Acoustic Power Transfer and Communication With a Wireless Sensor Embedded Within Metal

Thick metal barriers prevent the use of conventional electromagnetic wireless power transfer due to Faraday shielding effects. Here, for the first time, we demonstrate power transfer to and communication with a compact wireless sensor transponder fully embedded within a solid piece of metal through the use of ultrasonic waves. This technique is an important innovation for applications, such as structural health monitoring of solid metal structural components, which would be weakened by the presence of holes for wiring. The embedded sensor system consists of a single piezoelectric transducer used for both power and data communication, along with an energy storage unit and associated charging circuitry, as well as a representative sensor and sensor data acquisition electronics. The entire sensor transponder was packaged within a compact volume of 11.9 cm
³
(0.73 in
³
) and can be further miniaturized to millimeter-scale sizes with the use of widely available system-on-chip technologies. The measured power transfer and sensor data results were found to closely match modeling results, achieving a power transfer efficiency of 33% at 440 kHz, showcasing the feasibility and potential of this approach.