Programmable mode conversion and bandgap formation for surface acoustic waves using piezoelectric metamaterials

A spatially reversible and programmable piezoelectric metamaterial concept is introduced for the manipulation of surface acoustic waves to achieve on-demand wave mode conversion and reflection. The concept uses an array of inductive-shunted piezoelectric elements (with gradually varying inductors in space) attached to the surface of an elastic propagation domain. The value of each inductor directly controls the phase velocity of the Rayleigh wave locally as quantified through unit cell band diagram analysis that guides the design process. By varying the spatial inductance distribution, the proposed piezoelectric metamaterial domain can be programed to convert incident surface waves into bulk shear waves or reflect them completely. The location of surface-to-bulk wave mode conversion or wave reflection can be tailored by means of the inductance distribution, and the directional behavior in space can be reversed. The proposed concept may enable novel surface acoustic wave devices and filters, via digital or analog programmable shunt circuits. Published under license by AIP Publishing.