Active Labyrinthine Transmissive Ultrasonic Metamaterial

Abstract It is highly desirable to engineer multiple operational states in a single metamaterial device. Here, we present a powerful approach to transform a conventionally passive metamaterial into an actively reconfigurable metamaterial, using dynamic standalone unit cells, called dynamic meta-bricks. These 3D-printed meta-bricks comprise an actuatable internal magnetorheological elastomeric flap, designed for active ultrasonic (40 kHz) transmission and modulation. Computational assembly of dynamic and static meta-bricks generates controllable hybrid metamaterial stacks, within a composite metasurface. We demonstrate for the first time, dynamic acoustic levitation with a transmissive metasurface, showcasing that partial peripherally localised actuation, can enable full array operational dynamicity. Without re-assembly, actuating the dynamic meta-bricks shifts an acoustically trapped bead in mid-air in real-time, while maintaining acoustic levitation. This work uncovers the potential for strategic synergy between active and passive reconfigurability, opening novel possibilities to develop versatile, integrated, multifunctional metamaterials with enhanced degrees of freedom in design and control.