Three University of St Thomas engineering students and their professor have been working for several months to create something revolutionary: an implantable device that would capture energy from the beating of a heart and turn it into electrical power to run a device such as a pacemaker.
The students - Austin Lorch '18, Amanda Tenhoff '18 and Milad Audi '19 - are developing a system that uses energy-harvesting technology to improve battery life and simultaneously measure multiple vital signs, including heart and respiration rates. And all it entails is a magnet moving inside of a coil - which is harder to achieve than it sounds.
"With further development, this system has the potential to eliminate the need for batteries in implantable cardiac devices and can provide continuous or near-continuous diagnostic data streams to improve overall patient monitoring and treatment outcomes," said Dr. Tom Secord, assistant professor and former Medtronic mechanical engineer. "Two other research groups have published results using different approaches to this problem, but our approach is promising and unique in that it adjusts to different heart rates - at rest (sedentary) or exercising (active)," he said.
The idea for the implantable energy harvester technology started with a Faraday flashlight, which is powered by shaking it. A magnet passes back and forth through a coil of wire and creates an electric current. Secord presented the idea to his researchers and they got to work. In their prototype, a magnet oscillates back and forth (because of opposite end magnets on either side) within a cylinder of ¼-inch diameter.
"We wanted to develop the technology so we could replace a pacemaker battery without appreciably increasing the overall pacemaker size," Secord said.
Implantable cardiac sensors, such as pacemakers, tend to focus on only one vital sign (e.g., heart rate from EKG). But the full suite of vital signs includes heart rate, respiration rate, temperature and blood pressure, which the St. Thomas prototype will provide one day soon. With a viable prototype the researchers are drafting a journal article for submission to the IEEE Transactions on Biomedical Engineering journal.
All this lab work and research were possible because of Secord, who earned his graduate degree from Massachusetts Institute of Technology in Cambridge. Prior to joining St. Thomas in 2016, Secord spent six years at Medtronic working on the development and testing of transcatheter heart valves. His work at Medtronic encompassed many aspects of structural design, accelerated testing and regulatory approval for implantable devices.
When his project at Medtronic was concluding, Secord saw it as a great opportunity to pursue an academic career. He was pleasantly surprised by what he discovered at St. Thomas because "unlike many other schools, St. Thomas highly valued the experience of someone coming from industry," he said.
Secord leads the research team of Lorch, Tenhoff and Audi. The three mechanical engineering majors are enthused about working with Secord in the Lab for Biomedical Robotics and Mechatronics at St. Thomas, where they created and experimented individually and collaboratively.
Lorch, from Andover, Minnesota, said he was excited by the potential for his family and friends to have prolonged and improved lives through the research he conducted.
"I found this project thrilling because it was aimed at solving an issue that almost everyone has a connection to," he said. "An even cooler thought is that our work has the potential to impact the lives of those across every part of the globe. It is awesome to be focused on the heart, as it is one of the most central and crucial components of every human being."
Lorch, who started on the project in January, created a model of a heart's left ventricle and left atrium, the optimum location for the device because of the muscular nature of the ventricle and its attendant motion.
"I chose to 3-D print the mold, because it would be impossible to machine the mold considering its intricate geometry," Lorch said. To create the mold, he made a computerized 3-D model of the heart from CT image data from an actual patient.
"It was our goal to make the silicone model accurate to a specific patient to show the testing would be replicable for not only a generic model, but for individualized patients," Lorch said. "Essentially, the patientspecific silicone model will give credibility to our case for the tunable resonance device to be used in real-life situations."
To mimic heart muscle, a specific silicone was chosen and poured into the mold, creating a malleable left ventricle and atrium. The model was then actuated to replicate the motion of a human heart beating (at various beats per minute). Tenhoff's work provided the needed beat.
Tenhoff began her research - her third project at St. Thomas - last spring. Her main job this time was working on simulation with imaging to analyze heart motion. The Eagan, Minnesota, native said she enjoyed the research because it's what she wants to do after graduation.
"My dream is to be able to use my engineering skills to work with, heal and improve the human body and the lives of the people who would be receiving the medical treatment," she said. "This is my first step to being able to do that. In particular, I love this project because of the variety of different sub-projects in it: computer-aided design, programming, electrical wiring and building mechanical parts are all key components to this project, and all of us have the opportunity to try out any of it."
Her project goal was to create an accurate 3-D pumping heart model. To prepare, she spent last spring using programs that would allow her to read and manipulate 4-D CT scans, which illustrate the movement of the heart through the entire cardiac cycle.
"We successfully created a 3-D model of the heart on the computer and created a 'point cloud' of data that describes the topography of the heart," she said. "By comparing the topography of the heart at its smallest size to that at its biggest, we can roughly calculate how the heart moves."
During the summer, she wrote code in MATLAB, which analyzes the point cloud data and calculates how much the heart expands and contracts over its cycle, pinpointing places where it moves the most. With the silicone heart created and Tenhoff's beat info, the main component was still missing - the prototype of the energy harvester that included a magnet moving inside of a coil.
Audi also wants to work in the biomedical engineering field. Having completed two research projects already at St. Thomas, he chose the heart research because, "It was awesome! I was paid to learn and contribute to an important project at the same time," he said.
He wanted to work with Secord because of his work at Medtronic. "He knows a lot about biomedical engineering and about control systems. Both of these are things that I want to learn, and one of the best ways to learn is by working with someone who knows what they are doing," said Audi, who is from Crystal, Minnesota.
His part of the project, which he began in June, involved creating a device to implant on the heart, capture energy from the beating of the heart and turn it into electrical power to run a device such as a pacemaker. Audi made multiple prototypes with various coil and magnet parameters to find the most efficient one.
The fabrication process involved 3-D printing, winding coils and soldering wires. Audi systematically refined coil designs to find the best combination of factors to maximize power, such as using different lengths, different wires and different diameters. To test his prototypes he uses Simulink, a computer program, in conjunction with a physical system that simulates heart motion. He helped build a final prototype that attached to the silicone heart while it was beating.
"Hopefully one day the device will actually be in use and helping people," Audi said.
Source and top image: University of St Thomas
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