Design and Realization of Void-centric Zone Plate Ultrasonic Transducer: Considering Structural Vibration of Piezoelectric Metamaterials

Abstract We developed and experimentally realized a novel type of focal transducer called a void-centric zone plate ultrasonic transducer (VZPUT). Although VZPUT is a planar transducer, it can focus ultrasound and control the focal length using a single-channel electric network. Further, unlike a classical Fresnel zone plate, the VZPUT has space for an imaging probe at the center, making it useful for therapeutic focused ultrasound (FUS). To realize VZPUT, we develop a novel void-centric zone plate (VZP) that allows design freedom for the radius of the space at the center. Then, we fabricate the piezoelectric VZP, an acoustic metamaterial, considering its structural vibration modes that appear within the operating frequency range. The VZPUT demonstrated applicability to therapeutic FUS in that it could control the focal point by the operating frequency with real-time monitoring images from the imaging probe mounted at the center.