By Topic

Microelectromechanical Systems, Journal of

Issue 1 • Date Feb. 2006

Filter Results

Displaying Results 1 - 25 of 33
  • Table of contents

    Page(s): c1 - c4
    Save to Project icon | Request Permissions | PDF file iconPDF (33 KB)  
    Freely Available from IEEE
  • Journal of Microelectromechanical Systems publication information

    Page(s): c2
    Save to Project icon | Request Permissions | PDF file iconPDF (35 KB)  
    Freely Available from IEEE
  • An untethered, electrostatic, globally controllable MEMS micro-robot

    Page(s): 1 - 15
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1752 KB)  

    We present an untethered, electrostatic, MEMS micro-robot, with dimensions of 60 μm by 250 μm by 10 μm. The device consists of a curved, cantilevered steering arm, mounted on an untethered scratch drive actuator (USDA). These two components are fabricated monolithically from the same sheet of conductive polysilicon, and receive a common power and control signal through a capacitive coupling with an underlying electrical grid. All locations on the grid receive the same power and control signal, so that the devices can be operated without knowledge of their position on the substrate. Individual control of the component actuators provides two distinct motion gaits (forward motion and turning), which together allow full coverage of a planar workspace. These MEMS micro-robots demonstrate turning error of less than 3.7°/mm during forward motion, turn with radii as small as 176 μm, and achieve speeds of over 200 μm/sec with an average step size as small as 12 nm. They have been shown to operate open-loop for distances exceeding 35 cm without failure, and can be controlled through teleoperation to navigate complex paths. The devices were fabricated through a multiuser surface micromachining process, and were postprocessed to add a patterned layer of tensile chromium, which curls the steering arms upward. After sacrificial release, the devices were transferred with a vacuum microprobe to the electrical grid for testing. This grid consists of a silicon substrate coated with 13-μm microfabricated electrodes, arranged in an interdigitated fashion with 2-μm spaces. The electrodes are insulated by a layer of electron-beam-evaporated zirconium dioxide, so that devices placed on top of the electrodes will experience an electrostatic force in response to an applied voltage. Control waveforms are broadcast to the device through the capacitive power coupling, and are decoded by the electromechanical response of the device body. Hysteresis in the system allows on-board storage of n=2 bits of state information in response to these electrical signals. The presence of on-board state information within the device itself allows each of the two device subsystems (USDA and steering arm) to be individually addressed and controlled- . We describe this communication and control strategy and show necessary and sufficient conditions for voltage-selective actuation of all 2n system states, both for our devices (n=2), and for the more general case (where n is larger.). View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Latching micromagnetic optical switch

    Page(s): 16 - 23
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1232 KB) |  | HTML iconHTML  

    In this paper, we report a new type of latching micromagnetic optical switch. The key component of this optical switch is a cantilever made of soft magnetic material with a reflective surface serving as a mirror. The cantilever has two stable positions, therefore two stable states for the device, with presence of an external magnetic field. Input optical signal to the device is switched selectively to one of the two output ports when the device transitions between the two states upon short electromagnetic actuations. The optical switch is bistable because the cantilever has a tendency to align with the external magnetic field, and the torque to align the cantilever can be bidirectional depending on the angle between the cantilever and the magnetic field. Switching between the two stable states is accomplished by momentarily changing the direction and/or the magnitude of the cantilever's magnetization by passing a short current pulse through a planar coil underneath the cantilever. In either of its stable state, the cantilever is held in position by the combined influence of the static external magnetic field and mechanical force, such as from a physical stopper or a mechanical torque produced by the torsion flexures supporting the cantilever. Stable vertical position for the cantilever is obtained by using a tilted external magnetic field. When the cantilever mirror is at this UP state, light is reflected to the desired output port. Large angle deflection and bistable latching operations have been demonstrated. The measured mechanical switching speed between the two states of the prototype is 3.2 ms. Optical insertion loss is -4 dB, and the energy consumption is 44 mJ for each switching event. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Scanning micromirrors fabricated by an SOI/SOI wafer-bonding process

    Page(s): 24 - 32
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1344 KB) |  | HTML iconHTML  

    MEMS scanning micromirrors have been proposed to steer a modulated laser beam in order to establish secure optical links between rapidly moving platforms. An SOI/SOI wafer-bonding process has been developed to fabricate scanning micromirrors using lateral actuation. The process is an extension of established SOI technology and can be used to fabricate stacked high-aspect-ratio structures with well-controlled thicknesses. Fabricated one-axis micromirrors scan up to 21.8° optically under a dc actuation voltage of 75.0 V, and have a resonant frequency of 3.6 kHz. Fabricated two-axis micromirrors scan up to 15.9° optically on the inner axis at 71.8 V and 13.2° on the outer axis at 71.2 V. The micromirrors are observed to be quite durable and resistant to shocks. Torsional beams with T-shaped cross sections are introduced to replace rectangular torsional beams in two-axis MEMS micromirrors, in order to reduce the cross-coupling between the two axial rotations. Fabricated bidirectional two-axis micromirrors scan up to ±7° on the outer-axis and from -3° to 7° on the inner-axis under dc actuation. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Robust design and model validation of nonlinear compliant micromechanisms

    Page(s): 33 - 41
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (624 KB) |  | HTML iconHTML  

    Although the use of compliance or elastic flexibility in microelectromechanical systems (MEMS) helps eliminate friction, wear, and backlash, compliant MEMS are known to be sensitive to variations in material properties and feature geometry, resulting in large uncertainties in performance. This paper proposes an approach for design stage uncertainty analysis, model validation, and robust optimization of nonlinear MEMS to account for critical process uncertainties including residual stress, layer thicknesses, edge bias, and material stiffness. A fully compliant bistable micromechanism (FCBM) is used as an example, demonstrating that the approach can be used to handle complex devices involving nonlinear finite element models. The general shape of the force-displacement curve is validated by comparing the uncertainty predictions to measurements obtained from in situ force gauges. A robust design is presented, where simulations show that the estimated force variation at the point of interest may be reduced from ±47 μN to ±3 μN. The reduced sensitivity to process variations is experimentally validated by measuring the second stable position at multiple locations on a wafer. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Buckling and free oscillations of composite microresonators

    Page(s): 42 - 51
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1000 KB) |  | HTML iconHTML  

    Free oscillations of piezoelectric, microelectromechanical resonators are considered in this effort. These resonators are modeled as clamped-clamped composite structures, with stepwise varying properties across the length of the resonator. The different features of the model development are discussed, and buckling in these resonators is studied. A nonlinear analysis conducted to study oscillations about a buckled position is presented. The results of the analysis are found to compare well with the experimental observations. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Built-in self-test of MEMS accelerometers

    Page(s): 52 - 68
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (616 KB) |  | HTML iconHTML  

    A built-in self-test technique that is applicable to symmetric microsystems is described. A combination of existing layout features and additional circuitry is used to make measurements from symmetrically located points. In addition to the normal sense output, self-test outputs are used to detect the presence of layout asymmetry that are caused by local, hard-to-detect defects. Simulation results for an accelerometer reveal that our self-test approach is able to distinguish misbehavior resulting from local defects and global manufacturing process variations. A mathematical model is developed to analyze the efficacy of the differential built-in self-test method in characterization of a wide range of local manufacturing variations affecting different regions of a device and/or wafer. Model predictions are validated by simulation. Specifically, it has been shown that by using a suitable modulation scheme, sensitivity to etch variation along a particular direction is improved by nearly 30%. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Using dynamic voltage drive in a parallel-plate electrostatic actuator for full-gap travel range and positioning

    Page(s): 69 - 83
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4416 KB)  

    The nonlinear dynamics of the parallel-plate electrostatically driven microstructure have been investigated with the objective of finding a dynamic voltage drive suitable for full-gap operation. Nonlinear dynamic modeling with phase-portrait presentation of both position and velocity of a realistic microstructure demonstrate that instability is avoided by a timely and sufficient reduction of the drive voltage. The simulation results are confirmed by experiments on devices fabricated in an epi-poly process. A 5.5-V peak harmonic drive voltage with frequency higher than 300 Hz allows repetitive microstructure motion up to 70% of gap without position feedback. The results of the analysis have been applied to the design of a new concept for positioning beyond the static pull-in limitation that does include position feedback. The measured instantaneous actuator displacement is compared with the desired displacement setting and, unlike traditional feedback, the voltage applied to the actuator is changed according to the comparison result between two values. The "low" level is below the static pull-in voltage and opposes the motion, thus bringing the structure back into a stable regime, while the "high" level is larger than the static pull-in voltage and will push the structure beyond the static pull-in displacement. Operation is limited only by the position jitter due to the time delay introduced by the readout circuits. Measurements confirm flexible operation up to a mechanical stopper positioned at 2 μm of the 2.25 μm wide gap with a 30 nm ripple. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Antistick postpassivation of high-aspect ratio silicon molds fabricated by deep-reactive ion etching

    Page(s): 84 - 93
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4992 KB)  

    High-aspect ratio (HAR) silicon molds formed with deep-reactive ion etching (DRIE) technique are difficult to use as masters for replication, especially for replication of high-aspect ratio microstructures. Microstructures in silicon molds made by DRIE have high surface energy and wavy vertical side walls, both of which make demolding difficult. In the research reported here, microstructured silicon master molds were made with the DRIE technique; the mold microstructures were "trenches" with maximum depth and width of 146 μm and 9.8 μm, respectively. Silicone rubber replicas could not be successfully demolded from such a high aspect ratio (15) silicon master without further surface modification. A second similarly etched mold was plasma treated with C4F8 for 120 seconds after etching (postpassivated). This treatment was found to be successful; five faithful replicas in silicone rubber were successfully demolded from the postpassivated mold whereas the replica mold broke during demolding from the unpostpassivated master, leaving the master mold microstructure filled with silicone rubber. At higher aspect ratio of 18, the silicon mold had to be plasma treated with C4F8 for at least 400 s before five replicas could be demolded successfully. Post-passivation with C4F8 was found to reduce the root mean square sidewall roughness of the silicon master mold trenches by about halves. The nanotribology of the silicon surface was studied with atomic force microscopy. The friction coefficient of the silicon surface was found to be reduced six-fold by the postpassivation technique. XPS analyzes showed that when post-passivation timing was increased, concentration of C-F increased while that of C-CF decreased and the thickness of the fluorinated coating increased. These results show that postpassivation of silicon microstructures made by DRIE can be used to fabricate much higher aspect ratio molds that has heretofore been considered possible using this substrate material and fabrication technique. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Electrochemical process for the lamination of magnetic cores in thin-film magnetic components

    Page(s): 94 - 100
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1600 KB) |  | HTML iconHTML  

    The lamination of the core in thin film magnetic components is necessary to reduce the eddy current losses of the structure at high frequencies. The usual way to achieve lamination of the core is by physical vapor deposition (PVD) techniques. These methods are however costly and the deposition of layers is non selective. In this article, an almost entirely aqueous-based electrochemical process for the lamination of magnetic cores is presented. The process uses an electrodepositable photoresist Eagle 2100 ED codeposited with a catalyst (palladium). The Eagle layer is left as an insulator and the catalyst allows the activation of the layer for subsequent metallization. The process can be reproduced as many times as required for producing the multilayers. It is also selective: it does not require multiple photolithography steps. As a demonstration of the multilayer process, a core constituted of two layers of Ni80Fe20 (6 μm each layer), separated by an Eagle insulating layer, electroplated over three-dimensional structures, was produced. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Impact behavior and energy transfer efficiency of pulse-driven bent-beam electrothermal actuators

    Page(s): 101 - 110
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1096 KB) |  | HTML iconHTML  

    This paper investigates the dynamics of bent-beam electrothermal actuators and their use in impact actuation of other micromechanical elements, and in particular the issue of energy efficiency achieved by temporal variations in electrical drive signals. A transient thermal model of an actuator beam shows that the uniformity of temperature profile is greater when activating with short electrical pulses, which results in larger achievable displacements and forces. A dynamic force analysis reveals that using a train of pulses, referred to as a burst pulse, for activation achieves significant impact forces due to high velocities at the point of impact. The analytical trends are confirmed through experimental observations of microfabricated metal test structures in which actuators work against bistable mechanisms. Measurements of 2 mm and 3mm long actuators show that pulsed activation results in >5× reduction in energy consumption, with the activation energy falling from over 1000 μJ at dc activation, to less than 200 μJ using a 0.2-ms voltage pulse. The actuators however consume higher instantaneous power levels at shorter pulses, which may inhibit the use of pulses less than 1 ms in width. Further, the energy consumption through burst activation is 70% that of a single pulse, if sufficient impact forces are generated. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • The critical role of environment in fatigue damage accumulation in deep-reactive ion-etched single-crystal silicon structural films

    Page(s): 111 - 119
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1344 KB) |  | HTML iconHTML  

    The importance of service environment to the fatigue resistance of n+-type, 10 μm thick, deep-reactive ion-etched (DRIE) silicon structural films used in microelectromechanical systems (MEMS) was characterized by testing of electrostatically actuated resonators (natural frequency, f0, ∼40 kHz) in controlled atmospheres. Stress-life (S-N) fatigue tests conducted in 30°C, 50% relative humidity (R.H.) air demonstrated the fatigue susceptibility of silicon films. Further characterization of the films in medium vacuum and 25% R.H. air at various stress amplitudes revealed that the rates of fatigue damage accumulation (measured via resonant frequency changes) are strongly sensitive to both stress amplitude and, more importantly, humidity. Scanning electron microscopy of high-cycle fatigue fracture surfaces (cycles to failure, Nf>1×109) revealed clear failure origins that were not observed in short-life (Nf<1×104) specimens. Reaction-layer and microcracking mechanisms for fatigue of silicon films are discussed in light of this empirical evidence for the critical role of service environment during damage accumulation under cyclic loading conditions. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Piezo-FET stress-sensor arrays for wire-bonding characterization

    Page(s): 120 - 130
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1488 KB) |  | HTML iconHTML  

    This paper reports the design, fabrication, and characterization of a two-dimensional stress-sensor array based on a stress-sensor element exploiting the transverse pseudo-Hall effect in metal-oxide-semiconductor (MOS) field effect transistors (FET). P-channel MOS (PMOS) devices were integrated in a 4×4 stress sensor array with a total area of 120×120 μm2. The individual elements of the array are sensitive to the local shear stress in the chip plane. They are selected using a CMOS integrated digital decoder and transmission gates. The new array was characterized using a commercial ball-wedge wire bonding tool and was used for the in situ monitoring of the bonding process. The spatially resolved measurement of the stress distribution underneath and close to a bond pad during the bond wire touch-down is demonstrated. The array is able to resolve variations in the touch-down position of 10 μm. The time of 1.6 ms for acquisition of a full frame is currently limited by the experimental setup. To monitor the stress distribution during the bonding process, an aluminum covered stress sensor array similar to a standard bond pad was used. The successful bond formation between a gold ball and the metal bond pad was observed. The bond formation becomes evident as a characteristic, concentrated stress profile with large peak value appearing within 20 ms. The maximum stresses underneath the successfully bonded area exceeds stress levels in unbonded sensor locations by a factor of up to 60. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • On the dynamic pull-in of electrostatic actuators with multiple degrees of freedom and multiple voltage sources

    Page(s): 131 - 140
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (544 KB) |  | HTML iconHTML  

    This study considers the dynamic response of electrostatic actuators with multiple degrees of freedom that are driven by multiple voltage sources. The critical values of the applied voltages beyond which the dynamic response becomes unstable are investigated. A methodology for extracting a lower bound for this dynamic pull-in voltage is proposed. This lower bound is based on the stable and unstable static response of the system, and can be rapidly extracted because it does not require time integration of momentum equations. As example problems, the dynamic pull-in of two prevalent electrostatic actuators is analyzed. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Third-order intermodulation in microelectromechanical filters coupled with capacitive transducers

    Page(s): 141 - 148
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (504 KB)  

    Third-order intermodulation in capacitively coupled microelectromechanical filters is analyzed. Parallel-plate transducers are assumed and, in addition to the capacitive nonlinearities, also the usually much weaker second- and third-order mechanical resonator nonlinearities are taken into account. Closed-form expressions for the output signal-to-interference ratio (SIR) and input intercept point are derived. The analytical results are verified in experiments and in numerical harmonic-balance simulations. It is shown that intermodulation as a function of frequency is asymmetric with respect to the passband. The results are valuable in designing micromechanical filters, for example, for communication applications. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Performance improvement of an electrothermal microactuator fabricated using Ni-diamond nanocomposite

    Page(s): 149 - 158
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1360 KB) |  | HTML iconHTML  

    In this paper, a low-temperature stress-free electrolytic nickel (EL) deposition process with added dispersed diamond nanoparticles (diameter <0.5 μm) is developed to synthesize Ni-diamond nanocomposite for fabricating electrothermal microactuators. Device characterization reveals dramatic performance improvements in the electrothermal microactuator that is made of the nanocomposite, including a reduction in the input power requirement and enhanced operation reliability. In comparison with the microactuator made of pure nickel, the nanocomposite one can save about 73% the power for a 3 μm output displacement and have a longer reversible displacement range, which is prolonged from 1.8 μm to more than 3 μm. Furthermore, the nanocomposite device exhibits no performance degradation after more than 100 testing cycles in the reversible regime. The enhancements increase with the incorporation of the nanodiamond in a nickel matrix, so the Ni-diamond nanocomposite has potential for application in MEMS fabrication. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Validation of X-ray lithography and development simulation system for moving mask deep X-ray lithography

    Page(s): 159 - 168
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (904 KB) |  | HTML iconHTML  

    This paper presents a newly developed 3-Dimensional (3-D) simulation system for Moving Mask Deep X-ray Lithography (M2DXL) technique, and its validation. The simulation system named X-ray Lithography Simulation System for 3-Dimensional Fabrication (X3D) is tailored to simulate a fabrication process of 3-D microstructures by M2DXL. X3D consists of three modules: mask generation, exposure and resist development (hereafter development). The exposure module calculates a dose distribution in resist using an X-ray mask pattern and its movement trajectory. The dose is then converted to a resist dissolution rate. The development module adopted the "Fast Marching Method" technique to calculate the 3-D dissolution process and resultant 3-D microstructures. This technique takes into account resist dissolution direction that is required by 3-D X-ray lithography simulation. The comparison between simulation results and measurements of "stairs-like" dose deposition pattern by M2DXL showed that X3D correctly predicts the 3-D dissolution process of exposed PMMA. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Development of AFM tensile test technique for evaluating mechanical properties of sub-micron thick DLC films

    Page(s): 169 - 180
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1712 KB) |  | HTML iconHTML  

    This paper describes mechanical properties of submicron thick diamond-like carbon (DLC) films used for surface modification in MEMS devices. A new compact tensile tester operating under an atomic force microscope (AFM) is developed to measure Young's modulus, Poisson's ratio and fracture strength of single crystal silicon (SCS) and DLC coated SCS (DLC/SCS) specimens. DLC films with a thickness ranging from 0.11 μm to 0.58 μm are deposited on 19-μm-thick SCS substrate by plasma-enhanced chemical vapor deposition using a hot cathode penning ionization gauge discharge. Young's moduli of the DLC films deposited at bias voltages of -100 V and -300 V are found to be constant at 102 GPa and 121 GPa, respectively, regardless of film thickness. Poisson's ratio of DLC film is also independent of film thickness, whereas fracture strength of DLC/SCS specimens is inversely proportional to thickness. Raman spectroscopy analyses are performed to examine the effect of hydrogen content in DLC films on elastic properties. Raman spectra reveal that a reduction in hydrogen content in the films leads to better elastic properties. Finally, the proposed evaluation techniques are shown to be applicable to sub-micron thick DLC films by finite element analyses. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Transient heat transfer and gas flow in a MEMS-based thruster

    Page(s): 181 - 194
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (904 KB) |  | HTML iconHTML  

    Time-dependent performance of a high-temperature MEMS-based thruster is studied in detail by a coupled thermal-fluid analysis. The material thermal response governed by the transient heat conduction equation is obtained using the finite element method. The low-Reynolds number gas flow in the microthruster is modeled by the direct simulation Monte Carlo (DSMC) approach. The temporal variation of the thruster material temperature and gas flowfields are obtained as well as the thruster operational time limits for thermally insulated and convectively cooled thrusters. The predicted thrust and mass discharge coefficient of both two-dimensional (2-D) and three-dimensional (3-D) micronozzles decreases in time as the viscous losses increase for higher wall temperatures. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • High-energy density miniature thermoelectric generator using catalytic combustion

    Page(s): 195 - 203
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (976 KB) |  | HTML iconHTML  

    This paper describes the components and system of a thermoelectric (TE) generator with a catalytic butane combustor. The combustion chamber with a size of 8 mm×8 mm×0.4 mm is etched in a 0.65-mm-thick silicon substrate, and bonded to both sides of a 0.77-mm-thick glass substrate with a thin-film ignition heater. A set of 34 couples of BiTe TE elements, each with a size of 0.65 mm×0.65 mm×2 mm, are directly bonded to both sides of the combustor. The combustor without the TE modules was tested using butane as fuel, and self-sustaining combustion and electrical ignition were achieved. Also, nearly 100% combustion efficiency and a uniform temperature distribution were confirmed by gas chromatography and infrared thermoimaging, respectively. When the TE modules were attached to the combustor, however, butane combustion was impossible. The characteristics of TE generation were measured using hydrogen as fuel. When a theoretical combustion power was 6.6 W, the maximum output power of 184 mW was obtained with a load of 5.68 Ω. The total efficiency in this experiment was 2.8% (184 mW/6.6 W). View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Design and fabrication of a novel microfluidic nanoprobe

    Page(s): 204 - 213
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2408 KB)  

    The design and fabrication of a novel microfluidic nanoprobe system are presented. The nanoprobe consists of cantilevered ultrasharp volcano-like tips, with microfluidic capabilities consisting of microchannels connected to an on-chip reservoir. The chip possesses additional connection capabilities to a remote reservoir. The fabrication uses standard surface micromachining techniques and materials. Bulk micromachining is employed for chip release. The microchannels are fabricated in silicon nitride by a new methodology, based on edge underetching of a sacrificial layer, bird's beak oxidation for mechanically closing the edges, and deposition of a sealing layer. The design and integration of various elements of the system and their fabrication are discussed. The system is conceived mainly to work as a "nanofountain pen", i.e., a continuously writing upgrade of the dip-pen nanolithography approach. Moreover, the new chip shows a much larger applicability area in fields such as electrochemical nanoprobes, nanoprobe-based etching, build-up tools for nanofabrication, or a probe for materials interactive analysis. Preliminary tests for writing and imaging with the new device were performed. These tests illustrate the capabilities of the new device and demonstrate possible directions for improvement. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Design and fabrication of a micromachined planar patch-clamp substrate with integrated microfluidics for single-cell measurements

    Page(s): 214 - 222
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1856 KB)  

    We have designed, fabricated, tested, and integrated microfabricated planar patch-clamp substrates and poly(dimethylsiloxane) (PDMS) microfluidic components. Substrates with cell-patch-site aperture diameters ranging from 300nm to 12 μm were produced using standard MEMS-fabrication techniques. The resistance of the cell-patch sites and substrate capacitance were measured using impedance spectroscopy. The resistance of the microfabricated apertures ranged from 200 kΩ to 47 MΩ for apertures ranging from 12 μm to 750 nm, respectively. The substrate capacitance was 17.2 pF per mm2 of fluid contact area for substrates with a 2-μm-thick layer of silicon dioxide. In addition, the ability of the planar patch-clamp substrates to form high-resistance seals in excess of 1 GΩ has been confirmed using Chinese hamster ovary cells (CHO-K1). Testing shows that the microfluidic components are appropriate for driving human embryonic kidney cells (HEK 293) to patch apertures, for trapping cells on patch apertures, and for exchanging the extracellular fluid environment. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A continuous-flow polymerase chain reaction microchip with regional velocity control

    Page(s): 223 - 236
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1616 KB)  

    This paper presents a continuous-flow polymerase chain reaction (PCR) microchip with a serpentine microchannel of varying width for "regional velocity control." Varying the channel width by incorporating expanding and contracting conduits made it possible to control DNA sample velocities for the optimization of the exposure times of the sample to each temperature phase while minimizing the transitional periods during temperature transitions. A finite element analysis (FEA) and semi-analytical heat transfer model was used to determine the distances between the three heating assemblies that are responsible for creating the denaturation (96°C), hybridization (60°C), and extension (72°C) temperature zones within the microchip. Predictions from the thermal FEA and semi-analytical model were compared with temperature measurements obtained from an infrared (IR) camera. Flow-field FEAs were also performed to predict the velocity distributions in the regions of the expanding and contracting conduits to study the effects of the microchannel geometry on flow recirculation and bubble nucleation. The flow fields were empirically studied using micro particle image velocimetry (μ-PIV) to validate the flow-field FEA's and to determine experimental velocities in each of the regions of different width. Successful amplification of a 90 base pair (bp) bacillus anthracis DNA fragment was achieved. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Spatially controlled microfluidics using low-voltage electrokinetics

    Page(s): 237 - 245
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (904 KB) |  | HTML iconHTML  

    Most electrokinetic microfluidic devices currently require high voltages (>50 V) to generate sustained electric fields. However, two long-standing limitations remain, namely: (i) the resulting electrolysis of water produces bubbles, forcing electrodes to be placed in reservoirs outside the channels, and (ii) direct integration with low-voltage microelectronics cannot be achieved. A further limitation is the lack of spatial control within the microchannel. This work presents a method to achieve low-voltage (≤1 V) electrokinetic transport using micropatterned Ag-AgCl electrode arrays, which allows spatial flow control within microchannels. We demonstrate bidirectional electrophoretic control of microparticles within microfluidic channels using ±1 V. 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