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Microelectromechanical Systems, Journal of

Issue 6 • Date Dec. 2010

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Displaying Results 1 - 25 of 35
  • Table of contents

    Page(s): C1 - C4
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    Freely Available from IEEE
  • Journal of Microelectromechanical Systems publication information

    Page(s): C2
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    Freely Available from IEEE
  • Parylene-Insulated Ultradense Microfabricated Coils

    Page(s): 1277 - 1283
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    This paper details the microfabrication and characterization of electrodeposited coils with high packing density. The process consists of electroplating a first sequence of metal microstructures, followed by conformal insulation of these conductors by a thin vapor-deposited layer of parylene, and subsequent electrodeposited metal filling between the first-layer conductors. Using this approach, the packing density limitation due to photoresist aspect ratio is overcome. The microcoils, which are fabricated onto a dummy substrate, are released and embedded into a parylene layer to reduce parasitic substrate losses at high frequencies, as well as to facilitate the device integration. Comblike test structures were designed and fabricated in order to validate the approach and to explore the electrical properties of such microconductors. Furthermore, ultradense parylene-insulated spiral windings were fabricated and electrically characterized. A large number of turns per volume can be fabricated because of this fabrication approach, which is a requirement for highly efficient small-scale magnetic actuators. Finally, an array of substrateless parylene-coated 2-D coils were built, then folded on top of each other, and electrically connected to form 3-D coil devices. A 14.6-mm-diameter 96-turn three-layer copper winding was fabricated and characterized. The packing density of the 3-D fabricated coil was 81%. View full abstract»

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  • A Cavity Chip Interconnection Technology for Thick MEMS Chip Integration in MEMS-LSI Multichip Module

    Page(s): 1284 - 1291
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    We develop a cavity chip interconnection technology for thick microelectromechanical systems (MEMS) chip integration. The cavity chip comprising Cu through-silicon via and Cu beam-lead wire was fabricated by micromachining processes. The cavity chip could easily connect a thick MEMS chip with a high step height of more than a few hundred micrometers without changing the circuit design of MEMS chip and complicated extra process. Fundamental characteristics are successfully obtained from a pressure-sensing MEMS chip of 360- thickness, where the MEMS chip was connected to a Si substrate by the cavity chip without degrading brittle sensing elements. This interconnection technology would provide a good solution for thick MEMS chip integration with high flexibility. View full abstract»

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  • Evaluation of Oxygen Plasma and UV Ozone Methods for Cleaning of Occluded Areas in MEMS Devices

    Page(s): 1292 - 1298
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    UV ozone and oxygen plasma treatments are two common procedures for cleaning silicon surfaces. The extent to which hidden surfaces of microelectromechanical systems (MEMS) are cleaned by these methods has not been well documented. To probe and compare the effectiveness of the two methods for cleaning occluded regions in MEMS, devices consisting of large movable flaps were fabricated to produce hidden surfaces whose occluded regions exceeded the aspect ratios that typically occur in MEMS devices. The gaps between the flap and the substrate in the custom flap devices were designed to be variable in extent. Their interior regions were initially coated with chemisorbed monolayers and then subjected to cleaning. Both techniques removed monolayers on exposed surfaces and both, to some extent, removed monolayers present on the occluded surfaces. Oxygen plasma was found to be a far more effective method for cleaning the occluded surfaces than the UV ozone method. However, in occlusions with exceptionally large aspect ratios of 1700 : 1, even oxygen plasma could not remove all traces of the chemisorbed monolayers. View full abstract»

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  • Temperature-Dependent Viscoelasticity in Thin Au Films and Consequences for MEMS Devices

    Page(s): 1299 - 1308
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    Thin metal films acting as structural components in microelectromechanical systems (MEMS) devices can exhibit viscoelastic mechanical behavior even at small strains, causing time-dependent changes in device performance. In an effort to characterize the temperature dependence of this behavior, stress relaxation experiments using gas pressure bulge testing have been conducted on 1.0-μm thick Au films at temperatures between 20°C and 80°C. By fitting a Prony series of saturating exponentials to the resulting relaxation curves, a function for the time-dependent elastic modulus was developed for each temperature. The time-dependent elastic moduli were used in an analytical model to demonstrate the impact of viscoelastic stress relaxation on the restoring forces of two different RF MEMS capacitive switch designs. The implications for testing and performance of a cantilever-type contact switch were also assessed. Finally, using time-temperature superposition, a master curve was generated that may enable prediction of room temperature device performance out to times greater than one year. View full abstract»

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  • A Novel Method for In Situ Uniaxial Tests at the Micro/Nano Scale—Part I: Theory

    Page(s): 1309 - 1321
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    A novel MEMS-based uniaxial testing apparatus and a specimen design are presented for measuring the mechanical response of material samples in situ in scanning electron microscope (SEM). The stage adopts an assembly approach, where specimens are fabricated independently, allowing testing of a variety of materials. The assembly approach, however, involves intrinsic challenges in achieving pure uniaxial loading at the micro/nanoscale due to off-axis loading (misalignment) errors. The effect of misalignment in stress evaluation increases with decreasing size scale of the sample-an issue that has received limited attention in the literature. Here, the source of intrinsic misalignment and its influence on the stress nonuniformity are explored analytically and numerically. This paper reveals substantial bending of the microspecimen due to small and often unavoidable off-axis loading. The proposed stage and the specimen ensure uniaxial loading by introducing hingelike self-aligning mechanisms both in the stage as well as in the specimen. The analysis offers the parameter space to design and optimize uniaxial tests at the micro/nanoscale. View full abstract»

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  • A Novel Method for In Situ Uniaxial Tests at the Micro/Nanoscale—Part II: Experiment

    Page(s): 1322 - 1330
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    Here, we experimentally investigate the sources of misalignment during uniaxial test and their substantial influence on mechanical measurement of microspecimens. To avoid possible misalignment errors, we propose a novel MEMS-based uniaxial testing stage and a specimen design for measuring the mechanical response of material samples in situ in scanning electron microscope (SEM). The proposed stage and the specimen ensure uniaxiality of loading due to the introduction of hingelike self-aligning mechanisms both in the stage and in the specimen. Using the stage and the sample, we measure the elastic modulus of single-crystal silicon (SCS) within 99.5% of the known value. We also experimentally demonstrate that the bending strain due to any misalignment can be limited to within 1% of the average strain by using the proposed stage and specimen. View full abstract»

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  • Modeling of Front-Etched Micromachined Thermopile IR Detector by CMOS Technology

    Page(s): 1331 - 1340
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    CMOS-compatible thermopile detectors are widely used for IR detection. In this paper, an analytical model is developed for front-etched thermopile IR detectors using CMOS technology. By dividing the front-etched microbridge thermopile detector into cantilever thermocouple detectors with separate absorber areas, the thermal gradient in each zone of the single thermocouple IR detector (absorber and thermocouple transducer) is analyzed using 1-D method. During thermal gradient modeling, the IR absorption of dielectric layers in the thermocouple area is also considered. The thermopile IR detector performance is then calculated by adding the temperature differences of each single thermocouple IR detector. The developed analytical model has been verified by comparing simulations with experiments. The simulation results closely agree with the measured results. For optimizing the geometry of the front-etched thermopile IR detector, a quantitative study of the detector performance is conducted with respect to the absorber width, polysilicon length, polysilicon width, and etching window width. View full abstract»

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  • Encapsulation of Capacitive Micromachined Ultrasonic Transducers Using Viscoelastic Polymer

    Page(s): 1341 - 1351
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    The packaging of a medical imaging or therapeutic ultrasound transducer should provide protective insulation while maintaining high performance. For a capacitive micromachined ultrasonic transducer (CMUT), an ideal encapsulation coating would therefore require a limited and predictable change on the static operation point and the dynamic performance, while insulating the high dc and dc actuation voltages from the environment. To fulfill these requirements, viscoelastic materials, such as polydimethylsiloxane (PDMS), were investigated for an encapsulation material. In addition, PDMS, with a glass-transition temperature below room temperature, provides a low Young's modulus that preserves the static behavior; at higher frequencies for ultrasonic operation, this material becomes stiffer and acoustically matches to water. In this paper, we demonstrate the modeling and implementation of the viscoelastic polymer as the encapsulation material. We introduce a finite element model (FEM) that addresses viscoelasticity. This enables us to correctly calculate both the static operation point and the dynamic behavior of the CMUT. CMUTs designed for medical imaging and therapeutic ultrasound were fabricated and encapsulated. Static and dynamic measurements were used to verify the FEM and show excellent agreement. This paper will help in the design process for optimizing the static and the dynamic behavior of viscoelastic-polymer-coated CMUTs. View full abstract»

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  • Parylene-Based Electrochemical-MEMS Transducers

    Page(s): 1352 - 1361
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    We report the design, fabrication, and characterization of electrochemical microelectromechanical systems (EC-MEMS) devices featuring encapsulated fluid as the basis for transduction. Parylene microstructures, including discrete chambers (square or circular geometry), are utilized as physical transducers for electrochemically mediated liquid impedance transduction of physical phenomenon such as contact and force. Parylene-based EC-MEMS technologies uniquely leverage advantages in size (<; 500 μm diameter), packaging (no hermetic packaging necessary), power (nanowatts to microwatts), and flexibility to address the physical sensing requirements of in vivo applications. Robust EC impedance (EI) sensor responses (up to 20% from base-line) and discrimination of 200-nm chamber deflections were possible using the EI transduction technique. Additional transducer configurations enabling electrolysis-based out-of-plane actuation and biomimetic mechanotransduction in microfluidic channels are also presented. View full abstract»

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  • Large-Scale Silicone-Rubber-Based Optical Interconnect Packaged With FR4

    Page(s): 1362 - 1369
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1102 KB) |  | HTML iconHTML  

    Polydimethylsiloxane (PDMS)-based large-scale electrical-optical circuit boards (EOCBs) have been developed based on a combination of a large-scale PDMS waveguide fabrication technique and a process for efficient interfacial bonding between PDMS optical layers and standard FR4 (fiberglass-reinforced epoxy and grade 4 on flame retardance) printed circuit board materials using a specially developed surface adhesion promoter (SAP). The main mechanism of forming a good bonding between PDMS and FR4 has been identified. The optical properties of the PDMS waveguide layer remained unchanged by the addition of the SAP. According to the defined test procedures from the Institute of Printed Circuits, the International Electro Technical Commission, and Telcordia, the environmental stability of packaged EOCBs has been tested with the result that they exhibited excellent mechanical, optical, and thermal stabilities. The mechanical stability limit of the tested EOCBs is determined only by the intrinsic mechanical stability of the used PDMS materials. The optical waveguide propagation loss at 850 nm is less than 0.1 dB/cm after surviving from the defined environmental test procedures. View full abstract»

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  • A Piezoelectric-Driven Three-Dimensional MEMS VOA Using Attenuation Mechanism With Combination of Rotational and Translational Effects

    Page(s): 1370 - 1379
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    A gold-coated silicon mirror (5 mm 5 mm) actuated by piezoelectric (PZT) cantilever beams has been investigated for variable optical attenuator applications. The device is micromachined from a SOI substrate with a 5 μm thick Si device layer, with multilayers of Pt/Ti/PZT/Pt/Ti deposited as electrode materials. A large Si mirror plate and 110 arrayed PZT cantilevers arranged in parallel are formed after the release process. The ten cantilevers are designed to be electrically isolated from one another. A dual-core fiber collimator is aligned perpendicularly to the mirror in a 3-D light attenuation arrangement. Thus, three modes of attenuation mechanisms were investigated based on rotational and translational effects. A dynamic attenuation range of 40 dB is achieved at 1 V and 1.8 V for bending and torsional mode, respectively. View full abstract»

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  • Linear High-Resolution BioMEMS Force Sensors With Large Measurement Range

    Page(s): 1380 - 1389
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    We present a set of displacement-based high-resolution (50 pN) micromechanical force sensors with a large force measurement range (1 μN). Typically, force sensors that have high resolution have a limited force measurement range and vice versa. The force sensors presented here overcome this limitation and, in addition, have a highly linear force-displacement response. The sensors (≈3 mm × 4 mm × 150 m)are composed of a series of flexible beams attached to a rigid probe that deform when subjected to an external force. The force is obtained by optically measuring the displacement of the probe with respect to a fixed reference beam. The force sensors are fabricated using a simple two-mask process that allows for their stiffness to be varied over a wide range. Furthermore, we have developed a novel scheme to avoid capillary forces during the immersion and removal of these sensors from aqueous environments, which makes them highly suited for biological studies. We illustrate the capability and versatility of these sensors by measuring the in vivo force-deformation response of axons in Drosophila melanogaster (fruit fly). View full abstract»

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  • Drug Particle Delivery Investigation Through a Valveless Micropump

    Page(s): 1390 - 1399
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    Micropumps with various types of actuations are being used in microfluidic transport for liquid drug delivery. Due to the complexity of the flow field, particle transport through a valveless micropump might be challenging in comparison to a pressure-driven flow micropumps. In order to better understand and develop an optimized design for the delivery of drug particles through valveless micropumps, computational simulations may be necessary. In this paper, the transport of drug particles through the valveless micropump is simulated through 3-D computational fluid dynamics combined with discrete particle transport methods. After computational validation, the effects of actuation frequency, particle size, and transporting style on the particle transport are investigated. Both the actuation frequency and transporting pattern have a strong relationship in terms of resident times and the spatial distribution of the transported particles through the designed micropump. The computational analysis results presented demonstrate that it is possible to optimize the proposed valveless micropump design through numerical simulations for specific delivery of drug particles. View full abstract»

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  • Bioinspired 3-D Tactile Sensor for Minimally Invasive Surgery

    Page(s): 1400 - 1408
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    This paper reports the development of a bioinspired 3-D tactile sensor for minimally invasive surgery. Inspired by the principle of hair cells, the sensor is composed of a central silicon post and a piezoresistor-embedded polyimide diaphragm to which the silicon post is attached. The high-aspect-ratio silicon post helps to increase the sensitivity to shear force significantly. Another unique advantage is that the silicon post is surrounded by a cylindrical cavity that provides a safety stop for the excessively large force/displacement. A fabrication process using deep reactive-ion etching, as well as a simple but effective packaging scheme, was demonstrated. The packaged tactile sensor was characterized by monitoring the resistance change of the piezoresistors when the central post was pushed in different directions. The sensor exhibited a shear force sensitivity of 10.8 N-1 and a normal force sensitivity of 3.5 N-1. The measured displacement sensitivities in shear and normal directions are 1.2 × 10-3 and 6.0 × 10-3, respectively. The responses of single and multiple sensors to the rubber scratching test were studied to demonstrate the capability of the sensor to detect the direction and other information of the scratching. View full abstract»

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  • An Ultra Compact Integrated Front End for Wireless Neural Recording Microsystems

    Page(s): 1409 - 1421
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    Abstract-The design and performance of an integrated front end for high-channel-count neural recording microsystems is presented. This front end consists of a 3-D micromachined microelectrode array, realized using a new architecture that allows simple and rapid microassembly. A 64-site 3-D multiprobe, realized using the new architecture, interfaces with tissue volumes of less than 0.01 mm3 and has a footprint of 1 mm2. For amplification, filtering, and buffering of the recorded neural signals, a custom signal-conditioning circuit provides high gain (60 dB), low noise (4.8 μVrms), and low power (50 μW) in an area of 0.098 mm2. In addition, this circuitry implements bandwidth tuning, offset compensation, and wireless gain programmability. This new approach to system integration uses a microfabricated parylene overlay cable to electrically interconnect the 3-D array and signal-conditioning circuitry. In vivo results obtained using this integrated microsystem front end in its most compact form are presented. View full abstract»

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  • Low-Power High-Speed Electromagnetic Flapping Shutters Using Trapezoidal Shutter Blades Suspended by H-Type Torsional Springs

    Page(s): 1422 - 1429
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    We present small-size, low-power, and high-speed electromagnetic flapping shutters composed of trapezoidal twin blades suspended by H-type torsional springs for phone camera applications. The previous electrostatic rolling and flapping shutters need high input voltage, while the previous electromagnetic rotating shutters are too large to use in phone cameras. For low-power and high-speed angle motion in the small size available on phone cameras, the present electromagnetic flapping shutters are designed to use the low-inertia trapezoidal twin blades, each suspended by the low-stiffness H-type torsional springs. The size of the only shutter device is , and the total size of the shutter system, including two permanent magnets (NdFeB), is . In the experimental study, the electromagnetic flapping shutters generate the steady-state rotational angles of and in the magnetic fields of 0.15 and 0.30 T, respectively, for the input current of 60 mA, while achieving the maximum overshoot angles of and in the magnetic fields of 0.15 and 0.30 T, respectively. The electromagnetic flapping shutters show the rising/settling times of 1.0 ms/20.0 ms for opening and 1.7 ms/10.3 ms for closing. The life time and light-blocking rate of the shutters are measured to be cycles and 80.7%, respectively. Therefore, we experimentally demonstrated that the small-size , low-power (≤ 60 mA), and high-speed (~1/370 s) electromagnetic flapping shutters are suitable for phone camera applications. View full abstract»

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  • MEMS-Based Nanospray-Ionization Mass Spectrometer

    Page(s): 1430 - 1443
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    An electrospray-ionization mass spectrometer (ESI-MS) whose main components are all fabricated using silicon microelectromechanical systems (MEMS) techniques is demonstrated for the first time. The ion source consists of a microengineered alignment bench containing a V-groove mounting for a nanospray capillary, an ion-extraction electrode, and a pneumatic nebulizer. The vacuum interface consists of two plates, each carrying a 50-μm-diameter capillary, that are selectively etched and bonded together to provide a differentially pumped internal cavity. The quadrupole filter consists of a microfabricated frame that provides mountings for stainless-steel rods measuring 650 μm in diameter and 30 mm in length. Two different quadrupoles are compared: a first-generation bonded silicon device and a second-generation silicon-on-glass device with a Brubaker prefilter. Differential pumping of a MEMS component is demonstrated for the first time, atmospheric pressure ionization and ion transfer into vacuum are characterized, ESI-MS operation is demonstrated, and spectra are presented for a variety of compounds. View full abstract»

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  • Thermally Tunable Polymer Microlenses for Biological Imaging

    Page(s): 1444 - 1449
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    We present polydimethylsiloxane (PDMS) microlenses capable of thermally tuning their focal lengths via optically transparent indium tin oxide (ITO) microheaters. Microlenses with various diameters are created by molding PDMS over microstructures of reflowed photoresist. Due to a relatively large thermal expansion coefficient, these PDMS microlenses exhibit measurable thermal expansion with relatively small temperature changes. By adjusting the temperature of the microlenses using ITO microheaters, we can actively control their radii of curvature and focal lengths without requiring moving mechanical components. To demonstrate the tunability of the microlenses, we characterize temperature-dependent changes by focal length and magnification factor measurements. We also investigate the ability to use the microlenses for tunable observation of cells, demonstrating their potential application to biological imaging. View full abstract»

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  • A Tip-Tilt-Piston Micromirror Array for Optical Phased Array Applications

    Page(s): 1450 - 1461
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    A tip-tilt-piston micromirror array based on electrothermal bimorph actuation is presented. The micromirror uses a compactly folded actuator design that can realize high fill-factor with a simple fabrication process. A 4 × 4 micromirror array with sub-apertures of 0.9 mm and a fill-factor of 54% is demonstrated. A piston actuation of about 200 μm and tip-tilt scanning of ±18° optical angles are obtained at a driving voltage as small as 4.5 Vdc. The mirror's tip-tilt steering capability and piston control make it promising for optical phased array applications. The phased array concept is demonstrated by phasing two adjacent mirrors on the mirror array. Other device characterizations including frequency, transient response, and mirror surface quality are also reported. View full abstract»

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  • High-Pressure Peristaltic Membrane Micropump With Temperature Control

    Page(s): 1462 - 1469
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    A high-pressure peristaltic membrane micropump, which is capable of pumping against a back pressure of 150 bar, has been evaluated. The main focus was to maintain the flow characteristics also at high back pressures. The pump was manufactured by fusion bonding of parylene-coated stainless-steel stencils. A large-volume expansion connected to the solid-to-liquid phase transition in paraffin was used to move 10-μm-thick stainless-steel membranes. The pump was evaluated by using two different driving schemes, a four-phase cycle and a six-phase cycle. With the six-phase cycle, a constant flow rate of 0.4 μL min-1 was achieved over an interval ranging from atmospheric pressure to 130 bar. At lower back pressures, the more energy efficient four-phase cycle achieved slightly higher flow rates than the six-phase cycle. However, it required higher driving voltage at high back pressures. Since the pump is thermally activated, a temperature sensor was integrated to control the melting and solidification of paraffin, implying capability of increasing the performance of the pump. With a thickness of only 1 mm as well as a simple and robust design, the micropump is well suited for integration in analytical systems. The high pressures managed are in the region needed for, e.g., high-performance liquid chromatography systems. View full abstract»

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  • Design and Fabrication of a High-Power Eyeball-Like Microactuator Using a Symmetric Piezoelectric Pusher Element

    Page(s): 1470 - 1476
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    A novel multidegree-of-freedom (MDOF) eyeball-like microactuator was developed using a symmetric piezoelectric plate and an Ni-Co alloy micropusher element. A LIGA-like technique was employed to manufacture an Ni-Co alloy micropusher with a Vickers hardness value of 550, which was then attached at the midpoint of the long side of a piezoelectric plate with dual electrodes to construct a symmetric piezoelectric pusher element (SPPE). The research integrated the concept of LEGO bricks, and three different vibration modes of the SPPE were designed to develop a high-power MDOF motion platform, which was able to rotate a spherical charge-coupled device (CCD) along three perpendicular axes. This MDOF eyeball-like microactuator consisted of a stator and a rotor: The stator was created from two mutually orthogonal sets of parallel SPPEs to form an MDOF motion platform, and the rotor was a spherical CCD. The experiment demonstrated high-power MDOF eyeball-like microactuator working frequencies along the X-, Y-, and .Z-axes to be 223.4, 223.2, and 225 kHz and the rotation speeds to reach 50, 52, and 180 r/min, respectively, at a driving voltage of 30 Vpp. The volume ratio of rotor to stator was 20.32, and this design can therefore drive a rotor of a volume greater than ten times that of the stator. In addition, the driving voltage was proportional to the rotation speed; hence, when the rotor diameter was increased or the spherical rotor weight reduced, the rotation speed increased. In the future, this MODF eyeball-like microactuator may be used for a number of applications, such as sun-tracking systems for green-energy harvesters and eyeball-like devices for use in the biomedical field. View full abstract»

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  • An Optofluidic Concept for a Tunable Micro-iris

    Page(s): 1477 - 1484
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    A tunable aperture stop based on optofluidic technology, which overcomes a number of limitations of comparable micromechanical alternatives, is presented. Relying on the high optical absorption of aqueous pigment dispersions, we demonstrate that optical stops of high contrast may be defined without the need for any movable parts. The highly flexible design is based on photolithographic patterning of dry film resist and allows control of laminar flow in microfluidic chambers exclusively by capillary forces. The functionality of the developed device is shown in transmission measurements and by application of the iris in a basic imaging setup. View full abstract»

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  • Vortex Anemometer Using MEMS Cantilever Sensor

    Page(s): 1485 - 1489
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (577 KB) |  | HTML iconHTML  

    This paper presents construction and performance of a novel hybrid microelectromechanical system (MEMS) vortex flowmeter. A miniature cantilever MEMS displacement sensor was used to detect frequency of vortices development. 3-mm-long silicon cantilever, protruding directly out of a trailing edge of a trapezoidal glass-epoxy composite bluff body was put into oscillatory motion by vortices shed alternately from side surfaces of the obstacle. Verified linear measurement range of the device extended from 5 to 22 m/s; however, it could be broadened in absence of external 50-Hz mains electrical interfering signal which required bandpass frequency-domain digital sensor signal processing. The MEMS vortex sensor proved its effectiveness in detection of semilaminar airflow velocity distribution in a 40-mm-diameter tubular pipe. View full abstract»

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Aims & Scope

The topics of interest include, but are not limited to: devices ranging in size from microns to millimeters, IC-compatible fabrication techniques, other fabrication techniques, measurement of micro phenomena, theoretical results, new materials and designs, micro actuators, micro robots, micro batteries, bearings, wear, reliability, electrical interconnections, micro telemanipulation, and standards appropriate to MEMS. Application examples and application oriented devices in fluidics, optics, bio-medical engineering, etc., are also of central interest.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Christofer Hierold
ETH Zürich, Micro and Nanosystems