There are known numerous attempts to deploy in a human heart a piezoelectric source of energy harvesting electrical power in response to the heart movement in order to provide the power supply for pacemakers and other implantable devices.
Already in 1969 a piezoelectric converter of body motion into electrical energy for driving implants in the form of a completely encased piezoelectric cantilever beam was introduced in U.S. Pat. No. 3,456,134, though no way to deploy the container with the beam was described. An obvious disadvantage of this system is the insufficiency of the energy collected by a piezo-element encapsulated in a container to drive a pacemaker as it reacts only on its own derived movement and not on the muscle's. Another difficulty was the requirement for it's implantation inside the heart.
In 1972 it was suggested in U.S. Pat. No. 3,659,615 to use a piezoelectric bimorph encapsulated and implanted in the chest cavity or adjacent to the left ventricle of the heat, with flexing in reaction to muscular movement used to generate electrical power. The patent is mainly devoted to epicardial devices and to their coverage with synthetic or natural materials. A main disadvantage of such an approach is the great surgical impact resulting from the surgical intervention. Also, the life time of epicardial leads is very short, requiring additional surgical interventions.
U.S. Pat. No. 4,690,143 discloses a self-contained power source mounted in a pacing lead in order to generate electrical power for operating the pacing lead. A distinguishing feature of the technology described in this patent is the mounting of the power generation device in a pacing lead comprising a catheter which is inserted intravenously into a human heart. The power is collected while the lead is bending during the heart muscle contraction. The main disadvantages of the system include insufficient power generation for the overall pacemaker functioning by the piezo-element encapsulated in the lead because it reacts only to the derived movement of the lead and not on the muscle itself. Moreover, any movements of objects mounted inside the heart relative to the heart itself are potential sources of thrombus formation.
Further application of piezo-electric power generation to pacemakers was to connect a piezoelectric transformer to power a lead-based sensor, see U.S. Pat. No. 7,203,551 and an energy transmission system, containing a piezo-electric transducer, from an external unit generating magnetic field or acoustic waves to recharge a pacemaker battery, see U.S. Pat. No. 5,749,909. Also, in U.S. Pat. No. 5,431,694 a bio-operated piezo-electric generator in the form of a flexible sheet of poled polyvinylidene fluoride attached in surface-to-surface contiguity with a skeletal number, is proposed to be connected to a pacemaker. The generated AC is rectified to C, which is supplied to the battery on demand. Needless to say that these architectures only make the artificial in body structures and surgical interventions more complicated.
The further progress of piezoelectric technologies, see for example patents U.S. Pat. No. 5,835,996, U.S. Pat. No. 6,655,035B2, US 2005/0052097A1, US 2005/0082949A1, permits one to build highly efficient piezoelectric generators. For the development of piezoelectric transformers, see U.S. Pat. No. 6,707,235 patent and the literature cited there.
The latest state of the art technologies are presented in the following patents:                WO 2010/070650 A1 discloses a piezoelectric generator for low frequency based on a standard bimorph piezoelectric bending energy generator scheme, but does not produce enough energy for in-body appliances. Also, the use of a cantilever beam with a mechanical energy harvesting unit together encapsulated into a closed box, possess the drawbacks of the same kind as described above for U.S. Pat. Nos. 3,456,134 and 4,690,143        US 2010/0076517A1 presents a technology based on a bundle of piezo-electric fibers arranged around a core conductor. The authors state that, when the bundle is deformed, at least one fiber will be deformed sufficiently to generate sufficient energy for the pacemaker or other selected device. This idea does not differ from that behind U.S. Pat. No. 4,690,143. Consequently, it is not possible to get 20 mW and not more then 50-100 μW can be harvested using such a configuration.        WO 2007/1068284 A1 contains a broad description of the possible applications of the energy harvesting technologies inside and outside the heart. The piezo-electric part is under-developed and is citing the work of Roundy, 2003 where 200 μW were produced from 1 cm cube of the cantilever beam at 120 Hz frequency, considerably less than the 20 mW at 1 Hz needed from, at maximum, a 0.3 cm cube. Consequently, the drawback is of the same kind as in the technology described in WO 2010/070650 A1.        
Modern batteries can supply the power for pacemakers for 5-7 years and thus there is no real need for additional energy sources inside the heart, however the two-fold architecture containing a pacemaker itself, with the battery implanted outside the heart and pacing leads inserted intravenously into the heart propose certain inconveniences.
The present invention addresses a widely recognized need to eliminate complicated two-fold or even three-fold in-body structures, which cause obvious problems to patients, thus minimizing surgical procedures and providing patients with a lifetime source of energy feeding a pacemaker.
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USPTO Backgrounds