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Microelectromechanical Systems, Journal of

Issue 6 • Date Dec. 2002

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Displaying Results 1 - 25 of 26
  • Author Index

    Publication Year: 2002 , Page(s): 837 - 841
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    Freely Available from IEEE
  • Subject index

    Publication Year: 2002 , Page(s): 841 - 852
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  • Process compatible polysilicon-based electrical through-wafer interconnects in silicon substrates

    Publication Year: 2002 , Page(s): 631 - 640
    Cited by:  Papers (41)  |  Patents (32)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1043 KB) |  | HTML iconHTML  

    Electrical through-wafer interconnects (ETWI) which connect devices between both sides of a substrate are critical components for microelectromechanical systems (MEMS) and integrated circuits (IC), as they enable three-dimensional (3-D) structures and permit new packaging and integration geometries. Previously demonstrated ETWI are very difficult to integrate with standard semiconductor fabrication processes, not compatible with released sensors, do not permit extensive processing on both sides of the wafer, and are in general very application specific. This work describes the design, fabrication, and characterization of an ETWI technology for silicon substrates that can be broadly integrated with MEMS and IC processes. This interconnect is a passively isolated electrical through-wafer polysilicon plug, with a 20 μm diameter, 10-14 Ω resistance, and less than 1 pF capacitance. Plasma etching from both sides of the wafer is used to achieve a high-aspect ratio via (20:1 through 400 μm). The process is compatible with standard lithography, standard wafer handling, subsequent high-temperature processing, and released sensors integration. N-type and p-type versions are demonstrated, and isolated ground planes are added to provide shielding against substrate noise. Electrical properties of these ETWI are measured and analytically modeled. These ETWI are appropriate for integration with devices with impedances much greater than the ETWI, such as piezoresistive and capacitive sensor arrays. View full abstract»

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  • Fabrication of wafer-level thermocompression bonds

    Publication Year: 2002 , Page(s): 641 - 647
    Cited by:  Papers (26)  |  Patents (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (740 KB) |  | HTML iconHTML  

    Thermocompression bonding of gold is a promising technique for achieving low temperature, wafer-level bonding. The fabrication process for wafer bonding at 300°C via compressing gold under 7 MPa of pressure is described in detail. One of the issues encountered in the process development was e-beam source spitting, which resulted in micrometer diameter sized Au on the surfaces, and made bonding difficult. The problem was solved by inserting a tungsten liner to the graphite crucible. Surface segregation of Si on the Au surface at the bonding temperature was observed. Using Auger spectroscopy, a 1500 Å SiO2 barrier layer was shown to be sufficient in preventing Si from reaching the surface. Lastly, a four-point bend delamination technique was used to quantify the bond toughness. The associated process steps that were required to prepare the test specimens are described. The critical strain energy release rate for the bonds ranged between 22 to 67 J/m2 and was not shown to be strongly associated with the gold bond layer thickness in the thickness range studied (0.23 to 1.4 μm). View full abstract»

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  • A vacuum packaged surface micromachined resonant accelerometer

    Publication Year: 2002 , Page(s): 784 - 793
    Cited by:  Papers (64)  |  Patents (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (824 KB) |  | HTML iconHTML  

    This paper describes the operation of a vacuum packaged resonant accelerometer subjected to static and dynamic acceleration testing. The device response is in broad agreement with a new analytical model of its behavior under an applied time-varying acceleration. Measurements include tests of the scale factor of the sensor and the dependence of the output sideband power and the noise floor of the double-ended tuning fork oscillators as a function of the applied acceleration frequency. The resolution of resonant accelerometers is shown to degrade 20 dB/decade beyond a certain characteristic acceleration corner frequency. A prototype device was fabricated at Sandia National Laboratories and exhibits a noise floor of 40 μg/√(Hz) for an input acceleration frequency of 300 Hz. View full abstract»

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  • Fabrication, modeling, and testing of micro-cross-flow heat exchangers

    Publication Year: 2002 , Page(s): 726 - 735
    Cited by:  Papers (20)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1351 KB) |  | HTML iconHTML  

    Planar micro-cross-flow heat exchangers, similar in concept to most automobile radiators, have been fabricated using two different processes. A process that was previously reported (Harris et al., 2000) to fabricate a polymer heat exchanger involved embossing two identical polymer parts using the LIGA process. Then the two parts were aligned and bonded together. In this paper, a process is described to fabricate a nickel micro-cross-flow heat exchanger by embossing a sacrificial polymer mandrel using a LIGA-fabricated mold insert. The mandrel is coated with nickel (using either electroplating or electroless plating), then the sacrificial mandrel is dissolved. Experimental results are reported for both the polymer and nickel heat exchangers to determine the rates of heat transfer between the in-plane liquid (water) and the through-plane gas (air). Pressure drops of both fluid streams were also measured. The experimental results compare favorably with a modified version of the analytical model that was described previously. The fabricated heat exchangers have values of heat transfer/volume that are more than five times higher than conventional scale counterparts (with characteristic dimensions at least one order of magnitude larger than those reported here) and values of heat transfer/mass that are 50% greater than their conventional scale counterparts. View full abstract»

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  • Investigation of strain in microstructures by a novel moire method

    Publication Year: 2002 , Page(s): 829 - 836
    Cited by:  Papers (7)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (738 KB) |  | HTML iconHTML  

    A focused ion beam (FIB) moire method is proposed and demonstrated to measure the strain in microstructures. This technique is based on the advantages of the FIB system in nanofabrication, imaging, selective deposition, and fine adjustment. A nanograting is directly written on the top of the microstructures by ion milling without the requirement of an etch mask. The FIB moire pattern is formed by the interference between a prepared specimen grating and FIB raster scan lines. The strain of the microstructures is derived by calculating the average spacing of moire fringes. The sensitivity and accuracy of FIB moire in strain measurement is subsequently discussed. Since the local strain of a microstructure itself can be monitored during the process, the FIB moire technique has many potential applications in the mechanical metrology of microelectromechanical systems (MEMS). As an example, the strain distribution along the sticking microstructures and the contribution of surface oxidization and mass loading to the cantilever strain is determined by this FIB moire technique. View full abstract»

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  • Tunable optical filter of porous silicon as key component for a MEMS spectrometer

    Publication Year: 2002 , Page(s): 815 - 828
    Cited by:  Papers (31)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1415 KB) |  | HTML iconHTML  

    We present a microspectrometer based on a tunable interference filter for infrared or visible light that scans the desired part of the spectrum within milliseconds. A single pixel detector measures serially the intensity at selected wavelengths. This concept avoids expensive linear detectors as used for grating spectrometers. The tunable filter is fabricated by a new porous silicon technology using only two photolithography steps. A Bragg mirror or a Fabry-Perot bandpass filter for transmission wavelengths between 400 nm and 8 μm at normal incidence is created by modulations of the refractive index in the filter plate. Two thermal bimorph micro-actuators tilt the plate by up to 90°, changing the incidence angle of the beam to be analyzed. This tunes the wavelength transmitted to the detector by a factor of 1.16. The filter area can be chosen between 0.27 × 0.70 mm2 and 2.50 × 3.00 mm2, the filter thickness is typically 30 μm. The spectral resolution of Δλ/λ = 1/25 is sufficient for most sensor applications, e.g., measurement of CO2 and CO in combustion processes by their IR absorption bands as will be presented. View full abstract»

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  • A MEMS piggyback actuator for hard-disk drives

    Publication Year: 2002 , Page(s): 648 - 654
    Cited by:  Papers (15)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (713 KB) |  | HTML iconHTML  

    This paper reports a new fabrication process and designing method to integrate MEMS piggyback actuators on a silicon-on-insulator (SOI) wafer with magnetic read/write heads of hard-disk drives. Large bandwidth of the tracking servo system is designed by reducing the load mass for the tracking microactuator to be around 40 μg. A prototype electrostatic MEMS actuator (2 mm × 3 mm × 0.6 mm) of multiple parallel plates has been successfully integrated by using high-aspect ratio microstructures (gap opening 2 μm into 50-μm-SOI wafer) patterned by deep reactive-ion-etching (DRIE). A dc displacement of 0.5 μm, which is almost the same size as data track width, has been obtained at a driving voltage of dc 60 V and the fundamental resonance is found at 16 kHz. An analytical model of the MEMS piggyback actuator has been proposed to predict electromechanical performance. The fabrication method proposed here is very simple and straightforward to put the head-element-drive mechanism into practice. View full abstract»

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  • Design, fabrication, and testing of an electrohydrodynamic ion-drag micropump

    Publication Year: 2002 , Page(s): 684 - 690
    Cited by:  Papers (39)
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    This paper presents the design, fabrication, and testing of a novel electrohydrodynamic (EHD) ion-drag micropump. In order to maximize the electrical field gradients that are responsible for EHD pumping, we incorporated three-dimensional (3-D) triangular bumps of solder as part of the EHD electrodes. To form these bumps, Niobium was sputter-deposited onto a ceramic substrate, coated with photoresist, optically exposed and etched using a reactive ion etcher to define the electrode pattern. The substrate was then "dipped" into a molten solder pool. Since the solder adheres only to the metallic film, bumps of solder form on the electrodes, giving the electrodes a significant 3-D character. The overall dimensions of the micropump are 19 mm × 32 mm × 1.05 mm. Four different designs were fabricated and tested. Static pressure tests were performed with a 3M Thermal Fluid (HFE-7100) as the working fluid and the optimum design was identified. The results with the thermal fluid were highly promising and indicated a pumping head of up to 700 Pa at an applied voltage of 300 V. The experimental results for the four different designs show that the presence of the 3-D bump structures significantly improves the pumping performance. Also, a much better pumping performance was obtained with the micropump in which the emitter had a saw-tooth shape. View full abstract»

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  • A fast method for particulate microflows

    Publication Year: 2002 , Page(s): 691 - 702
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1201 KB) |  | HTML iconHTML  

    Modeling of active control of microparticles is important in a number of different microfluidic applications, including bioflows and self-assembled structures. We present here a fast method for simulating the dynamics of many particles in complex microgeometries. The method is based on a spatial distribution of finite force multipoles and requires much less resolution than full direct numerical simulations. The numerical formulation is summarized, and examples are given for Stokes flow and low Reynolds number flow in smooth and rough microchannels. Comparisons made with full direct numerical simulations and experiments validate the accuracy and efficiency of the proposed approach. View full abstract»

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  • Mechanics of microcantilever beams subject to combined electrostatic and adhesive forces

    Publication Year: 2002 , Page(s): 754 - 764
    Cited by:  Papers (38)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (541 KB) |  | HTML iconHTML  

    One of the most important issues facing the continued development and application of microelectromechanical systems (MEMS) is that of adhesion and friction between microstructures intended to transfer force. In this work, we develop modeling approaches for studying adhesion (i.e., stiction) using the observed shape of microcantilevers under electrostatic loading. Analytical models for an idealized configuration are presented first. The solutions reveal the regimes over which the cantilever deflections are sensitive to adhesion versus applied loading. Also, the energy release rate and hence the cantilever adhesion value is shown to be independent of the curvature of the initially freestanding beam. Second, with a finite-element modeling approach, we quantify the slight sensitivity of the cantilever deflections to the surface force law assumed and show that with Angstrom scale resolution of beam deflections, cohesive zone law information can in principle be deduced. We also use this approach to model the nonuniform electrostatic loading force used in our experiments and the effect of support post compliance. We then demonstrate how adhesion values are obtained along the length of a microcantilever. View full abstract»

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  • A thermal-bubble-actuated micronozzle-diffuser pump

    Publication Year: 2002 , Page(s): 665 - 671
    Cited by:  Papers (54)  |  Patents (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (950 KB) |  | HTML iconHTML  

    A thermal-bubble-actuated micropump by the principles of liquid/vapor phase transition and nozzle-diffuser flow regulation is successfully demonstrated. The micropump consists of a resistive heater, a pair of nozzle-diffuser flow controller and a 1 mm in diameter, 50 μm in depth pumping chamber. The actuation mechanism comes from periodically nucleating and collapsing thermal bubbles. A net flow is generated from the nozzle to the diffuser by the nozzle-diffuser flow controller. Two heater designs, single-bubble and dual-bubble actuation mode, have been investigated. In the single-bubble pumping mode, a maximum flow rate of 5 μl/min is measured when the driving pulse is 250 Hz at 10% duty cycle under an average power consumption of 1 W. A similar flow rate of 4.5 μl/min is achieved in the dual-bubble pumping mode, at the driving pulse of 5% duty cycle at 400 Hz with lower average power consumption, 0.5 W. The static pumping pressure is measured at a maximum value of 377 Pascal when the net volume flow rate is zero. As an application example in a microfluidic device, this valve-less micropump is used in a microfluidic system to enhance the fluid mixing by agitating the flows. View full abstract»

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  • Design of atomic force microscope cantilevers for combined thermomechanical writing and thermal reading in array operation

    Publication Year: 2002 , Page(s): 765 - 774
    Cited by:  Papers (35)  |  Patents (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (687 KB) |  | HTML iconHTML  

    In thermomechanical data writing, a resistively-heated atomic force microscope (AFM) cantilever tip forms indentations in a thin polymer film. The same cantilever operates as a thermal proximity sensor to detect the presence of previously written data bits. This paper uses recent progress in thermal analysis of the writing and reading modes to develop new cantilever designs for increased speed, sensitivity, and reduced power consumption in both writing and reading operation. Measurements of cantilever electrical resistance during heating reveals physical limits of cantilever writing and reading, and verifies a finite-difference thermal and electrical simulation of cantilever operation. This work proposes two new cantilever designs that correspond to fabrication technology benchmarks. Simulations predict that the proposed cantilevers have a higher data rate and are more sensitive than the present cantilever. The various cantilever designs offer single-bit writing times of 0.2 μs-25 μs for driving voltages of 2-25 V. The thermal reading ΔR/R sensitivity is as high as 4×10-4 per vertical nm in near steady-state operation. View full abstract»

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  • Parylene gas chromatographic column for rapid thermal cycling

    Publication Year: 2002 , Page(s): 718 - 725
    Cited by:  Papers (53)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1216 KB) |  | HTML iconHTML  

    This paper presents a parylene gas chromatographic column with an embedded heating element. The parylene coating on a silicon microchannel and parylene/parylene thermal bonding technique were employed to fabricate a parylene column. The heating element is a thin gold film evaporated on the corrugated surface of the parylene column having long and rectangular geometry. Joule heating via the thin gold film is a very effective heating system for a parylene column. ANSYS heat transfer analysis was performed to investigate the thermal cycling and temperature uniformity of the parylene column. The parylene column showed much faster heating and cooling rates as well as lower power consumption compared to a silicon/glass column. The temperature difference between the top and the bottom of a parylene column that is due to the low thermal conductivity of parylene could be reduced to less than 0.1 K by inserting a thin metal layer between two parylene layers, forming a triple layer structure (parylene/platinum/parylene). View full abstract»

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  • V-band reflection-type phase shifters using micromachined CPW coupler and RF switches

    Publication Year: 2002 , Page(s): 808 - 814
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1930 KB) |  | HTML iconHTML  

    Micromachined reflection-type phase shifters with small size and low loss for V-band communication systems are described. Two- and three-bit reflection type phase shifters were designed, fabricated, and measured. The micromachined air-gap overlay coupler and the direct contact type series switches were employed to implement the phase shift and reduce an insertion loss. The phase shift can be obtained by changing the length of the open-ended stubs using the cascaded MEMS switches. The fabricated two-bit phase shifter has a measured phase shift of 0°, 41.5°, 84.3°, and 128.7° with the consecutive actuation of the series MEMS switches. The actuation voltage of the switches is 35 V and the measured switching ON time is 5.1 μs. The average insertion loss of the two-bit phase shifter measured 4.1 dB at 60 GHz and the return losses for all phase shift states are better than 11.7 dB from 50 to 70 GHz. The two-bit phase shifter is small, 1.5 mm × 2.1 mm. By cascading the two-bit phase shifter and a 180° phase shifter (one-bit), a three-bit phase shifter is realized, which has a phase shift of 265.5° and an average insertion loss of 4.85 dB at 60 GHz. The size of the three-bit phase shifter is 3.2 mm × 2.1 mm. View full abstract»

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  • Energy dissipation in submicrometer thick single-crystal silicon cantilevers

    Publication Year: 2002 , Page(s): 775 - 783
    Cited by:  Papers (91)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (807 KB) |  | HTML iconHTML  

    Discusses four kinds of mechanical energy losses in ultrathin micro-cantilevers of 60 nm, 170 nm, and 500 nm in thickness: thermoelastic loss, air damping, support loss, and surface loss. For the cantilevers with thickness H<500 nm and length L>10 μm, thermoelastic loss is negligible. But it becomes significant when the beam thickness H>500 nm and the length L<10 μm. The cantilevers are very liable to air damping, hardly operated at pressure higher than 10-3 mbar. In a high vacuum (<10-3 mbar), air damping is negligible, the support and surface loss play an important role. The shorter the cantilevers, the larger the support energy loss. For the cantilevers with L/H<100, the quality factors (Q factors) are limited by the support loss. When the length L>30 μm, the Q factors of the cantilevers are proportional to their thickness, i.e., surface loss dominates the mechanical behavior. Annealing the cantilevers of 170 nm thickness at 1000°C for 30 s under an ultrahigh vacuum (UHV) condition results in an over one order-of-magnitude increase of the Q factor, up to about 2.5×105 for cantilevers of 30-90 μm in length. View full abstract»

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  • A water-powered osmotic microactuator

    Publication Year: 2002 , Page(s): 736 - 742
    Cited by:  Papers (31)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (737 KB)  

    This paper presents a microactuator that utilizes osmosis to produce mechanical actuation without consuming any electrical energy. The microactuator is made of cellulose acetate with cylindrical chamber of 500 to 2000 μm in diameter and of 200 to 1000 μm in depth. Sodium chloride is chosen as the osmotic driving agent to be placed inside the chamber. A semipermeable diaphragm made of cellulose acetate is processed at the bottom of the chamber to control the water flow. Either a cellulose acetate diaphragm or an impermeable diaphragm made of vinylidene chloride and acrylonitrile copolymer is spin-coated on top of the chamber as the actuation diaphragm. Using the principle of osmosis, this water-powered, osmotic microactuator can employ high osmotic pressure (a chemical potential) up to 35.6 MPa to provide hydrostatic pressure for mechanical actuation. Experimental measurements show that up to 800 μm vertical diaphragm movement (diaphragm size of 800 μm in diameter) and constant volume expansion rate of 4.5 to 11.5 nL/h can be achieved. When integrated with other microfluidic devices, this osmotic microactuator could serve as a clean, compact and inexpensive fluidic actuation source. View full abstract»

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  • Integrated measurement-modeling approaches for evaluating residual stress using micromachined fixed-fixed beams

    Publication Year: 2002 , Page(s): 743 - 753
    Cited by:  Papers (13)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (969 KB) |  | HTML iconHTML  

    Two methodologies have been developed to determine the biaxial residual stress value in thin films using electrostatically actuated fixed-fixed beam test structures. In the first, we determine the compliance matrix of the support posts using 3-D finite-element analysis. The residual stress value is then found from the best fit between the measured and modeled deflection curves, with the residual stress as the only free parameter in the model. An accuracy of ±0.5 MPa for the average biaxial residual stress level is evaluated from the reproducibility of independent measurements over a wide range of loadings. The key to the second methodology lies in the recognition that for a given value of residual stress, there exists a unique family of deflection curves associated with two adjacent beams of different lengths. Therefore, compliance information can be extracted directly from the deflection curves. We proceed to show that essentially the same values of residual stress are found by the two methodologies, while the latter allows much more rapid extraction of the residual stress. With the second methodology established, we find that residual stress values vary across a quarter of a six-inch diameter wafer by 2.5 MPa for three structural levels of polycrystalline silicon in our five-level surface micromachining technology. View full abstract»

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  • Electrically tunable collective response in a coupled micromechanical array

    Publication Year: 2002 , Page(s): 802 - 807
    Cited by:  Papers (55)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1641 KB) |  | HTML iconHTML  

    We employ optical diffraction to study the mechanical properties of a grating array of suspended doubly clamped beams made of Au. The device allows application of electrostatic coupling between the beams that gives rise to formation of a band of normal modes of vibration (phonons). We parametrically excite these collective modes and study the response by measuring the diffraction signal. The results indicate that nonlinear effects strongly affect the dynamics of the system. Further optimization will allow employing similar systems for real-time mechanical spectrum analysis of electrical waveforms. View full abstract»

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  • Design and fabrication of microfluidic devices for multiphase mixing and reaction

    Publication Year: 2002 , Page(s): 709 - 717
    Cited by:  Papers (86)  |  Patents (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (875 KB) |  | HTML iconHTML  

    Using silicon microfabrication technology, microchemical devices have been constructed for the purpose of conducting heterogeneously catalyzed multiphase reactions. The motivation behind the design, the fabrication approach, and the experimental characterization are presented for two classes of devices. The first design involves multiple parallel channels with integrated filter structures to incorporate standard catalytic materials. These catalysts are in the form of finely divided porous particles in a packed-bed arrangement. The second device involves the incorporation of porous silicon as a catalyst support, in the form of a thin layer covering microstructured channels. These microstructured channels simulate the structure of a packed bed and enhance mass transfer relative to an open channel. The ability to incorporate features at the tens-of-microns scale can reduce the mass-transfer limitations by promoting mixing and dispersion for the multiple phases. Directly integrating the catalyst support structures into the channels of the microreactor allows the precise definition of the bed properties, including the support's size, shape and arrangement, and the void fraction. Such a design would find broad applicability in enhancing the transport and active surface area for sensing, chemical, and biochemical conversion devices. Reaction rates for the gas-liquid-solid hydrogenation of cyclohexene using the integrated catalyst with porous silicon as a support compare favorably to those rates obtained with the packed-bed approach. In both cases, the mass transfer coefficient is at least 100 times better than conventional laboratory reactors. View full abstract»

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  • The piezoelectric valve-less pump - improved dynamic model

    Publication Year: 2002 , Page(s): 655 - 664
    Cited by:  Papers (34)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (613 KB) |  | HTML iconHTML  

    The piezoelectric valve-less pump is an attractive device to be used as a micro pump for low flow rates. The pump converts the reciprocating motion of a diaphragm, activated by a piezoelectric disk, into a pumping action. Instead of conventional valves, which have moving parts, nozzle/diffuser elements that have a preferential flow direction are used to direct the flow from the inlet to the outlet. In this paper, an improved dynamic model for the simulation of valve-less piezoelectric pumps is presented. The model is capable of accurate simulation of the pump performance including the natural frequency, flow rate, and pressure drop. The model is utilized here to study the effect of the driving frequency and the inlet/outlet length and diameter of the leading pipes on the pump performance. Comparison with experiments shows good agreement with a minimal number of adjusting parameters. View full abstract»

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  • Fabrication of high-density electrical feed-throughs by deep-reactive-ion etching of Pyrex glass

    Publication Year: 2002 , Page(s): 625 - 630
    Cited by:  Papers (54)  |  Patents (13)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1031 KB) |  | HTML iconHTML  

    This paper describes the fabrication technology for high-density electrical feed-throughs in Pyrex glass wafers. Small through holes (40-80 μm in diameter) in Pyrex glass wafers have been fabricated using deep-reactive-ion etching (DRIE) in a sulfur hexafluoride (SF6) plasma. The maximum aspect ratios obtained were between 5 and 7 for a hole pattern and 10 for a trench pattern. Through the wafer etching of a hole pattern of 50 μm diameter was carried out using 150-μm-thick Pyrex glass wafers. The electrical feed-throughs in the wafers were fabricated by filling the through-holes with electroplated nickel. We were able to successfully bond the glass wafer to silicon by anodic bonding after removing the electroplated nickel on the surface of the wafer by chemical-mechanical polishing (CMP). The electric resistance of the feed-through was estimated by a 4 point wire sensing method to be about 40 mΩ per hole. The heat cycles test shows that the resistance changes were within 3% after 100 cycles. The fabrication of high density electrical feed-throughs is one of the key processes in the field of MEMS. Probable applications of this technology are in electrical feed-throughs between logic elements and microprobe arrays for high-density data storage and for packaged devices. View full abstract»

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  • Fabrication and characterization of a micromechanical sensor for differential detection of nanoscale motions

    Publication Year: 2002 , Page(s): 703 - 708
    Cited by:  Papers (20)  |  Patents (21)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (620 KB) |  | HTML iconHTML  

    We have micromachined a mechanical sensor that uses interferometry to detect the differential and absolute deflections of two adjacent cantilevers. The overall geometry of the device allows simple fluidic delivery to each cantilever to immobilize molecules for biological and chemical detection. We show that differential sensing is 50 times less affected by ambient temperature changes than the absolute, thus enabling a more reliable differentiation between specific cantilever bending and background effects. We describe the fabrication process and show results related to the dynamic characterization of the device as a differential sensor. The root-mean-squared (r.m.s.) sensor noise in water and air is ∼1 nm over the frequency range of 0.4-40 Hz. We also find that in air, the deflection resolution is limited only by the cantilever's thermomechanical noise level of 0.008 Å/Hz12/ over the frequency range of 40-1000 Hz. View full abstract»

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  • Piezoresistive accelerometers for MCM package

    Publication Year: 2002 , Page(s): 794 - 801
    Cited by:  Papers (12)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1197 KB) |  | HTML iconHTML  

    Describes the first steps carried out for the integration of piezoresistive accelerometers in an MCM-D (D-type multichip modules with flip-chip interconnection) package. The bulk micromachined accelerometer technology and its modification to comply with MCM-D packaging technology requirements are presented. The accelerometer technology is based on BESOI (Bond and Etch Back Silicon-On-Insulator) wafers. The main characteristic of this technology is the use of the buried silicon oxide layer as an etch stop and as a sacrificial layer. In addition, over-range protection and self-test systems are defined without any additional photolithographic step or process. The flip chip attachment requires solderable metals in the bump pads. In addition, a sealing ring has been defined around the movable parts of the sensors to protect them from the underfill used during the final packaging process. Cantilever beam accelerometers with a self-test system are presented as example of the combined technology. The design, simulation, fabrication and characterization of the devices prior to the MCM-D packaging are presented as well. 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