A wireless, ingestible pH sensing capsule system based on iridium oxide for monitoring gastrointestinal health

The pH of the gastrointestinal (GI) tract has strong correlation with many GI diseases. In this study, a wireless and ingestible capsule system for monitoring GI pH was reported. Iridium oxide was electrodeposited on the screen-printed electrode (SPE) to form the pH sensor, which had the high sensitivity and wide detection range for H+. The rigid-flexible composited printed circuit board (RFPCB) technique was used to design the capsule detection circuit. Both of them were encapsulated into the 3D-printed capsule structure. With the biocompatibility treatment, the entire capsule system could be obtained, whose diameter and height were ~14.5 mm and ~26 mm, respectively. The capsule system could be ingested into the GI tract to perform real-time pH detection of biofluids, and the detected signal could be wirelessly transmitted to the external receiving device, which could be smartphone, personal computer, or the auxiliary circuit for wireless communication. In the in vivo evaluation of large animal, the capsule system could detect the pH of GI tract in real time, whose detection results were close to that of the professional pH instrument. Thus, the capsule system had the practical application potential of assisting in the clinical diagnosis of GI diseases.