{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,17]],"date-time":"2026-10-17T16:24:01Z","timestamp":1792254241739,"version":"4.4.0"},"reference-count":46,"publisher":"MDPI AG","issue":"6","license":[{"start":{"date-parts":[[2025,5,25]],"date-time":"2025-05-25T00:00:00Z","timestamp":1748131200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Micromachines"],"abstract":"<jats:p>Ultrasonic applications such as non-destructive testing, biomedical imaging or range measurements are currently based on piezoelectric bulk transducers. Yet, these kinds of transducers with their mm to cm dimensions are rather impractical in fields in which both frequencies in the kHz region and small-feature sizes are required. This fact mainly relates to the inverse relationship between the resonance frequency constant and the transducers\u2019 dimension, yielding a higher frequency and attenuation with a decreasing size. Piezoelectric micromachined ultrasonic transducers (PMUTs), in comparison, incorporate a small-scale \u00b5m design while preserving the operating frequency in the desired kHz range. This contribution presents the detailed manufacturing of such a PMUT with a multiple ring electrode\u2011based structure to additionally adjust the sound pressure fields. The PMUT will be characterized by its deflection in air along with the characterization of the piezoelectric material lead zirconate titanate (PZT) itself. The measurements showed a maximum polarization of 21.8 \u00b5C\/cm2 at 50 kV\/cm, the PMUT\u2019s displacement of 30.50 nm\/V in air when all electrodes are driven, and an adjustable deflection via different electrode excitations without the need for additional hardware. The ring design also offered the possibility to emit two distinct frequencies simultaneously. These results demonstrate the potential of the designs for small-feature-size applications as they are in high demand for implantable devices, miniaturized ultrasonic-based communication or drug delivery.<\/jats:p>","DOI":"10.3390\/mi16060623","type":"journal-article","created":{"date-parts":[[2025,5,25]],"date-time":"2025-05-25T20:39:36Z","timestamp":1748205576000},"page":"623","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":8,"title":["Multiple Ring Electrode-Based PMUT with Tunable Deflections"],"prefix":"10.3390","volume":"16","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-4886-1091","authenticated-orcid":false,"given":"Jan","family":"Helmerich","sequence":"first","affiliation":[{"name":"Laboratory for Electrical Instrumentation and Embedded Systems, Department of Microsystems Engineering (IMTEK), University of Freiburg, 79110 Freiburg, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5039-5045","authenticated-orcid":false,"given":"Manfred","family":"Wich","sequence":"additional","affiliation":[{"name":"Laboratory for Electrical Instrumentation and Embedded Systems, Department of Microsystems Engineering (IMTEK), University of Freiburg, 79110 Freiburg, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Annika","family":"Hofmann","sequence":"additional","affiliation":[{"name":"Laboratory for Electrical Instrumentation and Embedded Systems, Department of Microsystems Engineering (IMTEK), University of Freiburg, 79110 Freiburg, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5304-4213","authenticated-orcid":false,"given":"Thomas","family":"Schaechtle","sequence":"additional","affiliation":[{"name":"Laboratory for Electrical Instrumentation and Embedded Systems, Department of Microsystems Engineering (IMTEK), University of Freiburg, 79110 Freiburg, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4806-9838","authenticated-orcid":false,"given":"Stefan Johann","family":"Rupitsch","sequence":"additional","affiliation":[{"name":"Laboratory for Electrical Instrumentation and Embedded Systems, Department of Microsystems Engineering (IMTEK), University of Freiburg, 79110 Freiburg, Germany"},{"name":"BrainLinks-BrainTools, 79110 Freiburg im Breisgau, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2025,5,25]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Rupitsch, S.J. 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