevation through the flow cell portion of the device  100  shown in  FIG. 5 . 
         FIG. 6  is a perspective cut away view of the carbon nano-tube portion of in the narrow waste section between the opposing fluid chamber in  FIG. 5 . 
         FIG. 7  are the results of a FEM model of displacement of the flexible portion of the operative devise in a 2-D plot corresponding to the section view shown in  FIG. 5 . 
         FIG. 8  are the results of a FEM model of the velocity field of the flexible portion of the operative devise in a 2-D plot corresponding to the section view shown in  FIGS. 5 and 7 . 
         FIG. 9  is a cross-section of a the central portion of another embodiment of the device. 
         FIG. 10  is a cross-section of an embodiment wherein any of the devices of  FIG. 1-9  is disposed at the end of a catheter or implanted lead. 
         FIG. 11  is a cross-section of an embodiment wherein any of the devices of  FIG. 1-9  is disposed within, for example a portion of a catheter or lead. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIGS. 1 through 11 , wherein like reference numerals refer to like components in the various views, there is illustrated therein a new and improved Carbon Nano-tube Power Cell, generally denominated  100  herein. 
     Conductive carbon nanotubes also known as metallic carbon nanotubes (MNT) either multiwalled (MWNT) or single walled (SWNT) in contact with flowing liquid provide a unique micro-fluidic system that offers a large interfacial area of intimate atomic contact between the liquid and the solid substrate. This can lead to a strong coupling of the free charge carriers in the nano-tube to the particles in the flowing liquid, more so if the liquid is polar or ionic in nature. 
     The effect of this coupling is expected to be further enhanced due to charge carrier entrainment because of the quasi-one dimensionality of the conducting nano-tubes. The effect of flow induced current in MWNT was shown by Kral P &amp; Shapiro, 2001, Phys. Rev. Lett, 86, 131 Recently, the flow of a variety of liquids over SWNT bundles was experimentally studied, and was found to generate voltage in the sample along the direction of the flow as taught by S. Ghosh, A. K. Sood, S. Ramaswamy, and N. Kumar; Flow-induced voltage and current generation in carbon nanotubes, Physical Review B 70, 205423, 2004, which is incorporated herein by reference. 
     Quite unexpectedly, however, the dependence of the voltage on the flow speed was found to be nonlinear, and could be fitted to a logarithmic form over five decades of the variation of the speed. 
       FIG. 1  is a schematic illustration of the nano-tube portion  11  of device  100  that utilizes the teaching of Ghosh et al. which can also be used as an experimental setup for measuring of the electrical current and voltage. SWNT bundles  105  prepared by arc discharge method are placed between two metal electrodes  111  and  112 . The nanotubes  105  are kept in their place by a supporting insulating substrate  106 . The same insulator  106  is also shown as being applied as a superstrate on the portion of the nanotubes  105  covered by electrodes  111  and  112 . This configuration is preferable in particular for stacking portions  11  as shown in  FIG. 6 . The electrical signal is measured along the flow direction (u L ) as shown in  FIG. 1  by arrow  10 . 
     The dependence of flow induced voltage and current fits to the empirical relations taught by Ghosh, supra. 
     
       
         
           
             
               
                 
                   U 
                   = 
                   
                     
                       U 
                       0 
                     
                     ⁢ 
                     
                       log 
                       ⁡ 
                       
                         ( 
                         
                           
                             u 
                             
                               v 
                               0 
                             
                           
                           + 
                           1 
                         
                         ) 
                       
                     
                   
                 
               
               
                 
                   ( 
                   1 
                   ) 
                 
               
             
             
               
                 
                   I 
                   = 
                   
                     
                       I 
                       0 
                     
                     ⁢ 
                     
                       log 
                       ⁡ 
                       
                         ( 
                         
                           
                             u 
                             
                               v 
                               0 
                             
                           
                           + 
                           1 
                         
                         ) 
                       
                     
                   
                 
               
               
                 
                   ( 
                   2 
                   ) 
                 
               
             
           
         
       
     
     Where v 0  is the reference flow velocity, u is the flow velocity, I 0  is the initially measured electrical current, U 0  is the initially measured voltage. Please note that both I 0  and U 0  are constant. 
     In experiments of others 1 M NaCl aqueous solution was used, this results in the flow induced voltage of U 0 =30 mV for v 0 =5×10 −4  m/s and 
               R   0     =         U   0       I   0       =   75           
Ω at L=0.5 cm, H=2 cm, h=70 μm.
 
     The total volume of the nanotube film was V 0 =7 mm 3 . 
     The flow-induced power is given by the formula 
     
       
         
           
             
               
                 
                   P 
                   = 
                   
                     IU 
                     = 
                     
                       
                         
                           U 
                           0 
                           2 
                         
                         
                           R 
                           0 
                         
                       
                       ⁢ 
                       
                         
                           ( 
                           
                             log 
                             ⁡ 
                             
                               ( 
                               
                                 
                                   u 
                                   
                                     v 
                                     0 
                                   
                                 
                                 + 
                                 1 
                               
                               ) 
                             
                           
                           ) 
                         
                         2 
                       
                     
                   
                 
               
               
                 
                   ( 
                   3 
                   ) 
                 
               
             
           
         
       
     
     The power generated per unit volume of the carbon nano-tube film is W=P/V 0 . 
     For example if u=1 cm/sec, then P=0.11 mW or W=16 μW/mm 3 . So, if for example the active volume of the device is 1 cm 3 , then the power of 16 mW could be generated. The maximum power that can be used for charging a battery is half of that value. 
     Ghosh et al. also considered the direction of the flow induced current with respect to the flow direction as a function of the bias voltage V B  (as shown in  FIG. 2  of the Ghosh reference, reproduced herein as  FIG. 2 ). This potential biases the SWNT with respect to the Au-reference electrode immersed in the flow chamber close to the sample as shown in the inset of  FIG. 2 . The dependence of the sign and the magnitude of the flow-induced voltage on V B  for an aqueous solution of 0.01 M KCl (conductivity 1.4 mS/m) and for a fixed flow speed of 0.04 cm/s are shown in  FIG. 3 . It is seen that the flow-induced signal is positive, i.e., I is anti-parallel to u when V B  is positive, and the sign of the signal is reversed, i.e., I is parallel to u, when V B  is negative. 
     Thus, for the current I to be parallel, (antiparallel) to u, the charge carriers in the nanotubes need to be holes (electrons). 
     When the nanotubes are biased positively, the anions Cl − , OH −  move closer to the SWNT, localizing holes on the carbon and making electrons available for flow-induced current. Similarly, holes are liberated when the bias is negative. As the bias voltage is increased the number of carriers participating in the flow induced current will increase as shown in  FIG. 3 . 
     In the experiment above the voltage increases more than 50 times for V B =0.5 V. Assuming that the power consumption by biasing the nano-tube film is much smaller than the power generated by the film itself we could write the maximum power generated from a unit volume of the carbon nano-tube film as: 
     
       
         
           
             
               
                 
                   
                     W 
                     max 
                   
                   = 
                   
                     
                       G 
                       2 
                     
                     ⁢ 
                     
                       
                         U 
                         0 
                         2 
                       
                       
                         R 
                         0 
                       
                     
                     ⁢ 
                     
                       
                         ( 
                         
                           log 
                           ⁡ 
                           
                             ( 
                             
                               
                                 u 
                                 
                                   v 
                                   0 
                                 
                               
                               + 
                               1 
                             
                             ) 
                           
                         
                         ) 
                       
                       2 
                     
                   
                 
               
               
                 
                   ( 
                   4 
                   ) 
                 
               
             
           
         
       
     
     Where G is the gain factor due to the biasing effect, For u=1 cm/sec and G=50 we get W max =20 mW/mm 3  of the device. 
       FIG. 3  is an electrical schematic diagram of the described flow induced power cell device  100 . As can be seen in  FIG. 3  above, the device  100  described in  FIG. 1 , has opposing electrodes  111  and  112  connected to opposing sides of diode bridge  110 , which is in turn connected to a battery  120  via the 2 remaining sides of diode bridge  110 . Thus, regardless of the direction of the electron flow (electrical current) between electrodes  111  and  112 , the current from the bridge  110  will always flow to charge the battery  120 . 
       FIG. 4  illustrates a schematic model of the flow cell  400  portion of the device  100 , which is optionally deployed as shown in other embodiments as an invasive, implantable power harvesting device. Flow cell  400  provides a means for the periodic flow of fluid that preferably contains ions, such as the aqueous KCl solution described above, over the nanotube portion and electrodes shown in  FIG. 1 . This model simulates the flow dynamics of liquids. The structure is comprised of an elastic, hermetically sealed, polymer shell (which is bio-compatible) composed of materials such as silicon, nylon etc. 
     Flow cell  400  preferably has a general dumb bell type shape as shown with each end being a substantially spherical or elliptical chamber or lobes,  401  and  402  the opposing chambers or lobes separated by a narrow neck or channel  415  containing the MNT&#39;s. As shown in  FIG. 4  this device  400  is inserted into a lead in such a way that one of the lobes of the device is exposed to the blood and the other side is left unexposed (positioned within the lead). The inner part  410  of the connected lobes  401  and  402  of device  400  is filled with an ionized liquid, such as aqueous solutions of various salts. Flow cell  400  may have other shapes than the dumbbell illustrated herein. 
     In the examples given, the wall  416  of the shell has a thickness of about 1.25 mm at the thinnest portion near the apex most distal from the channel  415  between the lobes. However, it should be appreciated that the wall thickness can be varied depending on the compliance of the material it is constructed from. 
     Pressure exerted over the exposed section or lobe of the flow cell  400  of device  100 , causes that part or lobe to contract, pushing the liquid within over the single walled carbon nano tubes (positioned in the center of the device—in darker grey), and expand the un-exposed section of the device. This flow of liquid over the single walled carbon nano tubes generates the electrical current required to charge the battery (the explanation regarding this physical phenomenon is described in greater detail above). 
       FIG. 5  illustrates a cross-sectional view of the device described in  FIG. 4 , the black section in the middle of the device contains the single walled carbon nano tubes, and the two “empty” holes at each side of the device contain the liquid which flows from one lobe of the device to the other. Two electrical leads are connected to two electrodes (in contact with the carbon nano tubes); please note that these electrodes do not interfere with the flow of liquid from one side of the device to the other and vice versa. 
       FIGS. 6A and 6B  illustrate one embodiment of the internal organization of the single walled carbon nano tubes in the device.  FIGS. 6A and 6B  are orthogonal sections of the stack of MNT films  105  and associated electrodes  111  and  112 , each forming device sub portions  11  of  FIG. 1 , being labeled  11 ,  11 ′,  11 ″ and  11  ′″ in this FIG. The common electrodes  111  of sub portions  11 ,  11 ′,  11 ″ and  11 ′ 41 , are connected in parallel via a bus electrode  121  for the common electrodes  111 . Another common bus would connect the opposite electrodes  112 . This stacked arranged provides subchannels  601  so that liquid can flow between each of lobes  401  and  402  of the fluid reservoir  400  of MNT device  100 . The nano tubes are preferably organized in a thin film structure, (several tens of microns thick) and are anchored to substrate  106  using various metals which act as the electrodes. On top of the electrodes another dielectric layer is deposited. This structure constitutes a single film or device portion  11 . 
     It should also be appreciated that a similar series of alternating channels between each layer of MNT and their respective electrodes  111 / 112  and a support substrate  106  can be forms in a essentially concentric arrangement formed by the helical rolling of a layer of MNT and electrodes disposes on a flexible substrate, as shown in section in  FIG. 9 , which is a section through a portion of channel  415 . In such a configuration a single wide sub-portion  11  is rolled in a spiral. As this sectional view section is at the electrode plane  112 , the nano-tube layer  105  does not appear in the drawing. To the extent that the nanotube layer  105  or electrodes  111 / 112  are not sufficiently flexible for rolling in a spiral, the rolling or bending can be performed on stripped sub-portion of substrate  106  not coated with electrodes and nanotubes. The advantage of this configuration however is that all the electrodes are already connected in the spiral pattern. In the case of using multiple folds the electrodes, such as  121  in  FIG. 6  can be added after folding. 
       FIG. 7  illustrates the deformation of the membrane (outer shell) as described above, when pressure is exerted over the outer shell of the lower lobe (which is effectively a membrane) causing liquid flow from one lobe of the device  400  to the other, as well as the reversed flow. The grey scale on the right represents the magnitudes of the displacement as mapped onto the now distorted device  400  in grayscale. The solid outline is the undistorted or equal pressure shape of device  400 . Deformation on the upper lobe results in deformation of the lower lobe, with minor deformation of the central connecting channel  415  wall. It is also apparent that volume of liquid in the bottom lobe increases as the volume in the upper lobe decreases. To the extent that such deformation in channel  415  would damage the MNT array structures or subportions  11 , the wall of the central connecting channel can be thicker than shown or reinforced with more rigid materials than the lobes  401  and  402 . 
       FIG. 8  illustrates the velocity flow field direction by a series of overlayed short arrows, which is the distribution of the velocity of the flow within the device is illustrated. The grey scale bar on the right represent the magnitude of the velocity; the maximum velocity is measured in the middle of the channel  415  (where the nano tubes  105  are located) and is calculated to be 1.4 cm/s using Finite Element Methods. 
       FIG. 10  illustrates a first embodiment of a structure and method of using device  100  as power generating cell or device for implantation in a human being or other living being. The periodic pressure of the pulse causes the cyclical compression and expansion of at least one lobe to force fluid through channel  415 , and hence generate current and charging battery  120 . The implantation can be temporary or permanent. Preferably at least one of the lobes, in this example the upper lobe  401 , is isolated from external pressure by the surrounding can  1020 . In contrast, the lower lobe  402  is subjected to the periodical pressure of the blood stream, being either the end of catheter or cardiac electrode lead  1000 , which supports can  1020 . Device  100  has electrode leads  1011  and  1012  are connected to the electrodes  111  and  112  on opposite sides of the MNT array  105  in channel  415 . 
       FIG. 11  illustrates an alternative embodiment of a structure and method of using device  100  as an implanted power cell. The catheter or lead upper portion  1000   a  contains the can  1020 , below which is an open or exposed portion  1025  for lobe  402  that connects to the lower catheter or lead portion  1000   b . However, the upper and lower portion  1000   a  and  1000   b  are connected around cavity or exposed portion. It should be understood that such exposed portion may also be a pliable membrane containing fluid that surrounds lobe  402 , or the wall of lobe  402  can form a portion of the pliable portion of the catheter/lead. 
     The description of the use of device  100  in a catheter or lead is illustrative, as it should be appreciated that device  100 , need not be in direct contact with blood, if the periodic pressure of the blood flow is transmitted to its location through other tissue or fluid. 
     While the invention has been described in connection with a preferred embodiment, it is not intended to limit the scope of the invention to the particular form set forth, but on the contrary, it is intended to cover such alternatives, modifications, and equivalents as may be within the spirit and scope of the invention as defined by the appended claims.