Wireless Power Transfer Based on Spider Web–Coil for Biomedical Implants

Abstract

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.

Powering implanted sensors that monitor human activity using spider‐web coil wireless power transfer

“…The value of M between SWC–TX and SWC–RX was determined using Equation () [41, 42] as follows: $$$$\begin{equation} M = \frac{{{{{\mu}}_0}{\rm{\pi \ }}{{({D_{{\rm{SWC}} - {\rm{TX}}}}{D_{{\rm{SWC}} - {\rm{RX}}}})}^2}{N_{{\rm{SWC}} - {\rm{TX}}}}{N_{{\rm{SWC}} - {\rm{RX}}}}}}{{2\sqrt {{{\left( {D_{{\rm{SWC}} - {\rm{RX}}}^2 + {{\rm{X}}^2}} \right)}^3}} }}\end{equation}$$$$where μ◦ is the permeability of free space (4π × 10 −7 ) H/m [4, 43], N SWC–TX and N SWC–RX are the numbers of turns in the transmitter and receiver coils, X is the air gap distance between the SWC–TX and SWC–RX coils, and, as mentioned previously, D SWC–TX and D SWC–RX are the outer diameters of the transmitter and receiver coils. From the equation of self‐induction and the calculated M , the coupling coefficient ( k ) can be assessed as a proportion of interlock, determined from Equation () [15] as follows: $$$$\begin{equation}k\ = \frac{M}{{\sqrt {{L_{{\rm{SWC}} - {\rm{TX}}}}{L_{{\rm{SWC}} - {\rm{RX}}}}} }}\ \end{equation}$$$$…”

“…The implants are positioned either entirely or partially inside the human body. The required power level ranges from a few milliwatts to tens of watts, depending on the device's requirements [15]. To improve the performance of the WPT system (i.e.…”

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

“…For the misaligned setup case, the efficiency was 65%. Our previous work 41 reported utilization of an MRC–WPT‐based spider‐web coil design to energize a pacemaker wirelessly. The design had an SP configuration with zero voltage switching (ZVS), class‐D power amplifier, using an EPC9065 board based on gallium nitride (GaN) semiconductor technology.…”

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

“…In the near-field WPT system, the achieved power transfer efficiency may reach in excess of 90%, however, the transfer distance is very small, ranging from a few millimetres to several centimetres [32,33]. For the far-field WPT system proposed in [34] with a frequency of 433 MHz, the conversion efficiency was 86% with an input power of 0.0125 W. In another proposed system with a frequency of 2.45 GHz, the conversion efficiency was 67% with an applied input power of 0.05 W [35].…”