Carbon nanotubes-based actuator has been investigated using in situ Raman spectroscopy in order to understand the actuation mechanism and to determine associated parameters. We built an actuator from a sheet of single-wall carbon nanotubes (SWNT mat) and studied in several alkali metal (Li, Na, and K) and alkaline earth (Ca) halide solutions. Since Raman can detect changes in C-C bond length: the radial breathing mode (RBM) at ∼190 cm-1 varies inversely with the nanotube diameter and the G band at ∼1590 cm-1 varies with the axial bond length, the variation of bonding was monitored with potential. In addition, the intensities of both the modes vary with either emptying/depleting or filling of the bonding and antibonding states due to electrochemical charge injection. We discuss the variation of intensity/frequency providing valuable information on the dynamics of charge transfer on the SWNT mat surface. We found the in-plane microscopic strain (∼ -0.25%) and the charge transfer per carbon atom (fc ∼ -0.005) as an upper bound for the electrolytes used. It is demonstrated that though the present analyses does comply with the proposition made earlier, but the quantitative estimates of the associated parameters are significantly lower if compared with those of reported values for carbon nanotubes. Moreover, the extent of variation (i.e. coupled electro-chemo-mechanical response) does depend upon the type of counter-ion used. The cyclic voltammetry (CV) is also described briefly.

Composition spreads close to the Heusler alloy Ni2MnAl were grown onto 4-inch wafer substrates using molecular beam epitaxy. Compositional variations of up to 10 at.% relative to each constituent enable a direct comparison of the chemical-structural relationship with respect to martensitic transformation and to magnetic ordering as well as an efficient identification of the emerging phase stability regions. In this study, we set the primary focus on the structural aspects of the transformation behavior as observed by X-ray microdiffraction in combination with a specially designed heating stage. Notably, cross-sectional HRTEM imaging of the respective composition areas reveals a laminated two-phase martensitic structure inside the single grains, identified as a sequence of 2M and 14M variants. Stress relief upon transformation as observed by mechanical stress measurements reaches to 400 MPa depending on the composition. Magnetization measurements so far indicate field-induced ordering to occur at low temperatures, here, below 50 K which is assumed to be closely related to a high degree of structural disorder on the Mn-Al sublattice. Single-crystal thin films were realized by means of an epitaxial relationship to MgO (001).

There is a great deal of interest in CaCu3Ti4O12 system for dielectric applications. We have studied Ca1-xSrxCu3Ti4O12 system for different compositions. The material is synthesized by sol-gel chemical solution route and thin films were deposited by spin coating. Thin films were investigated by x-ray diffraction and Raman spectroscopy for structural properties. These results indicate a solid solution for the compositions x = 0.00 to 0.80. The SEM micrographs shows the uniform films at 800° C, but the dielectric response of Ca1-xSrxCu3Ti4O12 (x = 0.00) shows the dielectric constant value below 200.

ABSTRACT (1-x)PbMg1/3Nb2/3O3-xPbTiO3 (PMN-PT) single crystals of different compositions were studied via piezoresponse force microscopy (PFM). Piezoelectric contrast has been observed in 0.9PMN-0.1PT above the temperature of structural transition indicating spatial distribution of polarization and was attributed to the existence of polar clusters. The domain patterns were found to change drastically with increasing Ti content. In particular, the piezoresponse images of 0.8PMN-0.2PT combine both relaxor and ferroelectric features and in 0.65PMN-0.35PT crystals only micron-sized ferroelectric domains were observed. The evolution of the polar structures with increasing temperature and under external electric field was also investigated. The nature of the observed phenomena is discussed based on the current understanding of the relaxor state in ferroelectrics and possible influence of PFM instrumentation

Magnetization processes of Fe-31.2Pd(at.%) and Fe3Pt (S ≈ 0.8) single crystals in martensite state have been examined in order to confirm the propriety of the condition for the rearrangement of variants under magnetic field: τmag>τreq, where τmag is the magnetic shear stress and τreq is the shear stress required for the rearrangement. When the magnetic field is applied along the [001] direction of each specimen, the magnetization curve shows a large hysteresis due to the rearrangement of variants. Its area, i.e., energy dissipation, is nearly the same as that obtained by stress-strain curves, suggesting the path of the rearrangement of variants by magnetic field is essentially the same as that by external stress. From the magnetization curve, the uniaxial magnetocrystalline anisotropy constant Ku is estimated: it is about 350 kJ/m3 for Fe-31.2Pd at 77 K, and is about 500 kJ/m3 for Fe3Pt at 4.2 K. The maximum of τmag, being evaluated from Ku and twinning shear, is about 2.8 MPa for Fe-31.2Pd at 77K and is about 4.3 MPa for Fe3Pt at 4.2K. For Fe-31.2Pd, the value of τreq is obtained by tensile tests at 80 K to be 0.5–2.5MPa, and the above condition is satisfied. The above condition is also confirmed to be adequate by examining the influence of field direction on the magnetic filed-induced strain.

Fe-Pd thin films with approximately 30 at.% Pd have been produced by magnetron sputtering. Various heat treatment conditions were studied in order to obtain the face-centered tetragonal (fct) martensitic phase at room temperature. X-ray diffractometry was used to identify the various phases present at room temperature and the substrate curvature technique was employed to measure film stress as a function of temperature. The shape memory effect was demonstrated in samples containing the fct martensite phase at room temperature.

Ca1-xMgxCu3Ti4O12 material has been synthesized by chemical route for different compositions and thin films have been deposited by spin coating. X-ray diffraction and Raman spectroscopy were used for detailed characterization of this material for both powder and thin films. X-ray diffraction shows single phase film material for different compositions x < 0.80. The initial measurements on dielectric response indicates high dielectric constant > 10, 000 for the composition x = 0.1.

Synthetic jets have been identified and utilized widely in airflow control applications. These jets of air are usually created by the use of compressed air, or an electromechanically driven vibrating platform. All of these approaches produce desired results in airflow-control such as enhanced lift and increased maneuverability. Despite the results however, system weight, size, response time and force limit their use in aircraft applications where space is a premium. The objective of this study is to characterize the relevant properties for the design of a synthetic jet utilizing three types of piezoelectric actuators as mechanical diaphragms. The limiting parameters of the actuators for this application are shape and volumetric space. Thus, the actuators were circular with a diameter of 6.35 cm, and overall device cavity volume no larger than 147.5 cm3 on a 7 cm x 7 cm areal coverage. The actuators tested were pre-stressed curved metallic unimorphs, bimorphs, and radial field diaphragms. These piezoelectric elements were chosen because of their geometry, quasi-isostatic topography and overall free-displacement. Each actuator was affixed about its perimeter in a cavity, and relevant parameters such as clamped displacement, and jet velocity though a pre-determined dimensional slot, were measured.

SMAs are engineering alloys that recover extensive amounts of deformation when subjected to a temperature change. The recovery of deformation is as result of a phase transformation from martensite to austenite. For example, for NiTiNOL, a very popular SMA, this transformation occurs at 60°C. Actuation is a type of shape memory process that utilizes deformation recovery that is used in smart structural systems. These systems are designed to detect and control structural deformations due to external time varying loads encountered during functional operation. In this paper, the actuating properties of NiTiNOL are characterized using an analytical, computational, and experimental solution (ACES) methodology. Analytical models are utilized to calculate the deformation under dynamic loads. Finite element method (FEM) is used for computational investigations. Optoelectronic holography (OEH) is the experimental method utilized to obtain temperature dependent behavior of NiTiNOL. As a result of the phase transformation, NiTiNOL undergoes a stiffness change indicated by a change in the modulus of elasticity from 33 GPa to 75 GPa. Deformations of NiTiNOL samples subjected to static loads at different temperatures were measured indicating recovery of 85% due to the phase transformation. In addition, amplitudes of vibration were measured as a function of excitation frequency and temperature to determine the effects of phase transformation. The results show effectiveness of NiTiNOL in development of smart structural systems

Ionic polymer membrane actuators represent a relatively new and exciting entry into the field of smart materials. Several key limitations of these transducers have prevented them from experiencing widespread use, however. For example, the bandwidth of these devices is limited at very low frequencies by characteristic relaxation and at high frequencies by the low elastic modulus of the polymer. In this paper, an overview of the initial results of work with hybrid ionic / conducting polymer actuators is presented. These hybrid actuators are devices that combine the electromechanical coupling of ionic polymer actuators and conducting polymer actuators into one coupled device. Initial results show that these hybrid devices have the potential to offer marked advantages over traditional ionic polymer membrane transducers, including increased stress and strain generation and higher actuation bandwidth. Details of the preparation of these devices and performance metrics are presented and comparisons to baseline materials are made.

This paper reports on the design and validation of three in-situ measurement techniques for characterisation of photo-rheological and photo-actuation phenomena. Results from these in-situ techniques are presented and used to investigate isomerisation and recovery effects in azobenzene and spiropyran polymer systems with and without flexible spacer groups.

A new in-situ technique for the measurement of photo-viscosity effects in polymer solutions has been developed using a cone and plate rheometer. The new technique permits simultaneous irradiation of the photo-responsive polymer solutions and continuous measurement of its viscosity in a controlled environment. An additional benefit of the technique is the greatly reduced sample volume compared to traditional capillary viscometers.

Techniques for the in-situ measurement of the photo-actuation effect in polymer systems are discussed, including image analysis and interferometric methods. The effects of environmental factors such as temperature are considered and steps taken to minimise them. The resulting measurement techniques provide an accurate means of measuring the effect of irradiation on the photo-actuating polymers in solution and as solids.

A range of polymers with photo-responsive azobenzene and spiropyran groups in the polymer side chains have been synthesised and evaluated using these three techniques. The photoviscosity and photo-actuation effects under irradiation have been measured in a variety of solvents. The effect of incorporating a flexible spacer group in the side chain of the azobenzene polymers is examined and its effect on the photo-rheology mechanism is discussed.

The temperature dependences of the elastic constants of Ni0.50Mn0.284Ga0.216 and Fe3Pd were studied. Measurements were conducted by the ultrasonic continuous wave method. Anomalous behavior of the elastic constants temperature dependence in austenitic NiMnGa was observed, especially an abrupt 15% softening of C11 at the Curie temperature. The latter anomaly was found to be strongly influenced by the presence and orientation of applied magnetic fields. In martensitic NiMnGa, the temperature dependences of the velocities of all eleven elastic wave modes had abrupt changes at 220K, which indicate a structural phase change from the tetragonal to a second phase at lower temperature. The temperature and magnetic field effects in Fe3Pd were also studied by the elastic constants measurements.

A new generation of thin film shape memory alloy (SMA) for MEMS micro-actuator has been developed, in which film structure and chemistry are optimized, for enhanced higher transition temperature, higher strain recovery rate as well as reduced actuation time by improving the heat transfer rates. Thin film TiPdNi was produced using Ion Beam Assisted Deposition (IBAD) technique both by in-situ heat treating during deposition and followed by post processing heat treatment. Films deposited on unheated substrates were found to be highly amorphous with minimal B2 austenite crystallization, while films deposited on heated substrates produced a highly crystallized twinned B19 martensitic structure through the bulk of the film. For films deposited on heated substrates, a 70 nm thick transition layer was found to exist between the bulk film and silicon substrate. Severe delamination and oxidation as a result of post heat treatment on IBAD deposited samples made in-situ heat treatment most suitable for processing thin film SMAs for MEMS applications. The desire to introduce this innovative technology to the field of SMA micro-actuators is based on two primary advantages of IBAD process over existing technology used to apply thin film SMAs. First, the chemical composition and grain size of the applied coating can be precisely controlled over a wide range of values. Second, the SMA can be deposited as thin films ≤ 2 μm thick with smaller grain size, much denser than films applied using sputter deposition technology. The effects of various processing parameters, and post processing heat treatment, on properties of the thin film SMA were studied.

Water soluble polymers with tunable lower critical solution temperature (LCST) are of increasing interest for biological applications such as cell patterning, smart drug release, DNA sequencing etc. The present study addresses control of the polymer temperature response in water by varying chemical composition of the monomer. In order to achieve this a series of polymers were designed and synthesized based on an ethyleneoxide/ethylene monomer (EO/EE). Polymers were synthesized using polycondensation reactions of difunctional m-EO and n-EE oligomers. The cloud point follows linearly the balance of hydrophobic/hydrophilic interaction and can be tailored in the range of 7 – 70°C by varying the m/n composition and polymer type. Polymer grafting onto the silicon surface exhibits similar solubility behaviour. Adhesion energy measurements show that grafted polymers have solubility cloud points at the temperatures that are close to the ones of the bulk polymer solutions.

The classical NDE techniques of periodical maintenance are just now evolving towards the continuous health monitoring of materials and structures. Taking account of the relation of this approach with the bioinspired notion of smart materials, it seems useful to extend this passive concept to a more active one, especially in the case of materials systems as composite materials. Effectively, if sensors and actuators are embedded in a composite structure before curing in order to monitor and improve the processing parameters, they are able, remaining in the structure, to assume the health monitoring and some optimization of the usage in the next stages of the life. Moreover, in slightly damaged systems, it becomes reasonable to use the results collected by the sensors for improvements of safety of materials and structures. Finally in the last stage of the life, when the material is deeply damaged, it is sometimes possible to slow down, and more rarely, to heal the damage.

A magneto-optic spatial light modulator (MOSLM) driven by electric field is presented. Using finite element method simulation, the parameters of the MOSLM are decided including the 1 μm piezoelectric lead zirconate titanate (PZT)-based layer, the 200 nm bottom electrode, and the 8V electrical applied voltage. A flat surface magneto-optical bismuth-substituted iron garnet (Bi:YIG) based film having an array-pixels structure was created by a site-selected epitaxial method on a SGGG-based substrate. In order to avoid high temperature annealing process which may damage the Bi:YIG film, the PZT film was deposited by the aerosol deposition method (ADM) on the Bi:YIG film. By stress field induced by the PZT film to the Bi:YIG film with an external magnetic field, the pixels of the device were successfully switched.

Four Ni-Mn-Ga single crystals exhibiting modulated 10M and 14M martensites were exposed to rotating magnetic fields of 1 and 2 T. Large periodic magnetic-field-induced strains were obtained for crystals that had been subjected to a mechanical stress while the martensite formed on cooling and to deformation in a magnetic field prior to the experiments with rotating field. A reduction of the magnetic-field-induced strain and fracture occurred when the field-induced strain was close to the transformation strain whereas a constant magneto-mechanical response was detected over more than 10 million field cycles when the field-induced strain was small. The cyclic magneto-mechanical response is related to the interaction of groups of twinning dislocations and twin boundaries. If the dislocations move in large groups, they nucleate cracks at twin boundaries. If the dislocations move in small groups, no cracks are formed resulting in a long lifetime.

The initial concept of a piezoelectric transformer (PT) was proposed by C.A. Rosen, K. Fish, and H.C. Rothenberg and is described in the U.S. Patent 2,830,274, applied for in 1954. Fifty years later, this technology has become one of the most promising alternatives for replacing the magnetic transformers in a wide range of applications. Piezoelectric transformers convert electrical energy into electrical energy by using acoustic energy. These devices are typically manufactured using piezoelectric ceramic materials that vibrate in resonance. With appropriate designs it is possible to step-up and step-down the voltage between the input and output of the piezoelectric transformer, without making use of wires or any magnetic materials.

This technology did not reach commercial success until early the 90s. During this period, several companies, mainly in Japan, decided to introduce PTs for applications requiring small size, high step-up voltages, and low electromagnetic interference (EMI) signature. These PTs were developed based on optimizations of the initial Rosen concept, and thus typically referred to as “Rosen-type PTs”. Today's, PTs are used for backlighting LCD displays in notebook computers, PDAs, and other handheld devices. The PT yearly sales estimate was about over 20 millions in 2000 and industry sources report that production of piezoelectric transformers in Japan is growing steadily at a rate of 10% annually. The reliability achieved in LCD applications and the advances in the related technologies (materials, driving circuitry, housing and manufacturing) have currently spurred enormous interest and confidence in expanding this technology to other fields of application. This, consequently, is expanding the business opportunities for PTs.

In the present study, the evolution of micromagnetic structure and microstructure is studied in-situ both as a function of temperature and applied magnetic field, using single crystal Fe-Pd and Ni-Mn-Ga Heusler alloys. Through the development of a novel technique called ‘Magnetic Transition Spectrum’ to study temperature dependent domain dynamics, the relative sequence of micromagnetic reconfiguration with respect to the martensitic transformation has been determined for the first time. Results show that the FSMAs may be viewed as magnetic mosaics, a new perspective, which is also more amenable to modeling the physical properties of these alloys. Finally, the concept of magnetic mosaics has been used to synthesize a novel class of materials with engineered magnetic anisotropies, and is briefly discussed.

CaCu3Ti4O12 (CCT) thin films were deposited on Pt/TiO2/SiO2/Si substrates using pulsed laser deposition technique. During the thin films deposition, the substrate temperature was varied in the range of 700–800 °C with a constant O2 pressure of 200 mTorr. X-ray diffraction showed the polycrystalline nature of the films. The dielectric properties of the films were studied in metal insulator configuration. Films grown at higher substrate temperature exhibited highest value of dielectric permittivity (∼2200). Micro Raman spectroscopy was used to study the vibrational modes of the CCT thin films in comparison with the bulk ceramics.