A reconfigurable active acoustic metalens

Acoustic metasurfaces have enabled unprecedented control over acoustic waves, offering opportunities in areas such as holographic rendering, sound absorption, and acoustic communication. Despite the steady progress made in this field, most acoustic metasurface designs are passive in that they only provide static functionalities. Here, a reconfigurable active acoustic metalens is implemented to showcase scanning of the focus along arbitrary trajectories in free space with the help of a previously developed active acoustic metasurface platform. Each unit cell of the metasurface contains a cavity, whose size can be tuned continuously by a dynamic control system to adjust the phase of the reflected wave. While this work focuses on beam focusing, it could hold great promise for a wide range of applications including acoustic levitation and tweezers.