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.

Biomedical implants (BMIs) and biomedical sensors (BMSs) help to improve quality of life, detect diseases, provide monitoring of vital signs, and take over the role of malfunctioning organs. These implants and sensors require continuous battery power to work effectively, but the batteries used are restricted by their limited capacity and lifetime. This research reported here involved the design and implementation of a wireless charging system based on a seriesparallel spider-web coil (WPT-SP-SWC), specifically for cardiac pacemakers. The experimental design investigated several important parameters, including air gap, applied source voltage, coil size, and operating frequency. Performance metrics were evaluated in terms of output DC voltage, delivered output power, and power transfer efficiency. The target voltage was 5 V, which is adequate to charge a BMI such as a pacemaker, and three source voltages (5, 15, and 25 V) were tested. The design was examined at six operating frequencies, ranging from 1.78 MHz to 6.78 MHz. The most favorable results were achieved at 1.78 MHz. Power transfer efficiencies at a 10 mm air gap were 95.75% and 92.08% for applied voltages of 5 V and 15 V, respectively. The effectiveness of the proposed system was also validated by comparing the findings with previous articles.

A biomedical implant (BMI) is a device that allows patients to monitor their health condition at any time and obtain care from any location. However, the functionality of these devices is limited because of their restricted battery capacity, such that a BMI may not attain its full potential. Wireless power transfer technology-based magnetic resonant coupling (WPT-MRC) is considered a promising solution to the problem of restricted battery capacity in BMIs. In this paper, spider web coil-MRC (SWC-MRC) was designed and practically implemented to overcome the restricted battery life in low-power BMIs. A series/parallel (S/P) topology for powering the BMI was proposed in the design of the SWC-MRC. Several experiments were conducted in the lab to investigate the performance of the SWC-MRC system in terms of DC output voltage, power transfer, and transfer efficiency at different resistive loads and distances. The experimental results of the SWC-MRC test revealed that when the Vsource is 30 V, the DC output voltage of 5 V can be obtained at 1 cm. At such a distance (i.e., 1 cm), the SWC-MRC transfer efficiency is 91.86% and 97.91%, and the power transfer is 13.26 W and 23.5 W when 50-and 100-Ω resistive loads were adopted, respectively. A power transfer of 12.42 W and transfer efficiency of 93.38% were achieved at 2 cm for when a 150-Ω resistive load and a Vsource of 35 V were considered. The achieved performance was adequate for charging some BMIs, such as a pacemaker.