Dynamic acoustic metasurfaces based on magnetic levitation

Tunable acoustic metasurfaces have garnered substantial attention in recent years, offering an approach to manipulate acoustic waves efficiently. Despite the rapid progress in this field, obtaining a dynamic acoustic metasurface with a noncontact design remains a challenging goal. Here, we theoretically propose and experimentally demonstrate dynamic acoustic metasurfaces designed using magnetic levitation. The meta-atom consists of an acoustic cavity with a floating magnet. By varying the magnitude of the current in a coil located at the bottom of the cavity, the position of the magnet can be dynamically adjusted, effectively changing the height of the cavity. The reflection phase can thus be continuously modulated in real time, enabling the switching of versatile functionalities. Our work opens up a magnetic levitation approach towards intelligent acoustic metasurfaces with noncontact control.