Abstract:
An implantable device having a power source is provided. The power source uses reverse electrowetting technology to generate a charge to power the implantable device. The power source includes a flexible, non-conductive substrate having a first side and a second side opposite the first side with a channel between the first and second sides. Electrodes are arranged about the channel in a predefined pattern. A liquid is contained in the channel. The liquid includes a dielectric liquid and a conductive liquid that do not mix. The electric change is generated by moving the liquid back and forth across the electrodes. The force to pump or move the liquid is provided by organic means, such as, for example, the change in blood pressure between systolic and diastolic, the expansion and contraction of an organ, or the movement of a muscle.

Description:
CLAIM OF PRIORITY UNDER 35 U.S.C. §119 
       [0001]    The present application claims priority to U.S. Provisional Patent  Application Ser. No. 61/697,030, filed Sep. 5, 2012, the disclosure of which is incorporated herein by reference as if set out in full. 
       CLAIM OF PRIORITY UNDER 35 U.S.C. §120 
       [0002]    None. 
       REFERENCE TO CO-PENDING APPLICATIONS FOR PATENT 
       [0003]    None. 
     
    
     BACKGROUND 
       [0004]    1. Field 
         [0005]    The technology of the present application relates generally to electrically charging devices implantable into animals, and more specifically, to using differential pressures generated by muscles, organs, and other tissue to electrically charge an implantable device. 
         [0006]    2. Background 
         [0007]    Vascular stents and other devices that are implantable into animals, such as people or the like, are used frequently to treat a medical condition. For example, a stent may be used to remove an aneurysm from direct contact with blood flow or the like. In another example, a pacemaker may be implanted to treat abnormal heart rhythms. In still other examples, electrical stimulators may be used stimulate and treat muscles or nerves, including such nerves as optical nerves, spinal nerves, and peripheral nerves. 
         [0008]    Many of the implantable devices suffer from one drawback or another. Implantable devices that require electrical energy, such as pacemakers or stimulators, require a battery in most instances. Eventually the battery is drained and must be replaced or recharged prior to the implantable device ceasing to operate as required to treat the condition. 
         [0009]    Stents, as mentioned, are effective in treating certain coronary and vascular diseases and conditions. Stents may facilitate or even cause the formation of thrombosis or clots once placed in the blood vessels. The clots may cause blockage or decreased blood flow that may lead to a stroke or heart attack. 
         [0010]    One solution to the formation of clots is to provide stents with anticoagulation pharmacologic agents (a.k.a. drugs). The anticoagulation drug, such as Heparin, is typically loaded in or coated on the stent. The medication is released from the stent over time and inhibits the formation of clots. While an improvement over a bare metal stent or the like, medicated, or eluting, stents still suffer from drawbacks. 
         [0011]    It has been discovered that the formation of clots on stents may be inhibited by providing a negative charge on the stent. In one solution, the negative charge on the stent is provided by implanting a battery along with the stent, which has the problems mentioned above. 
         [0012]    Thus, against the above background an improved system and method to electrically charge implantable devices is needed and, more particularly, an improved system and method to negatively charge a stent to inhibit clotting. 
       SUMMARY 
       [0013]    Embodiments disclosed herein address the above stated needs by providing an implantable device with an implantable power supply. The implantable power supply converting mechanical energy of the body, such as the expansion and contraction of muscles into electrical energy using microfluidics or mechanical strain. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a perspective view of a bare metal stent consistent with the technology of the present application; 
           [0015]      FIG. 2A-2C  is a cutaway series of figures showing the implantation of the bare metal stent and expansion of the stent from a collapsed to an expanded state; 
           [0016]      FIG. 3  is a view of a stent graft consistent with the technology of the present application; 
           [0017]      FIG. 4  is a cross section of a stent or stent graft of  FIGS. 1 and 3  consistent with the technology of the present application; 
           [0018]      FIG. 5  is an exploded view of a piezoelectric material usable with the stent or stent graft of  FIGS. 1 and 3 ; 
           [0019]      FIG. 6  is a block diagram of a stent or stent graft attachable to muscles, organs, or tissue consistent with the technology of the present application; 
           [0020]      FIG. 7  is a cross sectional view of a microfluidic device capable of converting mechanical energy to electrical energy consistent with the technology of the present application; and 
           [0021]      FIG. 8  is a plan view of the microfluidic device of  FIG. 7 . 
       
    
    
     DETAILED DESCRIPTION 
       [0022]    The technology of the present patent application will now be explained with reference to various figures, tables, and the like. While the technology of the present application is described with respect to certain devices implantable in animals, such as, vascular stents, pacemakers, and an electrical stimulation device, one of ordinary skill in the art would now recognize that the technology is applicable to other implantable devices that may require a charge or a power source. Additionally, the technology of the present application may be presented in reference to people; however, one of ordinary skill in the art on reading the disclosure contained herein will now understand that the technology may be usable in other animals, both wild and domestic. Moreover, the technology of the present patent application will be described with reference to certain exemplary embodiments herein. The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments absent a specific indication that such an embodiment is preferred or advantageous over other embodiments. Additionally, in certain instances, only a single “exemplary” embodiment is provided. A single example is not necessarily to be construed as the only embodiment. The detailed description includes specific details for the purpose of providing a thorough understanding of the technology of the present patent application. However, on reading the disclosure, it will be apparent to those skilled in the art that the technology of the present patent application may be practiced with or without these specific details. In some descriptions herein, generally understood structures and devices may be shown in block diagrams to aid in understanding the technology of the present patent application without obscuring the technology herein. In certain instances and examples herein, the term “coupled” or “in communication with” means connected using either a direct link or indirect data link as is generally understood in the art. Moreover, the connections may be wired or wireless, private or public networks, or the like. 
         [0023]    Referring first to  FIG. 1 , a stent  100  is shown. Stent  100  may generally be referred to as a bare metal stent. Stent  100  is formed of a number of interconnected metallic members  102  that form expandable structures  104  that may be elongated and compressed or expanded, as shown in expanded state  106 . As is generally known in the art, stent  100  may be loaded with pharmacological agents and/or covered with a flexible material, such as a flexible metal or polymer. With further reference to  FIGS. 2A-2C , a cutaway of an artery  202  having a partial blockage  204 , which may be plaque or the like, is shown. The stent  100  in a collapsed state  204  is delivered to the portion of the vascular anatomy via a catheter  206  and lumen  208  delivery mechanisms. The stent  100  is placed in the artery  202  such that the stent  100  extends from a proximal side  210  to a distal side  212  of the blockage. As shown in  FIG. 2B , an expansion device  214 , such as a balloon as shown, is provided on the catheter  206  to expand the stent  100  from the collapsed state  204  to an expanded state  106 , as shown in  FIG. 2C . The expansion device  214 , catheter  206 , and lumen  208  are removed to allow blood flow through the artery  202  as shown by arrow A. One of ordinary skill in the art would recognize on reading the disclosure that the stent  100  may be deployed in numerous locations throughout the vascular system. 
         [0024]    The bare metal stent  100  is typically associated with a coronary artery and blockage. With reference to  FIG. 3 , a stent graft  300  is shown in multiple configurations. The stent graft  300  typically comprises a fabric  302  supported by a rigid structure  304 . The fabric  302  is elastic and the rigid structure  304  has bends  306  to allow the rigid structure  304  to straighten as the stent graft  300  is expanded. The stent graft  300  may be used in endovascular repair procedures, such as, for example, an aneurysm repair. 
         [0025]    As described above, stent  100  and stent graft  300  may develop blood clots that may lead to blockage in the vascular system resulting in a heart attack, stroke, or the like. As described above, blood clot formation may be inhibited by negatively charging the stent  100  or the stent graft  300 . Heretofore, a battery may be provided directly connected to the stent or electromechanically connected to the stent, see for example, United States Published Patent Application Publication No. 2006/0106451, the disclosure of which is incorporated herein as if set out in full. Using an independent battery adds the difficulty of (1) implanting the battery, (2) connecting the battery to the stent, (3) the life of the battery to name but three difficulties. 
         [0026]    A piezoelectric material develops charge or electrical energy in response to applied mechanical stress. Piezoelectricity or the piezoelectric effect is a linear electrometrical interaction between the mechanical and the electrical states in certain materials. Placing a strain on the piezoelectric material causes the generation of a charge. The reverse piezoelectric effect is by applying a charge to the material similarly causeing a mechanical strain. 
         [0027]    Certain polymers develop electrical charges under strain. The piezoelectricity effect generally relates to placing a strain on the polymers when the polymers are flexed or stretched. One exemplary type of stretchable polymer is a polyvinylidene fluoride (PVDF). With reference to  FIG. 4 , a cross section of a charge generating stent  400  is provided. Charge generating stent  400  may be either a bare metal stent  100  or a stent graft  300  as explained above. If stent  400  includes a bare metal stent  100 , as shown, a flexible layer of a piezoelectric polymer  402  is provided. If stent  400  is a stent graft  300 , the fabric  302  may be replaced by the piezoelectric polymer  402  or, in certain embodiments, the piezoelectric polymer  402  is layered on the fabric  302 . In either case, the piezoelectric polymer  402  is provided on the stent  400  in such a way as to provide a negative charge on the interior layer  404  as it has been found that the negative charge on the interior layer of the stent  400  inhibits the formation of clots and the like. As a corollary, the outer layer  406  may be provided with a positive charge relative to the internal layer as compared to the inner layer of stent  400 . The charge on the piezoelectric polymer  402  is generated by the blood pressure expanding and contracting the blood vessels, including the stent  400 . The expansion and contraction generates strain on the piezoelectric polymer  402  that in turn generates the negative charge on the interior layer  404  of the stent  400 . 
         [0028]    PVDF has a number of drawbacks that are generally known in the art. Thus, while it is possible to use PVDF to generate a negative charge on the interior layer of stent  400 , alternative power sources are desirable. One promising material is a flexible piezoelectric structure disclosed in United States Published Patent Application Publication Number 2011/010923A1, filed Mar. 19, 2010, and incorporated herein by reference as if set out in full. In one embodiment, as shown in  FIG. 5 , the piezoelectric includes first and second flexible substrates  505 ,  515 . For use with devices designed to be implanted to animals, the flexible substrates should be formed of biocompatible materials that are generally known in the art. The flexible substrates  505 ,  515  have an external side  505   x,    515   x  and an internal side  505   i,    515   i.  A plurality of piezoelectric film strips  510  may be coupled to the internal side  505   i  of one of the flexible substrates  505 . Suitable piezoelectric film strips  510  may be constructed from crystalline piezoelectric materials such as, for example, lead zirconate titanate, zinc oxide, Quartz, and the like as are generally known in the art. Flexible conductive electrodes  520 A and  520 B may be coupled to the internal side  515   i  of the other flexible substrate  515 . The flexible conductive electrodes may be formed on flexible substrate  515  using any number of conventional depositing techniques. The plurality of piezoelectric film strips  510  form an electrical circuit across the electrodes  520 A,  520 B. In certain embodiments, the flexible substrates  505 ,  515  form a protective biocompatible capsule for the electrical circuit. 
         [0029]    The flexible piezoelectric, shown in  FIG. 5 , provides an improvement in the generation of an electrical charge over the PVDF piezoelectric previously known. However, the generation of power by the piezoelectrics using differences in systolic and diastolic pressure is limited. Additional power may be provided if the flexible material was implanted into a muscle that has stronger expansion and contraction pressure or, alternatively, an organ. For example, larger strains may be implemented if the flexible piezoelectric is implanted into the lungs, the diaphragm, the heart, or other muscle, organs, or tissues that expand and contract. As shown in  FIG. 6 , a flexible piezoelectric  600  may be adapted for attachment to tissue  602 , such as a muscle or organ. In certain instances, the muscle or organ may be the heart, the diaphragm or the lungs to name but three options. Leads  604  may extend from the electrodes, such as electrodes  520 A,  520 B above, to the implanted device that requires power. The leads may be coaxial style leads, twisted pair leads, or the like. The leads  604  may connect to a stent, such as stent  100 , or a stent graft, such as stent graft  300  to provide a negative charge to the stent. In other embodiments, the leads  604  may supply a charge to rechargeable batteries, such as, for example, batteries associated with a pacemaker or a nerve stimulator to name two examples. 
         [0030]    While piezoelectric devices provide a useful source of electrical energy, the body has a limited ability to place strain on materials. Alternatively, it may be possible to use the expansion and contraction of organs, tissue, muscles, and the like, and/or the change in pressure of the vascular system to provide mechanical energy that is convertible to electrical energy using reverse electrowetting technologies. In other words, the reverse electrowetting structure explained herein is a means for generating an electrical charge to power, at least in part, implantable devices. The expansion, contraction, pressure differentials, or the like may be used to provide pumping action for microfluidic devices built into the implantable device, or separate from the implantable device and connected by electrical leads. One possible microfluidic device  700  is shown in  FIGS. 7 and 8 , and as disclosed in U.S. Pat. No. 7,898,096, which issued Mar. 1, 2011, and which is incorporated herein by reference as if set out in full. As shown in  FIGS. 7 and 8 , planar substrates  702  are provided separated by spacers  704  to form a channel  706  or space. Substrates  702  and spacers  704  should be formed of a dielectric or non-conductive material. A plurality of electrodes  708  are arranged about the channel  706 . Leads  710  complete the electrical circuit to the implantable device  712 , which may be a stent, pacemaker, stimulator, batteries, or the like. The microfluidic device  700  may directly power implantable devices or provide a continuous charge to prolong the life of the implantable device. 
         [0031]    A movable fluidic body  703  is disposed in channel  706  and configured to slide along channel  706  past electrodes  708 . Fluidic body  703  consists of two immiscible liquids, one being a dielectric liquid and the other one being an electrically conductive liquid. Examples of suitable electrically conductive liquids include aqueous salt solutions and molten salts. Exemplary aqueous salt solutions include 0.01 molar solutions of salts such as CuSO.sub.4, LiCl, KNO.sub.3, or NaCl. Exemplary molten salts include 1-ethyl-3-methylimidazolium tetrafluoroborate and 1-ethyl-3-methylimidazolium trifluoromethanesulfonate, which are both commercially available. In other cases, the conductive liquid can comprise liquid metals such as gallium, indium or mercury. Examples of suitable dielectric liquids include silicone oils and alkanes. Exemplary silicone oils include polydimethylsiloxane and polydiphenylsiloxane, and exemplary alkanes include nonane and heaxadecane. 
         [0032]    Conductive and dielectric liquids are spatially separated in a plurality of distinct regions. Dielectric liquid regions  714  and conductive liquid regions  716  are arranged in a periodic alternating pattern, such that conductive and dielectric regions regularly alternate. The boundaries between immiscible liquid regions are preserved by the surface tension forces, giving fluidic body  103  an ability to move as a whole, e.g. slide along channel  202  without disturbing the arrangement and volume of the above-mentioned distinct liquid regions. 
         [0033]    The pumping action to move the fluidic body  103  may be provided by the change between systolic and diastolic blood pressure, the expansion and contraction of muscles, the expansion and contraction of the lungs, or other tissues, organs, and the like. As the fluidic body  103  moves past the electrodes  708 , the mechanical energy is converted into electrical energy to power or charge the implantable device  712 . 
         [0034]    Those of skill would further appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention. 
         [0035]    The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.