Metamaterial-enabled wireless and contactless ultrasonic power transfer and data transmission through a metallic wall

Wireless ultrasonic power transfer and data transmission through a metallic wall requires a direct contact of transducers with the wall owing to the significant impedance mismatch between the surrounding fluid and the wall. Here, a pillar-based acoustic metamaterial is proposed for wireless and contactless ultrasonic power transfer and data transmission through a metallic wall by leveraging the pillar's vertical elongation mode. Experiments conducted in water demonstrate a 33-fold power transmission enhancement (from 2% to around 66%) at approximately 450 kHz through a 1-mm-thick metallic wall. Furthermore, our experiments show that a commercial light-emitting diode can be illuminated by harvesting the metamaterial-enhanced transmission of ultrasonic energy, which would not have been possible with the metallic wall alone even at an input voltage approximately 5 times greater. In addition, data transmission through the metallic wall is demonstrated by employing amplitude-shift keying modulation to transmit an image, showcasing the remarkable improvement in image quality enabled by the metamaterial. This study paves the way for a future generation of wireless and contactless ultrasonic power transfer and data-transmission applications.