A Batteryless Implantable System with Adaptive Near-Field Communication to Study Neurogastroenterological Disorders

To study the neurophysiology of the gastric system in the long term, it is essential to develop batteryless and wireless gastric implants with adaptive communication. This paper presents the development of a system that establishes a closed-loop wireless power transfer and bidirectional data transfer between a wearable unit (WU) and a miniature implantable unit (IU) through near-field communication. The neurophysiological activity of the gastric system is digitized, modulated through a load-shift keying (LSK) scheme, and transmitted from the IU to the WU over a 13.56 MHz adaptive inductive link. Besides, electroceutical therapeutic instructions are modulated through an amplitude-shift keying (ASK) scheme and sent over the reverse path for execution. A half-duplex data transmission protocol was developed to manage the sequential IU-WU and WU-IU data transfers and avoid collisions of data packets over the same inductive link. In addition, the uplink and downlink data are encoded through a self-clocking algorithm. The benchtop validation of the developed system demonstrated successful near-field communication at a data transfer rate of 125 kbps with no mismatch in both directions.