Recently, a variety of manufacturing methods have enabled us to produce fine or thin shapes or unique structure of TiNi-based shape memory alloys: e.g., (a) rolled thin plates with a thickness less than 100 μm, (b) drawn fine wires with a diameter less than 50 μm, (c) drawn microtubes with an outer diameter less than 350 μm, (d) sputter-deposited thin films with a thickness less than 1 μm, (e) rapidly solidified ribbons of several tens μm thickness and (f) sintered porous structured materials. The characteristics and applications of these TiNi-based alloys are reviewed.

Electrophoretic deposition (EPD) is a simple, rapid, and low cost method for producing conformal films on patterned electrodes. This paper covers the use of EPD for forming fully dense Lead Zirconate Titanate (PZT) films of twenty microns and less. The three main steps of this process as applied to PZT are covered: (1) formation of a charged suspension of the starting sub-micron PZT powder, (2) deposition of the powder particles on an electrode under the influence of a DC electric field, and (3) fluxing and constrained sintering of the resulting particulate deposit to form a dense continuous film. Using this process we have formed six to ten micron PZT films on an alumina substrate, sintered to fully density at 900°C. In a fourteen micron film we have achieved a piezoelectric d₃₃ coefficient of 140 picoCoulombs/Newton, and a dielectric constant of 1,000 with a loss tan δ of 0.045.

Several mechanical designs capable of amplifying the performance of electroactive ceramic actuators and sensors have been presented in the smart materials and structures literature. The realization of these designs on the microscale requires a fabrication technique capable of producing intricate ceramic and electrode structures. Microfabrication by coextrusion (MFCX) provides a simple and inexpensive method to produce axially symmetric structures. It allows concurrent shaping of both the electroactive ceramic and electrode materials, thereby removing the necessity of performing complex electroding procedures after sintering the ceramic. Typically these post firing procedures are difficult, if not impossible, with microdevices. The MFCX technique is a two step process. The first is the use of coextrusion to shape powder-filled thermoplastic compounds into green microsized parts. The second is a co-firing step to achieve binder burnout and densification of both the ceramic and electrode materials. Electroactive ceramic and silver palladium parts with 5 micron feature sizes have been fabricated using this method. This article includes a description of this new microfabrication technique and results of efforts to fabricate microsized ceramic objects including a fenestrated electrostrictive ceramic-silver palladium electrode structure and a piezoelectric hydrophone.

Properties of piezoelectric ceramics important for actuator applications have been measured as a function of grain size. Fine grain piezoelectrics (≤1 μm) have been found to exhibit improved machinability and increased mechanical strength over conventional materials. Actuators made from fine grain ceramic are, therefore, expected to have improved reliability, higher driving fields, and lower driving voltages (from thinner layers in stacked or co-fired actuators) over devices fabricated from conventional materials. TRS Ceramics in collaboration with the Pennsylvania State University's Materials Research Laboratory, has developed fine grain piezoelectric ceramics with minimal or no reduction in piezoactivity. New chemical doping strategies designed to compensate ferroelectric domain clamping effects from grain boundaries have been successful in yielding submicron grain sized ceramics with both low and high field properties equivalent to conventional materials. In the case of Type II ceramics, reduced grain size results in a very stable domain state with respect to both electric field and compressive prestress. Work is in progress to develop both epoxy bonded stack and co-fired actuators from fine grain piezoelectrics.

In this paper we report on polycrystalline thin films sputter- deposited at elevated temperatures. The grain size of the films was changed by controlling the film thickness. A series of 4 samples with thicknesses ranging from 0.1 μm to 1 μm was studied. The magnetic properties of the films were characterized by vibrating sample magnetometer measurement technique. The magneto-mechanical properties of the films were determined by dynamic magneto-mechanical measurements. The coercivity of the films was found to increase linearly with decreasing film thickness. A sharp transition occurred for film thickness below 0.3 μm and the coercivity decreased to 100 Oe as the film thickness reached 0.1 μm. The saturation magnetization of the films was calculated from the magneto-mechanical measurements. The values were found to agree with those determined from the VSM measurements for all the samples but the thinnest film for which VSM and magneto-mechanical values diffracted by one order of magnitude. It is suggested that the low coercivity of the 0.1 μm film can be associated with the onset of superparamagnetism in the nanograins of the film.

This paper describes the fabrication of functionally-tailored nanoparticle-based thin-films using the ionic self-assembled monolayer (ISAM) method. ISAM thin-films have been created by the consecutive coating of ceramic, polymer, metal and single-crystal substrate materials with numbers of layers of oppositely-charged polyelectrolyte species. We specifically report here the chemical synthesis of nanoparticles of several inorganic materials, having mean cross-sectional dimensions less than 10 nm and particle size distribution standard deviations as small as 0.5 nm or less. We next report the incorporation of these inorganic nanoparticles and high-performance polymers into multi-layer assemblies with as many as several hundred individual monolayers, each having excellent 2D surface uniformity. Potential applications in smart optical, electromagnetic and mechanical systems are discussed.

This paper studies the effect of Ta addition on the martensitic transformation characteristics and the X-ray visibility of NiTi shape memory alloys. It was found that: (1) The transformation temperatures of the Ti₄₉Ni₅₁ binary alloy increase drastically by an addition of 0 -- 4at%Ta, but only slightly when the concentration exceeds 4at%. (2) The addition of Ta greatly decreases the sensitivity of the martensitic transformations to the variation in the Ni-Ti ratio. (3) The addition of Ta to a TiNi binary alloy can improve its X-ray visibility.

This study investigates the properties of TiNi and TiNi-Cu (K- alloy) Shape Memory Alloys and their behavior in torsion (uniaxial) and combined tension-torsion (biaxial). Test results include torque versus angle curves and recovery torque versus pretwist for both uniaxial and biaxial loading. Preliminary results for low cycle fatigue are also presented. The wall thickness of the torque tube influences all of these curves considerably due to the gradation of stresses and strains through the thickness. All test data presented in this paper is for moderate torques where maximum shear strains are below 3.5% and as such represent an actuator capable of long fatigue life, based on previous experimental data for wire systems. A theoretical model for recovery torque is also described.

The evolution of inhomogeneous deformation in a NiTi shape memory alloy under uniaxial tension is studied both experimentally and analytically. Interesting features of stress-induced phase transformation fronts are observed in experiments of NiTi strips. The nucleation of a new phase occurs as a sharp band of localized strain inclined at 55° to the axis of loading. This angle agrees with a rather well-known hand calculation based on continuum plasticity. Under prescribed end displacement the new phase then spreads either by steady-state propagation of angled transition fronts or by an alternating pattern of finger-like features. These features are successfully captured by finite element analyses with a special trilinear stress-strain model having an intermediate unstable branch. It is a relatively simple continuum-based approach which captures the interplay of the material instability and more global structural constraints.

A torsional actuator generating angular displacement from the piezoelectric shear strain was developed. The actuator is a tube consisting of an even number of the segments poled along the length, which are adhesively bonded together, and the joints act as electrodes to apply the driving voltage. The experimental data measured on the prototype actuator: (i) prove the proposed concept of the torsional actuator, (ii) show that the actuator functions well under the torque load, and (iii) demonstrate that is has superior characteristics compared to previously reported designs of torsional actuators. In addition, one of the obvious advantages of the present design of the actuator is its simplicity: the piezoelectric shear strain is transformed directly into the angular displacement, whereas in the previously reported actuators, the conversion mechanism into the torsional motion was rather complicated which thus required a sophisticated design of the whole system.

Thin film composite sensors have been fabricated which incorporate piezoelectric ceramic particles in an polymer matrix. These composites are more compliant than pure piezoelectric ceramics and can be embedded in thick structures to monitor internal mechanical conditions, such as the evolution of damage. Composite films consisting of Ca-modified lead titanate particles in a poly(vinylidene fluoride-trifluororethylene) matrix are examined in this paper. The viscoelastic properties of these composites (with various volume fractions, up to 60% ceramic) have been measured over a range of frequencies (0.01 to 100 rad/sec). The complex h^*₃₁ piezoelectric coefficient has also been measured for these composites for various volume fractions and over a frequency range from 5 to 100 rad/sec. The magnitudes and phase angles of the piezoelectric coefficients are shown to be highly frequency dependent.

Currently, smart structures utilize both polymeric sensor and PZT-based actuators. The benefit of self-sensing calls for the development of integrated actuator/sensor composites. This paper addresses the development and properties of this new class of smart materials. Controlled porosity (amount, size, shape and distribution) were fabricated using sintering, blending and spin- on-disc. New flexible, thin polymer based composites were obtained. The optimization between d₃₁ and g₃₁ was performed to provide both actuator and sensing capabilities. It was found, that processing conditions including poling can be adjusted to provide the contribution from both PZT and VDF.

Short carbon fibers (5 mm long, 15 micrometers diameter) in polymer and cement matrices provide piezoresistive strain sensors that have their DC electrical resistivity change reversibly upon strain. For fibers (5 - 10 vol.%) in an epoxy matrix, the resistivity increases upon tension and decreases upon compression, due to the change in proximity between adjacent fibers in the composite, the gage factor (fractional change in electrical resistance per unit strain) is up to 97 under compression and up to 24 under tension. For fibers (0.2 - 0.5 vol.%) in a cement matrix, the resistivity increases upon tension and decreases upon compression, due to the change in contact resistivity between fiber and matrix; the gage factor is up to 700.

Piezoelectric materials produce a voltage proportional to an applied pressure. Using this phenomenon, piezoelectric polymer sensors are already being used for collecting traffic data including weight-in-motion, measuring speeds and counting axles. The polymer sensors are usually in the form of a long tape or cable embedded within long blocks of elastomeric material. These sensor assemblies are then installed into grooves, which are cut into roads perpendicular to the traffic flow. The biggest disadvantage of these sensors is that the piezoelectric output is not uniform with temperature, thus leading to large uncertainty in the data collected. Piezoelectric ceramics have a much more stable response over a large temperature range. However, until now they have not been used for traffic data sensors because of their inherent brittleness. In this research project flexible ceramic/polymer composite strips have been fabricated for use as piezoelectric sensors for measuring large vehicle loads. Here, the ceramic is the active piezoelectric material that is embedded in a flexible non-piezoelectric polymer. After encapsulating these sensors in elastomeric blocks in aluminum channels, the voltage output of the composite for different loads have been determined. Also, these composite sensor assemblies are being installed on a test road in order to perform actual measurements.

The piezoelectric properties of relaxor based ferroelectric single crystals, such as Pb(Zn_1/3Nb_2/3)O₃ - PbTiO₃ (PZN-PT) and Pb(Mg_1/3Nb_2/3)O₃ - PbTiO₃ (PMN- PT) were investigated for electromechanical actuators. In contrast to polycrystalline materials such as Pb(Zr,Ti)O₃ (PZT's), morphotropic phase boundary compositions were not essential for high piezoelectric strain. Piezoelectric coefficients (d₃₃'s) > 2500 pC/N and subsequent strain levels up to > 0.6% with minimal hysteresis were observed. Crystallographically, high strains are achieved for <001> oriented rhombohedral crystals, though <111> is the polar direction. Ultrahigh strain levels up to 1.7%, an order of magnitude larger than those available from conventional piezoelectric and electrostrictive ceramics could be achieved, being related to an E-field induced phase transformation. Strain vs. E-field behavior under external stress was also much superior to that of conventional piezoelectric ceramics. High electromechanical coupling (k₃₃) > 90% and low dielectric loss <1%, along with large strain make these crystals promising candidates for high performance solid state actuators.

The quasistatic electromechanical and dielectric behaviors of different electroactive actuator materials are investigated under the simultaneous influence of uniaxial stress and temperature at high driving field. An experimental setup capable of applying 9000 newtons of uniaxial force was carefully designed, based on a precisely guided steel frame. Extra caution was taken to minimize the effects of mis-alignment and contact surface clamping. The materials examined in this study include a prospective PLSnZT anitferroelectric ceramics which is currently under development, as well as electrostrictive ceramics, namely PMN-PT 90/10 and PMN-PT 76/24. To assess the applicability of these materials in real systems, multilayer stacks were assembled and their response to stress and temperature was examined. The overall strain of the PLSnZT composition showed increases with increasing uniaxial stress. This might be the result of re-orientation of antiferroelectric domains under pre-stress. It also showed excellent stability in strain over the temperature range 20 to 75°C under stress as high as 100 MPa. In contrast, the electrostrictive ceramics are less dependent on stress than antiferroelectrics but more susceptible to temperature changes.

An ongoing investigation into understanding the nature and mechanics of damage in piezoelectric material under combined cyclic electrical and static mechanical loads is described. The piezoelectric is subjected to large field excursions that are sufficient to cause polarization switching at least around internal anomalies, as well as mechanical stresses with values well below ultimate strength of the material. Experimental work is conducted on PZT-5H with macroscopically engineered dissimilar (180°) domain structures. All samples contain a seed notch to introduce a stress concentration at a specified location and eliminate questions associated with electrode attachment. Results indicate that for specimens undergoing significant domain wall motion the crack initiation occurs after only 20 - 100 cycles while for specimens undergoing small domain wall motion cracks initiate after 800,000 cycles. Compressive mechanical loads are found to retard damage growth. Experimental results are explained with data obtained from a finite element model. The principal conclusion is that domain wall motion on both micro and macro levels is responsible for crack initiation and degradation of the material during cycling loading.

We present a non-linear theory for electromechanical materials based on a Taylor's series expansion of the thermodynamic potentials to 3rd and higher order terms in field and stress, and we show that this general theory is applicable to both piezoelectric and ideal electrostrictive materials depending with an appropriate choice of material coefficients. The model allows for the non-zero piezoelectric behavior found in some nominally electrostrictive materials. The quasistatic non-linear equations used to describe low frequency electromechanical devices are shown to account for saturation in both strain and polarization as well as the stress dependence. The `reversible' electrostrictive ceramic PMN/PT/La (0.9/0.1/1%) operating above T_max is used to illustrate the suitability of the model. Under a DC bias field, these materials behave as a piezoelectric ceramic material with C_∞) symmetry. The effective piezoelectric is found to be linear as a function of the DC bias field up to about 0.5MV/m. Above 0.5 MV/m, the piezoelectric and the electromechanical coupling constants begin to saturate due to higher 4th order electrostriction (S ∝ kE⁴ with k negative), which is shown to be the result of the saturation in the dielectric response. A switchable, low field, linear component of the piezoelectric voltage coefficient, g, is found in the S vs D response. The g coefficient is found to change sign depending on the sign of the measurement field. These materials behave as a tunable piezoelectric with the piezoelectric coefficient being directly proportional to the electrostrictive coefficient and the DC bias field, up to saturation.

Micromachining technologies were established to fabricate microelectrode arrays and devices for interfacing parts of the central or peripheral nervous system. The devices were part of a neural prosthesis that allows simultaneous multichannel recording and multisite stimulation of neurons. Overcoming the brittle mechanics of silicon devices and challenging housing demands close to the nerve we established a process technology to fabricate light-weighted and highly flexible polyimide based devices. Platinum and iridium thin-film electrodes were embedded in the polyimide. With reactive ion etching we got the possibility to simply integrate interconnections and to form nearly arbitrary outer shapes of the devices. We designed multichannel devices with up to 24 electrodes in the shape of plates, hooks and cuffs for different applications. In vitro tests exhibited stable electrode properties and no cytotoxicity of the materials and the devices. Sieve electrodes were chronically implanted in rats to interface the regenerating sciatic nerve. After six months, recordings and stimulation of the nerve via electrodes on the micro-device proved functional reinnervation of the limb. Concentric circular structures were designed for a retina implant for the blind. In preliminary studies in rabbits, evoked potentials in the visual cortex corresponded to stimulation sites of the implant.

A physical model of the human elbow joint was designed using the polymer fiber polyacrylonitrile (PAN), developed at the University of New Mexico. The elbow model uses six PAN fiber bundles, as artificial muscles, to create the forces needed for elbow movement. These six fiber bundles were designed to imitate the major muscles that cross the human elbow joint. Four distinct movement tasks (elbow flexion/extension and forearm pronation/supination) were designed into the physical mode. Several steps were taken to meet this objective. First, the mechanical properties of the PAN fibers were characterized using the techniques developed by A. V. Hill, and compared with his results. The results show that the fiber mechanical properties have similarities to human muscle properties, and thus permitting a realistic elbow model to be developed. Second, a method of encasing the individual bundles of fibers was developed. The encasing lengthens and shortens with the fibers, prevents fluid leakage, and does not deteriorate given the acid and base fluid components. Third, a method of supplying and removing the activating fluids was developed. This system is chemically resistant, provides a method for controlling inlet and exit fluid flow, and allows for complete fluid exchange in less than 5 seconds. Finally, a microcontroller was incorporated to provide joint position and velocity control based on joint potentiometers and provide real-time feedback of joint positions. Using these components, a human elbow joint system was developed that allows movement in two degrees of freedom. Due to the characteristics of the PAN fiber bundles, the elbow joint was slower and weaker than originally designed. System improvements relate closely to increasing fiber bundle force and decreasing the reaction time constant.

This paper presents a design of an active knee and leg muscle exerciser using a shape memory alloy (SMA) rotary joint actuator. This active exerciser is designed for a paraplegic to exercise his or her knee and leg muscles. The exerciser is composed of a lower extremity orthosis or a knee brace, an SMA rotary joint actuator, and an electronic control unit. The lower extremity orthosis and knee brace are commercially available. The analysis model of the SMA rotary joint actuator is introduced and the design formulas are derived. A quasi-static analysis of the SMA rotary joint actuator is assumed in this design. The actuating component of the SMA rotary joint actuator is a bundle of lengthy SMA wires which are wrapped on several wrapping pulleys. A constant force spring is incorporated in this actuator to provide the SMA wires with a bias force to maintain a recoverable initial position of the actuator. A prototype of the active knee and leg muscle exerciser is designed, and an electronic control unit in the prototype provides users with a means of adjusting forward rotation speed and cycle time of the exerciser.

A linear motion-controlling or power-actuating cylinder can be found in virtually all types of machinery. In many applications, however, limitations in performance of longevity of operation exist due to a number of factors ranging from nature's environmental extremes to the demands of complex design and engineering requirements. Industry has come to accept the limited flexibility of current power- and motion-regulating mechanisms such as hydraulic valve-controlled actuators, and oftentimes chooses to design around the inherent flaws and drawbacks of these basic components. As a result, the level of maintenance and potential for mechanical failure are greater than necessary in many applications from routine road construction where hydraulic machinery is instrumental, to undersea operations where man relies heavily on hydraulic-cylinder devices during most scientific, geographic and biological research excursions. With ultimate flexibility and environmental adaptability providing the key motivation, E. P. Industries, Inc. has developed and prototyped a system of Novel Robotic Actuators to function where operational or environmental demands exceed the capabilities of conventional hydraulic-valve devices. The objective in developing the Robotic Muscle is to replace a typical hydraulic cylinder actuator with a relatively more compact `muscle-like' actuator exhibiting maximum flexibility and a superior strength-to-weight ratio while resisting the harsh temperatures and deterioration factors presented by unusual operating environments. Progressive development of the Robotic Muscle will be directed to use as an artificial biological replacement.

The possibility of using certain polymer gels as artificial skeletal muscle was investigated due to its ability to shorten or contract when saturated in acidic or basic solutions, respectively. Polyacrylonitrile (PAN) fiber is such an example of a polymer gel. Mechanical performance characteristics of PAN fibers were studied and compared to voluntary muscle mechanical properties. The experimental methods used to determine the mechanical properties of the PAN fibers were modeled after A. V. Hill's classic experiments of the force-length and force-velocity properties of voluntary muscle. In addition, the force-molarity, length-molarity, and force-time characteristics were measured for the PAN fibers. These characteristics were quantitatively and qualitatively compared to voluntary muscle properties when relevant and used to determine the feasibility of implementing PAN fibers as artificial skeletal muscle in modeling movement across the human elbow joint. The results indicated qualitative similarities with the mechanical characteristics of voluntary muscle, especially force-velocity property. The force capabilities of the PAN fibers were at the lower end of voluntary muscle force generation. (i.e. 20 - 200 N/cm²) Activation- contraction time was also substantially larger than skeletal muscle. Based on these data, it was concluded that using PAN fibers as artificial muscles in modeling the human elbow joint is feasible only under certain conditions. Additional characterization studies are needed to determine if individual PAN fibers can generate higher forces using a different experimental protocol or a different architectural arrangement of the fibers.

NASA is seeking to reduce the mass, size, consumed power, and cost of the instrumentation used in its future missions. An important element of many instruments and devices is the actuation mechanism and electroactive polymers offer an effective alternative to current actuators. In this study, two families of electroactive polymer materials were investigated, including bending ionomers and longitudinal electrostatically driven elastomers. These materials were demonstrated to effectively actuate manipulation devices and their performance is being enhanced in this on-going study. The recent observations are reported in this paper, which also include cryovac tests at conditions that simulate Mars environment. Tests at T = -140°C and P ~ 1 Torr, which are below Mars conditions, showed that the bending actuator was still responding with a measurable actuation displacement. Analysis of the electrical characteristics of the ionomer showed that it is a current driven material rather than voltage driven. Measurements of transient currents in response to a voltage step shows a time constant on the order of few seconds with a response speed that is enhanced with the decrease in drive voltage. The ionomer main limitation is its requirement for being continuously moist. Tests showed that while the performance degrades as the material becomes dry, its AC impedance increases, reaching an order of magnitude higher than the wet ionomer. This response provides a gauging indication of the material wetness status. Methods of forming the equivalent of a skin to protect the moisture content of the ionomer are being sought and a limited success was observed using thick platinum electroding as well as when using polymeric coating.

The high-voltage bulk photovoltaic effect in ferroelectrics was theoretically and experimentally studied focusing on the nonlinear dielectric response. The steady current in the absence of applied voltage, called `photocurrent', is considered as a result of photocarriers and the asymmetric electromotive force induced by near-ultraviolet radiation. A model accounting for the generation of electric field acting as an effective dc field for the photocarriers was explained in terms of the photoinduced nonlinear polarization and the Lorentz field in dielectrics. Experimental results on electric photoconductivity, photocurrent and photovoltage of a PLZT ceramic were analyzed by using exponential functions based on the model. An adjustable parameter was introduced in relation to the incoherence of the illuminating light as an electromagnetic wave. It was found that the exponential functions by the present model can give better fitting to the experimental data than that by a linear function previously used.

Discs of polyaniline-silver-polymer electrolyte composites exhibit rapid and reversible changes in their microwave impedance when small electric fields are applied across then in a resonant coaxial line test set. The experimental data show that the initial conductivity of the materials is dependent on the concentration of silver metal and suggests that changes in resistance due to chemical switching take plane, at least in part, in the manufacture of the composites. The experimental data show that changes in the gradient of the cyclic voltammograms coincide with large changes in microwave reflectivity consistent with increasing conductivity of the composite when fields are applied. The reverse change occurs when the fields are removed. Measurements of the switching speed have shown that the composites are able to switch between the different states at in times of less than a second for more than one million switching operations with no depreciation of the material. Large area films have also been studied in the front of waveguide devices and measured in a microwave transmission mode. The results show that large changes in microwave impedance occur with the application of small electric fields (~ 15 V cm^-1).

Carbon fibers are widely used as a reinforcement in structural composites. The use of these fibers that are already in the composite for strain sensing eliminates the need for strain gages, optical fibers or other sensors, thus decreasing cost and improving durability. For this purpose, the electromechanical behavior (change in DC electrical resistivity upon strain) of the fibers was investigated. A single bare carbon fiber increases its electrical resistance (not resistivity) reversibly upon tension due to changes in dimensions, such that the gage factor (fractional change in resistance per unit strain) in +2. A single carbon fiber embedded in epoxy (a common matrix) has its volume electrical resistivity increased by 10% after curing at 180°C and subsequent cooling of the epoxy, due to the compressive residual stress resulting from the thermal contraction mismatch between fiber and epoxy. Subsequent tension of the embedded fiber at its two exposed ends decreases the residual stress and causes the fiber resistivity to decrease back to its value before embedding, such that the resistivity decrease is reversible, with gage factor -17. Excessive tension causes the resistivity of the fiber to increase, due to damage. Thus, carbon fiber in epoxy is a sensitive piezoresistive strain sensor.

This paper discusses a number of recent findings in connection with ion-exchange polymer-noble metal composites (IPMC) as biomimetic sensors and actuators. These smart composites exhibit characteristics of both actuators and sensors. Strips of these composites can undergo large bending and flapping displacement if an electric field is imposed across their thickness. Thus, in this sense they are large motion actuators. Conversely by bending the composite strip, either quasi-statically or dynamically, a voltage is produced across the thickness of the strip between the two conducting electrodes attached. Thus, they are also large motion sensors. The output voltage can be calibrated for a standard size sensor and correlated to the applied loads or stresses. They can be manufactured and cut in any size and shape and in particular in the form of micro sensors and micro actuators for MEMS applications. In this paper first the sensing capability of these materials is reported. The preliminary results show the existence of a linear relationship between the output voltage and the imposed displacement for almost all cases. Furthermore, the ability of these ionic polymer-metal composites as large motion actuators and robotic manipulators is presented. Several muscle configurations are constructed to demonstrate the capabilities of these IPMC actuators. This paper further identifies key parameters involving the vibrational and resonance characteristics of sensors and actuators made with IPMC's. When the applied signal frequency is varied, so does the displacement up to a point where large deformations are observed at a critical frequency called resonant frequency where maximum deformation is observed. Beyond which the actuator response is diminished. A data acquisition system was used to measure the parameters involved and record the results in real time basis. Furthermore, reported in this paper are load characterization of such active polymer composites made with a noble metal such as platinum. The results showed that these actuators exhibit good force to weight characteristics in the presence of low applied voltages. Finally, reported are the cryogenic properties of these muscles for possible use by NASA in a harsh outer space environment of a few Torrs and temperatures of the order of -140 degrees Celsius. These muscles are shown to work quite well in such harsh cryogenics environment and thus present a great potential as sensors and actuators that can operate at cryogenic temperatures.

A new material for damping and energy-absorbing has been developed using a powder particle assembling technique. Powder particles of polystyrene coated with nickel-phosphorous alloy layers using electroless plating were assembled and sintered at high temperature. A closed cellular solid structure containing polystyrene was then constructed. The mechanical and ultrasonic properties of this cellular solid were measured at room temperature and at high temperatures. The compressive tests show that Young's modulus of this cellular solid is very small as are the changes due to increasing temperature, and the cellular solids have a high energy absorption. Ultrasonic measurement showed that the attenuation coefficient of this cellular solid is very large and would change due to increasing temperature. These results indicate that this cellular solid can be used for energy absorbing and passive damping systems.

The investigation of the behavior of the ferroelectric phase transition with magnetic field tuning and concentration change is highly attractive owing to the possibility to prepare alloying samples and to predict theoretically the parameters of the magnetic field and concentration response at relatively small concentrations. These parameters may be extracted from the equation of states of the perovskite under investigation in the assumption of the linear response. The study of the movement of the paraelectric-ferroelectric interphase boundary in (Ba,Sr)TiO₃ with concentration change and in constant magnetic fields is provided in the framework of the mean-field theory. The analytical solution for the parameters of motion of the interphase boundary is applied to the calculations of the splitting of domain walls in (Ba,Sr)TiO₃ with the magnetic field tuning for different concentrations of Sr. The calculations are based on the experimental data for the Curie-Weiss constant and for the parameters of the Landau-Ginzburg expression for the free energy.

Research at the University of Illinois School of Architecture Material's Lab is being done on a biomimetic building material with the unique properties of bone. This polymer/ceramic composite will mimic bone by controlling the (1) the structure and form of the material, (2) chemical makeup and sequencing of fabrication, (3) ability to adapt to environmental changes during fabrication, and (4) ability to later adapt and repair itself. Bones and shells obtain their great toughness and strength as a result of careful control of these four factors. The organic fibers are made first and the matrix grown around them as opposed to conventional ceramics in which any fibers are added to the matrix. Constituents are also placed in the material which allow it to later adapt to outside changes. The rules under which bone material naturally forms and adapts, albeit at a macroscale, are followed. Our efforts have concentrated on the chemical makeup, and basic sequencing of fabrication. Our research sought to match the intimate connection between material phases of bone by developing the chemical makeup.

The issues of processing and characterization of pultruded smart composite reinforcements with the embedded fiber optic sensors are discussed. These fiber reinforced polymer reinforcements incorporate the optical fiber sensors to provide a strain monitoring of structures. The required modification of the pultrusion processing technology to allow for the incorporation of fiber optic sensors is developed. Fabry Perot and Bragg Grating optical strain sensors were chosen due to their small size and excellent sensitivity. The small diameter of the sensor and optical fiber allow them to be embedded without adversely affecting the strength of the composite. Two types of reinforcement with vinylester resin were used to produce the experimental 9.5 mm diameter rods. The reinforcements were carbon and E-glass fibers. In order to fully characterize the pultrusion process, it was decided to subject the strain sensors separately to each of the variables pertinent to the pultrusion process. Thus, sensors were used to monitor strain caused by compaction pressure in the die, compaction pressure plus standard temperature profile, and finally compaction pressure plus temperature plus resin cure (complete pultrusion process). A strain profile was recorded for each experiment as the sensor travelled through the pultrusion die, and for the cool-down period after the sensor had exited the die.

Electroactive polyaniline (PANI)/MoO₃ nanocomposite ultrathin films were fabricated by a novel molecular self-assembly process based on the alternate deposition of PANI and inorganic polyanion isopolymolybdic acid (IPMA). Unlike the already-used layer-by- layer process based on electrostatic attraction, the process was based on acid-base reaction (or doping) of emeraldine base and IPMA. The process was monitored by UV/Vis spectroscopy and ellipsometry measurement.

the conditions of formation and fields of application of the hybrid inorganic-organic complexes based on polyvinyl alcohol (PVA), variable-valence metals, polyacids, heteropolyacids and orthophosphoric acid are evaluated by rheological methods with regard for electrophysical, optical and sorption properties. The modification of hydrogen-bonded complexes with the applied electric, magnetic, thermal fields and sorption of water vapor changing the system of inter- and intramolecular hydrogen bonds are discussed. Evaluation is made of an influence of the type and concentration of components on the properties and structure of the complexes. The presence of sensitivity of the compositions to applied fields is related to formation acid of the structure- sensitive complexes between PVA molecules and metal ions Cu²⁺, Ni²⁺, Co²⁺, Fe³⁺ as well as the orthophosphoric acid or polyacids.