A Wirelessly-Powered Implantable System to Record and Modulate the Gastric Slow Waves in Freely-Behaving Rodents

To study the electrophysiology of gastrointestinal tract during fasting, eating, and fed states in long-term, development of gastric implants with an adaptive wireless power transfer is inevitable. The purpose of this paper is to develop a miniature implantable system that can simultaneously record the bioelectrical activity of the gastric system and pace the gut in freely-behaving rodents, e.g., mice and rats. The system transmits the digitized gastric data to a stationary unit through a far-field 2.4 GHz bidirectional communication link and receives back the stimulation configurations instructed by the user, in real-time. In addition, an under-the-cage charging unit establishes an inductive near-field 13.56 MHz wireless power and data transfer with the implantable system and in presence of the body movements and stomach motility of the subject, delivers a constant power to the implant through a closed-loop system. The benchtop validation of the system showed appropriate frequency response of the analog conditioning circuit in the range of 16 mHz to 1.6 Hz and the capability of the implant to generate monophasic and biphasic electrical pulses at amplitudes and frequencies up to ±10 mA and 10 kHz, respectively. In addition, it was demonstrated that the charging unit can generate an adjustable output power between 100 mW and 1000 mW and provide a constant rectified voltage of 3.8 V at the implant.