Stomach-Acid Powered Batteries

Medicine+pills+spilling+out+of+container.

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Medicine pills spilling out of container.

Recently, small ingestible devices are being used more often for drug delivery substitutes in difficult cases. The only obstacle is finding ways to power them. That’s why a team of researchers from MIT have developed a battery powered by the acids found in the stomach, a cheap and safe alternative power source. This new stomach-acid powered battery can generate enough power to run sensors and drug delivery tools for longer periods of time.

Giovanni Traverso and Robert Langer, the senior authors of this project, have previously developed systems that need batteries like these, such as a drug delivery system that unfolds in the stomach to release medicine over the course of a couple weeks, and a sensor the size of a pill that is used to monitor the patient’s heartbeat and breathing. When regular batteries are used, they tend to wear out, and can contain chemicals that could be harmful to the human body. Giovanni Traverso has previously stated, “We need to come up with ways to power these ingestible systems for a long time. We see the GI tract as providing a really unique opportunity to house new systems for drug delivery and sensing, and fundamental to these systems is how they are powered.”

Most batteries run on acid, and the stomach has a very acidic environment, which is perfect to power the batteries.  This battery was inspired by the lemon battery, a simple type of voltaic cell. Taking ideas from that, scientists attached zinc and copper electrodes to the outside of the small device containing a temperature sensor and a 900 MHz transmitter inside. Stomach acid conducts the electric current from the zinc to the copper, and powers the battery. When tested inside a pig, it took an average of six days for the device to travel through the digestive tract, and it was able to send temperature readings, and send data about every 12 seconds to a receiver 6.6 feet away. When the device moved to the small intestine, the cell only produced a small percentage of what it produced in the stomach, but it could still send data, just at a slower rate.

Currently, the prototype is in the shape of a cylinder, and is 40 mm long and 12mm wide. Researchers hope that by changing the circuitry in the device, they could shrink it down to one-third of the current size. They would also like to add other sensors and devices to monitor vital signs and treat a variety of diseases and conditions. Philip Nadeau, a lead author of the study, predicts, “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. It just sits there making measurements and transmitting them to your phone.” These batteries will help doctors in many ways such as providing a way for them to measure dosages of a drug needed. Kraemer student Melody S. states,” It is amazing that these batteries are powered by stomach acid!”