Robert Osiander

Terahertz spectroscopy techniques for explosives detection.

Spectroscopy in the terahertz frequency range has demonstrated unique identification of both pure and military-grade explosives. There is significant potential for wide applications of the technology for nondestructive and nonintrusive detection of explosives and related devices. Terahertz radiation can penetrate most dielectrics, such as clothing materials, plastics, and cardboard. This allows both screening of personnel and through-container screening. We review the capabilities of the technology to detect and identify explosives and highlight some of the critical works in this area.

Spectroscopic characterization of explosives in the far-infrared region

Far infrared spectra of 14 commonly used explosive samples have been measured by using Fourier Transform Infrared Spectroscopy (FTIR) and THz Time-Domain Spectroscopy (THz TDS). New absorption resonances between 20 cm-1 and 650 cm-1 are reported. Below 20 cm-1, no clear absorption resonances are observed in all the explosives. There is a good consistency of far-IR spectrum measured by Far-FTIR and by THz TDS in explosives 3,5-DNA and 2,4-DNT. Observed far-IR spectrum of TNT is compared with a previously reported theoretical calculation.

Wafer-level assembly of carbon nanotube networks using dielectrophoresis

We use dielectrophoresis (DEP) to controllably and simultaneously assemble multiple carbon nanotube (CNT) networks at the wafer level. By an appropriate choice of electrode dimensions and geometry, an electric field is generated that captures CNTs from a sizable volume of suspension, resulting in good CNT network uniformity and alignment. During the DEP process, the electrical characteristics of the CNT network are measured and correlated with the network morphology. These experiments give novel insight into the physics of DEP assembly of CNT networks, and demonstrate the scalability of DEP for future device applications.

MEMS and Microstructures in aerospace applications

OVERVIEW OF MICROELECTROMECHANICAL SYSTEMS AND MICROSTRUCTURES IN AEROSPACE APPLICATIONS Robert Osiander and M. Ann Garrison Darrin VISION FOR MICROTECHNOLOGY SPACE MISSIONS Cornelius J. Dennehy MEMS FABRICATION James J. Allen IMPACT OF SPACE ENVIRONMENTAL FACTORS ON MICROTECHNOLOGIES M. Ann Garrison Darrin SPACE RADIATION EFFECTS AND MICROELECTROMECHANICAL SYSTEMS Stephen P. Buchner MICROTECHNOLOGIES FOR SPACE SYSTEMS Thomas George and Robert Powers MICROTECHNOLOGIES FOR SCIENCE INSTRUMENTATION APPLICATIONS Brian Jamieson and Robert Osiander MICROELECTROMECHANICAL SYSTEMS FOR SPACECRAFT COMMUNICATIONS Bradley Gilbert Boone and Samara Firebaugh MICROSYSTEMS IN SPACECRAFT THERMAL CONTROL Theodore D. Swanson and Philip T. Chen MICROSYSTEMS IN SPACECRAFT GUIDANCE, NAVIGATION, AND CONTROL Cornelius J. Dennehy and Robert Osiander MICROPROPULSION TECHNOLOGIES Jochen Schein MEMS PACKAGING FOR SPACE APPLICATIONS R. David Gerke and Danielle M. Wesolek HANDLING AND CONTAMINATION CONTROL CONSIDERATIONS FOR CRITICAL SPACE APPLICATIONS Philip T. Chen and R. David Gerke MATERIAL SELECTION FOR APPLICATIONS OF MEMS Keith J. Rebello RELIABILITY PRACTICES FOR DESIGN AND APPLICATION OF SPACE-BASED MEMS Robert Osiander and M. Ann Garrison Darrin ASSURANCE PRACTICES FOR MICROELECTROMECHANICAL SYSTEMS AND MICROSTRUCTURES IN AEROSPACE M. Ann Garrison Darrin and Dawnielle Farrar INDEX

Microelectromechanical devices for satellite thermal control

Future space missions will include constellations of spacecraft, including nano- and picosatellites, where adaptive thermal control systems will be needed that fit the constraints of space applications with limited power and mass budgets. A microelectromechanical systems (MEMS) solution has been developed that will vary the emissivity on the surface of the small satellite radiator. The system is based on louver thermal controllers, where panels are mechanically positioned to modulate the effective radiator surface area. This system consists of MEMS arrays of gold-coated sliding shutters, fabricated with the Sandia ultraplanar, multilevel MEMS technology fabrication process, which utilizes multilayer polycrystalline silicon surface micromachining. The shutters can be operated independently to allow digital control of the effective emissivity. This first demonstrator technology is limited in the possible emittance range to a 40% change. Early prototypes of MEMS louvers that open away from the structure have shown the capability of a much wider dynamic range. The first generation of this active thermal management system will be demonstrated on NASAs New Millennium Program ST-5 spacecraft. With the opportunity to validate the MEMS thermal control technology in space on ST-5, lightweight, low-power MEMS radiators offer a possibility for flexible thermal control on future nanosatellites.

Ultrafast laser-based spectroscopy and sensing: applications in LIBS, CARS, and THz spectroscopy.

Ultrafast pulsed lasers find application in a range of spectroscopy and sensing techniques including laser induced breakdown spectroscopy (LIBS), coherent Raman spectroscopy, and terahertz (THz) spectroscopy. Whether based on absorption or emission processes, the characteristics of these techniques are heavily influenced by the use of ultrafast pulses in the signal generation process. Depending on the energy of the pulses used, the essential laser interaction process can primarily involve lattice vibrations, molecular rotations, or a combination of excited states produced by laser heating. While some of these techniques are currently confined to sensing at close ranges, others can be implemented for remote spectroscopic sensing owing principally to the laser pulse duration. We present a review of ultrafast laser-based spectroscopy techniques and discuss the use of these techniques to current and potential chemical and environmental sensing applications.

A microelectromechanical‐based magnetostrictive magnetometer

The principles of operation of a microelectromechanical (MEMS)‐based magnetometer designed on the magnetoelastic effect are described. The active transduction element is a commercial (001) silicon microcantilever coated with an amorphous thin film of the giant magnetostrictive alloy Terfenol‐D [(Dy0.7Te0.3)Fe2]. In addition to the magnetostrictive transducer, basic components of the magnetometer include: (a) mechanical resonance of the coated‐microcantilever through coupling to an ac magnetic field; and (b) detection by optical beam deflection of the microcantilever motion utilizing a laser diode source and a position‐sensitive detector. Currently, the sensitivity of this MEMS‐based magnetostrictive magnetometer is ∼1μT.

Micromachined polysilicon resonating xylophone bar magnetometer

Abstract The basic device principles, including response sensitivity and transduction schemes, are outlined for a resonating xylophone bar magnetometer. Advanced design emphasis is on a polysilicon version with dimensions of order microns fabricated by microelectromechanical systems (MEMS) processing techniques. All polysilicon devices tested to date have performed extremely well in static magnetic fields and exhibit mechanical quality factors, Q, of up to 30,000 at reduced pressures. The resonance frequencies of the fundamental mode of vibration of these polysilicon xylophone bars have been found to be sensitive functions of the torsional stiffness of the support arms, in accord with an analytical model based on Bernoulli–Euler theory. The output response of the polysilicon xylophone magnetometer as a function of impressed magnetic flux density has been shown to be linear up to 150 μT ; however, sensitivity is currently limited by the significant resistivity of the polysilicon xylophone bar. Various strategies are being implemented to bring the magnetometer sensitivity into the applications-dominated nT regime.

Time-resolved infrared radiometry with step heating. A review

Abstract In contrast to most infrared radiometry techniques used for nondestructive evaluation which follow the sample cooling after pulsed heating, the technique termed time-resolved infrared radiometry with step heating (TRIR) follows the surface temperature rise as a function of time during the heating pulse. This approach allows identification of subsurface features and determination of thermal properties with the same speed as other thermal techniques, but keeps the required heating power and resulting surface temperature small. This permits the use of heat sources such as microwaves and RF induction heating where high peak power is often not available. One of the most attractive features of the TRIR method is the ability to calibrate the temperature response early, when the sample is thermally-thick. This allows correction for inhomogeneous heat source distributions and differentiation between backing materials. A fast algorithm has been developed to calculate thermal transit times and therefore generate quantitative depth images of subsurface features. This paper will describe the TRIR approach and the analysis of its time response, including the calibration at early times. Examples will be described for laser heating on zirconia coatings, corroded aluminum, and graphite composites, and the use of microwaves and RF induction heating as heating sources.

A high sensitivity, wide dynamic range magnetometer designed on a xylophone resonator

A novel magnetometer based on a classical xylophone resonator is described. The device consists of an aluminum bar supported by two wires placed at the nodal points of the fundamental resonance frequency. The wires also supply current of this frequency to the bar. In the presence of a magnetic field, the Lorentz force causes the resonator to vibrate. The amplitude of this vibration is proportional to a vector component of the magnetic field. The device is intrinsically linear, and by altering the drive current the sensitivity can range from nanoteslas to teslas.