A Tissue-Channel Transcutaneous Power Transfer Technique for Implantable Devices

For implantable devices, miniaturization is a key design consideration, which facilitates keyhole surgery and relieves the surgical pain. Wireless power transfer is a commonly used way for implants, and a high power transfer efficiency (PTE) could help to minimize or even remove the battery inside the human body. Conventionally, the required power is delivered transcutaneously to a medical implant by inductive coupling or capacitive coupling, but the PTE is extremely low when targeting at a very small implant through a thick tissue layer. In this paper, we propose a new technique by utilizing the body tissue as the power transfer channel, where a pair of medical electrodes are attached on the body surface to supply power to a miniaturized implant with a differential input. The PTE is remarkably improved by the current loop through the body tissue without violating the IEEE specific absorption rate standard. Measurement results show that the tissue-channel technique achieves 0.39% PTE for a 1-mm-sized implant locating 5 cm deep inside the tissue.