People often talk about “brain power.” But they might not be giving "stomach power" enough credit.
A new electronic pill, equipped with a Wi-Fi transmitter, can harvest energy from inside a person’s own stomach to record core body temperature and then beam the information to an external monitor.
The model can power itself for nearly a week. This is much longer than current ingestible devices, which are only able to share health information for less than an hour. Indeed, this ingestible device carries the longest-lasting, strongest energy harvester to date.
Device Could Deliver Drugs
While you can’t make Skype calls with this Wi-Fi pill, it could lead to fresh opportunities for drug delivery or real-time health monitoring from inside organs, said Giovanni Traverso, a doctor and biomedical engineer at Brigham and Women’s Hospital in Boston. Traverso co-led a study of the pill that was recently published.
It is a really big deal that this pill can measure body temperature. Despite our many medical advances, we’re pretty bad at measuring core body temperature. A recent study of 8,600 patients found that thermometer readings from the mouth, armpit or skin did a lousy job of measuring core temperature. Getting an accurate temperature is important. Without one, a patient under anesthesia about to go into surgery could face risks, like having a dangerously low body temperature. Inaccurate temperature readings could also complicate treatment for a patient with higher risk of developing an infection.
Traverso is a maker of origami-style ingestible devices. The devices fit inside a capsule but unfold when they hit the stomach and deliver drugs for long periods of time before they break down and pass through the body. About two and a half years ago, he and some collaborators wondered if adding a power source to such a device could extend its working lifespan.
“One of the things that we discussed early on was the potential to power systems using the gastric acid,” Traverso said.
Like A Lemon Battery, Pill Uses Metal To Generate Electricity
Ever build a lemon battery in grade school? If so, then you already know how this idea works. A lemon battery draws power from an electro-chemical reaction. Two metal electrodes — typically a zinc rod and a copper penny — are thrust into the fruit. The metals react chemically with the acidic lemon juice and dissolve, creating an imbalance. The zinc builds up negatively charged electrons and the copper fills with positively charged ions. Connect a wire between the metals, and electricity will flow between the two.
To make the power-harvesting pill, the team used miniaturized pieces of copper and zinc. "These metals react with the stomach acid and generate electrons to flow in the external circuit,” said Philip Nadeau, an electrical engineer who co-designed the device.
The electrodes were placed on the outside of a silicon capsule the size of an AirPod earbud, which housed all of the sensitive circuits and electronics. The device could harvest only a tiny amount directly from the stomach juices. So the engineers added an energy storage capacitor to boost the output.
“We were generating about 15 microwatts, so you would need about six million [of these devices] to power a 100-watt light bulb,” Nadeau said. “But it basically generates the same power level that a lot of Bluetooth devices use.”
In Pigs, Device Transmitted Data To A Device 10 Feet Away
To prove it, Nadeau and the others field tested the device in pigs. Each pill contained the electrodes, a temperature sensor and a Wi-Fi transmitter. The information beamed to a receiver hanging from the ceiling about 10 feet away, but Nadeau suspects the signal could reach as far as 32 feet.
“The device was sending a temperature measurement and a few performance indicators of the system every 12 seconds,” Nadeau said. “So basically it would be almost like a tweet, maybe a bit shorter than a tweet.”
For six days, the gadget tracked core body temperature as the pill moved through the stomach and intestines of pigs. Until now, similar ingestible devices had only been able to harvest less than an hour’s worth of energy. Another version used the harvested energy to deliver a dose of drugs.
“It’s a pretty nice accomplishment,” said John Rogers, a scientist at the University of Illinois at Urbana-Champaign. Rogers wasn’t involved in the study. “Not only were they able to sustain a power for a period of six days, but it was at levels of power that were practically useful.”
Use Of Copper In Humans Will Require More Study
In terms of safety, the pigs’ stomachs were exposed only to the zinc and copper electrodes; the silicone capsule encased the rest of the electronics. Zinc is a vitamin, and the amount released as the electrode dissolved was not dangerous. The risks associated with the copper are less clear, Rogers said. The electronic pill has low doses of zinc and copper, but it will need more study before use by humans.
Traverso and Nadeau are also aiming to shrink the pill to the size of a tablet.
“When I show it to people they say, ‘I’m not going to swallow that!'” Nadeau said. “Now that we know how much power is available, miniaturization is definitely (possible)."
Traverso thinks temperature tracking is just the first of many ways the medical community can use the device.
“We’ve looked at measuring other vital signs like the heart rate and respiratory rate,” Traverso said. “Systems that could be powered like this and stay in the stomach for a long time could monitor vital signs and diagnose a whole host of respiratory and cardiovascular diseases.”
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