Periodic finite element/boundary element modeling of capacitive micromachined ultrasonic transducers

Ballandras, S.; Wilm, M.; Daniau, W.; Reinhardt, Alexandre; Laude, Vincent; Armati, Raphaël

doi:10.1063/1.1839634

Cited by 32 publications

(19 citation statements)

References 9 publications

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“…To analyze the dispersion behavior of the 1D array transducer, the model is divided into elementary cells and periodic boundary conditions are applied to the interfaces between cells [29,30] . Constraints are imposed on the displacements and electric potential to enforce periodicity and continuity as:…”

Section: Boundary Conditionsmentioning

confidence: 99%

Effect of subdicing on the dispersion and resonance behavior of elastic guided waves in 1D array ultrasound transducers

2009

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1D array ultrasound subdicing is a common fabrication practice to avoid the presence of lateral modes near the center frequency of the transducer. The objective of this study is to theoretically analyze the effect of subdicing depth and width on the dispersion and resonance behavior of elastic guided wave propagation in 1D array transducers. The transducer is modeled as a periodic structure with the representative cell composed of one element. A semi-analytical finite-element (SAFE) method is derived to obtain the dispersion curves, group velocity and resonance mode shapes of a piezoelectric structure with arbitrary cross-section and periodic boundary conditions. Results indicate that resonant modes can occur at cutoff frequencies (wavenumber k = 0), where the phase velocity is infinite. Moreover, another interesting resonance behavior at zero-group-velocity (ZGV) points (wavenumber k ≠ 0) is observed where the phase velocity is finite. Theoretical results show that subdicing increases the number of waveguide modes, lowers the cut-off frequencies, increases the number of ZGV points and lowers the group velocities for flexural and extensional modes. Lower values of subdicing depth tend to increase the cut-off frequencies, but subdicing width has a minor effect on the dispersion curves. These important changes of the dispersion behavior are likely to influence the resonance characteristics and the bandwidth of the transducer. The analysis presented in this study provides a useful tool to optimize the design of 1D array ultrasound transducers and to gain better understanding of the complicated acoustic behavior of 1D array ultrasound transducers

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Section: Boundary Conditionsmentioning

confidence: 99%

Effect of subdicing on the dispersion and resonance behavior of elastic guided waves in 1D array ultrasound transducers

2009

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“…For the CMUTs with a vacuum cavity, there is no squeeze-film damping between the membrane and substrate. 19 The main energy dissipation is the acoustic radiation into its surrounding medium from one side of the membrane, 20,21 which can be equivalent to a virtual added mass on the membrane. 21,22 The resonant frequency with air damping effects can be given as: where, β is known as the added virtual mass factor, 22 ρ f is density of the fluid (the air in this study); R, h and ρ m are the parameters of the CMUT membrane.…”

Section: B Effect Of Air Dampingmentioning

confidence: 99%

Capacitive micromachined ultrasonic transducer for ultra-low pressure measurement: Theoretical study

Zhao

Jiang

et al. 2015

AIP Advances

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Ultra-low pressure measurement is necessary in many areas, such as high-vacuum environment monitoring, process control and biomedical applications. This paper presents a novel approach for ultra-low pressure measurement where capacitive micromachined ultrasonic transducers (CMUTs) are used as the sensing elements. The working principle is based on the resonant frequency shift of the membrane under the applied pressure. The membranes of the biased CMUTs can produce a larger resonant frequency shift than the diaphragms with no DC bias in the state-of-the-art resonant pressure sensors, which contributes to pressure sensitivity improvement. The theoretical analysis and finite element method (FEM) simulation were employed to study the relationship between the resonant frequency and the pressure. The results demonstrated excellent capability of the CMUTs for ultra-low pressure measurement. It is shown that the resonant frequency of the CMUT varies linearly with the applied pressure. A sensitivity of more than 6.33 ppm/Pa (68 kHz/kPa) was obtained within a pressure range of 0 to 100 Pa when the CMUTs were biased at a DC voltage of 90% of the collapse voltage. It was also demonstrated that the pressure sensitivity can be adjusted by the DC bias voltage. In addition, the effects of air damping and ambient temperature on the resonant frequency were also studied. The effect of air damping is negligible for the pressures below 1000 Pa. To eliminate the temperature effect on the resonant frequency, a temperature compensating method was proposed.

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“…For modeling the HBAR resonator admittance and determining the gravimetric sensitivity of the various overtones as boundary conditions are varied, a one dimension modeling software is used based on Boundary Element Modeling (BEM) 19,20 . The free parameters tuned during the modeling process are the layer thicknesses and material properties, while the gravimetric sensitivity is extracted from the application of Eq.…”

Section: Modelingmentioning

confidence: 99%

High-overtone bulk-acoustic resonator gravimetric sensitivity: Towards wideband acoustic spectroscopy

Rabus

Friedt

Ballandras

et al. 2015

Journal of Applied Physics

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In the context of direct detection sensors with compact dimensions, we investigate the gravimetric sensitivity of High-overtone Bulk Acoustic Resonators, through modeling of their acoustic characteristics and experiment. The high frequency characterizing such devices is expected to induce a significant effect when the acoustic field boundary conditions are modified by a thin adlayer. Furthermore, the multimode spectral characteristics is considered for wideband acoustic spectroscopy of the adlayer, once the gravimetric sensitivity dependence of the various overtones is established. Finally, means of improving the gravimetric sensitivity by confining the acoustic field in a low acoustic-impedance layer is theoretically established.

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Periodic finite element/boundary element modeling of capacitive micromachined ultrasonic transducers

Cited by 32 publications

References 9 publications

Effect of subdicing on the dispersion and resonance behavior of elastic guided waves in 1D array ultrasound transducers

Effect of subdicing on the dispersion and resonance behavior of elastic guided waves in 1D array ultrasound transducers

Capacitive micromachined ultrasonic transducer for ultra-low pressure measurement: Theoretical study

High-overtone bulk-acoustic resonator gravimetric sensitivity: Towards wideband acoustic spectroscopy

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