Flat Diaphragm Research Articles

Design of High Sensitivity and Linearity Microelectromechanical Systems Capacitive Tire Pressure Sensor using Stepped Membrane

This paper is focused on a novel design of stepped diaphragm for MEMS capacitive pressure sensor used in tire pressure monitoring system. The structure of sensor diaphragm plays a key role for determining the sensitivity of the sensor and the non-linearity of the output.First the structures of two capacitive pressure sensors with clamped square flatdiaphragms, with different thicknesses are investigatedand their sensitivity and non-linearityare compared together.Finally for increasing the sensitivity and linearity,anew capacitive pressure sensor with a stepped diaphragm is introduced. A numerical solution for determination of theaccurate sensitivity of the sensor is presented.The results show that the sensitivity of the sensor is increased from 0.063 fF/KPa with flat diaphragm to 0.107 fF/KPa with stepped diaphragm and also the non-linearity is decreased from 2.37% to 1.857%. In this design, the sensor sensitivity and output linearity are increased simultaneously.

Modeling and analysis of a novel combined peninsula–island structure diaphragm for ultra-low pressure sensing with high sensitivity

A novel combined peninsula–island structure diaphragm has been developed with four pairs of peninsula and island structures as well as four gaps between them. When a pressure is applied to the diaphragm, the major strain energy of the diaphragm is locked in the position above each gap, which is called the stress concentration region (SCR). Also, minimal strain energy is wasted outside the SCR. Therefore, this novel diaphragm is favorable in obtaining high sensitivity for a micro-electromechanical system piezoresistive ultra-low pressure sensor. In order to optimize the diaphragm structure, the partial differential equation governing the diaphragm deflection has been given under pressure. The theoretical analysis solutions are obtained based on the theory of the Navier trigonometric series and the mirror image method, and in accordance with the finite element method simulation results. Finally, a sensor with the proposed diaphragm is designed with the working range of 0–500 Pa and has sensitivity above 0.055 mV V−1 Pa−1. In comparison to a flat diaphragm with the same dimensions, this novel diaphragm achieves a sensitivity level increased by 256%, a nonlinearity reduced by 79%, and a resonance frequency increased by 5.5%. In addition, the proposed theoretical analysis solution of the diaphragm can also be applied to other kinds of diaphragm with different islands to achieve optimization.

Vibration Modes of Piezoelectric Diaphragms for Ultrasonic Microsensors and Influence of Top Electrodes

Vibration modes of MEMS piezoelectric diaphragms responding to an ultrasound pulse were investigated and influence of top electrodes to the vibration modes was discussed. The top electrode has a centrosymmetric shape divided into inner part for ultrasonic sensing and outer part for resonant frequency tuning. Piezoelectric output signal is generated in the inner electrode by centrosymmetric vibrations. The piezoelectric diaphragms were fabricated in flat or buckled shape and the top electrodes of various thickness were formed on them. Pulse-induced vibration modes were evaluated by using scanning laser Doppler vibrometry. The buckled diaphragms showed resonant peaks in a narrower frequency range compared to the flat diaphragm. The top electrode showed an influence on the vibration modes so that vibrations with a large amplitude spontaneously concentrated in the sensing electrode area, even in the case of a thin electrode film around 10nm.

New Vision Sensor to Measure Gas Pressure

Abstract The paper presents the construction and operation of a video sensor developed for video-manometer. In the publication the use of video-manometer for measuring gas pressure is presented. A characteristic feature of the device is pressure measurement based on diaphragm deformation and digital image processing. Presented measuring technique eliminates restrictions in the construction of the measuring apparatus arising from non-linear nature of diaphragm deformation. It also allows performing measurements of gas pressure, also of explosive gas, providing galvanic isolation between the factor measured and the measuring device. The paper presents the results of video-manometer calibration and measurements taken during the laboratory tests. It has been shown that the developed video-manometer, that is equipped with a flat silicone diaphragm, allows measuring the gas pressure in the range of 0 – 100 mbar with an error less than 2 %. In the experiments the CO2 pressure was measured.

Annularly Grooved Diaphragm Pressure Sensor With Embedded Silicon Nanowires for Low Pressure Application

We present a nanoelectromechanical system piezoresistive pressure sensor with annular grooves on the circular diaphragm where silicon nanowires (SiNWs) are embedded as sensing elements around the edge. In comparison with our previous flat diaphragm pressure sensor, this new diaphragm structure enhances the device sensitivity by 2.5 times under pressure range of 0-120 mmHg. By leveraging SiNWs as piezoresistors, this improvement is even remarkable in contrast to other recently reported piezoresistive pressure sensing devices. In addition, with the miniaturized sensing diaphragm (radius of 100 μm) the sensor can be potentially used as implantable device for low-pressure sensing applications.

Configuration improvement for micropressure sensor with vibration interference

Presented is the configuration design for piezoresistive absolute micropressure sensors. A figure of merit called the performance factor (PF) is defined as a quantitative index to describe the comprehensive performances of a sensor including sensitivity, resonant frequency and acceleration interference. Two configurations are proposed through introducing islands and sensitive beams into the typical flat diaphragm. The stress distributions of sensitive elements are analysed by a finite element method. Multivariate fittings based on ANSYS simulation results are performed to establish the equations on surface stresses and deflections of the two sensors. Optimisation by MATLAB is carried out to determine the dimensions of the configurations. Convex corner undercutting is analysed to estimate the final dimensions of the islands. Each PF of the two configurations with the determined dimensions has been calculated and compared. Silicon bulk micromachining is utilised to fabricate the prototypes of the sensors. The outputs of the sensors under both static and dynamic conditions are tested. Experimental results reveal that the configuration with quad islands presents the highest PF of 210.947 Hz1/4. The favourable overall performances make the sensor more suitable for altimetry.

An analytical solution for curved piezoelectric micromachined ultrasonic transducers with spherically shaped diaphragms.

An analytical solution for piezoelectrically actuated spherically shaped diaphragms has been developed to study their dynamic behavior with targeted applications in piezoelectric micromachined ultrasonic transducers (pMUT). The analytical model starts with a curved pMUT composed of a piezoelectric diaphragm with a nominal radius in size, a radius of curvature in shape, and under both possible actuation sources of radial pressure and electric potential. The diaphragm has the piezoelectric material polarized in the direction perpendicular to its surface and sandwiched between two metal electrodes. When an electric field is applied between the two electrodes, the in-plane piezoelectric strain can cause larger out-of-plane deflections than a flat unimorph piezoelectric diaphragm because of the diaphragm's spherical curvature with a clamped periphery for high electromechanical coupling factor. Key performance parameters, including mechanical mode shapes, resonant frequencies, dynamic responses, and displacements, with respect to the curvature and size of the diaphragm have been investigated. Both analytical derivations and numerical simulations using finite element analysis have been performed for the optimal design of the electromechanical coupling factor, with varying factors such as mechanical resonant frequency, radius of curvature, nominal radius, and thickness. As such, this work provides theoretical foundations for the design of curved pMUTs with high electromechanical coupling factor compared with planar-shape pMUTs.

Geometry optimization for micro-pressure sensor considering dynamic interference.

Presented is the geometry optimization for piezoresistive absolute micro-pressure sensor. A figure of merit called the performance factor (PF) is defined as a quantitative index to describe the comprehensive performances of a sensor including sensitivity, resonant frequency, and acceleration interference. Three geometries are proposed through introducing islands and sensitive beams into typical flat diaphragm. The stress distributions of sensitive elements are analyzed by finite element method. Multivariate fittings based on ANSYS simulation results are performed to establish the equations about surface stress, deflection, and resonant frequency. Optimization by MATLAB is carried out to determine the dimensions of the geometries. Convex corner undercutting is evaluated. Each PF of the three geometries with the determined dimensions is calculated and compared. Silicon bulk micromachining is utilized to fabricate the prototypes of the sensors. The outputs of the sensors under both static and dynamic conditions are tested. Experimental results demonstrate the rationality of the defined performance factor and reveal that the geometry with quad islands presents the highest PF of 210.947 Hz(1/4). The favorable overall performances enable the sensor more suitable for altimetry.

Realization of a micro pressure sensor with high sensitivity and overload by introducing beams and Islands

Presented is a piezoresistive absolute micro pressure sensor for altimetry. This investigation involves the design, fabrication and testing of the sensor. By analyzing the stress distribution of sensitive elements using finite element method (FEM), an improved structure is built up through introducing multi islands and sensitive beams into traditional flat diaphragm. The proposed configuration presents its advantages in terms of enhanced sensitivity and overload resistance compared with the bossed diaphragm and flat diaphragm structures. Multivariate fittings based on ANSYS® simulation results are performed to establish equations about surface stress and deflection of the sensor. Optimization by MATLAB® is carried out to determine the structure dimensions. Silicon bulk micromachining technology is utilized to fabricate the sensor prototype, and the fabrication process is discussed. The output signals under both static and dynamic conditions are evaluated and tested. Experimental results demonstrate the sensor features a relatively high sensitivity of 17.795 μV/V/Pa in the operating range of 500 Pa at room temperature and a proper overload resistance of 200 times overpressure to promise its survival under atmosphere. The favorable performances enable the sensor's application in measuring absolute micro pressure.

Design optimization of a high-sensitive absolute micro-pressure sensor

Purpose – The purpose of this study is to develop a piezoresistive absolute micro-pressure sensor for altimetry. For this application, both high sensitivity and high overload resistance are required. To develop a piezoresistive absolute micro-pressure sensor for altimetry, both high sensitivity and high-overload resistance are required. The structure design and optimization are critical for achieving the purpose. Besides, the study of dynamic performances is important for providing a solution to improve the accuracy under vibration environments. Design/methodology/approach – An improved structure is studied through incorporating sensitive beams into the twin-island-diaphragm structure. Equations about surface stress and deflection of the sensor are established by multivariate fittings based on the ANSYS simulation results. Structure dimensions are determined by MATLAB optimization. The silicon bulk micromachining technology is utilized to fabricate the sensor prototype. The performances under both static and dynamic conditions are tested. Findings – Compared with flat diaphragm and twin-island-diaphragm structures, the sensor features a relatively high sensitivity with the capacity of suffering atmosphere due to the introduction of sensitive beams and the optimization method used. Originality/value – An improved sensor prototype is raised and optimized for achieving the high sensitivity and the capacity of suffering atmosphere simultaneously. A general optimization method is proposed based on the multivariate fitting results. To simplify the calculation, a method to linearize the nonlinear fitting and optimization problems is presented. Moreover, a differential readout scheme attempting to decrease the dynamic interference is designed.

A high sensitivity and high linearity pressure sensor based on a peninsula-structured diaphragm for low-pressure ranges

The trade-off between sensitivity and linearity has been the major problem in designing the piezoresistive pressure sensors for low pressure ranges. To resolve the problem, a novel peninsula-structured diaphragm with specially designed piezoresistors was proposed. Finite element method (FEM) was adopted for analyzing the sensor performance as well as comparisons with other sensor structures. In comparison to flat diaphragm, the proposed sensor design could achieve a sensitivity increase by 11.4%, nonlinearity reduction of 60% and resonance frequency increase of 41.8%. In addition, the modified peninsula-structured diaphragms featuring a center boss have been optimized to achieve ultra-low nonlinearities of 0.018%FFS and 0.07%FFS for the 5kPa and 3kPa pressure ranges respectively with higher sensitivities as compared to the CBM (cross beam membrane) and hollow stiffening structures. In accordance with the FEM results, the fabricated pressure sensor with the peninsula-structured diaphragm showed a sensitivity of 18.4mV/V full-scale output and a nonlinearity error of 0.36%FSS in the pressure range 0–5kPa. The proposed sensor structure is potentially a better choice for designing low pressure sensors.

Experimental Investigation of the Seismic Performance of Retrofitted Masonry Flat Arch Diaphragms

AbstractMasonry flat arch diaphragm that developed in Britain is still in use in parts of Europe, North America, the Middle East, and Indian subcontinent. The damage of a large number of these diaphragms during past earthquakes all around the world highlighted the need for developing an appropriate retrofitting method. In this study, the in-plane seismic behavior of ordinary and the retrofitted brick flat arch diaphragms are experimentally investigated. Eight full-scale experiments were conducted under cyclic loading. Perpendicular and parallel loads were applied to the steel I-cross beams of the masonry flat arch diaphragms. The experimental models consisted of two frames of masonry flat arch diaphragms in the absence of brick flat arch, two ordinary masonry flat arch diaphragms with steel tension ties in end arch spans as prototype, two masonry flat arch diaphragms without and with steel tension ties in diaphragm span, and two retrofitted masonry flat arch diaphragms with simultaneous use of steel diago...

Anesthetic experience of a patient with Prune-belly syndrome.

Anesthetic experience of a patient with Prune-belly syndrome.

High Sensitive and Linear Pressure Sensor for Ultra-low Pressure Measurement

A novel peninsula-structured diaphragm with specially designed piezoresistors was proposed in our present pressure sensor for ultra-low pressure measurement. Finite element method (FEM) was adopted for analyzing the sensor performance. In comparison to typical sensors with flat and center-bossed diaphragms, the optimized sensor design could achieve excellent sensitivity and linearity. In accordance with the FEM results, the fabricated pressure sensor showed a sensitivity of 18.4 mV/V full-scale output and a nonlinearity error of 0.36%FSS in the pressure range 0-5 kPa. The proposed sensor structure is potentially a better choice for measuring low pressures.

Sensitivity Modification of Piezoelectric Diaphragm-Type Ultrasonic Microsensors by Poling and Influence of in-Plane Stress

Sensitivity modification of tunable ultrasonic microsensors has been investigated in terms of poling effect to the piezoelectric/ferroelectric thin film on the sensor diaphragm. The sensor has a tuning electrode besides a sensing electrode to tune the resonant frequency by introducing converse-piezoelectric stress on the diaphragm. Sensitivity change with poling and tuning voltage applications has been traced on sensors with flat and buckled diaphragms and the buckled-diaphragm sensors have shown anomalies; sensitivity decreases after increase with increasing poling voltage and a butterfly curve of sensitivity to tuning voltage reverses in a high poling voltage region. After the sensitivity investigation the buckling shape of the diaphragm has been profiled under the poling and tuning voltage applications, and the origin of the sensitivity anomalies have been found to be the total stress of the diaphragm and buckling shape of the sensing electrode part induced by the combination of the poling and tuning stress.

Design considerations to enhance the performances of thin circular piezoelectric energy harvester diaphragms in harsh liquid environments

Thin circular piezoelectric energy harvester diaphragms undergoing large deflection in a harsh liquid environment are investigated in this paper. A material set combining AlN as transducer, SiC as electronics, Mo as wiring and Si as holder is considered. A highly accurate analytical model, which presents less than 5% error compared to FEM simulations in COMSOL, is first developed to study thoroughly flat diaphragms. Consequently, etching the wafer and adding a corrugation are proposed to reduce both the stress concentration at the edge and the influence of residual stress on the device behavior, respectively. Both ideas are predicted to increase the power density compared to the standard flat case by at least a factor of 5 to 10.

Bending-induced electromechanical coupling and large piezoelectric response in a micromachined diaphragm

We investigated the dependence of electromechanical coupling and the piezoelectric response of a micromachined Pb(Zr0.52Ti0.48)O3 (PZT) diaphragm on its curvature by observing the impedance spectrum and central deflection responses to a small AC voltage. The curvature of the diaphragm was controlled by applying air pressure to its back. We found that a depolarized flat diaphragm does not initially exhibit electromechanical coupling or the piezoelectric response. However, upon the application of static air pressure to the diaphragm, both electromechanical coupling and the piezoelectric response can be induced in the originally depolarized diaphragm. The piezoelectric response increases as the curvature increases and a giant piezoelectric response can be obtained from a bent diaphragm. The obtained results clearly demonstrate that a high strain gradient in a diaphragm can polarize a PZT film through a flexoelectric effect, and that the induced piezoelectric response of the diaphragm can be controlled by adjusting its curvature.

Incorporation of beams into bossed diaphragm for a high sensitivity and overload micro pressure sensor

The paper presents a piezoresistive absolute micro pressure sensor, which is of great benefits for altitude location. In this investigation, the design, fabrication, and test of the sensor are involved. By analyzing the stress distribution of sensitive elements using finite element method, a novel structure through the introduction of sensitive beams into traditional bossed diaphragm is built up. The proposed configuration presents its advantages in terms of high sensitivity and high overload resistance compared with the conventional bossed diaphragm and flat diaphragm structures. Curve fittings of surface stress and deflection based on ANSYS simulation results are performed to establish the equations about the sensor. Nonlinear optimization by MATLAB is carried out to determine the structure dimensions. The output signals in both static and dynamic environments are evaluated. Silicon bulk micromachining technology is utilized to fabricate the sensor prototype, and the fabrication process is discussed. Experimental results demonstrate the sensor features a high sensitivity of 11.098 μV/V/Pa in the operating range of 500 Pa at room temperature, and a high overload resistance of 200 times overpressure to promise its survival under atmosphere. Due to the excellent performance above, the sensor can be applied in measuring the absolute micro pressure lower than 500 Pa.

A Robust and Compact Fiber Bragg Grating Vibration Sensor for Seismic Measurement

A compact fiber Bragg grating (FBG) vibration sensor consisting a flat diaphragm and two L-shaped rigid cantilever beams for seismic measurement has been proposed and experimentally demonstrated. The specially designed sensing configuration contributes many desirable features such as a wide frequency response range (10-120 Hz), an extremely high sensitivity coefficient (~100pm/g) together with a robust metal package for improving the mechanical strength and a decreased transverse sensitivity (<; 5%), making it a good candidate for in-field seismic wave measurement in oil and gas exploration.

Characterization of Silicon Nanowire Embedded in a MEMS Diaphragm Structure Within Large Compressive Strain Range

The characteristics of piezoresistive silicon nanowires (SiNWs) under compressive strain as large as 1.7% are reported. The SiNW is embedded in a multilayered diaphragm structure consisting of silicon nitride and silicon oxide. After leveraging the high fracture stress and intrinsic tensile stress of silicon nitride layer to produce a flat diaphragm, we can create large compressive strain to the SiNW without damaging the diaphragm. The relationship between SiNW resistance change and applied strain is measured and investigated with 2-μm and 5-μm SiNWs for both scientific and practical points of view. This approach demonstrates the validity to reveal the SiNW properties under large strain, and the exploration provides good reference for future SiNW-based MEMS sensor design.