This PDF file contains the front matter associated with SPIE Proceedings Volume 6556, including the Title Page, Copyright information, Table of Contents, Introduction, and the Conference Committee listing.

A complex MEMS device, microshutter array system, is being developed at NASA Goddard Space Flight Center for use as an aperture array for a Near-Infrared Spectrometer (NirSpec). The instrument will be carried on the James Webb Space Telescope (JWST), the next generation of space telescope after Hubble Space Telescope retires. The microshutter arrays (MSAs) are designed for the selective transmission of light with high efficiency and high contrast. Arrays are close-packed silicon nitride membranes with a pixel size close to 100x200 &mgr;m. Individual shutters are patterned with a torsion flexure permitting shutters to open 90 degrees with a minimized mechanical stress concentration. Light shields are made on to each shutter for light leak prevention so to enhance optical contrast. Shutters are actuated magnetically, latched and addressed electrostatically. The shutter arrays are fabricated using MEMS bulk-micromachining technologies and packaged using single-sided indium flip-chip bonding technology. The MSA flight concept consists of a mosaic of 2 x 2 format of four fully addressable 365 x 171 arrays placed in the JWST optical path at the focal plane.

We report on the design, fabrication, and simulation of a four-state pixelated subwavelength optical device that enables mid-wave infrared (MWIR) or long-wave infrared (LWIR) snapshot polarimetric imaging. The polarization information can help to classify imaged materials and identify objects of interest for remote sensing and military applications. The fabricated pixelated polarizers have measured extinction ratios larger than 100:1 for pixel sizes greater than 9 microns by 9 microns, with transmitted signals greater than 50%. That exceeds, by 7 times, previously reported device extinction ratios for 15 micron by 15 micron pixels. Traditionally, sequential polarimetric imaging sensors produce scenes with polarization information through a series of assembled images. Snapshot polarimetric imaging collects the spatial distribution of all four Stokes' parameters simultaneously. In this way any noise due to scene movement from one frame to the next is eliminated. In this paper, we will quantify near-field and diffractive effects of the finite pixel apertures upon detection. We have designed and built an experimental setup that models a pixel within a focal plane array (FPA) to measure crosstalk from adjacent gold wiregrid micropolarizers. This configuration simulates a snapshot polarization imaging device where the two substrates are stacked; micropolarizer array substrate on top of an FPA. Modeling and measured data indicate crosstalk between the adjacent pixels up to a few microns behind the polarizer plane. Crosstalk between adjacent pixels increases uncertainty in the measured polarization states in a scene of interest. Measured and simulated data confirm that the extinction ratio of a micropolarizer pixel in a super-cell will be reduced by 17% when moving the FPA from 0.5 microns to 1.0 microns away from the polarizer. These changes in extinction ratio are significant since typical glue separation is on the order of 10 microns.

This paper reports our recent fabrication effort in producing suspended-silicon-nanowire based static sensors, which is an extension to our previous theoretical and numerical studies. The static sensor consists of four suspended silicon dioxide microwires and one silicon dioxide microplate. Each side of the microplate includes two silicon dioxide microwires, instead of one, to avoid the possible torsion of the microplate and make the microplate remain parallel to the substrate before detection. Most of the bridges are curved, instead of being straight, as simulated with the FEA software previously. Silicon dioxide microbridges were fabricated, and gold/Ni was deposited on the bridge surface. The resulting deflection was observed with Roughness Step Tester (RST).

There is a need for ever-larger apertures for use in space based optical imaging systems. Requirements on optical instrumentation for future observations in space will place rigorous demands on wavefront quality. The design of such mirrors involves a balance between the utilization of ultra-lightweight mirror and support structures, and the active correction of the increased deformations due to these compromises in structural rigidity. Performing wavefront control with a primary mirror requires precision and stability over a large structure. The wavefront correction, therefore, can be partitioned in spatial frequency between the primary mirror and a tertiary deformable mirror (DM). To realize the full potential of new ultra-lightweight, active primary mirror, the large-stroke microactuator and DM technologies need to be developed. This paper presents a set of candidate components: linear microactuator technology and a piezoelectric unimorph-based large-stroke DM technology, in the context of a lightweight active mirror concept.

We propose dynamic range compression deconvolution by a new nonlinear optical limiter micro-electro-mechanical system (NOLMEMS) device. The NOLMEMS uses aperturized, reflected coherent light from optically addressed, parabolically deformable mirrors. The light is collimated by an array of micro-lenses. The reflected light saturates as a function of optical drive intensity. In this scheme, a joint image of the blurred input information and the blur impulse response is captured and sent to a spatial light modulator (SLM). The joint information on the SLM is read through a laser beam and is Fourier transformed by a lens to the back of the NOLMEMS device. The output from the NOLMEMS is Fourier transformed to produce the restored image. We derived the input-output nonlinear transfer function of our NOLMEMS device, which relates the transmitted light from the pinhole to the light intensity incident on the back side of the device, and exhibits saturation. We also analyzed the deconvolution orders for this device, using a nonlinear transform method. Computer simulation of image deconvolution by the NOLMEMS device is also presented.

In this paper, the fabrication, modeling and characterization of an all optically addressed spring patterned silicon-nitride deformable mirror Micro-Electro-Mechanical-System (MEMS) device is reported. This device is biased through combinations of high frequency AC and DC voltages. The experimentally verified theoretical modeling for this device shows mirror deflection saturation as a function of light intensity appropriate for dynamic range compression deconvolution. It was experimentally verified that the spring MEMS deformable mirror device has response up to 10 MHz, which opens the possibility of correcting supersonic turbulence as well as atmospheric turbulence.

The liquid core optical ring resonator (LCORR) sensor is a newly developed capillary-based ring resonator that integrates microfluidics with photonic sensing technology. The circular cross-section of the capillary forms a ring resonator that supports whispering gallery modes (WGM), which interact with the sample as it passes through the capillary. As in previous ring resonator sensor implementations, the interaction between the WGM evanescent field and the sample enables label-free detection. With a prototype of an LCORR sensor, we have achieved a refractive index detection limit of 10-6 RIU and a detection limit for protein of 2 pg/mm². Several engineering developments have been accomplished as well, including a thermal noise characterization, a thermal stabilization implementation, integration of the LCORR with a planar waveguide array, and electro-kinetic sample delivery. In the near future, the LCORR will be integrated into a dense 2-dimensional sensing array by integrating multiple capillaries with a chip-based waveguide array. This lab-on-a-chip sensing system will have a number of applications, including environmental sensing for defense purposes, disease diagnostics for medical purposes, and as a lab tool for analytical chemistry and molecular analysis.

Effective response to potentially dangerous environmental situations that can arise requires accurate and real time data on the environment that is being monitored. The ability to respond in an appropriate time frame is determined by the sensitivity and response time of the method used for monitoring. Fiber optic sensors have been used and are capable of detecting chemical compounds within an environment; however the sensitivity and response time of this detection method needs to be improved for many sensing applications. Improving these characteristics can be accomplished by designing the structure of the optical fiber sensor to allow increased response time and sensitivity. Through the introduction of new structures and control of these structures, the sensitivity and response time can be designed for a specific application. We have developed a novel porous optical fiber that has potential applications in chemical and biological agent sensing systems. Sensing capabilities of the optical fiber are a result of the structure that is designed into the fiber. The structure of the fiber developed, results of characterization of the fiber and the methods of analysis employed are presented. Methods used to analyze this new fiber optic sensor include nitrogen absorption porosity data, scanning electron microscopy and optical microscopy, and optical characterizations. The structure of the optical fiber is produced by controlling the processing parameters during the fiber draw as well as post processing stages. Fabrication methods and the processing steps that are used during the fiber optic production are also presented. Effect of altering processing conditions on the sensor structure is detailed and how this affects the performance of the fiber.

In this paper we will discuss a few basic concepts concerning the use of evanescent optical fields for the excitation of fluorescent chromophores placed near the interface. The observation of enhanced fluorescence from chromophores excited by surface plasmon and waveguide modes will be presented and discussed. We attribute the enhancement to the near-field interaction between the chromophores and the increased photonic mode density by surface plasmon and waveguide modes. We determined limits of detection (LOD) of DNA hybridisation using the same sensor architecture by surface plasmon fluorescence spectroscopy (SPFS) and optical waveguide fluorescence spectroscopy (OWFS). Both SPFS and OWFS techniques have the same detection principle using an enhanced electromagnetic field to excite fluorophores and make it possible to monitor DNA hybridisation in real-time with high sensitivity. The relative photonic mode density of each mode was calculated under the resonance condition, and these values are reflected in the LOD values.

An inexpensive, easily integrated, sensitive photoreceiver operating in the communications band with a 50-GHz bandwidth would revolutionize the free-space communication industry. While generation of 50-GHz carrier AM or FM signals is not difficult, its reception and heterodyning require specific, known technologies, generally based on silicon semiconductors. We present a 50 GHz photoreceiver that exceeds the capabilities of current devices. The proposed photoreceiver is based on a technology we call Nanodust. This new technology enables nano-optical photodetectors to be directly embedded in silicon matrices, or into CMOS reception/heterodyning circuits. Photoreceivers based on Nanodust technology can be designed to operate in any spectral region, the most important to date being the telecommunications band near 1.55 micrometers. Unlike current photodetectors that operate in this spectral region, Nanodust photodetectors can be directly integrated with standard CMOS and silicon-based circuitry. Nanodust technology lends itself well to normal-incidence signal reception, significantly increasing the reception area without compromising the bandwidth. Preliminary experiments have demonstrated a free-space responsivity of 50 &mgr;A/(W/cm²), nearly an order of magnitude greater than that offered by current 50-GHz detectors. We expect to increase the Nanodust responsivity significantly in upcoming experiments.

Whispering-gallery mode (WGM) resonators such as microspheres, microcylinders, and microrings have been proposed for telecommunication and sensing applications for decades. However, several challenges, such as the robustness of the optical coupling and sample delivery means, were often found in the path of developing them for the real world sensing applications. In this paper, a robust microring platform based on integrated lightwave circuit technology and a tunable laser interrogation system has been demonstrated as high-resolution refractive index and pressure measurement system. By using a "two-point" interrogation scheme and a microring with Q factor of about 24,000, a refractive index sensitivity of about 145 nm/RIU (TM mode) and 205 nm/RIU (TE mode) for two different polarizations and a limit of detection on the order of 10^-7 RIU have been demonstrated. For the high-pressure measurement applications, a pressure resolution of 0.05 psia has been achieved.

An optical microfiber is usually fabricated by drawing a conventional optical fiber and has a diameter of ~ 1 &mgr;m. A microfiber with a diameter significantly less than one micron is often called a nanofiber. This paper considers the potential applications of optical microfibers/nanofibers as sensors, which detect changes in the ambient medium by monitoring changes in the transmission power of light propagating along the MF. These changes may be caused by variation in temperature, radiation, concentration of chemical or biological species, microparticles, etc.

Microfluidic device detections of E. coli K12 in deionized (DI) water and E. coli in field water sample were demonstrated through static light scattering of latex immunoagglutination using proximity optical fibers. This method is a fully-automated, one-step detection, and requires neither sample pre-treatment nor cell culturing often required in many on-chip detections. We have used highly carboxylated polystyrene submicron latex particles without surfactants to enhance diffusional mixing and prevent non-specific bindings towards successful demonstration of latex immunoagglutination in microfluidic device. Detection of E. coli was performed by taking microscopic images from the view cell of a microfluidic device and counting the fractions of non-agglutinated and agglutinated particles. The limit of detection (LOD) was ca. 150 CFU ml-1 with this method for both E. coli K12 in DI water and E. coli in field water sample, indicating no non-specific bindings. Improved LOD of < 4.3 CFU ml-1 was achieved by measuring forward static light scattering from microfluidic device, using proximity optical fibers and a USB-powered miniature spectrometer. The total assay time for sample preparation (mostly dilutions) and on-chip assay (mostly injections and short incubation time) was < 10 min.

A small form factor microsensor system with optical MEMS devices is discussed in this paper. The key components in the microsensor system include a temperature and humidity sensor for environmental monitoring, a microprocessor for signal processing, and an optical MEMS device (active corner cube retroreflector or CCR) for remote free space optical communication. A flexible circuit design and a folded packaging scheme have been utilized to minimize the overall form factor. Flat, flexible polymer batteries are incorporated to minimize the vertical profile to a few millimeters. The entire fully packaged sensor system is about 30mmx30mmx6 mm. MEMS design of the CCR, fabrication, hermetic packaging of CCR, flexible circuit design and fabrication, flip chip bonding of die form microprocessor, and a battery replacement scheme for extended operation lifetime are crucial elements for the development of a real product for the microsensor system. Optical MEMS CCR is a torsion mirror design and was fabricated using surface micromachining with Si₃N₄ as a structural layer. A finite element analysis (FEA) model was developed to optimize design and performance of the MEMS structures. The sensor system has a miniature mechanical switch for local actuation and an optical switch for remote actuation. The applications of such a microsensor system include both tracking, tagging, locating (TTL) and remote sensing.

It is of interest to the optoelectronic community if index-tunable photonic crystals can be realized by using ferroelectric materials since the refractive index of ferroelectric materials can be electrically tuned through the electro-optic effect. In this paper, we present our work on developing a tunable one-dimensional (1D) photonic crystal (PC) based on a Ba_0.7Sr_0.3TiO₃/MgO multilayer structure. A ferroelectric 1D photonic crystal consisting of a Ba_0.7Sr_0.3TiO₃/MgO multilayer thin film was epitaxially deposited on a MgO (001) single-crystal substrate by pulsed laser deposition. A photonic band gap in the visible region is observed in the transmission spectrum of the multilayer thin film. The centre wavelength of the band gap is ~ 464 nm, which agrees with the simulation result obtained by the transfer matrix method. The band gap can be tuned by an external electric field E. The band gap shifts about 2 nm under a dc voltage of 240 V (E ~ 12 MV/m).

Tunable photonic crystals (PCs) have attracted much attention in the past decade because of their various applications such as ultra-fast optical filters and optical waveguides with add-drop functionalities. A common means of tuning PC is by changing the refractive indices of the constituent materials via the linear or quadratic electro-optic effect, which leads to a shift of the bandgap positions of the PC. The lead-free material, barium strontium titanate (BST), has a high quadratic electro-optic coefficient comparable to lanthanum-modified lead zirconate titanate (PLZT), and is a promising candidate as a lead-free tunable PC. Here we present a study on the feasibility of developing a one-dimensional tunable PC based on a BST and magnesium oxide (MgO) multilayer structure. The bandgap diagram of the PC structure is calculated using the plane-wave expansion (PWE) method. For a 1% change in the refractive index of BST, a 0.99% frequency shift in the bandgap can be achieved. It corresponds to a wavelength shift of 15.4 nm at a wavelength of 1550nm. Design of a tunable optical filter at a wavelength of 1550nm based on a BST/MgO 1D PC is suggested. The transmission property of the 1D PC is further verified by simulation, using the transfer matrix method (TMM).

Nano-patterning of metals on gold film and silicon nitride membrane using Dip Pen Nanolithography (DPN^TM) is reported in this study. Using this technique, nano-particles can be delivered or nano-scale features of metals can be deposited precisely at specific locations using the unique registration capabilities of DPN. Monolayers of metal salts (FeCl₂, FeCl₃, PdCl₂, etc.) are deposited with nano-scale precision using DPN. These metal salts can be subsequerntly reduced to pure metals in a reducing environment for various applications (e.g., magnetic memory storage, nano-catalysis, molecular electronics, brand protection, nano-sensors, etc.). Square nano-patterns of Palladium and Iron salts were successfully deposited using this technique with thickness of the deposited materials being less than 1 nm.

Precision nanoscale deposition is a fundamental requirement for much of current nanoscience research. Further, depositing a wide range of materials as nanoscale features onto diverse surfaces is a challenging requirement for nanoscale processing systems. As a high resolution scanning probe-based direct-write technology, Dip Pen Nanolithography® (DPN®) satisfies and exceeds these fundamental requirements. Herein we specifically describe the massive scalability of DPN with two dimensional probe arrays (the 2D nano PrintArray). In collaboration with researchers at Northwestern University, we have demonstrated massively parallel nanoscale deposition with this 2D array of 55,000 pens on a centimeter square probe chip. (To date, this is the highest cantilever density ever reported.) This enables direct-writing flexible patterns with a variety of molecules, simultaneously generating 55,000 duplicates at the resolution of single-pen DPN. To date, there is no other way to accomplish this kind of patterning at this unprecedented resolution. These advances in high-throughput, flexible nanopatterning point to several compelling applications. The 2D nano PrintArray can cover a square centimeter with nanoscale features and pattern 10⁷ &mgr;m² per hour. These features can be solid state nanostructures, metals, or using established templating techniques, these advances enable screening for biological interactions at the level of a few molecules, or even single molecules; this in turn can enable engineering the cell-substrate interface at sub-cellular resolution.

Nanoimprint is an emerging lithographic technology that promises high-throughput pattering of nanostructures. Based on the mechanical embossing principle, nanoimprint technique can achieve pattern resolutions beyond the limitations set by the light diffraction or beam scattering in other conventional techniques. The difficulty arises with the exact 90⁰ setting of the mould above the wafer. Proposed is the method of achieving this perpendicularity by the means of the crystallographic properties of Si or GaAs and the matrix made of the above-mentioned materials.

Conducting polymers have received much attention since their discovery in 1977. Applications of conducting polymer microsystems span from electronic devices to sensors. Traditional sensors had one-to-one correspondence between the detector and the target. Multiple conducting polymer micropattern arrays on a common substrate, when used for sensing, can effectively broaden the scope of a sensor. The Intermediate-layer lithography (ILL) technique was developed to generate multiple conducting polymer micropatterns, of desired dimensions on a common substrate. In this method, the sizes of the micropatterns can be scaled down effectively. Compared to films, micropatterns exhibited higher sensitivity at lower analyte concentrations. Also, the response of film sensors was not accurate when the conducting polymer film was partially covered, indicating that rare concentrations of analytes would be difficult to detect using the conventional conducting polymer film sensors. In the current work, conducting polymer micropatterns of varying dimensions have been fabricated using the ILL method and tested for their responses to organic vapors at low concentrations. The relationship between the surface-to-volume ratios of the micropatterns and their corresponding sensitivities is found for various target concentrations. The research results would provide insights regarding optimization of the micropattern sensors for maximizing their sensitivities.

In this work, conducting polymer-based heterojunctions, diodes and capacitors have been generated using an intermediate-layer lithography (ILL) approach which has been recently developed in our group. Polypyrrole (PPy) and poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS), Poly(methyl methacrylate) (PMMA) and aluminum were used as component materials in these devices. Compared with Si-based devices, conducting polymerbased devices have distinctive advantages of low weight and good flexibility, and may potentially replace the corresponding Si-based devices. A challenge is how to fabricate the conducting polymer-based microsystems. Most conducting polymers are sensitive to the environment, and their electrical properties tend to deteriorate over time due to overoxidation (air), moisture, high temperature and chemical alteration. The current fabrication techniques (e.g. lift-off, dry and wet etching processes) used in lithographic approaches involve ultra-violet, electron-beam, x-ray, gases (e.g., oxygen and nitrogen), DI water, and/or chemical solution (e.g. photoresist and acetone), making them improper to pattern conducting polymers. Since the ILL method does not involve aggressive chemistry in generation of patterns, it has been employed in this work to fabricate conducting polymer-based microdevices, particularly diodes and capacitors. In fabrication of the devices, multiple layers of polymers (e.g., PPy and PEDOT) and metals (e.g., Al) are coated on a PMMA sheet followed by the patterning with the insertion of Si molds. The detailed fabrication procedure and testing results are given in this paper.

Robotic reconnaissance operations are called for in extreme environments, not only those such as space, including planetary atmospheres, surfaces, and subsurfaces, but also in potentially hazardous or inaccessible operational areas on Earth, such as mine fields, battlefield environments, enemy occupied territories, terrorist infiltrated environments, or areas that have been exposed to biochemical agents or radiation. Real time reconnaissance enables the identification and characterization of transient events. A fundamentally new mission concept for tier-scalable reconnaissance of operational areas, originated by Fink et al., is aimed at replacing the engineering and safety constrained mission designs of the past. The tier-scalable paradigm integrates multi-tier (orbit atmosphere surface/subsurface) and multi-agent (satellite UAV/blimp surface/subsurface sensing platforms) hierarchical mission architectures, introducing not only mission redundancy and safety, but also enabling and optimizing intelligent, less constrained, and distributed reconnaissance in real time. Given the mass, size, and power constraints faced by such a multi-platform approach, this is an ideal application scenario for a diverse set of MEMS sensors. To support such mission architectures, a high degree of operational autonomy is required. Essential elements of such operational autonomy are: (1) automatic mapping of an operational area from different vantage points (including vehicle health monitoring); (2) automatic feature extraction and target/region-of-interest identification within the mapped operational area; and (3) automatic target prioritization for close-up examination. These requirements imply the optimal deployment of MEMS sensors and sensor platforms, sensor fusion, and sensor interoperability.

We propose a tuning method for Micro-Electro-Mechanical Systems (MEMS) gyroscopes based on evolutionary computation that has the capacity to efficiently increase the sensitivity of MEMS gyroscopes through tuning and, furthermore, to find the optimally tuned configuration for this state of increased sensitivity. We present the results of an experiment to determine the speed and efficiency of an evolutionary algorithm applied to electrostatic tuning of MEMS micro gyros. The MEMS gyro used in this experiment is a pyrex post resonator gyro (PRG) in a closed-loop control system. A measure of the quality of tuning is given by the difference in resonant frequencies, or frequency split, for the two orthogonal rocking axes. The current implementation of the closed-loop platform is able to measure and attain a relative stability in the sub-millihertz range, leading to a reduction of the frequency split to less than 100 mHz.

The development of advanced signal processing algorithms specifically for Micro/Nano Electro Mechanical Systems (MEMS/NEMS) based sensors has been largely unexplored and can be regarded as the single most important area for improving the performance of these devices. In this paper we present three classes of algorithms that were created to extract weak signals from devices operating in different sensing modalities. The first, stochastic resonance approach, named Active Signal Processing, depends on improving signal-to-noise ratio (SNR) by injecting noise into the measurement. ViaLogy invented and successfully demonstrated the Quantum Resonance Interferometry (QRI) algorithm, a quantum stochastic resonance (QSR)-based technique for improving SNR. QRI processing involves the QSR-based generation of a Quantum Expressor Function (QEF) for the sensor, encoding within it the noise environment, minimum level of detection, and the precision of measurement. Signal detection is achieved by the destruction of the resonance condition responsible for generating the system QEF. The next algorithm, also known as the "swept window" Maximum Aposteriori Probability algorithm, was developed for the case of signals with discrete statistics such as low analyte ion fluxes in mass spectrometers. Finally, a novel, ViaLogy-developed "Multi Scale Estimator" algorithm showed significant improvement over the Allan Deviation behavior of a state-of-the-art MEMS microgyroscope.

Micro Nano Technology-Based Systems (MNT-Based Systems) are expected to provide unprecedented capabilities for aerospace applications. However we have not sufficiently addressed the reliability of such systems for a number of reasons. For example, our foundational understanding of such systems is incomplete at the basic physics level and our understanding of how individual subsystems interact is much less than we originally assumed. In addition the manner in which we operate during the product realization cycle has large implications for the ultimate reliability we can expect to achieve. Currently it is quite difficult to determine the reliability of MNT-Based Systems and is in fact borne out by a number of estimates we have seen that are unsatisfactory. We shall discuss a number of issues that at present have slowed our progress in developing NMT-Based Systems and have deterred us from effectively ascertaining the true "reliability" of such systems.

We are developing micro chemical sensor nodes that can be used for real time, remote detection and early warning of chemical agent threats. The chemical sensors in our sensor nodes utilize GaN HEMTs (High Electron Mobility Transistors) fabricated with catalytically active transition metal gate electrodes. The GaN HEMT chemical sensors exhibit high sensitivity and selectivity toward chemical agent simulants such as DECNP (Diethyl cyano phosphonate), and this is the first time that chemical agent simulants have been detected with GaN micro sensors. Response time of the GaN HEMT sensor to a chemical species is within a second, and the maximum electronic response speed of the sensor is ~3 GHz. A prototype micro chemical sensor node has been constructed with the GaN sensor, a micro controller, and an RF link. The RF sensor node is operated with a single 3V Li battery, dissipating 15 mW during the RF transmission with 5 dBm output power. The microcontroller allows the operation of the RF sensor nodes with a duty cycle down to 1 %, extending lifetime of the RF sensor nodes over 47 days. Designed to transmit RF signals only at the exposures to chemical agents and produce collective responses to a chemical agent via a sensorweb, the GaN micro chemical sensor nodes seem to be promising for chemical agent beacons.

Recently, we discovered that the nanoporous zeolite materials possess the unique combination of optical and chemical properties suitable for developing highly sensitive chemical sensors. This paper summarizes our recent work in developing such highly sensitive chemical sensors by functionally integrating zeolite thin films with optical fiber devices. These include the zeolite Fabry-Perot interferometric sensor and the zeolite thin film-coated thermal long period fiber grating sensor. Both types of sensors operate by monitoring the adsorption-induced optical refractive index changes in the zeolite thin film. The sensors were tested using various organic chemicals with different molecular sizes and in both vapor and liquid phases.

A cold cathode field emission electron gun (e-gun) based on a patterned carbon nanotube (CNT) film has been fabricated for use in a miniaturized reflectron time-of-flight mass spectrometer (RTOF MS), with future applications in other charged particle spectrometers, and performance of the CNT e-gun has been evaluated. A thermionic electron gun has also been fabricated and evaluated in parallel and its performance is used as a benchmark in the evaluation of our CNT e-gun. Implications for future improvements and integration into the RTOF MS are discussed.

Microcantilevers (MCs) as state-of-art sensor platforms have been widely investigated. We recently introduced a new type of MC, magnetostrictive microcantilever (MSMC), as high performance sensor platform. The MSMC is a remote/wireless sensor platform and exhibits a high quality merit factor in liquid. In this paper, a MSMC-based biosensor is developed for detecting B. anthracis spores in liquid, a potential biothreaten agent. The results demonstrated the advantages of MSMCs as a sensor platform. MSMCs with different sizes were fabricated and utilized in the experiments. The MSMCs were coated with the filamentous phage as a bio-recognition element to capture the B. anthracis spores. The phage-coated MSMCs as biosensors were exposed to cultures containing target spores with concentrations ranging from 5 * 10⁴ spores/mL to 5 * 10⁸ spores/mL. The resonance frequency of the MSMC sensors in cultures was monitored in a real-time manner. The results showed that for MSMCs of 2.8 mm * 1.0 mm * 35 &mgr;m and with 1.4 mm * 0.8 mm * 35 &mgr;m have a detection limit of 10⁵ and 10⁴ spores/mL, respectively.

The need for smaller and less expensive MIL-STD 1901A compliant safe and arm-fire (S&A/A-F) devices to safely initiate rocket motors requires a better understanding of energetic initiation and firing train functionality. Applications broadly include NLOS artillery rocket-assist motors, high I_sp miniature thrusters for UAVs, composite molded thrusters for hypersonic flow temperatures, and smart munitions. Every energetic system needs an initiation mechanism. For the past decade, many groups have worked on reducing the footprint of these systems through batch processing and miniaturization. However, the typical miniaturization and semiconductor-style benefits such as "faster, smaller, cheaper" are only now being investigated for micro-energetics. Advancement of this field requires key breakthroughs in the following areas: 1) a SAFE and batch micro-energetics deposition and patterning step, 2) The compatibility of subsequent (post or pre) MEMS processing steps, 3) better understanding of the micro-initiation energetic train, and 4) special environmental standards for the manufacturer and specialized product qualification/testing. This body of work spotlights 'low-cost' MEMS-based initiators, typical chemical compounds used today in the industry and the associated sensitivities and dangers to be encountered. The micro-scale firing trains required for smart munitions, including warhead and propellant applications, can be made multifunctional for use with legacy and IM-compliant energetics. Methods of focusing industry on reliability and the importance of characterizing formulation, composition, and performance will also be discussed. Most importantly, however, is the need to focus industry on implementing a low-cost micro initiator methodology.

Microthrusters are critical for the development of terrestrial micromissiles and nano air vehicles for reconnaissance, surveillance, and sensor emplacement. With the maturation of MEMS manufacturing technology, the physical components of the thrusters can be readily fabricated. The thruster type that is the most straightforward is chemical combustion of a propellant that is ignited by a heating element giving a single shot thrust. Arrays of MEMS manufactured thrusters can be ganged to give multiple firings. The basic model for such a system is a solid rocket motor. The desired elements for the propellant of a chemical thruster are high specific impulse (I_sp), high temperature and pressure, and low molecular weight combustion gases. Since the combustion chamber of a microthruster is extremely small, the propellant material must be able to ignite, sustain and complete its burn inside the chamber. The propellant can be either a solid or a liquid. There are a large number of energetic materials available as candidates for a propellant for microthrusters. There has been no systematic evaluation of the available energetic materials as propellant candidates for microthrusters. This report summarizes computations done on a series of energetic materials to address their suitabilities as microthruster propellants.

Polymers that contain conjugated molecules can change their index of refraction upon bonding with high explosive molecules. These polymers can be incorporated into micro-ring resonators as trace explosive sensor. Since the resonator cavity itself is made of sensing material, the detection is intrinsic, which may lead to higher sensitivity and faster response than other fiber optic chemical sensors. Photobleaching was used for the fabrication of the microrings resonators. The sensor has shown ppb level of sensitivity to the vapor of an explosive stimulant 2,4- dinitrotoluene and is insensitive to common chemical pollutants including nitrates, sulfates and phosphates.

Flexural plate wave (FPW) device is one of promising devices for biological sensor application, because its electronic circuit can be isolated from the medium being detected, and it shows low acoustic energy loss in liquid medium. Moreover, FPW device arrays on the silicon based substrate can be possible at low cost fabrication by micromachining technology, so that it offers batch processing for economic sensor fabrication. In this study, piezoelectric ZnO film was chosen as a material for a biological sensor platform, due to non-toxicity, and chemical and thermal stability. RF magnetron sputtering and chemical solution deposition (CSD) were investigated as film fabrication method. To launch and receive the acoustic wave through the piezoelectric material, it is required that the piezoelectric ZnO film have strong c-axis orientation in the device. For the magnetron RF sputtering, process parameters such as gas ratio, substrate types, and temperature, were varied, and heat treatment and substrate types for CSD. Results indicated that the preferred orientation and microstructure of ZnO films can be controlled by the variation of the process parameter, and that uniform and dense microstructures of ZnO films were obtained by both fabrication methods. CSD method showed, however, stronger dependence of the preferred orientation on substrate types while less dependence on the substrates for sputtering due to energetic sputtered species. Mechanism for ZnO thin film growth will be discussed. FPW devices have been successfully integrated onto 4 inch Si-wafer with 22 different interdigitated electrodes designs, and the device demonstrated the capability to detect biological quantity of 446.13 cm²/gram of sensitivity.

Piezoelectric micromachined ultrasonic transducer (pMUT) consisting of a piezoelectric capacitor built on a micromachined silicon membrane has been used for ultrasound transmitting and sensing. It typically operates at the fundamental flexural vibration frequency, where maximum sensitivity can be achieved, and is insensitive at higher order of resonances because the harmonic signals generated from different parts of the diaphragm tend to cancel with each other. This leads to a very narrow bandwidth. In this paper, rectangular-shaped pMUTs for dual-frequency application are proposed and fabricated using piezoelectric P(VDF-TrFE) copolymer coating and silicon micromachining technologies. The electrode patterns are properly designed to efficiently make use of both (0, 0) and (2, 0) vibration modes of the rectangular membrane. By adjusting the length and width of the diaphragm, the ratio of the two frequencies can be varied on demand within a wide range. The corresponding design principles are also useful for other micromachined devices such as surface acoustic wave devices, delay lines, resonators, etc.

In this Paper we present growth and characterization of ZnO nanowires on a variety of substrates, such as Silicon and SiC. Experimental results on the ZnO nanowires grown on Si and SiC are presented with growth morphology, structure analysis, and dimensionality control. The ZnO nanowires can be used for a variety of nanoscale optical and electronics sensors.

Conducting polymers, because of their promising potential to replace silicon and metals in building devices, have attracted great attention since the discovery of high conductivity in doped polyacetylene in 1977. Lithographic techniques present significant technical challenges when working with conducting polymers. Sensitivity of conducting polymers to environmental conditions (e.g., air, oxygen, moisture, high temperature and chemical solutions) makes current photolithographic methods unsuitable for patterning the conducting polymers due to the involvement of wet and/or dry etching processes in those methods. Existing non-photolithographic approaches have limitations in throughput, resolution or electrical insulation. Therefore, an intermediate-layer lithography (ILL) approach has been recently developed by my group to produce conducting polymer micro/nanostructures. In the ILL method, an intermediate layer of an electrically insulating polymer is coated between the substrate and a layer of the conducting polymer to be printed. Subsequently, the conducting polymer is printed through mold insertion using a hot-embossing process. The current hot-embossing based methods face the obstacles of residual layer and depth of field (i.e., the height variation in the mold structures). In contrast, the ILL approach does not leave a residual layer in the material of interest, making conducting polymer patterns isolated from one another and avoiding the shorting problem in the electrical applications of these patterns. Furthermore, in the ILL, the height variation potentially existing among the mold structures has been transferred to the intermediate layer, ensuring that all patterns in the mold have been properly transferred to the conducting polymer layer. In addition to conducting polymers, the ILL can also be applied to pattern metals as well as other types of polymers. This paper gives a review of this ILL method and reports the results that we have achieved to date.

A new thinning and trimming approach has been explored to produce silicon nanowires (SiNWs) from silicon microwires. One-dimensional nanostructures have attracted great attention recently because of their potential applications as excellent components in micro/nanodevices. SiNWs in particular have received much attention since silicon is the most widely used material in integrated-circuit and microfabrication processes and has unique mechanical and electrical properties. However, due to the shortcomings of the existing fabrication approaches, new methods are needed to produce SiNWs that can not only be massively fabricated but also batch integrated to functional devices. The developed thinning and trimming approach is believed to be such a method, and would permit precise control of the structure, size and positions of SiNWs. Furthermore, this method may be used to break through the limitation of lithography in the sense that silicon features fabricated by any lithographic methods can be further miniaturized using this approach. Our progress on developing this new thinning and trimming approach is detailed in this paper.