Tunable acoustic metasurface based on tunable piezoelectric composite structure

Abstract

Due to the potential engineering needs, the passive tunable metasurfaces with a high performance equivalent to the active phased array is worthy of research. Here, a passive ultrathin metasurface unit composed of a piezoelectric composite structure (PCS) connected to an external capacitor, which can modulate the phase of the transmitted acoustic waves at a deep subwavelength scale only by controlling the external capacitor but without changing the structure, is proposed. Then, a tunable acoustic metasurface composed of 20 identical PCSs is introduced to realize three acoustic functions, beam steering, beam focusing, and tweezer-like beam generating, just by changing the external capacitors. The phase-control abilities of the PCS unit and three functions of the designed metasurface are proved both numerically and experimentally. This study provides the possibility to design ultrathin tunable acoustic metasurfaces with the ability of precise control and passive materials.

Novel phononic-crystal-arrayed acoustic metalens for long beam focusing in multi-band

“…[13][14][15][16][17][18] A significant challenge that has yet to be achieved in both theoretical models and experimental validation is to achieve long beam projection of lowfrequency-band acoustic waves with long wavelengths, similar to active parameter control, through the smallest possible metastructures. [19][20][21][22][23] This letter introduces a novel theoretical method for designing a two-dimensional acoustic metalens by means of multiple scattering theory. The proposed approach is validated through both finite element simulations and experimental verification.…”

Acoustic metalens with switchable and sharp focusing

“…[7][8][9][10][11] Usually, the studies of dynamically tunable or switchable acoustic metalens were based on phase-gradient metasurfaces, and were realized through the continuous tuning of the resonant-cavity volume, [12][13][14][15][16] the dynamic modulation of a rotating airflow, 17) or integrating piezoelectric materials into the meta-atoms. [18][19][20] An alternative method to realize broadband tunable focusing is based on the utilizing of coding acoustic metasurfaces. 21,22) Although interesting and switchable focusing effect was convincingly demonstrated in these works, they were designed for air-borne sounds only.…”