Dresden 2020 – scientific programme

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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 2: Focus: High-resolution Lithography and 3D Patterning (Part I) (joint session KFM/CPP/HL)

KFM 2.8: Talk

Monday, March 16, 2020, 12:30–12:50, TOE 317

Acoustic Impedance Matching on Ultrasonic Devices using Additive Manufacturing — •Severin Schweiger, Sandro Koch, Marcel Krenkel, and Marco Kircher — Fraunhofer Institute for Photonic Microsystems, Dresden, Germany

Acoustic impedance matching layers are attached to ultrasonic transducers to increase acoustic energy transmission into the load medium. A capacitive micromachined ultrasonic transducer (CMUT) emits sound via electrostatic deflection of a flexible electrode. Especially air-coupled CMUTs with protective or focusing layers exhibit a notable impedance mismatch. We propose a new approach to fabricate impedance matching metamaterials with low load-side specific acoustic impedance values, by employing a photolithographic additive manufacturing technology using two photon absorption. It will enable improved impedance matching, which has a beneficiary effect on acoustic bandwidth, efficiency and sensitivity of the CMUT. The center operating frequency of the CMUT can be influenced via this process as well. The technology also allows for direct fabrication of microstructures on the chip, foregoing any adhesion layers that disturb the impedance matching and enabling the protective and/or focusing aspects of the layer. This contribution will show analytic and FEM simulations of CMUTs with matching layers. Fabricated impedance matching layer samples and on chip fabrication will be presented as well. Electric impedance and acoustic measurements are in progress and will be featured accordingly.