Showing papers in "Sensors and Actuators A-physical in 1997"
TL;DR: In this paper, a simple model predicts exponential dependence of the output concentration on diffusion coefficient in certain regimes, and experiments confirm the model; the process is demonstrated using a micromachined device with fluid channels as small as 20 μm.
Abstract: Microfabricated fluid systems allow complex chemical analyses to be performed on sub-nanoliter volumes. However, many common laboratory procedures, including filtration, have yet to be robustly implemented in micro-fluid systems. A device has been developed to separate particles and molecules based on their diffusion coefficients; the process is demonstrated using a micromachined device with fluid channels as small as 20 μm. A simple model predicts exponential dependence of the output concentration on diffusion coefficient in certain regimes. Experiments confirm the model.
324 citations
TL;DR: In this paper, the authors demonstrate how combinations of two or more electro-thermal actuators can be applied to a variety of basic building-block micromechanical devices.
Abstract: Electro-thermal (E-T) actuators have been developed to complement the capabilities of electrostatic actuators. The thermal actuators presented here can be arrayed to generate high forces. Equally significant is that the single actuators and arrays of actuators operate at voltages and currents that are directly compatible with standard microelectronics. This paper demonstrates how combinations of two or more electro-thermal actuators can be applied to a variety of basic building-block micromechanical devices: array of ten lateral actuators; array of ten vertical actuators; vertically actuated two-axis tilting mirror; corner-cube retroreflector actuated by lateral array; grippers over the die edge with flip-over wiring; rotary stepper motor; flip-up optical grating on rotary stepper motor; linear stepper motor; and a linear stepper motor for assembly of hinged structures.
260 citations
TL;DR: In this article, a micro-sized zero-magnetostrictive amorphous wire head of about 1 mm installed in self oscillation circuits such as the Colpitts oscillator and a multivibrator circuit shows a high sensitivity with a resolution of 10 −6 Oe for ac fields and 10 −5 OE for dc fields, quick response with a cuttoff frequency of 1 MHz, and a high temperature stability of less than 0.05%FS °C −1 up to 70°C.
Abstract: Principle and basic performance of micro magnetic sensors such as the Hall element, the magneto-resistance (MR) element, the giant magneto-resistance (GMR) element, the thin-film fluxgate sensor (FGS), and the magneto-impedance (MI) element are summarized. Their basic properties are compared with each other considering a new sensing target in various modern industrial fields. A new micro-sized magnetic field sensor with a high sensitivity and a quick response is developed using the MI effect in amorphous wires and thin films. The MI sensor having a micro-sized zero-magnetostrictive amorphous wire head of about 1 mm installed in self oscillation circuits such as the Colpitts oscillator and a multivibrator circuit shows a high sensitivity with a resolution of 10 −6 Oe for ac fields and 10 −5 Oe for dc fields, quick response with a cutt-off frequency of about 1 MHz, and a high temperature stability of less than 0.05%FS °C −1 up to 70°C. A very low power consumption and highly stable MI sensor is constructed using a CMOS multivibrator. A stable measurement for a surface-flux distribution around a 2000-pole ring magnet with a diameter of 19 mm for a high density rotary encoder was carried out using the MI sensor. A small pin hole of 100 mm diameter in an iron sheet was detected at non destructive testing (NDT) using a gradient-field detection type MI sensor cancelling back ground disturbance fields. A sample of clustered magnetic particles was magnetically detected using the MI sensor probe in a simulation of detection of a brain tumor at which an injected sol was induced with the magnetic particles.
177 citations
TL;DR: In this paper, the authors proposed to detect the deflection of microfabricated bi-material cantilever beams with 3 pm resolution, which allowed the measurement of temperature, optical power and energy with 2 μK, 76 pW, and 15 fJ resolution, respectively.
Abstract: The ability to detect optically the deflections of microfabricated bi-material cantilever beams with 3 pm resolution has allowed the measurement of temperature, optical power, and energy with 2 μK, 76 pW, and 15 fJ resolution, respectively. The thickness ratio of the two beam materials is optimized to produce 40% improvement over previous designs. The governing equations for the sensor performance have been developed and form the basis for designing better cantilever shape for further performance improvements. Efforts are underway to detect cantilever deflections with 100 fm resolution, so that the thermal performance can be improved by an order of magnitude. Such unprecedentedly high resolutions are opening up promising prospects for their use in infrared detection and in studying molecular-level adsorption and surface chemical reactions.
172 citations
TL;DR: A detailed examination of the effects of deposition parameters, using LPCVD, and subsequent processing on the characteristics of silicon nitride is presented in this paper, where the properties investigated are deposition rate, refractive index, etch rate and intrinsic strain.
Abstract: A detailed examination of the effects of deposition parameters, using LPCVD, and subsequent processing on the characteristics of silicon nitride is presented The properties investigated are deposition rate, refractive index, etch rate and intrinsic strain The chemical composition of the material is determined using XPS and EPMA A close relationship between the chemical composition and mechanical properties is observed The ratio of process gas flow (using NH 3 and SiH 2 Cl 2 ) is shown to have a strong effect on all properties with deposition pressure having a secondary effect As the gas-flow ratio NH 3 /SiH 2 Cl 2 is ranged from 0176 to 1 the silicon content changes from Si/N=095 to 086, yielding a change in strain levels from 350 μϵ to 3000 μϵ Further increase in NH 3 yields only minor changes in silicon to nitrogen ratio and thus only minor changes in the film characteristics Additional thermal processing is shown to have a considerable effect on the mechanical properties of the material X-ray studies suggest that this to be due to volume shrinkage of the layer and not phase transformations involving crystallographic changes Tuning of the film properties through the processing parameters is shown
168 citations
TL;DR: The giant magneto-impedance effect (GMI) as mentioned in this paper describes the large relative change of the impedance observed in magnetically very soft ribbon and wire alloys under the application of dc magnetic fields (units of kA m 1 ).
Abstract: The giant magneto-impedance effect (GMI) consists of the large relative change of the impedance (up to around 300%) observed in magnetically very soft ribbon and wire alloys under the application of dc magnetic fields (units of kA m 1 ). The phenomenology of the GMI effect is firstly described including a discussion about its origin which mainly lies in the classical skin-effect. An alternative approach to GMI phenomena considering equivalent circuits is also introduced. The main requirements to detect GMI is to count on a sample with very large circular susceptibility and reduced resistivity provided the frequency of the ac current flowing along the sample (necessary to evaluate the impedance) is high enough (roughly above 0.1 MHz for most samples here considered). The dependence on dc magnetic field, mechanical stresses and particularly on thermal treatments resulting in the induced magnetic anisotropies or in the devitrification of amorphous samples into a nanocrystalline structure are reviewed. First results on GMI in glass-coated amorphous microwires are also reported. The use of the GMI as a tool for studying the inner circular magnetization process or for evaluating the magnetostriction is introduced. Finally, a description on various aspects regarding the development of magnetic field, current, proximity and stress sensor applications is presented.
163 citations
TL;DR: In this article, the authors proposed that the actual bonding is initiated by the dissolution of the oxide layer by silicidation of the titanium adhesion/barrier layer, which enables the formation of the euteetic phase.
Abstract: The actual mechanism involved in Au-Si wafer bonding is controversial. Usually a titanium or chromium layer is deposited in between the (oxidized) silicon substrate and the gold layer to ensure adhesion. The resulting bond of two such wafers after annealing is generally considered to be eutectic, however, the bond temperature required is higher than would be expected from the Au-Si eutectic temperature. Moreover, silicide grains are formed at the bonding interface. In this paper it is proposed that the actual bonding is initiated by the dissolution of the oxide layer by silicidation of the titanium adhesion/barrier layer. The subsequent direct Au-Si contact enables the formation of the euteetic phase. The silicidation is required to obtain the eutectic alloy with 19 at.% Si despite the Ti diffusion barrier. The bonding temperature required is, therefore, set by the silicidation process rather than by the eutectic phase. Several experiments have been designed to support this theory. AI-Si eutectic bonding has been investigated, as it is not complicated by an adhesion metal and experiments demonstrate reliable bonding close to its eutectic temperature. Moreover, a Ti/Au/Si/Au stack has been fabricated to be used as a eutectic solder, giving bonding at a temperature not affected by silicidation. Keywords Eutectic bonding Gold Silicide bonding Silicon Wafer bonding
161 citations
TL;DR: In this paper, a study of tetramethylammonium hydroxide (TMAH) etching of silicon and the interaction of etching parameters has been carried out.
Abstract: A study of tetramethylammonium hydroxide (TMAH) etching of silicon and the interaction of etching parameters has been carried out. We find that the silicon etch rate increases as the TMAH concentration increases and it reaches a maximum at 4 wt.%. The etch rate of n-type silicon is found to be slightly higher than that of p-type silicon. We conclude that illumination has no effect on the etch rate with our present experimental set-up. Etching experiments on silicon oxide layers show that both wet and dry oxides etch faster in lower TMAH concentration, and wet oxide generally etches faster than a dry oxide layer. A higher temperature also results in a higher etch rate for both the wet and dry oxides. From factorial analysis, we conclude that for silicon etching, the interaction between TMAH concentration and substrate type is the strongest. The silicon oxide etching experiments show that temperature is the most prominent factor and the most pronounced interaction exists between temperature and TMAH concentration.
134 citations
TL;DR: In this article, a new generation of flexible and extremely light-weight electrode arrays with integrated cables was developed, which overcomes the "classical" separation of substrate and insulation layers.
Abstract: It has been shown previously that peripheral nerve axons regenerate through microvias in silicon devices. A major challenge in the design of a biocompatible interface is to establish a reliable electrical and mechanical interconnection to signal-processing and transmission electronics which allows simultaneous multichannel recordings or stimulation of nerves. This paper describes the on-going work of developing a new generation of flexible and extremely light-weight electrode arrays with integrated cables. A process technology has been established to fabricate a multilayer device with micromachining methods, which overcomes the ‘classical’ separation of substrate and insulation layers. The micromachined electrodes exhibit promising mechanical stability and high insulation resistance.
130 citations
TL;DR: In this article, the polymerase chain reaction (PCR) is used for the in vitro amplification of nucleic acid molecules using a cycle of thermally controlled reaction steps, using a start molecule can be multiplied cycle by cycle up to factors of about 10 9.
Abstract: The polymerase chain reaction (PCR) is a molecular biological method for the in vitro amplification of nucleic acid molecules. Using a cycle of thermally controlled reaction steps, a start molecule can be multiplied cycle by cycle up to factors of about 10 9 . An efficient PCR relies particularly on fast heating and cooling processes, high temperature uniformity and small-sized devices. Here miniaturized thermocyclers show important advantages. Silicon-based thermocyclers with one, two, and ten chambers for volumes in the microlitre range have been prepared in order to realize fast thermocycling by high heating and cooling rates. The presented chip elements have dimensions of 20 mm × 18 mm and a weight of about 1 g.
129 citations
TL;DR: She sheep IgG is immobilized on the device surface as a receptor layer for detection of antisheep IgG in buffer solution to investigate the kinetics of the antibody-antigen binding.
Abstract: A Love wave acoustic device has been utilized for monitoring antibody-antigen immunoreactions in aqueous solutions in real time. High sensitivity and selectivity are achieved. In this study, sheep IgG is immobilized on the device surface as a receptor layer for detection of antisheep IgG in buffer solution. The kinetics of the antibody-antigen binding are investigated by monitoring the frequency change against reaction time for a wide range of antibody concentrations. A general analytic expression for the frequency against time and antibody concentrations is derived. A response to a concentration of 1 ng ml −1 is unambiguously detected. A dual-channel delay-line configuration. with one channel for sensing and the other as reference, is used to give a comparison of specific and non-specific responses as well as to reduce the temperature effects. The Love wave sensor is robust, reliable and reusable many times.
AVL1
Abstract: Single-crystalline GaPO 4 , gallium phosphate (more precisely gallium orthophosphate), is a new piezoelectric material which is very similar to quartz in its crystal structure but has a much higher thermal stability, a higher piezoelectric effect, larger electromechanical coupling constants and temperature-compensated cuts for bulk acoustic wave (BAW) and surface acoustic wave (SAW) applications. It is thus a promising material for sensor applications in the temperature range up to 900°C. The first products are already on the market: uncooled pressure sensors for combustion engines, with sensitivity and stability surpassing those attainable with quartz. As the crystal growth process is reaching larger quantity and higher quality, gallium phosphate will be the material for further new applications exceeding the possibilities of conventional materials.
TL;DR: In this paper, a new method is presented for microfabricating silicon-based neural probes that are designed for neurobiology research, which provide unique capabilities to record high-resolution signals simultaneously from multiple, precisely defined locations within neural tissue.
Abstract: A new method is presented for microfabricating silicon-based neural probes that are designed for neurobiology research. Such probes provide unique capabilities to record high-resolution signals simultaneously from multiple, precisely defined locations within neural tissue. The fabrication process utilizes a plasma etch to define the probe outline, resulting in sharp tips and compatibility with standard CMOS processes. A low-noise amplifier array has been fabricated through the MOSIS service to complete a system that has been used in multiple successful physiological experiments.
TL;DR: In this article, pyroelectric thin-film point detectors and 1 x 12 arrays have been fabricated and characterized and the measured current and voltage response as a function of modulation frequency of a 1 × 12 array element is compared with finite-element calculations.
Abstract: Pyroelectric thin-film point detectors and 1 x 12 arrays have been fabricated and characterized. They consist of sol-gel-deposited PZT thin-film elements on micromachined Si3N4/SiO2 membranes. The measured current and voltage response as a function of modulation frequency of a 1 x 12 array element is compared with finite-element calculations. Voltage responsivities of almost 3000 V W-1 in vacuum and 800 V W-1 in air have been achieved for 0.4 mm x 0.9 mm elements. Some point detectors have been completely packaged and correct operation in a movement detection system has been demonstrated.
TL;DR: In this article, a decoupled wrist force sensor was designed to provide increased force sensitivity with minimum stiffness, the lowest condition number, and an excellent decouple calibration matrix, and a simple 6×6 calibration matrix affords genuine savings in calculation time.
Abstract: A strategy for optimizing the design of a new type of wrist force sensor is presented. The design variables are the geometric sizes of the elastic sensor body, with sliding and rotating boundary conditions connected with the rigid rim. The calibration matrix, the condition number, strain-gage sensitivity, and strain gages glued to the sensor body are used to evaluate the performance of the force sensor. The finite-element method is employed here for numerical analysis of the elastic sensor body. The optimal design problem is solved by a penalty method determining the design variables. The natural frequencies and the von Mises stress are included in the constraint conditions in order to retain the force sensor within the higher natural frequency range and avoid failure, respectively. Based on the design criteria, a novel decoupled wrist force sensor is devised which, compared to existing commonly used force sensors, provides increased force sensitivity with minimum stiffness, the lowest condition number, and an excellent decoupled calibration matrix. The simple 6×6 calibration matrix affords genuine savings in calculation time and ensures the possibility of real-time control for a robot arm.
TL;DR: In this article, the main objective of the proposed research is the development of a production technology for three-dimensional micromechanical structures together with a study of the mechanical properties of these structures.
Abstract: Currently, nearly all microcomponents are fabricated by micro-electronic production technologies like etching, deposition and other (photo) lithographic techniques. In this way, main emphasis has been put on surface micromechanics. The major challenge for the future will be the development of real three-dimensional microstructures. The main objective of the proposed research is the development of a production technology for three-dimensional micromechanical structures together with a study of the mechanical properties of these structures. Electrodischarge machining (EDM) is a versatile technique which is very well suited for machining complex microstructures. This paper starts with an overview of EDM technology, the current state-of-the-art of micro EDM, and a comparison of EDM with other micromachining technologies. Afterwards, the basic parameters for EDM of silicon are derived. It will be demonstrated that EDM of silicon is not only feasible, but also forms an interesting, powerful and complementary alternative to traditional silicon micromachining.
TL;DR: This paper describes implantable drug-delivery systems based on shape memory alloy micro-actuation, designed for use with solid drugs while a second design enables delivery of liquid drugs.
Abstract: Shape memory alloy actuators feature an extremely high power-to-volume ratio. This property is a major advantage for miniature applications. This paper describes implantable drug-delivery systems based on shape memory alloy micro-actuation. A first type is designed for use with solid drugs while a second design enables delivery of liquid drugs. The operating principle of the latter system is based on a precisely controlled discontinuous release from a pressurized reservoir. It is realized using a shape memory actuated microwave system. One dose can be controlled with an accuracy up to 5 μl. The system is remotely powered and controlled using a transcutaneous transformer. A refilling possibility based on transcutaneous injections is provided. The design of the valve is such that it can be mounted on a printed circuit board together with the other electrical components. Furthermore, the valve is optimized towards aspects like biocompatibility, low-cost production, lifetime, safety and minimal dimensions. The drug-delivery system is aiming at patients who need multiple injections each day over a long period of time. The current prototype could already reduce the number of injections by a factor of 200. By further miniaturization a reduction factor of 3000 could be obtained.
TL;DR: In this paper, an optical flow-measurement technique has been developed to enhance the measurement range into the desired low flow range (10 -3 to 1 μl min -1 ).
Abstract: To investigate the performance of microengineered fluid channels in liquid dosing applications, flow-rate measurements have been performed with various channel geometries in a range from 0.01 to 1000 μl min -1 . An optical flow-measurement technique has been developed to enhance the measurement range into the desired low flow range (10 -3 to 1 μl min -1 ), and is compared to a standard gravimetric method, which is preferably used for flow rates above 1 μl min -1 . In addition, influences of the temperture-dependent viscosity and effects arising from fluidmechanical characteristics are studied. These influences are also calculated from laminar flow theory and semi-emprical models to obtain a theoretical model. It is found that the theoretical model is able to describe the measurement results well in the whole flow range. The model is implemented on a PC-based system, which measures the pressure drop across the microchannel and the fluid temperature and calculates the flow. In a temperature range from 20 to 50°C excellent agreement is found.
TL;DR: In this article, an efficient algorithm for self-consistent analysis of 3D microelectromechanical systems (MEMS) is described, which employs a hybrid finite-element/boundary-element technique for coupled mechanical and electrical analysis.
Abstract: An efficient algorithm for self-consistent analysis of three-dimensional (3-D) microelectromechanical systems (MEMS) is described. The algorithm employs a hybrid finite-element/boundary-element technique for coupled mechanical and electrical analysis. The nonlinear coupled equations are solved by employing a Newton-GMRES technique. The coupled algorithm is shown to converge rapidly and is much faster than relaxation for tightly coupled cases.
TL;DR: In this article, an intensity-based fiber-optic liquid-level sensor for point measurement is described, where the sensing principle is based on the total internal reflection of light which is disturbed by contact with a liquid.
Abstract: An intensity-based fiber-optic liquid-level sensor for point measurement is described. The sensing principle is based on the total internal reflection of light, which is disturbed by contact with a liquid. The main problems with this kind of level sensor are discussed. The performance of the sensor has been studied using four different shapes of the tips of the sensing elements: conical, rounded conical, second-order polynomial and third-order polynomial.
TL;DR: In this article, a low thermal budget technique is proposed for the preparation of thermally isolated silicon membranes, which eliminates the need for epitaxial substrates and backside alignment and proves to be very efficient in the realization of a high-temperature micro-hotplate operating with minimum power consumption for the purpose of integrated gas sensors.
Abstract: A novel low thermal budget technique is proposed for the preparation of thermally isolated silicon membranes. The selective formation of porous silicon in a p-type silicon wafer results in an undercut profile below the implanted n-type silicon regions. The sacrificial porous layer is subsequently removed in a dilute KOH solution. A non-stoichiometric LPCVD nitride layer combination forms the suspension of the single-crystalline silicon membranes. This technique eliminates the need for epitaxial substrates and backside alignment, and proves to be very efficient in the realization of a high-temperature micro-hotplate operating with minimum power consumption for the purpose of integrated gas sensors.
TL;DR: In this article, a micromachined diffraction gratings were mounted on CCD imaging devices for high-dispersion and -sensitivity applications, and the other for low-cost consumer applications.
Abstract: Miniature spectrometers have been demonstrated by mounting micromachined diffraction gratings onto CCD imaging devices. Two implementations are tested: one for high-dispersion and -sensitivity applications, and the other for low-cost consumer applications. The first system shows a dispersion of 1.7 nm/pixel and a resolution of 74.4 for the bandwidth of interest. The free spectral range of the device is designed to be in the visible range for this particular application. The diffraction efficiency of the system is 63%. The second, low-cost system demonstrates a dispersion and resolution of 2.55 nm/pixel and 69.8, respectively. These specifications are comparable to that of a conventional, low-end commercial spectrometer. Results are shown for their applications in biochemical analysis. Further optimization is sought by adding micromachined lenses and creating specialized, computer-generated gratings to compress and shape the spectral signal.
TL;DR: In this paper, the authors discuss the modelling, design and characterization of planar microcoils to be used in telemetry systems that supply energy to miniaturized implants, and show that a power of a few milliwatts is feasible.
Abstract: This paper discusses the modelling, design and characterization of planar microcoils to be used in telemetry systems that supply energy to miniaturized implants. Parasitic electrical effects that may become important at a.c. frequencies of several megahertz are evaluated. The fabrication process and electrical characterization of planar receiver microcoils will be described, and it will be shown that a power of a few milliwatts is feasible.
TL;DR: In this paper, the optimum shape and plane of a diaphragm and the optimum direction of gauges are analyzed by taking into account the effects of anisotropy of the piezoresistivity and elasticity and large deflection of diaphrasms.
Abstract: Optimum design considerations for silicon piezoresistive pressure sensors are carried out on the basis of the design restriction release produced by recent progress in microwave plasma etching technology. The optimum shape and plane of a diaphragm and the optimum direction of gauges are analysed by taking into account the effects of anisotropy of the piezoresistivity and elasticity and large deflection of diaphragms. A new index η, which expresses the relative performance of sensors, is introduced for the optimal gauge direction on the optimal diaphragm plane. It is found that the optimum design is as follows: four gauges are aligned on a 〈111〉 direction on a {110} plane square diaphragm with a centre boss.
TL;DR: In this paper, a new encapsulation technique to seal a vacuum-tube microcavity hermetically at low pressures, based on aluminium evaporation, is presented and its performance is compared to conventional low-pressure chemical vapour deposition (LPCVD) reactive sealing.
Abstract: A new encapsulation technique to seal a vacuum-tube microcavity hermetically at low pressures, based on aluminium evaporation, is presented and its performance is compared to conventional low-pressure chemical vapour deposition (LPCVD) reactive sealing. The microdiode consists of an in-cavity recessed single-crystalline silicon cathode tip above which a polycrystalline silicon anode is suspended on a silicon-rich nitride layer. The diode cavity is cleared from the sacrificial oxide in buffered HF through the horizontal etch-access channels between the polysilicon anode and the silicon-rich nitride isolation layer. Vacuum sealing of the cavity using LPCVD polycrystalline silicon results in polysilicon deposits ( > 50 nm) inside the cavity, and thus in a non-acceptable degradation of the cathode-tip curvature. When sealing is performed using aluminium evaporation, no deposits inside the cavity are observed and pressures below 10 Pa can be expected. Applications of the technique presented are not restricted to micro vacuum diodes, but also include various type of hermetically sealed micromechanical structures, where deposits inside the sealed cavity are undesirable.
TL;DR: In this article, a new fabrication method for borosilicate glass capillary tubes is presented, which is used for miniaturized total chemical analysis systems (μ-TAS).
Abstract: In this paper a new fabrication method for borosilicate glass capillary tubes is presented. As the interest in miniaturized total chemical analysis systems (μ-TAS) is increasing, the need for fluidic paths is growing and thus the study of microchannels, microtubes and microcolumns is an important topic of the microfluidic area. The capillary tubes presented here are fabricated by structuring and bonding three borosilicate glass wafers (7740 Corning Pyrex sR). Microchannels with lateral inlets and outlets have been successfully realized and well-defined size and shape have been obtained. Several capillary tubes with widths from 340 to 940 μm have been realized as well as different section shapes, which can be circular, elliptic or quasi-rectangular. The main fabrication steps and first characterizations are reported.
TL;DR: In this article, focused ion beam (FIB) patterned and chemically etched 3D Si structures with nanoscale thickness have been fabricated using 35 keV Ga + ion implantation and subsequent anisotropic etching in KOH/H 2 O solution.
Abstract: The further miniaturization of silicon micromechanical structures in combination with the highly developed microelectronic technology at the micrometre and sub-micrometre level will lead to a new generation of microdevices. A modern technique to fabricate three-dimensional micromechanical structures is the combination of high-concentration p′ -doping by writing ion implantation using a focused ion beam (FIB) and subsequent anisotropic and selective wet chemical etching. FIB-patterned and chemically etched 3D Si structures with nanoscale thickness have been fabricated using 35 keV Ga + ion implantation and subsequent anisotropic etching in KOH/H 2 O solution. Design and fabrication considerations to achieve freestanding Si structures are discussed and some typical structures are shown.
TL;DR: A theory of a piezoelectric axisymmetric bimorph is presented in this paper, where the bending moments and stretching forces produced by voltage are derived, and the results obtained by means of the described theory and numerical methods have been verified experimentally or by comparing them with results obtained analytically for a simple structure.
Abstract: A theory of a piezoelectric axisymmetric bimorph is presented in this paper. Bimorphs are often used as electroacoustic transducers, but their use is much wider. A piezoelectic bimorph consists of two or more layers which are placed asymmetrically to the middle surface of the structure. When voltage is supplied to the bimorph, a bending moment is produced which causes transversal deflections of the structure. Average elastic parameters are calculated. Equations for the calculation of bending moments and stretching forces produced by voltage are derived. When the bimorph is a shell of revolution with any shape of meridian, the derived equations can be solved by numerical methods. The finite-element method (FEM) is applied to solve this problem. The bimorph can also be used as a sensor. A theory of such a sensor is also presented. The results obtained by means of the described theory and numerical methods have been verified experimentally or by comparing them with results obtained analytically for a simple structure. It has been proved theoretically that the electric signal produced by a circular transducer clamped on the outer rim of a piezoelectric disc is equal to zero.
TL;DR: In this article, a novel and simple method for designing multi-range electrocaloric mass-flow sensors has been presented, which is based on the asymmetrical relative positioning of heaters and temperature sensors.
Abstract: A novel and simple method for designing multi-range electrocaloric mass-flow sensors has been presented. This new method is based on the asymmetrical relative positioning of heaters and temperature sensors, which is realized by using an array of heaters or temperature sensors. A simple analytical model and a numerical model with FIDAP have been verified by experimental results. The method of asymmetrical locations extends the flexibility of a sensor chip. Different fluids and variable flow ranges can be measured by only one sensor chip without changing the design, operation modes or amplifier gain.
TL;DR: In this article, a new technology for the fabrication of silicon condenser microphones is presented, which is based on the use of polyimide, and can be performed entirely as a post process on substrates already containing integrated circuits.
Abstract: A new technology for the fabrication of silicon condenser microphones is presented. The technology, which is based on the use of polyimide, can be performed entirely as a post process on substrates already containing integrated circuits. Microphones with an open-circuit sensitivity of 8.1 mV Pa?1, and a flat frequency response (±2 dB) between 100 Hz and 15 kHz have been fabricated with this technology. The bias voltage used in these measurements is 15 V, and the measured noise level with zero bias is 24 dB SPL, which is sufficient for most acoustic applications, including hearing aids.