Schweiger, SeverinSeverinSchweigerKoch, SandroSandroKoch2022-03-142022-03-142018https://publica.fraunhofer.de/handle/publica/40322310.1109/ISSE.2018.8443702This review analyses methods for acoustic impedance matching that are used on ultrasonic transducers to increase acoustic energy transmission into the load medium. A capacitive micromachined ultrasonic transducer (CMUT) emits sound via electrostatic deflection of a membrane electrode. Especially air-coupled CMUTs exhibit a notable impedance mismatch. We propose a new approach to fabricate impedance matching metamaterials with extremely low load-side specific acoustic impedance values and an extraordinary level of control over gradient attributes, by employing a photolithographic additive manufacturing technology. It will enable gradient impedance matching, which has a beneficiary effect on acoustic bandwidth, efficiency and sensitivity of the CMUT.en621conference paper