By Topic

Microelectromechanical Systems, Journal of

Issue 4 • Date Aug. 2010

Filter Results

Displaying Results 1 - 25 of 39
  • Table of contents

    Publication Year: 2010 , Page(s): C1 - C4
    Save to Project icon | Request Permissions | PDF file iconPDF (50 KB)  
    Freely Available from IEEE
  • Journal of Microelectromechanical Systems publication information

    Publication Year: 2010 , Page(s): C2
    Save to Project icon | Request Permissions | PDF file iconPDF (57 KB)  
    Freely Available from IEEE
  • Wireless Intraocular Pressure Sensing Using Microfabricated Minimally Invasive Flexible-Coiled LC Sensor Implant

    Publication Year: 2010 , Page(s): 721 - 734
    Cited by:  Papers (28)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1561 KB) |  | HTML iconHTML  

    This paper presents an implant-based wireless pressure sensing paradigm for long-range continuous intraocular pressure (IOP) monitoring of glaucoma patients. An implantable parylene-based pressure sensor has been developed, featuring an electrical LC-tank resonant circuit for passive wireless sensing without power consumption on the implanted site. The sensor is microfabricated with the use of parylene C (poly-chloro-p-xylylene) to create a flexible coil substrate that can be folded for smaller physical form factor so as to achieve minimally invasive implantation, while stretched back without damage for enhanced inductive sensor-reader coil coupling so as to achieve strong sensing signal. A data-processed external readout method has also been developed to support pressure measurements. By incorporating the LC sensor and the readout method, wireless pressure sensing with 1-mmHg resolution in longer than 2-cm distance is successfully demonstrated. Other than extensive on-bench characterization, device testing through six-month chronic in vivo and acute ex vivo animal studies has verified the feasibility and efficacy of the sensor implant in the surgical aspect, including robust fixation and long-term biocompatibility in the intraocular environment. With meeting specifications of practical wireless pressure sensing and further reader development, this sensing methodology is promising for continuous, convenient, direct, and faithful IOP monitoring. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Wafer-Level Parylene Packaging With Integrated RF Electronics for Wireless Retinal Prostheses

    Publication Year: 2010 , Page(s): 735 - 742
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (901 KB) |  | HTML iconHTML  

    This paper presents an embedded chip integration technology that incorporates silicon housings and flexible Parylene-based microelectromechanical systems (MEMS) devices. Accelerated-lifetime soak testing is performed in saline at elevated temperatures to study the packaging performance of Parylene C thin films. Experimental results show that the silicon chip under test is well protected by Parylene, and the lifetime of Parylene-coated metal at body temperature (37°C) is more than 60 years, indicating that Parylene C is an excellent structural and packaging material for biomedical applications. To demonstrate the proposed packaging technology, a flexible MEMS radio-frequency (RF) coil has been integrated with an RF identification (RFID) circuit die. The coil has an inductance of 16 μH with two layers of metal completely encapsulated in Parylene C, which is microfabricated using a Parylene-metal-Parylene thin-film technology. The chip is a commercially available read-only RFID chip with a typical operating frequency of 125 kHz. The functionality of the embedded chip has been tested using an RFID reader module in both air and saline, demonstrating successful power and data transmission through the MEMS coil. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A Microfluidic Device for Continuous-Flow Magnetically Controlled Capture and Isolation of Microparticles

    Publication Year: 2010 , Page(s): 743 - 751
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (847 KB) |  | HTML iconHTML  

    This paper presents a novel microfluidic device that exploits magnetic manipulation for integrated capture and isolation of microparticles in continuous flow. The device, which was fabricated from poly(dimethylsiloxane) (PDMS) by soft-lithography techniques, consists of an incubator and a separator integrated on a single chip. The incubator is based on a novel scheme termed target acquisition by repetitive traversal (TART), in which surface-functionalized magnetic beads repetitively traverse a sample to seek out and capture target particles. This is accomplished by a judicious combination of a serpentine microchannel geometry and a time-invariant magnetic field. Subsequently, in the separator, the captured target particles are isolated from nontarget particles via magnetically driven fractionation in the same magnetic field. Due to the TART incubation scheme that uses a corner-free serpentine channel, the device has no dead volume and allows minimization of undesired particle or magnetic-bead retention. Single-chip integration of the TART incubator with the magnetic-fractionation separator further allows automated continuous isolation and retrieval of specific microparticles in an integrated manner that is free of manual off-chip sample incubation, as often required by alternative approaches. Experiments are conducted to characterize the individual incubation and separation components, as well as the integrated device. The device is found to allow 90% of target particles in a sample to be captured and isolated and 99% of nontarget particles to be eliminated. With this high separation efficiency, along with excellent reliability and flexibility, the device is well suited to sorting, purification, enrichment, and detection of micro/nanoparticles and cells in lab-on-a-chip systems. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Kinematics of Specifically Captured Circulating Tumor Cells in Bio-Functionalized Microchannels

    Publication Year: 2010 , Page(s): 752 - 763
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (921 KB) |  | HTML iconHTML  

    The attachment kinematics of cancer cells under hydrodynamic loading in antibody-functionalized microchannels has been studied. Epithelial-cell-adhesion-molecule antibodies are immobilized on the microchannel surface for specific capture of the target cancer cells from homogeneous cell suspensions. The specific interaction between the cancer cell receptors and the immobilized antibodies under static conditions is demonstrated. The capture efficiency of the target cells from homogeneous suspensions under applied hydrodynamic flow field has been investigated, revealing a characteristic shear stress. Applying a lower stress allows the capture of most target cells, while the capture efficiency drops sharply with an increasing shear stress. The captured cells are spatially distributed along the microchannel; both the velocity and the distance travelled by cells prior to capture are measured. The characteristic time and length scales for cell capture are determined, and a log-normal statistical distribution is proposed to describe the observations. Furthermore, a first-order kinetic model for receptor-ligand bond formation provides a rough estimate of the cell adhesion rate constant. Under a low shear stress, the on-rate is much higher than the off-rate, allowing capture of most loaded cells. The off-rate constant increases exponentially with an increasing shear stress, such that above the characteristic stress level, most loaded cells avoid capture. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A Versatile Cell Contractility Mapping Transducer Utilizing Moiré-Based Technique

    Publication Year: 2010 , Page(s): 764 - 773
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1338 KB) |  | HTML iconHTML  

    The mapping of contraction forces developed from cells to their extracellular matrix is crucial to understanding how cells regulate their physiological function to adapt to their living environment and cellular processes. This paper reports a novel cell contractility mapping transducer utilizing moiré patterns as a visual and quantitative tool. Coherent light diffracted from two closely placed microfabricated periodic substrates is capable of mapping cell contraction forces via mapping the in-plane displacement on the sample substrate. By integrating cell culture environment and automated Fourier-based fringe analysis, the moiré pattern generated through microfabricated periodic substrates enables the mapping of cell contraction force distribution through phase changes encoded in carrier moiré fringe patterns. We demonstrated utilizing the transducer to map cardiac myocyte contraction under electric stimulation and vascular smooth muscle cell contractility evolutions triggered by agonist. Given the unique properties of optical moiré techniques (i.e., their automatic displacement and strain contouring and their magnification effect for small displacements), this new approach would be an improvement over existing techniques since it can be integrated with the existing engineered substrates and provide a direct contour of cell forces and fast detection of abnormal cell contractions. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • High- Q Tunable Microwave Cavity Resonators and Filters Using SOI-Based RF MEMS Tuners

    Publication Year: 2010 , Page(s): 774 - 784
    Cited by:  Papers (33)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1443 KB) |  | HTML iconHTML  

    This paper presents the modeling, design, fabrication, and measurement of microelectromechanical systems-enabled continuously tunable evanescent-mode electromagnetic cavity resonators and filters with very high unloaded quality factors (Qu). Integrated electrostatically actuated thin diaphragms are used, for the first time, for tuning the frequency of the resonators/filters. An example tunable resonator with 2.6:1 (5.0-1.9 GHz) tuning ratio and Qu of 300-650 is presented. A continuously tunable two-pole filter from 3.04 to 4.71 GHz with 0.7% bandwidth and insertion loss of 3.55-2.38 dB is also shown as a technology demonstrator. Mechanical stability measurements show that the tunable resonators/filters exhibit very low frequency drift (less than 0.5% for 3 h) under constant bias voltage. This paper significantly expands upon previously reported tunable resonators. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Wireless Signaling of Beta Detection Using Microdischarges

    Publication Year: 2010 , Page(s): 785 - 793
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1293 KB) |  | HTML iconHTML  

    This paper explores the possibility of using microdischarges to generate broadband radio-frequency (RF) signaling from gas-based microdetectors of beta radiation. The concept is evaluated using two types of lithographically manufactured test structures: 1) a silicon/glass stack with etched detection cavities and 2) a planar metal-on-glass structure. The test structures include electrodes that bias a fill-gas region with a high electric field, in which incident beta particles initiate avalanche-driven microdischarge pulses that inherently transmit RF spectra with frequency content extending into the ultrawideband (UWB) range of communication. The discharge gaps range from 165 to 500 μm. The impact of operating pressure, fill gases (which are typically a mixture of Ne and N2), and electrode materials (Ni and Cu) on operating voltage and wireless signaling performance is evaluated. Tests are performed in the proximity of weak (0.1-1.0-μCi) beta sources (90Sr and 204TI). Both types of test structures are capable of producing UWB signals spanning > 1 GHz. Measurements in an anechoic chamber using various receiver antennas show that microdischarges can produce field strengths up to 90 dB · μV/m measured at 1.67 m from the test structure. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • An Experimental and Theoretical Investigation of Dynamic Pull-In in MEMS Resonators Actuated Electrostatically

    Publication Year: 2010 , Page(s): 794 - 806
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1743 KB) |  | HTML iconHTML  

    We present experimental and theoretical investigations of dynamic pull-in of electrostatically actuated resonators. Several experimental data are presented, showing regimes of ac forcing amplitude versus ac frequency, where a resonator is forced to pull in if operated within these regimes. Results are shown for primary and secondary resonance excitations. The influences of the initial conditions of the system, the ac excitation amplitude, the ac frequency, the excitation type, and the sweeping type are investigated. A shooting technique to find periodic motions and a basin-of-attraction analysis are used to predict the limits of the pull-in bands. When compared with the experimental data, the results have shown that the pull-in limits coincide with 30%-40% erosion lines of the safe basin in the case of primary resonance and 5%-15% erosion lines of the safe basin in the case of subharmonic resonance. Bifurcation diagrams have been constructed, which designers can use to establish factors of safety to reliably operate microelectromechanical-systems resonators away from pull-in bands and the danger of pull-in, depending on the expected disturbances and noise in the systems. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • CMOS-Integrated RF MEMS Resonators

    Publication Year: 2010 , Page(s): 807 - 815
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (625 KB) |  | HTML iconHTML  

    We present a design approach that enables monolithic integration of high-quality-factor (Q) radio-frequency (RF) microelectromechanical systems (MEMS) resonators with CMOS electronics. Commercially available CMOS processes that feature two polysilicon layers and field oxide isolation can be used to implement this approach. By using a nonplanar resonator geometry in conjunction with mechanical stress in polycrystalline silicon (poly) gate layers, we create rigid and robust mechanical structures with efficient electromechanical transduction. We demonstrate polysilicon domes with capacitive pickup and arch-bridge resonators with piezoresistive readout. The small footprint of our MEMS structures enables on-chip integration of large arrays of resonators for RF signal processing or sensing applications. Their large surface-to-volume ratio in combination with high rigidity (that alleviates stiction associated with wet chemistry processing) can make these resonators particularly useful for sensors that require surface functionalization. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A High-Power Temperature-Stable Electrostatic RF MEMS Capacitive Switch Based on a Thermal Buckle-Beam Design

    Publication Year: 2010 , Page(s): 816 - 826
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1022 KB) |  | HTML iconHTML  

    This paper presents the design, fabrication and measurements of a novel vertical electrostatic RF MEMS switch which utilizes the lateral thermal buckle-beam actuator design in order to reduce the switch sensitivity to thermal stresses. The effect of biaxial and stress gradients are taken into consideration, and the buckle-beam designs show minimal sensitivity to these stresses. Several switches with 4,8, and 12 suspension beams are presented. All the switches demonstrate a low sensitivity to temperature, and the variation in the pull-in voltage is ~ -50 mV/°C from 25-125°C. The change in the up-state capacitance for the same temperature range is <; ± 3%. The switches also exhibit excellent RF and mechanical performances, and a capacitance ratio of ~ 20-23 (Cυ. = 85-115 fF, Cd = 1.7-2.6 pF) with Q > 150 at 10 GHz in the up-state position is reported. The mechanical resonant frequencies and quality factors are fο = 60-160 kHz and Qm = 2.3-4.5, respectively. The measured switching and release times are ~ 2-5 μs and ~ 5-6.5 μs, respectively. Power handling measurements show good stability with ~ 4 W of incident power at 10 GHz. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Lamb Waves and Resonant Modes in Rectangular-Bar Silicon Resonators

    Publication Year: 2010 , Page(s): 827 - 839
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (965 KB) |  | HTML iconHTML  

    This paper presents two newly developed models of capacitive silicon bulk acoustic resonators (SiBARs) characterized by a rectangular-bar geometry. The first model is derived from an approximate analytical solution of the linear elastodynamic equations for a parallelepiped made of an orthotropic material. This solution, which is recognized to represent a Lamb wave propagating across the width of the resonator, yields the frequencies and shapes of the resonance modes that typically govern the operation of SiBARs. The second model is numerical and is based on a finite-element multiphysics simulation of both acoustic wave propagation in the resonator and electromechanical transduction in the capacitive gaps of the device. It is especially useful in the computation of the SiBAR performance parameters, which cannot be obtained from the analytical model, e.g., the relationship between the transduction area and the insertion loss. Comparisons with the measurements taken on a set of silicon resonators fabricated using electron-beam lithography show that both models can predict the resonance frequencies of SiBARs with a relative error, which, in most cases, is significantly smaller than 1%. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Sequential Plasma-Activated Bonding Mechanism of Silicon/Silicon Wafers

    Publication Year: 2010 , Page(s): 840 - 848
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (886 KB) |  | HTML iconHTML  

    To investigate the sequentially plasma-activated bonding (SPAB) mechanism of silicon/silicon wafers, the surface hydrophilicity, and the interface voids, nanostructures and chemical compositions that control the bonding quality, such as bonding strength, have been observed. Although the sequentially plasma-activated surfaces are hydrophilic, the SPAB mechanism is not identical to the hydrophilic bonding. SPAB shows high bonding strength at room temperature and water rearrangement below 150°C, which removes the water from the interface to the bulk. This results in a thinner amorphous silicon oxide layer at the interface. Further heating of the bonded wafers desorbs water from the bulk. The heating at 225°C starts producing hillocks at the interface, which turn into voids at temperatures above 400°C for absorbing the hydrogen gas produced from the desorbed water at the interface. The new and bigger voids are due to the hydrogen gas at 600°C and start accumulating at 800°C, resulting in bubbles caused by the accumulation of voids at the preferential sites. No nitrogen exists either in silicon or in the amorphous SiO2 layer at the interface. The Si-L2, 3 edges from the amorphous silicon oxide at the bonded interface are identical to those of the standard SiO2. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Fabrication of High-Aspect-Ratio Alumina–Nickel Coaxial Nanorod Array by Electrodeposition

    Publication Year: 2010 , Page(s): 849 - 853
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (975 KB) |  | HTML iconHTML  

    In this paper, we investigate the fabrication of high-aspect-ratio (~500) larger area alumina-metal coaxial nanorod arrays using electrodeposition with an anodic aluminum oxide template. An annealing process was implemented after electrodeposition to enhance the mechanical properties of the deposited metal nanorods. Phosphoric acid was then used to gradually etch off the alumina that enclosed each individual metal nanorod starting from the borders between the hexagonal cells. The transmission electron microscopy and selected area electron diffraction analyses were implemented to verify the alumina/nickel coaxial structure. The alumina shell wrapping each individual metal nanorod served as an insulator for the core metal. The high aspect ratio of the alumina-metal coaxial nanorods described herein makes them practicable for use as nanoprobes or electrodes that are capable of penetrating individual cell membranes to sense the biological functions of the cells. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Analysis of Circular PDMS Microballoons With Ultralarge Deflection for MEMS Design

    Publication Year: 2010 , Page(s): 854 - 864
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1757 KB) |  | HTML iconHTML  

    This paper presents the simplified analytical and numerical analyses of the ultralarge deflection of circular polydimethylsiloxane (PDMS) microballoons (MBs) under pressure for microelectromechanical systems design. The analytical model assuming spherical symmetry on the deformed shape of MB yields a simplified solution on the pressure-normalized maximum deflection and two in-plane principal strains of the ultralargely deflected MB. The accuracy of the theoretical model is evaluated by comparing against the experimental results. Furthermore, by using a computational analysis that incorporates a Mooney-Rivlin model for a PDMS micromembrane, the properties of the PDMS fabricated at a mixing ratio of 10:1 base to catalyst, a curing temperature of 20°C, and a curing time of 48 h are determined for noncircular PDMS micromembrane analysis. In the experimental study, eight types of PDMS MBs, each of which has a membrane radius of 143, 202, 452, or 904 μm and a membrane thickness of 10 or 20 μm, are characterized in air and in cell culture media. A new strain-measuring method using fluorescent polymer microspheres for the PDMS MB is also introduced. The characterization of the PDMS MBs in air validates our theoretical model and shows an increase in elastic modulus as the membrane thickness decreases. The effect of cell culture media on the membrane rigidity of PDMS is also examined for biological applications of PDMS. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Nanometrology Using a Quasiperiodic Pattern Diffraction Optical Ruler

    Publication Year: 2010 , Page(s): 865 - 870
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (721 KB) |  | HTML iconHTML  

    This paper presents a nanometrology optical ruler imaging system to enable rapid wafer-scale nanometrology, particularly for scanning probe microscopes. The ruler is generated by the diffraction of a 10-8 stabilized laser by a metal thin-film pattern. Microfabrication techniques create a high-count quasiperiodic aperture array in the film which generates a translationally asymmetric feature-dense optical diffraction pattern well suited for the nanometrology application. An imager array samples the optical ruler and calculates its position by Fourier transform cross-correlation methods. Numerically, it is found that improving the imager by pixel count and size can reduce positioning errors down to 1/120th of the pixel size, after which further improvements yield no reduction in error. Experiments using a modest complementary metal-oxide-semiconductor imager demonstrate a positioning accuracy of 1/124th of the pixel size, or 29 nm. This system will enable high-precision high-throughput metrology and fabrication of nano- and microelectromechanical systems. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Accurate Surface-to-Bulk Feature Alignment and Feature Size Preservation During Double-Sided Wafer Processing Using \hbox {C}_{4}\hbox {F}_{8} Plasma Polymer for the Fabrication of Electrostatically Actuated Cantilever Devices

    Publication Year: 2010 , Page(s): 871 - 877
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (955 KB) |  | HTML iconHTML  

    An accurate alignment of surface-to-bulk features (within ±2 μm) during a double-sided silicon wafer processing can be extremely difficult. This is due to a combination of mask misalignment errors and unreliability of bulk etching techniques in translating the bulk feature shapes down to the surface side. In this paper, we present a fabrication process for an electrostatically actuated cantilever device where an accurate surface-to-bulk feature alignment is imperative to the operation of the device. The fabrication process compensates for the bulk etch-induced feature size variation and mask misalignment errors using a combination of self-aligning features and C4F8 plasma polymer passivation. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A Flat Heat Pipe Architecture Based on Nanostructured Titania

    Publication Year: 2010 , Page(s): 878 - 884
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (667 KB) |  | HTML iconHTML  

    A novel 3 cm × 3 cm × 600 μm-thick Ti-based flat heat pipe is developed for Thermal Ground Plane (TGP) applications. The Ti-based heat pipe architecture is constructed by laser welding two microfabricated titanium substrates to form a hermetically sealed vapor chamber. The scalable heat pipes' flat geometry facilitates contact with planar heat sources, such as microprocessor chip surfaces, thereby reducing thermal contact resistance and improving system packaging. Fluid transport is driven by the wicking structure in the TGP, which consists of an array of Ti pillars that are microfabricated from a titanium substrate using recently developed high-aspect-ratio Ti processing techniques. The hydrophilic nature of the Ti pillars is increased further by growing ~200-nm hairlike nanostructured titania of the pillar surfaces. The resulting super hydrophilic wick offers the potential to generate high wicking velocities of ~27.5 mm/s over distances of 2 mm. The experimental wetting results show a diffusive spreading behavior that is predicted by Washburn dynamics. The maximum effective thermal conductivity of a heat pipe is directly related to the speed of capillary flow of the working fluid through the wick and is measured experimentally in the first-generation device to be k = 350 W/m · K. A dummy TGP with a cavity volume of ~170 μL was used to test the hermiticity level of the laser packaging technique. The device gave a 0.067% of water loss based on ~60 μL of charged water at 100°C in air for over a year. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • The Nanoaquarium: A Platform for In Situ Transmission Electron Microscopy in Liquid Media

    Publication Year: 2010 , Page(s): 885 - 894
    Cited by:  Papers (25)
    Multimedia
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (845 KB) |  | HTML iconHTML  

    Transmission electron microscopes (TEMs) and scanning transmission electron microscopes (STEMs) are powerful tools for imaging on the nanoscale. These microscopes cannot be typically used to image processes taking place in liquid media because liquid simply evaporates in the high-vacuum environment of the microscope. In order to view a liquid sample, it is thus necessary to confine the liquid in a sealed vessel to prevent evaporation. Additionally, the liquid layer must be very thin to minimize electron scattering by the suspending medium. To address these issues, we have developed a flow cell with a height of tens of nanometers, sandwiched between two thin silicon nitride membranes. The cell is equipped with electrodes for actuation and sensing. The cell is thin enough to allow the transmission of electrons and the real-time imaging of nanoparticles suspended in liquid. This paper details the fabrication process, which relies on plasma-activated wafer bonding. Some of the advantages of our nanoaquarium include the thinnest observation chamber of any reported in situ TEM/STEM device, integrated electrodes for sensing and actuation, and wafer-scale processing that allows bulk device production. Device performance was demonstrated by STEM imaging of gold and polystyrene nanoparticles suspended in water with excellent resolution. Potential applications of the device include imaging of colloidal crystal formation, aggregation, nanowire growth, electrochemical deposition, and biological interactions. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • The Thickness Difference Method for Measuring the Thermal Conductivity of Thick Films

    Publication Year: 2010 , Page(s): 895 - 902
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (683 KB) |  | HTML iconHTML  

    A new experimental method, named the thickness difference method, is proposed for measuring the thermal conductivity of thick films. This method is developed based on a logarithmic relation regarding the difference of the total thermal resistances and the ratio of the film thicknesses between two similar systems. Such a logarithmic relation is supported by theoretical analysis and is analogous to that appearing in the steady heat diffusion problem between two concentric cylinders. Its accuracy is confirmed to be acceptable when the film thickness is large enough compared to the heating-wire width and small enough compared to the substrate width. The error analysis shows that the relative errors are under 1% for all film Biot numbers greater than 60. Finally, an associated experiment is also set up, and the measurement results confirm the accuracy of the proposed thickness difference method. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Accurate Temperature Monitoring in Laser-Assisted Polymer Bonding for MEMS Packaging Using an Embedded Microsensor Array

    Publication Year: 2010 , Page(s): 903 - 910
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1137 KB) |  | HTML iconHTML  

    This paper presents an experimental study of an accurate temperature-monitoring method using an embedded thin-film microsensor array for laser-assisted polymer bonding for MEMS packaging. The work is carried out using a fiber-coupled diode laser system and benzocyclobutene polymer as the bonding material. Beam-forming optical elements are used to generate top-hat and frame-shaped beam profiles. Platinum-based sensor arrays are fabricated using sputtering and ion-beam etching methods. Peripheral sensors are embedded at the interface between the polymer sealing ring on the top (capping) substrate and the sensor substrate in the bonding process. The embedded peripheral sensors allow precise monitoring of the temperature profile of the polymer track in the laser-assisted thermal curing process for substrate bonding. The sensor at the center of the array can monitor the temperature that would be experienced by a MEMS device in a manufacturing environment. Results show that accurate temperature monitoring can be obtained using the embedded sensor array. A lower temperature than that required for bonding is seen at the center of the bottom (device) substrate. This is a highly desirable effect for packaging of temperature-sensitive devices. In addition, the effects of substrate material and arrangement of heat dissipation on the resultant temperature profiles have been investigated. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Device-Level Vacuum Packaging for RF MEMS

    Publication Year: 2010 , Page(s): 911 - 918
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (834 KB) |  | HTML iconHTML  

    For specific RF applications, where the use of MEMS is highly attractive, cost-effective reliable packaging is one of the primary barriers to commercialization. Many RF MEMS devices require a hermetic or vacuum operation environment. This paper presents a post-CMOS-compatible method for vacuum packaging of RF MEMS devices by growing an encapsulation layer during the device fabrication. The resulting MEMS devices are surrounded by a vacuum cavity and can then be placed in a conventional low-cost circuit package. This is a low-temperature area-efficient device-level encapsulation for MEMS devices. RF MEMS resonators in a fixed-fixed configuration were used as the test bed since their quality factor can be used as a measure of the package quality. The encapsulation process is based on a double-sacrificial-layer surface micromachining technique, which is used to create a cavity under and above the resonator. Polyimide was used as the sacrificial layer, followed by the deposition of a packaging layer with trench cuts, which facilitate the sacrificial layer removal. The trench cuts were then sealed at a low pressure, forming a cavity around the device at the sealant layer deposition pressure. Extensive RF characterization and reliability tests were performed on the packaged resonators. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A Versatile Integration Technology of SOI-MEMS/CMOS Devices Using Microbridge Interconnection Structures

    Publication Year: 2010 , Page(s): 919 - 926
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1212 KB) |  | HTML iconHTML  

    In this paper, a versatile integration technology for thick-film silicon-on-insulator microelectromechanical systems (SOI-MEMS) devices with CMOS electronics using novel microbridge interconnections is reported. The microbridge interconnection proposed in this paper solves the problem regarding the electrical isolation and interconnection between CMOS and SOI-MEMS devices. The integration of SOI-MEMS requires only three additional photolithography steps for the CMOS wafers fabricated by a standard process. On the basis of the developed technology, SOI-MEMS devices integrated with CMOS circuits were fabricated using 20-μm-thick SOI wafers. No significant damage was observed in the measured characteristics of the fabricated CMOS after the integration of MEMS devices. In addition, the electrical isolation of SOI-MEMS from the CMOS substrate was successfully realized and confirmed in the experiment, keeping electrical connectivity between CMOS circuit terminals. The measured isolation resistance between MEMS and the CMOS substrate was more than 1012 Ω, and a proof voltage above 60 Vdc was observed. These values guarantee a small leakage current and a sufficient voltage swing for driving electrostatic microactuators. On the other hand, the resistance of the interconnection over a microbridge structure was below 1 Ω, which is sufficiently low for integrating low-noise microsensors. This integration technology can be used in realizing monolithically integrated SOI-MEMS sensor and actuator devices with high-aspect-ratio structures using the most cost-effective and versatile CMOS fabrication technologies. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Compact Low-Voltage Operation Micromirror Based on High-Vacuum Seal Technology Using Metal Can

    Publication Year: 2010 , Page(s): 927 - 935
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (970 KB) |  | HTML iconHTML  

    In this paper, we present the design, fabrication, and vacuum package of an electrostatic comb-drive resonant micromirror. The micromirror having a high resonant frequency suitable for a laser scanning display was fabricated using a silicon-on-insulator (SOI) wafer. An individual die which was an array of four micromirrors with a total size of 5.5 × 5.5 mm2 was diced from the SOI wafer by dry etching. The die was packaged in a transistor-outline-8 metal can with a window in a vacuum-packaging machine at a pressure of 10-4 Pa. To evacuate the residual gases generated after the package process, a nonevaporable getter was used in the metal can. The resonant frequencies of the fabricated micromirrors were 13 and 25 kHz, respectively. An optical rotation angle of about 10° was achieved at a low driving voltage of 5 V. Due to the decrease of air-friction loss, the operation voltage decreased by a factor of 32 compared with the voltage operated at atmospheric pressure. The operation pressure in the vacuum package was evaluated to be about 0.7 Pa from the amplitude and quality factor of the mirror oscillation. Moreover, several properties, such as the surface profile of the micromirror, were evaluated before and after the packaging. The durability of the packaged mirror was tested at temperatures of up to 75°C. The theoretical explanations about air friction were also described. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.

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