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Showing papers in "Journal of Micromechanics and Microengineering in 1993"


Journal ArticleDOI
TL;DR: An overview of research activities in the field of fluid components or systems built with microfabrication technologies is given in this paper, focusing on the fluidic behaviour of the various devices, such as valves, pumps and flow sensors as well as the possibilities and pitfalls related to the modelling of these devices using simple flow theory.
Abstract: An overview is given of research activities in the field of fluid components or systems built with microfabrication technologies. This review focuses on the fluidic behaviour of the various devices, such as valves, pumps and flow sensors as well as the possibilities and pitfalls related to the modelling of these devices using simple flow theory. Finally, a number of microfluidic systems are described and comments on future trends are given.

1,153 citations


Journal ArticleDOI
TL;DR: In this paper, a model of the electromechanical performance of bimetallic cantilever microactuators by deriving the relationship between the tip deflection and change in temperature using a simple analytical approach is presented.
Abstract: The authors present a model of the electromechanical performance of bimetallic cantilever microactuators by deriving the relationship between the tip deflection and change in temperature using a simple analytical approach. The model is verified by comparison with finite element analysis and published experimental data. The maximum tip force generated by a bimetallic cantilever beam is calculated by finding the reaction force needed at the tip to prevent cantilever beam deflection.

262 citations


Journal ArticleDOI
TL;DR: In this paper, tensile strength and elastic modulus measurements of low pressure chemical vapour deposited (LPCVD) polysilicon films were performed on freestanding microtensile specimens (fibers) fabricated from the films.
Abstract: Tensile strength and elastic modulus measurements of low-pressure chemical vapour deposited (LPCVD) polysilicon films were performed on freestanding microtensile specimens (fibers) fabricated from the films. Various annealing treatments were employed to alter the polysilicon grain size. Fibers were fabricated from films with grain sizes of 50, 100, and 500 nm. The fiber cross sectional area was 3.3 mu m3 and the gauge section was 30 mu m long. The fibers failed in a brittle fashion with tensile strengths between 2.7 and 3.4 GPa. Fibers fabricated from polysilicon with 500 nm grain size had uniform equiaxial grains and were stronger than fibers made from smaller grain size material. This higher strength can be attributed to the better interface between the 500 nm grains as a result of the annealing process. The average elastic modulus of the fibers was 175 GPa.

91 citations


Journal ArticleDOI
TL;DR: In this article, 1-, 2-propanol and 1-, 3-pentanol flow measurements through 5, 12, and 25 mu m hydraulic diameter microchannels are reported, which indicate that the Poiseuille number depends on the temperature and molecular isomerism of the liquid.
Abstract: Liquid (1-, 2-propanol and 1-, 3-pentanol) flow measurements through 5, 12, and 25 mu m hydraulic diameter microchannels are reported. These experiments indicate that the Poiseuille number depends on the temperature and, possibly, on the molecular isomerism of the liquid. The Poiseuille number increases by as much as 25% and 10% for the 12 and 25 mu m channels, respectively, as the temperature increases from 0 to 85 degrees C. These results are contrary to the predictions derived from the Navier-Stokes equation, which show that the Poiseuille number is independent of these parameters. The precision of these measurements is of the order of +or-2%, so that the observed deviations from theory are not readily explained by experimental errors.

80 citations


Journal ArticleDOI
TL;DR: In this article, the main characteristics of the electrodeposition process and specific properties of negative polyimide and positive photoresists are discussed and two realizations, an on-chip high-density array of electromagnets developed for high-performance printing heads, and a micromachined microphone, demonstrate that not only 3D electroplated microstructures are achievable but also the integration of electronics is possible on the same silicon substrate.
Abstract: Metal electrodeposition combined with resist micropatterning techniques provides a powerful tool for the fabrication of thick metallic microstructures. This paper discusses the main characteristics of the electrodeposition process and describes the specific properties of negative polyimide and positive photoresists. The innovative use of this technique is illustrated by the presentation of two realizations, an on-chip high-density array of electromagnets developed for high-performance printing heads, and a micromachined microphone. These realizations demonstrate that not only the real 3D electroplated microstructures are achievable but also the integration of electronics is possible on the same silicon substrate.

69 citations


Journal ArticleDOI
TL;DR: In this paper, the conducting polymer was used as an artificial muscle to bend the polymer bilayer, which results in bending of the bilayer and bending the fingers of the hand.
Abstract: Microfabrication techniques allow one to construct metal/polymer bilayers anchored at one end to a substrate and free to move at the other end. Electrically controlled 'fingers' were fabricated using the conducting polymer as an artificial muscle: doping and undoping the conjugated polymer causes a change in volume of this layer which results in bending of the bilayer. Grasping hands, fingers with sensing tips, and micropumps can be envisioned. Standing in the way of immediate fabrication are several materials challenges including layer adhesion, material compatibility, sacrificial layer improvement, and low-temperature processing techniques.

68 citations


Journal ArticleDOI
TL;DR: In this article, a planar micromachined spiral inductive structure with relatively high inductance at low (Hz-kHz) frequencies is designed and fabricated for integrated magnetic microactuator applications and other purposes.
Abstract: In this work, planar micromachined spiral inductive structures with relatively high inductance at low (Hz-kHz) frequencies are designed and fabricated for integrated magnetic microactuator applications and other purposes. Two types of multilayer micromachined inductors have been investigated. The first structure is a standard planar inductor spiral. To this structure we have added an electroplated high-permeability nickel-iron (Ni/Fe) magnetic core, which forms a central core to concentrate flux and completely encapsulates the windings, thus minimizing magnetic interference. For a typical 36-turn device 3 mm*3 mm in area, an inductance of approximately 20 mu H was obtained. The structure with a magnetic core has an inductance four to five times greater than a similar structure without a magnetic core. The specific inductance of our structure (inductance per unit area) is 2.2 mu H mm-2 at 10 kHz, which is one of the highest inductance values ever achieved in an integrated planar inductive component at low frequency. Since the structure of the spiral-type inductor is similar to those of planar magnetic microactuators such as micropumps, microvalves and microrelays, several low-frequency microactuator applications are expected to be possible with this inductor.

63 citations


Journal ArticleDOI
TL;DR: An electrochemical technique that makes use of pores of nuclear track filters as templates for synthesis of metal-semiconductor (Cu-Se) heterostructures and Se microtubules is described in this paper.
Abstract: An electrochemical technique is described that makes use of pores of nuclear track filters as templates for synthesis of metal-semiconductor (Cu-Se) heterostructures and Se microtubules Some possible applications of the microtubules and heterostructures are also suggested

58 citations


Journal ArticleDOI
TL;DR: In this article, the Wulff-Jaccodine tool is used to simulate the cinematic contours of a polygonal contour, depending on the applied sets of etch rates this contour represents the underetching, the contour of the etch ground or the cross section through the chip.
Abstract: Starting from a graphic file of an etch mask the tool uses the two-dimensional Wulff-Jaccodine construction to simulate the cinematic of a polygonal contour. Depending on the applied sets of etch rates this contour represents the underetching, the contour of the etch ground or the cross section through the chip. Knowing the inclinations of side walls the complete etched relief can be constructed. The tool is suitable for any material or orientation of crystal and for any composition and temperature of etchants provided that the related etch rates are available.

54 citations


Journal ArticleDOI
TL;DR: In this paper, side-wall profiles in etched grooves were used to produce two-dimensional etch diagrams for micromachining of monocrystalline quartz in, for instance, hydrofluoride-based etchants.
Abstract: The etch rate in monocrystalline quartz depends on the crystalline orientation. Etch-rate diagrams for micromachining of monocrystalline quartz in, for instance, hydrofluoride-based etchants, are a necessity if one requires the best manufacturing conditions for an etched structure. In this paper we use the development of side-wall profiles in etched grooves, on a Z-cut quartz wafer, to produce two-dimensional etch diagrams. The etch conditions are eight combinations of temperature, from 22 degrees C to 80 degrees C, and etchant mixtures of HF and NH4F diluted in water.

52 citations


Journal ArticleDOI
TL;DR: In this paper, the technology of freestanding parts of polysilicon is described, and the etching process and the use of different masking layers are investigated, and a thick sacrificial layer for applications in bulk and surface micromachining can be achieved with porous silicon.
Abstract: A thick sacrificial layer for applications in bulk and surface micromachining can be achieved with porous silicon. The technology of freestanding parts of polysilicon is described. The etching process and the use of different masking layers are investigated.

Journal ArticleDOI
TL;DR: In this article, active microvalves and micropumps have been manufactured by combining membranes with LIGA structures of metal, and they have been covered by glass platelets to form cavities for microfluidic components.
Abstract: Active microvalves and micropumps have been manufactured by combining membranes with LIGA structures of metal. These structures have been galvanized on thin titanium membranes. They have been covered by glass platelets to form cavities for microfluidic components. After separation from the substrate the cavities are tightly closed on one side by a thin micromembrane, which acts as a functional part of the fluidic component.

Journal ArticleDOI
TL;DR: In this article, the thermal transport properties of four different material layers as produced by a commercial IC CMOS process (AMS, Austria Mikro Systeme) were measured in the temperature range from 100 to 420 K.
Abstract: The authors have measured the thermal transport properties of four different material layers as produced by a commercial IC CMOS process (AMS, Austria Mikro Systeme). The thermal conductivities of two differently doped polycrystalline silicon layers, of a silicon dioxide isolation layer, and of one metal layer are reported in the temperature range from 100 to 420 K. The characterization was carried out with specially designed microelectromechanical test structures. At room temperature, the thermal conductivities of the n- and p-doped polysilicon layers were found to be 29 and 18 W K-1 m-1, respectively. These values represent a significant decrease from the 156 W K-1 m-1, of high-purity monocrystalline bulk silicon. The thermal conductivities of silicon dioxide and of the first aluminium metallization layer were determined as 1.15 and 180 W K-1 m-1, at 300 K, which are close to known bulk values.

Journal ArticleDOI
TL;DR: In this paper, a field emitter triode in the collector-assisted field emission mode is used to obtain a strong dependency of the collector current as a function of emitter-to-collector distance.
Abstract: By operating the field emitter triode in the collector-assisted field emission mode, a strong dependency of the collector current as a function of emitter-to-collector distance is obtained. This property can be used in the construction of displacement and/or pressure sensors. Experimental results are presented for a silicon emitter array. These include displacement measurements under DC and AC conditions, sensitivity, and temperature dependency from room temperature to 200 degrees C. From experimental data, model parameters for the Fowler-Nordheim equation are deduced. These parameters can then be used to calculate the performance of the device as a function of gate and collector voltages and of deflection.

Journal ArticleDOI
TL;DR: In this article, a comparison between the efficiency of thermal and piezoelectric excitations, as well as with external electrostatic excitation, is made, and the complex problem of correct choice of elastic constants is mentioned.
Abstract: There is a striking similarity between piezoelectric, thermal and other internal volume forces. Thus, methods used for understanding and predicting piezoelectric vibrations can be used for, for instance, thermally activated vibrations in silicon structures. The author shows such a method for beam-shaped structures. A comparison between the efficiency of thermal and piezoelectric excitations, as well as with external electrostatic excitation, is made. The complex problem of correct choice of elastic constants is mentioned.

Journal ArticleDOI
TL;DR: In this article, thin square membranes including a deep circular corrugation were realized and tested for application in a strain-based pressure sensor, where package-induced stresses are reduced and relief of the residual stress is obtained, resulting in a large pressure sensitivity and a reduced temperature sensitivity.
Abstract: Thin square membranes including a deep circular corrugation are realized and tested for application in a strain-based pressure sensor. Package-induced stresses are reduced and relief of the residual stress is obtained, resulting in a large pressure sensitivity and a reduced temperature sensitivity. Finite element method simulations were carried out, showing that the pressure-deflection behaviour of the structure is close to that of a circular membrane with clamped edge but free radial motion.

Journal ArticleDOI
TL;DR: In this article, a concept involving an accelerometer made completely with surface micromachining technology is introduced, where the sensor makes use of an effect based on electostatic force, which describes the transition from the stable to an unstable state of the system and depends on the effective acceleration.
Abstract: A concept involving an accelerometer made completely with surface micromachining technology is introduced. The sensor makes use of an effect based on electostatic force. Since only small surfaces are required, it is possible to keep the design relatively simple. In contrast to the capacitive principle, a so called critical voltage is measured which describes the transition from the stable to an unstable state of the system and depends on the effective acceleration. Preliminary tests and calculations indicate high sensitivity between 0.6 mV g-1 and 100 mV g-1 (unamplified) for structure with lengths between 120 mu m and 500 mu m.

Journal ArticleDOI
TL;DR: In this paper, anisotropic etching of a (110) oriented silicon wafer has been used to realize a differential capacitive force sensor, which can be adjusted to measure force in the range 0.01 N to 10 N or, in a low rigidity version, to act as a high precision displacement sensor with an expected resolution of 20 nm.
Abstract: Anisotropic etching of a (110) oriented silicon wafer has been used to realize a differential capacitive force sensor. This design is based on a simple concept allowing force to be measured in the plane of the sensor, giving a new and original product in the field of small force measurements. These sensors can be adjusted to measure force in the range 0.01 N to 10 N or, in a low rigidity version, to act as a high precision displacement sensor with an expected resolution of 20 nm. These sensors are planed to be used with a commercial capacitance measurement chip (nominal capacitance: 1 pF, resolution: 1 fF).

Journal ArticleDOI
TL;DR: In this article, a generalized analytical formulation of mechanical deformations as a function of applied electric field is derived for an arbitrary lay-up of piezoelectric microactuators.
Abstract: Piezoelectric microactuators may be considered as multilayer laminated composites consisting of alternating layers of piezoelectric and non-piezoelectric materials A generalized analytical formulation of mechanical deformations as a function of applied electric field is derived for an arbitrary lay-up of such laminates Based on the generalized theory developed, specific formulae for the electromechanical performance of two cantilever microactuator lay-up geometries including a single piezo/elastic laminate and a bimorph, are derived In the modeling of the electromechanical performance of piezoelectric microactuators, the present model incorporates both d211 and d222 Furthermore, the elastic properties of both the piezoelectric and the elastic materials have been considered The developed model is evaluated based on a comparison with results from experiment

Journal ArticleDOI
TL;DR: The LIGA process applied on micromachined silicon substrates offers new possibilities in micro system technology, especially in micro-optics as discussed by the authors, where optical fibres and passive optical components, e.g., ball lenses having different diameters can be precisely positioned at the same optical axis.
Abstract: The LIGA process applied on micromachined silicon substrates offers new possibilities in microsystem technology, especially in micro-optics. LIGA microstructures used as fixing elements for passive micro-optical components and optical fibres are precisely adjusted to microstructures etched into silicon wafers. In this way, optical fibres and passive micro-optical components, e.g., ball lenses having different diameters can be precisely positioned at the same optical axis. In addition, other functional elements like microactuators can be integrated on the same substrate to build advanced microsystems, e.g. a switch for use with single-mode fibres.

Journal ArticleDOI
TL;DR: In this paper, a low differential pressure sensor is presented which uses a bossed diaphragm as the spring element and built-in resonant strain gauges to provide a frequency output.
Abstract: A novel design of low differential-pressure sensor is presented which uses a bossed diaphragm as the spring element and built-in resonant strain gauges to provide a frequency output. A differential resonator design is employed to compensate for unwanted frequency shifts. The degrading influence due to coupling of the resonators and solution to overcome this problem are described in some detail. A 1000 Pa device is given as a design example, predicting a sensitivity of 175 Hz Pa-1, a resolution better than 0.01 Pa and a terminal-based non-linearity of 0.1% FSO.

Journal ArticleDOI
TL;DR: In this article, the use of photoetchable glasses in the field of microsystem technology is presented. But the main advantage of these tips with respect to conventional silicon-based tips is their large aspect ratio.
Abstract: The authors present the use of photoetchable glasses in the field of microsystem technology. Its properties make it an ideal material for a wide variety of microsystems. A method to fabricate tips for atomic force microscopy out of this material is proposed. The main advantage of these tips with respect to conventional silicon-based tips is their large aspect ratio. Silicon nitride is used as a material for the cantilevers, which are on top of a glass carrier. Experimental results are presented.

Journal ArticleDOI
TL;DR: In this paper, quasi-buckling of micromachined beams with imperfections is studied. But the authors focus on the stability of postbuckling equilibrium states, instead of the traditional sudden change in deflection characteristics.
Abstract: Buckling of structures with imperfections, quasi-buckling (QB), is studied. At the bifurcation load, these structures show a smooth transition into one of the stable postbuckling equilibrium states, instead of the traditional sudden change in deflection characteristics. QB structures can show the classical snap-through buckling behaviour, i.e., a sudden change of postbuckling equilibrium state. The QB is described with a generalized temperature, Tg, representing the compression of the structure. Imperfections and distributed deflection loads are represented by a generalized pressure, pg. Experiments on micromachined beams, exposed to heating (Tg) and to a Lorentz force (pg), verify that the QB phenomena can efficiently transfer a longitudinal stress into a transversal deflection, with a scale-factor depending on both Tg and pg.

Journal ArticleDOI
TL;DR: In this paper, the microfabrication of tools so small that they enable access to the nanoworld, such as tips, flexible cantilevers, integrated deflection sensors and nanoactuators is described.
Abstract: Recent developments and advances in micro-electro-mechanical systems for nanometer-scale applications such as scanning force microscopy are presented. The microfabrication of tools so small that they enable access to the nanoworld, such as tips, flexible cantilevers, integrated deflection sensors and nanoactuators is described. Bulk and surface micromachining of mono- or polycrystalline silicon, extended by aligned-wafer-bonding, etch-back and sacrificial-layer-etching steps are major fabrication steps used. Experiments on prototypes show that these devices are promising for use as ultra-sensitive stand-alone probe micro-instruments.

Journal ArticleDOI
TL;DR: In this paper, Borophosphosilicate glass (BPSG) has been investigated for both the surface planarization of plasma-etched and refilled trenches before etchback and structural layer deposition to enable the fabrication of genuine surface-micromachined double clamped beams and the smoothing of bulk-machined surfaces up to mirror quality for optical applications.
Abstract: Borophosphosilicate glass (BPSG) has been investigated for both the surface planarization of plasma-etched and refilled trenches before etchback and structural layer deposition to enable the fabrication of genuine surface-micromachined double clamped beams and the smoothing of bulk-micromachined surfaces up to mirror quality for optical applications. Sufficient reflow has been obtained without an excessive reduction of the etch rate in HF using low-pressure chemical vapour deposition (LPCVD) with 8 sccm BCl3 flow at 950 degrees C.

Journal ArticleDOI
TL;DR: In this article, a pyroelectric infrared detector based on ZnO thin films was integrated with GaAs metal-semiconductor field effect transistor (MESFET) amplifiers.
Abstract: Piezoelectric pressure sensors and pyroelectric infrared detectors based on ZnO thin films have been integrated with GaAs metal-semiconductor field effect transistor (MESFET) amplifiers The microsensors incorporate a 1 mu m-thick sputtered ZnO capacitor supported by a 2 mu m-thick aluminium membrane formed on a semi-insulating GaAs substrate The piezoelectric pressure sensor of area 80*80 mu m2 exhibits 299 mu V mu bar-1 sensitivity at 400 Hz The voltage response of a single infrared detector of area 80*80 mu m2 is 62 mV at 10 Hz and the time constant is 53 ms Circuits using 4 mu m-gate GaAs MESFETs are fabricated using a planar, direct ion-implant process The measured transconductance of a 4 mu m-gate GaAs MESFET is 256 mS mm-1 at room temperature

Journal ArticleDOI
TL;DR: In this article, a GaAs cantilever and Si3N4 diaphragms up to 400 mu m diameter were fabricated using ion implantation and using AlGaAs etch-stop layers thin GaAs/AlGaAs membranes were produced easily.
Abstract: This paper demonstrates the different possibilities of micromachining GaAs-based materials for integrated sensors with on-chip integrated circuitry. Special emphasis was laid on the high-temperature applications. The authors report for the first time the microstructuring of GaAs by ion implantation. A GaAs cantilever and Si3N4 diaphragms up to 400 mu m diameter were fabricated using this technology. Using AlGaAs etch-stop layers thin GaAs/AlGaAs membranes can be produced easily. This technique results in excellent thermal isolation. An anemometer with an integrated electronic circuit is presented.

Journal ArticleDOI
TL;DR: In this article, the fabrication and characterization of a thermal flow sensor based on porous silicon technology is reported, developed for gas metering applications, was designed in order to maintain compatibility with a gaseous environment and to exhibit a low power consumption.
Abstract: The fabrication and characterization of a thermal flow sensor based on porous silicon technology is reported. The sensor, developed for gas metering applications, was designed in order to maintain compatibility with a gaseous environment and to exhibit a low power consumption. The different steps of the fabrication process are described with emphasis on the porous silicon technology and packaging techniques. Thermal characterizations of the sensors and measurements in continuous flows were performed.

Journal ArticleDOI
TL;DR: In this article, a closed-loop controller regulates the liquid's flow in a piezoelectric silicon micropump with a controlled output flow is presented, which can maintain a constant output flow when the pressure difference between the pump's output and input varies.
Abstract: A piezoelectric silicon micropump with a controlled output flow is presented. A closed-loop controller regulates the liquid's flow. The system can maintain a constant output flow when the pressure difference between the pump's output and input varies. This regulation has been demonstrated for flow rates from 10 mu l min-1 to 100 mu l min-1, and for pressure differences up to 100 mbar. The main components of the system as well as the results obtained are discussed.

Journal ArticleDOI
TL;DR: In this paper, the authors discuss design considerations and outline the fabrication of a neural connector comprising a polymer guidance channel and a microfabricated silicon dice incorporating an array of via holes.
Abstract: The authors discuss design considerations and outline the fabrication of a neural connector comprising a polymer guidance channel and a microfabricated silicon dice incorporating an array of via holes. The proposed neural interface could ultimately find application in the control of motor/sensory limb prostheses for amputees and for the direct stimulation of limbs in spinal cord injury cases. A number of different connectors have been fabricated and some of them have been implanted in rabbits.