Ultrathin, High Sensitivity Polymer-based Capacitive Micromachined Ultrasound Transducers (polyCMUTs) for Acoustic Emission Sensing in Fiber Reinforced Polymers

Welsch, Jonas; Cretu, Edmond; Rohling, Robert; Gerardo, Carlos D.

doi:10.1109/ius54386.2022.9958226

Cited by 4 publications

(2 citation statements)

References 7 publications

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“…al [24] and Welsch et. al [37]. However, there were several changes to account for recent improvements of the polyCMUT fabrication process.…”

Section: B Fabricationmentioning

confidence: 99%

“…The S1813 is then washed away in an Acetone bath. The next layer, called the SU-8 base layer, is needed to even-out the topology of the fabricated layers (see [37]). Because the following first membrane layer should be as thin as possible, the areas between the sacrificial layer structures need to be filled with slightly higher or at least the same height as all previous layers stacked on top (roughly 320 nm).…”

Section: B Fabricationmentioning

confidence: 99%

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Studying the Effects of Mutual Acoustic Impedance on the Performance of Polymer-Based CMUTs

Angerer,

Welsch,

Gerardo

et al. 2024

IEEE Open J. Ultrason., Ferroelect., Freq. Contr.

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The objective of this work was to investigate changes in the acoustic characteristics of micromachined transducers caused by acoustic cross-coupling between cells. We used hexagonal, polymer-based capacitive micromachined ultrasonic transducers (polyCMUTs) consisting of 127 cells connected in parallel. The distances between the cells were varied, while the cell dimensions and number of cells remained constant. The resulting changes in characteristics were evaluated in terms of peak frequency f pk , fractional bandwidth F BW , peak transmit sensitivity S pk and opening angle Φ t . The study relies on results from an analytic multicell model (MCM) which considers cross-coupling effects between cells through a mutual acoustic impedance matrix. The results are compared with finite element (FE) analyses and measurements on fabricated prototypes. The manufacturing processes used to produce the polyCMUT prototypes are explained in detail. We found significant changes in all acoustic characteristics: as cell spacing increases, f pk and Φ t decrease, while S pk gradually rises to about twice the initial value. The F BW varies due to the change in f pk , peaking at small to intermediate cell-to-cell distances. While both modeling approaches cover the general effects, discrepancies in comparison to the measurements were identified. The FE model provided better fits than the analytic MCM, albeit at significantly higher computational costs. The effects on the acoustic characteristics were found strongest at lower frequencies and if many cells are in close proximity to each other. Hence, rotational symmetric or square transducers operating at lower frequencies are affected most. The results demonstrate that design approaches based on modeling single cells may lead to significant deviations from design goals. Both, analytic and FE models are suitable tools to estimate the effects of acoustic interactions and to predict the performance. This aids in meeting design requirements of micromachined ultrasound transducers consisting of multiple radiators.

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“…al [24] and Welsch et. al [37]. However, there were several changes to account for recent improvements of the polyCMUT fabrication process.…”

Section: B Fabricationmentioning

confidence: 99%

Section: B Fabricationmentioning

confidence: 99%