Reconfigurable acoustic focusing based on origami-inspired metalens

In the realm of acoustics, the ability to focus sound using metalenses holds significant promise for various applications. However, contemporary research on such focusing lenses predominantly relies on static structures, lacking adaptability and reconfigurability. In this study, we introduce an innovative, origami-inspired reconfigurable gradient metalens. The novel design comprises foldable V-shaped unit cells, each boasting high transmission efficiency and spanning a full $2\pi$ phase shift within the target frequency range. Notably, by merely adjusting the folding angle, we can achieve phase differences of $\pi$ between two unit cells at different frequencies, facilitating a versatile and selectable focusing effect characterized by a variable focal length. To further the concept, we demonstrate a metalens using eight distinct foldable unit cells, aiming to achieve pinpoint acoustic focusing through varying folding configurations. To validate this approach, we present evidence from both numerical simulations and experimental measurements of our origami-based reconfigurable metalens. The methodology offers a new perspective in constructing adaptable gradient metalenses and potential applications in acoustic sensors, energy collection devices and imaging systems.