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Microscale gas chromatography (μGC) systems are miniaturized instruments that typically incorporate one or several microfabricated fluidic elements; such systems are generally well suited for the automated sampling and analysis of gas-phase chemicals. Advanced μGC systems may incorporate more than 15 elements and operate these elements in different coordinated sequences to execute complex operations. In particular, the control software must manage the sampling and analysis operations of the μGC system in a time-sensitive manner; while operating multiple control loops, it must also manage error conditions, data acquisition, and user interactions when necessary. To address these challenges, this work describes the investigation of multithreaded control software and its evaluation with a representative μGC system. The μGC system is based on a progressive cellular architecture that uses multiple μGC cells to efficiently broaden the range of chemical analytes, with each cell incorporating multiple detectors. Implemented in Python language version 3.7.3 and executed by an embedded single-board computer, the control software enables the concurrent control of heaters, pumps, and valves while also gathering data from thermistors, pressure sensors, capacitive detectors, and photoionization detectors. A graphical user interface (UI) that operates on a laptop provides visualization of control parameters in real time. In experimental evaluations, the control software provided successful operation and readout for all the components, including eight sets of thermistors and heaters that form temperature feedback loops, two sets of pressure sensors and tunable gas pumps that form pressure head feedback loops, six capacitive detectors, three photoionization detectors, six valves, and an additional fixed-flow gas pump. A typical run analyzing 18 chemicals is presented. Although the operating system does not guarantee real-time operation, the relative standard deviations of the control loop timings were <0.5%. The control software successfully supported >1000 μGC runs that analyzed various chemical mixtures. [ABSTRACT FROM AUTHOR]

A chemical recognition algorithm is an integral part of any autonomous microscale gas chromatography (µGC) system for automated chemical analysis. For a multi-detector µGC system, the chemical analysis must account for the retention time of each chemical analyte as well as the relative response of each detector to each analyte, i.e., the detector response pattern (DRP). In contrast to the common approaches of heuristically using principal component analysis and machine learning, this paper reports a rule-based automated chemical recognition algorithm for a multi-cell, multi-detector µGC system, in which the DRP is related to theoretical principles; consequently, this algorithm only requires a small amount of calibration data but not extensive training data. For processing both the retention time and the raw DRP, the algorithm applies rules based on expert knowledge to compare the detected peaks; these rules are located in a customized software library. Additionally, the algorithm provides special handling for chromatogram peaks with a small signal-to-noise ratio. It also provides separate special handling for asymmetrical peaks that may result from surface adsorptive analytes. This work also describes an experimental evaluation in which the algorithm used the relative response of two complementary types of capacitive detectors as well as a photoionization detector that were incorporated into the µGC system of interest. In these tests, which were performed on chromatograms with 21–31 peaks for each detector, the true positive rate was 96.3%, the true negative rate was 94.1%, the false positive rate was 5.9%, and the false negative rate was 3.7%. The results demonstrated that the algorithm can support µGC systems for automated chemical screening and early warning applications. [ABSTRACT FROM AUTHOR]

Multinational Enterprises (MNEs) periodically decide on both which products to launch (or phase out) and in which global regions, thereby conducting an integrated products-countries consideration in diversification strategies. Over time, these diversification decisions can have a cumulative impact on the structure. Diversification literature has primarily focused on one of these two metrics rather than providing an integrated view; this work investigates both metrics. Considering deal-making as an execution instrument of strategies, a comparison of historic deals of MNEs with their current structure offers insights into the nature of the diversification strategies that were pursued. For the most active global deal-making pharmaceutical firms, we derive normalized deal diversity profile metrics in terms of their cumulative past product-countries' preferences and compare them with the product-countries' operations of their current subsidiaries. We rationalize MNE deal behaviors as means to shed, acquire and consolidate businesses to enable their market leadership aspirations. The analysis reveals two trajectories that have been actively favored in deals: one directed at niche products offered globally, and one directed at niche products in selected countries. The former is characterized by deals in a high number of countries, whereas the latter by two identifiably different product concentration levels. In contrast, trajectories directed at widely diverse products have been disfavored in deals. Understanding such directions and their pace can aid in global- or group-level strategy formulation, monitoring strategy execution, interpreting competitor moves and designing regional policies. [ABSTRACT FROM AUTHOR]

Using distributed MEMS pressure sensors to measure small flow rates in high resistance fluidic channels is fraught with challenges far beyond the performance of the pressure sensing element. In a typical core-flood experiment, which may last several months, flow-induced pressure gradients are generated in porous rock core samples wrapped in a polymer sheath. Measuring these pressure gradients along the flow path requires high resolution pressure measurement while contending with difficult test conditions such as large bias pressures (up to 20 bar) and temperatures (up to 125 °C), as well as the presence of corrosive fluids. This work is directed at a system for using passive wireless inductive-capacitive (LC) pressure sensors that are distributed along the flow path to measure the pressure gradient. The sensors are wirelessly interrogated with readout electronics placed exterior to the polymer sheath for continuous monitoring of experiments. Using microfabricated pressure sensors that are smaller than ø15 × 3.0 mm3, an LC sensor design model for minimizing pressure resolution, accounting for sensor packaging and environmental artifacts is investigated and experimentally validated. A test setup, built to provide fluid-flow pressure differentials to LC sensors with conditions that mimic placement of the sensors within the wall of the sheath, is used to test the system. Experimental results show the microsystem operating over full-scale pressure range of 20,700 mbar and temperatures up to 125 °C, while achieving pressure resolution of <1 mbar, and resolving gradients of 10–30 mL/min, which are typical in core-flood experiments. [ABSTRACT FROM AUTHOR]

Digitally dependent firms, which are linked to a large number of other firms with varying capabilities, are challenged on evaluating networks with which to engage. Empirically supported heuristic guidance can aid firms in identifying alliances to strengthen capability. We report a case study of firms linked to the Internet of Things (IoT) with a broad view of firms that leverage digital technologies to offer a diverse range of next generation consumer and industrial products and services. This article includes a network analysis of their publicly declared deals to reveal clusters of high volume deals-making activity and their respective hub firms. Based on the rationale of deals of the hub firms, the firms are categorized in a perceptual framework of market-oriented versus technology-seeking inclination. The inclinations of these hub firms were found to vary between technology-seeking, market-oriented, and ambidextrous. The results of this article can inform hub firms in assessing investment portfolios, nonhub firms in evaluating networks governed by hub firms, and policy makers to design incentives for digital adoption. [ABSTRACT FROM AUTHOR]

Conventional capillary gas chromatography (GC) columns, which have circular symmetry in cross-section and uniformity in length, are well modeled mathematically by the GC rate theory. However, even after adaptation, the theory has limited applicability to many unconventional properties in microfabricated GC columns, such as trapezoidal cross-sections, non-uniform stationary phase, and temperature gradients. This paper reports a 3D finite-element model for the chemical separation process in microfabricated GC columns using COMSOL. The model incorporates gas flow, diffusion, partition, and temperature effects, enabling quantitative assessment of the separation performance of microfabricated GC columns with different stationary phase coating topologies and temperature gradients. To address the tremendous computational burden in such a 3D model, this paper investigates methods of providing proper meshing and dimensional scaling. For validation purposes, the implemented model was first applied to a conventional capillary GC column and showed good matches to both the analytical calculation and experimental results. Next, the model was used to assess microfabricated columns with a trapezoidal cross-section and different stationary phase coating topologies. The results showed that, for the cases under consideration, a single-side-coated column provides only a 33% lower separation resolution compared to a double-side-coated column, and a parabolic stationary phase profile provides only a 12% lower separation resolution compared to a uniform profile. The model also indicated that temperature gradients have a negligible impact on separation performance. [ABSTRACT FROM AUTHOR]

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-[micro]m interelectrode spacing. These devices were operated in nitrogen over a range of 10-2000 torr, at temperatures as high as 1000[degrees]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 [mm.sup.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. [2008-0262] Index Terms--Plasma applications, plasma confinement, plasma measurements, plasma properties, pressure effects, sensitivity.

This paper presents a system for wirelessly monitoring the accumulation of sludge in a biliary stent. Two generations of the system are detailed. The first-generation system utilizes a 2 x 37.5-mm ribbon sensor with a mass of 18 mg, along with 0.8-mm-thick x 1.6-ram-diameter neodymium magnets to bias the sensor. Both components are integrated with a 4-mm-diameter stainless steel stent. The second-generation system comprises a sensor and a magnetic layer [consisting of strontium ferrite particles suspended in polydimethylsiloxane (PDMS)] that conform to the meshed topology and tubular curvature of a 5-mm-diameter Elgiloy stent. The second-generation sensors have an active area of 7.5 x 29 mm and a mass of 9.1 mg. The sensors in both generations are fabricated from 28-[micro]m-thick foils of magneto-elastic 2826MB Metglas, an amorphous Ni-Fe alloy. Analytical and finite-element models that predict sensor response in the dynamic biological environment are presented. The response of each system to viscosity changes that precede and accompany biliary sludge accumulation is tested, with resonant frequency changes of 2.8% and 6.5% over a 10-cP range for each respective generation. Sludge accumulation is simulated with successive coatings of either paraffin or an acrylate terpolymer. Resonant frequency response to this mass loading effect is similar for both generations of the system, showing a 40% decrease after applying a mass load of 2.5 x the mass of the sensor. [2008-(1154] Index Terms--Elgiloy, magnetoelasticity, Metglas, microsensors, photochemical machining, resonant sensors.

This paper reports on dc pulse-powered microdischarges in air at atmospheric pressure and their potential utility in chemical sensing. For electrode gaps of 50-100 [micro]m, microdischarges take the form of a glow discharge, an arc discharge, or a hybrid of the two. Arc microdischarges have high optical intensity but suffer from high background emission. Glow microdischarges have low background emission, but the prominent emission is confined in the UV-blue region of the spectrum. The arc--glow hybrid has characteristics that are intermediate between the two and can be tuned by circuitry to suit the chemical sensing application. A handheld system for chemical analysis using synchronized emission spectroscopy of these pulsed microdischarges is demonstrated. The system employs an exchangeable sensor chip (different for gas and liquid samples), a control circuit, and a commercially available portable spectrum analyzer coupled to a handheld computer. A pump and inert carrier gases are not utilized. The system can generate one or a series of single-shot microdischarges per chemical analysis. The gas discharge microchip, which utilizes electroplated copper electrodes on a glass substrate, has an electrode separation of 75 [micro]m and an active area of 300 x 300 [micro][m.sup.2]. The handheld system has been used to detect 17 ppm of acetone vapor in air. The liquid discharge microchip also has an electrode gap of 75 [micro]m and an active area of 1 x 1 [mm.sup.2]. It uses a porous cathode fabricated by micromolding and sintering glass frit slurry in a microchannel. When a microdischarge is initiated between the metal anode and the wet cathode, the liquid is sputtered into the microdischarge and emits characteristic line spectra. In this configuration, the system can detect 2 ppm of aqueous Cr without preconcentration. Index Terms--Chemical sensing systems, gas detectors, gas discharge devices, microarc, microdischarge, microplasma, water chemistry.

This paper reports deposition of silicon at elevated and room temperatures in spatially localized areas of a microchip by plasma-enhanced chemical vapor deposition using microplasmas. The microplasmas are generated by providing dc power to thin-film Ti electrodes patterned on the microchip. Electrode arrangements include configurations in which multiple cathode elements share a single anode. At the operating pressures used, the plasma glow is confined to the region directly over the energized cathodes only, and the deposition is localized to these regions. A silane ambient allows Si to be deposited at 6.7-15.9 nm/min using cathode power densities of 3.65-9.35 W/[cm.sup.2], with the substrate heated to 300 [degrees]C. At room temperature, deposition rates up to 4.2 nm/min are realized. Also described is a plasma-coupling technique that permits isolated metal pads to be powered by plasma spreading from a proximate cathode at certain levels of power and pressure. This permits controlled variations of silicon thickness in a subarray of unbiased electrodes, simplifying the powering scheme. Index Terms--Plasma-enhanced chemical vapor deposition (PECVD), polysilicon, thin-film deposition.

This paper describes two stainless steel microstructures that are microelectrodischarge machined from 50-[micro]m-thick planar foil for intraluminal measurements of pressure and flow (with potential for applications ranging from blood vessels to bile ducts). The first structure is an inductive antenna stent (stentenna) with 20-mm length and 3.5-mm expanded diameter. It is coupled with capacitive elements to form resonant LC tanks that can be telemetrically queried. The resulting LC tanks are deployed inside silicone mock arteries using standard angioplasty balloons and used in a passive telemetry scheme to sense changes in pressure and flow. Using water as the test fluid, the resonant peaks shift from about 215 to 208 MHz as the flow is increased from 0 to 370 mL/min. The second structure is a ring-shaped intraluminal cuff with two 400 x 750-[micro][m.sup.2] electrodes that are used to provide a direct transduction of flow velocity in the presence of a magnetic field. It is fabricated in a manner similar to the stentenna, but with an insulating segment. The voltage has a linear dependence on flow rate, changing by 3.1-4.3 [micro]V per cm/s of flow (of saline) over a 180 cm/s dynamic range, with a magnetic field of about 0.25 T. [1733] Index Terms--Bloodflow, cardiac, microelectrodischarge machining, sensor network, wireless.

This paper reports on a batch mode planar pattern transfer process for bulk ceramics, glass, and other hard, brittle, nonconductive materials suitable for micromachined transducers and packages. The process is named LEEDUS, as it combines lithography, electroplating, batch mode micro electro-discharge machining ([micro]EDM) and batch mode micro ultrasonic machining ([micro]USM). An electroplating mold is first created on a silicon of metal wafer using standard lithography, then using the electroplated pattern as an electrode to [micro]EDM a hard metal (stainless steel or WC/Co) tool, which is finally used in the [micro]USM of the ceramic substrate. A related process (SEDUS) uses serial [micro]EDM and omits lithography for rapid prototyping of simple patterns. Feature sizes of 25 [micro]m within a 4.5 x 4.5 [mm.sup.2] die have been micromachined on glass-mica (Macor) ceramic plates with 34 [micro]m depth. The ultrasonic step achieves 18 [micro]m/min. machining rate, with a tool wear ratio of less than 6% for the staiuless steel microtool. Other process characteristics are also described. As a demonstration, octagonal and circular spiral shaped in-plane actuators were fabricated from bulk lead zirconate titanate (PZT) plate using the LEEDUS/SEDUS process. A device of 20/[micro]m thickness and 450 [micro]m x 420 [micro]m footprint produces a displacement of [approximately equal to] 2[micro]m at 40 V. [1652] Index Terms--Ceramic micromachining, microelectro-discharge machining (EDM), piezoelectric micro actuator, ultrasonic micromachining.

Microsystems using electrothermal bent-beam microactuators have been demonstrated for a variety of applications including optical attenuators, RF switches, and micro positioners, thus creating a need for information on the longevity of these devices. This paper reports on the dc and pulse mode lifetime testing of this class of actuators constructed using polysilicon and p++ doped single crystal silicon. The relative temperature profile along the top surface of an actuator is experimentally verified by scanning probe microscopy. Displacement measurements are used to explore links between aging behavior and the design variables and operating conditions. At low power levels (which result in average operating temperatures of 300-400 [degrees]C) both polysilicon and p++ Si devices provide continuous dc operation for >1400 min. in air without change in amplitude. While some types of p++ Si devices show monotonic loss of amplitude in pulse tests, others have been operated up to 30 million cycles without degradation. The displacement for polysilicon actuators can either increase of decrease depending on the geometry of the device and operating conditions, both of which are related to temperature and stress of the structural members. Polysilicon grain transformations are observed over extended operation at high temperatures. Performance changes are correlated to material properties using SEM and TEM images. [1682] Index Terms--Actuator, electrothermal, lifetime, micromachining, polysilicon, in situ annealing.

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 x reduction in energy consumption, with the activation energy falling from over 1000 [mciro]J at dc activation, to less than 200 [micro]J 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. [1566] Index Terms--Bent-beam electrothermal actuator, bistable structure, burst pulse drive, single pulse drive.

This paper describes the design, fabrication, and testing of a single-chip micromachined implementation of a Knudsen pump, which uses the principle of thermal transpiration, and has no moving parts. A six-mask microfabrication process was used to fabricate the pump using a glass substrate and silicon wafer. The Knudsen pump and two integrated pressure sensors occupy an area of 1.5 mm x 2 mm. Measurements show that while operating in standard laboratory conditions this device can evacuate a cavity to 0.46 atm using 80 mW input power. The pumpdown time of an on-chip chamber and pressure sensor cavity with a total volume of 80 000 cubic micrometers is only 2 s, with a peak pump speed of 1 x [10.sup.-6] cc/min. High thermal isolation is obtained between the polysilicon heater and the rest of the device. [1073] Index Terms--High temperature, thermal isolation, thermal transpiration, thermomolecular, vacuum pump.

This paper reports on a micromachined Kelvin probe structure with an integrated scanning tip and an integrated electrothermal actuator that provides axial dithering motion. The device is fabricated from metal foil by a modified microelectrodischarge machining process that allows electrical isolation within the device. In particular, it permits the incorporation of a wide epoxy plug that creates an insulating gap with low parasitic capacitance between the probe and the actuator. The epoxy structures are found to withstand the thermal and mechanical conditions encountered during device operation. The device is used to measure changes in the external surface potential of a parylene microfluidic channel as a function of varying pH of liquid inside the channel. A contact potential difference of [approximately equal to] 6V is measured for a change in pH from 4 to 8 within the channel. The device is also used to map embedded charge in a thin Si[O.sub.2] layer on a Si substrate, showing it to be suitable for monitoring microelectronics manufacturing processes. [1072] Index Terms--Contact potential, oxide charge, pH, surface potential.

This paper reports a microfluidic device that integrates electrical and optical features required for field-portable water-chemistry testing by discharge spectroscopy. The device utilizes a dc-powered spark between a metal anode and a liquid cathode as the spectral source. Impurities are sputtered from the water sample into the microdischarge and characteristic atomic transitions due to them are detected optically. A blazed grating is used as the dispersion element. The device is fabricated from stacked glass layers, and is assembled and used with a charge-coupled device (CCD) sensing element to distinguish atomic spectra. Two structural variations and optical arrangements are reported. Detection of Cr and other chemicals in water samples has been successfully demonstrated with both devices. The angular resolution in terms of angular change per unit variation in wavelength ([??][theta]/[??][lambda]) is experimentally determined to be approximately 0.10 rad/[micro]m, as opposed to the idealized theoretical estimate of 0.22 rad/[micro]m. This is because the microdischarge is uncollimated and not a point source. However, this is sufficient angular resolution to allow critical spectra of metal impurities to be distinguished. Index Terms--Chemical sensing, dispersion optics, microdischarge, sample delivery, water chemistry.

This paper presents an interface circuit for low-frequency dithering measurements of resistor-based transducers. It is demonstrated in the context of a polyimide-shank scanning thermal microscopy probe which provides high thermal sensitivity and spatial resolution, but has a low bandwidth from both mechanical and thermal perspectives. These pose challenges in temperature dithering and control, as well as noise immunity. The circuit includes a proportional-integral controller and a demodulator, along with appropriate amplifier and filter blocks. It keeps the average temperature of the probe tip constant while synchronously detecting variations in the second harmonic of the modulated signal as the tip is scanned across the sample surface. Strategic choices in the circuit architecture and topology are evaluated, and the overall system including the sensor and the circuit is simulated. Measurements of the implemented system show that a signal-to-noise ratio (SNR) of 15.7 is achieved while scanning a photoresist sample of 218 nm thickness on a silicon substrate, and that the detection limit for variations in thermal conductance is < 3 pW/K. [1125] Index Terms--Polyimide probe, scanning probe, thermal imaging.

A new approach that uses planar batch manufacturing technologies is presented for the design and fabrication of coronary artery stents. Stent samples with different wall patterns have been fabricated from 50-[micro]m-thick stainless steel foil using microelectrodischarge machining. Stents have been expanded to tubular shapes by using angioplasty balloons, both inside mock arteries and without external confinement (i.e., free-standing). Free-standing stents exhibit diameter variations of Index Terms--Angioplasty, arc, electrodischarge, micromachining, stent.

This paper explores the use of miniaturized magnets to enhance the parameters of dc microplasmas. The microplasmas are powered by thin coaxial electrodes and are enhanced by a coaxial magnetron configuration machined from niobium composite magnets. At operating pressures of 1-4 torr, a glow region that is confined to the volume directly over the cathode, forms a traditional magnetron-type annular ring. Three coaxial magnets, ranging in total size from 3.2 to 7.2 mm in outside diameter generate measured magnetic fields up to 3030 G. The magnetic field structure is profiled with a small Hall probe and is modeled by finite-element analysis. The plasma currents for various applied voltages are measured, and the plasma breakdown/termination voltages are determined. In nitrogen ambients at 1.2 torr and 370-V bias, the current changes from 9.3 mA in the absence of a magnetic field to 17.6 mA with the addition of the largest magnet. The sheath region decreases with the addition of the magnetic structures, illustrating an effect on the Debye length and, therefore, the local plasma density. The dimensions of the sheath are found to vary radially within the annular microplasma. The smallest sheath corresponds to the region of highest magnetic field over the south pole for the largest magnetic configuration. This effect is used to generate a microplasma in SF8 on a silicon wafer producing a localized etch. The etch rate in the region of the brightest glow is three times greater than the weakest etch rate, allowing spatially localized etch selectivity without masking. Index Terms--Magnetic confinement, manufacturing, microdischarge, microplasma, sensing.

In order to understand the details of high-field breakdown in microstructures that are vacuum packaged, a series of experiments are used to determine characteristics of microdischarges. The results support a reinterpretation of conventional assumptions based upon large scale discharges. When planar microelectrodes are used, Paschen's curve is not applicable in the traditional sense: the breakdown voltage is relatively insensitive to pressure in the 1-20 torr range, and remains at ~400 V for air ambient. However, the spatial distribution of discharge current does vary with the pressure and the power. Large voltage gradients are supported in the glow region which is confined to a few millimeters directly above the cathode, and within a few hundred microns of its lateral edge. Their magnitudes range from 100 000-500 000 V/m for operating pressures ranging from 1.2-6 torr. Based on these results, guidelines are provided for the design of high-voltage microsystems. [916] Index Terms--Electric breakdown, electrostatic devices, microdischarge, microplasma.

The creation of low resistivity, ultrashallow source/drain regions in MOS device structures requires rapid thermal processing (RTP) techniques that restrict diffusion and activate a significant percentage of the implanted dopant species. While current heating techniques depend upon illumination based heating, a new technology, electromagnetic induction heating (EMIH), achieves a rapid heating of the silicon by coupling electromagnetic radiation directly into the silicon wafer. Heating rates of 125 [degrees]C/s to temperatures in excess of 1050 [degrees]C have been achieved for 75--and 100-mm-diameter wafers at input powers of 1000 and 1300 W, respectively. These ramp rates are suitable for ultrashallow junction formation, and junctions shallower than 30 nm with sheet resistances lower than 600 [ohm]/square have been achieved. This paper details the application of electromagnetic heating using radiation in the microwave, 2450 MHz, frequency regime. Experimental results, comparing microwave annealed implants to the well documented SEMATECH requirements, and simulations, utilizing a coupled electromagnetic-thermal computer model, of the heating process are discussed. Index Terms--Activation, anneal, dopant, junction, microwave, radiation, shallow.

A silicon-micromachined servo-controlled capacitive pressure sensor is described. The use of a capped-cylinder shape with pick-off electrodes external to a sealed cavity permits this device to be fabricated in only three masking steps. Device behavior is evaluated experimentally and by finite element analysis. A fabricated device with 2 mm diameter, 9.7 [micro]m structural thickness and 10 [micro]m cavity height provides a measured sensitivity of 0.516 V/kPa over a dynamic range of 20-100 kPa gauge pressure, with a nonlinearity of Index Terms--Dissolved wafer process, liquid encapsulation, pressure sensor, servo-controller.

We report a high yield fabrication process based on surface micromachining of sapphire substrates and plasma-deposited thin films for pressure sensors with extraordinarily high output swing relative to baseline and parasitic capacitance. This feature allows the use of massively parallel diaphragms arrays in a single sensor chip that is read out with a single interface circuit, providing a superior full-scale range and resolution in a small footprint. Five types of sensor chips are reported, incorporating: a) a single diaphragm (ø 100 μm diameter); b) 18 diaphragms in parallel (ø 100 μm diameter); c) 85 diaphragms (ø56-ø 92 μm diameter); d) 8 diaphragms in parallel (ø 200 μm diameter); and e) 32 diaphragms in parallel (ø110-ø 150 μm diameter). The respective maximum gauge pressures are 30 MPa, 30 MPa, 70 MPa, 70 kPa, and 110 kPa; the respective resolutions are 1.0 kPa, 0.2 kPa, 0.5 kPa, 5.7 Pa, and 2.6 Pa. Full-scale range is defined with the upper boundary as the applied pressure at which the incremental response falls below 30% of the incremental response at the lower boundary (which is approximated as atmospheric pressure). In two of these cases, varying diameters are used to reduce the inherent non-linearity of the sensor response over the full-scale pressure range. The 85-diaphragm sensor, intended for downhole pressure sensing, provides a capacitance response of 0.46 fF/kPa and 7.1 pF C0. The 32-diaphragm sensor, intended for lower operating pressures, provides capacitance response of 29 fF/kPa and 11.5 pF C0. The fabrication process, design features, and experimental results are presented. [ABSTRACT FROM AUTHOR]

The detection of trace contaminants in water by spectroscopy of micro glow discharges operating in air or at moderate vacuum using liquid electrodes is discussed. The development of a liquid electrode spectral emission chip (LEd-SpEC) is described.

This paper describes the design, implementation, and evaluation of an environmental logging microsystem (ELM) for operation at elevated pressure and in corrosive environments, at temperatures up to 125°C. The ELM units are intended to be deployed in large quantities, allowed to collect data, and then retrieved, interrogated, and re-charged. Powered by a rechargeable battery embedded within the system, each ELM incorporates pressure and temperature sensors, control electronics, optical communication elements, and power management and battery re-charging circuits. The pressure sensor is a customized capacitive transducer chip on a sapphire substrate; details are provided in a companion paper. The electronic components and battery used in ELM are selected on the basis of functionality and form factor; packaged components are selected for ease of assembly and for added protection against the environment. The pressure sensor, electronics and battery are assembled on a flexible circuit board, folded into a stack with dimensions 7.2 mm $\times\,\,6.6$ mm $\times\,\,6.5$ mm, and encapsulated in a steel tube filled with optically transparent silicone caulk. This encapsulation provides mechanical protection against shock and abrasion, as well as chemical protection against high salinity environments, while allowing the ambient pressure and temperature to be transferred to the sensing elements. Results are reported from high-temperature and high-pressure tests reaching 125°C and 7,250 psi in brine and other corrosive environments in laboratory conditions. Field tests that were conducted in a brine well to a maximum depth of 1,235 m are also described. The recorded data were post-processed to interpret the environmental pressure and temperature. [ABSTRACT FROM AUTHOR]

This paper reports the design, microfabrication, and experimental evaluation of a monolithic Si-micromachined four-stage Knudsen pump (KP) suitable for microscale gas chromatography (µGC) applications. Without moving parts, KPs generate gas flow by leveraging free molecular flow against a temperature gradient in narrow channels. In this work the KP consists of four monolithically integrated stages that are fabricated by a five-mask lithographic process; each pump stage is micromachined into a silicon-on-insulator wafer and fluidically connected to adjacent stages by channels etched into glass wafers that are bonded above and below the silicon wafer. The pumping channels are densely arrayed, vertically oriented, 1.2 µm-wide rectangular channels with 10 nm thick Al2O3 sidewalls. The four-stage KP has a footprint of 5 × 7.5 mm2. While operating at ambient atmospheric pressure, the pump provides a blocking pressure of ≈3.3 kPa and a maximum air flow rate of ≈0.75 sccm with 1.2 W input power. (The experimental results match the modeling with <30% discrepancy.) Such performance is suitable for providing gas flow in µGCs. [ABSTRACT FROM AUTHOR]

This article explores electric current and field distributions in dc microplasmas, which have distinctive characteristics that are not evident at larger dimensions. These microplasmas, which are powered by coplanar thin-film metal electrodes with 400-μm minimum separations on a glass substrate, are potentially useful for microsystems in both sensing and microfabrication contexts. Experiments in N[sub 2] ambient show that electron current favors electrode separations of 4 mm at 1.2 Torr, reducing to 0.4 mm at 10 Torr. The glow region is confined directly above the cathode, and within 200–500 μm of its lateral edge. Voltage gradients of 100 kV/m exist in this glow region at 1.2 Torr, increasing to 500 kV/m at 6 Torr, far in excess of those observed in larger plasmas. Numerical simulations indicate that the microplasmas are highly nonquasineutral, with a large ion density proximate to the cathode, responsible for a dense space-charge region, and the strong electric fields in the glow region. It is responsible for the bulk of the ionization and has a bimodal electron energy distribution function, with a local peak at 420 eV. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Wireless magnetoelastic sensors offer significant potential for measuring the accumulation of biomass within stents—enabling early detection prior to stent occlusion—but the encapsulation of these sensors remains a critical challenge. The encapsulation must allow the sensors to navigate the curvature and accommodate the contact forces imparted during and after the implantation procedure, while also leaving the sensor open to mechanical interaction with the biomass during the extended period of deployment. This paper is focused on the encapsulation of ribbon-like magnetoelastic sensors (12.5 mm × 1 mm × 60 μm) within plastic biliary stents (inner diameter of 2.54 mm). The compromise between two polymer-based package designs—one mechanically flexible (Type F) and one mechanically stiff (Type S)—is evaluated. The primary advantage of the Type F package is the flexibility during the delivery process while that of the Type S package is in maintaining a strong signal even when the stent is in a curved bile duct. The maximum thicknesses of the Type F and S packages are 0.53 and 0.74 mm, respectively. Mechanical tests show that both types protect the sensors from forces imparted by a standard introducer, and allow the encapsulated sensors to accommodate bending with a radius of curvature as small as 3 cm. The Type F package has also been tested in situ, in the bile duct of a porcine carcass. The signal is measurable with a wireless range of ≍10 cm, at a resonant frequency of 159 kHz and a quality factor of 397. [ABSTRACT FROM AUTHOR]