3D-mapping wireless power for neural implants

Wayne Gillam

Usman Khan, an undergraduate student at the University of Washington, is helping to engineer wireless charging systems for neural implants by developing a 3D visualization of the electromagnetic fields wireless power devices generate.

Before Usman Khan’s freshman year at the University of Washington (UW) even started, his academic interests began to broaden from his declared major in physics to encompass electrical engineering. It was a visit to the lab of Center for Neurotechnology (CNT) member, Joshua Smith, that initially piqued Khan’s curiosity.

“When I first came to the UW and got started, I took a class, a short program before fall quarter started. That was taught by an electrical engineering professor. He took us on a tour of a bunch of different labs, and I saw Josh’s Sensor Systems Lab,” Khan said. “I thought that was pretty cool. So, as the year went on, I was studying physics, but I was noticing that the engineers were making some really cool stuff. I wanted to see what kind of research opportunities there were in that area.”

Fast forward three years later, and Khan is now a junior in the UW Department of Electrical & Computer Engineering, working in the Sensor Systems Laboratory on a CNT-affiliated research project that blends his interests in physics and engineering. Last summer, Khan began “3DEVS: a 3D Electromagnetic Visualization System for the Design and Analysis of Wirelessly Powered Neural Implants.” He worked under supervision by mentor, Gregory Moore, a CNT member and UW graduate student, and alongside Tri Nguyen, a CNT Research Experience for Undergraduates participant. With encouragement and support from the CNT, Smith, and Moore, Khan is continuing to develop the project throughout the school year, building on what he and Nguyen worked on over the summer.

“It has been a pleasure working with Usman and Tri,” Moore said. “With their concerted efforts, the project moved from conceptual design to an operational tool. This reconfigurable testbench allows for rapid prototyping of antennas and mapping of [electromagnetic] fields, which accelerates our research progress.”

How wireless power for neural implants works

Like any electronic device, such as a cell phone, neural implants designed for medical applications require a steady, reliable power source in order to operate. Most biomedical implants in existence today, such as a heart pacemaker, use long-lasting batteries as their power source. The batteries have a duration measured in years, but eventually, an invasive surgery is required to access the device and replace them. This exposes patients to surgical risks. A promising alternative is wirelessly recharging batteries, which would enable the implanted device to remain in the body indefinitely. This method of recharging devices is noninvasive and could be done at any time, such as when the user is sleeping.

Wireless charging systems for neural implants work by using magnetic fields devices emit to move power from a charger outside the body to a device inside the body. A good knowledge of physics is needed to understand how the magnetic fields interact with each other, as well as engineering know-how, to construct devices that can optimize magnetic field interaction for safe and efficient wireless charging.

Drawing a 3D map of electromagnetic fields

One of the daunting challenges engineers face is how to clearly describe the invisible magnetic fields neural implants generate in order to inform and optimize device design. The magnetic fields can be described mathematically, but because of the complexity of the equations involved with neural implants, it simply isn’t practical to describe the fields in this way. Khan’s system helps to address this challenge by providing a practical and useful method for both measuring and visualizing the magnetic field behavior of a wireless charging system.

A researcher or engineer can plug a wireless power device into Khan’s 3D-visualization system, which will take a series of scans, collecting precise data on the device’s power efficiency. That data is then plotted and mapped to create a 3D image of the electromagnetic field the device is generating. This is essentially making invisible magnetic fields visible to the naked eye. The visual map can then be used to further develop, analyze and debug the wireless device.

“Without the 3D map, it’s like trying to design [a wireless power device] blind. It’s like if I asked you to draw a picture, and you have a blindfold on. You can kind of draw it, sort of, but you can’t really tell what you are doing,” Khan said. “The system I designed is to visualize wireless power efficiency through the magnetic field. Why are we visualizing the magnetic field? Because that’s the medium through which the power moves.”

Using the map to create efficient and safe wireless power systems

Over the next year, Khan plans to explore how machine learning techniques could be applied to data the 3D-visualization system collects to create simplified mathematical models of wireless charging systems for neural implants. This could be a powerful tool for engineers and researchers, given that design and analysis of these systems is mathematically challenging. Khan’s 3D map will enable them to not only see the electromagnetic fields wireless charging systems generate, but also create useful models of the systems themselves.

Khan’s 3D-visualization system also has the potential to provide experimental metrics for absorbed energy, which would be useful for designing implants that are safe and will not damage surrounding brain or body tissue.

“One possibility [for the 3D-visualization system] is to collect what are called ‘SAR measurements.’ SAR stands for ‘specific absorption rate.’ It’s a metric to know how much electromagnetic energy your biological tissue, your body is absorbing,” Khan said. “For example, if you have a cell phone, and you are holding the cell phone to your ear, for that thing to be approved [for use], someone will have to do some measurements to make sure those electrical signals are not harming your body, because to some extent, something will be absorbed by your body. You have to make sure it’s not a harmful amount.”

Because wireless power is foundational to creating functional, useful and practical neural implants with medical applications, Khan’s work has the potential to contribute to a wide array of CNT research projects aimed at developing viable wireless communication and interface designs. Looking forward, Khan said that he plans to continue his studies and research at the graduate level, and he remains keenly aware of the human impact his work is contributing to and helping to facilitate.

“I knew I wanted my work to mean something. I always wanted to help people,” Khan said. “Being open-minded and getting involved in research shows you these opportunities to be involved in beneficial and meaningful work.”

Learn more about wireless charging systems for neural implants on the CNT and Sensor Systems Laboratory websites.