When is a human-made actuator an artificial muscle. Natural actuators in the animal kingdom vary greatly in their capacity and role. Maximum stress variety by 100-fold as does the velocity at which muscles contract. Some muscles generate near maximum force over broad strain ranges, while others function over only the narrowest ranges. Frequencies of operation range from less than 1 Hz to 1000 Hz. Mass- specific power output can reach over 250 W/kg muscle. Muscles function not simply as force generators, but as springs and dampers. Our isolated muscle experiments on insects show that some muscles function primarily as energy absorber sand have a role in control, while others are effective at power generation. At present, we are evaluating EAPs to see where these actuators fit in the functional space of nature's muscles. EAPs appear particularly promising as artificial muscles for insect-sized robots.

Electroactive Polymers (EAP) are promising as a new class of actuation materials being considered in a wide range of applications. Their large electrically induced strains, low density, ease of processing, and mechanical flexibility offer advantages over traditional electroactive materials. However, before these materials can be properly exploited, their electrical and mechanical properties must be properly quantified. Two general types of EAP can be identified including wet (hydrated) and dry materials. The first type requires relatively low voltages (<10V) to achieve large bending deflections (more than 90°). This class usually needs to be hydrated and electrochemical reactions may occur. The second type of EAP involves electrostrictive and/or Maxwell stresses. These types of materials require large electric fields (>100MV/m) to achieve large extensional deformation (>4%). Some of the difficulties that are involved with the characterization of the properties of EAP include nonlinearity, large compliance, non-homogeneity formed during processing, etc. In order for this technology to fully mature, the authors are developing characterization techniques to quantify their electroactive responses and material properties. This paper focuses on a new testing procedure for bending EAP. Results for ion exchange Flemion membranes are presented.

Carbon nanotubes are of major interest because they combine nanoscale dimensions, structural regularity, exceptional mechanical properties, and interesting electrical properties. We have been primarily concerned with the use of nanotube assemblies as novel electromechanical actuators. The use of nanotube sheets as electromechanical actuators (artifical muscles) has provided encouraging results. However, the mechanical performance observed to date for nanotube sheets are far below those inherent for the individual tubes, and this aspect has severely limited the stresses generated by actuation. The previously demonstrated nanotube actuators are based on tangled arrays of bundled single-wall nanotubes. We here show the first example of an electromechanical actuator based on multi-wall carbon nanotubes. In contrast with the disordered assembly of bundled nanotubes in the previous actuator sheets, the present actuator sheets are based on arrays of parallel non- bundled multi-wall nanotubes in which the tube direction is orthogonal to the sheet plane. The multi-walled nanotubes in these sheets have a defined length (in the range of 5 to 40 μm) and diameter (in the range 10 to 60 nm). While the previous single-wall nanotube actuators are based on chain- direction dimensional changes, the present actuators utilize the electrostatic repulsion between electrical double layers associated with parallel multi-wall nanotubes. The electrochemical properties of these aligned nanotube arrays was studied in a number of different electrolytes, since electrochemical charge injection is important for actuation and for other nanotube applications - such as for energy storage in a supercapacitor. In addition, we have demonstrated the electrochemical deposition of conducting polymer on the nanotube arrays, and have shown that the resulting polymer/nanotube composites provide a high pseudocapacitance.

There is considerable need for light, low-volume actuators having long-cycle-life that can generate displacements and high forces when low voltages are applied. Electroactive polymers possess some of these characteristics, but improvements are needed. We describe work on a promising new type of actuator that is based on non-faradaic electrochemical charge injection in carbon nanotube sheets. While large actuator strokes combined with giant stress generation capabilities are predicted for optimized materials, the present stage of actuator development is embryonic and major materials advances are required to realize these features. The present work describes recent advances in increasing the actuator stroke and stress generation capabilities well above our initially obtained values for carbon nanotube actuators. Operating these actuators in 1M NaCl at low voltages (-0.5 to 1.5 V vs. SCE) we obtained actuator strain of up to 1%. Although the generated stresses are much higher than those of natural muscles, they are many orders of magnitude lower than predicted for nanotube sheets that fully utilize the mechanical properties of the individual nanotubes.

Peizoelectric and electrostrictive polymers are widely used in many areas of electromechanical actuation and transduction. This paper summarizes the current status and recent works in this class of polymers. For the piezoelectric polymers, the electromechanical properties of poly(vinylidene fluoride-trifluoroethylene) copolymers (P(VDF-TrFE), which possess the best piezoelectric performance among the known piezopolymers, are presented. In order to improve the strain capability and other electromechanical properties, the large electrostrictive response and high electromechanical conversion efficient near a first order ferroelectric-paraelectric transition of P(VDF-TrFE) copolymer were exploited. It is shown that the copolymer, treated with high energy electron irradiation, exhibits high electrostrictive strains (-5% longitudinal strain under 150 MV/m and 3.5% transverse starin under 100 MV/m) with high strain energy density, high load capability and improved electromechanical coupling factor. For the comparison, the works related to the Maxwell stress induced strain response in soft polymers are also discussed.

Extremely large strains were achieved with elastomeric polymer films that are subject to high electric fields. The films were coated on both sides with complaint electrode material. When voltage was applied, the film compressed in thickness and expanded in area. The strain response is dominated by the electrostatic forces produced by the charges on the compliant electrodes. Actuated strains up to 117% were demonstrated with silicone elastomers, and up to 215% with acrylic elastomers. A key to achieving these large strains is to introduce a high prestrain to the film. Specific energy densities were much greater than those of other field-actuated materials. Because the response is electrostatic in nature, the actuation mechanism is predicted to be fast. Response speeds in excess of 2000 Hz have ben demonstrated in silicones. Acrylic response speeds are more than an order of magnitude slower, although the reason for this difference is not yet known. Measurement of material viscoelastic and electrical properties predicts that high efficiencies (> 80%) may be achieved with efficient driver circuits. A variety of actuators, including electrooptical devices, diaphragm pumps, and muscle like linear actuators, have been demonstrated with these materials, suggesting that this technology is well suited to small-scale electromechanical devices and robots.

Actuator mechanisms that are lightweight, durable, and efficient are needed to support telerobotic requirements, for future NASA missions. In this work, we present a series of electromechanically active polymer blends that can potentially be used as actuators for a variety of applications. This polymer blend combines an electrostrictive graft-elastomer with a ferroelectric poly (vinylidene fluoride-trifluoroethylene) polymer. Mechanical and piezoelectric properties of the blends as a function of temperature, frequency and relative composition of the two constituents in the blends have been studied. Electric field induced strain response of the blend films has also been studied as a function of the relative composition. A bending actuator device was developed incorporating the use of the polymer blend materials. The results and the possible effects of the combination of piezoelectricity and electrostriction in a material system are presented and discussed. This type of analysis may enable the design of blend compositions with optimal strain, mechanical, and dielectric properties for specific actuator applications.

In order to characterize the electromechanical properties of newly developed electrostrictive poly(vinylidene fluoride- trifluorethylene) copolymers for practical device applications, the following results are presented: 1) The driving field amplitude dependence of the material response. It was found that M(S = ME²) exhibits the driving field amplitude dependence and that the apparent piezoelectric coefficient for the material under DC bias depends on both the driving field amplitude and DC field. 2) Load capability. The copolymer film has a high mechanical load capability. For example, the transverse strain remains 0.6% at 47MV/m under a tensile load of 45 MPA. The load dependence of the material response prove that the electric field induced strain in the copolymer films mainly originates from the electric field induced phase transition in the crystal regions. 3) Frequency dependence of the material response. Although the strain response decreases with increasing frequency, it is found that the strain response at 1 kHz can reach more than 80% of the response at 1Hz.

An ionic polymer-metal composite (IPMC) consisting of a thin Nafion sheet, platinum plated on both faces, undergoes large bending motion when an electric field is applied across its thickness. Conversely, a voltage is produced across its faces when it is suddenly bent. A micromechanical model is developed which accounts for the coupled ion transport, electric field, and elastic deformation to predict the response of the IPMC, qualitatively and quantitatively. First the basic 3D coupled field equations are presented, and then the results are applied to predict the response of a thin sheet of an IPMC. Central to our theory is the recognition that the interaction between an imbalanced charge density and the backbone polymer can be presented by an eigenstress field. The constitutive parameter connecting the eigenstress to the charge density is calculated directly using a single microstructural model for Nafion. The results are applied to predict the response of samples of IPMC, and good correlation with experimental data is obtained. Experiments show that the voltage induced by a sudden imposition of a curvature, it two orders of magnitude less than that required to produce the same curvature. The theory accurately predicts this result. The theory also shows the relative effects of different counter ions, e.g., sodium versus lithium, on the response of the composite to an applied voltage or a curvature.

In this paper, a white-box model of Nafion-Pt composite actuators considering the following physical phenomena is proposed: 1) ionic motion by electric field, 2) water motion by ion-drag, 3) swelling and contraction of the membrane, 4) momentum effect, 5) electrostatic force, and 6) conformation change. Computer simulation showed the following results. 1) The simulated motions agreed with experimental results improving the accuracy in comparison with the conventional models, especially on the time of the maximum displacement. 2) The nonlinear relation between input voltage and the maximum displacement was explained.

The cluster morphology in a water-swollen Nafion perfluorinated membrane is studied using a micromechanics approach. The cluster size is determined from the minimization of the free energy as a function of the equivalent-weight of Nafion, the volume fraction of water, and the temperature, taking into account the electrostatic dipole interaction energy, the elastic polymer chain reorganization energy, and the cluster surface energy, leading to results which are in accord with experimental observations. By minimizing the sum of (1) the electro- elastic interaction energy between an ionic cluster and the fluorocarbon matrix, and (2) the cluster surface energy, it is concluded that the effective cluster shape is spherical in the absence of an electric field, and an oblate spheroid when an electric field is applied. The effect of cluster morphology on the effective electro-elastic moduli and the effective ionic conductivity is then studied by a micromechanical multi-inclusion model. The result seems to describe the available empirical relation when a spherical cluster shape is assumed. It correctly predicts the insulator-to-conductor transition which occurs in Nafion, as the water volume fraction is increased.

Ionic Polymer-Metal Composites (IPMCs) are materials capable of exhibiting large motion sensing and actuation capabilities in an electric field produced by a small voltage. Laboratory observations on the behavior of IPMC in an electric field strongly establish the presence of water movement due to electrophoretic migration of hydrated counter-ions or simply cations. In this paper, the effects of counter-ions on the performance of IPMCs in sensing and actuation are discussed. Samples of IPMCs were carefully prepared in a standard size of 0.25 x 1 inch strip containing various monovalent and divalent metal cations including Na⁺, Li⁺, K⁺, H⁺, Ca⁺⁺, Mg⁺⁺ and Ba⁺⁺. Given a sinusoidal wave input of 1.2 volts with ½ Hz, the IPMC having Li⁺ shows the best performance in terms of force generation. Such results strongly indicate that sulfonate exchange sites are the relatively low charge sites and therefore the hydration process plays a much more important role. It is noted that water absorptivity and the phenomenon of exchange site clustering depend on the type of cations. Furthermore, the experimental results strongly indicate the importance of the hydration process. Muscle performance characteristics are reported and a simple phenomenological model for forces and fluxes is also presented.

To induce bending motion in a perfluorinated polymer electrolyte by electric stimuli in water or saline solution, plating with metal is required. To fabricate electrodes, a perfluorocarboxylic acid membrane was soaked in Au(III) di- chloro phenanthroline complex solution, and then any adsorbed Au(III) cation complex was reduced in aqueous sodium sulfite. Optimizing the motion response depends on control of the chemical plating procedure. By sequential adsorption/reduction cycling, a suitable pair of gold electrodes with a fractal-like structure have been grown. We illustrate the advantage of optimizing the interfacial area between electrode and membrane to enhance deformation response. To achieve this, gold deposits in the film are accumulated by sequential adsorption/reduction plating cycles. Actuator displacement increased with the number of plating gold deposition cycles up to roughly 6 times, but showed no clear improvement beyond. It is believed that with excessive plating, the interfacial area begins to decrease and/or the hardness of the electrode increases, thus countering any improvement in electrical conductance. Displacement rates were proportional to current. This high interfacial area between the electrodes and polymer electrolyte leads to larger deformation. The measured deformation progressively improves with cycling. Its motional response and versatility are illustrated by some examples.

A continuum mechanical model of Nafion based metal-polymer actuators is presented. Global integral postulates are written for the conservation of mass, momentum, energy, and charge, Gauss' law, and the second law of thermodynamics. The global equations are then localized in the volume and on the material surfaces bounding the polymer. A finite element formulation is used to predict the evolution of the counter ion concentration, 'free' water content, electric potential, and stress/strain during actuation. The model includes stress relaxation phenomena due to water flow generated governed by Darcy's law.

Ion-exchange polymer membrane metallic composites (IPMC) are one of the electroactive polymers (EAP) that were shown to have potential application as actuators. The recent introduction of perfluorocarboxylate-gold composite with tetra-n-butylammonium and lithium cations instead of sodium made the most significant improvement of the material's electroactivity. Under less than 3 volts, such IPMC material were shown to induce bending beyond a compete loop. The bending characteristics of IPMC offered an attractive actuation capability for a dust wiper in planetary applications and it was explored for the Nanorover's IR camera window of the MUSES-CN mission. This joint NASA and the Japanese space agency mission, is scheduled to be launched from Kagoshima, Japan, in January 2002, to explore the surface of a small near-Earth asteroid. The application of EAP at space conditions posed a great challenge due to the harsh operating conditions that are expected and the critical need for robustness and durability. Several issues that are critical to the application of IPMC were addressed including operation in vacuum and low temperatures, as well as the effect of the electromechanical characteristics of the IPMC on its actuation capability. Highly efficient IPMC materials, mechanical modeling, unique elements and protective coatings were introduced to enhance the applicability of this EAP material. However, critical issues were identified that hamper the transition of IPMC from being considered for practical applications at this stage.

Electroactive polymers constitute a great family of very different compounds, with diverse properties and applications. They have in common that the modulation of EAP properties is a key requisites in order to make use of these materials for technological purposes. In this contribution we outline some applications of materials based in polypyrrole and describe methods to characterize the polymerization process and the properties of the films. A selected property can be then optimized in order to attain a tailored material for a defined application.

Ionic polymer gels shrink and swell in response to certain environmental stimuli, such as the application of an electric field or a change in the pH level of the surroundings. This ability to achieve large, reversible deformations with no external mechanical loading has generated much interest in the use of these gels as actuators and artificial muscles. This work focuses on developing a means of characterizing the mechanical properties of such ionic gels and describing how these properties evolve as the gel actuates. A thermodynamically consistent finite elastic constitutive model of an active polymer gel is developed to describe this behavior. The mechanical properties of the gel are characterized by a strain-energy function and the model utilizes an evolving internal variable to describe the actuation state. Applications of the mode to poly(vinyl alcohol)-poly (acrylic acid) gels are presented.

Peizoelectric ultrathin composite film comprised of PSS and PDDA was synthesized using the electrostatic self-assembly (ESA) process. The ESA processed PSS/PDDA film is a layer- by-layer laminated structure, which exhibits piezoelectric response directly, with a piezoelectric coefficient d₃₃ = 6.0 pC/N and without poling treatment. It is assumed that the self-assembly process may play a role in molecular alignment resulting in net polarization in the layer-by- layer structured ultrathin film, a process quite different form that used for form conventional piezoelectric films.

Uniaxial and biaxial mechanical tester was developed tp perform basic test for characterization of soft, low strength polymer gels. We have considered stress/strain relationship of acrylamide-based and polyacrylonitrile (PAN) fiber and sheet gels. Acrylamide-based gels were tested uniaxially, where Young's modulus estimated varies between 10 and 25 kPa. Uniaxial and biaxial tension test were performed on PAN sheets, from which Young's modulus was estimated at 6.65 Mpa, which is an extraordinarily large strength than the conventionally investigated acrylamide- based gels. Its length change in response to EtOH/H₂O solution exchange proved to be not small as an actuator material, and it was observed that PAN exhibited a deformation in response to the electric field. Two types of PAN gel fibers were tested as a bundle of 50 fibers. True stress-strain data were obtained showing similar non-linear trend in both case. Statistical methods were used to assess fiber strength distribution.

Composites of monodomain nematic liquid crystal elastomers and a conducting material distributed within their network are shown to exhibit large deformations, i.e. contraction, expansion, bending with strains of over 200% and appreciable force, by Joule heating through electrical activation. The electrical activation of the conducting material induces a rapid Joule heating in the sample leading to a nematic to isotropic phase transition where the elastomer of dimensions 32 mm x 7 mm x 0.4 mm contracted in less than a second. The cooling process, isotropic to nematic transition where the elastomer expands back to its original length, was slow and took 8 seconds. The material studied here is a highly novel liquid crystalline co-elastomer, invented and developed by Heino Finkelmann and co-workers at Albert-Ludwigs-Universitaet in Freiburg, Germany. The material is such that in which the mesogenic units are in both the side chains and the main chains of the elastomer. This co-elastomer was then mechanically loaded to induce a uniaxial network anisotropy before the cross-linking reaction was completed. These samples were then made into a composite with a conducting material such as dispersed silver particles or graphite fibers. The final samples was capable of undergoing more than 200% reversible strain in a few seconds.

In order to gain more insight into basic principles of the nature of polymer hydrogels which are able to execute work by large deformations in electric fields, this study is mainly focused on those gels with a polyacrylamide backbone being very suitable for considerably varying their physicochemical properties simply by specific copolymerization. In the experimental part, the Donnan potential has been registered for the first time in PAAm/PAA gels in varying electric fields and different chemical environments with a new microelectrode technique. The mechanical properties of the gels have been characterized by measurements of swelling ratio, elastic modulus and being in dynamics under various stimuli. In the theoretical part, a model based both on this theory and the measured mechanical parameters, the bending dynamics of a polyelectrolyte gel in an electric field can be evaluated. Numerical simulations employing finite element discretization demonstrate the potential and the validity of the model. A promising correlation between theory and experiment could be shown.

This paper examines the possibility of the Electro-Active Papers (EAPap) as actuators. EAPap was prepared by glueing tow sliver laminated papers in opposite direction so as to constitute electrodes outside. When an electric voltage was applied on the electrodes the EAPap produces bending displacement. The performance of the EAPap is dependent on the glue types, applied voltage and excitation frequency. To investigate the operational principle of the EAPap, some experiments were conducted with different adhesives and host papers, and we believe that it is based on the electrostriction effect associated with a combination of the electrostatic force of electrodes and the intermolecular interaction of the adhesive. Further investigations to improve and stabilize the EAPap properties are necessary and some remarks for future research are provided. Since the EAPap are quite simple to fabricate and lightweight, various fields of them are applicable, i.e., flexible speakers, active sound absorbing materials and smart shape control devices.

We have developed a new driving mechanism to induce deformation and movement of a neutral polymer gels in non- conducting medium. The main idea was to incorporate such finely distributed colloidal particles into a swollen network, which response to electric field. Since the particles can not leave the gel matrix, so that all of the forces acting on the particles are transmitted directly to the polymer chains result in either locomotion or deformation of the gel. Bending of weakly cross-linked poly(dimethylsiloxane) gels containing finally distributed electric field sensitive particles has been studied in silicon oil. Under an external electric field these gels underwent significant and quick bending. Scaling down the geometry may provide a new principle to build soft microelectromechanical actuators.

A novel concept for protection of optical sensor will be described. The device consist of a transparent substrate, a transparent conducting electrode, insulating polymers, and a reflective top electrode layer. Using thin film deposition and photolithographic fabrication techniques commonly available for manufacture of integrated circuits, plus spin coating as commonly used for polymers, the layers can be placed on the substrate and arrays of apertures created with sizes ranging from micrometers to millimeters. Due to the stress gradient between the polymer dielectric and the reflective metal electrodes, the composite thin film structure will open over the aperture area once a 'release layer' is removed by chemical treatment. This is the 'open' condition for the 'eyelid'. By applying a voltage between the transparent conducting the metal electrodes, an electrostatic force is created which closes the 'eyelid'. Upon elimination of the voltage, the stress gradient opens the 'eyelid' again. Preliminary devices have been fabricated and operated up to a frequency of 4kHz and at lifetimes of over 10¹⁰ cycles. The power consumption is extremely low. The potential of this technology for a variety of applications will be discussed.

Artificial muscles typically contrast by a phase-transition. Muscle is thought to contract by a different mechanism - a filament-sliding mechanism in which one set of filaments is driven past another by the action of cyclically rotating cross-bridges. The concept is much like the mechanism of rowing. The evidence, however, is equally consistent with a mechanism in which the filaments themselves contract, much like the condensation of polymers during a phase-transition. Muscle contains three principal polymer types organized neatly into a characteristic framework All three polymers can shorten. The contributions of each filament may be designed to confer versatility, as well as sped and strength, on this biological machine. The principles of natural contraction may be useful in establishing optimal design principles for artificial muscles.

Activated polyacrylonitrile (PAN) fibers, which are suitably annealed, cross-linked and hydrolyzed, are known to contract and elongate when immersed in acidic and alkaline solutions, respectively. The key engineering features of PAN fibers are its capability of changing length more than 100 percent and its comparable strength to human muscle. A new technique that allows one to electrically control the actuation of active PAN fiber bundles is reported here. Increasing the conductivity of PAN fibers by making a composite of them with a conductive medium such as platinum, gold, graphite, carbon nanotubes and fibers by making a composite of them with a conductive medium such as platinum, gold, graphite, carbon nanotubes and conductive polymers such as polyaniline or polypyrrole has allowed for electric activation of PAN fibers when a conductive polyacrylonitrile (C-PAN) fiber bundle is placed in a chemical electrolysis cell as an electrode. A change in pH in the vicinity of C-PAN fiber electrode leads to contraction and expansion of C-PAN fibers depending upon the applied electric field polarity. Typically close to 100 percent change in C-PAN length in a few seconds is observed in a weak electrolyte solution with 10s of VDC power supply. These results indicate a great potential in developing electrically activated C-PAN muscles and linear actuators, as well as integrated pairs of antagonistic muscles and muscle sarcomere and myosin/actin assembly. This technology would be more applicable to realistic situations than that of chemically activated PAN fiber bundles as artificial muscles. These results present an excellent potential for using electrically activated C- PAN as artificial sarcomere and artificial muscle.

The electrochemical characterization of triple-layers formed by a EPA (Electroactive Polymer)/double-sided tape/EPA, like artificial muscles is described. Those muscles were characterized working under constant potential or under constant current. Due to the electrochemical nature of the electrochemomechanical property, muscles working under constant current produce constant movements, consuming increasing energies at decreasing temperatures, decreasing concentrations of electrolytes or trailing increasing masses. Muscles working at constant potential response with a faster movement if the temperature or the concentration of the electrolyte increase, or if the trailed weight decreases. Specific charges and specific energies were determined for every experimental condition.

Nafion-Pt composite (ICPF) is one of the most practical electroactive polymer nearest to applications. In this paper, motion of ICPF was analyzed to design a dust wiper of a visual/IR window of Nanorover of NASA MUSES-CN mission by applying Kanno-Tadokoro simulation model. This is a gray-box model between input and output consisting of 3 stages: an electrical stage, a stress generation stage and a mechanical stage. In the electrical stage, the input is voltage and the output is distributed current through the membrane. In the stress generation stage, the input is the current and the output is internal stress. The mechanical stage is approximated by an elastic body or a viscoelastic body. Many results have shown validity of this model. As a result of analysis, the following were revealed. Strain near the electrode is larger than that at the tip. The actuator shows a rolling-up shape at the edges. The larger the aspect ratio of ICPF is, the larger the displacement is, because this spoils the actuator motion. A crosspiece at the tip prevents ICPF form rolling up and the efficiency is improved. Too long crosspiece disables ICPF form moving with a good performance.

Commercial steerable catheters and catheter prototypes actuated by active materials still present limitations in terms of self-sustaining capability and miniaturization. Specifications for the intravascular catheter we are developing are: bending angle up to 20°, bending stiffness of a few N/m, response time of the order of seconds. Simulations with finite element method (FEM) showed these specifications can be satisfied using a polymer with active strain of 1 percent and elastic modulus E=4.5 GPa and a solid polymer electrolyte (SPE) matrix with E=MPa. The actuator is thought to be made of a composite structure which includes polyaniline fibers, a copper wire electrode and SPE matrix. Its measured characteristics are: active strain 0.2%, active stress 2 MPa, fiber elastic modulus 1.5 GPa, SPE elastic modulus 1-2 MPa. The major problem to realize the catheter is the stiffness of SPE, which has to be considerably augmented. Fiber active strain is below the required value, but it can be increased by proper drive. The production of fibers with a diameter of 10 microns will reduce the response time to the required value.

Mechanical performances of beam-shaped and bridge-shaped conductive polymer actuator in aqueous solution and in solid electrolyte have been measured and analyzed varying polymerization conditions and operating conditions. The optimum thickness of polypyrrole for the best bending performance is about 17-19 μm which has been polymerized at the current density of 5.4 μA/mm² for 120 minutes. For the application of conductive polymer actuator to micropump, silicon bulk micromachining process has been combined with polymer processes. By use of parylene diaphragm and anisotropic etching of silicon, the micropump structure composed of polypyrrole and solid polymer electrolyte has been fabricated successfully.

ERFs are electroactive fluids that experience dramatic changes in rheological properties, in the presence of an electric field. The fluids are made from suspensions of an insulating base fluid and particles on the order of one tenth to one hundred microns in size. In the presence of an electric field, the particles, due to an induced dipole moment, will form chains along the field lines. This induced structure changes the ERFs viscosity, yield stress, and other properties, allowing the ERF to change consistency from that of a liquid to something that is viscoelastic, such as a gel, with response times to changes in electric fields on the order of milliseconds. In this paper the modeling and experimental studies of a novel ERF based haptic interface are presented. Forces applied at a robot end-effector due to a compliant environment are reflected to the remote human operator using this ERF based haptic interface where a change in the system viscosity occurs proportionally to the force to be transmitted. Results of preliminary test are presented where forces, displacements, pressure and temperature data are measured and analyzed.

In this paper, the authors discuss the chemical process of fabricating IPMCs and their variations suitable for applications of fuel cells, electrolysis, and hydrogen sensors. The underlying principle of fabrication of IPMCs is an initial stage of molecular metallization and subsequent surface plating. Characterization results including TEM photographs and physical properties are provided. It has been found that the molecular metallization process is slow due to the complex phenomena related to an increased mass transfer resistance as platinum precipitate and possibly slow kinetics involved in. TEM photographs confirmed 'the cluster-network model' that is convenient to describe mass transfer phenomena within the IPMC.

This paper describes the design and implementation of electric fields to actuate mollusk-shaped robots made entirely of PAMPS gel, which is a kind of electro-active polymer (EAP). The purpose of this study is to develop a system to control the shape of both simulated and real gel robots using electric fields. We present a modeling framework and experimental results using a prototype mollusk-shaped EAP robot that locomotes by changing the shape of its whole body.

We present results from development and testing of lightweight actuators made of the piezoelectric polymer PVDF. The prototype being developed is intended for microgravity applications in space and has been tested aboard NASA's Reduced Gravity Platform. The design has been driven by the requirements for a full 3D environment. Incorporation of additional electrical leads into the actuators themselves may remove the need for a separate umbilical to the suspended experiment. Linear equations describing the displacement of piezoelectric bimorphs were developed and applied to the bellows actuator including the epoxy layer. Properties for the piezoelectric layers were obtained from the literature; properties for the epoxy layer were obtained through ultrasonic testing. To assess the validity of the assumed linearity of the actuator, we conducted nonlinear finite element analysis, which indicated a high degree of linearity on contraction and up to a maximum of 5% deviation on expansion to full deflection (about 6 mm). We have developed and tested a proportional-plus-derivative (PD) control system for use with the actuator in 1D using a novel folded pendulum to simulate a zero-g environment. Passive and active characteristics are both in agreement with theoretical predictions.

We have reported that nonionic gel of ploy(vinyl alcohol) (PVA) swollen with dimethyl sulfoxide (DMSO) responds to an electric field rapidly with a large and reversible deformation, which includes a spherical bending motion to the anode side and a contraction in the direction of an electric field. The electrically induced strain in the polymer gel has ben suggested to be due to electrically induced unidirectional movement of solvent in the gel. The chemically crosslinked polymer gels used here, which had only about 2wt% of polymer content and far much larger amount of solvent in the gel networks, were a good elastic body to suffer a large mechanical deformation. Here, we discussed mechanical properties of the gel under and out of the application of an electric field, and also the interaction between the polymer network and solvent. The electrically induced deformation was discussed, as well, on the proportionality of strain to the square of an electric field for both of the bending motion to the anode side and the contracting motion in the field direction. Furthermore, we drove out the electrically induced solvent force in the gel under various conditions, and demonstrated that the electroactive non-ionic gel can be used in some mechanical devices.

The main goals of this research were to 1) refine manufacturing processes in order to develop novel soft, highly compliant and efficient electroactive materials for 2) subsequent characterization and integration into a prototype autonomous aquatic vehicle as a visible demonstration platform. Therefore several manufacturing processes to develop active polymeric composites were investigated and refined to create robust and efficient artificial muscle fin actuators. In this effort, several polymer materials, geometric shapes and thickness of the fin were investigated. An experimental static bench-test setup was then instrumented to characterize forward thrust force and evaluate efficient input driving signals to the actuator fin. All characterization data were obtained using a laptop PC-platform LabVIEW data acquisition system. A radio- controlled vehicle utilizing the optimized fin propulsors and all the onboard hardware to generate power and control signals was then designated and tested for optimum forward cruising speed and simple steering maneuver. The results showed that the proposed electroactive fin could be a viable candidate for application in low powered autonomous aquatic swimming vehicles.

Polymers of three carbon residues, substituted phosphoglycerides, display physical properties: malability, diffusion coefficients, and phosphoglyceride substitution. Monomers and polymers covalently bound to phospholipids provide unique design elements attractive as limiting boundaries. This experimentation proposes a layering of Poly-glyceryl phosphoryl diglucosyl diglyceride (>50 GPDD unit) polymers, as asingle end-to-end layer of 1,3-GPDD or as more comlex two or three thicknesses of cross-linked 2,2-phosphoglyceride GPDD polymers. Poly-GPDD polymers are controlled in both length and thickness, additional strength, and pro-regulation of diffusional migration and "active" diffusion of small to intermediate MW environmentally meaningful modules. Smart structure control evaluates ultrastructural appearance, molecular shape and immunologic coating with this natural procedure. Shapeliness of different Smart Structrues, controlled with unique phosphoglyceride layering, is an obvious ultrastructural detail. Calculation of smart structure volume and surface area assumes regular spherical (coccal) or cylindrical (bacillar or spirillar) shapes. Structural integrity and limiting layer organization support Smart Structure geometry. Internal ultrastructure of layers is evident by: shape, molecular dimensions, regularity/irregularity, thicknesses, crystallinity, etc. Variation of polymeric: Mw, length, surface, localization, and secondary/tertiery structure, characterize this polymerically integrated system. This integrated structural organization demonstrates GPDD as a geometric building block. Opposing viewpoints rely upon more detailed chemical bonding within these polymers. These proposed experiments will provide understanding of natural smart structures.

Herein we report the design, synthesis, and properties of a novel electromechanical actuator, poly(cyclooctatetrathiophene). This system integrates both a conducting polymer and a (4n)annulene repeat unit. The ability of (4n)annulenes to undergo a conformational change as a function of redox state is well known, and allows poly(cyclooctatetrathiophene) to, in principle, expand and contract via redox-induced changes in the length of the repeating unit. Thus, electromechanical actuation in this system is an intrinsic property of the individual chains, not a bulk property of the material. The ultimate goal is to demonstrate single-molecule electromechanical actuation.

The stringent requirements for a solid polymer electrolyte (SPE) in solid state devices such as batteries or supercapacitors are even more demanding when used in electromechanical actuators. Not only is the SPE expected to exhibit good conductivity, mechanical properties, adhesion and mechanical/electrical stability, but it must also be flexible, maintained good adhesion while flexing, be easily processible and be able to function in air. In this work polyacrylonitrile and Kynar based non-aqueous SPEs and water based polyacrylamide hydrogel ion source/sinks containing various perchlorate salts were tested for their applicability to polypyrrole and carbon nanotube actuators and supercapacitors. The results indicate that the optimum SPE for both polypyrrole and carbon nanotube actuators would be a polyacrylonitrile plasticized with propylene carbonate and ethylene carbonate containing 1.0M NaClO₄. It is also apparent that the same SPE would be the most suitable for supercapacitor applications with these materials.