This paper describes the implementation of smart materials in actuators which are employed by mobile microrobots. A versatile microrobot is able to perform complex handling and joining procedures of microobjects with high precision. Such a microrobot requires precise actuators made of specific smart materials. These materials enable the microrobots to fulfill movements in coarse- and fine-positioning mode. The actuator material, currently most frequently used for the coarse-positioning mode, is a piezoelectric ceramic. It is important for the coarse-positioning actuators to be able to carry the entire weight of the microrobots, to provide a velocity of several cm/s and a positioning accuracy in a range of a few μm. The actuators for a fine-positioning unit have to provide an accuracy in the range of a few nanometers. The workspace of a fine-positioning unit depends on a task and is in between a few μm³ and several cm³. For this use, piezoelectric ceramics are suitable as well. Furthermore, the employment of ferrofluids is promising.

Composite materials structures often have weaknesses at the location where the materials join, where different materials are placed in proximity or bonded. These weaknesses, flaws or defects control the ultimate strength of the materials. Coupling agents are used to bond disparate materials into one coherent composite. Usually fibers and sometimes beads are part of the composite design. The goal of this area of research sponsored by N.S.F., Transportation Research Board of National Academy of Science and Natural Process Design, has been to develop composites with unique toughness and strength by self repair which occurs at material interfaces and at damaged areas. This is not by the usual methods of hand repair but release of repair chemicals from within the composite itself. These take the form of hollow structural fibers or beads are embedded in the matrix, or a matrix, which reacts with the environment itself. The chemicals carried in the hollow vessels are released wherever and whenever cracking or other matrix damage occurs. In the case where the matrix repairs itself, this works most effectively if supplied all through the volume. Chemicals can be designed to react and repair more than once. Superior performance over the life of the composite is achieved by the selfrepairing and regenerating nature of the interface between the materials. Research to assess and clarify the impact of the various factors involved in self-repair in a more scientific way has been done by Professor Dry who invented the field and holds the basic patents in the area. Repair efficacy of the various applications by other researchers covers a large data field. Due to a lack of clear understanding of the impact of the various factors as well as lack of proper design of all the factors from the start there is a large need for scientific understanding in this area. This research addressed some of these issues by quantifying, relating and explaining the impact of the various factors on each other. These factors are 1) parameter choices such as delivery vessel, shape/size, coating, chemicals released, release trigger and efficacy, impact on matrix properties 2) influence of end use such as the importance of speed of release in and the importance of damping and stiffening 3) combination with various processing methods’ heat and pressure. The objective of the paper is to explain the science issues involved in creating polymer composites designed to be self-repairing.

The actuation of single-wall carbon nanotube (CNT) mat, electrically conducting polyaniline (PAn) film and a composite of these two materials has been investigated in NaNO3 (1 M), NaCl (1 M, 3 M) and HCl (1 M) solutions. The expansion/contraction patterns of the PAn, CNT and CNT/PAn samples are similar in these solutions. Fabrication of the CNT/PAn samples by coating PAn (CNT:PAn= 3:1 by weight) substantially enhanced the actuation strain (0.2 - 0.5 %) of the CNT/PAn composite from a low actuation strain (0.06%) of the CNT mat. This result indicates that the addition of PAn to CNT can increase the strain while the Young's modulus E of the PAn coated CNT bundles could be maintained near the E value of CNT bundles (~640 GPa). In other words, the PAn component contributes to a high strain value while the CNT component to high Young's modulus. The combination of these two factors would result in high actuation stresses produced by CNT/PAn composite actuators.

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 threestep 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 costeffective solution with a variety of applications in UV coating, phase shifters for telecommunications and global positioning systems, and polymer and BioMEMS devices.

Multiple Fiber Bragg-gratings are embedded in carbon-epoxy laminates as well as in composite wound pressure vessel. Structural properties of such composites are investigated. The measurements include stress-strain relation in laminates and Poisson’s ration in several specimens with varying orientation of the optical fiber Bragg-sensor with respect to the carbon fiber in an epoxy matrix. Additionally, fiber Bragg gratings are bonded on the surface of these laminates and cylinders fabricated out of carbon-epoxy composites and multiple points are monitored and compared for strain measurements at several locations.

The optimal design of fibre composite structures with embedded sensor systems is investigated to address the interaction between the fibre composite structure and sensor design disciplines for Multidisciplinary Design Optimisation (MDO). Optimisation within the composite structure discipline involves changes in the geometry and ply orientations to achieve a design meeting strength and weight constraints. Other design decisions involve choices of materials, material forms and manufacturing processes, and these affect the valid design space for such variables as minimum thicknesses or curvatures, and strength properties. Within the sensor discipline, optimisation involves changes in sensor locations to achieve a design meeting the requirements for sensor functionality (e.g. detecting damage of a particular size), robustness, cost, and structural integrity. Design decisions such as choice of sensor type influence allowable locations for embedment, the degree of strength reduction in the fibre composite structure, compatible methods of component manufacture, and coverage area for each sensor. The nature of the disciplinary design spaces differ significantly leading to varied approaches to optimisation and the requirement to bring together a range of commercial and customised analysis programs and optimisation algorithms into a cohesive MDO environment.

Adaptive structures are advanced structural systems allowing variation of geometrical and structural characteristics to meet mission requirements. The aim of this paper is to develop an advanced method for vibration control of complex modular elastic structures, which are often required to perform a variety of tasks in aerospace applications with limited resources. The paper's focus is on design of the observer-based decentralized controllers for these smart systems, to counteract the external dynamic loads and to reduce the dynamic stresses in the structural members during arbitrary loading. The new approach leads to substantial savings in computational time with respect to the conventional centralized control method. The concept is illustrated via numerical simulations for 2D elastic modular structures. Their response for various excitation cases, including the case of the failed sub-component controllers is considered in detail. For better interpretation of the efficiency of the designed smart systems, results of the simulations are illustrated using a Virtual Reality computer environment, offering advanced visual effects.

The integration of MEMS, IDTs (interdigital transducers) 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 critical aircraft components. The approach integrates acoustic emission, strain gauges, MEMS 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 (ASHM) 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 characterization 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 (Application Specific Integrated Circuit), providing a low power Microsystems. 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.

Smart structures that used the Ni-Ti shape memory alloy in order to develop mounting/dismounting equipment for the radiation protection clothes were produced experimentally. This is merely an instance. 2 kinds of test specimen of the high-temperature closing and high-temperature opening type were fabricated. The analytic solutions on reversible shape change and tightening force or pressing force for these models were deduced. It could be verified that the analysis method in this study was appropriate, because experimental value and analytic value agreed well. Therefore, it was clarified that the real equipment that it is elaborate and that there is the reliability could be made, if present analysis method is used.

In this paper we describe a novel imaging sensor design¹ that uses the thermo-mechanical properties of nickel-titanium (NiTi) shape memory alloys (SMAs) for detecting far infrared radiation (FIR). A thin NiTi SMA cantilever is coated with a FIR absorbing layer on one surface, while the other is coated with a highly reflecting metallic layers such as gold. Upon absorption of FIR, the temperature of the cantilever changes. This causes the tilt angle of the cantilever to change as well. The deflection is very large if the temperature change coincides with the temperature range of the phase transformation of the NiTi SMA. The detection of the mechanical movements in the cantilever is achieved by illuminating the reflective side using a visible laser beam. A Michelson interferometer is used to covert the reflected light into optical modulation. In doing this, very small displacement in the cantilever can be visualized as laser intensity variation. A single element device has been fabricated for this purpose and our initial experimental results have demonstrated the successful detection of FIR. An estimation of angular deflection per unit change of temperature suggests that our approach can offer sensitivity higher than the reported design based on the use of bi-material strips. We envisage that a two-dimensional array of such devices can lead to the possibility of realizing a practical low-cost infrared imaging device operating under room temperature conditions.

Measurement characterisation of error has been performed from synthetic acceleration data. A variety of kinematics computation techniques were investigated and then applied. Data acquisition specifications, including analogue to digital conversion (ADC) resolution (6, 8, 10, 12 and 14 bit) and sampling rate (100, 150, 200, 250, 300, 375, 500 and 600 Hz), have been varied to investigate the effect on the accuracy of kinematics data with respect to short (20m) displacements. The magnitude of the errors in acceleration, velocity and position are reported for the simulated data. Also, error reduction techniques, including over-sampling and oversampling/multiple point averaging/reduced data transmission, were implemented to examine their effectiveness. The results of this investigation show that MEMS accelerometers are subjected to significant amount of errors, and require accurate calibration and characterisation of errors. Error reduction techniques are also necessary to ensure accurate computation of kinematics information.

The coupled interaction between the mechanical deflection of a cantilever beam and an applied electrostatic field is a non-linear problem. A simple and efficient model is desirable in the initial design phase of MEMS structures. A new analytical model is developed which is versatile and applicable to complex cantilever structures. The model is verified and compared to current analytical approaches and Coventorware. The model is used to examine the novel electromechanical properties of double cantilever beams. Double cantilever beams exhibit a minimum pull-in voltage when the overlap distance between the beams is one half the length of the beams. This result has application to tunable micro-cantilever switches, and the geometrical relationship of the cantilever beam to dynamic range of the switching voltage is discussed.

This paper presents design and development of a haptic interfacing system working with magnetorheological fluids. This system consists of three interchangeable parts: a MR actuator, an interfacing circuitry, and a computer program. The MR actuator is optimally analyzed and designed with finite element simulation, by considering the effects of both magnetic field formation and MR effect formation mechanism. The computer screen is portioned in various segments and the controllable software monitors the attributed values of the voltage to the screen. The computer program, via the parallel port-interfacing circuitry, monitors the current through the electromagnet. Simultaneously, a sensor detects the knob position; the corresponding motion can be observed through a cursor on a computer display. An interactive program is written to demonstrate the working of the haptic interface system. It displays a series of colour bands across the screen, each representing an assigned resistive torque value. As the cursor enters these zones, the corresponding feedback signal is sent to the haptic device.

The primary objective of active flow control research is to develop a cost-effective technology that has the potential for revolutionary advances in aerodynamic performance and maneuvering compared to conventional approaches. The development of such systems have many implications for aerospace vehicles including: reducing mechanical complexity and hydraulic failure, reducing noise and weight, lowering energy and fuel consumption, lowering downtime and maintenance, enhancing maneuvering and agility with enhanced aerodynamic performance and safety. Interest in active flow control for aerospace applications has stimulated the recent development of innovative actuator designs that create localized disturbances in a flowfield. A novel class of devices, known as synthetic jet actuator, has been demonstrated to exhibit promising flow control capabilities including separation control and thrust vectoring. The basic components of a synthetic jet actuator are made of cavity and oscillating materials. The synthetic jet actuator developed at NASA LaRC has a small housing in which a cylindrical cavity is enclosed by two metal diaphragms, 50 mm in diameter, placed opposite each other. A circular piezoelectric wafer is attached to the center of the outside face of each metal diaphragm. The pair of piezoelectric metal diaphragms is operated with a 180° phase differential at the same sinusoidal voltage and frequency. With actuation, a synthetic jet issues from a 35.5mm long by 0.5mm wide slot on the top of the device. In this study, a finite element model of synthetic jet actuator developed at NASA LaRC is investigated. The developed finite element model can be utilized to design and determine the performance of synthetic jet actuator. The analysis includes the FE model of circular plate, FE model of piezoelectric actuator/circular plate, piezoelectric (electrical field)/circular plate (structural field)/cavity (flow field) coupled system and experimental validation. The phase-average jet center velocity and amplitude of input voltage of piezoelectric actuator are predicted by this finite element model. The theoretical prediction is validated experimentally in this study.

This paper presents a design of piezoelectric micro-actuator with improved stroke sensitivity and adequate level of lateral resonant frequency for hard disk drive (HDD) application. The improved design employed active piezoelectric elements in push-pull configuration, and two flexural serpentines with inverse-T slits in between them. Instead of adopting conventional design of physical hinge, the two flexural serpentines allow flexural rotations of load beam about an artificial hinge at larger magnification factors. The present design also allows easy adjustment between stroke sensitivity and lateral resonant frequency, which are conflicting with each other, through placement of piezoelectric elements.

A finite-element method is employed to model layered Surface Acoustic Wave (SAW) two port delay lines, with a zinc oxide (ZnO) thin film guiding layer. The structure is based on x-cut, y-propagating LiNbO₃ substrate. Conditions that model the realistic electrical and mechanical boundary values are applied to the structure to analyze the electromechanical properties of the SAW device. Transient analyses are performed and the frequency responses are calculated using the FFT. Simulation results show good agreement with experimental results, indicating that a finite-element method is an appropriate approach for modeling layered SAW devices.

The development of an optical modulator that can be integrated directly with different types of MEMS sensors and multiplexed onto a single optical fibre network will provide an improved functionality over current optical interfacing techniques. Narrow bandwidth modulators are required for linear sensor arrays to allow rapid connection of sensors, such as MEMS inertial sensors, with relative ease and low insertion loss to an optical network. A new MOEMS Fabry-Perot modulator fabricated using bulk micromachining is proposed. The modulator has been developed to reduce the alignment and packaging restrictions, the complexity and weight of a large sensor system. The modulator allows multiple sensors to be connected to the same optical fibre. Analytical and experimental results of the optical characteristics of the modulator are compared to current MEMS modulators and the fabrication constraints of the modulator are described.

Silicon nitride membrane based MEMS technologies are used in numerous optical micro-systems for many practical applications. In recent years significant effort has been invested into miniaturization of present spectrometers leading to development of compact systems based on linear detector arrays. However, further miniaturization requires the application of MEMS technology. MEMS based micro-Fabry-Perot cavity structures with a flexible mirrors operating in the visible and near infrared range have already been demonstrated. Extension of the technology to mid- (MWIR-3μm to 5μm) and long-wave infrared (LWIR - 8μm to 12μm) seems to be a natural development. However, this requires much larger deflection of the movable mirror of the Fabry-Perot cavity: ~1μm for 3μm to 5μm and ~2μm for 8μm to 12μm wavelengths range. Consequently, precise control of the intrinsic stress in the silicon nitride support film is needed. Our experiments show that suitable silicon nitride properties can be obtained by carefully controlling the process parameters during plasma enhanced CVD growth. In addition to the material requirements, the mechanical structure of the flexible mirror is also important. In order to optimize the mirror structure/shape, finite element analysis was undertaken. The results show that for certain silicon nitride support shapes and thicknesses, mirror deflections needed for both the MWIR and LWIR wavelength regions are possible.

In this paper we investigated the focal performances of the refractive cylindrical micro-lenses made of anisotropic material(uniaxial crystal ) with the use of the rigorous diffraction theory and boundary element method (BEM). The expressions of conversion from the H-field into the E-field for the TM-polarization are given. The lateral and axial intensity distributions of the E- ( H-)field for the TM- polarization and E-field of the TE-polarization are calculated. The focusing features of the micro-lenses, including the focal spot size, the focal length, and the diffractive efficiency are appraised. The focusing characteristics of both isotropically and anisotropically refractive cylindrical micro-lenses with different f-numbers have been analyzed and compared. The numerical simulations show that in the case of isotropic dielectricity the E- and H- field distributions for the TE- and TM-polarizations exhibit almost the same focusing behavior for all different f-numbers (f/4, f/2, f/1.5). However, in the case of anisotropic dielectricity, we found that the focal spot size of the E-field for the TM-polarization is quite larger than that of the E-field for the TE- polarization, for instance, the focal spot sizes of the E-field for TM- and TE-polarizations are 2.35μm and 1.98μm in the case of f/2, respectively. It is noted that the positions of the focal plane of the E-field for the TE- and TM-polarizations are shifted remarkably away from each other. The focal length of the E-field of the TE-polarization is shorter than that of the E-field of the TM-polarization. For instance, the positions of the focal plane of the E-field for the TE- and TM-polarizations are 59.35μm and 70.79μm in the case of f/2, respectively. This result can be understood from the simple argument owing to the different refraction index for two polarizations in the uniaxial crystal. These interesting features are reported here for the first time. It is anticipated that this kind of elements may serve as the ideal light switching devices with high speed in the MEMS.

We propose a new kind of closed-boundary axilens (CBA) for achieving the property of the increasing focal depth even when the f-numbers of system <2/3, superior to an open boundary axilens (OBA). As the propagating beam in the CBA is experienced twice modulations by two boundaries ( closed-boundary) of the CBA, consequently, the focal depth of the CBA may be longer than that of the OBA in which the incident wave is modulated only once. In this presentation, we analyze the focusing characteristics of the CBA with the use of the boundary integral method. The numerical simulations show that the CBA can produce long focal depth for the preset focal depth of 3 and 5 μm in the small f / # of 2/3 , 1/2, and 1/3. For a comparison, we also carry out the calculation for the OBA in the same parameters as those of the CBA. We find that the ratio of the relatively extended focal depth for the CBA to that of the conventional micro-lens is 1.57 (or 2.17) for the preset focal depth of 3μm (or 5μm) at f / # set to 1/2. In contrast, this ratio for the OBA is only 0.75 (or 1.04) for the preset depth of 3μm (or 5μm), with fixed f / # of 1/2. The results sufficiently verify that the CBA has good superiority of long focal depth even for the lower f / # <2/3. In contrast, the OBA almost loses the property of long focal depth for the lower f / # <2/3. It is expected that the proposed CBA may be much useful for practical applications in MEMS.

Ion beam implantation using 2.4 MeV H⁺ ions was used to fabricate long period gratings in multimode optical fibres. The Bragg peak from the ion beam was located in the centre of the core of the fiber. The ion beam was implanted through a mask on the fibre with a period of 1.1 mm to produce a periodic a refractive index modulation, of up to 1%, along the axis of the core of the fibre. The mode scrambling, from the established fundamental mode, was monitored in situ as the implantation was done by observation of the light transmitted through the fibre. This paper describes the experimental method used to achieve this and describes the results. Significant mode scrambling was observed to occur when 3 grating periods were written into the fibre.

Oversampled analog-to-digital conversion architectures provide a trade-off between sampling speed for improved amplitude resolution without the need for complex analog circuits. One form of oversampled data conversion techniques is sigma-delta (ΣΔ) modulation, which takes advantage of high sampling rates. In this paper, a performance evaluation on ΣΔ modulators based on measured data of Self Electro-optic Effect Devices are presented and discussed. The data are used in evaluating the performance of the A/D converter using MATLAB simulations.

In this paper a new low power area efficient serial-to-parallel shift register design is presented. The design of the register only contains 4 transistors per stage and uses a capacitive bootstrapping technique to offset the threshold voltage drop of MOSFETs. We shall refer to this logic family as Non-Ratioed Bootstrap Logic (NRBL). The intended target applications are in smart sensor arrays and image sensors for use in the select registers to control the photo diode array.

In wideband surveillance and digital radio systems, there is a need to sweep the centre fequency of the data converter to detect a broadcast i nthe band of interest. Hence there is a need to design data converters with variable centre frequencies. Sigma-Delta modulators with programmable center frequency are chosen for this purpose. In this paper new resonators for a variable centre frequency bandpass Sigma-Delta modulator are presented. The new resonators have a centre frequency that extends from very low frequency up to half the sampling frequency. Simulation results of a fourth order discrete-time bandpass modulator employing the new resonator are presented using MATLAB and SPICE.

In recent years, there has been renewed interest in Threshold Logic (TL), mainly as a result of the development of a number of successful implementations of TL gates in silicon. Threshold Logic enables, in some instances, the design of digital integrated circuits with a significantly reduced transistor count and area. This paper addresses the important problem of designing technologically feasible parallel (m,n) counters for using TL for binary multiplication. A number of counter design techniques are reviewed and some novel parallel counter designs are presented that allow the design of area efficient 32-bit multiplier partial product reduction circuits.

The 77 GHz band has been reserved for intelligent cruise control in luxury cars and some public transport services in America and the United Kingdom. The Rotman lens offers a cheap and compact means to extend the single beam systems generally used, to fully functional beam staring arrangements. Rotman lenses have been built for microwave frequencies with limited success. The flexibility of microstrip transmission lines and the advent of fast accurate simulation packages allow practical Rotman lenses to be designed at mm-wavelengths. This paper discusses the limitations of the conventional design approach and predicts the performance of a new Rotman lens designed at 77 GHz.

A new approach for the Health Monitoring of structural systems is described in this paper. This technique is based on detecting the acoustic emission signals from damage progression in structures using an array of sensory nodes. Two different sensor configurations that could be used for monitoring wide areas on a structure are discussed. An reliable and cost effective health monitoring system can be an enabling technology for the widespread use of newly discovered high performance materials and design concepts in structural applications. Without a reliable health monitoring system, the lack of service experience and the susceptibility of new classes of materials to unexpected and unknown failure modes will likely delay their acceptance into actual structures. The proposed sensory system mimics biological neurons in its architecture and such an architecture can reduces the cost and complexity of the monitoring system. It is potentially scalable to large and complex structures and could be integrated into the structural materials. The paper summarizes recent work related to this sensory system and provides some new results.

The low structural damping of large space structures and the stringent positioning requirements in missions demand effective vibration suppression. The semi-active approach at hand is based on friction damping due to interfacial slip in semi-active joints which can be controlled by varying the normal pressure in the contact area using a piezo-stack actuator. This paper focuses on the modeling, identification and model reduction of a large space structure with semi-active joints. For the purpose of model identification and model reduction, the nonlinear friction forces transmitted in the joints are considered as external forces acting on the linear tress structure. Experimental Modal Analysis results are used to update the FE model of the truss structure and the parameters of the nonlinear friction model are identified from measured responses of an isolated joint. The model of the linear subsystem is reduced by a combination of balanced reduction and matching moments method. The modal truncation is based on controllability and observability gramians. To improve the fidelity locations conventional connections are replaced by adaptive joints, each with a local feedback controller for the adaptation of the normal force. Simulation results of a 10-bay truss structure with semi-active joints show the potential of the present approach.

The study of smart structures with active devices of sensors and actuators for self-monitoring and self-adaption has been of much recent research interest. Active vibration control is a major application focus and there has been tremendous amount of research work on active vibration control of flexible structures using piezoelectric materials. In this paper, the control mechanism for a flexible cantilever plate structure using surface bonded piezoelectric sensors and actuators has been studied through analytical simulations and experiments. The sensor outputs were used to determine the amount of input to the actuators for controlling the response of the structure in a closed loop. The responses under different control mechanisms were analysed by three dimensional finite element model. The effectiveness of different feedback control methods in altering system characteristics and system responses of the structure was investigated. Experimental investigations on active vibration control were also conducted on a cantilever plate with surface bonded piezoelectric sensors and actuators.

Most structural health monitoring analyses to date have focused on the determination of damage in the form of crack growth in metallic materials or delamination or other types of damage growth in composite materials. However, in many applications local instability in the form of buckling can be the precursor to more extensive damage and unstable failure of the structure. If buckling could be detected in the very early stages, there is a possibility of taking preventive measures to stabilize and save the structure. Relatively few investigations have addressed this type of damage initiation in structures. Recently, during the structural health monitoring of wind turbine blades, local buckling was identified as the cause of premature failure. Results from this investigation suggested that stress waves could be used for detecting the early signs of change in the local curvature that precedes buckling type of failure in this structure. These conditions have been replicated in the laboratory and detailed investigation on the ability of low frequency vibrations to detect the buckling displacement has been carried out. The experiment was performed on a composite bar. The results clearly show that low frequency vibrations could be used to detect the onset of buckling in which the local deflection is only of the order of 0.25 inches.

This paper presents our design and experimental results of nickel microcantilevers, which were fabricated using a laser-LIGA process, based on KrF (248 nm) excimer laser micromachining. A chrome-on-quartz mask, containing the desired mask patterns was prepared for this work. The substrate of copper (30 μm thick) clad printed circuit board (PCB) was laminated with Laminar 5038 photopolymer to be laser patterned. Following laser patterning and laser cleaning, all the samples were electroformed with nickel on top of the copper layer. To release the Ni microcantilevers, the excimer laser was employed again to remove the polymer in the localised area to facilitate Cu selective etching. Here, copper acted as the sacrificial layer as well. The Cu selective etching was carried out with ~ 20 % (wt) aqueous solution of ammonium persulfate. Because the Cu selective etching is isotropic, some undercuts happened next to the anchor area. The samples were characterised using optical microscope, confocal laser scanning microscope and SEM, and some of Ni cantilevers were tested electro-thermally. Their performance was analyzed with respect to the simulation results.

Mechanical instability and stiction of surface structures are troublesome problems in the microfabrication of microelectromechanical systems (MEMS). They are particularly critical when separation gaps are in the sub-micrometer scale. Fabrication-related stiction is usually the result of the rinse-and-dry procedure following the sacrificial layer etch in the structure-release process. The operation-related stiction is the result of over-range operation or capillary condensation after packaging resulting from operation in humid environment. We will present a survey and analysis of various release methods used to hedge stiction problems during fabrication, and then draw a useful comparison among various techniques. Likewise, we will examine some ideas put forward to remedy against post fabrication stiction. The underlying physics for stiction is fundamental to our understanding of the various forces coming into play on the structures in the dimensional scale most utilized in MEMS. We will have a brief look at the proposed theory for modeling these phenomena.

The James Webb Space Telescope (JWST), formally Next Generation Space Telescope (NGST), is one of NASA’s challenging projects for advancing the exploration of space. The NGST will be equipped with a Multi-Object-Spectrometer (MOS) that covers the wavelength ranging from 0.6 to 5 micron. To selectively direct light rays from different regions of space into the spectrometer, one approach is to use microshutter arrays serving as the slit mask for the spectrometer. A large format (2Kx1K) individually addressable microshutter array with a lateral pixel size of 100μm x 200μm is being developed and fabricated using MEMS technologies. The microshutter arrays are close-packed silicon nitride membrane cantilevers. A ferromagnetic Co₉₀Fe₁₀ film is deposited on the membranes to magnetically actuate the microshutters. During deposition a Co₉₀Fe₁₀ film is susceptible to develop large tensile stress that can distort the nitride membranes and affect the contrast of the MOS, especially at cryogenic temperatures. In this paper, we discuss how to minimize the film stress. Stress-test cantilevers are micro machined and used in conjunction with Stoney’s formula to determine film stresses. The effects of deposition pressure and power on the Co₉₀Fe₁₀ film, aluminum film and multiple-layer film stress are discussed. It is found that sputter-deposition of Co₉₀Fe₁₀ at low pressure and power results in favor of low tensile stresses in films.

This paper describes a resonant pressure sensor of a new structure which comprises two beams supported by only two rectangular piers. Both beams can be thermally excited into resonant vibration, whose resonant frequencies are differentially modulated by pressure loads, and the value of the applied pressure can then be obtained by measuring the resonant frequency of each beam. With thick silicon rich SiN film of low residual stress as mechanical vibrating beams, the sensor is fabricated from a single crystal silicon wafer, using porous silicon as a sacrificial layer. Computer simulation is carried out on temperature distribution, resonant frequency shift due to thermal stress, design of diaphragm geometry, and sensitivity of pressure measurement. Simulation results show that the novel structure improves the thermal stability and pressure sensitivity.

This paper is dedicated to a global study of large amplitude effects of electrostatically driven microresonators. Special attention is given to the electrostatic soft spring effect. A theoretical description of the amplitude-induced soft spring effect is given to an electrostatically driven parallel-plate type resonator. A coefficient representing the beam mode shape is introduced, for a clamped-clamped beam resonator. Electrostatic soft spring effect is combined with hard spring effect to highlight the possibility of obtaining a design criteria for compensating the two effects. Hysterisis due to nonlinear forces are addressed, and a critical amplitude is given. A numeric simulator based on MATLAB/Simulink is developed to highlight the electrostatic soft spring effect. Three prototypes with different geometries, which represent each a typical case, are fabricated on an SOI wafer. The design criteria has been compared with measurements obtained with prototypes and experimental results showed good agreements with theory and simulations.

In this paper, we have investigated double gate (DG) MOSFET structure, which has main gate (MG) and two side gates (SG). We know that optimum side gate voltage for each side gate length is about 2V in the main gate 50nm. Also, we know that optimum side gate length for each main gate length is 70nm above. DG MOSFET shows a small threshold voltage (V_th) roll-off. From the I-V characteristics, we obtained I_Dsat=510μA/μm at V_MG=V_DS=1.5V and V_SG=3.0V for DG MOSFET with the main gate length of 50nm and the side gate length of 70nm. The subthreshold slope is 86mV/decade, transconductance is 111μA/V and DIBL (Drain Induced Barrier Lowering) is 51.3mV. Then, we have investigated the advantage of this structure for the application to multi-input NAND gate logic. Also, we have presented that TCAD simulator is suitable for device simulation.

In short channel MOSFETs (metal oxide semiconductor field effect transistors), the effective channel length can be substantially shortened, leading to a slope in the saturated I-V characteristic that is analogous to the Early effect for BJT. These SCE(short channel effect) problems have been solved using the LDD(lightly doped drain) structure, but can't be completely solved at nano scale gate. To complete weakness of LDD, we have designed the MOSFET which has the DG(double gate) structure. For comparing LDD with DG MOSFETs, we have used the TCAD simulator. The structures of LDD and DG MOSFETs have been designed and simulated by the DIOS tool and the electrical characteristics simulated by the DESSIS tool in TCAD. The I-V characteristic is not good in LDD but it is very excellent in DG MOSFET of sub-50nm gate.

In this paper, we have presented the simulation results about threshold voltage of nano scale lightly doped drain (LDD) MOSFET with halo doping profile. Device size is scaled down from 100nm to 40nm using generalized scaling. We have investigated the threshold voltage for constant field scaling and constant voltage scaling using the Van Dort Quantum Correction Model (QM) and direct tunneling current for each gate oxide thickness. We know that threshold voltage is decreasing in the constant field scaling and increasing in the constant voltage scaling when gate length is reducing, and direct tunneling current is increasing when gate oxide thickness is reducing. To minimize the roll-off characteristics for threshold voltage of MOSFET with decreasing channel length, we know α value must be nearly 1 in the generalized scaling.

Microactuator is one of the key components for the microelectromechanical systems (MEMS), and it can be categorized as out-of-plane and in-plane according to the motion types. Most of the existing out-of-plane thermal actuators are multi-layer structures. In this paper, a novel electrothermal single-layer out-of-plane actuator is provided and it characteristics and advantages of this device are stated as follows: (1) This actuator is consisted of only a single thin film material, therefore, it can prevent from delaminating after a long-term operation. Besides, owing to its symmetric geometric design, the inner-beams of this structure don’t have any current passed through them and the inner-beams also provide a geometric constraint to allow the two free ends of the structure to bend upwards symmetrically. (2) This device can be operated at a relative low voltage (<5 volt), and deflected upwards about 4 μm in the experiment test. Besides, the fabrication process is very simple and it is MUMPs(Multi-User MEMS Processes)-compatible. Presently, a prototype structure has been successfully fabricated and tested. This structure offers the potential applications in the adaptive optics systems, and Fabry-Perot filters, etc. Besides, it also provides an interface to cooperate with integrated circuits (IC) and various optical elements to construct an embedded-control optical system.

This paper is dedicated to an electronic oscillator designed to control a MEMS (Micro-Electro-Mechanical System) sensor based on a clamped-clamped silicon micro-beam resonator. Due to the high-temperature environment (200°C) and the MEMS specificities, a specific architecture (MRC transimpedance) was implemented in a standard CMOS technology to improve the robustness and to enable the compensation of drifts due to the technologies used for both the sensor and the ASIC. Particular attention is given to the transimpedance first stage of the oscillator. In this paper and after a brief description of the entire oscillator, experimental results are given to demonstrate the capability of the designed ASIC.

Flexible electrode is essential for longitudinal or traverse type of micro-actuator using electrostrictive(ES) polymer. In this paper, two types of flexible electrode using conductive polymer(CP), carbon black composite and polypyrrole(PPy), was developed for a membrane type and unimorph type ES actuator using PU. At first, electrode using carbon black powder mixed with water-dispersed polyurethane was made and its displacement and dynamic characteristics were measured and compared with commercial conductive grease. Water-dispersed PU was produced by modified acetone process, using methylethylketone and acetone as solvent via NCO-terminated prepolymer. PU actuator was manufactured by stacking carbon black electrode(CBE) at both sides of half cured PU film with spin coater. Compared with conductive grease, displacement using carbon black electrode is approximately 60%. It can be thought that CBE has considerably more viscosity and less conductivity than conductive grease. Although PPy can be made from tens of nanometer to tens of micrometer thickness, phase shift occurs between PU film and PPy because of high temperature CVD process. It is estimated that high surface energy and low surface quality disturbs contacts with PU film.

With increasing interest in micro machine and micro mechatronics, high interest is given to micro devices using magnetostrictive alloys with small sizes. The accurate measurement of magnetostritions ranging from several tens ppm to 1000 ppm of small alloy samples is not easy, and the establishment of measurement methods of magnetostriction of small samples is needed. In this study, four different methods were examined to measure magnetostrictions of small metal samples (cubic samples with sizes smaller than 5 mm x 5 mm x 5 mm ) : Optical interference (OI) method, cantilever (CL) method, strain gauge (SG) method and capacitance (CP) method. The OI method was found to have a high sensitivity, however, too sensitive to measure small deformations of a small sample because of mechanical disturbance induced by surrounding mechanical noises. The CL, SG, and CP methods exhibited similar values of magnetostriction with high stability and reproducibility. This paper reports and discusses results of these measurement methods.

The field of bio-engineering with the aim of developing new machines, which utilizes the motion and control of organisms as a model, is attracting attention. This technology is pursued by paying attention to various shapes and movements of organisms and autonomous system of organisms in acting in response to environment surrounding them, and by mechanically elucidating the locomotion mechanism, propulsive mechanism, nerve system and sensation system of these organisms. On the other hand, in the field of hydrodynamics, magnetic fluid that changes its apparent viscosity depending on magnetic field has been developed, and its utilization is under trial in various fields. We paid attention to the peristaltic crawling of earthworm as transport function in place of wheels or ambulation, and have developed a micro robot running inside a tube using magnetic fluid. In this micro robot, a cell corresponding to earthworm's segment is composed of a natural rubber tube sealed with water-based magnetic fluid, and the cells are connected with elastic rods made of natural rubber. The feature of this micro robot is that its structure is simply composed of, and it can be controlled with external wireless force, by providing it with moving magnetism from the outside. This paper presents the analytical result of the peristaltic crawling of an actual earthworm and the evaluation result of transport mechanism of a prototype micro robot moved by external magnetic field.

The use of silicon-based sensors requires the addition of external support electronics to allow for compatibility with external logging and display instruments. The development of a smart sensor technology, where the support electronics are incorporated into the sensor allows for a simpler interface. To achieve this integration techniques are required for the connection of substrate sensors with drive and support circuitry (operational amplifiers and CMOS circuitry), for effective encapsulation into a single packaged device. In this paper a literature review of basic peripheral and internal interconnect techniques is presented. Three techniques for interconnects were experimentally investigated (wraparound, thermomigration and etched micro via’s) using in-house fabrication equipment and the results presented and discussed. An integrated "smart" light sensor was constructed by forming a schotkey diode on n-type silicon. The sensor was integrated with a commercially available LM324 quad operational amplifier die and etched micro via`s were used to connect between the electronics on one side and the silicon sensor on the other side so forming a smart sensor. The light level sensor was calibrated and tested for suitability as a solar intensity monitor.

Frequency-scanned slotted-waveguide and microstrip travelling-wave arrays, for detecting mm-wave (10-110GHz)thermal emissions via acousto-optic Bragg cell processors, are being considered in defence and civilian security-related remote sensing applications. The optical processing of RF signals is significant because it promises affordable RF operating staring multi-beam arrangements. Optical processing circumvents the need to assemble expensive miniaturised RF receiver elements in phased array configurations by allowing RF information to be processed using optical-video and CCD techniques. This paper considers the design and fabrication of microstrip travelling-wave based sensors for Ka (~35 GHz) -band operation.

In order to successfully integrate microdevices into functional systems, it is often important to address issues of real-time performance monitoring and control. The present study addresses some of these problems in the context of a piezoelectric-driven micropump. These devices are important for emerging areas of chemistry and medicine where reliable distribution of small quantities of fluid is required. A simple, low-cost, fibre optic interferometer has been used to measure the dynamic displacement of the micropump actuator surface. Measurements show significant differences in actuator velocity, displacement and settling time between different pumping media. In addition, transient underdamped vibration of the actuator surface was observed during the rapid excursion and recursion phases of the pump movement while pumping air. These non-contact measurements can be used to determine the open loop characteristics of the micropump and provide information for design improvement or failure analysis. However, the technique can also be used to provide continuous measurement for adaptive compensation, so that the pump performance criteria are always satisfied. To this end, an automated interference fringe counting algorithm has been developed, so that the steady-state parameters can be mapped into the closed-loop control elements in real time. The performance of this algorithm will be discussed, together with the implications for optimal control of the micropump and eventual integration of the interferometer and micropump systems.

By photo-sensitizing the surface controlled negative impedance transistor (NEGIT), we can get a novel photo-negative resistance device--- photo-surface controlled negative impedance transistor--- PNEGIT, PNEGIT has a photo-surface controlled negative resistance I-V characteristics. By taking PNEGIT as an Optical input device to form a drive device and a resistor R_L to form a load of the inverter. And taking a LED in series with R_L as an optical output device. Due to the Instability at the state in the negative resistance region. A photo-controlled Bistability can be made. The state in the valley current region will jump suddenly to the state in the positive resistance region or jumps in the opposite direction as the optical input power p_in increases or decreases respectively. It is demonstrated that, there are two states of photo current or optical output power p_out corresponding one State of p_in Value. This optical Bistability has the function of optical switching, optical self-latching, and optical memory. It can be Applicated in the area of optical information processing, optical computing and optical communication in coming days.

In this paper, we propose a new approach to the modeling of specific electronic networks and junctions. This approach is based on some results obtained by Chechkin, Jikov, Lukkassen and Piatniski (C4) in the theory of periodic wire networks and junctions, which are based on singular measures on these structures. Using this approach, we generalize some results obtained by Canon and Lenczner (C2) and Lenczner (L2) concerning electronic circuits models. As application, the model of piezoelectric thin plate, obtained by Hoffmann and Botkin (H1, H4) is used, where the piezoelectric patches are chosen as junction domains.

The implementation of wavelets in differing areas of signal processing has been a popular research area over the last decade. However, utilising this technology in compressing two dimensional signals, such as digital images is relatively new. Wavelet compression has many distinct advantages over earlier compression methods, the most important of which is suitability to error protection as well as the ability to precisely truncate the compressed bitstream to achieve a desired bit rate for transmission. In this paper some of the recently emerging technologies pertaining to wavelet coding of images will be reviewed, particularly with the use of wireless channels. These developments include techniques to filter images that have been degraded through the addition of noise as well as reconstructing parts of images that have been lost as a result of the fading that characterises wireless mobile environments.

This paper describes the research on the development of a visualisation tool to generate 3D solid models of structures produced by micromachining using an excimer laser system. Currently, the development of part programs to achieve a desired microstructure is by a trial and error approach. This simulation tool assists designers and excimer machine programmers to produce microstructures using the excimer laser. Users can develop their microstructures and part programs with the assistance of digital prototypes rather than designing products using expensive laser micromachining equipment. The methods to simulate micromachining using the solid modelling package, SolidWorks, are described, and simulation and actual machined examples are reported. A basic knowledge of the solid modelling package is required to develop the simulations, and complex models take time to prepare, however, the development time can be minimised by working from previous simulations. The models developed can be parameterised so that families of designs can be investigated for little additional effort to optimise the design before committing to laser micromachining.

The purpose of this research project is to improve the capability of the laser micromachinning process, so that any desired 3D surface can be produced by taking the 3D information from a CAD system and automatically generating the NC part programs. In addition, surface quality should be able to be controlled by specifying optimised parameters. This paper presents the algorithms and a software system, which processes 3D geometry in an STL file format from a CAD system and produces the NC part program to mill the surface using the Excimer laser ablation process. Simple structures are used to demonstrate the prototype system's part programming capabilities, and an actual surface is machined.

A variable reluctance hybrid magnet has been developed to apply new type of high torque motors. A permanent magnet, electromagnet and yoke construct the variable reluctance hybrid magnet. From an engineering point of view, it is important to know the magnetic field around a variable reluctance hybrid magnet. Based on the results of magnetic flux density measurement around the hybrid variable reluctance magnet, the high magnetic flux density was found at edges and joints. The high magnetic flux density was also obtained with electrical current of 10 A at optimum setting form. Therefore, we concluded that the strong force of rotor of the hybrid motor was generated by high surface flux density of the hybrid magnet.

Hydrostatic actuation is a novel method of actuation in Micro Electro Mechanical Systems (MEMS) and provides advantages over other actuation techniques in current use. Hydrostatic actuation utilises a contained pressurised medium to straighten a bent hollow beam, similar to the Bourdon tube used to measure pressure in the macro world. Research has commenced at RMIT University to design and fabricate a microgripper prototype to validate this work. To simplify the design of this microgripper a virtual prototype has been initiated. This paper looks at the work carried out and verification of this virtual prototype using mathematical and finite element modelling. Further work to be undertaken will also be discussed.

We do not know of any modern cities free from air pollution. In Tokyo, the levels of nitrogen oxides, photochemical oxidants, and particulate matter often exceed the environmental quality standards. However, the cost and size of the chemical analyzers have limited the number of monitoring stations and, thus, the spatial resolution of the measured pollutant distributions. The authors have been proposing a gas distribution analyzing system (GASDAS). The use of gas sensors enables compact and inexpensive sensing systems, and leads to a significant increase in the density of monitoring sites. Various network technologies can be used to form a sensing network for efficient data collection. As a first step in the development of GASDAS, a measurement system for nitrogen dioxide and ozone has been developed using electrochemical and semiconductor gas sensors. Encouraging results have been obtained from both types of sensors, and the major interference gas to be addressed in future work has turned out to be nitrogen monoxide. A monitoring system for particulate matter has also been developed. A photosensor is used to measure the accumulation of particulate matter on an air filter. The experimental results have shown the potential of this simple method.

Modal analysis based damage detection techniques using only first few modes are not sensitive for damage identification. The sensitivity of the modal parameters to damage is greater at the higher modes of vibration. Yet, actuation of structures at high frequencies is very difficult with the conventional modal testing methods. In this paper, a new technique that uses smart piezoelectric (PZT) material to extract the modal frequencies for higher modes of vibration is presented. A PZT transducer possesses simultaneous actuating and sensing capabilities. The electromechanical (e/m) impedance method exploits this feature of the PZT transducer to measure its drive-point impedance characteristics when bonded to a structure. Damage location is identified using the natural frequency shifts obtained from the structural impedance signatures and the corresponding undamaged state modes shapes. This technique is superior to other methods, which rely only on statistical quantification of changes in the measured structural signatures. The damage locations were successfully identified by this method for a finite element simulated beam model. The natural frequencies obtained experimentally for longitudinal and bending modes were fairly consistent with the analytical predictions. However, the modeling of damage as merely a source of stiffness reduction proves insufficient to accurately estimate its location, experimentally.

The electro-mechanical impedance (EMI) technique, which utilizes "smart" piezoceramic (PZT) patches as collocated actuator-sensors, has recently emerged as a powerful technique for diagnosing incipient damages in structures and machines. This technique utilizes the electro-mechanical admittance of a PZT patch surface bonded to the structure as the diagnostic signature of the structure. The operating frequency is typically maintained in the kHz range for optimum sensitivity in damage detection. However, there are many impediments to the practical application of the technique for NDE of real-life structures, such as aerospace systems, machine parts, and civil-infrastructures like buildings and bridges. The main challenge lies in achieving consistent behavior of the bonded PZT patch over sufficiently long periods, typically of the order of years, under "harsh" environment. This necessitates protecting the PZT patch from environmental effects. This paper reports a dedicated investigation stretched over several months to ascertain the long-term consistency of the electro-mechanical admittance signatures of PZT patches. Possible protection of the patch by means of suitable covering layer as well as the effects of the layer on damage sensitivity of the patch are also investigated. It is found that a suitable cover is necessary to protect the PZT patch, especially against humidity and to ensure long life. It is also found that the patch exhibits a high sensitivity to damage even in the presence of the protection layer. The paper also includes a brief discussion on few recent applications of the EMI technique and possible use of multiplexing to optimize sensor interrogation time.

In this communication we present all-optical AND, NOT XOR and NOR gates with two and three input logic signals using the cross-polarization modulation (XPolM) effect in a semiconductor optical amplifier (SOA). The gates utilize only a SOA and they need neither an inversion stage nor an additional synchronized clock. The XpolM effect is discussed as well as its repercussion on the polarization-state of a probe beam crossing a SOA perturbed by the power of a control beam. Based on this discussion, we present the design criteria allowing the implementation of the all-optical logic gates with two and three input logic signals. Finally the gates are experimentally demonstrated with input logic signals modulated with a 2.5 Gb/s NRZ code with a pseudo-random data sequence of 2²³-1 length.

In the beginning, the electro-mechanical (EM) impedance method for structural health monitoring was recognized as a means of structural in-situ stress monitoring and measurement. Consequently, theoretical analysis based on the EM impedance method as a tool for in-situ stress identification in structural members was presented. A dynamic impedance model derived from the Euler-Bernoulli beam theory was developed to investigate the influence of in-situ stress on the dynamic and electro-mechanical response of a smart beam interrogated by a pair of symmetrically bounded, surface-bonded piezoceramic (PZT) transducers. Numerical simulation was performed for a laboratory sized smart beam subjected to a multitude of axial loads at the ends. It was found that natural frequency shifts takes place in the presence of in-situ stress. Furthermore, these shifts, which are linearly related to the magnitude of applied load, is directly reflected in the point-wise dynamic stiffness response. However, in terms of the electro-mechanical response, which can be measured directly, the shift of peaks of the EM admittance signature is not directly indicative of the natural frequency shifts. This arises as an inverse problem in engineering, which cannot be deciphered using direct approach. Back calculation of the in-situ stress using genetic algorithm (GA) was proposed.