Dynamic FEM analysis of multiple cMUT cells in immersion

Bayram, Barış
Ergun, AS
Oralkan, O
Khuri-Yakub, BT
This paper reports on the accurate modeling of immersion capacitive micromachined ultrasonic transducers (cMUTs) using the time-domain, nonlinear finite element package, LS-DYNA, developed by Livermore Software Technology Corporation (LSTC). A capacitive micromachined ultrasonic transducer consists of many cMUT cells. In this paper, a square membrane was used as the unit cell to cover the transducer area by periodic replication on the surface. The silicon membrane, silicon oxide post and insulation layer were modeled, and the contact region was defined on the membrane and the substrate surfaces. The 3-D finite element model also included a 500 mu m-thick substrate and the acoustic fluid medium, to take into account two main sources of coupling in cMUTs: Scholte wave propagating at the solid-fluid interface and Lamb wave propagating in the substrate. A highly efficient perfectly matched layer (PAIL) absorbing boundary condition was designed for the acoustic medium to truncate the computational domain. The cMUT was biased in-collapse or out-of-collapse with an applied potential difference between the membrane and substrate electrodes: a rectangular pulse excitation was then used for the conventional, collapsed or collapse-snapback operations of the cMUT. Collapsed operation of the cMUT generated six times greater acoustic output pressure (641 kPa) than the conventional operation (107 kPa) at both the same bias voltage (83 V) and the pulse amplitude (+5 V). The vacuum backing and impedance-matched backing were compared to determine the influence of wave reflections from the bottom of the substrate in the collapsed operation. The dynamic FEN,I results were compared to the experimental results for conventional and collapse-snapback operations by applying step voltages on biased cMUT membranes. The acoustic output pressure measurements of the cMUT were performed with a hydrophone. The hydrophone calibration data was used to find the sensed pressure. Taking the attenuation and diffraction losses into account, the pressure on the cMUT surface was extracted. The cMUT generated 348 kPa and 1040 kPa in the conventional and collapse-snapback operations, respectively, and good agreement was observed with the dynamic FEM results.


Bayram, Barış; Kupnik, Mario; Khuri-Yakub, Butrus T. (2006-01-01)
This paper reports on the finite element analysis (FEA) of crosstalk in capacitive micromachined ultrasonic transducer (CMUT) arrays. Finite element calculations using a commercial package (LS-DYNA) were performed for an immersed I-D CMUT array operating in the conventional and collapsed modes. LS-DYNA was used to model the crosstalk in CMUT arrays under specific voltage bias and excitation conditions, and such a modeling is well worth the effort for special-purpose CMUT arrays for ultrasound applications s...
Experimental characterization of collapse-mode CMUT operation
Oralkan, Omer; Bayram, Barış; Yaralioglu, Goksen G.; Ergun, A. Sanli; Kupnik, Mario; Yeh, David T.; Wygant, Ira O.; Khuri-Yakub, Butrus T. (2006-08-01)
This paper reports on the experimental characterization of collapse-mode operation of capacitive micromachined ultrasonic transducers (CMUTs). CMUTs are conventionally operated by applying a direct current (DC) bias voltage less than the collapse voltage of the membrane, so that the membrane is deflected toward the bottom electrode. In the conventional regime, there is no contact between the membrane and the substrate; the maximum alternating current (AC) displacement occurs at the center of the membrane. I...
Dynamic analysis of CMUTs in different regimes of operation
Bayram, Barış; Ergun, AS; Yaralioglu, GG; Khuri-Yakub, BT (2003-01-01)
This paper reports on dynamic analysis of an immersed single capacitive micromachined ultrasonic transducer (CMUT) cell transmitting. A water loaded 24 mum circular silicon membrane of a transducer was modeled. The calculated collapse and snapback voltages were 80 V and 50 V, respectively. The resonance frequency, output pressure and nonlinearity of the CMUT in three regimes of operation were determined. These regimes were: a) the conventional regime in which the membrane does not make contact with the subs...
Deep-trench RIE optimization for high performance MEMS microsensors
Aydemir, Akın; Turan, Raşit; Department of Physics (2007)
This thesis presents the optimization of deep reactive ion etching process (DRIE) to achieve high precision 3-dimensional integrated micro electro mechanical systems (MEMS) sensors with high aspect ratio structures. Two optimization processes have been performed to achieve 20 μm depth for 1 μm opening for a dissolved wafer process (DWP) and to achieve 100 μm depth for 1 μm opening for silicon-on-glass (SOG) process. A number of parameters affecting the etch rate and profile angle are investigated, including...
Finite element modeling of capacitive micromachined ultrasonic transducers
Yaralioglu, GG; Bayram, Barış; Nikoozadeh, A; Khuri-Yakub, BTP (2005-01-01)
Transducers based on piezoelectric crystals dominate the biomedical ultrasonic imaging field. However, fabrication difficulties for piezoelectric transducers limit their usage for complex imaging modalities such as 2D imaging, high frequency imaging, and forward looking intravascular imaging. Capacitive micromachined ultrasonic transducers (CMUTs) have been proposed to overcome these limitations and they offer competitive advantages in terms of bandwidth and dynamic range. Further, the ease of fabrication e...
Citation Formats
B. Bayram, A. Ergun, O. Oralkan, and B. Khuri-Yakub, “Dynamic FEM analysis of multiple cMUT cells in immersion,” Montreal, CANADA, 2004, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/54488.