Engineers have designed a new inflatable pill, which they say could be used to monitor physiological parameters in the stomach for up to a month.
The hydrogel device is ingested as a standard-sized pill before rapidly swelling into a large soft sphere, while remaining impervious to the stomach's acidic environment. If the pill needs to be removed, a patient can drink a solution of calcium ions that triggers the pill to quickly shrink to its original size, so it can pass safely out of the body.
In animal tests, the engineers embedded small, commercial temperature sensors into several pills, which were fed to pigs, and found it was able to accurately track the animals' daily activity patterns for up to 30 days.
The engineers envisage that the pill could safely deliver a number of different sensors to the stomach for physiological monitoring. They suggest it could also be used to visualise the gastrointestinal tract by carrying a mini camera or as an alternative to gastric balloon.
"With our design, you wouldn't need to go through a painful process to implant a rigid balloon," said Xuanhe Zhao, associate professor of mechanical engineering at Massachusetts Institute of Technology.
The findings are reported in Nature Communications.