The motivation for the work reported is portable NMR spectroscopy of liquids and solids with higher sensitivity than inductive detection and without the need for tuned elements specific to the frequency of each isotope observed. The fabrication and assembly of a BOOMERANG force-detected nuclear magnetic resonance (NMR) spectrometer is reported. The design is optimal for samples of ~ 50 micron diameter and realizes tolerances of ~1 micron in the Si and ferromagnetic parts. Optical lithography, electrodeposition, reactive ion etching, and release of the moving part by solution etching are key methods used. Resistance to delamination of the ferromagnetic material was achieved by Cr/Au deposition prior to electrodeposition of 85/15 Co:Ni.

A CMOS digital microcircuit, utilizing sub-micron technology, was designed for the purpose of providing integrated control circuitry to an array of high-voltage micro-electromechanical systems (MEMS) switch based phase shifter devices. The grid of MEMS phase shifters is part of a phased array antenna system. The phase of each element of the array is controlled via the CMOS microcircuit. This paper presents the design, physical layout, and the measured test results for CMOS digital control circuit that has been fabricated using the MOSIS Integrated Circuit Fabrication Service. The circuit converts serial data to parallel outputs to reduce number of control lines and lower the cost of wiring the phased array. In addition, discrete digital control circuitry for loading phase shifts into each MEMS device is presented.

This paper presents the design, analysis, and testing of a diffractive optical element (DOE) to be part of the Lunar Orbiter Laser Altimeter (LOLA) instrument scheduled to launch in 2008. LOLA will be one of six instruments to orbit the Moon for a year or more as part of the Lunar Reconnaissance Orbiter (LRO). The various scientific instruments aboard the LRO will map the lunar environment in greater detail than ever before. LOLA will produce a topographic map of the Moon from a nominal 50km orbit during the one-year mission. LOLA works by bouncing laser pulses off the lunar surface as it orbits the Moon. By measuring the time it takes for light to travel to the surface and back, LOLA can calculate the roundtrip distance. Each pulse consists of five laser spots in a cross-like pattern spanning about 50 meters of the lunar surface. The spots are generated by a DOE from the single, collimated LOLA laser input beam. It is projected that LOLA will gather more than a billion measurements of the Moon's surface elevation creating a high resolution three-dimensional map of the surface.

This paper presents MEMS deformable-mirror technology under development at Iris AO. The hybrid approach uses surface-micromachining techniques to fabricate actuator arrays. High-fill-factor mirror arrays are flip-chip bonded on top of these actuator arrays. The single-crystal-silicon mirror segments provide robust substrates for optical coating with excellent surface quality (6-20 nm rms surface-figure errors). The hexagonally close-packed segments are 350 μm on a side, and can thus provide high-spatial frequency corrections in a small form factor. High-stroke actuation of greater than >7.5 μm has been experimentally verified while keeping actuation voltages within reasonable bounds (<130 V). Three electrodes under each actuator allow for piston/tip/tilt motion. An open-loop controller has been demonstrated to position a 37-segment array resulting in a flattened array with only 19 nm rms of surface figure error.

Sandia National Laboratories has a long tradition of technology development for national security applications. In recent years, significant effort has been focused on micro-analytical systems - handheld, miniature, or portable instruments built around microfabricated components. Many of these systems include microsensor concepts and target detection and analysis of chemical and biological agents. The ultimate development goal for these instruments is to produce fully integrated sensored microsystems. Described here are a few new components and systems being explored: (1) A new microcalibrator chip, consisting of a thermally labile solid matrix on an array of suspended-membrane microhotplates, that when actuated delivers controlled quantities of chemical vapors. (2) New chemical vapor detectors, based on a suspended-membrane micro-hotplate design, which are amenable to array configurations. (3) Micron-scale cylindrical ion traps, fabricated using a molded tungsten process, which form the critical elements for a micro-mass analyzer. (4) Monolithically integrated micro-chemical analysis systems fabricated in silicon that incorporate chemical preconcentrators, gas chromatography columns, detector arrays, and MEMS valves.

Recent terrorists events have shown that an urgent and widespread need exists for development of novel sensors for chemical and biowarfare agents. The advent of inexpensive, mass-produced microcantilever sensors, promises to bring about a revolution in detection of terrorists threats. Extremely sensitive chem/biosensors can be developed using microcantilever platform. Both frequency and bending of microcantilevers can be used to detect the chemical and biological species in air or solution. The specificity is achieved by immobilizing chemically-specific receptors the cantilever. This short report will give an overview of chemical/biological warfare agents sensor recently developed based on microcantilevers.

The discovery of high conductivity in doped polyacetylene in 1977 (garnering the 2000 Nobel Prize in Chemistry for the three discovering scientists) has attracted considerable interest in the application of polymers as the semiconducting and conducting materials due to their promising potential to replace silicon and metals in building devices. Previous and current efforts in developing conducting polymer microsystems mainly focus on generating a device of a single function. When multiple micropatterns made of different conducting polymers are produced on the same substrate, many microsystems of multiple functions can be envisioned. For example, analogous to the mammalian olfactory system which includes over 1,000 receptor genes in detecting various odors (e.g., beer, soda etc.), a sensor consisting of multiple distinct conducting polymer sensing elements will be capable of detecting a number of analytes simultaneously. However, existing techniques present significant technical challenges of degradation, low throughput, low resolution, depth of field, and/or residual layer in producing conducting polymer microstructures. To circumvent these challenges, an intermediate-layer lithography method developed in our group is used to generate multiple micropatterns made of different, commonly used conducting polymers, Polypyrrole (PPy), Poly(3,4-ethylenedioxy)thiophene (PEDOT) and Polyaniline (PANI). The generated multiple micropatterns are further used in an "electronic nose" to detect water vapor, glucose, toluene and acetone.

Effective and rapid detection of nitroaromatic explosive compounds, especially trinitrotoluene (TNT), is very important to homeland security as well as to environmental monitoring of contaminants in soil and water, and landmine detection. In this research, we explore a novel nanoscale flagellar motor based TNT detection system (nFMTNT). The nFMTNT is a bio-hybrid MEMS system which combines genetically engineered flagellar motors and MEMS devices. The system consists of three major components: (1) a non-pathogenic, genetically modified Escherichia coli strain KAF95 with a rotating flagellar filament, (2) a microchannel with tethered cells, and (3) a sub-micron bead attached to a rotating flagellar filament. The operational principle of nFMTNT is based on detecting the change in the rotational behavior of the nanoscale flagellar filament in the presence of TNT. The rotational behavior of flagellar filaments of E. coli KAF95 was shown to be extremely sensitive to the presence of nitrate or nitrite. Normally, the flagellar filaments were locked in to rotate in the counterclockwise direction. However, when a nitrate or nitrite was present in the immediate environment, the filaments cease to rotate. Our results indicate that the threshold concentrations required for this response were 10^-4 M for nitrate and 10^-3 M for nitrite. This is equivalent to around 10 pg of nitrate and 100 pg of nitrite, based on the dimension of the MEMS-based reaction system used for the experiment (400 μm × 100 μm × 40 μm). These detection limits can be even lower when the size of the system is reduced.

The central goal of our work is to combine semiconductor nanotechnology and surface functionalization in order to build platforms for the selective detection of bio-organisms ranging in size from bacteria (micron range) down to viruses, as well as for the detection of chemical agents (nanometer range). We will show on three porous silicon platforms how pore geometry and pore wall chemistry can be combined and optimized to capture and detect specific targets. We developed a synthetic route allowing to directly anchor proteins on silicon surfaces and illustrated the relevance of this technique by immobilizing live enzymes onto electrochemically etched luminescent nano-porous silicon. The powerful association of the specific enzymes with the transducing matrix led to a selective hybrid platform for chemical sensing. We also used light-assisted electrochemistry to produce periodic arrays of through pores on pre-patterned silicon membranes with controlled diameters ranging from many microns down to tens of nanometers. We demonstrated the first covalently functionalized silicon membranes and illustrated their selective capture abilities with antibody-coated micro-beads. These engineered membranes are extremely versatile and could be adapted to specifically recognize the external fingerprints (size and coat composition) of target bio-organisms. Finally, we fabricated locally functionalized single nanopores using a combination of focused ion beam drilling and ion beam assisted oxide deposition. We showed how a silicon oxide ring can be grown around a single nanopore and how it can be functionalized with DNA probes to detect single viral-sized beads. The next step for this platform is the detection of whole viruses and bacteria.

Microfabrication not only enables the miniaturization of sensors and instruments, it also enables novel function and capability not accessible to the macro versions. For biomedical applications small size means less invasive, greater spatial resolution, and/or the ability to process small sample volumes. Miniaturization has additional advantages for space applications such as reduced launch payload, compact flight storage, and ease of redundancy. Several, demonstrated biomedical microinstruments are described here illustrating new capabilities arising from descending scale.

High sensitivity and high Q value, as well as working well in liquid, make the newly developed magnetostrictive microcantilevers (MSMCs) a great candidate for developing a high performance biosensor. In this paper, blood cell identification by the MSMCs was demonstrated. The MSMCs were fabricated and their surface was functionalized by immobilizing anti-B antibody as the bioreceptor for blood cells inspection. By immersing the MSMCs into different type blood cells and monitoring the resonance frequency shift, due to blood cell binding, the blood cells A and B were distinguished.

Magnetostrictive particles (MSPs) as biosensor platform have been developed recently. The principle of MSPs as sensor platform is the same as that of other acoustic wave devices, such as quartz crystal microbalance. In this paper, the fabrication, characterization and performance of phage-based MSP biosensors for detecting Bacillus anthracis spores are reported. A commercially available magnetostrictive alloy was utilized to fabricate the sensor platform. The phage was immobilized onto the MSPs using physical adsorption technology. The following performance of the phage-based MSP sensors will be presented: sensitivity, response time, longevity, specificity and binding efficacy. The performance of the sensors at static and dynamic conditions was characterized. The experimental results are confirmed by microscopy photographs. The excellent performance including high sensitivity and rapid response is demonstrated. More importantly, it is experimentally found that the phage-based MSP sensors have a much better longevity than antibody-based sensors.

Optical ring resonators in the form of a microsphere or microcylinder of a few tens to a few hundreds of μm in diameter represent a new sensing mechanism and have recently drawn increasing attention in bio/chemical sensor development. In a ring resonator, the light circulates along the inner surface in the form of the whispering gallery modes (WGMs) resulting from total internal reflection. Due to the high Q-factor of the WGM, the effective interaction length between the light and the analytes can be 10-100 cm long, despite the sensor's micrometer dimensions. Successful feasibility demonstrations of a single ring resonator sensor have stimulated further investigation on photonic and fluidic integration. In this paper, we present a novel bio/chemical sensor platform based on a liquid core optical ring resonator (LCORR) architecture that takes advantage of the high sensitivity associated with ring resonators and easy sample delivery associated with the hollow core columns. This structure allows for separate engineering of the fluidics and photonics and is well-suited for a 2-D sensor array. The potential result is a micro-sized sensing system capable of detecting multiple agents simultaneously while providing redundancy to reduce false positives. In addition, the sample detection volume can be as low as 100 pL. Here we present an LCORR with a Q-factor of 500,000 (2 pm mode linewidth) and a refractive index sensitivity of 7 nm/RIU. Also, we demonstrate the detection of bovine serum albumin adsorbing to the inner surface as the sample is pumped through the LCORR.

Methods for fabricating high frequency ultrasound transducer and array based on piezoelectric films and MEMS technology are presented in this paper. Piezoelectric PZT films up to 30 μm-thick deposited on silicon substrate have been prepared by a modified sol-gel process. The raw materials included lead acetate trihydrate and zirconium n-propoxide and titanate isoproxide. The sol-gel PZT solutions were prepared using above materials and 2-methoxyethanol as the solvent. Spin-coated films were annealed at 750 ^oC by a rapid thermal annealing (RTA) process. Thicker PZT films were fabricated by repeating this process and using a modified PZT composite solution. The high frequency single element transducers actuated by the PZT films were fabricated and pulse-echo measurement results show the transducers had a broad bandwidth and high central frequencies. The beam profile of one 103 MHz transducer was measured using a 8 μm diameter wire and a lateral resolution of 33 μm was observed. A micromachined process to fabricate high frequency linear array will be also presented.

In last few years, with the strong progress in thin film technologies for complex materials systems such as PZT, ZnO and AlN, thin film bulk acoustic wave resonator (FBAR) and filter concepts are gaining more and more importance for microwave frequency control applications. For resonators operating in the GHz range, piezoelectric thin film layer in the order of a few microns with desirable electromechanical properties (high Q and wide bandwidth) is required. Among these materials, AlN is very attractive due to that it has a number of interesting properties such as high thermal conductivity, high electrical insulation, and highly chemical stability. These characteristics make it possible to design and fabricate high frequency resonators and bandpass filters for signal processing and communication devices. If the thin film bulk acoustic resonator devices of sufficient performance can be fabricated, they will be the best choice to replace the current crystal, ceramic or SAW devices due to their compactness and good compatibility with the high frequency Si or GaAs integrated circuit processing. In this research, onchip AlN thin film resonator has been investigated. AlN thin films with 0.5 to 2.5μm thickness and c-axis orientation have been deposited by DC magnetron reactive sputtering method on silicon and sapphire substrates. The nanoindentation and laser interferometer methods are used to characterize the mechanical properties and electromechanical properties of the thin AlN film in the composite resonator structure. Patterning of AlN film and electrode layers has also been studied for the fabrication of onchip thin film bulk acoustic wave resonators.

The excellent tribological properties, very low friction coefficient, ~0.05, of the recently discovered carbide derived carbon (CDC) films have shown them to be excellent candidates in many applications where friction and wear are dominating issues in performance. In this work we examine the feasibility of employing a reactive ion etching process (RIE) with chlorine gas at low temperature, as opposed to the current high temperature chlorination process, in achieving the conversion of metal carbide films into amorphous carbon films. The overall goal is develop a process that is friendlier to microfabricated devices towards employing the tribological properties of CDC films in such devices. We examine this RIE processing using both bulk scale and thin film specimens. These metal-carbide specimens are subjected to a halogen containing ion plasma at reduced pressure in order to leach out the metal, resulting in an amorphous carbon film, a so-called carbide-derived carbon (CDC) process. This reactive ion etching process has been used to produce carbon layers on multiphase carbide materials containing silicon and titanium. The resulting carbon layers have been characterized using a variety of techniques. The results on the bulk scale specimens, via Raman spectrometry, indicated that RIE processing can indeed achieve conversion, while results of the thin films indicated that although conversion occurred poor adhesion of the films to the substrate resulted spallation during friction testing attempts.

This paper describes the fabrication and testing of a microfluidic ink delivery device for Dip Pen Nanolithography (DPN^TM). The purpose of this microfluidic device is to maximize the number of chemical species (inks) for nanofabrication that can be simultaneously patterned by DPN. The device (called 'Centiwells') consists of a two-dimensional array of 96micro-wells micro-machined on a silicon substrate and a thermoelectric module attached to the bottom of the substrate. Microbeads of a hygroscopic material (Poly-Ethylene Glycol) are dispensed into the microwells. By reducing the temperature of the substrate to below the dew point water droplets are condensed on the PEG microbeads, dissolving the beads and creating PEG solutions. Following the formation of the PEG solutions, an AFM tip (pen) is lowered into the micro-wells for loading ink ('dipping' or 'inking' step) and subsequently nanolithography is performed.

In this paper, we report the development of two-dimensional scanning probe arrays to achieve high-throughput DPN writing in a parallel mode. A new "mold-and-transfer" micromachining process has been developed, which is capable of making large scanning probe arrays with high yield and at low cost. Up to date, two-dimensional passive probe arrays with 1000 metal probes and 1000,000 polymer probes have been successfully developed. Prototypes of two-dimensional active probe arrays have also been successfully fabricated and tested, which consists of 49 scanning probe individually controlled by a thermal bimorph micro actuator integrated on each probe. To ensure proper contact status of each probe on the sample surface, a new electrical probe-substrate contact sensing method has also been developed for two-dimensional DPN probe arrays to realize robust DPN writing. As such, 2D DPN writing has been successfully demonstrated for the first time.

The objective of this study is to develop a portable micro-sensor platform for real-time detection of energetic materials (e.g., explosives) over a wide range of vapor pressures. The bending response of an electrically heated microcantilever thermal bi-morph array is used for specific detection of combustible substances using their calorimetric properties. Chemical reactions on the surface induce stress on a micro-cantilever which affects the bending and is measured in real-time using an optical apparatus. The threshold value of actuation current is found to provide a unique signature for identifying equilibrium concentration of iso-propyl alcohol, acetone and gasoline vapors at room temperature. The threshold current is found to scale with the vapor pressure of the volatile species and the ignition temperature. This shows that the sensors can be used for specific detection of different types of combustible materials. The sensor array can be used to detect, identify and monitor volatile combustible species in real time (response time in milliseconds) with the capability for redundancy checks and the ability to eliminate false positive/ false-negative results. The sensor is capable of remote monitoring on a continuous basis for indoor and outdoor applications - which protects the operator of the sensor instrument from explosive effects. The sensor design permits detection at a nominal distance away from the source without coming in contact with the contaminated surface. The sensor capability can be enhanced by specifically coating the micro-cantilever surfaces (e.g. using Dip Pen Nanolithography techniques) and can be integrated into a portable detection platform or instrument.

This paper reports our recent theoretical and numerical studies of new suspended-silicon-nanowire based static sensors. These static sensors detect the presence of molecules according to static deflections induced by the adsorption of molecules. As shown in Fig. 1, the static sensor consists of four suspended silicon nanowires (SiNWs) and one silicon microbeam. Each side of the microbeam includes two SiNWs, instead of one, to avoid the possible torsion of the microbeam and make the microbeam remain parallel to the substrate before detection. The microbeam is used as a platform for the adsorption of molecules. The ultra-high sensitivity of this sensor to mass loading is ensured by the extremely low bending stiffness of the four supporting SiNWs, while the position and deflection of a microbeam are easily found by a routinely used instrument due to the relatively large horizontal dimensions of the microbeam. In this work, theoretical formulation for the sensor deflections under pressure and concentration force is derived and compared with numerical results. Both theoretical and numerical results are subsequently used to optimize the design of the static sensors.

A new configuration of an electroactive polymer, ceramic-based micro hybrid actuation system (μHYBAS) is proposed in this paper. The μHYBAS is a device concept to utilize different electroactive materials in a cooperative and efficient method for optimized electromechanical performance. A theoretical model has been developed, based on the elastic and electromechanical properties of the materials and on the configuration of the device. The μHYBASs investigated use piezoelectric polyvinylidene fluoride (PVDF) as the electroactive polymer (EAP) element combined with the electroactive ceramic (EAC) elements, which are piezoelectric hard lead zirconate titanate (PZT), soft PZT, or Pb(Zn_1/3Nb_2/3)O₃-4.5%PbTiO₃ single crystal (PZN-PT single crystal). The μHYBAS demonstrates significantly enhanced electromechanical performance by utilizing advantages of synergistic contributions of the electromechanical responses of an electroactive polymer and an electroactive ceramic. The modeled results provide guidelines for future developments of high performance μHYBASs to meet various applications.

Microcantilever based sensors have been being widely used for measuring or detecting various physical conditions, chemical agents and biological species. Researchers are continuing to focus on enhancing the sensitivity of these devices toward improving their performance and applicability. In this paper, a numerical study is performed to assess the influence of microcantilever geometry on sensitivity to improve these devices for better detection of hazardous biological agents in liquid environments. Modal analyses were performed on microcantilevers of different geometries and shapes using ANSYS software and compared to the basic rectangular shaped microcantilever structures employed by most researchers. These structures all possessed a 50 μm length, 0.5 μm thickness and 25 μm width where the cantilever is clamped to the substrate, and were analyzed for their basic resonance frequency as well as the frequency shift for the attachment of a 0.285 picogram of mass attached on their surfaces. These numerical results are compared for the improvement of the sensitivity for MEMS based microcantilever sensor, which is particularly promising for biosensor applications. Of the geometries studied a few were found to possess a significant increase in mass sensitivity over regular rectangular shaped cantilever beam structures of similar dimensions. In particular, it was found that geometries possessing larger clamping widths and/or reduced effective mass at the free end yielded enhanced sensitivity. A triangular shape was found to increase mass sensitivity an order of magnitude over standard rectangular shapes.

To develop biosensors with the capability of detecting very small mount of biological agents, such as single or several cells, magnetostrictive bars or stripes in size from nanometer to micrometer are required. In this paper, magnetostrictive nanobars and nanobar arrays, with a diameter from 50 to 200 nm and a length of 2~5 μm, were fabricated based on template-based synthesis. The amorphous Fe-B alloy was selected as the magnetostrictive material to fabricate the nanobars. The study on resonance behavior and magnetic properties of plated Fe-B thin films indicate that amorphous Fe-B alloy is a good candidate for fabricating high performance sensor platform. The magnetization hysteresis loop of Fe-B nanobars was characterized. It is found that all the nanobar arrays exhibit easy axis of magnetization along bar length direction but with smaller coercivity, which is different with bulk materials. The physics behind the phenomena is discussed.