Near-Field Wireless Power Transfer to Stent-Based Biomedical Implants

Safe wireless power transfer is an essential requirement for biomedical implants. Emerging technologies are becoming smaller, less invasive and consuming less power. Moreover, stent-based devices are being recognized as a minimally invasive alternative to traditional surgery. Hence, the idea of using the body of the stent as the power receiving element is becoming increasingly attractive. The objective of this work is to analyze two near field wireless power transfer methods to stent-based devices, viz., inductive and capacitive coupling. The methods used are lumped element modelling, ac circuit theory, finite-element analysis, experiments with excised bovine muscle tissue and a live ovine vascular model. Capacitive coupling is proposed as an alternate method due to the transmitter design that can be worn anywhere on the body. It achieves power transfer efficiencies of 2.6% and 1% when placed at depths in muscle tissue of 15 mm and 30 mm respectively. Safety requirements are also met. The capacitive link can accept an input power of 53 mW before exceeding the safe specific absorption rate limit of 1.6 W/kg averaged over 1 g of tissue.