Inflatable Pill Created for Stomach Monitoring
Jeffrey Heimgartner posted on February 20, 2019 |

The best way to monitor physiological issues is from the inside. Technologies continue to emerge in the form of ingestible electronics that can do just that. Often, this new research involves materials that aren’t necessarily bio-friendly or are limited in how long they last. Researchers at MIT have developed a biocompatible, hydrogel pill that addresses these issues.

Their inflatable pill was created using two hydrogels, which are a mix of water and polymers. This unique combo allows the pill to quickly inflate to about the size of a ping-pong ball in the stomach without being affected by stomach acid and movement. Once inflated, they are similar in consistency to Jell-O. Included in the pill is a sensor that can track stomach temperature for approximately 30 days, which could help monitor potential disease or vital signs.

The ingestible hydrogel pills swells to a Jell-O-like substance the size of a ping-pong ball and deflates into a membrane that easily passes through the stomach. (Image courtesy of MIT/Xinyue Liu, Shaoting Lin.)
The ingestible hydrogel pills swells to a Jell-O-like substance the size of a ping-pong ball and deflates into a membrane that easily passes through the stomach. (Image courtesy of MIT/Xinyue Liu, Shaoting Lin.)

One obstacle the team faced was the stomach itself. If the pill was too small, it could pass through the stomach via the pylorus. To counter this, in their research recently published in Nature Communications, the team drew inspiration from the defense mechanisms of the pufferfish. This slow-moving fish inflates by quickly sucking in a large amount of water. The researchers began to experiment with ways to have their pill inflate at the same speed to a size that wouldn’t be able pass through.

“Currently, when people try to design these highly swellable gels, they usually use diffusion, letting water gradually diffuse into the hydrogel network,” said Xinyue Liu, one of the lead authors. “But to swell to the size of a ping-pong ball takes hours or even days. It’s longer than the emptying time of the stomach.”

The ingestible hydrogel device inflates in water with at a high rate and ratio and lasts around 30 days. During testing, the team found that the pill inflated 100 times its size in approximately 15 minutes. (Image courtesy of MIT/Xinyue Liu.)
The ingestible hydrogel device inflates in water with at a high rate and ratio and lasts around 30 days. During testing, the team found that the pill inflated 100 times its size in approximately 15 minutes. (Image courtesy of MIT/Xinyue Liu.)

It also needed to be able to last in the ever-moving stomach. To ensure its longevity, they developed a second protective layer out of nanoscopic, crystalline chains. These chains are folded over each other to create a gridlock pattern that is impregnable.

“We found that even when we make a small cut in the membrane and then stretch and squeeze it thousands of times, the cut does not grow larger. Our design is very robust,” Lin said.

The team also developed a calcium ion solution that shrinks the particles. A patient can drink the solution to deflate the pill for it to easily pass through the stomach.

The researchers believe their new device could lead to safer ways of delivering sensors internally. It also opens the door to potentially including cameras for additional monitoring or to be used as a safe form of diet control.

Interested in more medical innovations? Check out Smart Capsule Aims to Ease Medicating and Monitoring Diseases and The Future of Medicine Is at the Nanoscale.

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