Abstract
Acoustic metasurfaces, exhibiting superior performance with subwavelength thickness, are ideal alternatives for functionalities such as wavefront modulation and acoustic energy trapping, etc. However, most of the reported acoustic metasurfaces were passive. Here a magnetically tuned mechanism is reported for membrane-type acoustic metamaterials. Harnessing the geometric nonlinearity of membrane structures, the transmission spectrum is both theoretically and experimentally tuned over broadband by an external static magnetic force. Simultaneously, the phase profiles can be readily tailored by the magnetic stimulus. Further, a magnetic-control multifunctional metasurface is proposed for low-frequency wave manipulation. By switching the magnetic force distribution, multi extraordinary phenomena, such as acoustic wave redirecting, focusing, bending, etc., are realized without changing the physical structure. Besides, it is demonstrated the proposed metasurface, at deep subwavelength scale (~1/85λ), supports anomalous reflected wave manipulation over a wide band. These results open up new degrees of freedom to steer acoustic wave and pave a way for designing active acoustic devices.
Highlights
Recent years have witnessed the rapid development of artificially structured materials in which extraordinary phenomena are discovered[1,2,3,4,5,6,7,8,9,10,11,12,13,14,15]
Driven by the development of tunable metamaterials, the research agenda is shifting towards designing acoustic devices with tunable and switchable
The results show the versatility of the tunable acoustic metasurfaces and have potential in acoustic imaging, cloaking and sensing applications
Summary
Recent years have witnessed the rapid development of artificially structured materials in which extraordinary phenomena are discovered[1,2,3,4,5,6,7,8,9,10,11,12,13,14,15]. The incident wave was constrained to propagate along the curled channels, which resulted in arbitrary phase delay and a high refractive index Resorted to these unique properties, fascinating acoustic wave manipulation, such as wave bending[17], anomalous reflection and refraction[18,19,20,21,22,23], converting radiation pattern[24], etc., have been demonstrated both theoretically and experimentally. Most reported acoustic metasurfaces are passive and hampered by the lack of tuning capabilities Another limitations of the subwavelength structures are the narrow operative band due to the high dispersion. The results show the versatility of the tunable acoustic metasurfaces and have potential in acoustic imaging, cloaking and sensing applications
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