Ultra-compact Clamp-on Liquid Level Sensor based on a Low-Voltage CMUT

Merbeler, Fabian; Anzinger, Sebastian; Bretthauer, Christian; Kupnik, Mario

doi:10.1109/sensors47125.2020.9278743

Cited by 5 publications

(1 citation statement)

References 13 publications

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“…This makes this type of microelectromechanical systems (MEMS) one of the most promising candidates for advancing the state of the art in many fields, such as high-intensity focused ultrasound (HIFU) therapy [ 2 ], medical imaging (e.g., 3D imaging [ 3 ], intravascular ultrasound (IVUS) imaging [ 4 , 5 , 6 ], intracardiac echocardiography (ICE) imaging [ 7 ], and strongly emerging photoacoustic imaging [ 8 , 9 ]), and ultrasound computer tomography [ 10 ]. Furthermore, diverse industrial applications, such fill-level sensing [ 11 ] and flow-metering [ 12 ], structural health monitoring [ 13 , 14 ], resonant gas sensing [ 15 , 16 , 17 ], and consumer applications (e.g., fingerprint sensors) [ 18 ], are advanced due to CMUTs. A comprehensive review on CMUTs is given by Brenner et al [ 19 ].…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2022

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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.

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