Magnetically Coupled Microelectromechanical Resonators for Low-Frequency Wireless Power Transfer

This paper demonstrates a breakthrough wireless power transmission (WPT) approach using magnetically coupled electromechanical resonators affording power transfer at distances up to 7 times the characteristic size of the resonator magnet. In contrast to resonant inductive coupled WPT, this concept uses mechanical resonators rather than electrical resonators; permanent magnets rather than current-generated magnetic fields; and low-audio frequencies rather than RF frequencies. Compact voice-coil electromechanical resonators using vibrating permanent magnets are designed, fabricated and tested. Operating at 503 Hz with mechanical Q-factors of only 73, this first-generation prototype demonstrates 121 µW of power transfer with 18.5% efficiency over a distance of 2x the resonator size. Also, a power density of 1.4 mW/cm
³
is achieved. The significance of this work is the opportunity to safely charge wearables and/or biomedical implants using compact power receivers.