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Micro Electro Mechanical Systems, 1996, MEMS '96, Proceedings. An Investigation of Micro Structures, Sensors, Actuators, Machines and Systems. IEEE, The Ninth Annual International Workshop on

Date 11-15 Feb. 1996

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Displaying Results 1 - 25 of 92
  • Proceedings of Ninth International Workshop on Micro Electromechanical Systems

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  • Active endoscope with SMA (Shape Memory Alloy) coil springs

    Page(s): 290 - 295
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    This paper describes the development of an active endoscope which allows a large bending angle for practical application and has a simple structure for miniaturization. An active endoscope (image fiber with 4200 pixels and light guide fiber) 2 mm in outer diameter with a shape memory alloy (SMA) actuator was designed and fabricated. The practical specifications of the SMA coil spring were determined based on a design chart and equation. The active endoscope consists of a bending part, the SMA actuator, and an endoscope. The mechanical properties of the bending part were investigated. The shear modulus of the SMA at room temperature and in the parent phase were determined in designing the actuators View full abstract»

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  • Comparison of wall attachment and jet deflection microfluidic amplifiers

    Page(s): 372 - 377
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    Two types of microfluidic amplifiers (unvented wall attachment and jet deflection) were examined using dry nitrogen as the test fluid. The devices were fabricated in silicon using standard micromachining methods and anodic sealing with a glass cap. Flow control and flow gain were demonstrated with supply pressures ranging up to 630 kPa. An asymmetric output flow was observed from the two output ports at sufficiently high supply pressures in both devices, suggesting possible shock wave formation. The jet deflection microfluidic amplifier presents a more symmetric behavior and provides higher flow variation than the wall attachment device. The ratio of the maximum and minimum output flows, as measured for the jet deflection device for various control and supply pressures, reveals a performance degradation at the onset of choked supply flow View full abstract»

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  • Status and new evaluation method of interfacial oxide between the directly-bonded Si wafer pairs

    Page(s): 337 - 342
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    We discovered that the shapes of the (111) facet structures were closely related to the disintegration, the spheroidization, and the stabilization of the native interfacial oxide layer in directly bonded Si wafer pairs. These (111) facet structures are generated from the anisotropic etching of (110) cross-section of bonded (100) Si wafer pairs. Also, we confirmed that most of the interfacial oxide existing at the bonding interface of a well-aligned wafer pairs were disintegrated and spheroidized by high-temperature annealing process above 900°C View full abstract»

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  • A modular micromachined high-density connector for implantable biomedical systems

    Page(s): 497 - 502
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    This paper presents a high-density, modular, low-profile, small, removable connector system developed using micromachining technologies for biomedical implants. This system consists of a silicon probe with one end in contact with the biological tissue and its back end attached to a titanium base that is fixed on the test subject. An external glass substrate, which supports a flexible polyimide diaphragm and low-noise CMOS buffers (~160 nV/√Hz), is attached to the titanium base whenever electrical recording/stimulation is to be carried out. The polyimide flexible diaphragm contains high density gold electroplated pads which match similar pads on the silicon back end. When vacuum is drawn between the silicon substrate and the polyimide diaphragm, the polyimide diaphragm deflects and the gold pads on silicon and polyimide touch, therefore establishing an electrical connection. In-vitro electrical tests have been performed on a 32-site connector system demonstrating <20 Ω contact resistance and -60 dB cross talk between adjacent channels View full abstract»

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  • Micro tensile-test system fabricated on a single crystal silicon chip

    Page(s): 360 - 364
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    We have developed a uniaxial tensile test structure on a single crystal silicon chip. This enables tensile testing of MEMS materials, such as bulk silicon and thin film materials, to be carried out directly on the chip without manipulating a small specimen during the test procedure as in previous work. The structure was designed so that uniaxial force is applied to the specimen when a lever structure on the same chip is loaded perpendicular to the surface. The chip was fabricated on a (100) silicon wafer using chemical anisotropic etching View full abstract»

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  • Transverse mode electrostatic microactuator for MEMS-based HDD slider

    Page(s): 216 - 221
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    In this paper, we propose a new head slider concept for hard disk drives (HDDs) which will be completely batch-fabricated on a sacrificial layer together with a transverse mode electrostatic microactuator using MEMS-based technology. We present the design, fabrication, and testing of a prototype electrostatic microactuator in transverse mode without a slider body just to determine the basic characteristics. Test results showed a stroke of 0.55 μm and a very high mechanical resonant frequency of 34 kHz due to the low moving mass of 0.85 μg and the large force, estimated to be 23.5 μN, generated by the actuator View full abstract»

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  • Mechanical properties of thick, surface micromachined polysilicon films

    Page(s): 343 - 348
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    Polycrystalline silicon is the most widely used structural material for surface micromachined microelectromechanical systems (MEMS). There are many advantages to using thick polysilicon films; however, due to process equipment limitations, these devices are typically fabricated from polysilicon films less than 3 μm thick. In this work, microelectromechanical test structures were designed and processed from thick (up to 10 μm) undoped and in situ boron-doped polysilicon films. The elastic moduli of the doped films were 150±30 GPa, and appeared to be independent of film thickness. The thermal oxidation of the polysilicon induced a compressive stress into the top surface of the films, which was detected as a residual stress in the polysilicon after the device fabrication was complete. The average nominal fracture toughness of the polysilicon was 2.3±0.1 MPa √m View full abstract»

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  • A force sensor using a CMOS inverter in view of its application in scanning force microscopy

    Page(s): 447 - 450
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    A force sensor using a new detection scheme is presented for scanning force microscopy. The sensor consists of a silicon cantilever and a CMOS inverter, and is based on piezoresistivity effects in a MOS transistor. The sensor principle has been verified by assembling a test structure including a large cantilever (40 mm×4 mm×0.39 mm) with an integrated MOS transistor. A deflection of 1 μm at the cantilever end yields a signal of 6.19 mV at the output of the inverter for a supply voltage of 13 V and without any amplification stage. The measured minimum detectable stress demonstrates the potential of this new detection scheme. In combination with microfabricated cantilevers, a spatial resolution better than 1 nm is expected making this sensor of interest for application in scanning force microscopy View full abstract»

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  • Coupled 3D thermo-electro-mechanical simulations of microactuators

    Page(s): 133 - 138
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    We report 3D simulations of microactuators based on the solution of consistently coupled thermo-electro-mechanical equations. The necessary solution algorithms are implemented into the MEMS simulation environment SOLIDIS and allow efficient optimization studies of geometrically complex MEMS devices. Key issues are the solution of coupled equation systems using zone partitioning, adaptive mesh refinement, mesh updating using geometrical algorithms and field smoothing for the extraction of accurate electrostatic forces View full abstract»

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  • A 1.5 V supplied, CMOS ASIC for the actuation of an electrostatic micromotor

    Page(s): 25 - 31
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    The use of electrostatic forces in micromechanical systems is well known but needs quite high voltages to produce usable forces. In this perspective paper, we present an autonomous, nonresonant, open-loop, 1.5 V battery-supplied high voltage integrated circuit able to drive an electrostatic micromotor, for opening the way to future portable applications (wristwatch like) View full abstract»

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  • Packaging and qualification of MEMS-based space systems

    Page(s): 503 - 508
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    The number of spacecraft designed and built over the next century will grow exponentially as communication satellite networks proliferate and NASA continues to push towards the development of many microspacecraft to replace its traditional “grand tour” space vehicles. Costs in the space industry are measured in terms of weight (dollars per pound launched) and reliability. Unit costs pale in comparison to launch costs and the cost of replacing an entire vehicle in the case of a catastrophic failure. Space systems present a unique application for microelectromechanical systems (MEMS) technology which can be applied to miniaturize many of the subsystems in a space vehicle, and can improve overall reliability. This paper identifies potential applications of MEMS in a space system, describes space environmental factors, and reviews efforts to develop appropriate packaging and space qualification methodologies. Finally, a flight experiment for testing the performance of typical MEMS devices and packages in the space environment is described View full abstract»

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  • Fine surface finishing method for 3-dimensional micro structures

    Page(s): 73 - 78
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    We developed a new finishing method using an advanced ECM (electrochemical machining) assisted by fine abrasive grains in order to finish surfaces of 3-dimensional micro components used in MEMS. With the method, a fine surface of selected micro-area, which is not obtained by micro-EDM (electrodischarge machining) nor conventional ECM, is created in a few minutes. We also developed an advanced machine which has a performance to make 3-D complicated micro structures with fine surfaces by the combination of the micro-EDM and the developed finishing method. The performance is achieved by a sequential process without workpiece handling from the micro-EDM to the finishing. Using the new machine, we obtained a high precision shaft with a mirror-like surface. The result is satisfactory to apply the method to make a cylindrical substrate for a rotor of micro wobble motor. We are sure that the process will be applied to producing practical micro mechanical components View full abstract»

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  • Design and fabrication of compliant micromechanisms and structures with negative Poisson's ratio

    Page(s): 365 - 371
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    This paper describes a new way to design and fabricate compliant micromechanisms and material structures with negative Poisson's ratio (NPR). The design of compliant mechanisms and material structures is accomplished in an automated way using a numerical topology optimization method. The procedure allows the user to specify the elastic properties of materials or the mechanical or geometrical advantages of compliant mechanisms and returns the optimal structures. The topologies obtained by the numerical procedure require practically no interaction by the engineer before they can be transferred to the fabrication unit. Fabrication is carried out by patterning a sputtered silicon on a PECVD-glass with a laser micromachining set-up. Subsequently the structures are etched into the underlying PECVD-glass and the glass are underetched, all in one two-step RIE process. The components are tested using a probe placed on an xy-stage. This fast prototyping allows newly developed topologies to be fabricated and tested within the same day View full abstract»

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  • A monolithic optical displacement measurement microsystem

    Page(s): 400 - 405
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    A monolithically integrated optical displacement measurement microsystem is presented. The microsystem consists of a Michelson interferometer with an integrated DBR laser and waveguide photodetector, fabricated on a single GaAs-based chip. Displacement measurements with sub-100 nm resolution have been performed, requiring only the alignment of the interferometer with an external lens for focusing the measurement beam. Obviating the need for alignment of the interferometer components implies that such an optical chip may be used for precision position or displacement measurement in movable MEMS or as part of a more complex semiconductor-based opto-mechanical microsystem View full abstract»

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  • A wide frequency range, rugged silicon micro accelerometer with overrange stops

    Page(s): 180 - 185
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    A rugged and wide frequency range silicon micro accelerometer with integral overrange stops has been developed for use in anthropomorphic test dummies and on vehicles for crash and sled safety testing. The accelerometer utilizes a monolithic piezoresistive cantilever type sensor crafted on (110) silicon wafer. Taking advantage of the unique vertical wall etching capability on (110) silicon, the geometry of the hinge, mass, and stop-gap can be defined precisely. It is limited only by the photolithographic accuracy instead of the etching time control. The piezoresistive gages are etch freed from the silicon wafer. Their cross sectional area is very small, 0.6 μm by 4.2 μm, thus needing very little strain energy to produce a useful signal. By locating them at an appropriate distance apart from the centrally support hinge, the gages are very efficient in picking up the acceleration force. A high sensitivity (nominally 0.2 mV/g) yet wide frequency range (nominally resonate at 28 kHz) sensor can be obtained. The etch freed gages enable the accelerometer to stabilize (or warm up) in less than 15 μs after power on. It also has minimal thermal zero shifts of ±6 mV in a wide temperature range from -54 to +100°C. Furthermore, the vertical wall etching capability on (110) silicon allows very narrow gaps between the mass tip and surrounding rim to “stop” the mass tip from traveling too far. These “overrange stops” protect the sensor from excessive g shock. The accelerometer demonstrates survivability under repeated high g shock in excess of 10000 g View full abstract»

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  • Development and characterization of micro-mechanical gratings for optical modulation

    Page(s): 222 - 227
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    Two types of micro-electro-mechanical gratings have been designed for use as optical modulators. The gratings have been fabricated and experimentally characterized, yielding excellent results. Micro-electro-mechanical gratings are possible candidates for applications such as intra-cavity switches for Q-switched lasers, or intensity modulating switches for free-space optical interconnects. Compared to commercially available acousto-optic modulators, micro-electro-mechanical gratings are smaller, weigh less, and can be manufactured in large quantities for a fraction of the cost View full abstract»

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  • Development of mass productive micro stereo lithography (Mass-IH process)

    Page(s): 301 - 306
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    Mass productive 3D micro fabrication process based on micro stereo lithography is proposed and verified experimentally. By using an array of micro optical fibers, a new multi-beam scanning method with high accuracy can be obtained in the whole fabrication area. Since this technique is based on the “IH process” developed (Ikuta et al., MEMS'93, 94), it was named “Mass-IH process”. This process enables us to fabricate MIFS (Micro INtegrated Fluid System) under mass and low cost production similar to silicon process. Future applications of MIFS for Biochemical LSI” and “Biochemical Computer” along with biomedical devices are described View full abstract»

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  • Electrochemical and optical processing of microstructures by scanning probe microscopy (SPM)

    Page(s): 296 - 300
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    Two micro processing techniques based on scanning probe microscopy (SPM) are described. One is electrochemical etching and deposition using a scanning tunneling microscope (STM). STM is very useful tool of nm-scaled observation, and it can be also used as precise positioner in micro processing. In micro electrochemical processing system, a potentiostat for processing is externally attached to STM system, a STM probe was set very closely to a metal substrate in electrolyte solution, and voltage was applied between the substrate and the probe. Then electrochemical reaction occurs in restricted area of the substrate. Therefore, micrometer-size structures are produced by faradic current. A line pattern, which is 200-300 nm in width and 100 nm in depth, was electrochemically etched. When polarity of applied voltage was inverted, a bump pattern, 300 nm in diameter, 200 nm in height, was electrochemically deposited. Another processing method is using a scanning near-field optic/atomic force microscope (SNOAM). The SNOAM provides simultaneous topographic and optical images with high resolution beyond the diffraction limit, better than 100 nm. The optical processing is demonstrated in the photoresist film by the SNOAM. We obtained pit and line patterns down to 100 nm in diameter and width, respectively View full abstract»

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  • Elimination of post-release adhesion in microstructures using thin conformal fluorocarbon films

    Page(s): 55 - 60
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    The adhesion of polysilicon microstructures to their substrates is eliminated using a thin coating of a hydrophobic fluorocarbon film. The film is grown in a plasma reactor in a field-free zone yielding a relatively conformal film growth. Experiments confirm the presence of the film on the surfaces of 100 μm undercuts with contact angles of 110°. The film eliminates the adhesion of polysilicon beams up to 230 μm-long even after direct immersion in water. Initial accelerated aging tests indicate that the film withstands temperatures up to 400°C. Wear test show the film remains effective after 108 contact cycles View full abstract»

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  • Friction and pull-off force on silicon surface modified by FIB

    Page(s): 349 - 353
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    The friction and adhesion forces were measured for silicon surfaces that had various patterns having cyclic asperity. The patterns were created by using a focused ion beam (FIB) to mill ditches and to deposit platinum mounds. To study the effect of cyclic asperity on the forces, the friction and pull-off forces were measured between the pattern and a flat, square scanning probe (0.7×0.7 μm2 ) of an atomic force microscope (AFM). Both the friction and pull-off forces decreased as the asperity increased (i.e., as the ditch depth or mound height increased). The decrease was greater for the cyclic ditches than for the cyclic mounds. The friction force was proportional to the pull-off force, which indicates the importance of reducing the adhesion force when devising lubrication methods for micromachines and micro-electro mechanical systems (MEMS) View full abstract»

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  • Single-crystal silicon actuator arrays for micro manipulation tasks

    Page(s): 7 - 12
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    Arrays of electrostatic MEMS actuators have been fabricated using a modified, multi-layer SCREAM (S_ingle-C_rystal R_eactive E_tching and M_etallization) process. The devices consist of released, torsionally suspended grids with high aspect ratio single-crystal silicon (SCS) tips. They can be used to generate a force field for the manipulation of small, flat objects. Calculations and experiments show that the actuator array is strong enough to move macroscopic parts. An individual actuator can generate a force of approximately 10 μN and a displacement of 5 μm. Monolithic arrays have been built reaching a size of up to 10 cm2 , with up to 15000 individual single-crystal silicon actuators on one chip. We investigate micro actuators for manipulation tasks, and discuss important issues and trade-offs in design, processing and fabrication. We describe manipulation experiments in which small, flat objects where lifted and moved. We conclude with an outlook on applications of programmable actuator arrays to more elaborate micro manipulation tasks and give an outline on how they can be used for transporting, positioning, sorting, and assembly of small parts View full abstract»

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  • A surface-micromachined shear stress imager

    Page(s): 110 - 115
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    A new MEMS shear stress sensor imager has been developed and its capability of imaging surface shear stress distribution has been demonstrated. The imager consists of multi-rows of vacuum-insulated shear stress sensors with a 300 μm pitch. This small spacing allows it to detect surface flow patterns that could not be directly measured before. The high frequency response (30 kHz) of the sensor under constant temperature bias mode also allows it to be used in high Reynolds number turbulent flow studies. The measurement results in a fully developed turbulent flow agree well with the numerical and experimental results previously published View full abstract»

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  • Porous silicon-a new material for MEMS

    Page(s): 1 - 6
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    A technique for the formation of pore arrays with high aspect ratios by electrochemical etching of n-type silicon wafers in hydrofluoric acid is presented. New devices such as a silicon based capacitor or photonic bandgap materials for the infrared regime are fabricated based on this new technology View full abstract»

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