Magnetoelectric Transducer Designs for Use as Wireless Power Receivers in Wearable and Implantable Applications.

Tyrel Rupp,Shane Williams,Shad Roundy,Binh Duc Truong

doi:10.3390/ma12030512

Abstract

As the size of biomedical implants and wearable devices becomes smaller, the need for methods to deliver power at higher power densities is growing. The most common method to wirelessly deliver power, inductively coupled coils, suffers from poor power density for very small-sized receiving coils. An alternative strategy is to transmit power wirelessly to magnetoelectric (ME) or mechano-magnetoelectric (MME) receivers, which can operate efficiently at much smaller sizes for a given frequency. This work studies the effectiveness of ME and MME transducers as wireless power receivers for biomedical implants of very small (<2 mm3) size. The comparative study clearly demonstrates that under existing safety standards, the ME architecture is able to generate a significantly higher power density than the MME architecture. Analytical models for both types of transducers are developed and validated using centimeter scale devices. The Institute of Electrical and Electronics Engineers (IEEE) and the International Commission on Non-Ionizing Radiation Protection (ICNIRP) standards were applied to the lumped elements models which were then used to optimize device dimensions within a 2 mm3 volume. An optimized ME device can produce 21.3 mW/mm3 and 31.3 μW/mm3 under the IEEE and ICNIRP standards, respectively, which are extremely attractive for a wide range of biomedical implants and wearable devices.

Highlights

The current explosion of wearable devices has led to increased attention on methods to power them from harvested energy
In order to characterize the ME and MME transducers, a nested Helmholtz coil was constructed to create a uniform alternating current (AC) magnetic field superimposed on a direct current (DC) magnetic field
The measured and simulated open circuit voltage as a function of frequency for the MetglasPVDF device is shown in Figure 11. (The open circuit voltage for the Galfenol-PZT device is shown above in Figure 10.) In both cases, the DC magnetic field was optimally biased prior to the measurements

Summary

Introduction

The current explosion of wearable devices has led to increased attention on methods to power them from harvested energy. The most common way to power IMDs is via a direct (wired) external source or a battery implanted along with the IMD. Batteries help mitigate the problems presented by the direct powering method, they have finite lifetimes and require periodic replacement. This concern is relevant as the sensing and computation components of IMDs become very small (i.e., 1 mm or smaller). In light of these concerns, a Wireless Power Transfer (WPT) system would appear to be a promising solution

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Discussion

Conclusion