A new flexible piezoelectric sensor is 2 × 2.5 cm and can be rolled up and swallowed. (Credit: MIT)

Researchers have built a flexible sensor that can be rolled up and swallowed. Upon ingestion, the sensor adheres to the stomach wall or intestinal lining, where it can measure the rhythmic contractions of the digestive tract.

Such sensors could help doctors to diagnose gastrointestinal disorders that slow down the passage of food through the digestive tract. They could also be used to detect food pressing on the stomach, helping doctors to monitor food intake by patients being treated for obesity.

The flexible devices are based on piezoelectric materials, which generate a current and voltage when they are mechanically deformed. They also incorporate polymers with elasticity similar to that of human skin, so that they can conform to the skin and stretch when the skin stretches.

To make the new sensor, researchers fabricated electronic circuits on a silicon wafer. The circuits contain two electrodes: a gold electrode placed atop a piezoelectric material called PZT, and a platinum electrode on the underside of the PZT. Once the circuit is fabricated, it can be removed from the silicon wafer and printed onto a flexible polymer called polyimide. The ingestible sensor designed for this study is 2× 2.5 cm and can be rolled up and placed in a capsule that dissolves after being swallowed.