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Ultra-Low-Voltage Capacitive Micromachined Ultrasonic Transducers with Increased Output Pressure Due to Piston-Structured Plates

Merbeler, Fabian ; Wismath, Sonja ; Haubold, Marco ; Bretthauer, Christian ; Kupnik, Mario (2022):
Ultra-Low-Voltage Capacitive Micromachined Ultrasonic Transducers with Increased Output Pressure Due to Piston-Structured Plates. (Publisher's Version)
In: Micromachines, 13 (5), MDPI, e-ISSN 2072-666X,
DOI: 10.26083/tuprints-00021291,
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Item Type: Article
Origin: Secondary publication DeepGreen
Status: Publisher's Version
Title: Ultra-Low-Voltage Capacitive Micromachined Ultrasonic Transducers with Increased Output Pressure Due to Piston-Structured Plates
Language: English
Abstract:

Capacitive micromachined ultrasonic transducers (CMUTs) represent an accepted technology for ultrasonic transducers, while high bias voltage requirements and limited output pressure still need to be addressed. In this paper, we present a design for ultra-low-voltage operation with enhanced output pressure. Low voltages allow for good integrability and mobile applications, whereas higher output pressures improve the penetration depth and signal-to-noise ratio. The CMUT introduced has an ultra-thin gap (120 nm), small plate thickness (800 nm), and is supported by a non-flexural piston, stiffening the topside for improved average displacement, and thus higher output pressure. Three designs for low MHz operation are simulated and fabricated for comparison: bare plate, plate with small piston (34% plate coverage), and big piston (57%). The impact of the piston on the plate mechanics in terms of resonance and pull-in voltage are simulated with finite element method (FEM). Simulations are in good agreement with laser Doppler vibrometer and LCR-meter measurements. Further, the sound pressure output is characterized in immersion with a hydrophone. Pull-in voltages range from only 7.4 V to 25.0 V. Measurements in immersion with a pulse at 80% of the pull-in voltage present surface output pressures from 44.7 kPa to 502.1 kPa at 3.3 MHz to 4.2 MHz with a fractional bandwidth of up to 135%. This leads to an improvement in transmit sensitivity in pulsed (non-harmonic) driving from 7.8 kPa/V up to 24.8 kPa/V.

Journal or Publication Title: Micromachines
Volume of the journal: 13
Issue Number: 5
Place of Publication: Darmstadt
Publisher: MDPI
Collation: 15 Seiten
Uncontrolled Keywords: capacitive micromachined ultrasonic transducer (CMUT), surface micromachining, ultra-low voltage, piston-like movement, high-efficiency output pressure
Classification DDC: 600 Technik, Medizin, angewandte Wissenschaften > 600 Technik
600 Technik, Medizin, angewandte Wissenschaften > 620 Ingenieurwissenschaften
Divisions: 18 Department of Electrical Engineering and Information Technology > Measurement and Sensor Technology
Date Deposited: 06 May 2022 11:06
Last Modified: 06 Oct 2022 11:19
DOI: 10.26083/tuprints-00021291
Corresponding Links:
URN: urn:nbn:de:tuda-tuprints-212914
SWORD Depositor: Deep Green
URI: https://tuprints.ulb.tu-darmstadt.de/id/eprint/21291
PPN: 49984422X
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