Through-package wireless powering via piezoelectric micromachined ultrasonic transducers

The paper reports on a chip-scale wireless power transfer method using elastic waves traveling though plastic packaging media with arbitrary thicknesses. Piezoelectric micromachined ultrasonic transducers (pMUTs) are utilized for harnessing the longitudinal bulk acoustic waves generated by an external acoustic probe. Aluminum nitride pMUTs are developed through a simple and CMOS compatible process. In order to emulate the effect of the package, PLA plastic pieces with various thicknesses are 3D printed and used in the experiments. PMUTs as small as 200×200 μm² resulted in -30 dB power transfer efficiency in the case of a 1 mm thick PLA package.