This article presents a thorough analysis and an equivalent circuit model of a wireless power transfer system utilizing magnetoelectric (ME) effects. Based on two-port theory, explicit analytical solutions of, (i) the ME coefficient α ME (defined by the derivative of the generated electric field with respect to the applied magnetic field), and (ii) the power transferred to a load resistance, are derived and rigorously validated by experiments. The compact closed-forms of the optimal load and its corresponding maximum output power are developed. In our particular experimental system, a power of ∼10 mW is attained at an applied magnetic flux density of 318.9 µT with a laminated composite made by two Galfenol and one PZT layers. While α ME is widely used in the literature as a standard criterion to evaluate the performance of a ME transducer, we reveal that larger α ME does not always ensure higher optimum power delivered to the load. Instead, we quantify the essential influences of each magnetostrictive and piezoelectric phases on the maximum obtainable power. We show that the transduction factor between the magnetic and mechanical domains is often more critical for power optimization than the mechanical-electrical transduction factor as it determines and limits the maximum power available for transfer to a resistive load.

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.

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This paper presents a complete equivalent circuit model for a wireless power transfer concept utilizing a center-clamped piezoelectric cantilever beam with magnetic tip masses as a receiver. The analytical solution for the power delivered to a load resistance is given as a function of material properties, beam characteristics and external magnetic field strength. The lumped element model is experimentally verified. The efficiency of the system is thoroughly investigated and validated. The essential effect of the coil resistance is highlighted. The analyses show that optimization of transmitter coil size and geometry of the piezoelectric transducer has a significant impact on the transduction factor between the magnetic-mechanical-electrical domains, which greatly improves the transmission efficiency. Finally, the model for evaluating the efficiency is generalized for other similar structures.