Research Objectives and Approaches: The objective of this research is to design flexible, multilayered polymer film power generators that convert cardiac motion into electrical power to recharge automatic implantable cardiac defibrillators and bi-ventricular pacemakers. The approach is to engineer the film thickness, crystalline and surface energy states, towards orders-of-magnitude enhancement in power output.

Intellectual Merit: While longevity of average congestive heart failure patients has increased to 15 years after implantation, batteries for the cardiac defibrillators and pacemaker are replaced every 4-5 years. This mismatch poses significant clinical and economic burden. Our hypothesis is that flexible, conformable poly(vinylidene fluoride) (PVDF) films containing many nanolayers (each 10-100 nm thick) can be embedded inside the current intra-cardiac leads to convert cardiac mechanical motion into electrical energy by exploiting the piezoelectricity of PVDF. The research tasks include designing a power generator made of PVDF films, characterization and optimization of energy generation, and determination of mechano-electrical coupling efficiencies.

Broader Impacts: This research paves the way towards the creation of robust, scalable, energy-relevant nanomaterials and implantable microsystems that capitalize upon with the extraordinary efficiency of the hearts contraction and relaxation. The findings will enable development of broad classes of tunable nanomaterials to tailor energy conversion characteristics with potential applications in energy efficient biochips. This project will be conducted at UT Austin and UT Health Science Center. Life scientists, engineering researchers, graduate and undergraduate students at both campuses will be trained in three key emerging areas of biomedical engineering, including biomedical microelectromechanical systems, nanomaterials and interventional cardiology.

Project Report

Implantable medical devices are severely restricted in application due to non-replenishable power sources. With the advancement in science, it is now possible to have replenishable energy generators that harvest energy from the living body. However, energy generator development is limited by its low charge density and voltage output. Our studies have focused on enhancing power generation from Polyvinyledenedifluoride (PVDF) films and development of processes for manufacturing flexible, high efficient PVDF nanomaterials. In structure aspect, multilayer structure with varied electrical connections is developed. Stacked thin films are connected in serial and parallel to verify the inner electrical connection configuration of multilayer device. What is the intellectual merit of this activity? Piezoelectric Nanogenerator presents a promising potential for commercial applications in areas such as self-powered sensor networks and implantable healthcare devices. Due to the increasing ratio of surface/interface area to the volume of nanocomposites, the surfaces and interfaces may have significant effects on the physical and mechanical properties of piezoelectric structures, especially the converted electrostatic potential. We have achieved the following advancement during this project: Multilayer PVDF film Multilayer PVDF-TrFE energy harvesting films have been made to maximize the energy harvesting capabilities. A multilayer film demo consisted of three layers of PVDF are fabricated to demonstrate the high voltage poling approach and inner electrodes configuration. The cross section of the multilayer structure is showed in the attached figure. Different PVDF multilayer electrode connections are showed. Output power is tested under same stress to demonstrate the electrode connection configuration and re-polling process. The output capacity test proved the output increase as PVDF layers increase. Test results showed that the interdigitated and parallel connection will enhance the charge output while serial connection cannot fully use the charges generated in the middle layers. Interdigitated connection required a much lower poling voltage than parallel connection. Nanoparticle decorated electrode We developed flexible thin-film energy generators based on gold nanoparticles doped PVDF-TrFE copolymer. The thin film characteristics can be well controlled by the manufacturing process involving the spin-coating and electrochemical deposition. We demonstrate that nanostructures in thin film piezoelectric materials increases charge collect area, leading towards enhanced power density and reversibility. Flexible substrate with doped nanoparticles presents a new class of platform for high efficiency, low-cost energy and sensing applications. Test results showed that gold particles modified harvester has a 30% higher charge output than conventional harvester with ITO electrode. What are the broader impacts of this activity? Incorporation of nanoscale materials into PVDF matrix has a profound effect on the crystallization behavior and crystalline morphology, which could lead to an improvement of piezoelectric and mechanical properties of polymers. The integration of a broad range of nanomaterials with thin films for efficient energy generators and sensors can be achieved.

National Science Foundation (NSF)
Division of Electrical, Communications and Cyber Systems (ECCS)
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Radhakisan S. Baheti
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University of Texas Austin
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