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Microelectromechanical Systems, Journal of

Issue 2 • Date April 2006

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Displaying Results 1 - 21 of 21
  • Table of contents

    Page(s): c1 - c4
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  • Journal of Microelectromechanical Systems publication information

    Page(s): c2
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  • Microoptical characterization of piezoelectric vibratory microinjections in drosophila embryos for genome-wide RNAi screen

    Page(s): 277 - 286
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    In this paper, we study the effect of acoustic agitation on the penetration force for microinjections in Drosophila embryos for genome-wide RNA interference (RNAi) screens, using an integrated optical MEMS force encoder for in vivo characterization of the dynamic penetration forces. Two modes of operation are investigated. In the first mode of operation, the injector is brought into contact and acts on the embryo with a fixed force, and the vibration amplitude of the microinjector is increased till penetration occur. We observed a linear decrease in the penetration force of 1.6 μN with every 0.1 m/s tip velocity increase. In the second mode of operation, the vibration amplitude is kept constant and the injector is pushed into the embryo until penetration. We simulate the optical force encoder eigenmodes and measure the injection force over the frequency range from 0 to 16 kHz with actuation voltages up to 150V. Among the eight encoder eigenmodes with resonant frequency up to 16 kHz, the longitudinal vibration along the injector is shown to dominate the force reduction at 14 kHz. Two other modes, both involving significant out-of-plane injector motion, reduce the penetration force by 52% around 3.1 kHz. The average penetration force is calculated based on injections into multiple embryos for each experimental condition. For each microinjection, the peak (or average) penetration force can be derived from the peak (or average) relative displacement of the two gratings upon penetration. The achieved minimum peak penetration force was 15.6 μN (∼29.7% of the static penetration force), while the minimum average penetration force was 2.7 μN (5.1% of the static penetration force). View full abstract»

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  • Development of microfluidic device for electrical/physical characterization of single cell

    Page(s): 287 - 295
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    A novel device with microchannels for flowing cells and twin microcantilever arrays for measuring the electrical impedance of a single cell is proposed. The fabrication process is demonstrated and the twin microcantilever arrays have been successfully fabricated. In our research, we measured the electrical impedance for normal and abnormal red blood cell over the frequency range from 1 Hz to 10 MHz. From the electrical impedance experiment of normal and abnormal red blood cell, it was examined that the electrical impedance between normal and abnormal red blood cells was significantly different in magnitude and phase shift. In this paper, we show that the normal cell can be taken apart from the abnormal cell by electrical impedance measurement. Therefore, it is expected that the applicability of this technology can be used in cellular studies such as cell sorting, counting or membrane biophysical characterization. View full abstract»

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  • A capillary system with thermal-bubble-actuated 1×N microfluidic switches via time-sequence power control for continuous liquid handling

    Page(s): 296 - 307
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    A novel thermal-bubble-actuated 1×N microfluidic switch without the need of external pumps has been successfully fabricated using micromachining process and demonstrated. This device is a valveless switch by means of the triggering thermal-bubble-actuator, the capillary force, the design of the distributed hydrophobic patches in the microchannels, and the time-sequence power control. The switch mechanism among different microchannels in our device is dominated by controlling the format and timing of power input that generates actuating thermal bubbles. The experimental results successfully and robustly demonstrate the switch function of our microcapillary systems to switch continuous liquid into desired outlet ports based on our hydrophobic-patch design and programmable time-sequence bubble actuation. In this paper, we describe the theory, design, synthesis, micromachining process, control circuitry, and its time-sequence control, as well as the experimental demonstration of this microcapillary system. View full abstract»

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  • Silicon-on-insulator microfluidic device with monolithic sensor integration for μTAS applications

    Page(s): 308 - 313
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    A novel concept for the integration of liquid phase charge sensors into microfluidic devices based on silicon-on-insulator (SOI) technology is reported. Utilizing standard silicon processing we fabricated basic microfluidic cross geometries comprising of 5-10-mm-long and 55-μm-wide channels of 3 μm depth by wet sacrificial etching of the buried oxide of an SOI substrate. To demonstrate the feasibility of fluid manipulation along the channel we performed electroosmotic pumping of a dye-labeled buffer solution. At selected positions along the channel we patterned the 205-nm thin top silicon layer into freely suspended, 10-μm wide bars bridging the channel. We demonstrate how these monolithically integrated bars work as thin-film resistors that sensitively probe changes of the surface potential via the field effect. In this way, a combination of electrokinetic manipulation and separation of charged analytes together with an on-chip electronic detection can provide a new basis for the label-free analysis of, for example, biomolecular species as envisaged in the concept of micrototal analysis systems (μTAS) or Lab-on-Chip (LOC). View full abstract»

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  • Spatially resolved temperature mapping of electrothermal actuators by surface Raman scattering

    Page(s): 314 - 321
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    In this paper, we report spatially resolved temperature profiles along the legs of working V-shaped electrothermal (ET) actuators using a surface Raman scattering technique. The Raman probe provides nonperturbing optical data with a spatial resolution of 1.2 μm, which is required to observe the 3-μm-wide actuator beams. A detailed uncertainty analysis reveals that our Raman thermometry of polycrystalline silicon is performed with fidelity of ±10 to 11 K when the peak location of the Stokes-shifted optical phonon signature is used as an indicator of temperature. This level of uncertainty is sufficient for temperature mapping of many working thermal MEMS devices which exhibit characteristic temperature differences of several hundred Kelvins. To our knowledge, these are the first quantitative and spatially resolved temperature data available for thermal actuator structures. This new temperature data set can be used for validation of actuator thermal design models and these new results are compared with finite-difference simulations of actuator thermal performance. View full abstract»

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  • Microfabrication and characterization of metal-embedded thin-film thermomechanical microsensors for applications in hostile manufacturing environments

    Page(s): 322 - 329
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    Effective monitoring and diagnosis of manufacturing processes is of critical importance. If critical manufacturing process conditions are continuously monitored, problems can be detected and solved during the processing cycle. However, current technology still evidently lags behind practical needs. Microfabricated thin-film thermocouples and strain gauges are attractive for their small size and fast response. It is challenging to fabricate and embed these sensors into metallic components that are widely used in manufacturing. This paper investigates the fabrication, embedding, and characterization of metal embedded thin-film thermocouples and strain gauges. The materials (dielectric and metallic) constituting a complete microsensor were characterized and optimized. The results obtained from characterization and optimization of materials are presented and discussed. Thin-film thermocouples on stainless steel substrates (before and after embedding) were calibrated to elevated temperatures. The behavior of thin-film strain gauges was also studied. The metal embedded sensors demonstrated good accuracy, sensitivity, and linearity that matched the performance of commercial thermocouples and strain gauges well. The metal embedded microsensors are promising for in situ monitoring in hostile manufacturing environments. View full abstract»

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  • Magnetic composite electroplating for depositing micromagnets

    Page(s): 330 - 337
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    This paper reports a novel magnetic composite materials deposition technique called magnetic composite electroplating (MCE). Thin films and micromagnets arrays of a composite matrix consisting of magnetic particles and a ferromagnetic alloy have been fabricated based on this technique. In a typical MCE process, magnetic particles are electrochemically and mechanically embedded into electroplated ferromagnetic thin films to form a magnetic particle-alloy composite. The magnetic particle selected is a barium ferrite magnet (BaFe12O19) and the ferromagnetic matrix is a pulse-reverse electroplated CoNiP alloy. The particle embedded fraction (w.t. %) directly affects magnetic properties and is experimentally determined by its energy dispersive spectrum (EDS). Various factors including electrolyte particle concentration, applied current, electrolyte pH, and the presence of cationic surfactants affecting the particle embedded fraction are experimentally investigated. Arrays of BaFe12O19-CoNiP magnets with a variety of dimensions and features as small as 8μm have been realized by MCE. Experimental analysis shows that the composite exhibits magnetic properties, such as a high coercivity (Hc) of up to 1.75×105 A/m, particularly well suited for MEMS actuators. View full abstract»

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  • Thermal annealing in hydrogen for 3-D profile transformation on silicon-on-insulator and sidewall roughness reduction

    Page(s): 338 - 343
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    A fast, effective process using hydrogen annealing is introduced to perform profile transformation on silicon-on-insulator (SOI) and to reduce sidewall roughness on silicon surfaces. By controlling the dimensions of as-etched structures, microspheres with 1 μm radii, submicron wires with 0.5 μm radii, and a microdisk toroid with 0.2 μm toroidal radius have been successfully demonstrated on SOI substrates. Utilizing this technique, we also observe the root-mean-square (rms) sidewall roughness dramatically reduced from 20 to 0.26 nm. A theoretical model is presented to analyze the profile transformation, and experimental results show this process can be engineered by several parameters including temperature, pressure, and time. View full abstract»

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  • Pneumatic microactuator powered by the deflagration of sodium azide

    Page(s): 344 - 354
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    This paper details the design, simulation, fabrication, and characterization of two pneumatic microactuators powered by sodium azide or an external pressure source. One was fabricated using traditional manufacturing, while the other used microfabrication techniques. To characterize force output, a microforce gage was also designed, built, and characterized since commercial devices were not available. The azide-based microactuator was successfully actuated numerous times and simulations were then used to predict model characteristics based on system identification techniques. Forces as high as 65 mN and as low as sub milli-Newton were recorded, and displacements in the multi millimeter range were observed. Both the force and displacement magnitudes are in fact limited by the material properties, design geometry, and amount of azide deflagrated. It was demonstrated that a microactuator powered by sodium azide can provide both large forces and displacements simultaneously with the potential of using a small amount of electrical power. No tradeoffs had to be made between force outputs and displacement strokes, as is common to other microactuators. Since only a small amount of electrical power should be necessary in a properly designed battery powered device, the microactuator is poised to be mobile and independent of external power sources. View full abstract»

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  • Complex nonlinear oscillations in electrostatically actuated microstructures

    Page(s): 355 - 369
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    In this paper, new nonlinear dynamic properties of electrostatically actuated microstructures [referred to as electrostatic microelectromechanical systems (MEMS)] observed under superharmonic excitations are presented using numerical simulations. Application of a large dc bias (close to the pull-in voltage of the device) is found to bring the device to a nonlinear state. This nonlinear state (referred to as "dc-symmetry breaking") can be clearly observed from the characteristic change in the phase-plot of the device. Once a steady nonlinear state is reached, application of an ac signal at the Mth superharmonic frequency with an amplitude around "ac-symmetry breaking" gives rise to M oscillations per period or M-cycles in the MEM device. "ac-symmetry breaking" can also be observed by a characteristic change in the phase-plot of the device. On further increasing the ac voltage, a period doubling sequence takes place resulting in the formation of 2nM-cycles in the system at the Mth superharmonic frequency. An interesting chaotic transition (banded chaos) is observed during the period doubling bifurcations. The nonlinear nature of the electrostatic force acting on the MEM device is found to be responsible for the reported observations. The significance of the mechanical and the fluidic nonlinearities is also studied. View full abstract»

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  • Piezoelectric unimorph microactuator arrays for single-crystal silicon continuous-membrane deformable mirror

    Page(s): 370 - 379
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    Micromachined deformable mirror technology can boost the imaging performance of an otherwise nonrigid, lower-quality telescope structure. This paper describes the optimization of lead zirconium titanate (PZT) unimorph membrane microactuators for deformable mirrors. PZT unimorph actuators consisting of a variety of electrode designs, silicon-membrane thickness, and membrane sizes were fabricated and characterized. A mathematical model was developed to accurately simulate the membrane microactuator performance and to aid in the optimization of membrane thicknesses and electrode geometries. Excellent agreement was obtained between the model and the experimental results. Using the above approach, we have successfully demonstrated a 2.5-mm-diameter PZT unimorph actuator. A measured deflection of 5 μm was obtained for 50 V applied voltage. Complete deformable mirror structures consisting of 10-μm-thick single-crystal silicon mirror membranes mounted over the aforementioned 4×4 4 PZT unimorph membrane microactuator arrays were designed, fabricated, assembled, and optically characterized. The fully assembled deformable mirror showed an individual pixel stroke of 2.5 μm at 50 V actuation voltage. The deformable mirror has a resonance frequency of 42 kHz and an influence function of approximately 25%. View full abstract»

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  • Inherently robust micromachined gyroscopes with 2-DOF sense-mode oscillator

    Page(s): 380 - 387
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    Commercialization of reliable vibratory micromachined gyroscopes for high-volume applications has proven to be extremely challenging, primarily due to the high sensitivity of the dynamical system response to fabrication and environmental variations. This paper reports a novel micromachined gyroscope with two degrees-of-freedom (DOF) sense-mode oscillator that provides inherent robustness against structural parameter variations. The 2-DOF sense-mode oscillator provides a frequency response with two resonant peaks and a flat region between the peaks, instead of a single resonance peak as in conventional gyroscopes. The device is nominally operated in the flat region of the sense-mode response curve, where the amplitude and phase of the response are insensitive to parameter fluctuations. Furthermore, the sensitivity is improved by utilizing dynamical amplification of oscillations in the 2-DOF sense-mode oscillator. Thus, improved robustness to variations in temperature, damping, and structural parameters is achieved, solely by the mechanical system design. Prototype gyroscopes were fabricated using a bulk-micromachining process, and the performance and robustness of the devices have been experimentally evaluated. With a 25 V dc bias and 3 V ac drive signal resulting in 5.8 μm drive-mode amplitude, the gyroscope exhibited a measured noise-floor of 0.64°/s/√Hz over 50 Hz bandwidth in atmospheric pressure. The sense-mode response in the flat operating region was also experimentally demonstrated to be inherently insensitive to pressure, temperature, and dc bias variations. View full abstract»

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  • Grating-assisted optical microprobing of in-plane and out-of-plane displacements of microelectromechanical devices

    Page(s): 388 - 395
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    In this paper, we present an optical sensing method that is capable of detection of both in-plane and out-of-plane translational motions of a micromachined structure that incorporates a diffraction grating. In the proposed method, the out-of-plane displacement sensing is based on optical intensity modulation of a phase-sensitive diffraction grating, while the in-plane displacement sensing is based on a modified grating interferometry. Preliminary experimental results on a surface micromachined grating structure fabricated within the shuttle of a comb-drive resonator demonstrate an in-plane resolution of 0.23 nm/√Hz and an out-of-plane resolution of 0.03 nm/√Hz in a 1 Hz bandwidth centered at 950 Hz. The proposed method can be configured for many promising applications, including optically interrogated high sensitive single/dual-axis microaccelerometers or gyroscopes. View full abstract»

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  • A novel method for measuring the strength of microbeams

    Page(s): 396 - 405
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    A novel method and test structure for measuring the strength of brittle microbeams is presented. The method does not require any measurement of forces or displacements. The test structure includes a microbeam that is wrapped over a curved side-wall by application of an unmeasured force. With the progression of wrapping, increasing tensile stresses are induced in the microbeam. When sufficiently high stresses are induced, the beam breaks. The failure stress is deduced by measuring the length of the remaining ligament of the broken beam. The method is demonstrated by measuring the strength of microbeams in bulk-micromachined test structures. View full abstract»

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  • Magnetic induction machines integrated into bulk-micromachined silicon

    Page(s): 406 - 414
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    This paper presents the design, fabrication, and characterization of laminated, magnetic induction machines intended for high-speed, high-temperature, high-power-density, silicon-based microengine power generation systems. Innovative fabrication techniques were used to embed electroplated materials (Cu, Ni80Fe20, Co65Fe18Ni17) within bulk-micromachined and fusion-bonded silicon to form the machine structures. The induction machines were characterized in motoring mode using tethered rotors, and exhibited a maximum measured torque of 2.5 μN·m. View full abstract»

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  • Magnetic induction micromachine-part I: Design and analysis

    Page(s): 415 - 426
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    Most microscale electric and magnetic machines studied in the last decade lack the power density to support many practical applications. This paper introduces a design for a magnetic induction machine that offers power densities in excess of 200 MW/m3 and efficiencies of up to 50%, while providing more than 10 W of mechanical power. This is a substantial performance increase in MEMS electromagnetic machines studied to date. View full abstract»

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  • Magnetic induction micromachine-part II: fabrication and testing

    Page(s): 427 - 439
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    This paper presents the realization of a magnetic induction machine. The development of this machine is part of an ongoing project to create high-power density electric microgenerators for use in portable-power applications. The results reported here focus on testing a first-generation nonlaminated electromagnetic actuator, a metrology device designed for exploring and characterizing the fabrication process and the operating behavior of the magnetic induction micromachine. Achieving high power density requires large electrical currents and magnetic fluxes, which necessitate thick, multilayered microstructures that are difficult to fabricate. The batch-fabrication schemes developed as part of this work are based on low-temperature micromolding that makes extensive use of various ultra-thick photoresists and electroplating of electrical conductors (Cu) and ferromagnetic materials (Ni-Fe 80%-20%), resulting in the successful fabrication of a multilayer two-phase planar stator and a planar rotor. To evaluate the performance of the complete machine (stator plus rotor), a 4-mm-diameter, 500-μm-thick electroplated Ni-Fe rotor is tethered to a series of flexible structures that prevent it from making a complete revolution, but allow accurate torque performance extraction. The tethered induction micromotor studied here exhibits torque production as high as 4.8 μN·m. View full abstract»

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  • Magnetic induction micromachine-part III:Eddy currents and nonlinear effects

    Page(s): 440 - 456
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    The magnetic induction micromachine fabricated in Part II was not laminated, as designed in Part I. Consequently, eddy currents in the stator core, and the associated nonlinear saturation, significantly decreased its performance from that predicted in Part I. To investigate and explain these phenomena and their consequences, this paper models the behavior of the solid-stator-core machine fabricated in Part II using a finite-difference time-domain numerical analysis. The inherent stiffness in the time-domain integration of Maxwell's equations is mitigated via reducing the speed of light artificially by five orders of magnitude, while taking special care that assumptions of magneto-quasi-static behavior are still met. The results from this model are in very good agreement with experimental data from the tethered magnetic induction micro motor. View full abstract»

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  • Journal of Microelectromechanical Systems Information for authors

    Page(s): c3
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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