Fabrication and Evaluation of MUT‐Type Acoustic Metamaterial for Impedance Matching

A micromachined ultrasonic transducer (MUT)‐type acoustic metamaterial that achieved acoustic impedance matching between materials with different acoustic impedances was successfully fabricated. The fabricated device consisted of a thin membrane that vibrated when acoustic waves impinged on the surface of the device, along with tapered trench structures located beneath the membrane. The device fabrication process consisted of seven steps, using four silicon wafers. An acoustic evaluation of the system with the fabricated MUT‐type acoustic metamaterial showed that the water‐to‐silicon transmission property was 30% higher than that of a system without the MUT‐type acoustic metamaterial. This result confirms that MUT‐type acoustic metamaterials are useful for matching the acoustic impedance between materials with different acoustic impedances. © 2024 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC.