A Wireless Rechargeable Implantable System for Monitoring and Pacing the Gut in Small Animals*

Long-term studies of gastrointestinal bioelectrical activity, termed slow-waves (SWs), emphasizes the necessity of implantable systems featured with a reliable wireless power transfer (WPT) link. This paper presents the development and benchtop validation of a system that can wirelessly acquire SWs, modulate the gastrointestinal activity through delivering short and long pulses to the stomach, and be wirelessly recharged through a 13.56 MHz inductive link. The developed system is composed of an implantable unit, an under-the-cage charging unit, and a stationary unit connected to a computer. An application-specific graphical user interface was designed in LabVIEW to process and display the recorded SWs in real time and to configure the stimulation pulses, wirelessly. The system was successfully validated in benchtop settings. The validation of the system showed appropriate frequency response of analog conditioning and digitization resolution to acquire SWs. Moreover, the system was able to deliver electrical pulses at amplitudes up to ±12 mA to a maximum load of 1 kΩ. In addition, the voltage of the 110 mAh LiPo battery at the implantable unit was increased from 3.3 V to 4.2 V in 30 minutes by the charging unit while the recording system was fully functional.