Tunable directivity in metamaterials with reconfigurable cell symmetry

We introduce a strategy to attain reconfigurable, highly focused, subwavelength wave patterns in cellular metamaterials via electromechanical tuning of their microstructures. The metamaterial cells feature a population of auxiliary microstructural elements instrumented with piezoelectric patches connected to negative capacitance shunting circuits. By tuning the circuital characteristics of selected subsets of shunts, we relax the symmetry of the cell material property landscape, thus affecting the global directivity and enabling a plethora of wave manipulation capabilities. The acoustic reconfiguration is decoupled from other mechanical functions and is carried out without affecting the shape or the static properties of the host cellular structure. (C) 2015 AIP Publishing LLC.