Thin Diaphragm Research Articles

Bossed diaphragm coupled fixed guided beam structure for MEMS based piezoresistive pressure sensor

PurposeStructures play a very important role in developing pressure sensors with good sensitivity and linearity, as they undergo deformation to the input pressure and function as the primary sensing element of the sensor. To achieve high sensitivity, thinner diaphragms are required; however, excessively thin diaphragms may induce large deflection and instability, leading to the unfavorable performances of a sensor in terms of linearity and repeatability. Thereby, importance is given to the development of innovative structures that offer good linearity and sensitivity. This paper aims to investigate the sensitivity of a bossed diaphragm coupled fixed guided beam three-dimensional (3D) structure for pressure sensor applications.Design/methodology/approachThe proposed sensor comprises of mainly two sensing elements: the first being the 3D mechanical structure made of bulk silicon consisting of boss square diaphragm along with a fixed guided beam landing on to its center, forming the primary sensing element, and the diffused piezoresistors, which form the secondary sensing element, are embedded in the tensile and compression regions of the fixed guided beam. This micro mechanical 3 D structure is packaged for applying input pressure to the bottom of boss diaphragm. The sensor without pressure load has no deflection of the diaphragm; hence, no strain is observed on the fixed guided beam and also there is no change in the output voltage. When an input pressure P is applied through the pressure port, there is a deformation in the diaphragm causing a deflection, which displaces the mass and the fixed guided beam vertically, causing strain on the fixed guided beam, with tensile strain toward the guided end and compressive strain toward the fixed end of the close magnitudes. The geometrical dimensions of the structure, such as the diaphragm, boss and fixed guided beam, are optimized for linearity and maximum strain for an applied input pressure range of 0 to 10 bar. The structure is also analyzed analytically, numerically and experimentally, and the results are compared.FindingsThe structure offers equal magnitudes of tensile and compressive stresses on the surface of the fixed guided beam. It also offers good linearity and sensitivity. The analytical, simulation and experimental studies of this sensor are introduced and the results correlate with each other. Customized process steps are followed wherein two silicon-on-insulator (SOI) wafers are fusion bonded together, with SOI-1 wafer used to realize the diaphragm along with the boss and SOI-2 wafer to realize the fixed guided beam, leading to formation of a 3D structure. The geometrical dimensions of the structure, such as the diaphragm, boss and fixed guided beam, are optimized for linearity and maximum strain for an applied input pressure range of 0 to10 bar.Originality/valueThis paper presents a unique and compact 3D micro-mechanical structure pressure sensor with a rigid center square diaphragm (boss diaphragm) and a fixed guided beam landing at its center, with diffused piezoresistors embedded in the tensile and compression regions of the fixed guided beam. A total of six masks were involved to realize and fabricate the 3D structure and the sensor, which is presumed to be the first of its kind in the fabrication of MEMS-based piezoresistive pressure sensor.

Piezoelectric P(VDF-TrFE) micro cantilevers and beams for low frequency vibration sensors and energy harvesters

Piezoelectric P(VDF-TrFE) micro-cantilevers and beams have been developed with a novel micro-electromechanical systems process very useful for low frequency vibration sensors and energy harvesters. The devices were designed and simulated using COMSOL Multiphysics simulation software to determine the resonant frequency, voltage and power output for various dimensions with length in the range 200 μm to 2000 μm, width in the range 100 μm to 400 μm and thickness 2.5 μm in all cases. Devices were fabricated on <110> silicon wafers using a novel bulk micromachining process by suspending them using critical process steps which include: micromachining of silicon substrate from the backside using anisotropic wet etchant TMAH to define the device suspension regions with thin SiO2 diaphragm, and release of micro-cantilevers and beams by etching the SiO2 diaphragm from backside with CHF3/O2 based plasma etching. All the devices were fabricated with 2.5 μm P(VDF-TrFE) spin coated on SiO2. Laser Doppler Vibrometer was used to measure resonant frequency, voltage and power output of the devices which were operated in longitudinal mode with thermally evaporated Cr-Au interdigitated electrodes for power extraction. The experimental results obtained on fabricated devices for the first time using this process were in good agreement with those derived from simulation.

Fatigue cracking investigation on diaphragm cutout in a self-anchored suspension bridge with orthotropic steel deck

To investigate the mechanism of base-metal cracking on diaphragm cutout in a self-anchored suspension bridge with orthotropic steel deck (OSD), multi-scale finite element models were established to obtain stress response at cutout detail under the passage of wheel loads. Fatigue life was evaluated based on nominal stress method and hot-spot stress method. The results indicated that the length of the longitudinal influence line for detail stress to wheel loads approximately equalled to twice the diaphragm spacing. The wheel loading location of maximum stress was the front wheel of middle-axle group 0.3 m from the diaphragm, and the stress was dominated by in-plane stress. The nominal stress was hard to define at cutout detail for high stress concentration, and the hot-spot stress was preferred to fatigue assessment based on S-N curve of FAT125, also nominal stress should be extracted at the location 5.0 mm from cutout edge. Cutout shape of Highway Bridge in Eurocode was suggested, and diaphragm thickness should not be below 12 mm. The cutout cracking was caused by poor cutout shape, thin diaphragm, high truck traffic volume and overloaded wheel loads, while undesirable fabrication control and large residual stress might also contribute to the cracking.

S-shaped microfiber based diaphragm supported optical microphone

We propose and demonstrate a simple and highly sensitive optical microphone based on S-shaped tapered fibre (STF). The short pigtailed end of the STF is attached to the centre of a thin circular nitrile diaphragm. The applied acoustic signal deforms the nitrile diaphragm and due to the affixation, the STF structure gets modified leading to change in the bending angles of the two STF bends. As a consequence, the photodetector output, detecting the reflected light intensity of the STF, varies in accordance with the applied acoustic signal. Various properties of the proposed sensing setup can be easily tailored by changing the diaphragm diameter and thickness, and the shapes and size of the STF. For an optimized configuration, the proposed sensor achieves a sensitivity of 3.07 mV Pa−1 and a minimum detectable pressure of 36.48 mPa Hz−1. The sensor shows a linear behaviour up to 1300 Hz and the experimental value of its first order natural frequency is 1455 Hz.

Probing heavy ion radiation effects in silicon carbide (SiC) via 3D integrated multimode vibrating diaphragms

We report on the measurement and analysis of energetic heavy ion radiation effects on the mechanical properties of silicon carbide (SiC) crystals, by exploiting a vertical stack of micromachined vibrating SiC thin diaphragms integrated in a three-dimensional (3D) fashion. The diaphragms are 1 mm × 1 mm in lateral dimensions and 2 μm in thickness, vibrating at their multiple flexural modes in the range of 200 to 800 kHz. Upon 10.25 MeV oxygen ion irradiation, the 4 devices in the 3D stack exhibit saliently different changes in their multimode resonance frequencies. The device that is intended to capture most ions shows the largest frequency downshifts (∼6.6%–11.3%), corresponding to the extracted tension release from 382 MPa to 306 MPa, which can be explained by the maximum displacement damage in this device. The design of 3D integration not only scientifically enables probing different radiation effects in multiple devices simultaneously with clear controls but also economically evades very expensive, repetitive tests on individual devices, thus proving to be a powerful platform for analyzing and understanding radiation damage in micro/nanoelectromechanical systems and other micro/nanosystems.

Peculiarities of the flows forming in processes of an impulse starting of a supersonic wind tunnel with different diffusers

The peculiarities of supersonic unsteady flows forming in the processes of an impulse starting of a wind tunnel including a fore-chamber, a nozzle, a diffuser, and an exhaust tank are considered. The fore-chamber is separated from the flow duct by a thin breakable diaphragm. Before the wind tunnel starting, the gas contained in the exhaust tank is pumped out down to a very small pressure, and then the high-pressured working gas is fed into the fore-chamber. Upon reaching some value of this pressure, the diaphragm “instantaneously” ruptures, and the working gas starts exhausting through the nozzle: a rapid unsteady process of the wind tunnel starting arises. The numerical simulation of the flows forming at the impulse starting of the simplest experimental gas-dynamic facility has been carried out; the facility is arranged with a nozzle forming at its exit a two-dimensional supersonic flow with the Mach number of 2.9, and with replaceable diffusers having different relative areas of the throat. The numerical computations of two-dimensional unsteady flows have been carried out using the Reynolds-averaged Navier—Stokes equations and the SST k-ω turbulence model. The flow patterns computed numerically are compared with the data of the optical visualization of the flow obtained in the experimental gas-dynamic facility in the process of its starting.

Most animals hear acoustic flow instead of pressure; we should too

The majority of animals that hear sound do so by detecting the minute fluctuations in the velocity of the medium. They do this by sensing the deflection of thin hairs that are driven by viscous forces in the acoustic medium. This is in contrast to the detection of sound pressure, as is used in some animals, including humans. Nearly all microphones respond to sound through the use of a thin diaphragm or membrane designed to experience a net fluctuating pressure in a sound field. Here, we explore technologies for achieving precise detection of sound using a mechanical structure that is driven by viscous forces associated with the fluctuating velocity of the medium. In one example, this has been shown to result in a directional microphone with flat response from 1 Hz to 50 kHz [Zhou et al., “Sensing fluctuating airflow with spider silk,” Proc. Natl. Acad. Sci., 201710559(2017)]. Methods of creating extremely compliant, viscous-driven velocity sensors are discussed along with a new technique for capacitive transduction to achieve an electronic output.

Fabrication of on‐chip vacuum pump using a silicon nanostructure by metal‐assisted chemical etching

We proposed, fabricated, and evaluated an on‐chip vacuum pumping device using a nanoporous structure fabricated using metal‐assisted chemical etching (MACE) on silicon (Si). The driving principle relies on thermal transpiration, which is generally referred to as a Knudsen pump. MACE can be used to fabricate high‐aspect nanostructures of Si, which is advantageous for obtaining a high performance similar to that of a Knudsen pump because the nanochannels and temperature difference are significant components of this principle. The pumping device consists of wafers arranged as follows: glass (300 µm)/Si (200 µm)/glass (200 µm). The glass wafers have small chambers, and the Si wafer has a nanoporous structure with wide channels. One hundred and thirty‐two stages (pairs of cool and hot chambers) are cascaded. Vacuum levels are evaluated using a suspended thin diaphragm of Si. The device is fabricated using conventional microfabrication techniques. In the fabricated device, the temperature of the cool and hot sides is maintained at 70 and 230 °C. The chamber pressure in the 132nd stage was estimated to be 85.9 kPa, and the evacuation speed was approximately 10 min. © 2019 Institute of Electrical Engineers of Japan. Published by John Wiley &amp; Sons, Inc.

Design optimization and simulation of a diamond based piezoresistive pressure sensor for high temperature application

Abstract To investigate the performance of diamond based piezoresistive pressure sensors, we have carried out a simulation study for obtaining an estimate of the pressure response. The sensor comprised of a thin diaphragm of diamond as a primary sensing element and boron doped diamond piezoresistors as transduction elements. The diaphragm geometry was optimized to 750 μm × 750 μm with 35 μm diaphragm thickness for a pressure range up to 40 MPa. Subsequently, the placement of diamond piezoresistors on the top of the thin diaphragm was optimized to get the best sensitivity. Since diamond has a higher piezoresistive coefficient in the longitudinal direction, a configuration of two longitudinal piezoresistors near to diaphragm edge and the other two transverse piezoresistors near to the diaphragm centre was used for the placement of piezoresistors. The voltage response of the piezoresistive pressure sensor was estimated using simulations. A sensitivity of 0.27 mV/V/MPa was obtained for the optimized sensor parameters.

Complex geometry apertures for resonant diaphragms in rectangular waveguides

ABSTRACTIn the paper, we investigate thin metal transverse resonant diaphragms with a complex aperture in rectangular waveguides and develop some new aperture profiles with advanced properties. The presented resonant diaphragms are produced by the metallization of the thin dielectric substrate and allow to construct band-pass and band-stop filters with high Q-factor and transmission zeros. An original approach to develop the ultra-compact and robust waveguide filters is described. As an example, we demonstrate the band-pass filter on WR-90 rectangular waveguides with the length of 8 mm and the pass-band of 10%.

Deposition and process development of AlN for MEMS acoustic sensor

This paper describes a technique for fabrication of AlN based structure for MEMS acoustic sensor and similar applications. The AlN films of 2.1 μm thickness are grown on silicon substrates by reactive sputtering. The deposited films are characterized to determine the crystalline quality and piezoelectricity. Thermal annealing of the deposited films are performed at different temperatures for better piezoelectricity. The investigation showed a c-axis oriented AlN film is obtained at 600 °C temperature. A simple AlN based structure for MEMS acoustic sensor is fabricated on a thin silicon diaphragm. During fabrication of structure, a wet etching technique of AlN was developed. The reliability testing of fabricated structured was performed. The maximum current that can be passed across Al-deposited AlN edge was found to be 3.05 A without any damage. The investigations show a uniform Al step coverage on a 2.1 μm-thick AlN edge using proposed technique. The proposed technique for AlN etching reduces the process complexity and providing better reliability of fabricated structure. The resonance frequency of fabricated AlN based structure was measured and found to be 42.9 kHz.

Analytical Modelling and FEM Simulation of Capacitive Pressure Sensor for Intraocular Pressure Sensing

The paper presents analytical modelling and Finite Element Method (FEM) based simulation of clamped circular capacitive pressure sensors for Intraocular Pressure (IOP) measurement. The parallel plate capacitive pressure sensor consists of a fixed backplate and a circular shaped clamped thin diaphragm made of silicon material. The plates are separated by a vacuum media. MATLAB® and COVENTORWARE® are used for analytical and FEM simulations, respectively, and a comparison of maximum deflection in the diaphragm, capacitance after pressure application and sensitivity is carried out. A pressure range of 0-60 mmHg is used for IOP measurement.

Harnessing the bilinear nonlinearity of a 3D printed biomimetic diaphragm for acoustic sensor applications

Abstract This study presents an initial assessment of a newly shaped biomimetic diaphragm aimed at mimicking the function of the tympanic membrane (TM) of the human auditory system. The TM consists of three parts, namely, the malleus, pars tensa, and pars flaccida, and its dynamic behavior is typically known to be different from other common, thin membranes. The constructed membrane has a curved conical shape with the apex pointing medially, and with an initially bucked shape. The malleus is also firmly attached to the medial surface of the membrane at its center. In addition, the TM is connected to a surrounding annulus ligament (muscle) and is concave at its deepest part (the umbo). As a result, the TM does not move as a normal flat and thin diaphragm. In this study, we investigated the bilinear nonlinearity of an elliptic and conical shaped diaphragm similar to the actual TM of the human auditory system to deliver improved vibrating characteristics. It is reported that the proposed adaptively diaphragm structure fabricated by using 3D printing technology can exhibit bilinear nonlinearity when the sound pressure level (SPL) of the incoming sound is high, thus resulting in a flat sensitivity and a broad frequency response.

Nonlinear Theory of Sandwich Shells with a Transversely Soft Core Containing Delamination Zones and Edge Support Diaphragm

Sandwich shells with transversely soft cores and skin layers supported along the edges by a thin deformable diaphragm with a ruled middle surface are considered. Delamination zones are assumed on the contact surfaces between the core and skin layers. The refined geometrically nonlinear theory has been constructed for these type of structures at small deformations and moderate displacements, which can describe prebuckling deformation and reveal all possible buckling mode shapes of skin layers (antisymmetric, symmetric, mixed bending and mixed bending-shear, as well as arbitrary mode shapes comprising all listed modes) and of the reinforcing diaphragm. This theory is based on the introduction of interaction forces between the core and skin layers and between the core and reinforcing diaphragm at each point of the contact surfaces as unknowns. The previously proposed variant of the generalized Lagrangian variational principle has been utilized in the derivation of the governing equations, static boundary conditions for the shell and reinforcing diaphragm, and kinematic coupling conditions between the core and skin and between the core and support diaphragm.

청각기관 고막을 생체 모방한 다이어프램의 쌍선형 강성 특성

This study presents the preliminary study for a new shaped diaphragm structure aimed at mimicking the function of the tympanic membrane (TM) of human auditory systems. The TM consists of three parts: malleus, pars tensa, and pars flaccida, and the dynamic behavior of the TM is typically known to be different from other common thin membranes. In other words, the shape of human TM is elliptic and conical, and the TM does not move as a normal flat and thin diaphragm. We investigated the bilinear nonlinear stiffness of elliptic and conical shaped diaphragm similar to actual TM of human auditory system to deliver improved vibrating characteristics. The diaphragm structure made by 3-D printing technology can exhibits the bilinear nonlinearity when the sound pressure level (SPL) of incoming sound is high, resulting in the flat and broad frequency response.

Diabetes Can Accelerate Sarcopenia in the Diaphragm

The diaphragm is a skeletal muscle that is involved not only in respiration but also in swallowing and lymphatic functions and maintaining posture. Only a few studies have described diaphragm thickness in patients with diabetes. Diaphragm thickness is usually evaluated using ultrasonography (U.S.). However, because evaluation of diaphragm thickness using U.S. is not routinely performed, it is difficult to assess it in a retrospective manner. Therefore, in this study, we developed a new method to evaluate diaphragm thickness in patients with diabetes using computed tomography (CT) and evaluated the correlation between U.S. and CT findings. Then, we evaluated the relationship among diaphragm thickness, age, and blood glucose metabolism. We prospectively evaluated the diaphragm thickness of 50 patients with diabetes using both U.S. and CT. The diaphragm thickness using CT was evaluated in the zone of apposition on contact with the thoracic cavity between the most frontal and dorsal positions, and the results were expressed as a sum of left and right measurements. The mean diaphragm thickness was 3.35 ± 0.64 mm and 3.73 ± 1.00 mm using U.S. and CT, respectively. The diaphragm thicknesses evaluated using both U.S. and CT were significantly correlated with each other (r = 0.3809, P = 0.0063). Then, we studied the data of 1patients with tuberculosis who had undergone CT and had a high morbidity of diabetes. The diaphragm thickness was positively correlated with body weight (r = 0.2911, P = 0.0088) and negatively with age and HbA1c (r = −0.4493, P &amp;lt; 0.0001; r = −0.5507, P &amp;lt; 0.0001, respectively). Moreover, the diaphragm thickness was significantly less in patients with diabetes than in those without diabetes. A thin diaphragm has been found to be related to poor prognosis among patients with acute pneumonia in intensive care units. Our results indicate that diabetes can accelerate sarcopenia of the diaphragm. Because the diaphragm has multiple functions, sarcopenia of the diaphragm in patients with diabetes might affect prognosis. Disclosure M. Yamamoto: None. M. Takemoto: None. H. Masuyama: None. M. Koshizaka: None. Y. Maezawa: None. K. Yokote: Research Support; Self; Astellas Pharm Ltd, MSD K.K..

Fiber optic method for obtaining the peak reflected pressure of shock waves.

Most of fiber-optic pressure sensors used in shock wave measurements are based on deformations of sensing elements. These approaches result in low dynamic pressure ranges for these sensors used in the air. A novel fiber-optic method based on the relationship between pressure and the acceleration of a diaphragm is proposed to obtain peak reflected pressure of shock waves in the air. The optical sensor is designed with a thin circular diaphragm as the sensing element, and the Fabry-Perot optical interferometry is used to detect the acceleration of the diaphragm. Shock tube and explosive-blast experiments prove that the proposed fiber optic method is feasible and has the advantages of no calibration, high precision and fast response time. The proposed fiber-optic pressure method has potential in practical applications for shock wave measurements.

Design of SAW sensor for longitudinal strain measurement with improved sensitivity

This paper presents the design of a highly sensitive surface acoustic wave (SAW)-based sensor with novel structure for the longitudinal strain measurement. The sensor utilizes thin lithium niobate (LiNbO3) diaphragm as the sensing element rather than the bulk substrate. The application of the diaphragm effectively decreases the cross-sectional area of the strain sensitive element, and meanwhile reduces the resistance between the sensor and the specimen. The newly designed strain sensor is to operate around a frequency of 50 MHz. The insertion loss of − 12 dB and quality factor of 63 are obtained analytically from impulse-response model. The sensor performance with tensile testing of the steel beam is predicted by the finite element method. The prestressed eigenfrequency analysis is conducted with the COMSOL commercial software. The simulation shows the resonance frequency of the sensor shifts linearly with the strain induced in the testing beam. For the SAW sensor with traditional configuration applying 1 mm thick substrate, the strain sensitivity is obtained as 0.41 ppm/μe. For the sensor with the novel design employing thin diaphragm with the thickness of 200 μm, the strain sensitivity is increased to 0.83 ppm/μe. With the availability of the bulk micromachining of LiNbO3, the application of the piezoelectric diaphragm as sensing element in SAW strain sensor can be an alternative way to enhance the sensor sensitivity.

Design, development and characterization of MEMS silicon diaphragm force sensor

The aim of the paper is to describe the design, development and experimental characterization of a MEMS silicon diaphragm based force sensor. In the presented design, a unique combination of a thin single crystal silicon diaphragm has been used as a mechanical sensing element. The force sensor is based on the principle of conversion of applied force to an electrical quantity (e.g. voltage) consists of four piezoresistors in a Wheatstone-bridge configuration. The sensor has been modeled with the help of modern CAD tools and, after several iterations, the diaphragm size and thickness have been optimized to obtain a high sensitivity against an applied load in the designed range. The finite element analysis (FEA) has been carried out for computational investigations to have an approximate evaluation in regard of mechanical design and features. The important parameters like stress, strain and deflection are found to be within permissible limits. The fabricated sensor has been characterized by its metrological capabilities. The relative error due to repeatability is found to be <1% in the working range of the sensor. The sensitivity has been found to be in order of 0.35–0.40 mV/V/N for 10 N–50 N force range.

Generalized Mathematical Model of Thin Asymmetric Inductive Diaphragm in Rectangular Waveguide

Introduction. A significant number of microwave devices are constructed with applying the investigation results of thin asymmetric inductive diaphragm in rectangular waveguide. Increasing the requirements for the characteristics of these devices stipulates necessity to review the possibilities of existing electromagnetic methods in relation to increasing the accuracy of generalized scattering matrices calculation of this diaphragm. To obtain the high accuracy results of generalized scattering matrices calculation, a further study of integral equations method is represent considerable practical interest. Mathematical model of diaphragm. An accurate novel solution for general scattering matrix of infinitely thin asymmetric one-sided diaphragm in rectangular waveguide has been obtained. The problem is formed as the system of integral equations along the number of waves which is incident on the diaphragm. By applying the Galerkin’s method, each integral equation is reduced to system of linear algebraic equations relatively to coefficients of tangential electric field decomposition in diaphragm window by series of coordinate functions. The joint solution of all equations gives the distribution of tangential electric field in diaphragm window which is further used for finding the generalized scattering matrix. Numerical results. Two approaches for finding the coupling coefficients of coordinate functions of diaphragm window and eigen functions of waveguide are investigated. An estimation of limiting possibilities of developed realization of the integral equations method at approximation of tangential electric field in diaphragm window by series of eigen scalar functions has been carried out. It is shown that the calculated results of module and phase of fundamental wave transmission coefficient through diaphragm slowly go to exact values when the order of linear algebraic equation system is increased. Conclusions. The results of diaphragm investigation by using this algorithm have not only independent value but can be used to verify the accuracy of calculating the electromagnetic parameters of thin waveguide structures by using the general methods for solving electromagnetic problems, for example, FDTD. It is supposed that the results obtained in this work can be used in developing fast and high-precision calculation algorithms for frequency responses of multi-stage asymmetric waveguide structures.