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This paper presents experimental results on thermomechanical behavior of Extrinsic Fabry-Perot Interferometric fiber optic strain sensors (EFPI-FOSS). The objective of this study was to determine the accuracy, strength characteristics, and durability properties of both bare (nonembedded) EFPI sensors, and embedded optical fiber sensors in either a neat resin or aerospace grade composite laminate. Experimental results suggest that the embedded EFPI sensors provide reliable strain measurements for values exceeding 10,000 μ∊ under static loading conditions. A major portion of this study focused on evaluating the long term tension–tension fatigue behavior of optical fiber sensors. Test data suggest the EFPI sensors provide reliable data up to 1 million cycles at fatigue strain levels below 3,000 μ∊. For fatigue strain levels above this value, failure of the fiber optic sensor was observed. While the sensor failed it did not influence the strength and fatigue life of the composite coupons. Considering the design strains used in aerospace components, these results provide evidence that the EFPI sensors will survive during the life of typical aerospace structures.

In this paper we have examined compositional shifts in NiTi film sputter-deposited from a heated and a cooled target. Substrates were radially placed at 18° intervals to capture the semicircular sputtering profile. The composition of the film was measured using Rutherford backscattering spectroscopy (RBS). Film thickness values were measured and the atomic flux captured was calculated. Results indicate that the target temperature significantly influences the composition of the sputtered film. It was found that, for cold targets, Ni and Ti sputter at different angles, producing a compositional shift in the film when compared with the target. For hot targets the sputtering angle is influenced to a lesser degree, such that the compositional shift is negligible. Therefore, target temperature appears to represent an approach to alter the stoichiometry of films deposited.

This paper presents numerical and experimental data for dipole-dipole coupled Ni nanodots on a piezoelectric [Pb(Mg1/3Nb2/3)O3]0.68[PbTiO3]0.32 substrate. Simulation results show that the dipole coupling produces artificial ferromagnetic (parallel magnetization alignment in the nanodot arrays) behavior that can be modified to artificial antiferromagnetic behavior with an applied voltage. Experimental results show the trends in Mr and Hc predicted by the model, but discrepancies arise due to geometric defects present in the fabricated samples. Geometric defects are introduced into the Ni nanodot models, thus dramatically improving the correlation between experiments and analysis. This work shows, through numerical simulations, that artificial multiferroic nanostructures can be designed to produce switching from parallel (artificial ferromagnetic) to antiparallel (artificial antiferromagnetic) magnetization ordering by leveraging dipole coupling with voltage induced changes in magnetic anisotropy.

This paper describes the manufacture and testing of polymer matrix Terfenol-D particulate composites fabricated with a [112] preferred crystal orientation. The results demonstrate that crystal orientation permits higher saturation strain than previously obtained in particulate composites. Oriented particle composites were fabricated using needle shaped Terfenol-D particulate made from commercially available [112] textured polycrystals. A magnetic field applied during manufacture oriented the particles along their longest dimension. Three materials of 22, 36, and 49% particulate volume fraction, were produced and tested to obtain the magnetostriction at constant mechanical loads from 0.5 to 16 MPa. Results demonstrate that crystallographically oriented particle composites saturate at 1475 microstrain whereas the previous non-oriented particle composite saturates at 1150 microstrain. The authors attribute the increased magnetostriction to a predominance of particle orientation along the [112] crystal direction. Modulus measurements indicate that the composites can be described using an upper bound 1–3 composite model. Upper bound rule of mixtures models show that the 36% and 49% oriented particle composites exhibit 94% and 90% respectively of the predicted upper bound magnetostriction. Further rule of mixtures models are used to illustrate how applied stress increases the effective anisotropy in composites as a function of particulate volume fraction. The results demonstrate that by preferential orientation of particles, Terfenol-D particulate composite materials may be fabricated with magnetostriction properties close to that of bulk Terfenol-D.

Piezoelectric polycrystalline ceramics consists of a large number of polarized crystallites (domains) oriented along random directions. When subjected to an excessive electro-mechanical load, each domain may undergo polarization switching resulting in a nonlinear macroscopic behavior of the piezoceramic. In this article a finite element code is developed to simulate this nonlinear behavior. The polycrystalline piezoceramic is modeled as an aggregate of finite elements with each domain represented by a finite element. Each element within this model is oriented in a random direction and is allowed to undergo polarization switchings when a criterion is exceeded. All domains are assumed to possess tetragonal structure. The dielectric, strain, and stress-strain macroscopic responses of the material are generated by the model. The analytical results are compared with experimental data and reasonable agreement is achieved.

A novel thin film (micrometer thickness) shape memory alloy (SMA) micro actuator is presented in this paper. The thin film SMA with composition of approximately 50:50 nickel titanium (NiTi) is sputter-deposited onto a silicon wafer in an ultra high vacuum system. Transformation temperatures of the NiTi film are determined by measuring the residual stress as a function of temperature. The transformation temperature is independent of the presence of chromium (Cr) used as an adhesion layer, or being exposed to air before annealing. A mixture of hydrofluoric acid (HF), nitric acid (HNO/sub 3/) and deionized (DI) water is used to etch the film. Different etch masks are evaluated to protect the NiTi film during the etching. Among the masks tested, a thick photoresist (AZ-4620) produces the best result. The NiTi membrane is hot-shaped into a three-dimensional (3-D) dome shape using a stainless-steel jig. Results indicate the membrane exhibits two-way effect. The performance of the SMA micro actuator is characterized with a laser measurement system for deflection versus input power and frequency response.

In this work, the frequency-dependent magnetic properties of sputtered Galfenol/Permalloy (Fe85Ga15/Ni81Fe19 or FeGa/NiFe) magnetic multilayers were examined to tailor their magnetic softness, loss at microwave frequencies, permeability, and magnetoelasticity, leveraging the magnetic softness and low loss of NiFe and the high saturation magnetostriction (λs) and magnetization (MS) of FeGa. The total volume of each material and their ratio were kept constant, and the number of alternating layers was increased (with decreasing individual layer thickness) to assess the role of increasing interfaces in these magnetic heterostructures. A systematic change was observed as the number of bilayers or interfaces increases: a seven-bilayer structure results in an 88% reduction in coercivity and a 55% reduction in ferromagnetic resonance linewidth at the X-band compared to a single phase FeGa film, while maintaining a high relative permeability of 700. The magnetostriction was slightly reduced by the addition of NiFe...

Micromagnetic simulations of magnetoelastic nanostructures traditionally rely on either the Stoner-Wohlfarth model or the Landau?Lifshitz-Gilbert (LLG) model, assuming uniform strain (and/or assuming uniform magnetization). While the uniform strain assumption is reasonable when modeling magnetoelastic thin films, this constant strain approach becomes increasingly inaccurate for smaller in-plane nanoscale structures. This paper presents analytical work intended to significantly improve the simulation of finite structures by fully coupling the LLG model with elastodynamics, i.e., the partial differential equations are intrinsically coupled. The coupled equations developed in this manuscript, along with the Stoner-Wohlfarth model and the LLG (constant strain) model are compared to experimental data on nickel nanostructures. The nickel nanostructures are 100???300???35 nm single domain elements that are fabricated on a Si/SiO2 substrate; these nanostructures are mechanically strained when they experience an applied magnetic field, which is used to generate M vs H curves. Results reveal that this paper?s fully-coupled approach corresponds the best with the experimental data on coercive field changes. This more sophisticated modeling technique is critical for guiding the design process of future nanoscale strain-mediated multiferroic elements, such as those needed in memory systems.

In this work, we present the concept of planar polymer photonic waveguides for the health monitoring of aerospace structures. Here a polymer layer is deposited onto the material/structure to be monitored. Within the polymer layer, waveguides are created after deposition. These waveguides can then be used as 'optical fibres' for optical fibre sensing methodologies. In investigating the use of polymer photonic waveguides the question to be answered is: does the strain in the test material transfer to the polymer layer, such that the value to be measured optically is reliable and indicative of the true strain in the test structure? To answer this question we have conducted a preliminary structural analysis with finite element analysis, utilising ANSYS. A simple aluminium cantilever was used as the test structure, and layers of polyethylene with different thicknesses were added to this. Result show that the thinner the layer of polymer, the more accurate the measured strain will be. For a 100um coating, the difference is strain was observed to be on the order of 3.3%. © 2014 IEEE.

This study reports on signal recovery of optical fiber Bragg gratings embedded in a carbon fiber composite overwrapped pressure vessel's (COPV) structure which have become chirped due to microcracks. COPVs are commonly used for the storage of high pressure liquids and gases. They utilize a thin metal liner to seal in contents, with a composite overwrap to strengthen the vessel with minimal additional mass. A COPV was instrumented with an array of surface mounted and embedded fiber Bragg gratings (FBGs) for structural health monitoring (SHM) via strain sensing of the material. FBGs have been studied as strain sensors for the last couple decades. Many of the embedded FBGs reflected a multi-peak, chirped response which was not able to be interpreted well by the current monitoring algorithm. Literature and this study found that the chirping correlated with microcracks. As loading increases, so does the number of chirped FBGs and microcracks. This study uses optical frequency domain reflectometry (OFDR) to demultiplex the array of FBGs, and then sub- divide individual FBGs. When a FBG is sub-divided using OFDR, the gratings' strain along its length is recovered. The sub-divided chirped FBGs have strain gradients along their length from microcracks. Applying this to all chirped gratings, nearly the entirety of the embedded sensors' readings can be recovered into a series of single peak responses, which show very large local strains throughout the structure. This study reports on this success in recovering embedded FBGs signal, and the strain gradient from microcracks.

The authors recently reported on a hybrid rotary-translational vibration energy harvesting approach using a spherical permanent-magnet and employing cycloidal motion as a mechanical amplifier. The rotary-translational harvesting approach, which is resonant in nature, can yield approximately twice the e.m.f. compared with a similar translationalonly device. This paper explores the analytic and numerical modelling of the rotary-translational harvester with the goal of finding an efficient method for design optimisation.

The effect of prestress on the nonlinear dielectric (polarization) and piezoelectric (strain) response of lead zirconate–lead titanate (PZT–5H) piezoelectric ceramic is studied. The response to bipolar (−2/+2 MV/m) and unipolar (0/+2 MV/m, −0.4/+2 MV/m) electric field under constant prestress (up to 175 MPa) is experimentally evaluated. In the bipolar regime, prestress mainly influences the first non-180° process. In the unipolar regime, the dielectric and piezoelectric response achieve maximum values near 50–60 MPa because the prestress increases the number of available non-180° domains. A detailed description of the effect of the prestress on electro–mechanical response is provided in terms of non-180° domain wall motion. Based on rule of mixtures formulation, an analytical model is developed to estimate the optimum prestress value for the unipolar electric loading condition. It is found that the dielectric and piezoelectric response of the material is proportional to the volume fraction of the non-180°...

Manufacturing issues related to a thin film NiTi shape memory alloy (SMA) microactuator (i.e. microwrapper) have been investigated using both wet and dry etching techniques. Results show that wet etching the amorphous film produces a cleaner pattern than the crystallized film. Transformation temperatures are not affected by the pre-exposure of the NiTi film to air before crystallization. However, this process produces breakage in the NiTi film at sacrificial layer steps. This is believed to be due to residual stresses developed between the film and substrate during sputtering. The film breakage is overcome by dry etching the film with an ion-milling technique. Curvature in the microwrapper arms is induced using either a bi-layer material (i.e. polyimide and NiTi) or a functionally gradated NiTi film. Results show that when heated the microwrapper arms flatten due to shape memory effect and curl up to form a cage-like structure when cooled.

We present experimental results for [1–3] magnetostrictive composites containing a 20% volume-fraction of Terfenol-D coarse particles (≫1 μm) suspended in a nonmetallic binder. Results from magnetostrictive strain and magnetoelastic measurements are provided for particle distributions that differ in particle size and range of size distribution. Particle size and packing density are shown to effect strain response and are attributed to demagnetization and loading (prestress) effects. Both a decreasing and increasing ΔE effect are measured for low and high fields, respectively, and found to be independent of particle distribution. The response of an optimized bimodal distribution increases packing density and produces 15% larger magnetostrictive strains than the other widely dispersed (polydispersed) (

This paper analytically evaluates the strength of microcomponents fabricated using both wet and dry etching techniques. A finite element model (nanometer meshed) coupled with a macroscopically accepted energy criterion is used to predict the strength of four different microridge structures (geometries). Agreement between analytical predictions and experimental data on single crystal silicon is excellent and validates the use of macroscopic models to predict the strength of micromachined components fabricated with a wide range of processes. The model is used to evaluate design parameters such as the influence of height and ridge material on strength properties. The analytical portion of the study suggests that optimum ridge height exists to maximize the strength and by choosing tougher materials, the strength of the ridges may be improved by an order of magnitude. However, the significant strength improvement is not validated experimentally. The simulation results confirm that the geometries rather than etching flaws are critical issues when dealing with strength of micromachined components. Furthermore, standard macroscopic methods can be used to predict the strength of MEMS components at the micron size level.

Vibration reduction using blade root pitch control introduces a significant power penalty and may adversely affect the airworthiness of the flight control system. Comparable levels of vibration reduction can be achieved using considerably less power through an actively controlled trailing edge flap mounted on the blade. Such a device would have no effect on helicopter airworthiness since it is controlled by a loop separate from the primary flight control system which utilizes the swashplate. Control flap actuation using the magnetostrictive material Terfenol-D is studied in this paper by designing a minimum weight actuator, subject to a set of actuation and stress constraints. An important ingredient in this design process is the precise characterization of the constitutive relations for the magnetostrictive material which provides valuable guidelines on the practical implementation of magnetostrictive actuators. It is shown that the magnetostrictively actuated flap is capable of producing vibration reduction in high speed forward flight in excess of 90%.

The design, fabrication, and testing of a compact displacement accumulation device is presented in this paper. The piezoelectric device provides both large displacement (mm) and large force (100 N). The device is based on conventional inchworm motor design that produces large displacement. The device integrates piezoelectric stacks for large force output and high-speed operation with MEMS ridges as a new clamping system. The device should be able to push and pull 450 N at 11 mm/s in a relatively compact size. FEM analysis is used for the design, EDM is used for the fabrication of a prototype, and conventional test techniques are used to evaluate performance. Stress and modal analysis are used to confirm that the device has an infinite fatigue life and a first modal frequency at 1309 Hz. Experimental data for clamping strength of the ridges and blocking force of the device validate that the device transfers the required load of 450 N. The device is successfully tested over a wide range of operating conditions at speeds up to 11 mm/s using open loop control. The stall load of the device is measured to be exceeding 2250 N. For the dynamic loading test, the device pushes test weights up to 50 N with the open loop control approach.

Piezoelectric materials exhibit nonlinear behavior when subjected to large electrical or mechanical loads. This strong nonlinear material behavior is induced by localized polarization switching (i.e., change of the polarization direction) at the subgrain level. In this article, a nonlinear finite element code is described to model polarization switchings in piezoceramics subjected to large electromechanical loads. The local polarization switching criterion is based on electric displacement combined with stability arguments. To evaluate the model, three cases are studied in this article: a partially electroded specimen simulating 180° polarization switching, a fully electroded specimen simulating 90° switching and a plate containing a void. The analytical results are compared with experimental data obtained from Moire interferometer with reasonable agreement. Stresses in the vicinity of the voids are computed and the results are used to explain fatigue behavior observed in piezoceramics. It has been determ...

A new, rechargeable, thick-film, polymer electrolyte, lithium battery using a high-energy density cathode material (vanadium pentoxide aerogel, 350 mAh/g) has been tested in a pulse-discharge mode of operation. Three separate 12 volt batteries were pulse-discharged through a piezoelectric stack actuator. Since motion rectification devices such as linear motors operate at elevated frequencies, the batteries were pulse-discharged at 10, 100, and 500 Hz. Multiple cycle, charge/discharge data is presented for the three batteries tested in this study. Additionally, a 6 volt battery was fabricated and used to power a piezoelectric actuator patch (chirp source) that was part of a damage detection system.

A parametric study was performed on NiTiCu shape memory alloy torque tubes. Four samples with varying wall thickness values were evaluated for their thermo-mechanical response. The torque against the angular displacement was measured for each sample when purely martensitic and purely austenitic. The recovery torque was measured as a function of the pretwist applied during loading in the martensite phase. The trends observed were compared to three models with relatively good agreement. The recovery torque for biaxial tension/compression-torsion tests were measured with values comparable to pure torsional loadings. During the biaxial loading, a time-dependent phenomenon was observed. To evaluate the time dependence, standard creep tests were performed to elucidate the influence of the load on the temporal response of the material.

In this paper we present a novel method for depositing NiTi thin film by DC sputtering. The film has transformation temperatures very close to that of the target. The new process involves heating the target and does not require compositional modification of the NiTi target. Results from X-ray diffraction, differential scanning calorimeter, four-point probe, Rutherford backscattering, and transmission electron microscopy are presented. These results indicate that compositional modification can be produced by varying the target temperature. Films produced from hot targets have compositions similar to the target while films produced from cold targets were Ti deficient. Films that were produced by gradual heating of the target have compositional gradation through the film thickness. The gradated films exhibit the two-way shape memory effect.

In this article we present results for magnetostrictive composites containing between 10% and 50% Terfenol-D (Tb0.3Dy0.7Fe2) in a nonmetallic binder. The composite consists of aligned Terfenol-D particles representative of a [1-3] fiber composite. For this study we measure the modulus of elasticity and other pertinent magnetostrictive properties. The measured stiffness values fall between the upper and lower bounds predicted by a rule of mixtures approximation. The magnetostriction for the composites rival that of the monolithic at comparable magnetic field levels. A mechanically unloaded 20% volume fraction composite produces 900 ppm and a 30% volume fraction composite preloaded with 8 MPa produces 1000 ppm. Contrary to the belief that the greater the magnetostrictive particulate volume, the greater magnetostrictive properties—this study shows that there is an optimal balance of epoxy and magnetostrictive material that will maximize magnetostriction for a mechanically unloaded specimen. For the matrix ch...

“Hazardous levels of methane in the subsurface occur at numerous locations across the United States.”

Compositional uniformity in NiTi thin films produced under “cold” and “hot” target conditions using d. c. magnetron sputtering is presented in this article. Film deposited under “hot” target condition shows significantly better compositional uniformity compared to those deposited under “cold” target condition. The Ti composition in the film produced under “cold” target condition showed a 2.5 at.% loss relative to the target composition, whereas film produced under “hot” target condition exhibits composition nearly identical to that of the target. XRD and DSC measurements confirm the presence of martensitic phase at room temperature and the shape memory effect in the film deposited under “hot” target condition.

A novel proof-of-concept prototype Mesoscale Actuator Device (MAD) containing microscale components has been developed. The MAD is similar to piezoelectrically driven inchworm motors with the exception that mechanically interlocking microridges replace the traditional frictional clamping mechanisms. The interlocked microridges, fabricated from single crystal silicon, are designed to increase the load carrying capability of the device substantially. Tests conducted on the current design demonstrate that interlocked microridges fabricated with 30% KOH solution support a 9.6 MPa shear stress or that a pair of 5×5 mm locked chips supports a 500 N load. For high frequency operation, an open loop control signal is implemented to synchronize the locking and unlocking of the microridges with the elongating and contracting of the actuator. The system was successfully operated from 0.2 Hz to 500 Hz (or speeds from 2 μm/s to 5 mm/s). The upper limit (500 Hz) is imposed by software and hardware limitations and not related to physical limitations of the prototype device.

Phytoremediation has been implemented at an industrial site in Wisconsin to promote in situ remediation of No. 2 fuel oil-contaminated soil. The goal of the project is to utilize microbial-enhancing processes within the rhizosphere of trees to stimulate biodegradation of diesel range organics (DROs) within four contaminated hot spots at the site. Between 40 and 90% reductions in the concentrations of the DROs were observed over the course of a 24-week bench-scale bioventing study performed in 1994. In addition to a reduction in the concentration of DROs, the chromatograms for those analyses exhibited a relative decrease in the proportion of the more water soluble and available shorter chained or lower molecular weight DROs compared to their higher molecular weight counterparts in the fuel. In addition to a decrease in concentration, this observed change in the pattern of the chromatograms over time is consistent with biodegradation of DROs. An agronomic assessment performed in 1995 indicated that conditio...

A novel proof-of-concept prototype Mesoscale Actuator Device (MAD) is described in this paper. The MAD is similar to piezoelectric driven inchworm motors with the exception that mechanically interlocking microridges replace the traditional frictional clamping mechanisms. The interlocked microridges, microfabricated from single crystal silicon, are shown to support macroscopic loads with exact values dependent upon manufacturing processes. Tests conducted on the current design demonstrate that the interlocked microridges support 16 MPa in shear or that two sets of 3 x 5 mm locked chips support a 50 kgf. Operation of a prototype MAD device containing microridges is accomplished at relatively large frequencies using an open loop control signal. Synchronizing the locking and unlocking of the microridges with the elongating and contracting actuator requires a dedicated waveform in the voltage signal supplied and permitted large operational frequencies. The system was successfully operated from 0.2 Hz to 500 Hz corresponding to speeds from 2,um/s to 5 mm/s. The upper limit (500 Hz) was imposed by software limitations and not related to physical limitations of the current device.

This paper presents research results on the electro–thermomechanical behavior of piezoelectric ceramics for use in actuator applications with an emphasis on ferroelectric fatigue. The material being investigated is a lead zirconate titanate piezoelectric ceramic with the composition PbZr0.53Ti0.47O3 (PZT-5H). Results presented in this paper include an augmented constitutive model that accounts for the temperature-dependent piezoelectric properties. Using this model, nonlinear effects measured at one temperature can be extrapolated to other temperatures with good accuracy. Experimental studies into 180° and 90° polarization switching of PZT-5H indicate that the dielectric flux to dipole the material appears to be an adequate criterion for predicting this nonlinear switching behavior. Fatigue studies show that material degradation is strongly influenced by temperature and by the magnitude of the applied electric field. Above a critical temperature, PZT-5H no longer fatigues in the presence of large electric...

In this paper, we present the results of an experimental study focused on understanding the strain concentrations arising due to nonlinear phenomena associated with polarization switching. A moire interferometry technique is used to measure the normal and shear strains of a PZT-5H piezoceramic undergoing 180 and 90 deg switching. These results include the strain concentrations measured between polarized regions oriented 180 and 90 deg apart. The results show that very large strain mismatches (e.g., as large as 4500 microstrains) occur along the boundary of dissimilar oriented domains, suggesting a source of microcrack initiation and fatigue degradation.

Using ab initio electronic structure calculations, we have investigated the effect of an electric field and of a heavy-metal cap of Pd on the magnetocrystalline anisotropy (MCA) of FePd ultrathin film. Analysis of the energy- and $k$-resolved distribution of the orbital character of the minority-spin band reveals that the perpendicular MCA of the uncapped film mainly arises from the spin-orbit coupling (SOC) between unoccupied Fe ${d}_{xy}$ and occupied Fe ${d}_{{x}^{2}\ensuremath{-}{y}^{2}}$ states. On the other hand, the SOC between the Pd- and Fe-derived $d$ states yields negative contributions to the MCA. We find that the sensitivity of the surface anisotropy energy to the applied electric field is 18 fJ/(Vm) and is due to changes in the occupation of the surface Fe atoms ${d}_{{x}^{2}\ensuremath{-}{y}^{2}}$ and (${d}_{xz},{d}_{yz}$) orbitals. We demonstrate that the thickness of the Pd cap has a dramatic effect on the MCA and can even switch the magnetization from out-of- to in-plane orientation. The underlying origin is the change of the position and orbital character of the spin-polarized quantum well states induced in the Pd cap by varying its thickness. These results have important implications for exploiting heavy metals with large spin-orbit coupling (Ru, Pd, Ta, Pt, or Au) as contacts with ferromagnetic thin films to tailor the magnetic switching of spintronic devices by tuning the cap thickness.

Piezoelectric ceramics contain anomalies which give rise to localized stress concentrations when electric fields are applied. These stress concentrations cause microcracking which leads to electro-mechanical degradation and eventually to material failure. In this paper, a unit cell approach is presented to understand the relationship between material properties and electric field induced stress concentrations around a specific anomaly, i.e., circular void. An exact electro-elastic analysis verified with a finite element model is used to study the stress and electric field concentrations as a function of material properties. Parametric studies indicate that the electric field induced stress concentrations in the material are effectively eliminated for certain values of the piezoelectric coefficients. While a trivial solution to this problem is that the piezoelectric coefficients are zero, other “optimum” coefficients exist. These coefficients do not limit the deformation profile of the piezoelectric and are thermodynamically admissible. Results presented for PZT-4 and PZT-5H support the contention that optimal piezoelectric materials can be manufactured.

The dynamic magnetoelastic properties of a [112]-oriented magnetostrictive composite comprising 0.49 volume fraction of needle-shaped, [112]-oriented Terfenol-D particles and Spurr epoxy were investigated as a function of magnetic bias field. These properties included elastic moduli (E/sub 3//sup H/ and E/sub 3//sup B/), dynamic strain coefficient (d/sub 33/), and magnetoelastic coupling coefficient (k/sub 33/). A randomly oriented composite with 0.51 volume fraction of irregular-shaped, ball-milled Terfenol-D particles was also prepared and characterized for comparison. It was found that the [112] preferential particulate orientation increases non-180/spl deg/ domain-wall motion in the [112]-oriented composite, resulting in maximum negative-/spl Delta/E,d/sub 33/, and k/sub 33/ values of about 10%, 5.5 nm/A, and 0.34, respectively. These are the largest property values reported as yet for magnetostrictive particulate composites, being up to 67% larger than the randomly oriented composite and approach to 65% of the monolithic Terfenol-D.

While Fontan palliation in the form of the total cavopulmonary connection has improved the management of congenital single ventricle physiology, long-term outcomes for patients with this disease are suboptimal due to the lack of two functional ventricles. Researchers have shown that ventricular assist devices (VADs) can normalize Fontan hemodynamics. To minimize blood contacting surfaces of the VAD, we evaluated the use of an external compression device (C-Pulse Heart Assist System, Sunshine Heart Inc.) as a Fontan assist device. A mock circulation was developed to mimic the hemodynamics of a hypertensive Fontan circulation in a pediatric patient. The Sunshine C-Pulse compression cuff was coupled with polymeric valves and a compressible tube to provide nonblood-contacting pulsatile flow through the Fontan circulation. The effect of the number, one or two, and placement of valves, before or after the compression cuff, on inferior vena cava pressure (IVCP) was studied. In addition, the effect of device inflation volume and compression rate on maintaining low IVCP was investigated. With one valve located before the cuff, the device was unable to maintain an IVCP below 15.5 mm Hg. With two valves, the C-Pulse was able to maintain IVCP as low as 8.5 mm Hg. The C-Pulse provided pulsatile flow and pressure through the pulmonary branch of the mock circulation with a pulse pressure of 16 mm Hg and 180 mL/min additional flow above unassisted flow. C-Pulse compression reduced IVCP below 12 mm Hg with 13 cc inflation volume and compression rates above 105 bpm. This application of an external compression device combined with two valves has potential for use as an artificial right ventricle by maintaining low IVCP and providing pulsatile flow through the lungs.

We demonstrate in situ 90\ifmmode^\circ\else\textdegree\fi{} electric field-induced uniform magnetization rotation in single domain submicron ferromagnetic islands grown on a ferroelectric single crystal using x-ray photoemission electron microscopy. The experimental findings are well correlated with micromagnetic simulations, showing that the reorientation occurs by the strain-induced magnetoelectric interaction between the ferromagnetic nanostructures and the ferroelectric crystal. Specifically, the ferroelectric domain structure plays a key role in determining the response of the structure to the applied electric field, resulting in three strain-induced regimes of magnetization behavior for the single domain islands.