Gastrointestinal segment tracking of ingestible capsules using biodegradable superstrates

Ingestible capsules can access parts of the gastrointestinal tract that are otherwise difficult to reach. The real-time and continuous data transfer from inside the gastrointestinal tract to an external reader becomes even more valuable when the reader also has spatial information about the received data. Despite valuable advancements in ingestible microelectronics technology, the tracking and localization of these devices remain an open area of research. This work aims to present a methodology that can be easily adapted to any type of ingestible capsule to track its location within the digestive tract. The novelty of this technique lies in the use of natural biodegradation as a sensing mechanism and leveraging the intrinsic electrochemical characteristics of each organ to achieve its mission. Biodegradable pH-sensitive polymers are used as coating material for an ingestible capsule with an embedded antenna. Three layers of coatings are applied around the surface of the capsule, each soluble only in one of the three target organs: the stomach, small intestine, and large intestine. As the capsule arrives in the stomach, the first layer dissolves in the acidic pH range of this tissue. This removal of one layer shifts the resonance frequency of the antenna from its initial state upon entering the digestive tract. This frequency shift indicates the capsule's presence in the stomach. The same scenario applies as the capsule transitions from the stomach to the small intestine, and from there to the large intestine. Electromagnetic simulations are presented. Based on the numerical results, electromagnetic measurements on electrochemical phantoms mimicking the dielectric properties and pH of each organ are conducted as proof of concept.