Towards Battery-Less Internet of Bodies: Energy Harvester with Reconfigurable Stages Enabled by Galvanic Body-Coupled Powering for Bio-Implants

In the rapidly evolving landscape of connected healthcare, this work offers new insights into self-powered, intelligent bio-electronics within the Internet of Bodies (IoB). Key prevailing challenges include the need for battery-free, wirelessly powered biomedical implants and efficient energy-harvesting (EH) methods that can sustain sensing, communication, and security functions in the complex tissue environment. Our proposed system utilizes a body-coupled powering (BCP) approach, harnessing the body’s natural conductive properties and employing galvanic coupling (G-BCP). By improving targeting accuracy, power transfer efficiency (PTE), and tissue penetration, G-BCP surpasses traditional wireless power transfer (WPT) methods. Additionally, a reconfigurable N-stage rectifier circuit enables maximum power transfer, adapting to frequency-dependent tissue-electrode impedance variations without any adaptive matching network. To substantiate the proposed design concept, a simulated prototype in Ansys HFSS, modeling a multi-layered tissue medium of 75 mm radius with a 5 mm implant depth, achieves over 11.7% peak PTE at 1 GHz and > 1 mW power delivery with a SAR limit of < 0.048W/kg from 0.78 - 1.35 GHz frequency range. Circuit-level simulations using the TSMC 65-nm CMOS process further confirm the system’s adaptability, with a 100-stage EH circuit reconfiguring to N < 100 for optimum WPT. Therefore, the G-BCP-based reconfigurable EH system is envisaged to be a key enabler in establishing a scalable framework for powering bio-implants in the realm of IoB applications.