An implantable, batteryless, and wireless capsule with integrated impedance and pH sensors for gastroesophageal reflux monitoring

Hung Cao, Vaibhav Landge, Uday Tata, Young Sik Seo, Smitha Rao, Shou Jiang Tang, H. F. Tibbals, Stuart Spechler, J. C. Chiao

Research output: Contribution to journalArticlepeer-review

98 Scopus citations


In this study, a device for gastroesophageal reflux disease (GERD) monitoring has been prototyped. The system consists of an implantable, batteryless and wireless transponder with integrated impedance and pH sensors; and a wearable, external reader that wirelessly powers up the transponder and interprets the transponded radio-frequency signals. The transponder implant with the total size of 0.4cm ×0.8cm ×3.8cm harvests radio frequency energy to operate dual-sensor and load-modulation circuitry. The external reader can store the data in a memory card and/or send it to a base station wirelessly, which is optional in the case of multiple-patient monitoring in a hospital or conducting large-scale freely behaving animal experiments. Tests were carried out to verify the signal transduction reliability in different situations for antenna locations and orientation. In vitro, experiments were conducted in a mannequin model by positioning the sensor capsule inside the wall of a tube mimicking the esophagus. Different liquids with known pH values were flushed through the tube creating reflux episodes and wireless signals were recorded. Live pigs under anesthesia were used for the animal models with the transponder implant attached on the esophageal wall. The reflux episodes were created while the sensor data were recorded wirelessly. The data were compared with those recorded independently by a clinically used wireless pH sensor capsule placed next to our implant transponder. The results showed that our transponder detected every episode in both acid and nonacid nature, while the commercial pH sensor missed events that had similar, repeated pH values, and failed to detect pH values higher than 10. Our batteryless transponder does not require a battery thus allowing longer diagnosis and prognosis periods to monitor drug efficacy, as well as providing accurate assessment of GERD symptoms.

Original languageEnglish (US)
Article number6279457
Pages (from-to)3131-3139
Number of pages9
JournalIEEE Transactions on Biomedical Engineering
Issue number12 PART2
StatePublished - 2012


  • Gastroesophageal reflux disease (GERD)
  • impedance sensor
  • implantable
  • pH sensor
  • wireless powering

ASJC Scopus subject areas

  • Biomedical Engineering


Dive into the research topics of 'An implantable, batteryless, and wireless capsule with integrated impedance and pH sensors for gastroesophageal reflux monitoring'. Together they form a unique fingerprint.

Cite this