STEM is taught and conducted by Dr. Crowthers. STEM 1 is a class where you get to embark on a 6 month independent research project centered around either a research question, engineering need, or mathematical conjecture. Throughout the journey, you learn and acquire key information about communication with professionals in your field, reviewing scientific literature, and writing your own project documents. After months of research and data collection, the final product of your project is presented at a fair in February, from where you can potentially advance all the way up to the international science fair.
My project developed an optimized piezoelectric power harvester to power a pacemaker through a multiphysics simulation software. This project aimed to extend the battery life of the pacemaker to 10 or more years. You can scroll below to see some of my work.
Pacemakers are implantable biomedical devices that regulate the pacing of the heart. However, The lithium-ion battery that it operates on only contains a lifespan of approximately 5-7 years, requiring the patient to undergo a surgical procedure for the replacement of the battery. As this increases the potential risk of infection, this project utilized an alternative source of energy: piezoelectrics, specifically the lead zirconate titanate (PZT) material. Since piezoelectrics generate voltage when they undergo mechanical stress, also known as the piezoelectric effect, they were used to construct a power harvester that would operate based on the vibrational frequency of the heart to provide power output for the pacemaker for at least a time period of 10 years before the piezoelectric deteriorates. Three different prototype designs of piezoelectric materials were made through CAD using the SolidWorks software where each design had a contrasting geometry to the conventional rectangular piezoelectric. The prototypes were then imported to the COMSOL Multiphysics software for its simulation and were tested alongside capacitors, resistors, and bridge rectifiers with varying amounts of stress that emulate the vibrational frequency that would be acquired from the heart, cyclic loadings, and loading frequencies for optimized power output, minimized degradation ratio, and minimized volume. The output voltage exceeded the amount of voltage required by a pacemaker: 0.1-15 volts and The degradation ratio was higher than 0.8, indicating that the power harvester lost only 20% efficiency in outputting power over its 10+ year lifespan, deeming it to be suitable to work alongside a lithium-ion battery. As this design is a low-frequency power harvester, it can be utilized for low-application devices that also run on lithium-ion batteries.
Keywords: piezoelectric power harvester, piezoelectric effect, pacemaker, mechanical stress, resonant frequency, COMSOL Multiphysics
Current lithium-ion batteries are not sufficient for a pacemaker device to run for an extended period of time, requiring a surgical procedure for battery replacement every 5-7 years which poses many risks to the patient.
The goal of this project is to engineer a more-efficient power harvesting system that can fulfill the needs of a pacemaker to run for at least 10 years or more before the piezoelectric material deteriorates.
More than three million people in the United States are diagnosed with Arrhythmia, a condition where the pacing of the heartbeat becomes abnormal due to the insufficient electrical impulses being provided by the heart (Bhatia, 2018). To resolve this issue, pacemakers have been considered as the main form of treatment for the reduction of symptoms, with over 200,000 devices being implanted every year just in the United States (Bhatia, 2018). The device itself is highly effective in functionality, however the predicament is the lifespan of this biomedical device. With a battery life of only 5-7 years, patients are required to undergo surgery once the battery is drained out, posing potential risks to their physical health such as infection at the site of implant, blood clots (thromboembolism), and collapsed lungs (Mulpuru et al., 2017). The proposed plan is to build a piezoelectric framework that would be able to sustain the lifespan of a pacemaker for an extended period.
This project conducted all design, development, and testing computationally. The design prototypes for the piezoelectric PZT plate were designed using Computer-Aided Design (CAD) using the SolidWorks software. The design protypes were tested and analyzed through the COMSOL software, which is a software utilized for Multiphysics simulation. Within COMSOL, the micro electromechanical systems (MEMS), computational fluid dynamics (CFD), and structural mechanics modules were used to test and analyze the piezoelectric power harvester. In order to apply certain characteristics to the power harvester, the Solid Mechanics, Electrostatics, and Electrical Circuit physics were applied.
Load in Newtons provided by the Vibrational Frequency of the Heart
Graph of Output Voltage
Rate of Voltage Degradation from Power Harvester
Graph of Eigenfrequency based on Varying Compression Levels
This study aimed to design and developed an optimized piezoelectric power harvester that would satisfy the energy requirements of a pacemaker. In order to optimize the voltage output of the piezoelectric, multiple physics modules were utilized in the COMSOL Multiphysics software to transform the piezoelectric: Eigenfrequency, Solid Mechanics, and Electrical Circuit. The preliminary work consisted of constructing the 2 prototypes in SolidWorks. These geometries differed from the conventional rectangular piezoelectric plate that can only be compressed one way, whereas the prototype geometries would be able to handle compression and as well as torsion, which would aid with the eigenfrequency.
This study was conducted for the betterment of the pacemaker in the long term, and prioritized the voltage output of the piezoelectric power harvester, the degradation ratio, and the volume of the piezoelectric. The study showed promising results that could potentially make the power harvester implantable in the future.