When Swallowed, This Sensor Is Powered by Stomach Acid

In a new approach to an old problem, MIT researchers have discovered a way to power batteries within ingestible medical devices.

This just in from the electrified gastroenterology desk: A team of MIT scientists has developed an ingestible medical sensor powered by stomach acid. When swallowed, the sensor becomes its own battery and beams diagnostic information straight from your belly. This is what happens when you let the surgeons sit next to the electrical engineers at lunch.

The biomedical energy system, which has already been successfully tested on pigs, may be used to develop an entirely new class of internal sensors and drug delivery devices, according to the research team.

Ingestible medical devices aren't new, but they've always had a fundamental problem in regard to batteries. Traditional battery systems, even when radically miniaturized, can pose obvious health risks when cut loose in the gastrointestinal tract. And the miniaturization process itself severely limits the power output of any given battery solution.

By utilizing the body's own natural acids, the new ingestible device sidesteps the battery issue altogether. Instead, the device acts as its own voltaic cell, using the surrounding stomach acid to facilitate the electrical circuit.

Remember those lemon-powered batteries from middle school science class? It's essentially the same thing. With lemon batteries, the citric acid connects the two electrodes - usually a galvanized nail and a copper penny. Researchers simply replicated the system, attaching zinc and copper electrodes to the surface of the ingestible sensor.

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In the initial experiments, the improvised acid battery produced enough juice to power a commercial thermometer and a 900-megahertz wireless transmitter. Temperature readings were beamed from the stomach to a base station about two meters away.

"This work could lead to a new generation of electronic ingestible pills that could someday enable novel ways of monitoring patient health and/or treating disease," said MIT researcher Robert Langer, in press materials about the breakthrough. The research was published in the Feb. 6 issue of Nature Biomedical Engineering.

The prototype device is a pill-shaped cylinder about 40 millimeters long and 12 millimeters in diameter. That's a relatively big pill to swallow, but the researchers believe they can get down to about one-third of that size by incorporating integrated circuity. The electronic pill could also be used as a drug-delivery device that gives doctors more control over timed release and dosages.

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Possible consumer applications are on the table, as well.

"You could have a self-powered pill that would monitor your vital signs from inside for a couple of weeks, and you don't even have to think about it," said MIT postdoc researcher Phillip Nadeau. "It just sits there making measurements and transmitting them to your phone."

Sounds great! You first.

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