Investigation of PDMS as coating on CMUTs for imaging

A capacitive micromachined ultrasonic transducer (CMUT), 8 MHz resonance frequency, λ/2 cell pitch 188+188 row-column addressed (RCA) array for super resolution imaging is presented. The top-and bottom electrode design features a zigzag shaped pattern to increase the active cell area for fixed plate thicknesses. The RCA CMUT has been fabricated utilising a deposit, remove, etch, multistep (DREM) process to fully separate the bottom electrodes electrically as well as anodic bonding the array to an insulating borosilicate glass wafer. Linear test elements have been characterized. Electrical measurements show a center frequency of approximately 5.5 MHz and a coupling coefficient of 7.8% for-80 V DC bias and 50 mV AC. Acoustic measurements made in immersion with a single cycle 4 MHz pulse with a-90 V DC bias demonstrate that the fabricated CMUT arrays can emit broadband ultrasound pulses.

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“…This serves to electrically insulate the elements from the water. The encapsulation procedure is described in [13].…”

Section: B Acousticmentioning

confidence: 99%

188+188 Row–Column Addressed CMUT Transducer for Super Resolution Imaging

Grass

Havreland

Engholm

et al. 2019

2019 IEEE International Ultrasonics Symposium (IUS)

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“…The bump formed in the cavity of the CMUT by the double local oxidation has a radius comprising 2/3 of the cell plate. The center frequency in water immersion is 5 MHz and the pull-in voltage V pi is 220 V. The interconnect is identical to previous presented work [7] and the CMUT is coated with a ∼ 1 µm layer of polydimethylsiloxane (PDMS) for electrical insulation. The PDMS layer is flat and has no lens effect.…”

Section: Experimental Methodsmentioning

confidence: 99%

Elimination of second-harmonics in CMUTs using square pulse excitation

Lei

Diederichsen

Hansen

et al. 2016

2016 IEEE International Ultrasonics Symposium (IUS)

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Abstract-The harmonic imaging mode is today a fundamental part of ultrasound imaging; it is not only used for suppressing the grating lobe artifact, but also to reduce many other acoustical artifacts in the ultrasound image. A vital performance parameter for accepting CMUT probes as a clinical usable transducer technology is, that it can support harmonic imaging. The large bandwidth of the CMUT is a clear advantage for harmonic imaging, but the inherent nonlinear behavior of the CMUT poses an issue as it is difficult to dissociate the harmonics generated in the tissue from the harmonic content of the transmitted signal. This work presents how proper pulse coding of a bipolar pulser, which is present in most commercial ultrasound scanners, can reduce the intrinsic generated harmonic to fundamental pressure amplitude ratio to below −35 dB, making CMUT probes usable for clinical applications.

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“…2 mm. The coating procedure is similar to the one described in [9]. Furthermore, during measurements a cylindrical PMMA holder pressing down on a rubber ring placed on top of the PCB serves as a water tank.…”

Section: Cmut Fabrication and Experimental Setupmentioning

confidence: 99%

Output pressure and pulse-echo characteristics of CMUTs as function of plate dimensions

Diederichsen

Hansen

Engholm

et al. 2017

2017 IEEE International Ultrasonics Symposium (IUS)

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Abstract-This paper presents an experimental study of the acoustic performance of Capacitive Micromachined Ultrasonic Transducers (CMUTs) as function of plate dimensions. The objective is to increase the output pressure without decreasing the pulse-echo signal. The CMUTs are fabricated with a LOCOS process, followed by direct wafer fusion bonding to a SiliconOn-Insulator (SOI) wafer. In this way, the plate thickness is determined by the SOI wafer device layer thickness, resulting in CMUTs with plate thicknesses of 2, 9.3 and 15 µm. The corresponding radii and gap heights resulting in an immersion frequency of 5 MHz and a pull-in voltage of 200 V are obtained using finite element analysis. Hydrophone and plane reflector measurements are used to assess the acoustic performance. Increasing the plate thickness from 2 µm to 15 µm decreases the pulse-echo bandwidth from >100% to 30%. A maximum in both peak-to-peak output pressure and pulse-echo signal is obtained for the 9.3 µm plate, which still has a moderate pulseecho bandwidth of 60%. The 9.3 µm plate results in a 1.9 times higher peak-to-peak output pressure and a 3.6 times higher pulse-echo signal compared to the 2 µm plate. By adjusting the plate dimensions of a CMUT it is possible to optimize its acoustic performance for medical imaging applications, including visualization of deeper structures in the body, as well as nonlinear imaging such as tissue harmonic imaging.

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Investigation of PDMS as coating on CMUTs for imaging

Cited by 13 publications

References 6 publications

188+188 Row–Column Addressed CMUT Transducer for Super Resolution Imaging

188+188 Row–Column Addressed CMUT Transducer for Super Resolution Imaging

Elimination of second-harmonics in CMUTs using square pulse excitation

Output pressure and pulse-echo characteristics of CMUTs as function of plate dimensions

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