Researchers in Boston have come up with a novel new way of powering ingestible capsules.
A team at Brigham and Women’s Hospital has developed a capsule that can be powered by a galvanic cell battery that draws its juice from stomach acid.
The team demonstrated this by having their battery successfully power an ingestible thermometer. It took measurements every 12 seconds inside a pig’s stomach for six days.
Experts in the field say that while there’s still a lot of work to be done, the research could be an important step to improving the long-term utility of ingestible devices.
The team was led by Phillip Nadeau, Ph.D., study author, and postdoctoral researcher at the Massachusetts Institute of Technology (MIT).
They announced their findings in Prolonged Energy Harvesting for Ingestible Devices, published in the journal Nature Research earlier this month.
Useful ... until the battery dies
Ingestible devices are useful tools for doctors.
They are utilized in a variety of applications from simple vital sign measurement, to dispensing medication, to “pill cams,” which provide video feedback as an alternative to more invasive means of diagnosis.
These devices, particularly the more energy-intensive pill cams, are limited by a lack of power. While simpler devices use minimal power, a pill cam tends to drain its battery quickly, with no means of recharging while it’s inside the body.
In an effort to develop a device that could provide continuous power on a long-term basis, the research team turned to an old science class standby.
“One of the things we started contemplating with our collaborators in the Department of Electrical Engineering at MIT was looking at a galvanic cell, basically a takeoff of the lemon battery that’s often explored in school,” Giovanni Traverso, Ph.D., senior co-author, and instructor at Harvard Medical School, told Healthline. “And that’s exactly what we did. We used the gastric fluid as the electrolyte, and we used the copper and zinc as the cathode and anode, respectively, to generate that current.”
“I think the researchers put forth some interesting demonstrations of a zinc-copper type electrolytic cell for power,” John Rogers, Ph.D., physical chemist, and chair of the Rogers Research Group at the University of Illinois, told Healthline. “By comparison to more widely used magnesium-based systems, the appeal of zinc is that it can offer long-term operation — several days, as opposed to one or two. So I think that’s an important advance. There’s an electrical engineering team involved in that work that put together some pretty interesting low-power electronics. They had some pretty clever ways to optimize the power utilization and accommodate for the fluctuations in the power that were coming from the battery.”
Drew Higgins, Ph.D., Banting Postdoctoral Fellow at Stanford University, told Healthline in an email, “The authors took fundamental electrochemistry concepts that many of us would have applied through lemon battery or penny battery experiments in school. While this battery chemistry may not be practical for your cell phone or laptop, the authors recognized some key features of these systems. Primarily, they are inexpensive, biocompatible, and capable of producing enough energy to power microdevices assembled in their laboratory.”
A variety of skills
The technology, which couples electrochemistry with biomedical engineering, required researchers with varied skillsets.
“We did have a diverse group with expertise ranging from electronics design to packaging, chemistry, and medicine,” wrote Nadeau. “Having such a diverse team was a tremendous asset to this work. Working at the interface of these different areas helped us find and try something that was broadly interesting.”
“There are electrical engineering challenges here, there are materials challenges, and then there are animal model challenges,” acknowledged Traverso. “So you really need a broad expertise to come together, collaborate, and execute. And that’s reflected in the manuscript when you look at the authors and where they come from. They come from departments in electrical engineering, chemical engineering, from hospitals, and I think it really takes that kind of collaboration to address some of the major challenges.”
Higgins says this multidisciplinary approach is crucial — not just in this research, but in other scientific endeavors.
“As scientists and engineers, we consistently talk about the fact that interdisciplinary collaborations underpin some of the most high impact research,” he wrote, “And this study exemplifies this perfectly.”
Big possibilities, big challenges
This technology could underpin the way ingestible devices operate in the future.
The research, however, is still in its infancy.
Nadeau says that miniaturizing the device and using more advanced circuit design is a priority.
He’d also like to explore more advanced sensors.
“Ultimately, it would be neat if five or 10 years down the road, we could power a long-term ingestible vital signs monitor with this technology,” Nadeau said. “Essentially, a pill that could monitor your breathing and heart rate from inside the stomach and transmit it wirelessly for up to a week using the harvested energy from the cell.”
“You can just let your imagination run wild with things you’d like to measure, sense, capture, store, sample, or even deliver therapy. Kind of the whole gamut,” said Rogers. “But I think the menu of options is going to be limited by the range of functionality you can pack into a relatively small footprint. But then, the overarching concern is going to be how to power it. I think going forward, there will probably be a lot of optimization you can do. But it’s a good starting point for sure.”
“With respect to where we could be in five or 10 years, I think that depending on further interest — and that means collaboration with potential sponsors and also further funding — I think we could be in humans fairly quickly,” said Traverso.