Near‐field wireless power transfer used in biomedical implants: A comprehensive review

Abstract

Wireless power transfer (WPT) techniques have been utilized in various biomedical applications to overcome the challenges of battery capacity and lifetime, and high-cost surgical interventions, using biomedical implants (BMIs) and biomedical sensors (BMSs), including deep brain stimulators, capsule endoscopes, pacemakers, and cardiac monitoring sensors. In this article, near-field WPT methods in BMIs and BMSs, including magnetic resonator coupling (MRC), inductive coupling (IC), and capacitive coupling (CC), are reviewed, and some biomedical applications of these methods are highlighted. The applications of WPT have been explored in recent years to enhance the major performance metrics of BMIs. The main topologies of MRC-WPT are presented, and the main mathematical models related to each type were extracted from previous studies and detailed here. Additionally, the main performance metrics and results achieved, along with their suggested biomedical applications, are summarized in a comparison table. Some challenges and limitations of using WPT in the biomedical field and suggestions for improving the efficiency of WPT for biomedical applications are also discussed. Furthermore, future trends in WPT-based BMIs are also highlighted.

Electronic Tunability and Cancellation of Serial Losses in Wire Coils

“…The serial resistance of the inductor, representing an important real parameter of the coil, creates issues especially in the low-frequency bands (below 1 kHz) of the coil operation. Researchers in [ 49 ] clearly explain the importance of this parameter for the efficiency of near-field wireless power transfer but, depending on the frequency, it also plays a significant role in low-power sensing devices. Similarly as in [ 49 ], the serial resistance of the inductor decreases the efficiency of a receiving antenna (e.g., used in a sensor of an electromagnetic field).…”

“…Researchers in [ 49 ] clearly explain the importance of this parameter for the efficiency of near-field wireless power transfer but, depending on the frequency, it also plays a significant role in low-power sensing devices. Similarly as in [ 49 ], the serial resistance of the inductor decreases the efficiency of a receiving antenna (e.g., used in a sensor of an electromagnetic field). Commercially fabricated coils (and various types of inductors) have always this feature, influencing more or less the real operation of a system.…”

Wireless charging for cardiac pacemakers based on class‐D power amplifier and a series–parallel spider‐web coil

“…Thus, SAR varies between implantable environments, such as the head model, limbs, and torso. For these reasons, the WPT design in implants and sensors should explore these considerations within a specific limit for each body area 3,43,44 . SAR value differs for each type of human tissue because of the variability in tissue conductivity.…”

“…For these reasons, the WPT design in implants and sensors should explore these considerations within a specific limit for each body area. 3,43,44 SAR value differs for each type of human tissue because of the variability in tissue conductivity. Nevertheless, by controlling the power at the transmitter side of the WPT system, the output power can be kept within the safety recommendation of the Federal Communications Commission (FCC) to avoid adverse thermal effects and related harmful effects on health.…”

A Comprehensive Analysis, Design, and Experimental Evaluation of Single-Loop Polygonal Slotted RF Resonators and WPT Systems

“…They have been lately employed in a number of segments such as biomedicine, consumer electronics, microrobotics, vehicular, and emerging wireless technologies and can be broadly classified into far-and near-field types [1]- [3]. If the former is accomplished using protocols, namely, time-switching and power-splitting relaying techniques, the latter is achieved by following any of the coupling-based techniques (i.e., capacitive or inductive) [4]. As a concept, magnetic resonant coupling (MRC) also falls under the umbrella of inductive coupling.…”