Analysis of spring softening effect on the collapse voltage of capacitive MEMS ultrasonic transducers

Maity, Reshmi; Maity, N. P.; Guha, Koushik; Baishya, Srimanta

doi:10.1007/s00542-018-4040-x

Cited by 16 publications

(4 citation statements)

References 23 publications

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“…The electrostatic force F e is calculated in accordance with Equation (5). The differential Equation (14) has been solved to achieve the membrane displacement of CMUT and can be expressed as follows:…”

Section: Membrane Modelmentioning

confidence: 99%

“…In the year 2004, Yongli Huang et al have carried out a comparative study of the performance of CMUT for three different membrane configurations [ 12 ]. A compact analytical model was proposed by R. Maity et al to calculate the dependency of collapse voltage on different physical parameters and structural features of the device [ 13 , 14 ]. In another study, the authors have used Mason’s equation to establish a circular membrane model [ 15 ].…”

Section: Introductionmentioning

confidence: 99%

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Squeeze Film Effect in Surface Micromachined Nano Ultrasonic Sensor for Different Diaphragm Displacement Profiles

Dastidar

Maity

Tiwari

et al. 2023

Sensors

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In the present paper, we have analytically explored the small variations of the local pressure in the trapped air film of both sides of the clamped circular capacitive micromachined ultrasonic transducer (CMUT), which consists of a thin movable membrane of silicon nitride (Si3N4). This time-independent pressure profile has been investigated thoroughly by solving the associated linear Reynold’s equation in the framework of three analytical models, viz. membrane model, plate model, and non-local plate model. The solution involves Bessel functions of the first kind. The Landau–Lifschitz fringing technique has been assimilated to engrave the edge effects in estimation of the capacitance of CMUT, which should be considered in the micrometer or lesser dimension. To divulge the dimension-based efficacy of the considered analytical models, various statistical methods have been employed. Our use of contour plots of absolute quadratic deviation revealed a very satisfactory solution in this direction. Though the analytical expression of the pressure profile is very cumbersome in various models, the analysis of these outputs exhibits that the pressure profile follows the displacement profile in all the cases indicating no viscous damping. A finite element model (FEM) has been used to validate the systematic analyses of displacement profiles for several radii and thicknesses of the CMUT’s diaphragm. The FEM result is further corroborated by published experimental results bearing excellent outcome.

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Section: Membrane Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Squeeze Film Effect in Surface Micromachined Nano Ultrasonic Sensor for Different Diaphragm Displacement Profiles

Dastidar

Maity

Tiwari

et al. 2023

Sensors

Self Cite

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“…Based on the assumption of rigid body motion, the resonant frequency of a CMUT cell can be estimated analytically [21]. However, the estimated resonant frequency may be inaccurate due to the assumption of rigid body motion and the influence of the spring softening effect (i.e., the reduction of the effective spring constant caused by dc biased voltage [27]). Instead of the analytical calculation of the resonant frequency, the resonant frequency calculated from the eigenfrequency study of FEM is brought into the theory shown in Section II to evaluate the sensing behavior of a CMUT cell analytically.…”

Section: Mechanism Of the Phase-reversal-basedmentioning

confidence: 99%

Theoretical and Simulation Studies on Designing a Phase-Reversal-Based Broadband CMUT With Flat Passband and Improved Noise Rejections for SHM

Zhang

Wang

et al. 2022

IEEE Sensors J.

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In the past two decades, capacitive micromachined ultrasonic transducers (CMUTs) have been greatly explored for applications in structural health monitoring (SHM); however, relevant theories about their broadband sense have not been investigated systematically. Therefore, broadband CMUTs have been specifically developed from the aspects of theory and simulation in this work. Based on these theoretical developments, we propose a new design of phase-reversal-based CMUT, which has a flat passband for broadband sensing and two stopbands at both sides for improved noise rejections. First, the expressions for the evaluation of the total output current and the sensitivity of a CMUT constituted of multiple cells are deduced from the theoretical spring-mass-damping model. Then, theoretical and simulation analysis on a CMUT combined with two different cells have revealed that reversing the current phase of one of these two cells can produce significant stopbands for rejecting the low-and high-frequency noises, which are useful not only for a CMUT in coarse vacuum (low pressure) but also a CMUT in the air (atmospheric pressure). Especially, for a CMUT in a coarse vacuum, this design can effectively build a passband among the resonant frequencies of each cell instead of compensating each other to zero. Finally, the genetic algorithm is adopted to design a broadband CMUT with a given passband in air, the results of which are verified by the frequency-and time-domain simulations concurrently. Our research work may produce a theoretical way for the design of broadband CMUTs with noise rejections.

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“…where a reflects the effect of the bias voltage on the resonant frequency of the CMUT, namely the spring softening effect, which is a function of the bias voltage, indicating that the resonant frequency of the CMUT shifts as the bias voltage increases. As the top electrode moves closer to the bottom electrode due to the presence of the bias voltage, the electrical field increases and the top electrode displaces further, acting as if the spring constant of the top electrode decreases under the influence of the applied voltage [30]. The parameter b represents the frequency shift caused by pressure change at a given DC bias voltage.…”

Section: Basic Theory Of Cmut For Micro-pressure Detectionmentioning

confidence: 99%

Research on Novel CMUTs for Detecting Micro-Pressure with Ultra-High Sensitivity and Linearity

et al. 2021

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Capacitive micromachined ultrasonic transducers (CMUTs) have been indispensable owing to their resonance characteristics in the MHz frequency range. However, the inferior pressure sensitivity and linearity of traditional CMUTs themselves cannot meet the actual demands of micro-pressure measurements. In this paper, two novel CMUTs are proposed for the first time to improve the measuring performance of micro-pressure in the range of 0–10 kPa. The core concept of the enhancement is strengthening membrane deformability by partly adjusting the CMUT framework under the combined action of electrostatic force and uniform pressure. Two modified structures of an inverted frustum cone-like cavity and slotted membrane are presented, respectively, and a finite element model (FEM) of CMUT was constructed and analyzed using COMSOL Multiphysics 5.5. The results demonstrate that the maximum displacement and pressure sensitivity are improved by 16.01% and 30.79% for the frustum cone-like cavity and 104.22% and 1861.31% for the slotted membrane, respectively. Furthermore, the results show that the width uniformity of the grooves does not influence the characteristics of the membrane, which mainly depend on the total width of the grooves, greatly enriching design flexibility. In brief, the proposed structural designs can significantly improve the micro-pressure measurement performance of the CMUT, which will accelerate the rapid breakthrough of technical barriers in the fields of aerospace, industry control, and other sensing domains.

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Analysis of spring softening effect on the collapse voltage of capacitive MEMS ultrasonic transducers

Cited by 16 publications

References 23 publications

Squeeze Film Effect in Surface Micromachined Nano Ultrasonic Sensor for Different Diaphragm Displacement Profiles

Squeeze Film Effect in Surface Micromachined Nano Ultrasonic Sensor for Different Diaphragm Displacement Profiles

Theoretical and Simulation Studies on Designing a Phase-Reversal-Based Broadband CMUT With Flat Passband and Improved Noise Rejections for SHM

Research on Novel CMUTs for Detecting Micro-Pressure with Ultra-High Sensitivity and Linearity

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