http://ieeexplore.ieee.org TOC Alert for Publication# 84 2009 June 19 18 3 C1 C4 51 18 3 C2 C2 39 In this paper, we describe low-permeability components of a microfluidic drug delivery system fabricated with versatile micromilling and lamination techniques. The fabrication process uses laminate sheets which are machined using XY milling tables commonly used in the printed-circuit industry. This adaptable platform for polymer microfluidics readily accommodates integration with silicon-based sensors, printed-circuit, and surface-mount technologies. We have used these methods to build components used in a wearable liquid-drug delivery system for in vivo studies. The design, fabrication, and performance of membrane-based fluidic capacitors and manual screw valves provide detailed examples of the capability and limitations of the fabrication method. We demonstrate fluidic capacitances ranging from 0.015 to 0.15 $muhbox{L}$/kPa, screw valves with on/off flow ratios greater than 38 000, and a 45$times$ reduction in the aqueous fluid loss rate to the ambient due to permeation through a silicone diaphragm layer. $hfill$[2008-0148] ]]> 18 3 501 510 632 This paper describes the design, microfabrication, and testing of a novel polycrystalline-diamond (poly-C)-based microprobe for possible applications in neural prosthesis. The probe utilizes undoped poly-C with a resistivity on the order of $10^{5} Omegacdothbox{cm}$ as a supporting material, which has a Young's modulus in the range of 400–1000 GPa and is biocompatible. Boron-doped poly-C with a resistivity on the order of $10^{-3} Omegacdot hbox{cm}$ is used as an electrode material, which provides a chemically stable surface for both chemical and electrical detections in neural studies. The probe has eight poly-C electrode sites with diameters ranging from 2 to 150 $muhbox{m}$; the electrode capacitance is approximately 87 $muhbox{F/cm}^{2}$. The measured water potential window of the poly-C electrode spans across negative and positive electrode potentials and typically has a total value of 2.2 V in 1 M KCl. The smallest detectable concentration of norepinephrine (a neurotransmitter) was on the order of 10 nM. The poly-C probe has also been successfully implanted in the auditory cortex area of a guinea pig brain for in vivo neural studies. The recorded signal amplitude was 30–40 $muhbox{V}$ and had a duration of 1 ms. $hfill$[2008-0195] ]]> 18 3 511 521 1488 An 8-pixel micromachined quartz crystal resonator array with a fundamental resonance frequency of 66 MHz has been designed, fabricated, and tested. A compact impedance-spectrum-analyzer electronic interface has been developed and combined with the quartz resonator array to form the biosensing system. The sensor array was calibrated using water–glycerol solutions, and the performance was found to be exactly as expected. Measurement of the crosstalk between the sensor pixels showed an isolation of $sim$ 30 dB. Selective functionalization of the pixels was achieved through the use of aqueous 3, 3 $^{prime}$-Dithiobis (sulfosuccinimidylpropionate) (DTSSP) molecules. The adsorption of avidin on DTSSP gave a frequency signal of 60 kHz in comparison to unfunctionalized pixels. The specific adsorption of avidin on functionalized pixels was confirmed through fluorescence microscopy. Comparing the performance of the micromachined quartz crystal microbalance (QCM) with a commercial 5-MHz device, we found that the micromachined QCM has a 4.25 times higher signal-to-noise ratio. Based on the measurement of the noise and using three times the frequency noise as the limit for the detection of avidin molecules, we expect to resolve a minimum of $sim$1/960 of a monolayer of avidin corresponding to an aerial mass density resolution of 0.7 $hbox{ng/cm}^{2}$ .$hfill$[2008-0196] ]]> 18 3 522 530 1146 Precision engineering has been used in the macroworld and in the microscale only with rigid materials. Soft flexible materials commonly used for microfluidics and other bio-MEMS applications have not been aligned with elastic averaging. We report the use of complementary raised and recessed circular features to align polymer layers and demonstrate alignment accuracy and repeatability. The alignment is accomplished in a Petri dish with a thin layer of liquid between the two surfaces of micromolded elastomeric polymer sheets. The layers are aligned with simple hand–eye manipulation. We test circular geometries of varying diameters, obtaining accuracy and repeatability values in the range of 1–3 $muhbox{m}$ across thin polymer sheets molded from silicon masters. This is a significant improvement over existing manual, moving stage, and self-alignment techniques and a novel proof of concept that paves the way for complex 3-D polymer constructs.$hfill$ [2008-0093] ]]> 18 3 531 538 752 This paper presents a microfluidic device that can passively reduce fluctuations in an upstream fluid flow and generate a largely steady flow in a microfluidic system. The device features a series of compliant membranes that form deformable walls of a microchannel. For an incoming pulsatile flow, passive vibrations of the membranes allow the fluid to be accumulated for an overflow and discharged for an underflow, resulting in drastically reduced fluctuations in flow rate and pressure. A lumped-parameter model is developed to simulate the device characteristics, in which the coupling of membrane vibrations and fluid flow in individual channel sections associated with a single membrane is first represented by squeeze-film theory and inertia-free structural dynamics. The entire device is next represented as a system by connecting individual channel sections in series. The model is numerically solved, and the results agree with experiments. The theoretical and experimental results both show that a five-membrane device can stabilize a pulsating flow by a factor of about 20. These results also reveal that smaller average flow rate, smaller fluctuation, and higher fluctuation frequency lead to more effective flow stabilization. With these characteristics, the flow stabilizer can be used to obtain steady flow in microfluidic systems.$hfill$ [2008-0305] ]]> 18 3 539 546 875 The effect of asymmetry in the electrode geometry and interelectrode spacing on the performance of ion-drag-type electrohydrodynamic micropumps was studied. The micropumps consisted of chromium/gold planar electrodes on a glass substrate that was integrated within a polydimethylsiloxane microchannel that was 100 $muhbox{m}$ in height. The pumps were tested using HFE-7100 as the working fluid for the maximum-pressure generation under a no-flow condition and the maximum flow rate under a no-back-pressure condition. The micropumps with an asymmetric-electrode design, where the emitter and collector electrode widths were different, generated a significantly higher pressure head and flow rate than the corresponding micropumps with symmetric-electrode designs for the same applied voltage. The power consumption of the pumps with asymmetric electrodes was significantly lower than that with symmetric electrodes. $hfill$[2008-0217] ]]> 18 3 547 554 490 The measurement of the mechanical properties of materials with submicrometer dimensions is extremely challenging, from the preparation and manipulation of specimens to the application of small loads and extraction of accurate stresses and strains. A new on-chip nanomechanical testing concept has been developed in order to measure the mechanical properties of submicrometer freestanding thin films allowing various loading configurations and specimen geometries. The basic idea is to use internal stress present in one film to provide the actuation for deforming another film attached to the first film on one side and to the substrate on the other side. The measurement of the displacement resulting from the release of both films gives access to the stress and the strain applied to the test specimen provided the Young's modulus and mismatch strain of the actuator film are known. Classical microelectromechanical-systems-based microfabrication procedures are used to pattern the test structures and release the films from the substrate. The design procedures, data reduction scheme, and a generic fabrication strategy are described in details and implemented in order to build a suite of test structures with various combinations of dimensions. These structures allow the characterization of different materials and mechanical properties and enable high throughputs of data while avoiding any electrical signal or external actuation. Results obtained on ductile aluminum and brittle polysilicon films demonstrate the potential of the method to determine the Young's modulus, yield stress or fracture stress, fracture strain, and strain hardening in ductile materials. $hfill$[2008-0260] ]]> 18 3 555 569 1144 In order to evaluate the importance of stress relaxation on device performance of capacitive RF MEMS switches, stress relaxation has been measured in 1.2-$muhbox{m}$-thick Au films using a membrane bulge technique. When the residual stress in the films is small, the stress relaxation is fully recoverable and is well described by linear anelasticity (viscoelasticity) theory. A 27% reduction in the effective elastic modulus occurs over a three-day period under constant strain conditions at room temperature. The time dependence of the relaxation can be represented by a series of time constants with values extending from seconds to days. Linear superposition of the anelastic response can be used to accurately predict the stress under any time dependence of the strain. The prediction is accurate even during cyclic loading and unloading, and even when the strain is cycled at rates that are fast compared with any of the relaxation times. The restoring force available to open a capacitive RF MEMS switch is modeled for two different switch designs. The restoring force is shown to drop by approximately 7% or 20% at room temperature for the two cases presented. $hfill$[2008-0263] ]]> 18 3 570 576 460 A gas transport mechanism is studied to characterize the hermetic behavior of polymer-sealed microelectromechanical systems packages. Diffusion-based governing equations, which are fundamentally different from the conduction-based governing equations used for metallic seals, are proposed to predict a change in cavity pressure. An effective numerical scheme is developed to implement the governing equations. The validity of the governing equations is corroborated by the optical leak test. The verified gas diffusion model is utilized to investigate the effect of the diffusion properties and geometries of polymeric seals on the gas leak behavior. $hfill$[2008-0264] ]]> 18 3 577 587 1186 A thin-film encapsulation process, featuring low-temperature steps, hermetic sealing (preliminary), and RF-compatible shell, is reported. Uniquely attractive as compared with the existing MEMS packaging approaches is its capability to monolithically package metal microstructures inside a microcavity on chip in one continuous surface-micromachining process. The key for this process is a technique to fabricate a large freestanding porous membrane on chip by postdeposition anodization of thin-film aluminum at room temperature. The porous-alumina membrane allows for the diffusion of gas or liquid etchants through the nanopores to etch away the sacrificial material underneath, freeing the movable microstructures encapsulated inside the cavity. To seal the package, a thin film is deposited over the alumina shell whose nanoscale pores of a high aspect ratio $(≫ 30)$ do not allow any detectable penetration of the sealing material. The low-temperature $(≪ 300,^{circ}hbox{C})$ encapsulation process produced a low-pressure seal (8 torr), monitored by a Pirani pressure gauge that also represents an encapsulated freestanding metal microstructure in the cavity. The thin-film package demonstrated a considerably low RF insertion loss of less than 0.1 dB up to 40 GHz.$hfill$ [2007-0267] ]]> 18 3 588 596 1413 We present a theoretical and experimental investigation into the effect of the motion of a printed circuit board (PCB) on the response of microelectromechanical systems (MEMS) devices to shock loading. For the theoretical part, a 2-DOF model is used, where the first degree of freedom accounts for the PCB. The second degree of freedom represents the motion of the MEMS microstructure. Low-g acceleration pulses are applied to the MEMS–PCB assembly base to simulate shock pulses generated from a drop-table test. Simulation data are presented to show the effects of the natural frequency of the PCB, the natural frequency of the microstructure, and the shock pulse duration. Universal 3-D spectra representing the effect of these parameters are presented. It is found that neglecting the PCB effect on the design of MEMS devices under shock loads can lead to undesirable motion of their microstructures. The effects of electrostatic force and squeeze film damping are investigated. It is found that the amplification of motion due to the PCB can cause early pull-in instability for MEMS devices implementing electrostatic forces. The effect of higher order modes of a microbeam is studied through a continuous beam model coupled with a lumped model of the PCB. The limitations of the 2-DOF model are discussed. An experimental investigation is conducted to verify the theoretical results using a capacitive accelerometer. Experimental data for the response of the accelerometer while it is mounted on two representative PCBs due to different low-g shock conditions are shown.$hfill$[2008-0026] ]]> 18 3 597 609 1922 Piezoelectric $hbox{Pb}(hbox{Zr}, hbox{Ti})hbox{O}_{3}$ (PZT) thin films were directly deposited on cantilever-shaped titanium substrates and evaluated for their piezoelectric properties and actuator performance. Because of the small difference in the thermal expansion coefficient between the PZT and the substrate, and the mitigation of the residual stress, large piezoelectric properties could be obtained for PZT/Ti unimorph actuators. X-ray diffraction measurements clearly revealed that the PZT thin films have a polycrystalline perovskite structure with a random orientation. Observations using a scanning electron microscope (SEM) demonstrated that PZT films, which were 3.8 $mu hbox{m}$ thick, were densely deposited on Pt-coated Ti substrate without pores or cracks. The polarization–electric field ($P$– $E$) hysteresis of the PZT film clearly indicates ferroelectricity. The piezoelectric properties of the PZT films were evaluated from the tip displacement of PZT/Ti unimorph cantilevers. Simplified transverse piezoelectric coefficients ($e_{31}^{ ast} = d_{31}/s_{11}^{E}$, where $d_{31}$ and $s_{11}^{E}$ are piezoelectric coefficient and elastic compliance, respectively) were measured, which ranged from $-$3.6 to 4.3 $hbox{C}/hbox{m}^{2}$—about three times larger than those of the PZT thin films deposited on stainless-steel substrates. Measureme- - nt of resonant frequencies of the cantilevers shows a clear dependence on the cantilever length, which obeys the theoretical equation. This indicates that these cantilevers can be reliably applied as sensors and actuators in a resonance mode. $hfill$[2008-0100] ]]> 18 3 610 615 398 Microactuators provide controlled motion and force for applications ranging from radio frequency switches to microfluidic valves. Large amplitude response in piezoelectric actuators requires amplification of the small strain, exhibited by the piezoelectric material, used in the construction of such actuators. This paper studies a uniflex microactuator that combines the strain amplification mechanisms of a unimorph and flexural motion to produce large displacement and blocking force. The design and fabrication of the proposed uniflex microactuator are described in detail. An analytical model is developed with three connected beams and a reflective symmetric boundary condition that predicts actuator displacement and blocking force as a function of the applied voltage. The model shows that the uniflex design requires appropriate parameter ranges, particularly the clearance between the unimorph and aluminum cap, to ensure that both the unimorph and flexural amplification effects are realized. With a weakened joint at the unimorph/cap interface, the model is found to predict the displacement and blocking force for the actuators fabricated in this work.$hfill$[2008-0128] ]]> 18 3 616 625 1162 A small-signal model that describes the energy exchange between surface micromachined beams and bulk-lead zirconium titanate (PZT) actuators attached to the silicon substrate is presented. The model includes detection of acoustic waves launched from electrostatically actuated structures on the surface of the die, as well as their actuation by bulk waves generated by piezoelectric ceramics. The interaction is modeled via an empirical equivalent circuit, which is substantiated by experiments designed to extract the model parameters. The equivalent model is valid for cases where the beam resonance frequency is much smaller than the thickness mode resonance of the PZT/silicon stack. In this paper, the resonance frequency of the beams ranges between 200 and 300 kHz. As energy transfer between bulk-PZT and electrostatic actuated beam resonators must be reciprocal for small signals, this paper uses the extracted equivalent model to describe the physical sources of error that account for discrepancies in reciprocity.$hfill$[2008-0131] ]]> 18 3 626 640 2518 This paper presents the design, analysis, fabrication, and characterization of an active cantilever device integrated with a high-bandwidth 2-DOF translational $(XY)$ micropositioning stage. The cantilever is actuated electrostatically through a separate electrode that is fabricated underneath the cantilever. Torsion bars that connect the cantilever to the rest of the structure provide the required compliance for the cantilever's out-of-plane rotation. The active cantilever is carried by a micropositioning stage, which enables high-bandwidth scanning to allow manipulation in three dimensions. The design of the microelectromechanical system stage is based on a parallel kinematic mechanism (PKM). The PKM design decouples the motion in the $X$- and $Y$-directions while allowing for an increased motion range with linear kinematics in the operating region (or workspace). The trusslike structure of the PKM also results in increased stiffness and reduced mass of the stage. The integrated cantilever device is fabricated on a silicon-on-insulator (SOI) wafer using surface micromachining and deep reactive ion etching processes. The actuation electrode of the cantilever is fabricated on the handle layer, while the cantilever and the $XY$ stage are at the device layer of the SOI wafer. Two sets of electrostatic linear comb drives are used to actuate the stage mechanism in the $X$- and $Y$-directions. The cantilever provides an out-of-plane motion of 7 $muhbox{m}$ at 4.5 V, while the <- - tex Notation="TeX">$XY$ stage provides a motion range of 24 $muhbox{m}$ in each direction at the driving voltage of 180 V. The resonant frequency of the $XY$ stage under ambient conditions is 2090 Hz. A high quality factor ($sim$210) is achieved from this parallel kinematic $XY$ stage. The fabricated stages will be adapted as chip-scale manufacturing and metrology devices for nanomanufacturing and nanometrology applications. $hfill$[2008-0278] ]]> 18 3 641 651 1162 Due to force scaling laws, large adhesion forces at the microscale make rapid accurate release of microobjects a long-standing challenge in pick–place micromanipulation. This paper presents a new microelectromechanical systems (MEMS) microgripper integrated with a plunging mechanism to impact the microobject for it to gain sufficient momentum to overcome adhesion forces. The performance was experimentally quantified through the manipulation of 7.5–10.9-$muhbox{m}$ borosilicate glass spheres in an ambient environment under an optical microscope. Experimental results demonstrate that this microgripper, for the first time, achieves a 100% successful release rate (based on 200 trials) and a release accuracy of $hbox{0.70} pm hbox{0.46} muhbox{m}$. Experiments with conductive and nonconductive substrates also confirmed that the release process is not substrate dependent. Theoretical analyses were conducted to understand the release principle. Based on this paper, further scaling down the end structure of this microgripper will possibly provide an effective solution to the manipulation of submicrometer-sized objects.$hfill$[2008-0304] ]]> 18 3 652 659 727 This paper presents a microelectromechanical systems (MEMS) capacitive position sensor for nanopositioning applications in Probe storage systems. The objective of the sensor system design is to develop a high-precision $X$–$Y$ linear and rotational position sensor with a minimum sensor area and a large range of movements at high speed. To achieve this, first, a simple sensor noise model scalable with a sensor area was developed, in which all the parasitic capacitances are taken into account. Furthermore, a signal-processing solution was developed to compensate for the nonlinearities caused by rotational disturbances and, at the same time, to generate a rotational position signal for active rotation-control purposes. A MEMS capacitive sensor prototype was constructed with the design of a 13-$muhbox{m}$ pitch, a 300- $muhbox{m}$ peak-to-peak linear stroke, and a 3.46-$ hbox{mm}^{2}$ sensor area at a 3-$muhbox{m}$ gap. The measured sensor noise was 0.2 nm 1$sigma$, which corresponds to 12 $muhbox{deg}$ 1 $sigma$ for the fabricated prototype sensor, at 25-kHz bandwidth. Furthermore, the signal linearity was significantly enhanced by the proposed sensor signal processing, with a measured sensor signal nonlinearity of 0.78% for an 80-$muhbox{m}$ peak-to-peak stroke at 200 Hz. Finally, the capaciti- - ve sensor-based dynamic closed-loop $X$ –$Y$ linear and rotational position control of an electromagnetic scanner was successfully demonstrated.$hfill$ [2008-0200] ]]> 18 3 660 670 1170 This paper describes the development of aluminum nitride (AlN) resonant accelerometers that can be integrated directly over foundry CMOS circuitry. Acceleration is measured by a change in resonant frequency of AlN double-ended tuning-fork (DETF) resonators. The DETF resonators and an attached proof mass are composed of a 1- $muhbox{m}$ -thick piezoelectric AlN layer. Utilizing piezoelectric coupling for the resonator drive and sense, DETFs at 890 kHz have been realized with quality factors $(Q)$ of 5090 and a maximum power handling of 1 $muhbox{W}$. The linear drive of the piezoelectric coupling reduces upconversion of $1/f$ amplifier noise into $1/f^{3}$ phase noise close to the oscillator carrier. This results in lower oscillator phase noise, $-$96 dBc/Hz at 100-Hz offset from the carrier, and improved sensor resolution when the DETF resonators are oscillated by the readout electronics. Attached to a 110-ng proof mass, the accelerometer microsystem has a measured sensitivity of 3.4 Hz/G and a resolution of 0.9 $hbox{mG}/surdhbox{Hz}$ from 10 to 200 Hz, where the accelerometer bandwidth is limited by the measurement setup. Theoretical calculations predict an upper limit on the accelerometer bandwidth of 1.4 kHz.$hfill$ [2008-0190] ]]> 18 3 671 678 788 This paper reports the design, fabrication, and experimental characterization of a fully microfabricated planar array of externally fed electrospray emitters that produces heavy molecular ions from the ionic liquids $hbox{EMI-BF}_{4}$ and EMI-Im. The microelectromechanical systems (MEMS) electrospray array is composed of the following two microfabricated parts: 1) an emitter die with as many as 502 emitters in 1.13 $hbox{cm}^{2}$ and 2) an extractor component that provides assembly alignment, electrical insulation, and a common bias voltage to the emitter array. The devices were created using Pyrex and silicon substrates, as well as microfabrication techniques such as deep reactive ion etching, low-temperature fusion bonding, and anodic bonding. The emitters are coated with black silicon, which acts as a wicking material for transporting the liquid to the emitter tips. The extractor electrode uses a 3-D MEMS packaging technology that allows hand assembly of the two components with micrometer-level precision. Experimental characterization of the MEMS electrospray array includes current–voltage characteristics, time-of-flight mass spectrometry, beam divergence, and imprints on a collector. The data show that with both ionic liquids and in both polarities, the electrospray array works in the pure ionic regime, emitting ions with as little as 500 V of bias voltage. The data suggest that the MEMS electrospray array ion source could be used in applications such as coating, printing, etching, and nanosatellite propulsion. $hfill$[2008-0270] ]]> 18 3 679 694 1400 The major focus of this study was to examine the feasibility of applying diamond-like nanocomposite (DLN) coatings on the sidewalls of Ni alloy parts fabricated using lithographie, galvanoformung and abformung (LIGA: a German acronym that means lithography, electroforming, and molding) for friction and wear control. Planar test coupons were employed to understand the friction mechanisms in regimes relevant to LIGA microsytems. Friction tests were conducted on planar test coupons as well as between LIGA-fabricated test structures in planar–sidewall and sidewall–sidewall configurations. Measurements were made in dry nitrogen and air with 50% relative humidity by enclosing the friction tester in an environmental chamber. In contrast to bare metal–metal contacts, minimal wear was exhibited for the DLN-coated LIGA NiMn alloy parts and test coupons. The low friction behavior of DLN was attributed to its ability to transfer to the rubbing counterface providing low interfacial shear at the sliding contact. The coating coverage and chemistry on the sidewalls and the substrate–coating interface integrity were examined by transmission electron microscopy, Automated eXpert Spectral Image Analysis, and electron backscatter diffraction on cross sections prepared by focused ion beam microscopy. The role of novel characterization techniques to evaluate the surface coatings for LIGA microsystems technology is highlighted. $hfill$[2008-0007] ]]> 18 3 695 704 1274 Wideband 8–12-GHz inline-type microwave power sensors that are based on measuring the microwave power coupled from the coplanar waveguide line by a microelectromechanical systems membrane are presented. In this method, the signal is available during the power detection. In order to obtain the low reflection losses and insertion losses, as well as the wideband response of the power sensor, an impedance match structure and a compensating capacitance are proposed. The fabrication of the power sensor is compatible with the GaAs monolithic microwave integrated circuit (MMIC) process. The experimental results show that the sensor has reflection losses better than 20 dB and insertion losses less than 0.45 dB up to 12 GHz. A sensitivity of more than 30 $muhbox{V/mW}$ and a resolution of 0.2 mW are obtained at the 10-GHz frequency.$hfill$[2008-0219] ]]> 18 3 705 714 753 We describe a novel type of MEMS optical switch based on moving waveguide which has merits inherited from both MEMS and integrated optics technologies. It provides an expandable 2 $times$ 2 switching capability, a first in this category of switches. The switch is built by assembling independently optimized latching silicon actuator and soft polymer waveguides. The actuator is based on two new structures: a microhinge, dubbed the fork hinge, and a latching structure using a precompressed microspring. The mechanical switching speed was measured below 0.5 ms. The complex polymer waveguide structure was thoroughly characterized to obtain all the components of the optical loss. This analysis allowed us to estimate robustly the insertion loss of the assembled optical switch below 3 dB and to identify the possibilities to improve this figure. $hfill$[2008-0142] ]]> 18 3 715 724 1584 Microresonators employed in microelectromechanical systems for sensing and communications are growing increasingly more sophisticated in terms of structural geometry and mode shapes. Accompanying this increase in sophistication is a corresponding need to develop accurate analytical models to predict the dynamic properties of such resonators. Here, we present an analytical framework to compute thermoelastic damping (TED) in the general class of microresonators characterized by structural discontinuities in the form of slots or internal channels. The temperature field within the resonators is obtained by solving the one-way coupled equation of thermoelastic heat conduction in a piecewise fashion, thereby capturing the effects of structural discontinuities interrupting heat conduction within the beam. The framework is validated by comparison with previously reported finite-element analysis and measurements of damping in slotted microresonators. The analysis leads to an expression for TED in the form of rapidly converging infinite series, and accurate closed-form expressions are obtained by retaining the leading terms. These simple formulas enable a rapid exploration of the design space over a full range of parameters, as illustrated for the case of hollow single-crystal-silicon beams containing internal channels. For constant channel volume, the peak value of TED reduces monotonically with the ratio of channel width to channel height. The analysis is used to identify designs that reduce TED to values that are less than $2 times 10^{-5}$ at all frequencies.$hfill$ [2008-0215] ]]> 18 3 725 735 355 Two versions of microdischarge-based pressure sensors, which operate by measuring the change, with pressure, in the spatial current distribution of pulsed dc microdischarges, are reported. The inherently high temperatures of the ions and electrons in the microdischarges make these devices amenable to high-temperature operation. The first sensor type uses 3-D arrays of horizontal bulk metal electrodes embedded in quartz substrates with electrode diameters of 1–2 mm and 50–100-$muhbox{m}$ interelectrode spacing. These devices were operated in nitrogen over a range of 10–2000 torr, at temperatures as high as 1000 $^{circ}hbox{C}$. The maximum measured sensitivity was 5420 ppm/torr at the low end of the dynamic range and 500 ppm/torr at the high end, while the temperature coefficient of sensitivity ranged from $-$925 to $-$550 ppm/K. Sensors of the second type use planar electrodes and have active areas as small as 0.13 $hbox{mm}^{2}$. These devices, when tested in a chemical sensing system flowing helium as a carrier gas, had a maximum sensitivity of 9800 ppm/torr, a dynamic range of 25–200 torr, and a temperature coefficient of sensitivity of approximately $-$1412 ppm/K.$hfill$ [2008-0262] ]]> 18 3 736 743 1092 A unique T-beam microresonator designed to operate on the principle of nonlinear modal interactions due to 1 : 2 internal resonance is introduced. Specifically, the T-structure is designed to have two flexural modes with natural frequencies in a 1 : 2 ratio, and the higher frequency mode autoparametrically excites the lower frequency mode through inertial quadratic nonlinearities. A Lagrangian formulation is used to model the electrostatically actuated T-beam resonator, and it includes inertial quadratic nonlinearities, cubic nonlinearities due to midplane stretching and curvature of the beam, electrostatic potential, and effects of thermal prestress. A nonlinear two-mode reduced-order model is derived using linear structural modes in desired internal resonance. The model is used to estimate static pull-in bias voltages and dynamic responses using asymptotic averaging. Nonlinear frequency responses are developed for the case of resonant actuation of a higher frequency mode. It is shown that the lower frequency flexural mode is excited for actuation levels above a certain threshold and generates response component at half the frequency of resonant actuation. The effects of damping, thermal prestress, and mass and geometric perturbations from nominal design are thoroughly discussed. Finally, experimental results for a macroscale T-beam structure are briefly described and qualitatively confirm the basic analytical predictions. The T-beam resonator shows a high sensitivity to mass perturbations and, thus, holds great potential as a radio frequency filter–mixer and mass sensor.$hfill$ [2008-0107] ]]> 18 3 744 762 836 We demonstrate and discuss the performance of fully integrated and flexible micro thermoelectric generators $(muhbox{TEGs})$. The devices are fabricated with a low-cost microfabrication process based on electrochemical deposition of a thermoelectric material into a polymer mold. Overall system optimization is demonstrated by means of NiCu and p- and n-type $ hbox{Bi}_{2}hbox{Te}_{3}$-based $muhbox{TEGs}$ . Influences of design, material, fabrication, and performance parameters on device performance are explained by means of measurements and model calculations. The fabricated devices generate up to $2.6ast 10^{-3} muhbox{W}cdot hbox{cm}^{-2}cdothbox{K}^{-2}$ for devices with NiCu thermocouples and up to 0.29 $muhbox{W}cdot hbox{cm}^{-2}cdothbox{K}^{-2}$ for $hbox{Bi}_{2}hbox{Te}_{3}$-based generators in planar state. Mechanical testing on NiCu $muhbox{TEGs}$ demonstrated functionality of the generator when bent to curvatures down to 7.5 mm. This allows for enhanced thermal contact to nonplanar surfaces.$hfill$ [2008-0084] ]]> 18 3 763 772 2601 18 3 C3 C3 566