Characterization of RF Differential Tissue-Coupled Powering (DTCP): An Emerging Sub-GHz Wireless Power Transfer Link for Bio-Implants

Among emerging wireless power transfer (WPT) modalities, differential tissue-coupled powering (DTCP) is particularly compelling because it directly harnesses biological tissue as the channel for the power-delivery, while remaining compatible with ultra-thin, thread-like implants. Here, we present, for the first time, a comprehensive theoretical and experimental characterization of radio frequency (RF)-DTCP as a wearable-to-implant WPT scheme. We develop a generalized analytical framework that models arbitrary four-electrode TX-RX configurations, derives port-level admittances from the underlying impedance network, and evaluates power transfer efficiency as an explicit function of geometry, tissue properties, and frequency, including a closed-form expression in the capacitive-dominated region. In ex vivo porcine tissue, sub-GHz (0.5–0.6 GHz) RF-DTCP achieves 10–25% PTE at implant depths > 5 mm for implant lengths from 1–8 cm, while maintaining high tolerance to angular misalignment and extending all the prior body-coupled links that were confined to < 10 MHz. Combined, these results establish RF-DTCP as a robust and scalable WPT method for future minimally invasive bio-implants.