Microfabrication techniques such as bulk micromachining and surface micromachining currently employed to conceive MEMS are largely derived from the standard IC and microelectronics technology. Even though many MEMS devices with integrated electronics have been achieved by using the traditional micromachining techniques, some limitations have nevertheless to be underlined: 1) these techniques are very expensive and need specific installations as well as a clean room environment, 2) the materials that can be used up to now are restricted to silicon and metals, 3) the manufacture of 3D parts having curved surfaces or an important number of layers is not possible. Moreover, for some biological applications, the materials used for sensors must be compatible with human body and the actuators need to have high strain and displacement which the current silicon based MEMS do not provide.

One of the most widely known effects in nano electronics is the Coulomb-blocked effect which reduces the shot noise in a device. However, the effect of shrinking of the size is not always so beneficial, shot noise can even increase, because of other effects. Moreover, other types of noises and new effects can set strong limits for device performance. From classical knowledge on device noise, an increased 1/f noise and increased effective thermal noise voltage and quantum uncertainty noises are expected which imply performance limitations at the low frequency and high frequency ends, respectively. The results is a reduced long-term stability an increased frequency of false-bit-switching or false alarm events. These considerations can help us to understand why biology is using neural spikes. From the research-and- development side, the original and engineering of conductance noise is often an unsolved problem. For example, in carbon nanotubes, the published experimental results are contradictory and it is not possible to draw a final conclusion about the nature and possible ways of engineering this crucial kind of noise source. It is important to realize that more active noise sources do not always mean limitation of performance. In chemical sensing applications, the measurement of noise can be used to detect chemical agents and their composition with a great selectivity and sensitivity, because the chemical fragments dynamically interact with the current transport in the device. This is the situation when the noise in nano-sensors has a great advantage as compared to the noise in classical devices. The increased specific surface of nanostructures and the large number of possible structural combinations have a great potential for both gas and fluid sensing application s via noise analysis.

Circuit design for a novel scheme for converting a multiple- valued output voltage forma sensor into a binary-coded output for signal processing is described here. Floating gate MOSFETs and floating gate potential diagrams have been used to design a readout integrated circuit in a standard 1.5 micrometers digital CMOS VLSI technology. The physical design is simulated and tested with SPICE using MOSIS BSIM3 MOS model parameters. Initial results on fabricated devices for the conversion of quaternary input into binary output have shown agreement with the corresponding simulated values. The method is simple and compatible with current CMOS processes. The circuit can be integrated with output of a sensor fabricated in MEMS-CMOS technology.

In our previous work, we had reported initial results on electrical behavior of a novel device called Laterally Movable Gate Field Effect Transistor or LMGFET. In this device, the gate of a FET moves parallel to the substrate surface, which causes the drain current to change linearly to gate motion. In this paper, we describe a potential application of this device as a resonant gate structure. A folded beam structure is utilized as a restraining spring in order to make spring more flexible in the direction of motion compared to the other two orthogonal directions. A high aspect ratio structure is utilized to decrease motion in the direction vertical to the substrate. The resonance frequency can be changed with device geometry resulting in an array of devices with different resonance frequencies on a chip. Five different resonant gate structures are designed with resonance frequencies lying in the audio frequency range. The structures are simulated by analytical and numerical methods. Damping effects are considered in the simulations resulting in quality factor Q values in the range of 500 to 1440 under atmospheric conditions for the designed structures.

Current developments in RF systems require high-performance switches for applications including signal routing, impedance matching and adjustable gain amplifiers. The use of micro-switches to replace traditional semiconductor components is increasingly common, because of their advantages in terms of electrical isolation and power loss. This paper reports on a research program relating to the development of a silicon micro-machined RF micro-switch that uses thin-film piezoelectric material for actuation. Piezoelectric actuation has potential advantages over electrostatic actuation in terms of achievable forces and simplicity of structural design. This paper gives an overview of the design and analysis of a prototype switch. The design concept, based on a cantilevered silicon beam or plate, is described. A low order mathematical model, incorporating the mechanical and electrical characteristics of the switch and the interaction between the silicon structure and the piezo-drive is summarized. This allows the basic behavior of the switch to be quantified, and provides a useful tool for design and optimization purposes. The outline design and manufacture/processing of a prototype switch is discussed.

This work reports a new approach to fabricate spiral on-chip inductors with suspended dome-shape metal tracks. The new fabrication techniques are aimed at reduction of substrate losses by fabrication of spiral metal tracks on top of a sacrificial polymeric dome so that the inductor is suspended in the air when the dome is finally removed. In addition, the reduction of fringing capacitance between the spiral metal tracks is expected since the tracks sidewalls are not fully overlap to each other. Dome-shape spiral inductors made of copper were demonstrated. Currently, high-frequency characterizations of these inductors are under way.

Fabrication process and numerical simulations of a distributed MEMS phase shifter fabricated on a high resistivity silicon substrate using microstereolithography technique is presented here. This fabrication technique enables reduction of the early development cost by removing the need for photomasks used for defining the MEMS bridges. The distributed MEMS phase shifter consists of a high- impedance coplanar waveguide transmission line and several MEMS bridges of 4.5 micrometers height. By applying an electrostatic voltage the height of these bridges can be adjusted. This result in a variation in the distributed capacitance of the segment of the transmission line, which manifests in the phase shift at the output terminal. Experimental efforts to improve its performance is presently underway. The fabrication procedure described here shows significant promise for the use of microstereolithography techniques for RF MEMS devices. Furthermore, the present derive is built on silicon substrate, and hence is compatible with conventional IC fabrication processes.

This paper relates to the development of a novel rate sensor for a wide range of potential applications in the automotive field, amongst others. The sensor is based on the dynamic behavior of an active, vibrating silicon structure that uses thin-film piezoelectric material for actuation and sensing functions, and can be manufactured using silicon micro-machining techniques. The use of piezo-electric material for drive and pickoff offers potentially significant advantages over electrostatic/capacitive means in terms of achievable actuation forces and simplicity of structural design. This paper gives an overview of the design and analysis of a prototype sensor. The design concept is described and a low-order mathematical model, incorporating the inertial behavior of the structure and the interaction between the silicon structure and the piezo-drives and pickoffs is presented. This model allows the basic sensitivity of the sensor to be quantified. The design of a prototype sensor is then described. Some preliminary test results are presented, illustrating the feasibility of the concept.

This paper reports a design concept for MEMS gyroscopes that shifts the complexity of the design from control architecture to system dynamics, utilizing the passive disturbance rejection capability of the 4-DOF dynamical system. Specifically, a novel wide-bandwidth micromachined gyroscope design approach based on increasing the degrees-of-freedom of the oscillatory system by the use of two independently oscillating interconnected proof masses is presented along with preliminary experimental demonstration of implementation feasibility. With the concept of using a 4-DOF system, inherent disturbance rejection is achieved due to the wide operation frequency range of the dynamic system, providing reduced sensitivity to structural and thermal parameter fluctuations. Thus, less demanding active control strategies are required for operation under presence of perturbations. The fabricated prototype dual-mass gyroscopes successfully demonstrated a dramatically wide driving frequency range within where the drive direction oscillation amplitude varies insignificantly without any active control, in contrast to the conventional gyroscopes where the mass has to be sustained in constant amplitude oscillation in a very narrow frequency band. Mechanical amplification of driven mass oscillation by the sensing element was also experimentally demonstrated, providing large oscillation amplitudes, which is crucial for sensor performance.

The mammalian cochlea achieves remarkable acoustic transduction characteristics in a compact and robust design. For this reason, its mechanics have been extensively studied, both mathematically and experimentally. Recently, a number of researchers have attempted to mimic the cochlear function of the basilar membrane in micromachined mechanical devices. This paper presents a design for a silicon cochlea which extends previous work by utilizing a micromachined liquid-filled two duct structure similar to the duct structure of the biological cochlea. Design issues related to both mechanical structure and electrical transduction will be discussed, particularly with regard to optimization of transducer performance. A parallel beam array structure is proposed as a model for an orthotropic membrane. Fabrication procedures and results are also presented. Challenging Fabrication issues related to through-wafer etching, adhesive wafer bonding, device release, and fluid injection are emphasized.

It is always desirable to fabricate low-cost, highly sensitive and miniaturized hydrophones for applications in sonar technology. In this project, silicon based integrated hydrophone devices were designed, fabricated and tested. A theoretical model was also developed. A piezoelectric polymer, polyvinylidene difluoride (PVDF), was employed as the sensing material. Acoustic impedance possessed by this piezoelectric material provides a reasonable match to that of water, which makes it very attractive for underwater applications. A MOSFET with extended gate electrode fabricated on a silicon wafer using standard NMOS process technology was designed as the interface circuit. The electrical signal generated by the PVDF film was directly coupled to the gate of the hence improve the device sensitivity, a thick photoresist, SU-8, was used as the interconnecting dielectric layer under the extended gate electrode. With an 11 micrometers thick SU-8 layer, a sensitivity of the hydrophone was improved dramatically. For underwater operation, the hydrophone was encapsulated by a Rho-C rubber. To improve the reliability of the hydrophone, the active device was passivated by a silicon nitride layer, which is a good barrier material to most mobile ions and solvents. The device after passivation also shows a lower noise level. Further improvement is also achieved by using a differential amplifier as the interface circuit in the electronics. The differential amplifier is also less susceptible to noisy environments and thus improves the signal to noise ratio.

Scientists and engineers at the Army Aviation Missile Command's (AMCOM) Research, Development and Engineering Center (RDEC) are cooperatively working with the Defense Advanced Research Projects Agency (DARPA), other Army agencies, and industry to provide technical solutions for the Army's transformation efforts into the 21st Century force. Advanced technologies are being exposed to achieve the performance and cost goals dictated by the emerging missions of the Transformed Army. It is well established that MEMS technology offers the potential solution to cost, size, and weight issues for the soldier, missile, gun, ground vehicles, and aircraft applications. MEMS sensor arrays are currently being investigated to meet system performance requirements and provide more robust mission capability. A Science and Technology Objective, Research and Development Project is underway at AMCOM/RDEC to develop controlled MEMS sensor arrays to provide for full military dynamic performance ranges using miniature sensor system. MEMS-based angular rate sensors are enhanced with vibration feedback form MEMS accelerometers for output signal stabilization in high-vibration environments. Multi-range MEMS-based accelerometers, cooperatively developed by Government and industry, are being multiplexed to provide dynamic range expansion. An array of integrated accelerometers is expected to increase the dynamic range by an order of magnitude. Future projections suggest that MEMS sensor array technology will be applicable to a broad range of military applications, which include environmental sensor suites for structural health monitoring and forward reconnaissance and surveillance; and optical and radio frequency phased arrays for fast beam steering.

Drag reduction for aerial vehicles has a range of positive ramifications: reduced fuel consumption with the associated economic and environmental consequences, larger flight range and endurance and higher achievable flight speeds. This work capitalizes on recent advances in active turbulent drag reduction and active material based actuation to develop an active or 'smart' skin for turbulent drag reduction in realistic flight conditions. The skin operation principle is based on computational evidence that spanwise traveling waves of the right amplitude, wavelength and frequency can result in significant turbulent drag reduction. Such traveling waves can be induced in the smart skin via active-material actuation. The flow control technique pursued is 'micro' in the sense that only micro-scale wave amplitudes (order of 30mm) and energy inputs are sufficient to produce significant benefits. Two actuation principles have been proposed and analyzed. Different skin designs based on these two actuation principles have been discussed. The feasibility of these different actuation possibilities (such as Shape Memory Alloys and Piezoelectric material based actuators) and relative merits of different skin designs are discussed. The realization of a mechanically actuated prototype skin capable of generating a traveling wave, using a rapid prototyping machine, for the purpose of validating the proposed drag reduction technique is also presented.

In order to achieve successful long-term embedding of Micro-Electro-Mechanical Systems (MEMS) sensors, issues pertaining to their reliability and failure modes need to be investigated. Understanding critical failure modes and their influence on the sensor output is key to developing micro-sensors and switches for long-term application without re-calibration or periodic device maintenance. In this effort, a hierarchical and multi-level model is developed for simulating the response of a MEMS device under induced mechanical failure conditions. The example MEMS device, an accelerometer is modeled at the dynamic, electro-mechanical interaction, and device levels. Mechanical dynamics level simulates the deformation and stress response of the mechanical stage to applied loads. Electro-mechanical interaction model is used to simulate the electrostatic-mechanical interaction of an accelerometer predicting the capacitance changes and electrostatic forces due to deformation. Device level emulates the signal analysis and calibration stage, thus enabling the simulation of the electrical output when the device is subjected to mechanical force or acceleration inputs. The modeling of the MEMS device at each level is carried out using the Finite Element Method. Potential failure modes, such as internal delamination of the mass and spring elements and micro-cracking, are then emulated. The effect of each failure mode on the sensor output is studied for an identifiable signature in the sensor output signal. Selected results showing the effects of typical failure modes are shown.

We describe the design, fabrication, and testing of an electrostatic vertical actuator that exhibits a range of motion that covers the entire initial gap between the actuator and substrate and provides controllable digital output motion. This is obtained by spatially tailoring the electrode arrangement and the stiffness characteristics of the microstructure to control the voltage-deflection characteristics. The concept is based on the electrostatic pull down of bimaterial beams, via a series of electrodes attached to the beams by flexures with tailored stiffness characteristics. The range of travel of the actuator is defined by the post-release deformed shape of the bilayer beams, and can be controlled by a post-release heat-treat process combined with a tailored actuator topology (material distribution and geometry, including spatial geometrical patterning of the individual layers of the bilayer beams). Not only does this allow an increase in the range of travel to cover the entire initial gap, but it also permits digital control of the tip of the actuator which can be designed to yield linear displacement - pull in step characteristics. We fabricated these actuators using the MUMPs surface micromachining process, and packaged them in-house. We measured, using an interferometric microscope, full field deformed shapes of the actuator at each pull in step. The measurements compare well with companion simulation results, both qualitatively and quantitatively.

This paper describes a technique for detection of anisoelasticities in rate integrating gyroscopes as part of a self-calibrative control architecture. In contrast to laser trimming typically done in post processing to compensate for structural imperfections, the on-chip control architecture uses feedforward voltage control to tune the non-linear negative spring effects inherent in parallel plate electrodes in order to electrostatically 'trim' the structural non-idealities. As the first steps toward the feedforward control realization, we present three different algorithms that can be implemented on-chip for identification of structural anisoelasticities. The first technique utilizes the results of measured static displacements, requiring precise knowledge of displacements and applied forces. The second technique involves solving for the non-ideal stiffness parameters using Principal Component Analysis and Fourier transforms of the dynamic system response. The last technique embellishes on the second by the addition of an energy compensation control to overcome damping effects in low Q systems. Finally, the implementation of this algorithm in the electrostatic trimming' of structural imperfections is discussed.

Surface Acoustic Wave gyroscope presents itself as a cheap and effective option for several applications ranging from automotive to industrial sector. The possibility of its wireless interrogation without any power source makes it even more attractive. This paper present a brief discussion of the use of Coupling of Modes theory for the optimization of the design of the SAW gyroscope. Further, the Equivalent Circuit Model is employed to model the gyroscope. The results from HP EES of simulation are compared with measurements from the rate table experiments and the performance of the gyroscope is evaluated in the light of the same.

Electroceramic particles with electrodes of solder are prepared y a low cost and high productivity process. The electroceramic particles can be used as single particle devices, and moreover as multi-functional devices by their assembling. PTCR material is one of the electroceramics, having a positive temperature coefficient of resistivity. We prepare the PTCR particles with electrodes of solder as follows. Semiconducting barium titanate (BaTiO₃) particles, a typical PTCR material, and solder particles are charged into a cylindrical vessel, and the vessel is rotated for several hours. The product is semiconducting BaTiO₃ coated by solder particles. The solder particles are flattened out at the surface of the core particle. The solder forms small dot-like islands, and they are isolated each other. Several applications of such kind of composite particles are described. Single particle device is a PTC thermistor, which consists of one composite particle of semiconducting BaTiO₃. Flexible and self-thermostatic sheets can be produced by packing the composite particles between two thin electrodes. Using NTC particles instead of the semiconducting BaTiO₃ single particle devices of NTC thermistor and flexible NTC sheets can be produced. Twin particles device is a combination of a single particle PTC thermistor and a single particle NTC thermistor in series, and will be a V-type thermistor, having both PTC and NTC properties. The V-type thermistor can be obtained also by stacking the layer of PTC composite particles and that of NTC composite particles in series. It can be applied to a protective device.

A novel planarization technique, compressive molding planarization (CMP) is developed for implementation of a multi-layered micro coil device. Applying CMP and other micromachining techniques, a multi-layered micro coil device has been designed and fabricated, and its use in the magnetic micro actuators for hard disk drive applications has been demonstrated, showing that it can produce milli-Newton of magnetic force suitable for driving a micro actuator. The novel CMP technique can be equally applicable in other MEMS devices fabrication to ease the process integration for the complicated structure.

In this paper, synthesis of carbon and ceramic microcoils by microwave chemical vapor deposition method is presented. Carbon microcoils were synthesized over nickel catalyst using acetylene as carbon source by microwave technique. Titanium carbide microcoils were gained by direct titanization to carbon microcoils .A comparison is given between conventional thermal filament CVD and microwave CVD methods. Particular attention is given to the potential applications of carbon and ceramic microcoils for MEMS.

High aspect ratio micro-gaps are important for electrostatically and electromagnetically transforming forces in movable parts of MEMS. In this paper, three methods based on common UV photolithography are presented to achieve micro-gaps in electroplated permalloy alloy structures. The first method uses an electroplated photoresist PEPR coating as a sacrificial layer. The electrodeposition of photoresist can produce a resist coating of consistent thickness over complex shapes. The micro-gap is realized after the photoresist coating between two electroplated metallic components is removed. This method has been used to produce a gap of 5 mm in a 50 mm thick metallic structure. The second method is used electroplated copper as a sacrificial layer. This method has been demonstrated to produce a 3 mm wide gap in a 50 mm thick metallic structure. The last method uses SU-8 molds whose molecular cross-links are intentionally controlled. After electroplating, the SU-8 molds are completely stripped. This method has been used to produce a 15 mm gap in a 50 mm thick metallic structure. For the three methods above, movable parts can be obtained by removing the underneath sacrificial layers. Compared to DRIE and LIGA, the present approaches enable the inexpensive fabrication of micro-gaps in metallic structures for a variety of MEMS devices such as microsensors, microactuators and microswitches.

The patch rectenna array was initially designed for high voltage output in shape control applications. The test results show that more than 200 volts of output was obtained from a 6 X 6 array at a far-field exposure (1.8 meters away) with an x-band input power of 18 watts. The 6 X 6 array patch rectenna was designed to generate theoretical voltages of up to 540 volts, but normal output was range 200 and 300 volts. Test were also performed with a THUNDER actuator attached to the 6 x 6 array. Flexible dipole rectenna arrays built on thin-film based flexible membranes are envisioned as the best option for NASA applications, such as microwave-driven shape controls for aircraft morphing and large ultra lightweight space structures. An array of dipole rectennas was designed for a high voltage output by densely populating it with Schottky barrier diodes to drive piezoelectric or electrostrictive actuators. The dipole rectenna array will eventually be integrated with a PAD logic circuit for power allocation and distribution and microbatteries for storage of excess power. The development of rectenna array-based wireless power drivers for shape control requires the development of new membrane materials with dielectric constants that are suitable for dipole rectenna arrays.

The work in this study develops the framework for placement and actuation of novel mechanically reconfigurable dual-offset contour beam reflector antennas (DCBRA). Towards that end the methodology for the antennas' design is defined. The antenna designed in this study employs piezoelectrically driven ball screw actuators. These actuators are attached to a flexible sub reflector surface and are used to vary radiation pattern. In addition, two separate optimization problems are stated and solved: Actuator position optimization and actuation value optimization. For the former, a method termed as Greatest Error Suppression method is proposed where the position of each actuator is decided one by one after each evaluation of the error between the desired subreflector shape and the actual subreflector shape. For the second problem, a mathematical analysis shows that there exists only one optimal configuration. Two optimization techniques are used for the second problem: the Simulated Annealing algorithm and a simple univariate optimization technique. The univariate technique always generates the same optimal configuration for different initial configurations and it gives the low bound in the evaluation of the error. The Simulated Annealing algorithm is a stochastic technique used to search for global optimum point. Finally, as an example, the results of the proposed optimization techniques are presented for the generation of a subreflector shape for the geographical outline of Brazil.

Electrical power distribution for recently developed smart actuators becomes an important air-vehicle challenge if projected smart actuation benefits are to be met. Among the items under development are variable shape inlets and control surfaces that utilize shape memory alloys (SMA); full span, chord-wise and span-wise contouring trailing control surfaces that use SMA or piezoelectric materials for actuation; and other strain-based actuators for buffet load alleviation, flutter suppression and flow control. At first glance, such technologies afford overall vehicle performance improvement, however, integration system impacts have yet to be determined or quantified. Power systems to support smart structures initiatives are the focus of the current paper. The paper has been organized into five main topics for further discussion: (1) air-vehicle power system architectures - standard and advanced distribution concepts for actuators, (2) smart wing actuator power requirements and results - highlighting wind tunnel power measurements from shape memory alloy and piezoelectric ultrasonic motor actuated control surfaces and different dynamic pressure and angle of attack; (3) vehicle electromagnetic effects (EME) issues, (4) power supply design considerations for smart actuators - featuring the aircraft power and actuator interface, and (5) summary and conclusions.

Smart structural systems require control systems, which are integrated into structures, to be small, light weight and power-efficient. Re-configurable digital signal processing using Field Programmable Gate Arrays (FPGAs) is now preferred over Digital Signal Processors (DSPs) and Application Specific Integrated Circuits (ASICs) for high performance applications. The FPGAs, due to their re-programmable and dynamic nature, are more suitable in developing hardware implementations because several configurations can be tested and experimented easily without any additional hardware cost. Being small, lightweight and power-efficient, FPGAs are one of the best platforms for building controllers for smart structures. Distributed Arithmetic is a widely used technique for hardware efficient implementations of inner product between a fixed and a variable data vectors. The computational requirements of smart structural controller match this type very well. The objective of the research is to design easily configurable, stand-alone smart controller, which could be used for real-time control applications. Self-configurable controllers are implemented and tested on a cantilevered beam.

While the wireless sensor network technology does exist, the usefulness of this technology has not yet been proven. A small scale implementation of the wireless sensor network will pave the way to a larger scale project that can take full advantage of the capabilities of the sensors. Additionally, a small scale implementation can prove that the wireless sensor network does have useful functionality in most environments. This paper will also provide a basis for any other application that will attempt to use this technology in the future. Bluetooth has been found to be the most favorable protocol for short range wireless sensor networks. Bluetooth is a low cost, low power, short range wireless IEEE 802.11 standard that allows varied device to talk to each other. SAW devices prove to be excellent sensors due to their high sensitivity to the physical environment. In this paper, we implement a temperature sensor. In order to enable communication of a wireless sensor network we use the universal specification-Bluetooth.

Radar absorbing material is a very effective means of RCS reduction in the content of stealth technology. In this paper, we present our design of multi-layer microwave absorber with fractal Frequency Selective Surface embedded. Micro-genetic algorithm is employed for the optimization of the design. Two designs are presented in the paper with regard to different frequency spectrum. The experimental result shown here indicates more than 15 dB reduction at X- band in the reflection of a flat surface, by the use of this configuration with lossy dielectrics, which is in good agreement with the simulation result.

Vacuum packaging of micro resonators using TRP aluminum-to- nitride bonding has been demonstrated. Polysilicon micro resonators are fabricated with integrated sealing rings using surface micromachining technology. The top most layer on the sealing ring is silicon nitride. Aluminum sealing rings are patterned on the Pyrex glass cap wafers. The bonding and sealing of device wafer to cap wafer is done by heating the wafers in the RTP chamber at 750 degrees C for 10 seconds in vacuum. The quality factor of a vacuum- packaged micro resonator is measured as 400 +/- 50.

Packaging represents a significant and expensive obstacle in commercializing microsystem technology (MST) devices such as micro-electro-mechanical systems (MEMS), micro-optical-electro-mechanical-systems (MOEMS), microsensors, microactuators and other micromachined devices. This paper describes a novel wafer level protection method for MST devices which facilitates improved manufacturing throughput and automation in package assembly, wafer level testing of devices, and enhanced device performance. The method involves the use of a wafer-sized micro-cap array. This array consists of an assortment of small caps molded onto a material with adjustable shapes and sizes to serve as protective structures against the hostile environments associated with packaging. It may also include modifications which enhance its adhesion to the MST wafer or increase the MST device function. Depending on the application, the micro-molded cap can be designed and modified to facilitate additional functions, such as optical, electrical, mechanical, and chemical functions, which are not easily achieved in the device by traditional means. The fabrication method, materials selection, and the compatibility of the micro cap device to conventional packaging process are discussed in this paper. The results of wafer-level micro cap packaging demonstrations are also presented.

Scanning probe lithography (SPL) is an emerging method of producing sub 50-nm features for semiconductor applications. A new variation of this process known as Dip Pen Nanolithography (DPN) expands the range of SPL capabilities to include depositing organic and biological macromolecules with nanometer precision. Recent work has been underway to implement DPN as parallel process by employing close packed arrays of individually thermally actuated DPN probes (TA-DPN arrays). In these types of devices, it is not necessary to have feedback control of the height of individual tips during operation. This simplifies the control system and probe structure but complicates array design because of the uncontrolled mechanical interaction between the tip and surface. We have found that TA-DPN arrays are subject to several failure modes that make optimization difficult, including surface scratching, excess tip angle, and problems resulting from inadequate actuation. In this paper, these performance issues are outlined and resolved with the creation of a multi-parameter simulator. The simulation predicts array behavior by employing engineering beam theory, Hertz contact mechanics, and capillary adhesion theory. Using the new insights gained from this simulation method, TA-DPN arrays can be quickly optimized based on any desired criteria.

We report on the performance of micromachined unimorph actuators (PMAT) based on the electrostrictive poly(vinylidene fluoride-trifluoroethylene) copolymer. Because of the high electrostrictive strain and high elastic energy density of the active polymer, the PMAT exhibits a very high stroke level with high load capability and high displacement voltage ratio. In addition, the experimental data also demonstrate that the PMAT is capable of operating over a broad frequency range. The PMAT performance was modeled and the agreement between the modeling results and experimental data confirms that the response of the PMAT indeed follows the design parameters.

Our objective was to demonstrate a microminiature magnetoelastic strain gauge that provides both strain and temperature signals without additional sensors. Iron based magnetoelastic materials were embedded within superelastic nickel/titanium (NiTi) tubing. NiTi stress was transferred to the ferrite, causing a permeability change sensed by a tiny coil. The coil/bridge was excited (70 KHz AC), synchronously demodulated, and amplified to produce a voltage output proportional to coil/ferrite impedance. A DC voltage was also applied and separately conditioned to provide an output proportional to coil resistance; this signal was used to provide thermal compensation. Controlled strains were applied and 6 Hz cyclic outputs recorded simultaneously from the magnetoelastic strain gauge and conventional foil strain gauges. The magnetoelastic strain gauge tracked the foil gauge with minimal hysteresis and good linearity over 600 microstrain; repeatability was approximately 1.5 microstrain. The magnetoelastic strain gauge's gauge factor was computed from delta inductance/original inductance under static strain conditions. Temperatures of 25-140 deg C resulted in an uncompensated shift of 15 microstrain/deg C, and compensated shift of 1.0 microstrain/deg C. A sensitive micro-magnetoelastic strain gauge was demonstrated using the same sensor to detect stress and temperature with no moving parts, high gauge factor, and good thermal stability.

We have developed artificial haircell sensors based on an improved plastic deformation magnetic assembly (PDMA) method. The PDMA method is uniquely capable of realizing 3D microstructures in an efficient, IC-compatible manner. We have improved the design of the PDMA structure to significantly increase the yield by eliminating stress concentration. The robustness of the fabricated devices is enhanced using conformal Parylene deposition. The PDMA process uses magnetic force to bend surface micromachiend cantilever beams. If the bending is significant, the beams would enter plastic deformation regime and maintains permanently bent position even after the magnetic field is removed. Previously, the PDMA process is associated with appreciable yield loss during het magnetic assembly. The failure mechanisms is believed to be stress concentration at sharp corners defined by edges of sacrificial layers. In the new design, a structure enhancement feature is added to the surface micromachiend assembly and hence eliminating any sharp features. Haircells sensors are modular sensory units widely found in the biological world. Haircells are responsible for hearing, flow sensing, and for balancing/equilibrium. We are developing artificial haircell sensors using advanced micromachining technology. The artificial haircell sensors have similar physical scale compared with biological ones.

We describe a micro electro-optical DNA array sensor whose main features are that it is rapid, sensitive, highly accurate and capable of detecting more than one analyte. These features are the consequence of electronic control of three key elements of DNA assays, namely: concentration of the target molecules at the analysis sites, hybridization of the DNA targets to capture probes and discrimination of complementary DNA from non-complementary DNA. The assays are monitored using a scanning confocal optical platform for fluorescence detection. A finite-element based computational model for determining electric field distribution at the biochip electrode array and electrophoretic transport of DNA species is built and analyzed. Comparison of theoretical results for electrophoretic DNA accumulation with those obtained from experiments and a simple analytical model is presented.

In recent years the electronics for developing sensor networks have become compact and cheaper. This has led to an interest in creating communities of distributed sensors that can collect and share data over a large area without being physically connected by wires. The Intelligent Systems Center at the University of Missouri-Rolla (UMR) has for several years been using commercial off-the-shelf (COTS) hardware and custom software to develop a system of stationary sensing nodes capable of pre processing their data locally and sharing processed data to produce global details. This distributed sensing and processing array is targeted for use in monitoring a wide variety of infrastructures. It has been laboratory tested for use in civil, automotive, and airframe monitoring. This paper is an overview of the technologies investigated and the level of functionality obtained from each hardware/sensor/target set. The current system consists of a web server, a central cluster and a collection of satellite clusters. The central cluster is a PC104 X 86 based computer with the satellite clusters being 8051 based single board computers. The satellite clusters are of the order 6 inch X 5 inch X 2 inch in size. There is an effort under way to place a short-range radio with a processor and a PZT sensor into a 2 inch X 1.5 inch X.5 inch package. Exercises have been carried out to demonstrate the ability of the central clusters to remotely control the satellite clusters and the web server's ability to control the central cluster. Further work is under way to integrate the entire system into a web server attached to the Internet and to a long distance communication device, currently employed is a cellular modem into the monitoring array. The web server communicates over standard phone lines to the central cluster, which is equipped with a cellular modem. The central cluster communicates with the satellite clusters using short-range wireless equipment. Proxim rangelan, Erickson Bluetooth, and Linx Technologies RF modules have all been tested as short-range wireless communication solutions. We have demonstrated a system that consists of a structure with an array of smart sensors, preprocess and collect data, and post this data on a web server for global inspection and manipulation. This will enable data sharing and collaborative data analysis to extend the knowledge of structural health monitoring.

The integration of MEMS, IDTs and required microelectronics and conformal antennas to realize programmable, robust and low cost passive microsensors suitable for many military structures and systems including aircraft, missiles and munitions is presented in this paper. The technology is currently being applied to the structural health monitoring of accelerometers, gyroscopes and vibration monitoring devices with signal processing electronics to provide real- time indicators of incipient failure of aircraft components with a known history of catastrophic failure due to fracture. Recently a combination of the need for safety in the air and the desire to control costs is encouraging the use of in-flight monitoring of aircraft components and systems using light-weight, wireless and cost effective microsensors and MEMS. An in-situ Aircraft structural health monitoring system, with sensors embedded in the composite structure or surface-mounted on the structure, would permit the timely detection of damage in aircraft. Micromachining offers the potential for fabricating a range of microsensors and MEMS for structural applications including load, vibration and acoustics characteristics and monitoring. Such microsensors are extremely small; they can be embedded into structural materials, can be mass-produced and are therefore potentially cheap. Additionally a range of sensor types can be integrated onto a single chip with built-in electronics and ASIC, providing a low power microsystem. The smart sensors are being developed using the standard microelectronics and micromachining in conjunction with novel Penn State smart electronics or wireless communication systems suitable for condition monitoring of aircraft structures in-flight. A hybrid accelerometer and gyroscope in a single chip suitable for inertial navigation system and other microsensors for health monitoring and condition-based maintenance of structures, drag sensing and control of aircraft, strain and deflection of structures and systems, ice sensing on aircraft, remote temperature and humidity measurement of propellant in munitions, chemical sensing, etc. are discussed.

The hydrogenated nanocrystalline silicon films have been prepared with plasma enhanced chemical vapor deposition method. The microstructure of these films has been studied by high resolution transmission electron microscopy, Raman scattering spectra and x-ray diffraction analysis methods. The films are especially valuable for some devices, for example, quantum dots, luminescence devices, and film pressure sensors etc. The nc-Si:H films show texture structure. The fractal dimension of this microstructure has been calculated with a Fourier filtered image. The microstructure properties of the films are discussed.