The future proliferation of truly high-speed wireless systems will require more functionality from antennas than can be provided by classic designs. One approach to this challenge is to develop reconfigurable antennas. The goal of a reconfigurable radiator - one that can adjust its operating frequency, bandwidth, and/or radiation pattern to accommodate changing requirements - poses significant challenges to both antenna and system designers. This paper highlights some of the recent advances in the area of antenna reconfiguration, at the University of Illinois and elsewhere, as well as discusses some of the barriers that still need to be overcome to arrive at realizable technologies. These barriers include the development of reliable, mass-manufacturable RF MEMS switches, the design of switch bias networks that will not interfere with antenna operation, and the expansion of signal processing and feedback algorithms to fully exploit this new antenna functionality.

The architecture level design of an impedance matching network is presented for the global system for mobile communication radio frequency (GSM RF) power amplifier module used in a typical cellular handset. Designs for the low and high output impedance of the power amplifier and 50 Ω antenna impedance are considered. Impedance matching network design is presented for a typical low output impedance (Z = 2-j*0.4 Ω) of the power amplifier and 50 Ω antenna impedance and is made adaptive for high output impedance (Z = 7+j*2 Ω). It is shown that the network can be made adaptive to varying output requirements of the power amplifier by tuning the network capacitance toward the antenna end. The architecture level design of a 25 Ω antenna impedance is also presented and shown that that the impedance matching network can be made adaptive, which would require the use of MEMS switches. The adaptive impedance matching networks can be implemented in a passive integration technology with post-processing for MEMS components.

A CMOS test chip has been designed and fabricated which can monolithically integrate ultra low-power operational amplifiers with neural microprobes through post-IC processing. Neural microprobes of varying widths (70 μm, 60 μm, 50 μm, and 40 μm) are designed with varying center-to-center spacing (195 μm, 175 μm, 165 μm, 155 μm, 145 μm, and 125 μm) on a test chip for integration. Neural microprobes are first fabricated on a separate Si substrate to develop a fabrication process for post-IC processing for integration. The amplifier is designed in standard 1.5 μm CMOS process for operation at ∓ 0.4 V. Low power performance is realized by combining forward biased source-substrate junction MOSFETs with a novel low-voltage level-shift current mirror. The designed amplifier gives a gain of 7000 (77 dB) and a 3-dB bandwidth of 30 kHz. The amplifier output has a positive offset of only 20 μV and power dissipation of only 40 μW.

This paper presents the design and analysis of a cantilever beam resonator that is driven by a piezoelectric material. In this paper, we shall look at the effects of miniaturizing the resonator. The beam is a bimorph structure with a Lead Zirconate Titanate (PZT) layer and a stainless steel substrate layer. The PZT layer is electroded in segments to form a sensor and actuator pair for feedback to drive the resonator. Key issues are the effects of design choices on the gain required to cause self-oscillation. These choices are placement and sizing of the sensor and actuator. The study is based on an analytical model of the beam. Results show that the gain required for self-oscillation is highly dependent on the actuator and sensor size and location, the mode of vibration and the overall resonator size.

In this paper the design and development of a planar phase shifter on poly-Si/high resistivity silicon is presented. A new bilateral interdigital coplanar waveguide (BI-CPW) configuration has been developed to get higher effective dielectric constant than normal CPW having same dimensions. This design makes use of BaSrTiO₃ thin film effectively. A new process flow has been developed to enable full compatibility with emerging SiGe/Si technology. Another important feature of this design is the inclusion of a poly-Si layer for lowering operation voltage.

We first point out the practical difficulties of universal quantum computing which may prohibit practical applications as universal computers. Then we show how to apply analog microelectronic circuits to realize the architecture, data processing and parallel computing abilities of quantum computing via Hilbert space computing with analog circuits. Such a Hilbert-space-analog (HSA) computer simulates the Hilbert space and its operators and it is able to use and test quantum algorithms developed for the real quantum computers. Such a computer would be free of most of the practical difficulties of realizing and running a real quantum computer. This computer can be made universal. It is remarkable that by using the same numbers of transistors as in today's PCs, such a HSA computer can manipulate ~10⁷ analog numbers corresponding to ~23 qubits, simultaneously, by quantum-parallel processing.

Electroactive polymers (EAP) demonstrate advantages over some traditional electroactive materials such as electro-ceramics and magneostrictive materials for electromechanical device applications due to their high strain, light weight, flexibility, and low cost. Electroactive polymer-based microelectromechanical systems (EAP-MEMS) are increasingly demanded in many aerospace and medical applications. This paper will briefly review recent progress in the developments and applications of EAP- MEMS. In the past few years, several new configurations of micromachined actuators/transducers have been developed using electroactive polymers. The performance of these micromachined EAP-based devices has been evaluated for both fluid and air conditions. The performance of EAP-MEMS has also been theoretically modeled based on material properties and device configurations. In general, the results obtained from modeling agree with the experimental measurements. Critical process issues, including patterned micro-scale electrodes, molded micro/nano electroactive polymer structures, polymer to electrode adhesion and the development of conductive polymers for electrodes will be discussed. The challenges to develop complete polymer MEMS will also be addressed.

Design, simulation, and fabrication of an integrated microaccelerometer, which is one of several applications of a novel device called Laterally Movable Gate FET (LMGFET) are presented. A LIGA-like post-IC fabrication method compatible with monolithic integration of electronic circuits in standard CMOS technology is utilized to fabricate the accelerometers. External acceleration results in motion of LMGFET differential gates, which cause the drain currents in the FETs to change linearly with position and hence motion. Two types of designs are utilized as restraining springs, which are rigidly anchored to the substrate. The gate motion is first simulated by FEM to analyze its mechanical response. The simulation predicts resonance frequencies of the structures to be 6.32 kHz and 4.66 kHz and gate mechanical motion sensitivity values of 6.23 and 11.47 nm/unit acceleration in g. The op-amp is designed, simulated using PSPICE and fabricated using a 1.5 μm standard CMOS process to amplify the sensor output signal. The simulated values for sensitivity of the two accelerometers are 0.23 mV/g and 0.42 mV/g for the folded beam and the serpentine structure, respectively for an amplifier gain of 45.4 (33.14 dB). The LMGFET microaccelerometers show promise for extremely high dynamic linear operating range.

Polymer based MEMS is rapidly gaining momentum due to their potential for conformability and other special characteristics not available with silicon microsystems. The polymer based nano- and micro-devices are flexible, chemically and biologically compatible, available in many varieties, and can be fabricated in truly 3-D shapes. The conceived devices thus are cheap and disposable. However, in order to conceive fully functional microsystems, necessary electronics have to be integrated. A modified organic thin film TFT is used for such integration. Although the existing technology of organic TFTs can not rival the well-established silicon semiconductor technology, especially in terms of speed, they are still useful in displays, disposable devices, and sensors. Although organic TFT and polymeric MEMS have several common features that make them compatible with each other, to the best of our knowledge, no serious attempt has been made thus far for combining these technologies. This paper is aimed at bridging this gap. Examples of potential microsensors and systems, such as accelerometers and gyroscopes derived from polymer with functionalised carbon nanotubes are presented. A sensor-in-shoe demonstration will be performed at the Conference. Many issues and challenges in the design and development of polymer-based sensors with organic electronics are also addressed.

We developed new surface acoustic wave (SAW) sensors to measure the properties of protein solutions applying a particular organic thin film on the delay line of transverse type SAW devices. Each delay line is configured as an oscillator. The delay line for a sensing channel is coated with a gold film on which an antibody layer is immobilized by protein A. The sensing delay line selectively adsorbs antigens when exposed to a protein solution, which results in phase delay changes due to the mass loading effects induced by the adsorbed antigens. The other delay line is uncoated for use as a stable reference. The relative change in the frequency of the two oscillators is monitored to measure the concentration of the antigens. Sensor properties investigated include selectivity, sensitivity, response time and stability in response to the antigen concentration as well as the viscosity and electrical conductivity of the protein solution.

Nanoparticles can be generated by several different gas phase methods, such as gas deposition, laser-assisted chemical vapor deposition, and laser ablation. Some of the most important aspects - such as size-distribution, structure, and chemical composition of the generated nanoparticles (specifically W and WO₃) - are presented and compared. WO₃ nanoparticle films were deposited by an advanced gas deposition technique and were tested for sensor applications. Two different sensor devices were fabricated: Firstly, a thin Au-WO₃ nanoparticle sandwich film was constructed, and conductance fluctuations of the Au film were measured as the sensor was exposed to alcohol vapor. Secondly, conductivity changes of a thick WO₃ nanoparticle film were detected as it was exposed to test gases (H₂S, NO₂, and CO).

A new method for the detection and identification of gas molecules and the analysis of their mixtures is proposed. The new process is based on the analysis of the amplitude density function of surface acoustic wave resonator (SAWR) or MOSFET signal(s). The proposed method has the potential to detect and identify very small numbers of molecules, even a single one. When the number of adsorbed molecules is small, the exact number and type can be determined from first principles of combinatorics.

Epilepsy is a form of brain disorder caused by abnormal discharges of neurons. The most common manifestations of epilepsy are seizures which could affect visual, aural and motor abilities of a person. Absence epilepsy is a form of epilepsy common mostly in children. The most common manifestations of absence epilepsy are staring and transient loss of responsiveness. Also, subtle motor activities may occur. Due to the subtle nature of these symptoms, episodes of absence epilepsy may often go unrecognized for long periods of time or be mistakenly attributed to attention deficit disorder or daydreaming. Spells of absence epilepsy may last about 10 seconds and occur hundreds of times each day. Patients have no recollections of the events occurred during those seizures and will resume normal activity without any postictal symptoms. The EEG during such episodes of Absence epilepsy shows intermittent activity of 3 Hz generalized spike and wave complexes. As EEG is the only way of detecting such symptoms, it is required to monitor the EEG of the patient for a long time, usually the whole day. This requires that the patient be connected to the EEG recorder all the time and thus remain only in the bed. So, effectively the EEG is being monitored only when the patient is stationary. The wireless monitoring system described in this paper aims at eliminating this constraint and enables the physician to monitor the EEG when the patient resumes his normal activities. This approach could even help the doctor identify possible triggers of absence epilepsy.

A layer-by-layer nanoassembly (LbL) allows production of ultrathin films with a precision of 1-2 nm and needed composition across the multilayer. It was used in combination with traditional lithography to develop micropatterns in ordered nanoparticle multilayers. A selective nanoparticle film growth was also demonstrated for microchannel silicon chips. Microfluidic properties of nanoorganized polymer microcapsules were studied with the microchannel device. Nanoorganized microcapsules production: A LbL-assembly of 20-nm thick poly(styrenesulfonate) / poly(allylamine) shell on microtemplates and loading such hollow polyion shells with enzymes allowed fabrication of catalytic "bioreactors," as it was demonstrated for glucose oxidase, hemoglobin, and myoglobin ensembles.

Hypoglycemia-abnormal decrease in blood sugar-is a major obstacle in the management of diabetes and prevention of long-term complications, and it may impose serious effects on the brain, including impairment of memory and other cognitive functions. This paper presents the development of a non-invasive sensor with miniaturized telemetry device in a wrist-watch for monitoring glucose concentration in blood. The sensor concept is based on optical chirality of glucose level in the interstitial fluid. The wrist watch consists of a laser power source of the wavelength compatible with the glucose. A nanofilm with specific chirality is placed at the bottom of the watch. The light then passes through the film and illuminates a small area on the skin. It has been documented that there is certain concentration of sugar level is taken by the intertitial fluid from the blood stream and deposit a portion of it at the dead skin. The wrist-watch when in contact with the outer skin of the human will thus monitor the glucose concentration. A wireless monitoring system in the watch then downloads the data from the watch to a Palm or a laptop computer.

In this paper we present design, fabrication and integration of a micro fluidic cell for use with the electronic tongue. The cell was machined using microstereo lithography on a Hexanediol Diacrylate (HDDA) liquid monomer. The wet cell was designed to confine the liquid under test to the sensing area and insure complete isolation of the interdigital transducers (IDTs). The electronic tongue is a shear horizontal surface acoustic wave (SH-SAW) device. Shear horizontally polarized Love-waves are guided between transmitting and receiving IDTs, over a piezoelectric substrate, which creates an electronic oscillator effect. This device has a dual delay line configuration, which accounts for the measuring of both mechanical and electrical properties of a liquid, simultaneously, with the ability to eliminate environmental factors. The data collected is distinguished using principal components analysis in conjunction with pre-processing parameters. The experiments show that the micro fluidic cell for this electronic tongue does not affect the losses or phase of the device to any extent of concern. Experiments also show that liquids such as Strawberry Hi-C, Teriyaki Sauce, DI Water, Coca Cola, and Pepsi are distinguishable using these methods.

This paper summarizes very recent developments in the MEMS application of a novel material-class, manufactured by new processing methods. This technology has two unique aspects: (1) The materials form a continuum from high temperature polymers to ultrahigh temperature ceramics. We call them polymer-derived-ceramics (PDCs). In addition to being mechanically robust and chemically inert, the PDCs can be functionalized to embody electronic, optical and magnetic properties. (2) PDC-MEMS are processed from liquid precursors by a simple UV photolithographic photo-curing process. Multilayer structures can be made by stereo lithography or by simple bonding of the polymer structures. The PDC-MEMS technology will be demonstrated by two examples: an optical grating made from the transparent polymer version of the PDC, and a microigniter operating at 1300-1500°C made from the ceramic version. A special feature of the Colorado work is the development of a real-time human-machine-interface (HMI) along-side the design and testing of the MEMS devices. For example, a live HMI for the microigniter gives information such as tip temperature, remaining life and damage accumulation. Finally, the PDC-MEMS technology is inexpensive.

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 cleanroom 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. It is thus natural for the researchers to 'look' for alternative methods such as Microstereolithography (MSL) to make 3D sensors and actuators using polymeric based materials. For MSL techniques to be successful as their silicon counterparts, one has to come up with multifunctional polymers with electrical properties comparable to silicon. These multifunctional polymers should not only have a high sensing capability but also a high strain and actuation performance. A novel UV-curable polymer uniformly bonded with functionalized nanotubes was synthesized via a modified three-step in-situ polymerization. Purified multi-walled nanotubes, gained from the microwave chemical vapor deposition method, were functionalized by oxidation. The UV curable polymer was prepared from toluene diisocyanate (TDI), functionalized nanotubes, and 2-hydroxyethyl methacrylate (HEMA). The chemical bonds between -NCO groups of TDI and -OH, -COOH groups of functionalized nanotubes help for conceiving polymeric based MEMS devices. A cost effective fabrication techniques was presented using Micro Stereo Lithography and an example of a micropump was also described. The wireless concept of the device has many applications including implanted medical delivery systems, chemical and biological instruments, fluid delivery in engines, pump coolants and refrigerants for local cooling of electronic components.

Current ultraviolet (UV) curable polymer techniques for MEMS fabrication pose certain challenges due to the electrical and mechanical properties of the polymer. A novel UV-curable polymer uniformly bonded with functionalized nanotubes was synthesized via a modified three-step in-situ polymerization. Purified multi-walled nanotubes, gained from the microwave chemical vapor deposition method, were functionalized by oxidation. X-ray photoelectron spectroscopy (XPS) was used to identify the -OH and -COOH groups attached to nanotube surface. The UV curable polymer was prepared from toluene diisocyanate (TDI), functionalized nanotubes, and 2-hydroxyethyl methacrylate (HEMA). The chemical bonds between -NCO groups of TDI and -OH, -COOH groups of functionalized nanotubes were confirmed by Fourier transform infrared (FTIR) spectra. This new UV-curable polymer is expected to be a cost-effective solution with a variety of applications in UV coating, phase shifters for telecommunications and global positioning systems, and polymer and BioMEMS devices.

Random deposition of conducting nanoparticles on a flat two dimensional (2D) substrate leads to the formation of a conducting path at the percolation threshold. In sufficiently small systems significant finite size effects are expected. However, in the 2D square systems that are usually studied, the random deposition means that the main effect of small system sizes is that stochastic fluctuations become increasingly large. We have performed experiments and simulations on rectangular 2D nanoparticle films with nanoscale overall dimensions. The sample geometry is chosen to limit stochastic fluctuations in the film’s properties. In the experiments bismuth nanoparticles with mean diameters in the range 20-60nm are deposited between contacts with separations down to 300nm. At small contact separations there is a significant shift in the percolation threshold (pc) and the conducting path formed close to pc resembles a nanowire. Percolation theory describes the experimental onset of conduction well: there is good agreement between predicted and measured values of the power law exponent for the correlation length.

Carbon nanotubes (CNTs) are an interesting class of nanostructures which can be thought of as arising from the folding of a layer of graphite (a graphene sheet ) to form a hollow cylinder composed of carbon hexagons. However, practical applications are still limited by the intricate process of synthesis and the inability of present day methods for large scale production of carbon nanotubes. Morevoer high quality nanotubes with functionalization capability with polymers are desired for polymer MEMS, Nanodevices and BioMEMS. In this paper, an innovative CVD approach using microwave energy was developed for large scale production of single wall and multiwall carbon nanotubes (MWNTs). Straight and helical carbon nanotubes were obtained when acetylene decomposed over the cobalt catalyst at 700°C created by microwave field. The scanning electron microscopy (SEM) of microwave driven MWNTs revealed their homogenous nature. The high resolution electron microscopy (HRTEM) showed typical MWNT has 26 layers. The average diameter of the tubes was observed 20-30 nm. Electron microscope observations showed higher yield of nanotubes obtained from microwave CVD than thermal filament CVD method.

This paper investigates the impact of non-intrusive carbon nanotube coatings on the power consumption of piezoceramic sheet actuators. Due to their nano-scale cylindrical structure, carbon nanotubes provide an order of magnitude increase in the exposed surface area compared to the uncoated piezoceramic sheet. This along with their excellent thermal conductivity allows the nanotube coating to act as a heat sink, drawing energy away from the bulk piezoceramic material and dissipating it to the atmosphere. To demonstrate the proof-of-concept multiwalled carbon nanotube thin films were deposited on the surfaces of 10 mil thick, commercially available PZT-5H sheets. The piezoelectric sheets were actuated at several different excitation frequencies and voltage settings, both before and after application of the nano-film coating. Strain, perpendicular to the poling direction, and current measurements made on these samples indicated that while the piezoelectric samples with nano-film coating exhibited strain behavior similar to the baseline uncoated samples, they required upu to 15% less peak power for high frequency actuation.

Coiled carbon nanotubes exhibit excellent mechanical and electrical properties because of the combination of coil morphology and properties of nanotubes. They could have potential novel applications in nano-composite, nano-electronic devices as well as nano-electromechanical system (NEMS). In this work, synthesis of regularly coiled carbon nanotubes is presented. It involves pyrolysis of hydrocarbon gas over metal/support catalyst by conventional thermal filament CCVD and microwave CCVD methods. The growth mechanism and structural and electrical properties of coiled carbon nanotubes are also discussed.

Industrial Micro Electro Mechanical Systems (MEMS) developers are rapidly bringing to demonstration inertial radio frequency, and optical MEMS devices and components. The Army has a requirement for compact, highly reliable, and inexpensive laser beam steering components for missile seekers and unmanned aerial vehicles remote sensing components to provide a fast scanning capability for pointing, acquisition, tracking, and data communication. The coupling of this requirement with recent developments in the micro-optics area, has led scientists and engineers at the Army Aviation and Missile Command (AMCOM) to consider optical MEMS-based phased arrays, which have potential applications in the commercial industry as well as in the military, as a replacement for gimbals. Laser beam steering in commercial applications such as free space communicataion, scanning display, bar-code reading, and gimbaled seekers; require relatively large monolithic micro-mirrors to accomplish the required optical resolution. The Army will benefit from phased arrays composed of relatively small micro-mirrors that can be actuated through large deflection angles with substantially reduced volume times. The AMCOM Aviation and Missile Research, Development, and Engineering Center (AMRDEC) has initiated a research project to develop MEMS-based phased arrays for use in a small volume, inexpensive Laser Detection and Ranging (LADAR) seeker that is particularly attractive because of its ability to provide large field-of-regard and autonomous target acquisition for reconnaissance mission applications. The primary objective of the collaborative project with the Defence Advanced Research Projects Agency (DARPA) is to develop a rugged, MEMS-based phased arrays for incorporation into the 2-D scanner of a LADAR seeker. Design challenges and approach to achieving performance requirements will be discussed.

Manufacturing processes that can create extremely small machines have been developed in recent years. Microelectromechanical systems (MEMS) refer to devices that have characteristic length of less than 1 mm but more than 1 micron, that combine electrical and mechanical components and that are fabricated using integrated circuit batch-processing techniques. Electrostatic, magnetic, pneumatic and thermal actuators, motors, valves, gears and tweezers of less than 100 mm size have been fabricated. These have been used as sensors for pressure, temperature, mass flow, velocity and sound, as actuators for linear and angular motions, and as simple components for complex systems such as micro-heat-engines and micro-heat-pumps. The technology is progressing at a rate that far exceeds that of our understanding of the unconventional physics involved in the operation as well as the manufacturing of those minute devices. The primary objective of this paper is to critically review the status of our understanding of fluid flow phenomena particular to microdevices. Continuum as well as molecular approaches to the problem will be surveyed. A second objective is to discuss a novel pump/turbine suited for MEMS applications.

Tactile perception of complex symbols through tactile stimulation is an exciting application of a phenomenon known as tactile illusion (TI). Sensation of motion on the skin can be produced by a limited number of discrete mechanical actuators applying light pressure over the skin. This phenomenon can thus be used as a neurophysiological testing tool to determine central and peripheral nervous system injury as well as providing an additional human-machine communication channel. This paper describes the development of a 4 x 5 actuator array of individual vibrating pixels for fingertip tactile communication. The array is approximately one square centimeter and utilizes novel micro-clutch MEMS technology. The individual pixels are turned ON and OFF by pairs of microscopic composite thermal actuators, while the main vibration is generated by a vibrating piezo-electric plate. The physiological parameters required for inducing tactile illusion are described. The fabrication sequence for the thermal micro-actuators along with actuation results are also presented.

Large arrays of MEMS with programmable electrodes and electromagnets are used to achieve microscale positioning of particles, whiskers, and fibers in polymer matrix materials. Arrays of MEMS are placed above and beneath thin layers of a random particle-filled liquid polymer. Microscale variations in the electric and magnetic fields are then used to control body forces that move the piezoelectric and piezomagnetic particles. The body forces are due to the gradients in the E and B fields. Such body forces are generally small on a macroscopic scale. However, standard microfabrication methods enable the generation of very high gradients in E and B on the microscale, therefore generating body forces large enough to overcome microscopic sedimentation forces, viscous forces, and the mutual attraction of particles. We discuss the free body diagram of a particle, the design of MEMS arrays using a finite element code (ANSYS) to determine the electric and magnetic fields, and the fabrication of the MEMS arrays. Currently there is no way to affordably arrange the particles in the optimal microscale pattern in composite materials. Ideally, the current method will provide an affordable and versatile method of patterning the microstructure of multi-functional composite materials, sensors, actuators.

A reflective type Fresnel lens using an array of micromirrors is designed and fabricated using the MUMPs® surface micromachining process. The focal length of the lens can be rapidly changed by controlling both the rotation and translation of electrostatically actuated micromirrors. The rotation converges rays and the translation adjusts the optical path length difference of the rays to be integer multiples of the wavelength. The suspension spring, pedestal and electrodes are located under the mirror to maximize the optical efficiency. Relations are provided for the fill-factor and the numerical aperture as functions of the lens diameter, the mirror size, and the tolerances specified by the MUMPs® design rules. The fabricated lens is 1.8mm in diameter, and each micromirror is approximately 100mm x 100mm. The lens fill-factor is 83.7%, the numerical aperture is 0.018 for a wavelength of 632.8nm, and the resolution is approximately 22mm, whereas the resolution of a perfect aberration-free lens is 21.4μm for a NA of 0.018. The focal length ranges from 11.3mm to infinity. The simulated Strehl ratio, which is the ratio of the point spread function maximum intensity to the theoretical diffraction-limited PSF maximum intensity, is 31.2%. A mechanical analysis was performed using the finite element code IDEAS. The combined maximum rotation and translation produces a maximum stress of 301MPa, below the yield strength of polysilicon, 1.21 to 1.65GPa. Potential applications include adaptive microscope lenses for scanning particle imaging velocimetry and a visually aided micro-assembly.

A reciprocating forced convection cooling concept for a high frequency hybrid shape memory alloy (SMA) actuator is introduced. The actuator combines resistive heating and reciprocating forced convection cooling. The main barrier to achieving high frequency actuation is the large cooling time of conventional steady unidirectional forced convection. Previous studies show that a reciprocating flow in a channel can be more effective in removing heat from the channel walls than the steady state unidirectional forced convection. Analysis of heat transfer from a SMA strip in steady unidirectional laminar forced convection and pulsating forced convection is undertaken in this study. A parametric study is conducted, with various values of parameters such as wall thickness to channel height ratio, Reynolds number, Prandtl number, fluid inlet temperature and oscillation frequency and amplitude of oscillation (in case of reciprocating flow), to identify the optimum operating conditions.

This paper describes the development of a micro-machined passive check valve for an SMA-based compact hybrid actuator device (CHAD). The overall diameter of the valve is 12 mm and the thickness is 1 mm. The structure houses an array of 56 micro check valves. Each micro valve has a 250 μm diameter orifice covered by 10 mm thick nickel flap. Stoppers on each micro valves limit the displacement of the flaps during an opening. This design allows the Ni flaps to withstand high-pressure gradient created by the actuator while achieving high flow rate. A finite element analysis is used to characterize the static and dynamic behaviors of the valve flap for the prediction on flow rate. The prediction is found to be in good agreement with the experiment on static flow rate. The test results indicate that the flaps are able to withstand pressure difference of 0.28 MPa while achieving flow rate of 20 cc/sec. The valve also has low cracking pressure and reverse leakage.

Energy harvesting using piezoelectric material is not a new concept, but its generation capability has not been attractive for mass energy generation. For this reason, little research has been done on the topic. Recently, wearable computer concepts, as well as small portable electrical devices, are a few motivations that have ignited the study of piezoelectric energy harvesting again. The theory behind cantilever type piezoelectric elements is well known, but the transverse moving diaphragm elements, which can be used in pressure type energy generation is not yet fully developed. The power generation in a diaphragm depends on several factors. Among them, the thickness of each layer is important. In this paper, two diaphragm structures, unimorph and bi-morph, were used to calculate energy generation with varying thickness ratio using piezoelectric constitutive equation. The results of this analysis are presented with an eye toward guidelines for design of useful energy harvesting structure.

Our goal was to demonstrate a robust strain energy harvesting system for powering an embedded wireless sensor network without batteries. A composite material specimen was laminated with unidirectional aligned piezoelectric fibers (PZT5A, 250 um, overall 13x10x.38 mm). The fibers were embedded within a resin matrix for damage tolerance (Advanced Cerametrics, Lambertville, NJ). A foil strain gauge (Micro-Measurements, Raleigh, NC) was bonded to the piezoelectric fiber and shunt calibrated. The specimen was loaded in three point cyclic bending (75 to 300 με peak) using an electrodynamic actuator operating at 60,120, and 180 Hz. Strain energy was stored by rectifying piezoelectric fiber output into a capacitor bank. When the capacitor voltage reached a preset threshold, charge was transferred to an integrated, embeddable wireless sensor node (StrainLink, MicroStrain, Inc., Williston, VT). Nodes include: 16 bit A/D converter w/programmable gain and filter, 5 single ended or 3 differential sensor inputs, microcontroller w/16 bit address, on-board EEPROM, and 418 MHz FSK RF transmitter. Transmission range was 1/3 mile (LOS, 1/4 wavelength antennas, 12 milliamps at +3 VDC). The RF receiver included EEPROM, XML output, and Ethernet connectivity. Received data from network nodes are parsed according to their individual addresses. The times required to accumulate sufficient charge to accomplish data transmission was evaluated. For peak strains of 150 με, the time to transmit was 30 to 160 seconds (for 180 to 60 Hz tests).

With the advent of new wireless standards, faster microprocessors and smart sensors, it has become possible to construct wireless sensor networks with ample processing and communication capability. Our thrust in this paper is toward implementing a collaborative processing system for wireless sensor networks. A number of research groups have developed algorithms for applications such as target tracking and location, environment monitoring, and health monitoring of structures. What has been missing is a distributed sensor processing system which provides a framework for these algorithms to function. The system described here borrows heavily from the parallel processing sphere especially the Parallel Virtual Machine (PVM) system developed by ORNL. To facilitate distribution of computational resources, a new algorithm has been proposed for efficient distribution with the use of minimum system resources, in other words, determining an optimal set of nodes which can handle the distributed computation. For this purpose, we assign costs to the various parameters of interest in the network such as the node energy level, the communication energy cost/complexity and resource availability. We then arrive at a cost function by assigning suitable weights to these costs and choose only those nodes whose cost function evaluates to above a particular threshold value. Implementation of typical feature extraction algorithms such as the Discrete Fourier Transform (DFT) and the Discrete Wavelet Transform (DWT) are discussed.

This paper presents the development of a Bluetooth enabled wireless tuning fork gyroscope for the biomedical applications, including gait phase detection system, human motion analysis and physical therapy. This gyroscope is capable of measuring rotation rates between -90 and 90 and it can read the rotation information using a computer. Currently, the information from a gyroscope can trigger automobile airbag deployment during rollover, improve the accuracy and reliability of GPS navigation systems and stabilize moving platforms such as automobiles, airplanes, robots, antennas, and industrial equipment. Adding wireless capability to the existing gyroscope could help to expand its applications in many areas particularly in biomedical applications, where a continuous patient monitoring is quite difficult. This wireless system provides information on several aspects of activities of patients for real-time monitoring in hospitals.

Conventional (i.e. passive) radar absorbers are widely used for modifying the radar cross-section (RCS) of current military platforms but such absorbers may not have adequate performance to satisfy future requirements. Active absorbers, however, offer the potential to overcome the so-called Rozanov performance limit and to enable additional 'smart' functionality such as monitoring damage, adaptive control of RCS or target appearance, Identification-Friend-or-Foe (IFF) and Absorb-While-Scan (AWS) This paper outlines the concept and basic properties of a novel type of active radar absorber, the so-called Phase-Switched Screen (PSS). The basic PSS topology is then modified so as to enable it to operate as a smart radar absorber when used together with an external sensor and feedback control loop. The theoretical predictions are confirmed using data measured on transmission-line analogues of the smart PSS structure.

In this paper, we present the fabrication and experimental results of impedance-graded composites containing carbon nanotubes, carbon fibers, microballoons along with Frequency Selective Surface (FSS). Samples with different FSS patterns were used along with these composites and experiments were carried out to find the effect of the FSSs. It is found that both the FSS pattern and its location in the composite are critical for the reflection property of the sample.

Composite materials comprising microparticles of the environmentally stable conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT), a transition metal/metal salt redox couple in a solid polymer electrolyte matrix have been prepared and characterised. These materials show rapid and reversible changes in their DC and microwave impedances when small DC or AC fields are applied across them from the edges. The composites may be switched from a high impedance state to a low impedance state with the imposition of hte fields for more t han one thousand switching operations with little or no deterioration in performace. When the fields are removed, the initial high impedance state is restored. The extent of the change is very dependent on the choice of redox pair and also on the composition of the polymer electrolyte phase. Copper has been shown to give the largest changes in microwave impedance from 750Ω at 0V to 5Ω at 5V. In this paper, we present a series of waveguide results for composites containing 26wt% PEDOT together with a comparison with other conducting polymer composites, the effect of redox couple on the extent of switching and a proposed mechanism for the switching process.

The VIACT^TM is a new MEMS electrostatic actuator technology potentially capable of realising a number of batchfabricated actuator/sensor transducers including those deflecting in the same or opposite directions, bi-directional, 1D and 2D. The technology can be applied to a wide range of microrobotic and micromechanic applications. This paper reports FEA modelling and simulation, using ANSYS software, of the electromechanical parts of a MEMS-based multitasking walking microrobot, capable of locomotion and equipped with a number of microtools. The few mm² microrobot comprises a number of VIACT^TM cascade microactuators forming eight legs for forward/backward locomotion (via CMS) and side turn and tilt, a microscoop, a combination microtool for gripping, digging, sampling, cutting and lifting tasks, an antenna and solar panel deployment mechanisms. The output energy capability of these actuators is approximately 500 and 1700 pJ/mm² at 35 and 65 volt, respectively, giving microrobot's load-carrying capability of 10x and 25x its own weight at 35 and 65 volts, respectively. When integrated with smart electronics and/or power supply, the microrobot can potentially be remotely-controlled or autonomous. With two structural polysilicon layers and one insulating layer, the whole structure can be batch-fabricated using conventional micromachining techniques. Among its applications include micromanipulation, microassembley and chemical and biological microwaste disposal.

There are various types of noise sources such as shot noise, thermal noise and flicker noise in electronic devices, quantum noise in photonic devices and noise due to Brownian motion in the case of MEMS which limit the performance of the systems based on these devices. In communication applications, noise causes degradation in SNR or BER leading to loss or errors in the received signal. In the case of sensor systems, noise poses a problem in terms of the minimum detectable quantity such as pressure or rotation rate or radiation field. In this paper first an overview of noise sources, noise modeling and analysis is given. Simulation results for some specific MOEM devices are presented. A comparative study of the performance of MEMS versus MOEMS for the same or similar application is also highlighted.

If the most important problem restraining polymer usage is damage and the inability to control it, predict, detect it it, then the solution is self repair of the composites. In order to be self -repairing, a healing chemical is stored in hollow fiber or vessels embedded in the polymer matrix. When the composite cracks, the crack progresses cracking the repair fiber, or bead. The healing chemical flows into the crack and the crack faces are rebonded. Also the fiber can be rebonded to the matrix or delaminations repaired with the adhesive. This research focuses on factors affecting repair so that it will be reliable and not as unpredictable as the polymer matrix itself.