Continuously Tunable Acoustic Metasurface for Transmitted Wavefront Modulation

Fixed properties are one thing, but the design of $t\phantom{\rule{0}{0ex}}u\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}a\phantom{\rule{0}{0ex}}b\phantom{\rule{0}{0ex}}l\phantom{\rule{0}{0ex}}e$ metasurfaces is significant for real-world applications, as an integrated, active control mechanism is much more resilient to the actual requirements of an ever-changing environment. However, design is often limited by the difficulty of finding a suitable tuning mechanism. The authors here design a tunable acoustic metasurface consisting of helical cylinders screwed into a circular plate. This screw-and-nut setup is used to obtain arbitrary phase profiles over a wide frequency range, and furthermore may inspire other sorts of designs.