Miniature Electrodynamic Wireless Power Transmission Receiver Using a Micromachined Silicon Suspension

We present the design, modeling, fabrication, and experimental characterization of an electrodynamic wireless power transmission (EWPT) receiver for low-frequency (< 1 kHz), near-field wireless power transmission. The device utilizes a bulk-micromachined silicon serpentine suspension, two NdFeB magnets and two precision-manufactured coils. The architecture of the transducer is designed to maximize the electrodynamic coupling coefficient while maintaining a low mechanical resonant frequency in order to maximize the power density for low-frequency wireless power transmission. An equivalent lumped-element circuit model is established to parameterize the system and to predict the output performance of the proposed system. A prototype device is fabricated, assembled and tested, and the results are compared with the model prediction. The 0.31 cm³ device generates 2.46 mW average power (7.9 mW <inline-formula> <tex-math notation="LaTeX">$\cdot $ </tex-math></inline-formula> cm⁻³ power density) at 4 cm distance from a transmitter coil operating at 821 Hz and safely within allowable human exposure limits. This data corresponds to a normalized power density of 21.9 mW <inline-formula> <tex-math notation="LaTeX">$\cdot $ </tex-math></inline-formula> cm<inline-formula> <tex-math notation="LaTeX">$^{-3}\,\,\cdot $ </tex-math></inline-formula> mT⁻², which is 44% higher than similar reported devices. Based on these results, this device shows great suitability for wirelessly charging mobile, wearable and bio-implantable devices. [2020-0161]