Coding Piezoelectric Metasurfaces

The manipulation of acoustic waves plays an important role in a wide range of applications. Currently, acoustic wave manipulation typically relies on either acoustic metasurfaces or phased array transducers. The elements of traditional metasurfaces are usually designed with complex artificial structures and limited by the additive manufacturing capability, which are difficult to apply in MHz frequency underwater acoustic wave control. Phased array transducers, suffering from high-cost and complex control circuits, are usually limited by the array size and the filling ratio of the control units. Coding piezoelectric metasurfaces are reported; three wave functionalities, including beam steering, beam focusing, and vortex beam focusing are demonstrated; and acoustic tweezers and ultrasound imaging are eventually realized. The information coded on the piezoelectric metasurfaces herein is frequency independent and originates from the polarization directions, pointing either up or down, of the piezoelectric materials. Such a piezoelectric metasurface is driven by a single electrode and acts as a controllable active sound source, which combines the advantages of acoustic metasurfaces and phased array transducers while keeping the devices structurally simple and compact. The coding piezoelectric metasurfaces lead to potential technological innovations in underwater acoustic wave modulation, acoustic tweezers, biomedical imaging, industrial nondestructive testing, and neural regulation.