The present invention relates to the field of piezoelectric nanogenerator. The present invention, in particular, relates to a self-rechargeable system for battery charging consisting of nanomaterials incorporated piezoelectric system as nanogenerator and a rechargeable battery to replace the classical non-chargeable Li-ion batteries used in the pacemakers.
DESCRIPTION OF THE RELATED ART:
[002] The traditional cardiac pacemaker batteries are made up of Lithium (Li) ions. These lithium based batteries, such as, the lithium / iodine-polyvinylpyridine batteries are non-rechargeable and thus, need to be replaced approximately, every 8-10 years depending on the requirements of the patients. For example, a complete heart block patient requires continuous pacing, which consumes more power, hence reduced battery life while sporadic bradycardia patients require intermittent pacing and hence, consume less power, and therefore more battery life. Further, these batteries occupy ~ 50% of the volume of the pacemakers, making them bulky. Capacitor is one of the key components of implantable pacemakers and cardiac resynchronization therapy pacemakers (CRT-Ps), that stores the electrical energy to pace the heart. The surgical procedures involved in replacing these batteries are traumatizing to the patients.
[003] Self-rechargeable batteries will eliminate replacement surgeries and, thus will significantly improve the quality of life of the patient. In recent years, efforts have been made for self-recharging of pacemaker battery to avoid the unnecessary surgery to replace the battery.
[004] Publication No. US9026212 relates to apparatus, systems and methods for harvesting energy from bio-kinetic events to power various implanted medical devices. One embodiment provides an energy harvesting mechanism for a cardiac pacemaker comprising an energy converter and a signal path component. The energy converter is positionable inside a human body and configured to generate electric power signals in response to a bio-kinetic event of the human body such as a heartbeat, respiration or arterial pulse. The converter can comprise a piezoelectric material which generates electricity in response to mechanical deformation of the converter. The converter can also have a power generation characteristic that is matched to the frequency of the bio-kinetic event. For heart beat powered applications, the power generation characteristic can be matched to the physiologic range of pulse rates. The piezo electric fibers are of a sufficient number and arrangement such that when bundle is deformed in a given direction, at least one fiber will be deformed sufficiently to generate sufficient energy for the pacemaker.
[005] Patent No. US5810015 relates to an implantable apparatus which includes a power supply capable of converting non-electrical energy such as mechanical, chemical, thermal, or nuclear energy into electrical energy. The invention also provides a method of supplying energy to an electrical device within a mammalian body in which the mammal is implanted with an apparatus including a power supply capable of converting non-electrical energy into electrical energy, and non-electrical energy is transcutaneously applied to the apparatus. A rectifier network is coupled to the piezoelectric devices of chamber and provides an electrical signal to EESD. The valves are operated together in response to control signals from controller.
[006] Patent No. US4690143 relates to a catheter distal end portion which has a piezoelectric device therein and which is adapted to be inserted into a human heart. The device can be a ceramic bimorph or can be made of polyvinylidene fluoride film for generation of electrical energy upon contraction of the heart. The piezoelectric device is designed to generate electrical energy in response to movement of the implanted pacing lead and in the preferred embodiment is incorporated into the wall of the catheter of the lead as a longitudinal or spiral configured strip of film having piezoelectric properties.
[007] Patent No. US3659615 relates to an encapsulated non-permeable piezoelectric self-powered pacesetter for implantation in an in vivo, or living, system in which the pacesetter is sealed and enclosed in an envelope formed of medical grade silicone rubber and preferably natural or synthetic animal, plant or insect wax, in which a piezoelectric poly-crystalline ceramic is completely embedded, enclosed or housed to function as a mechanical to electrical energy converter, when implanted near moving muscle in a living system, and without connection with a separate source of electrical energy either within or without the living system.
[008] Patent No. US8311632 relates to the power generator for converting mechanical energy to electrical energy including a compressible element adapted and configured to be placed in an environment having a variable compressive force such as varying ambient pressures. The compressible element may be compressed by a force applied by the variable pressure to the compressible element. The power generator may further include a transducer that may be coupled to the compressible element and that may convert mechanical energy from the compression of the compressible element to electrical energy. In some embodiments, the power generator may be adapted to be an implantable power generator for converting mechanical energy from a patient to electrical energy, such that the compressible element adapted and configured to be placed between two adjacent tissue layers of the patient and to be compressed by a force applied from the two adjacent tissue layers to the compressible element.
[009] Publication No. EP1964161 relates to an electrical generator including a substrate a semiconductor piezoelectric structure having a first end and an opposite second end disposed adjacent to the substrate, a first conductive contact and a second conductive contact. The structure bends when a force is applied adjacent to the first end, thereby causing an electrical potential difference to exist between a first side and a second side of the structure. The first conductive contact is in electrical communication with the first end and includes a material that creates a Schottky barrier between a portion of the first end of the structure and the first conductive contact. The fist conductive contact is also disposed relative to the structure in a position so that the Schottky barrier is forward biased when the structure is deformed, thereby allowing current to flow from the first conductive contact into the first end.
[010] Publication No. KR20160117793 relates to a piezoelectric nano-generator device and a method of manufacturing the same. The piezoelectric nano-generator device includes: a first electrode formed on a substrate; a second electrode formed on the first electrode; and a piezoelectric nano-structure layer and a nitrogen compound layer formed between the first and second electrodes. Since the piezoelectric nano-structure layer and the nitrogen compound layer are formed between the first and second electrodes, an electric potential barrier gives more improved reliability to the electrodes, so that leakage current may be restrained from flowing through an inside. The accumulation of charges to the electrodes is improved and crystallinity and piezo-electricity of a piezoelectric material are improved when the piezoelectric nano-structure layer and the nitrogen compound are sequentially epitaxy-grown, so that an improved piezoelectric output is provided.
[011] Publication No. US2011275947 relates to a method and implant suitable for implantation inside a human body that includes a power consuming means responsive to a physiological requirement of the human body, a power source and a power storage device. The power source comprises a piezoelectric assembly that is configured to generate an electrical current when flexed by the tissue of the body and communicate the generated current to the power storage device, which is electrically coupled to the power source and to the power consuming means.
[012] Publication No. CN205564817 relates to a little energy system of nanometer piezoelectricity including the upper substrate down in proper order, going up electrode, dielectric layer, bottom electrode, piezoelectricity nano-material, infrabasal plate on the follow, upper substrate, last electrode, dielectric layer and bottom electrode constitution dielectric electric capacity, piezoelectricity nano-material is located between infrabasal plate and the dielectric electric capacity, power (resulting from the dissipation mechanical energy of collecting) the quilt that comes from the outside is transmitted piezoelectricity nano -material and makes the material produce deformation, under positive piezo electric effect's effect to produce the electric energy. This little energy system of nanometer piezoelectricity not only can reduce the leakage current, improves nanogenerator's efficiency, can also save the produced electric energy of nanogenerator, and external firm output is in succession given with electrical apparatus or the higher outside storage device of energy density again in needs. The invention little energy system of nanometer piezoelectricity is through novel structural design, has realized that efficient electricity generation, conversion, storage, output are as an organic whole.
[013] Patent No. US4798206 relates to self-contained, self-powered, flexible electrical control signal generating means are located in the right ventricle of a heart and generate electrical control signals solely by mechanical movements caused by actions of and conditions in the heart without any electrical connection to and supply of electrical energy from any other power source which electric control signals are transmitted to a control circuit system of an implanted control unit which control unit transmits an electrical signal to a stimulation electrode implanted in tissue at the apex of the right ventricle of the heart which stimulation electrode uses the electrical signal to stimulate the heart.
[014] Patent No. US10398904 relates to apparatus, systems and methods for harvesting energy from bio-kinetic events to power various implanted medical devices. One embodiment provides an energy harvesting mechanism for a cardiac pacemaker comprising an energy converter and a signal path component. The energy converter is positionable inside a human body and configured to generate electric power signals in response to a bio-kinetic event of the human body such as a heartbeat, respiration or arterial pulse. The converter can comprise a piezoelectric material which generates electricity in response to mechanical deformation of the converter. The converter can also have a power generation characteristic that is matched to the frequency of the bio-kinetic event. For heart beat powered applications, the power generation characteristic can be matched to the physiologic range of pulse rates.
[015] Publication No. US2016346556 relates to materials and systems that enable high efficiency conversion of mechanical stress to electrical energy and methods of use thereof are described herein. The materials and systems are preferably used to provide power to medical devices implanted inside or used outside of a patient's body. The materials and systems are capable of being bent, folded or otherwise stressed without fracturing and include piezoelectric materials on a flexible substrate.
[016] Publication No. US3456134 relates to a piezoelectric converter for converting motion to electrical energy and has particular reference to an improved converter assembly to convert body motions into electrical energy for the driving of electronic implants such as a pacemaker machine.
[017] Publication No. US2009171404 relates to devices and systems for generating energy for powering implanted medical devices such as a pacemakers and defibrillators. The devices and systems of the invention are biocompatible and are suitable for use with active implanted medical devices, such as a pacemakers and defibrillators, and also with ventricular assist devices, muscle stimulators, neurological stimulators, cochlear implants, monitoring devices, and drug pumps.
[018] Patent No. US7729768 relates to implantable cardiac motion powered piezoelectric energy sources are provided. An aspects of embodiments of the subject implantable energy sources is that they include a piezoelectric transducer that converts cardiac mechanical energy to electrical energy.
[019] Patent No. US8344597 relates to a nano-converter capable of directly generating electricity through a nanostructure embedded in a polymer layer experiencing differential thermal expansion in a stress transfer zone. High surface-to-volume ratio semiconductor nanowires or nanotubes (such as ZnO, silicon, carbon, etc.) are grown either aligned or substantially vertically aligned on a substrate. The resulting nanoforest is then embedded with the polymer layer, which transfers stress to the nanostructures in the stress transfer zone, thereby creating a nanostructure voltage output due to the piezoelectric effect acting on the nanostructure. Electrodes attached at both ends of the nanostructures generate output power at densities of ~20 nW/cm2 with heating temperatures of ~65° C. Nanoconverters arrayed in a series parallel arrangement may be constructed in planar, stacked, or rolled arrays to supply power to nano- and micro-devices without use of external batteries. The CNT and Pt contacts are deposited upon a SiO2 insulator atop a Si substrate that acts as gate to the CNT field effect transistor (FET). The Si substrate is in turn electrically connected to a voltage source to control the CNT FET.
[020] Patent No. US10199560 relates to methods, systems, and devices for implementing a stretchable nanoparticle-polymer composite foams that exhibit piezoelectric properties. In one aspect, a nanoparticle-polymer composite structure includes a curable liquid polymer; piezoelectric nanoparticles; and graphitic carbons. Because of its electrical and mechanical properties, PVDF can be applied to a wide range of applications including non-volatile low voltage memory, hydrophones and acoustic transmitters, and implantable medical devices. The CNTs in these composites can enhance the stress transfer from the polymer to the BTO nanoparticles.
[021] Patent No. US8680751 relates to a generator that includes a bio-compatible substrate onto which one mechanical generating unit. A plurality of elongated piezoelectric fibers each have a first end that is in electrical communication with a first electrode and an opposite second end that is in electrical communication with a second electrode. An insulating layer covers the first electrode, the second electrode and the elongated piezoelectric fibers. A third electrode and a fourth electrode are each disposed on the bio-compatible substrate opposite from the mechanical generating unit. A proton conducting member is in contact with both the third electrode and the fourth electrode. A glucose catalyzing enzyme is electrically coupled to the third electrode. An oxidase enzyme is electrically coupled to the fourth electrode. A layer of soft epoxy polymer is coated on the carbon fiber as an insulator, then two gold electrodes are patterned onto it and coated with carbon nanotubes (CNTs), followed by immobilization of glucose oxidase (GOx) and laccase to form the anode and cathode, respectively.
[022] Patent No. US10602939 relates to an interface structure for a biological environment including at least one composite electrical impulse generating layer comprising a matrix phase of a piezo polymer material, a first dispersed phase of piezo nanocrystals, and second dispersed phase of carbon nanotubes, the first and second dispersed phase presented through the matrix phase. The piezo polymer material and piezo nanocrystal convert mechanical motion into electrical impulses and accept electrons to charge the composite impulse generating layer. The carbon nanotubes provide pathways for distribution of the electrical impulses to a surface of the composite impulse generating layer contacting the biological environment. The carbon nanotubes further provide for the delivery of the byproducts of the free radical degradation from the biological environment to both piezo-nanocrystals and piezo-polymer.
[023] The article entitled “Implantable physiological power supply with PVDF film” by E. Häsler , L. Stein & G. Harbauer, Journal Ferroelectrics Volume 60, 1984 - Issue 1, 08 Feb 2011 talks about a miniaturized prototype with solid electrical and mechanical contacts designed. The physical characteristics of the device and the first results of an animal experiment are discussed. With improved PVDF films, a power converter with a film mass of a few g could supply implanted electric systems with a power of 1 mW.
[024] The article entitled “A flexible and implantable piezoelectric generator harvesting energy from the pulsation of ascending aorta: In vitro and in vivo studies” by Hao Zhang; Xiao-Sheng Zhang, Xiaoliang Cheng, Yang Liu, Mengdi Han, Xiang Xue, Shuaifei Wang, Fan Yang, Smitha Ankanahalli Shankaregowda, Hai-Xia Zhang, Zhiyun Xu, Nano Energy 12, January 2015 talks about the feasibility and efficacy of generating electric power utilizing the pulsating energy of ascending aorta with a flexible and implantable piezoelectric generator (PG) through in vitro and in vivo studies. In the in vitro study, the max output voltage (Vmax), current (Imax) and power (Pmax) of the PG were 10.3 V, 400 nA and 681 nW respectively. The quantity of electric charging by one pulse was about 7–9 nC. Factors affecting its output performance were investigated with single variable experiments.
[025] The article entitled “Piezoelectric response of aligned electrospun polyvinylidene fluoride/carbon nanotube nanofibrous membranes” talks about the effects of the presence of carbon nanotubes (CNT) and optimized ES parameters on the crystal structures and piezoelectric properties of aligned PVDF/CNT nanofibrous membranes. The optimal ß content and piezoelectric coefficient (d33) of the aligned electrospun PVDF reached 88% and 27.4 pC/N; CNT addition increased the ß-phase content to 89% and d33 to 31.3 pC/N. The output voltages of piezoelectric units with aligned electrospun PVDF/CNT membranes increased linearly with applied loading and showed good stability during cyclic dynamic compression and tension. PVDF fibrous membranes were prepared through ES as three sample types of randomly oriented PVDF fiber mat, well-aligned PVDF fiber mat, and well-aligned PVDF fiber mat with added CNT. The influence of the rotating collector and conductive additives on the ß phase content and piezoelectricity of PVDF were investigated.
[026] The article entitled “Ferroelectric polymer PVDF-based nanogenerator” by Jeongjae Ryu, Seongmun Eom, Panpan Li, Chi Hao Liow and Seungbum Hong, intechopen, June 27th 2019 talks about the development of ferroelectric polymer polyvinylidene fluoride (PVDF)-based nanogenerators. It first introduces PVDF and its copolymers, and briefly discusses their properties. Then, it discusses fabrication methods, including solution casting, spin coating, template-assisted method, electrospinning, thermal drawing, and dip coating. Using these methods, a wide variety of ferroelectric polymer structures can be fabricated. In addition to the performance enhancements provided by fabrication methods, the performance of PVDF-based nanogenerators has been improved by incorporating fillers that can alter the factors affecting the performance. Next, we review energy sources that can be exploited by PVDF-based nanogenerators to harvest electricity. The abundant energy sources in the environment include sound, wind flow, and thermal fluctuation.
[027] The present invention aims to provide a self-rechargeable battery system using piezoelectric polymeric materials to convert mechanical energy to electrical energy emanated with every systole-diastole movement of the heart into electrical energy, to refuel itself. The self-rechargeable batteries of the pacemaker are connected with leads having piezoelectric materials, which are capable of harvesting mechanical energy to use it as electrical energy. Naturally, they make the pacemakers self-sustainable and, in the process, eliminate the need and cost for their surgical replacement every 8-10 years. More importantly, these batteries will completely extirpate the physical distress and mental trauma associated with such repeated surgeries during battery replacements. Further, the battery size is substantially reduced, leading to smaller size of the whole pacemaker device. Therefore, this self-rechargeable battery system will be consequential in pacemaker evolution.
OBJECTS OF THE INVENTION:
[028] The principal object of the present invention is to provide a self-rechargeable battery system using piezoelectric polymeric materials to convert mechanical energy to electrical energy emanated with every systole-diastole movement of the heart into electrical energy, to refuel itself.
[029] Another object of the present invention is to provide enhanced efficacy as the material used to make the film is standardized to produce similar voltage as required to pace the heart.
[030] Yet another object of the present invention is to eliminate the need for surgeries to replace discharged pacemakers.
[031] Another object of the present invention is to standardize the material used to make the self-re-chargeable pacemaker batteries, hence contributed towards improving the quality of existing pacemakers. The size of battery, used in pacemaker, is much smaller than the existing ones. The present invention, makes pacemakers significantly lighter, compact and thinner than the existing ones also.
[032] Still, another object of the present invention is to decrease the overall cost of pacemakers by eliminating the need of surgeries required for the replacement of discharged pacemaker batteries. Also, these self-rechargeable films are made up of low-cost polymers, hence it again adds up to the cost-effectiveness of the overall device.
[033] Another object of the present invention is to provide ease of use as existing clinical practices are sufficient enough to support the implantation of the pacemaker with this battery system without any additional care and precaution. The polymeric sheathing is used to the existing leads which is easy to use.
[034] Yet another object of the present invention is to increase the shelf life of the pacemaker to many folds.
BRIEF DESCRIPTION OF THE INVENTION:
[035] The present invention relates to a self-rechargeable battery system consisting of nanomaterials incorporated piezoelectric system as nanogenerator and a rechargeable battery to replace the classical non-chargeable Li-ion batteries used in the pacemakers. The piezoelectric system is essentially a piezoelectric polymeric mat attached to a full-wave bridge rectifier and a voltage multiplier. The rectified and modulated voltage from the piezoelectric system is fed to the rechargeable battery. Nanomaterials are incorporated as second phase reinforcement material to piezoelectric mat to enhance its electrical and piezoelectric properties. The piezoelectric system converts mechanical energy arising from the movement of the heart to electrical energy and concomitantly generate voltage to replenish its charge used in running the pacemaker. In order to fabricate the components, the piezoelectric nanogenerator is devised by optimizing its polymer composition, its incorporation in the leads and its subsequent integration with the pace maker battery to make it self-rechargeable. The polymer is reinforced with suitable nanomaterials to improve electrical and mechanical properties of the nanogenerator.
[036] The voltage required to contract the ventricles or to pace the human heart varies from person to person, ranging from 0.25mV – 1.5mV, and in some cases, it can go upto5mV.The voltage generated by the system is enough to power a rechargeable battery. However, suitable voltage multipliers can be employed to increase the output voltage to many folds. Since the system is made up of light-weight, flexible polymeric materials, the system becomes conformable and non-bulky adding ease for patients to live with.
[037] The assembly of the piezoelectric polymeric film wrapped lead and tines and rechargeable battery can be used in patients suffering from bradycardia or irregular heartbeats. This invention overcomes the shortcoming of traditional pacemaker batteries. Patients get rid of unnecessary repeated surgery for the replacement of discharged pacemaker batteries. Other than that, this rechargeable power source can be used in any battery-operated biomedical device such as implantable cardioverter defibrillator (ICD’s), cardiac resynchronization therapy (CRT’s)etc. to eliminate the need of replacement of discharged battery. Further, due to continuous replenishment of energy, the size of rechargeable battery can be much less, causing reduced discomfort due to the presence of the pacemaker device.
BRIEF DESCRIPTION OF DRAWINGS
[038] It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered for limiting of its scope, for the invention may admit to other equally effective embodiments.
[039] Figure 1 shows schematic showing pacemaker (a) and nanogenerator placements (b) around the pacemaker leads and (c) over the tip of electrode;
[040] Figure 2 shows methodology of process involved;
[041] Figure 3 shows optical image of reinforced polymer nanogenerator;
[042] Figure 4 shows schematic for the electrical connections to evaluate the applications of the nanogenerator;
[043] Figure 5 shows comparison of conductivity of polymer with and without different nanofillers using solvent casted/ electrospun mat;
[044] Figure 6 shows piezoelectric experiment;
[045] Figure 7 shows (a) Stress vs voltage curve of the samples; (b) table demonstrating the voltage generated by different samples at different values of stress applied;
[046] Figure 8 shows (a) voltage generated by PVDF CNT aligned sample when it was, pressed, twisted, stretched normally and stretched fully; (b) the intensity of LED increases as the amount of stress on the nanogenerator increases;
[047] Figure 9 shows heart prototype: (a) the circuit diagram of the prototype and the actual digital images of heart prototype depicting (b) relaxation and (c) expansion of balloon.
DETAILED DESCRIPTION OF INVENTIONS:
[048] The invention provides a self-rechargeable battery system consists of a piezoelectric system and a rechargeable battery. The piezoelectric system is essentially a piezoelectric polymeric mat attached to a full-wave bridge rectifier and a voltage multiplier. The rectified and modulated voltage from the piezoelectric system will be fed to the rechargeable battery. The voltage required to contract the ventricles or to pace the human heart varies from person to person, ranging from 0.25mV – 1.5mV, and in some cases, it can go upto5mV. In the system, nanomaterials are incorporated as second phase reinforcement material to piezoelectric mat to enhance its electrical and piezoelectric properties. When a pressure of 0.25mmHg - 0.12 mmHg (0.033 kN/m2 to 0.015 kN/m2)(equivalent to that of the blood pressure in arteries) is applied on a 1cm2 patch of designed nanogenerator using the heart prototype, it generates voltage at a rate of around 1.5mV per minute. Further, the system is able to generate a voltage of 6 mV using low load tensile test instrument at 0.8 KN/m2pressure and is capable of producing a voltage of 0.5 Volts. The capacity of the nanogenerator, fabricated in present invention is 2.160 mAh. The voltage generated by the system is enough to power a rechargeable battery.
[049] This invention involves designing of a self-rechargeable battery system for pacemakers (1) using piezoelectric polymeric materials that can convert mechanical energy to electrical energy. The components included are the mechanical energy harvesting unit and the rechargeable battery. In order to fabricate these components, the piezoelectric nanogenerator is devised by optimizing its polymer composition, its incorporation in the leads and its subsequent integration with the pace maker battery to make it self-rechargeable. The polymer is reinforced with suitable nanomaterials to improve electrical and mechanical properties of the nanogenerator.
[050] The invented piezoelectric polymer film is placed on the endocardium of the ventricles and/or around the leads of the pacemaker as a sheathing, so that it can utilize the mechanical energy from the cardiac motion to produce a corresponding voltage (electrical energy) as shown in figure 1. This is stored in the rechargeable battery. The system is schematically illustrated in figure 1. The pacemaker along with the self-re-chargeable battery (1) is fitted outside the heart and the leads (2) of the pacemaker are passed through the right atrium to be opened up in right ventricle. The tip of the electrode has tines (3) which are attached to the myocardium. Two electrodes go co-axially within the lead, which are sheathed both internally and externally by insulating layers (4). The fabricated layer of nanogenerator is wrapped over the leads (2) of the pacemaker electrode. This way the layer of nanogenerator (5) harvests the mechanical energy generated by the haemodynamic flow and convert it into electrical energy. The nanogenerator layer is further covered by a layer of insulating material (4) as shown in figure 1(b). In addition, piezoelectric nanogenerator sheet is wrapped all around the tines of the tip (3), in case of passive electrode, as shown in figure 1(c). As the tines come out and attach to the myocardium, the layer of nanogenerator (6) spreads over the myocardium. This causes the nanogenerator to move in sync with cardiac contractions and relaxations. Piezoelectric property of the polymer used converts this into electrical energy. This energy is used to charge the rechargeable battery attached with the pacemaker. Therefore, using the polymeric nanogenerator in the suggested way, a regular pacemaker (1) can be upgraded to a self-rechargeable one. This will eliminate the need for additional surgery to replace discharged pacemakers.
[051] The proposed nanogenerator is fabricated out of piezoelectric polymer, reinforced with suitable nanoparticles. Solvent casting and electrospinning are the two main techniques used for the fabrication of polymeric mat. The polymer solution and the preparation of nanocomposite is done as per the schematic shown in figure 2. In solvent casting, the polymer solution is placed in suitable glass mould and cured at specific temperature. While in electrospinning, the polymer solution is deposited into a nanofibrous mat. With proper electrical connections, the parameters such as voltage, distance and flow rate are optimized based on the choice of the polymer.
[052] Evaluation of the electrical property of the polymeric nanogenerator.
[053] The designed polymeric piezoelectric nanogenerator is meant to convert mechanical energy to electrical energy. Thus, as mentioned earlier, the polymeric mat is reinforced with suitable nanomaterials capable of imparting/improving its electrical conductivity. In order to make electrodes, aluminum film is pasted on both sides of the sample which is glued by using conducting tape. Wires are then connected with these electrodes to check the electrical properties as shown in figure 3.
[054] The nanogenerator converts mechanical energy to electrical energy, so the conductivity of the nanogenerator is evaluatedby making two electrodes on either side of the polymeric mat. A full wave bridge rectifier is connected with the polymeric mat that converts the AC voltage generated by the nanogenerator to DC voltage, thereby eliminating the noise and unnecessary fluctuations, as shown in figure 4.
[055] The electrical conductivities of the reinforced and non-reinforced mats are evaluated by connecting the sample to source meter and measuring the desired parameters. The conductivity of semiconductors ranges from (103 to 10-8) S/m. Figure 5 depicts the electrical conductivity of all the samples. As shown in figure 5, PVDF with aligned CNT exhibits the highest electrical conductivity of 0.12 S/m (in case of electrospun mat) and 0.10 S/m.
[056] Evaluation of mechanical property of the polymeric nanogenerator.
[057] In one of the embodiments, the polymeric nanogenerator is implanted by wrapping it around the pacemaker lead. In another embodiment, the polymeric nanogenerator is implanted either as a patch on the endocardium or as a combination of both the embodiments. Under these conditions, it is exposed to certain levels of mechanical and hemodynamic forces. As per J. Michael Lee and Derek R. Boughner [Circ. Res. 1985;57;475-481], the normal end-diastolic stress for human pericardium is in the range of 19-57 kN/ m2 (0.019 MPa-0.057 MPa) and the maximum stress on the human pericardium walls can go upto140 kN/m2 (0.14 MPa). Also, the systolic and diastolic blood pressure in the arteries ranges from 0.033 kN/m2 to 0.015 kN/m2. A low load tensile tester is used to evaluate the mechanical property of the proposed polymeric film. The PVDF incorporated with aligned CNT can bear a stress of 0.33 MPa (330 kN/m2). This is much higher than the stress that human heart experiences, both the blood pressure and the pericardium pressure, showing mechanical stability of the film under proposed application. Therefore, it is pertinent that the mechanical property of this polymeric mat is evaluated to ensure that it can withstand the prolonged exposure to these physiological forces.
[058] Evaluation of piezoelectric property of the polymeric nanogenerator
[059] The salient feature of the fabricated polymeric nanogenerator is its ability to harvest mechanical energy and generate electrical energy. Therefore, its piezoelectric property is evaluated, as illustrated in the figure 6. The sample is connected to the holder of low load tensile tester. An electrical connection is established between the sample and the source meter. Sinusoidal mechanical pulses of pre-defined amplitude and frequencies are applied to the sample through low load tensile tester and corresponding voltage is recorded in the source meter.
[060] The voltage generated by the setup shown in figure 6 is plotted against stress applied and the graph is shown in figure 7(a). Voltage generated by the different samples is proportional to the strength of the sinusoidal mechanical pulses (plotted as stress along y-axis in figure 7(a) and demonstrated in the form of table in figure 7(b)). Hence, the piezoelectric characteristic of the polymeric nanogenerator is confirmed. Also, the PVDF with aligned CNT shows maximum output voltage at same amount of applied stress, suggesting better piezoelectric properties when compared to other samples.
Table 1

[061] Since, the PVDF CNT aligned sample has shown superior piezoelectric properties, the voltage generated by the polymeric mat under various mechanical forces such as pressing, twisting and stretching is measured as shown in figure 8(a). Further, a capacitor (100 µF, 50 V) and a rechargeable cell (1.2 V) are also charged by the voltage generated by proposed nanogenerator. Apart from this, an LED is also powered by this nanogenerator, and it started glowing. It is noted that as more and more pressure is applied on the nanogenerator, more amount of voltage is generated and hence, the intensity of light of LED increases as shown in figure 8 (b).
[062] Heart prototype
[063] Finally, the functional efficacy of the polymeric nanogenerator is evaluated in a heart prototype, illustrated in figure 7. It consisted of a stepper motor and a transformer to apply pulsating voltage to the water pump. This switched the pump ON or OFF corresponding to the pulsating voltage applied by stepper motor. The pump is placed in a water reservoir to pump water into the balloon (intended to serve as heart in this model) to inflate it. During the OFF cycles, balloon deflated sending the water back to the reservoir. In this way, through the motorized inflation and deflation of the balloon, the contraction and relaxation of heart is mimicked. The nanogenerator is attached to the surface of the balloon and electrically connected to the source meter. A pressure sensor is placed over the balloon to measure the pressure applied on its walls from within during inflation and deflation. A rechargeable cell is connected to the nanogenerator to store the voltage generated due to the mechanical movement of the balloon. The voltage generated is converted from AC to DC mode using a full wave rectifier before reaching into the rechargeable cell. 1.5mV of voltage per minute was generated when a pressure of 0.016 – 0.033 kN/m2was appliedusing the heart prototype. A single pacing of human heart can be done with a voltage ranging from 0.25 – 1.5mV (maximum 5mV) and the capacity of a pacemaker battery is 1.25V. So, considering the voltage generation by the nanogenerator, it takes 13.8 hours to fully recharge a completely discharged pacemaker battery. By incorporating voltage multiplier,the amount of voltage generated in a single cycle is enough for a single pacing of a normal human heart and the charging rate increases.
[064] Numerous modifications and adaptations of the system of the present invention will be apparent to those skilled in the art and thus it is intended by the appended claims to cover all such modifications and adaptations which fall within the scope of this invention.

WE CLAIM:

1. A flexible and biocompatible charging system (1) capable of harvesting the mechanical energy of human cardiac and blood circulatory system and convert it to electrical energy wherein the charging system (1) comprises pacemaker along with the self-re-chargeable battery (1) fitted outside the heart; the leads (2) of the pacemaker passed through the right atrium to be opened up in right ventricle; tip of the electrode has tines (3) which are attached to the myocardium. two electrodes go co-axially within the lead, which are sheathed both internally and externally by insulating layers (4) characterized in that the fabricated layer of nanogenerator is wrapped over the leads (2) of the pacemaker electrode so that the layer of nanogenerator (5) harvests the mechanical energy generated by the haemodynamic flow and convert it into electrical energy wherein the nanogenerator layer is further covered by a layer of insulating material and piezoelectric nanogenerator sheet is wrapped all around the tines of the tip (3), in case of passive electrode and as the tines come out and attach to the myocardium, the layer of nanogenerator (6) spreads over the myocardium which causes the nanogenerator to move in synchronization with cardiac contractions and relaxations.
2. The flexible and biocompatible charging system as claimed in claim 1 wherein the polymeric nanogenerator (5) is implanted by wrapping it around the pacemaker lead (2).
3. The flexible and biocompatible charging system as claimed in claim 1 wherein the polymeric nanogenerator (6) is implanted as a patch on the tines of the electrode (3).
4. The flexible and biocompatible charging system as claimed in claim 1 wherein the nanogenerator layer is further covered by a layer of insulating material (4).