Tunable reflected acoustic wave front modulated with piezoelectric metasurfaces

Abstract Wave front engineering realized through metasurface synthesis has attracted considerable attention in recent years. Acoustic metasurfaces in deep subwavelength scale have promising potentials in applications such as acoustic focal lenses and acoustic cloaking. Most existing devices, however, lack the tunability in real time. In this paper, an adaptive acoustic metasurface taking advantage of the two-way electro-mechanical coupling of piezoelectric transducers is developed, which enables the manipulation of acoustic waves adaptively. The proposed metasurface consists of units constructed from membranes with back air cavities, wherein the membrane strength is controlled by piezoelectric transducer. With membrane strengths tailored in a tunable manner, an accurate phase profile along the acoustic metasurfaces can be designed, yielding acoustic metasurfaces to steer reflected acoustic waves online without modification of the underlying physical structures. We demonstrate that the adaptive acoustic metasurfaces can successfully achieve abnormal reflections, planar focal lenses and self-accelerating beams. The acoustic cloaking realized by our adaptive acoustic metasurfaces is also illustrated to further manifest the design versatility.