UNIVERSITY PARK, Pa. — Researchers at Penn State are designing a new wireless rechargeable battery for biomedical electronics, such as cardiac pacemakers, that will allow them to be charged and managed without the need for invasive surgery.

“We want to optimize the battery and the materials design and couple that with wireless charging,” said Feifei Shi, assistant professor of energy engineering in the John and Willie Leone Family Department of Energy and Mineral Engineering at Penn State. “Currently, we are limited to cable charging, and wireless charging is definitely the future.”

Biomedical devices recreate physiological functions in the human body that relieve chronic pain and vastly improve quality of life, and the past few decades have seen tremendous growth in electronics and wireless technology that champion this cause. However, a remaining challenge for medical devices is the power supply. The bulk of most implantable electronic devices is driven by primary batteries that have a limited lifespan and must be charged using cables. With human longevity at an all-time high, scientists need a longer-lasting, more reliable alternative to the lithium iodine batteries currently being used.

“Ten years ago, this was not the problem,” Shi said. “But nowadays, battery replacements are much more frequent because people are living longer.”

The first implanted cardiac pacemaker used a nickel-cadmium rechargeable battery. Zinc-mercury batteries were then developed, which lasted for more than two years. But nothing performed as well as the lithium iodine battery, invented in 1972. These batteries last for up to 10 years and are the gold standard for many manufacturers of cardiac pacemakers. Problems arise, however, when people outlive their pacemaker batteries, sometimes by decades. Battery replacement surgeries, while relatively safe, do not come without risks, especially at an advanced age. These risks include infection, blood clots, damage to the blood vessels or nerves, collapsed lungs and cardiac perforation.

To help solve this problem, Shi has received a $150,000 grant from Johnson & Johnson for a three-year project to develop a rechargeable battery with the ability to be charged wirelessly. The result will be a first-of-its-kind remotely chargeable, high-capacity battery within the human body. This new, rechargeable battery system has the potential to eliminate the risk of infection and other complications associated with surgery and provide a more stable and durable power supply to allow more health diagnostic sensors to be integrated into implemented medical devices. If successful, Shi said, she believes this project will save lives, minimize suffering, reduce costs and trigger the next revolution in implementable medical devices. 

The first step will be to adopt an existing non-commercial wireless charging method that is bio-safe and can penetrate muscle tissue, making charging within the body possible. To do this, they will run small-scale testing on some prototypes to find the optimal chemistry for this type of battery.

“Past research generally demonstrates wireless charging on a light bulb or a capacitor, they never demonstrate that they can charge a battery,” Shi said. "There is a difference between igniting a light bulb, and a real usage and aging test.” 

The second task will be structural optimization. The device will need to be tiny, and the receptor will need to be integrated, which is a novel concept, explained Shi.

“I want to think of the battery as a whole and think about every component of it, this is not only about the battery's performance,” Shi said. "We are starting from scratch, there is nothing like this that exists, so we have a lot of freedom. This is good because if we were working on existing technology, we don't have too much space to play. This gives us more opportunities to invent something new, something more useful for society.”

The biggest challenges will be safety and battery life, Shi said. Ideally, she said, she hopes to develop something that has a 20- or 30-year calendar life and is safe in the human body. 

“If you have a car that catches fire, you can run away,” Shi said. “But if you have something inside your body that is not accessible at all, it has to be reliable, so safety is the highest priority and the most complex.” 

Shi said she hopes that her background and experience in battery development along with cross-collaborative efforts with other researchers will allow her to make a battery that redefines biomedical battery technology. 

“From both the battery aspect, and the wireless charging aspect, my ultimate goal is to customize a better battery that can accommodate wireless charging in the body,” Shi said. "My research area is only one very narrow corner, and health and medical devices are multi-disciplinary research areas. We will need a lot of people working together to make this come true.”