Wireless Power Transfer Techniques for Implantable Medical Devices: A Review

Abstract

Wireless power transfer (WPT) systems have become increasingly suitable solutions for the electrical powering of advanced multifunctional micro-electronic devices such as those found in current biomedical implants. The design and implementation of high power transfer efficiency WPT systems are, however, challenging. The size of the WPT system, the separation distance between the outside environment and location of the implanted medical device inside the body, the operating frequency and tissue safety due to power dissipation are key parameters to consider in the design of WPT systems. This article provides a systematic review of the wide range of WPT systems that have been investigated over the last two decades to improve overall system performance. The various strategies implemented to transfer wireless power in implantable medical devices (IMDs) were reviewed, which includes capacitive coupling, inductive coupling, magnetic resonance coupling and, more recently, acoustic and optical powering methods. The strengths and limitations of all these techniques are benchmarked against each other and particular emphasis is placed on comparing the implanted receiver size, the WPT distance, power transfer efficiency and tissue safety presented by the resulting systems. Necessary improvements and trends of each WPT techniques are also indicated per specific IMD.

Energy-Aware System Design for Autonomous Wireless Sensor Nodes: A Comprehensive Review

“…IPT systems transmit power through coils with a specific frequency in the range of hundreds of kHz [ 46 ]. Over the last years, significant investigations have been conducted to improve the performance of IPT systems, especially for wireless charging of mobile devices, but also medical applications [ 55 ] and electric vehicles [ 56 ], which can be scaled up or down for wireless sensors. Different aspects could be optimized considering coil geometry and technology, operating frequency, multi-coil systems, resonant compensation topologies and misalignment.…”

Miniaturised Wireless Power Transfer Systems for Neurostimulation: A Review

“…The Eddy resistance is defined by (9): (9) in which the frequency ω crit at which the current crowding effect starts to become significant is defined by (10) taking in consideration the sheet resistance R sheet [31]:…”

“…For this reason, this review has the gaze turned toward the miniaturisation of the implant. Differently from other works [8], [9], [10] this review compares the advantages as well as the critical limitations of each powering method in designing a wireless link specifically for neurostimulation with extremely miniaturised implants.…”

Investigation on Wireless Link for Medical Telemetry Including Impedance Matching of Implanted Antennas

“…In addition to the antenna designs, studies on radio transmission have been performed with the aim to create reliable communication links between devices outside and inside the human body. Wireless power transfer (WPT) using electromagnetic waves can be classified into the following groups: (1) non-radiative, (2) radiative and non-radiative mid-field, and (3) radiative far-field [ 3 ]. In addition, WPT using an acoustic link can be classified as a non-EM (Electromagnetics) solution [ 4 ].…”