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A midinfrared absorption sensor for crank-angle-resolved in-cylinder measurements of gasoline concentration and gas temperature for spark-ignition internal-combustion engines is reported, and design considerations and validation testing in the controlled environments of a heated cell and shock-heated gases are discussed. Mid-IR laser light was tuned to transitions in the strong absorption bands associated with C--H stretching vibration near 3.4 [micro]m, and time-resolved fuel vapor concentration and gas temperature were determined simultaneously from the absorption at two different wavelengths. These two infrared laser wavelengths were simultaneously produced by difference-frequency generation, which combines a near-IR signal laser with two near-IR pump lasers in a periodically poled lithium niobate crystal. Injection current modulation of the pump lasers produced intensity modulation of the mid-IR, which allowed the transmitted signals from the two laser wavelengths to be detected on a single detector and separated by frequency demultiplexing. Injection current modulation produced a wavelength modulation synchronous with the intensity modulation for each of the laser wavelengths, and accurate measurement of the gasoline absorption signal required the effects of wavelength modulation to be considered. Validation experiments were conducted for a single-component hydrocarbon fuel (2,2,4-trimethyl-pentane, commonly known as iso-octane) and a gasoline blend in a heated static cell (300 [less than or equal to] T [less than or equal to] 600 K) and behind planar shock waves (600 < T < 1100 K) in a shock tube. With a bandwidth of 10 kHz, the measured fuel concentrations agreed within 5% RMS and the measured temperature agreed within 3% RMS to the known values. The 10 kHz bandwidth is sufficient to resolve 1 crank-angle degree at 1600 RPM. OCIS codes: 120.1740, 120.6780, 300.1030.

Cavity-enhanced tunable diode laser absorption spectroscopy is an attractive method for measuring small concentrations of gaseous species. Ethane is a breath biomarker of lipid peroxidation initiated by reactive oxygen species. A noninvasive means of quickly quantifying oxidative stress status has the potential for broad clinical application. We present a simple, compact system using off-axis integrated cavity output spectroscopy with an interband cascade laser and demonstrate its use in real-time measurements of breath ethane. We demonstrate a detection sensitivity of 0.48 ppb/Hz.sup.1/2]. OCIS codes: 280.0280, 300.0300.

This paper presents the design, fabrication, and characterization of millimeter-scale rotary electromagnetic generators. The axial-flux synchronous machines consist of a three-phase microfabricated surface-wound copper coil and a multipole permanent-magnet (PM) rotor measuring 2 mm in diameter. Several machines with various geometries and numbers of magnetic poles and turns per pole are designed and compared. Moreover, the use of different PM materials is investigated. Multipole magnetic rotors are modeled using finite element analysis to analyze magnetic field distributions. In operation, the rotor is spun above the microfabricated stator coils using an off-the-shelf air-driven turbine. As a result of design choices, the generators present different levels of operating frequency and electrical output power. The four-pole six-turn/pole NdFeB generator exhibits up to 6.6 [mW.sub.rms] of ac electrical power across a resistive load at a rotational speed of 392 000 r/min. This milliwatt-scale power generation indicates the feasibility of such ultrasmall machines for low-power applications. [2008-0078] Index Terms--AC generators, micromachining, permanent-magnet (PM) machines, power microelectromechanical systems (MEMS).

In this paper, the concept, fabrication, and characterization of a kinematically stabilized polymeric microbubble actuator (endoskeletal microbubble actuator) for a pneumatic tactile display application are presented. The kinematic stabilization is achieved by the combination of two polymeric layers with complementary functions: a microcorrugated parylene diaphragm layer as a 'skeleton' to provide a directional deflection in a desired axial direction while suppressing undesired lateral deflections and an overcoated elastomer diaphragm layer as a 'skin' to help the extended membrane recoil to its original shape, ensuring diaphragm stability. Arrays of microcorrugated diaphragms are implemented in a mass producible fashion using inclined rotational UV lithography, micromolding, and pattern transfer techniques. Both the number of corrugations and the corrugation profile of the endoskeletal actuator are determined through numerical analysis, taking into account the constraints of the microfabrication processes utilized. A prototype of a single endoskeletal bubble actuator with a diameter of 2.6 mm has been fabricated and characterized. For comparison purposes, elastomer microcorrugated diaphragm (skin only) actuators and parylene microcorrugated diaphragm (skeleton only) actuators of the same materials and dimensions have also been fabricated and tested. While the skin-only diaphragm actuators demonstrated undesired omnidirectional inflation and the skeleton-only diaphragm actuators have shown unstable and irreversible deformation during extension, the proposed endoskeletal microbubble actuators have shown stable reversible axial extensions with a deflection of approximately 0.9 mm. A 6 x 6 array of endoskeletal polymer microbubble actuators integrated with a microfluidic manifold has been successfully fabricated, demonstrating its mass manufacturability. [2006-0243] Index Terms--Digital Clay, endoskeletal bubble, inclined exposure, microbubble actuator, microcorrugated diaphragm.

Administration of protein and DNA biotherapeutics is limited by the need for hypodermic injection. Use of micron-scale needles to deliver drugs in a minimally invasive manner provides an attractive alternative, but application of this approach is limited by the need for suitable microneedle designs and fabrication methods. To address this need, this paper presents a conical polymer microneedle design that is fabricated using a novel integrated lens technique and analyzed for its ability to insert into the skin without mechanical failure. Microneedle master structures were fabricated using microlenses etched into a glass substrate that focused light through SU-8 negative epoxy resist to produce sharply tapered structures. Microneedle replicates were fabricated out of biodegradable polymers by micromoiding. Because microneedle mechanical properties are critical to their insertion into the skin, we theoretically modeled two failure modes (axial mode and transverse mode), and analytical models were compared with measured data showing general agreement. Guided by this analysis, polymer microneedles were designed and demonstrated to insert to different depths into porcine skin in vitro. 'Long' polymer microneedles were also demonstrated in human subjects to insert deeply without failure. Index Terms--Biodegradable polymer, lens, microneedle, transdermal drug delivery.

The active cooling substrate in this study is a microelectromechanical system device that implements the synthetic jet concept into a printed wiring board (PWB) to enhance thermal management. Synthetic jets are oscillatory jets synthesized from the surrounding fluid using electromagnetic actuators. The jet fluid mechanics and heat transfer applications have been investigated by a variety of on-board (PWB) fluidic structures. A testbed comprising six different fluidic channels has been fabricated and characterized with a standard silicon based platinum heater. Based on the fluid mechanics measurements and cooling performance tests, an empirical correlation of synthetic jet Nusselt number with its Reynolds number, fluidic channel dimensions, and jet locations has been derived. Through a magnitude analysis, jet actuator diaphragm, fluidic channel dimension, and cooling location optimizations have been investigated. [DOI: 10.1115/1.2351900]

This paper presents the modeling of permanent-magnet (PM) generators for use in microscale power generation systems. The generators are three-phase, axial-flux, synchronous machines, each consisting of a multipole, surface-wound stator and PM rotor. The machines are modeled by analytically solving two-dimensional (2-D) magneto-quasi-static Maxwell's equations as a function of radius. The 2-D field solutions are then integrated over the radial span of the machine to determine circuit parameters such as open-circuit voltage and inductance as well as hysteresis loss in the stator core and eddy current losses in the stator core and windings. The model provides a computationally fast method to determine power and efficiency of an axial-flux PM machine as a function of geometry, speed, and material properties. The open-circuit voltage predictions are also shown to agree well with 3-D finite-element analysis simulation results. [1700] Index Terms--AC generators, micromachining, permanent-magnet (PM) machines, power microelectromechanical systems (MEMS).

This paper presents the design, fabrication, and characterization of permanent-magnet (PM) generators for use in microscale power generation systems. The generators are three-phase, axial-flux, synchronous machines, each consisting of an eight-pole surface-wound stator and PM rotor. The devices are fabricated using a combination of microfabrication and precision assembly. Characterization is achieved using a custom-built experimental test stand that incorporates an off-the-shelf gas-driven spindle to power the machines. At a rotational speed of 120 000 rpm, one generator demonstrates 2.5 W of mechanical-to-electrical power conversion and, coupled to a transformer and rectifier, delivers 1.1 W of dc electrical power to a resistive load. This watt-scale electrical power generation demonstrates the viability of scaled PM machines for practical power generation applications. [1701] Index Terms--AC generators, micromachining, permanent-magnet (PM) machines, power microelectromechanical systems (MEMS).

Electrical isolation of bulk-micromachined single crystal silicon (SCS) microelectromechanical systems (MEMS) devices is demonstrated using through-wafer junction isolation. Through-wafer junctions of alternating n-type and p-type silicon (npn junctions) are fabricated using 'temperature gradient zone melting' (TGZM) or thermomigration of aluminum in n-type silicon. The npn regions electrically isolate various regions of the SCS from one another by acting as series connected backbiased diodes. Thermomigration is a potentially high throughput process that is consistent with batch fabrication principles. Practical demonstration of this technique is shown by fabricating and testing a full wafer thickness (~300 [micro]m) electrostatic actuator fabricated from a single silicon wafer, and driven at 360 Vpp at resonance of 1933 Hz. Breakdown voltages of single thermomigrated npn junctions in excess of 189 V with leakage currents less than 70 nA were measured. For multiple junctions in series, overall breakdown voltages greater than 1500 V were demonstrated. Compatibility of thermomigration with standard p-channel metal-oxide-semiconductor (PMOS) transistors is also demonstrated. [1345] Index Terms--Bulk micromachining, deep reactive ion etching (DRIE), diodic isolation, electrical isolation, inductively coupled plasma (ICP), junction isolation, temperature gradient zone melting (TGZM), thermomigration.

Various three-dimensionally (3-D) complex MEMS structures are fabricated using multidirectional ultraviolet (UV) lithography, which includes reverse-side exposure through a UV-transparent substrate, inclined exposure with or without simultaneous substrate rotation, and the combination of these processes. A reverse-side exposure scheme through UV-transparent substrates (e.g., glass, sapphire, or quartz) has been exploited for implementing high-aspect-ratio structures (greater than 20:1), repeatable self-alignment photoresist patterning with subsequent metallization on a BST/sapphire substrate, and unconventional patterning using substrate optics such as proximity patterning or integrated lens techniques. Inclined exposure has been applied to a SU-8 substrate with differing inclination angles and incidence directions. The refractive index of SU-8 is experimentally determined to be 1.68 by means of test structures fabricated using this approach. Implemented structures using the inclined exposure include vertical screen structures, inclined tubes, and conical shape structures. Dynamic mode operation, in which the substrate is continuously rotated and tilted during exposure is also discussed. Examples of achievable 3-D structures using dynamic mode operation are presented. [1581] Index Terms--Inclined exposure, multidirectional ultraviolet (UV) lithography, reverse-side exposure, rotational exposure, SU-8.

This paper presents the realization of a magnetic induction machine. The development of this machine is part of an ongoing project to create high-power density electric microgenerators for use in portable-power applications. The results reported here focus on testing a first-generation nonlaminated electromagnetic actuator, a metrology device designed for exploring and characterizing the fabrication process and the operating behavior of the magnetic induction micromachine. Achieving high power density requires large electrical currents and magnetic fluxes, which necessitate thick, multilayered microstructures that are difficult to fabricate. The batch-fabrication schemes developed as part of this work are based on low-temperature micromolding that makes extensive use of various ultra-thick photoresists and electroplating of electrical conductors (Cu) and ferromagnetic materials (Ni-Fe 80%-20%), resulting in the successful fabrication of a multilayer two-phase planar stator and a planar rotor. To evaluate the performance of the complete machine (stator plus rotor), a 4-mm-diameter, 500-[micro]-thick electroplated Ni-Fe rotor is tethered to a series of flexible structures that prevent it from making a complete revolution, but allow accurate torque performance extraction. The tethered induction micromotor studied here exhibits torque production as high as 4.8 [micro]N.m. [1436] Index Terms--Magnetic induction micromachine, micromolding, electroplating, tethers, micromotor.

This paper presents the design, fabrication, and characterization of laminated, magnetic induction machines intended for high-speed, high-temperature, high-power-density, silicon-based microengine power generation systems. Innovative fabrication techniques were used to embed electroplated materials (Cu, [Ni.sub.80][Fe.sub.20], [Co.sub.65][Fe.sub.18][Ni.sub.17]) within bulk-micromachined and fusion-bonded silicon to form the machine structures. The induction machines were characterized in motoring mode using tethered rotors, and exhibited a maximum measured torque of 2.5 [micro]N*m. [1466] Index Terms--AC generators, induction machines, magnetic materials, MEMS, micromachining.

We have demonstrated a high-sensitivity, room-temperature quantum-cascade (QC) laser sensor for detection of S[O.sub.2] and S[O.sub.3] under conditions relevant to aircraft test combustor exhaust. Two QC lasers probe infrared absorption features at 7.50 and 7.16 [micro]m for S[O.sub.2] and SQ, respectively, with a common dual-beam detection system. We inferred a noise-equivalent absorbance of ~1 x [10.sup.-4] [Hz.sup.-1/2]. We have demonstrated detection limits for both S[O.sub.2] and S[O.sub.3] of 1-2 ppmv m/[Hz.sup.1/2] (where ppmv is parts in [10.sup.6] by volume) for 300 torr, elevated temperature, and path lengths near i m. This level of sensitivity permits measurement of OCIS codes: 010.1120, 120.1740, 140.5760, 300.6340.

In many radio frequency (RF) microelectromechanical systems (MEMS) applications, currents are confined to the outermost portions of conductors due to the skin effect. Conductors consisting of polymer cores coated with metal, the so-called polymer-core conductor, are appropriate to consider for these applications, and in many instances are easier to fabricate than their solid-metal-core counterparts. Implementation of polymer-core conductors using an SU-8 epoxy-core patterning and subsequent metal electrodeposition is reported. The SU-8 core approach allows for relatively simple formation of extremely high-aspect-ratio columns for inductor sidewalls. In addition, an SU-8 bridge fabrication technique has been realized using a double exposure and single develop scheme. The bridge thickness has been characterized as a function of the optical dose and the post bake time in an oven. Three-dimensional, high-aspect-ratio, high Q-factor, solenoid-type RF inductors are fabricated and tested to demonstrate the feasibility of the polymer-core conductor approach for RF applications. A single, vialess metallization over SU-8 back-bone structure provides the complete conducting paths of the inductor. A single turn inductor that is 900 [micro]m in height and 600 [micro]m in lateral extension shows a maximum Q-factor of 84 and an inductance of 1.17 nH at 2.6 GHz. [1382] Index Terms--Double-exposure-single-development, epoxy-core conductor, high-aspect-ratio solenoid inductor, polymer-core conductor, radio frequency (RF) microelectromechanical systems (MEMS), SU-8 bridge fabrication.

The goal of this study was to design, fabricate, and test arrays of hollow microneedles for minimally invasive and continuous delivery of insulin in vivo. As a simple, robust fabrication method suitable for inexpensive mass production, we developed a modified-LIGA process to micromachine molds out of polyethylene terephthalate using an ultraviolet laser, coated those molds with nickel by electrodepostion onto a sputter-deposited seed layer, and released the resulting metal microneedle arrays by selectively etching the polymer mold. Mechanical testing showed that these microneedles were sufficiently strong to pierce living skin without breaking. Arrays containing 16 microneedles measuring 500 [micro]m in length with a 75 [micro]m tip diameter were then inserted into the skin of anesthetized, diabetic, hairless rats. Insulin delivery through microneedles caused blood glucose levels to drop steadily to 47% of pretreatment values over a 4-h insulin delivery period and were then approximately constant over a 4-h postdelivery monitoring period. Direct measurement of plasma insulin levels showed a peak value of 0.43 ng/ml. Together, these data suggest that microneedles can be fabricated and used for in vivo insulin delivery. Index Terms--Drug delivery systems, laser machining, micro-machining.

Fabrication methods for integrating thick (tens or hundreds of micrometers) electroplated metallic microstructures inside fusion-bonded silicon wafers are proposed and validated. Cu and [Ni.sub.80][Fe.sub.20] (permalloy) test structures were embedded inside of cavities in silicon wafers, which were fusion-bonded at 500[degrees]C for 4 h with nearly 100% yield. Resistance tests validated the electrical integrity of the metals after annealing, and magnetic measurements indicated the Ni-Fe maintained its magnetic performance after annealing. Additional mechanical tests verified a strong, uniform bond, and that the presence of the metals does not degrade the bond strength. These results demonstrate the ability to integrate conductive and magnetic materials in wafer-bonded silicon, a method useful for a variety of multiwafer, MEMS devices. [1276] Index Terms--Copper, encapsulation, micromachining, nickel alloys, permalloy, wafer handing.