For controlled drug delivery and health monitoring, an alternative consists in designing sensor-laden and drug-carrying pills that can be swallowed, though their stay in the stomach is rather transient, usually lasting only a day or two before being excreted.
Now, researchers from the Massachusetts Institute of Technology have designed an electronic pill that unfolds when it reaches the stomach, preventing it from following its natural course through the gastrointestinal route. On the mechanical side, the Gastric Resident Electronic (GRE) system as it is called (because it remains in the gastric cavity for up to a month), consists of a 3D-printed elastomeric shape whose arms are folded back along the pill's main body into a gelatin capsule. After ingestion, the gelatin dissolves within seconds in the gastric fluid and the arms expand again, somehow anchoring the pill within the stomach so its sensors and multiple drug carriers can operate for longer within the human body.
In a paper titled "3D-Printed Gastric Resident Electronics" published in Advanced Materials Technologies, the researchers report Bluetooth-enabled GRE prototypes lasting up to 36 days in the hostile gastric environment, maintaining their wireless connectivity for about 15 days.
Measuring the actual radio signal from the ingested pill, the authors report a stable transmission at 2.4GHz and the possibility to directly interconnect the electronic pill with external devices such as Bluetooth-enabled wearables and smartphones while simultaneously restricting the signal strength to within an arm’s length (−80 to −90 dBm at 45 cm) to provide a physical isolation for additional security and privacy protection.