For many years, EAPs received relatively little attention due to their limited actuation capability and the small number of available materials. In the last ten years, new EAP materials have emerged that exhibit large displacement response to electrical stimulation and they are enabling great potentials for the field. EAP are very attractive for their operational similarity to biological muscles, particularly their resilience, damage tolerant, and ability to induce large actuation strains. The application of these materials as actuators to drive various manipulation, mobility and robotic devices involves multidiscipline including materials, chemistry, electro-mechanics, computers, electronics, etc. Even though the force actuation of existing EAP materials and their robustness require further improvement, there has already been a series of reported successes. The successful devices that were reported include miniature manipulation devices including catheter reported successes. The successful devices that were reported include miniature manipulation devices including catheter steering element, miniature manipulator, dust-wiper, miniature robotic arm, grippers and others. Some of the currently considered applications may be difficult to accomplish and it is important to scope the requirements to the level that current materials can address. Using EAP to replace existing actuators may be a difficult challenge and therefore it is highly desirable to identify a niche application where it would not need to compete with existing capabilities. This paper will review the current efforts and the expectations for the future.

Muscles fulfill several functions within an animal's body. During locomotion they propel and control the limbs in unstructured environments. Therefore, the functional workspace of muscle needs to be represented by variables describing energy management (i.e. power output, efficiency) as well as control aspects (i.e. stiffness, damping). Muscles in the animal kingdom vary greatly with respect to those variables. To study if ElectroActive Polymer's (EAP) can be considered as artificial muscles we are making a direct comparison between the contractile properties of EAP's and biological muscle. We have measured the functional workspace of EAP actuators using the same setup and techniques that we use to test biological muscle. We evaluated the properties of three different EAP materials; the acrylic and silicone dielectric elastomers developed at SRI International and the high-energy electron-irradiated co-polymers (p(VDF-TrFE)) developed at the MRL laboratory at Penn State University. Initial results indicate that the EAP materials partly capture the functional workspace of natural muscle and sometimes even exceed the capabilities of muscle. Based on the data we have collected it seems that both EAP technologies have characteristics that could qualify them as artificial muscles.

The promise of Electroactive Polymers (EAP) and associated muscle technologies lies beyond their use as simply an alternative actuation system. Because of their soft nature, both physically and systemically, a new range of robotic designs can be addressed, including those that more closely resemble designs found in nature. Conceptually simplest is the exploitation of the inherent spring and damping characteristics of muscle actuators. By tuning the characteristics of the actuator, it may be possible to build more functionally flexible systems that are at the same time more robust and stable. More ambitiously, EAP could be coupled with techniques in rapid prototyping, novel control methods, and genetic algorithm system design to create a new class of highly integrated robots that are more efficient in their design time, resource requirements, and operational characteristics. These ideas may have particular relevance for the creation of micro-robots, a possible design of which is proposed.

Nafion-platinum composite (IPMC or ICPF) is one of the electro-active polymer actuators nearest to real applications. This paper introduces development of some actuation devices using IPMC. A distributed actuation device has a number of EFD (Elliptic Friction Drive) elements that give planar motoin with two degrees of freedom by 2 IPMC actuators. Coordinated motion of EFDs realizes robustness of drive. A soft micromanipulator with three degrees of freedom is a parallel mechanism having 4 actuator parts enabling motion in x, y and z directions. A face actuation device is a sheet that changes its shape arbitrarily by applying electric stimuli to its grid electrode structure. In order to develop the mechanical structures and the control strategies for those applications, appropriate models are essential. It introduces a gray-box model practical for the design purpose.

The demand for actuators featuring biomimetic properties such as direct drive, high power density and intrinsic compliance is growing in robotics and bioengineering. Our work is aimed to increase the performance of a class of actuators utilizing active polymer components which are characterized under several different electrical stimulation conditions. In order to increase the active strain of the system we have considered a configuration inspired to McKibben muscle. In this configuration each active element is covered by a braid mesh shell (made with flexible, but not extensible, threads), which contracts when the element increases its volume. This technical solution amplifies the strain up to 50 times and can be utilized to reach tangible shortening of the actuator.

Many conjugated polymers show an appreciable difference in volume between their oxidized and reduced forms. This property can be utilized in soft electrochemically driven actuators, "artificial muscles". Several geometries have been proposed for the conversion of the volume expansion into useful mechanical work. In a particularly simple geometry, the length change of polymer strips is exploited. The polymer strips are connected to the driving circuit at the end of the strip that is attached to the support of the device. The other end of the strip is connected to the load. The advantage of this set-up is simplicity and that the maximum force generated in the polymer can be transferred directly to the load. There is, however, an inherent problem in this design that will be examined in this paper. If the potential of the reduced state is below that for oxygen reduction, only a finite length of the free-standing film will be fully reduced. This is due to the reduction of oxygen at the surface of the polymer competing with the reduction of the polymer. For a long strip, the potential will therefore approach the reduction potential of oxygen. This will lower the efficiency of the artificial muscles and complicate measurements on free-standing films. A model of the potential profile in a free-standing strip is derived. It is found that the active length (the length with a given potential change) of the polymer will scale as &sqrt;dσ/i_d. (d is the thickness, σ the conductivity of the film, and id the diffusion limited current density for oxygen reduction). The active length is typically of the order of millimeters. The model is compared with measurements on a strip of polypyrrole doped with dodecylbenzene sulfonate.

The mesoscopic morphology of wet-spun polyaniline fibers determines their mechanical strength. Macrovoid formation in the coagulation bath is responsible for poor mechanical properties of these fibers. The effects of polymer concentration, coagulation bath temperature, polymer molecular weight and coagulant on the morphology of wet-spun polyaniline fibers have been investigated. The fibers were spun from concentrated solutions of low/medium and medium molecular weight emeraldine base dissolved in N-methyl-2- pyrrolidinone containing heptamethyleneimine as a gel inhibitor. The impact of the fiber morphology on the mechanical properties of the fibers prepared under different conditions is studied. A wet-spinning method, which minimizes macrovoid formation in the polyaniline fiber, is reported, and consequently the strength of the unstretched polyaniline fibers increased dramatically.

We reported the characterization of a macroscopic electrochemomechanical actuator like triple layer (3x1 cm) formed by polypyrrole)/double- sided, non-conducting and flexible tape/ polypyrrole that works in liquid electrolytes under electrochemical control. This triple layer has characteristics of artificial muscle. The influence of variables that control the volume change in the polymer as electrolyte concentration, or temperature has been studied. Variations of time, energy and charge under different conditions are described. We have found that the triple layer acts, at the same time, as sensor and actuator. Therefore, physical magnitudes like the electrolyte concentration or the temperature in the cell can be obtained from electrical energy consumed by a muscle. We have evaluated the influence of variables as area of the triple layer or the trailing weight, which don't participate in the electrochemical reaction. We propose an explication to the results, which show a correlation between the trailed mass and the consumed charge required to move a constant angle those masses by the triple layer. When different surface areas of the triple layer has been evaluated we found that the consumed electrical charge is proportional to area (the mass) of the triple layer. The triple layer can make macroscopical movements in short times, their position is absolutely controlled with the electrical charge, and it has capacity to lift masses. These characteristics allow their use in the design of tools. So, we present a macroscopic tool constituted by two triple layers, which allows catch and translate objects in liquid medium (nipper).

Conducting polymers such as polypyrrole (PPy) doped with large anionic detergents have high stability in aqueous systems. PPy can be reversibly oxidised and reduced electrochemically. The redox change of PPy is accompanied by a change in volume of the polymer. This is partly ascribed to take-up of ions and solvent molecules. This volume change can be used as a polymer actuator (artificial muscle) working in a narrow voltage range (less than 1 V). The properties of the PPy polymer are largely determined by the dopant ions and also by the deposition conditions and the substrate. A free-standing 10 micrometers thick film is prepared electrochemically at a constant current from an aqueous solution of pyrrole and sodium alkylbenzene sulfonate. The mechanical properties of the film (tensile strength and Young's modulus) and the reversible linear elongation between the oxidised and reduced states are measured. Alkylbenzene sulfonates with alkyl chain lengths between 1 and 22 carbon atoms are used as dopant anion. The films made with the different anions have highly different properties and are here compared to outline the influence of the size of the anion. A maximum in linear elongation is found for p-(n-octyl)benzene sulfonate and in conductivity for p-(n-butyl)benzene sulfonate.

In our earlier work, we have demonstrated that the high- energy electron irradiation modifies (VDF-TrFE) copolymers from a normal ferroelectric to a relaxor ferroelectric with high electromechanical response. Here, we present two approaches we are taking recently. One is to explore the non-irradiation approach to modify the PVDF-based material to achieve high electromechanical response. A ter-monomer (HFP and CTFE are used here) with a relative large size is added to the copolymer to act as modifiers. The electromechanical and dielectric properties in the terpolymers seem to be similar to those in irradiated copolymers. The other approach addresses the fundamental issue of the low dielectric constant in the currently available electroactive polymers. By making use of composite approach and ultra-high dielectric constant in CuPc, a polymeric composite with very high dielectric constant but the elastic modulus similar to polymer has been demonstrated. The preliminary results indicate that the polymer composite has the potential to generate high strain under much lower field. In parallel to the material development, we investigated device performance based on the irradiated copolymers. The performance of irradiated copolymer multilayers with a thickness up to 1 mm was characterized. The design and device performance of a flextensional actuator fabricated from the irradiated copolymer multiplayer are presented. The flextensional actuator, whose resonance frequency is at a frequency of a few kHz to more than 10 kHz, exhibits more than 1 mm displacement and high force output, which are attractive for many applications.

This paper discusses a new ferroelectric polymer with high dielectric constant (>50 at 1K-1M Hz) and large electrostrictive response (~5%) at ambient temperature, which is based on a processable semicrystalline terpolymer comprising vinylidene difluoride (VDF), trifluoroethylene (TrFE), and chlorotrifluoroethylene (CTFE). This VDF/TrFE/CTFE terpolymer was prepared by a combination of a borane/oxygen initiator and bulk polymerization process at ambient temperature. The control of monomer addition afforts the terpolymers with high molecular weight and relatively narrow molecular weight and composition distributions. The incorporated bulky CTFE units homogeneously distributed along the polymer chain seem to reduce the thickness of ferroelectric crystalline domains without destroying the overall crystallinity. This nano-size semicrystalline morphology results in the reduction of ferroelectric-paraelectric (F-P) phase transition to near ambient temperature with a very small energy barrier. Some terpolymers exhibited common ferroelectric relaxor behaviors with a broad dielectric peak that shifted toward higher temperatures as the frequency increased, and a slim polarization hysteresis loop at near the dielectric peak (around ambient temperature) that gradually evolved into a normal ferroelectric polarization hysteresis loop with reduced temperature.

Previous studies have shown that copolymers of vinylidene fluoride (VDF) and hexafluoropropylene (HFP) can exhibit large electrostrictive strains depending on sample history and copolymer composition. In an earlier study, random copolymers containing 5%HFP/ 95% VDF and 15%HFP/85%VDF were investigated. In this study, we used random copolymers of poly(VDF/TrFE) (68/32) mol% and poly(VDF/HFP) (95/5) mol% to prepare films by solution blending the two copolymers in different weight percents. Films were prepared using a two step process. First, we prepared solvent cast films of the blends using dimethylformamide (DMF) as the solvent at room temperature and then melt-pressed and quenched the films into ice water. Gold electrodes were deposited on opposing sides of the films by sputtering. We measured the electrostrictive properties as a function of electric field.

A new type of ferroelectric polymer produced by melt blending ~1 micrometers powder particles of poly (vinylidene fluoride) (PVDF) and nylon 11 exhibited several enhanced properties compared to the homopolymers. One of the most significant changes previously observed was in the polarization as a function of composition which exhibited a maximum at the 50/50 level by weight. In this study, we report the enhanced high temperature stability of the polarized PVDF crystals imparted by the presence of ~20% nylon 11 in uniaxially stretched films. This is in contrast to the large loss in polarization and piezoelectric properties observed to occur in uniaxially oriented, Phase I, PVDF films. The powder blend films exhibited almost no loss in piezoelectric response after annealing at 160 degree(s)C for two hours while PVDF films exhibited more than an 80% loss in d31 after the same annealing treatment: similar decreases in e31 were also observed. Both the glass transition temperature and melting point of nylon 11 were observed to decrease with increasing PVDF content, indicating the presence of interactions between these two polar polymers.

Micromachined unimorph actuators based on the electrostrictive P(VDF-TrFE) copolymer have been fabricated. The performance of the devices has been modeled and characterized. The experimental results on the device responses are very close to the prediction of the model, indicating a high actuator displacement and voltage sensitivity. For a typical unimorph device with 1 mm length, the displacement at the center of the device can reach 30 micrometers , and the ratio of the displacement/applied voltage is more than 30nm/V. Furthermore, over more than 3 frequency decades, the dispersion of the displacement is less than 20%, which indicates the high frequency capability of this polymer based MEMS. To demonstrate the high force capability of the device, the displacement response of the device was evaluated at 200 Hz ina fluid medium and there is no observable change in the displacement response in fluid medium when compared with that measured in air. Due to the large field induced electrostrictive strain and high frequency capability of the electrostrictive P(VDF-TfFE), the device is capable of operating at no-resonance model with high displacement and force output, and over a broad frequency range (DC to >10 kHz). The observed performance of the device indicates that this type of electrostrictive P(VDF-TrFE) based MEMS is attractive for micro-pump, values, and air coupled ultrasonic transducer array, etc.

Polyacrylate dielectric elastomers have yielded extremely large strain and elastic energy density suggesting that they are useful for many actuator applications. A thorough understanding of the physics underlying the mechanism of the observed response to an electric field can help develop improved actuators. The response is believed to be due to Maxwell stress, a second order dependence of the stress upon applied electric field. Based on this supposition, an equation relating the applied voltage to the measured force from an actuator was derived. Experimental data fit with the expected behavior, though there are discrepancies. Further analysis suggests that these arise mostly from imperfect manufacture of the actuators, though there is a small contribution from an explicitly electrostrictive behavior of the acrylic adhesive. Measurements of the dielectric constant of stretched polymer reveal that the dielectric constant drops, when the polymer is strained, indicating the existence of a small electrostrictive effect. Finally, measurements of the electric breakdown field were made. These also show a dependence upon the strain. In the unstrained state the breakdown field is 20 MV/m, which grows to 218MV/m at 500% x 500% strain. This large increase could prove to be of importance in actuator design.

Dielectric elastomers have shown great promise as actuator materials. Their advantages in converting mechanical to electrical energy in a generator mode are less well known. If a low voltage charge is placed on a stretched elastomer prior to contraction, the contraction works against the electrostatic field pressure and raises the voltage of the charge, thus generating electrical energy. This paper discusses the fundamentals of dielectric elastomer generators, experimental verification of the phenomenon, practical issues, and potential applications. Acrylic elastomers have demonstrated an estimated 0.4 J/g specific energy density, greater than that of piezoelectric materials. Much higher energy densities, over 1 J/g, are predicted. Conversion efficiency can also be high, theoretically up to 80-90%; the paper discusses the operating conditions and materials required for high efficiency. Practical considerations may limit the specific outputs and efficiencies of dielectric elastomeric generators, tradeoffs between electronics and generator material performance are discussed. Lastly, the paper describes work on potential applications such as an ongoing effort to develop a boot generator based on dielectric elastomers, as well as other applications such as conventional power generators, backpack generators, and wave power applications.

Elastomer films sandwiched between compliant electrodes work as electrostatic actuators when a large electric field is applied over the electrodes. We have analyzed the mechanical and electrical response of actuators to a sinusoidal varying driving voltage. The actuator acts as a capacitor in the electric circuit, but due to very high strains, the capacitance changes during a work cycle. The extension of the actuator is electrostrictive in response, hence it depends on the square of the applied field and oscillates with twice the driving frequency. The response is non-linear. This change in dimension is coupled back into the electric circuit through the capacitance of the film and the current oscillates with the first, third and odd higher-order harmonics. Due to this coupling, measurements of the current allows one to determine the expansion of the actuator, and hence to control the actuator.

It is now well recognized that a strip of ionic polymer- metal composite (IPMC) exhibits a spontaneous bending capability under the influence of an electric potential. A key observation is the appearance and disappearance of water on the expansion and contraction surfaces of the strip, respectively. Such water appearing/disappearing activities occur near the permeable metal electrodes. The imposition of en elctric field causes the mobile cations that are conjugated to the polymeric anions to undergo electrophoretic dynamic migration that can result in local deformation of the material. Such an electrophoretic behavior of the IPMC causes the water to leak out of the permeable electroded boundary so as to lower the actuation performance. This situation is similar to a leaking hydraulic actuator (hydraulic jack), which has the highest force density notwithstanding the compressor unit weight. Herein, a new category of actuators as ionic polymeric hydraulic actuators (IPHA's) is defined. The IPMC is a good example of such ionic polymeric hydraulic actuators. The advantage of ionic polymeric hydraulic actuators is their potential to generate substantially high force densities, theoretically better than current hydraulic actuators. Based upon this ionic polymer hydraulic actuator concept, a certain manufacturing technique was developed to increase the force density of the conventional IPMC's by a factor of two (100% improvement in force). This technology and associated experimental results are presented in this paper.

Described is a novel fabrication process of manufacturing ionic polymeric metal composites (IPMC's) biomimetic sensors, actuators and artificial muscles equipped with physically loaded and interlocked (PLI) electrodes. The underlying principle of processing this novel PLI-IPMC's is to first physically load a conductive primary powder into the ionic polymer network forming a dispersed particulate layer. This primary layer functions as a major conductive medium. Subsequently, this primary layer of dispersed particles of a conductive material is interlocked within the polymer network with smaller secondary particles via chemical plating, which used reducing agents to load another phase of conductive particles within the first layer. In turn, both primary and secondary particles can be secured within the ionic polymer network and reduce the potential intrinsic contact resistances between large primary particles. Furthermore, electroplating can be applied to integrate the entire primary and secondary conductive phases and serve as another effective interlocking electrode. In this paper we describe the details of this newly developed technique to efficiently produce a PLI-IPMC loaded with spherical silver particles (D₁₀<0.8 micrometers , D₅₀<1.5 micrometers , D₉₀<2.5 micrometers ; A_sur<6 m²/g) and subsequently interlocked by palladium (D_p~50nm, via a chemical reducing process). It has been observed that such a PLI-IPMC is quite comparable in performance with the traditional Platinum loaded and Gold electro-plated IPMC's but enjoys a much smaller manufacturing cost. Yet it produces a low surface resistivity (less than 1 (Omega) /square) which is highly desirable in creating more uniform deformation.

In this paper first we address experimental works to investigate basic characteristics of IPMC actuators which have not been discussed sufficiently yet. Surface conductivity, displacement and force features are discussed. Also a new actuator is proposed called Artificial Musclelike Linear Actuator (AMuLA) inspired from the actuation principles of the human. The actuator is a linear actuator simulating the mechanical behavior of myofilaments that are the basic units of the human muscle. Multiple IPMC's and electrodes are utilized to mimic the motion of muscles and as a result, musclelike linear motions can be realized. The prototype of AMuLA is introduced and its performance is evaluated.

In this work the synthesis of nano-scaled platinum particles by a chemical reducing technique within an ion-exchange membrane has been performed. It is desirable to gain a fundamental knowledge and understanding of the properties of small nano-scaled platinum particles within ion-exchange membranes, which can affect the performance of Ionic Polymer-Metal Composite (IPMC) artificial muscles. In IPMC artificial muscle applications, the finite size of platinum particles is believed to strongly influence their properties. This might be related to a platinum surface effect originating from the electronic surface states of platinum particles that differ from the bulk states. In order to address this issue, we have attempted to synthesize small platinum particles having different size distributions by using protective agents. Further, we have characterized them as well. For IPMC artificial muscles, the presence of such nano-scale platinum particles minimizes the solvent- leakage from the surface electrodes. This in turn improves their performance dramatically. A successfully fabricated IPMC artificial muscle with nano-Platinum particles has shown a significantly improved force density as much as 100% than that of the conventional IPMC.

The electromechanical actuation performance of carbon nanotube mats, polypyrrole films and hybrid nanotube-polypryrrole materials has been compared. The hybrid materials were formed by coating nanotube mats with polypyrrole using vapour deposition and electropolymerisation techniques. When the coating time was short, the hybrid materials showed the electrochemical responses typical of polypyrrole and retained the porous structure of the nanotube mats. The actuator response of the different materials was determined isotonically at different applied loads. The nanotube mat and hybrid materials gave actuator strains that were largely insensitive to the applied stress up to ~ 10 MPa. The hybrid materials were virtually identical to the uncoated nanotube mats in terms of actuator performance. A simple model showed that the actuator strain depends upon the difference in elastic modulus of the actuator material in the doped and undoped states.

A variety of microfabrication techniques have been developed at the University of Pisa. They are based either on pressure or piston actuated microsyringes or modified ink-jet printers. This work present the results of a study aimed at fabricating carbon nanotube (NT) actuators using micro-syringes. In order to prevent the nanotubes from aggregating into clumps, they were enclosed in a partially cross-linked polyvinylalcohol - polyallylamine matrix. After sonication the solution remained homogenously dispersed for about 40 minutes, which was sufficient time for deposition. Small strips of NT, about 5 mm across and 15 mm long were deposited. Following deposition, the films were baked at 80 degree(s)C and their thickness, impedance and mechanical resistance measured. The results indicate that 50 minutes of baking time is sufficient to give a constant resistivity of 1.12 x 10^-2 (Omega) m per layer similar to a typical semiconductor, and each layer has a thickness of about 6 micrometers .

Amine-epoxy based gel actuators have been made since this chemistry allows the small volume gels to be made easily and is expected to provide enough strength for practical use with highly crosslinked networks. In this study, a small drop of cationic polyelectrolyte gel was prepared by crosslinking of trifunctional polyetheramines with ethylene glycol diglycidyl ether. The response of these materials to electrical stimuli, pH and metal ions is controlled by the crosslink density and ionic strength of medium. When the gels contact a platinum anode, positive charges are generated on the amine groups and the ionic repulsion causes the swelling. Reversing current neutralizes amines and the hydrogen bonding interaction causes a volume collapse. These gels show large and rapid swelling in response to an electrical and chemical input on a sub-millimeter scale.

All commercially available (as-received) perfluorinated ion- exchange membranes are in the form of hydrolyzed polymers and are semi-crystalline containing ionic clusters. Their typical thickness is in the range of approximately 100-300 micrometer. Such a thin thickness of commercially available membrane permits fast mass transfer for use in various chemical processes. Although ionic polymer-metal composite (IPMC) artificial muscles made with these ion-exchange membranes have shown a great potential to produce large displacements and high force densities (maximum force greater than 40 times of its own weight), achieving large forces to be utilized in many practical devices requires manufacturing and fabrication of three dimensional electroactive materials. Knowing that such as-received semi-crystalline membranes are not melt-processable, they are not suitable for the fabrication of 3D electroactive materials or other composite forms. In this work, the authors report a newly developed fabrication method that can scale-up the IPMC artificial muscles in a strip size of milli-to-centi-meter thickness. We have adopted a recently developed technique by Moor et al. For dissolving as- received ion-exchange membranes in appropriate solvents. By carefully evaporating solvents out of the solution, recasted ion-exchange membranes were obtained. The test results showed that a successfully fabricated IPMC strip in a size of 2 mm thickness, 5-mm width, and 15-mm length, produces generative forces (tip forces) more than 20 g-force up to approximately a half centimeter-displacement under a small voltage.

Ordered liquid crystal elastomer films exhibit anisotropic deformations on macroscopic length scales on changing the orientational order of the liquid crystal group by external stimuli such as temperature and electric field. We have developed laterally attached side-chain nematic elastomers with mechanical properties approaching stress, strain and time scale of skeletal muscle activation. The mechanical and structural characterization has led to the ability to improve desired physical properties such as backbone extension and coupling between the backbone and liquid crystal side chain. We have studied the effect of the coupling length on the change in the conformational entropy of the backbone and the viscoelastic behavior. In this paper we discuss the results of our stress relaxation tests.

A fast (0.8sec), large (>10%) and reversible deformation of Poly(vinyl alcohol) gel (PVA) swollen with dimethyl sulfoxide (DMSO) upon electric field was realized, and the maximum observed strain reached quite high 27% (DP2100). St-PVA gels were found to exhibit more stable and reversible deformation than at-PVA gels. Furthermore, we have studied the macroscopic structure of PVA/DMSO gels and its influence on their strain exhibition. Four differently structured PVA/DMSO gels, monolayer, circular, triple-layered and porous, were prepared. Monolayer gel exhibited the highly reproducible strain behavior. The mechanism of electric actuation of PVA/DMSO gel is proposed. Then a design of gel mechanical switch is shown, which exhibited the fast response to the electric field with a large, stable and reversible stretching deformation.

Electric-, and magnetic field sensitive polymer gels are soft smart materials whose elastic and thermodynamic properties are strong function of the field strength imposed upon them. Since electric and magnetic fields are convenient stimuli from the point of signal control, therefore it is of great importance to develop and study such gel systems. In the first part of this paper we introduce a new concept to classify responsive polymer gels. Then it is followed by the discussion of a new driving mechanism which was discovered to induce deformation and movement of neutral polymer gels in non-conducting medium. Bending of weakly crosslinked poly(dimethyl siloxane) gels containing finely distributed TiO₂ particles as well as colloidal iron particles has been studied in silicon oil. Under electric field these gels undergo a significant and quick deformation.

Polyacrylamide hydrogels containing bis-[4- {dimethylamine}phenyl]{4-vinyl-phenyl}methyl leucohydroxide which is so called vinyl derivative of Malachite Green have been studied as color changeable gels. The response times of the color and the volume changes of the gel were measured under 6 and 2 different stimuli, respectively. We found a way to increase their color change speed upon applied electric current (E-current), and designed a gel actuator using Nafion film as a separator between two compartments and as a cation conductor. In addition acrylamide gel swollen with Na₂SO₄ solution was used as a medium for increasing electric conductivity. We varied the concentration of dvMG in the gel to control the degree of color change. Furthermore, we have studied the influence of gel thickness on the color change rate. In light of the results obtained, we have proposed one device consisting of this color changeable gel.

In this paper, electrolyte polymer gels, consisting of a polymer network with ionizable groups and a liquid phase with mobile ions, are investigated. For these gels, we present a volume- and surface-coupled multi-field problem involving chemo-electro-mechanics. First, we derive a convection-diffusion equation for the ion concentrations inside and outside the gel as well as a Laplace equation for the electric field. Second, an equation of motion in order to simulate the unsteady swelling-behavior of the gels, is presented. For the chemo-electro-mechanical coupling, the equations as well as the solution scheme, are given. For the numerical simulation, unconditionally stable, higher order accurate, conservative and implicit space-time finite elements with interpolations - continuous in space and discontinuous in time - are used. We investigate the anionic and the cationic ion concentrations for a given fixed number of bound anionic groups as well as the electric potential inside and outside the gel at a given electric field. The resulting increase in the Donnan potential difference on the anode side of the gel, which represents the higher swelling rate, is in good agreement with experimental results. This shows the validity and the potential of the model.

The electrochemically stimulated conformational relaxation model (ESCR) allows a good description of the chronoamperometric responses of polyaniline in acetonitrile solutions under relaxation control. Compaction, relaxation and diffusion controlled oxidation with penetration of counterions and increase of volume can be defined theoretically. Those three components include structural (macromolecular) aspects and electrochemical descriptions. The model is self-consistent: the same theoretical equation allows to simulate the influence of the different variables on the experimental results.

In this paper, we present a meshless Finite Cloud Method (FCM) for the solution of time-dependent partial differential equations governing ionic gel swelling. Using a point distribution, FCM constructs interpolation functions without assuming any connectivity between points. A collocation approach enforces the unknowns at every point to satisfy either the governing equation of the boundary conditions. To validate the model, a cylindrical hydrogel was fabricated and subjected to step changes in solution pH to characterize the hydrogel's dynamic behavior. The hydrogel's equilibrium behavior was matched using a thermodynamic model. Numerical results show good agreement with experimental data.

We present a multi-scale approach to modeling the electro-mechanical behavior of ionic polymers. We start with a detailed elasto-electro-chemical model which allows for finite deformation. We reduce it to one space dimension appropriate for the commonly used sheet configuration, and demonstrate that steady state solutions display an important boundary layer effect. We conclude with a macroscopic model of a strip of ionic-polymer-metal-composite.

Many physical models of ionic polymer have been developed. However, these models are not suitable for use in the design of control systems for Ionic Polymer-Metal Composite(IPMC) actuators. In this paper an empirical model of IPMC is developed and used for closed-loop control. The empirical model is developed by measuring the step response of 20mm x 10mm IPMC actuator in a cantilever configuration . Using this empirical model, a compensator was designed using a linear observer-estimator in state space. Since the IPMC has a slow time constant, it cannot be used to actuate high frequency signals. The design objectives were to constrain the control voltage to less than 2 Volts and minimize the settling time by using feedback control. The controller was designed using Linear Quadratic Regulator(LQR) techniques which reduced the number of design parameters to one variable. This LQR parameter was varied and simulations were performed which showed settling time of 0.15 seconds for closed-loop as compared to a open-loop settling time of 7 seconds. The maximum control input varied from 1.1 Volts to 2.5 Volts for the simulations depending on the LQR parameter. The controller was later used in experimentation to check simulations. Results obtained were consistent to a high degree. Closed-loop settling time was observed to be 0.95 seconds and the maximum control input was less than 2.3 Volts. Experimentation also revealed a high overshoot and oscillations before settling which occurred due to the excitation of IPMC at its natural frequency. Thus, need to include the higher frequency dynamics was highlighted.

Behaviors of nafion-based actuators are significantly affected by interfacial area between electrode and polymer electrolyte. Replication method was utilized to manufacture a large surface-area composite actuator. Etched aluminum foil was used as a template for replication using liquid nafion solution. Measurement of double layer charging and scanning electron microscopy indicated that interfacial area was greatly increased by replication method. Higher surface area induced a better bending performance of ionic polymer metal composite (IPMC). In parallel, the effect of cations on IPMC was interpreted with constant current experiment, linear sweep voltammetry and electrochemical impedance spectroscopy. For univalent cations, ion size is the most influencing parameter on ionic mobility inside membrane. However, ion-ion interaction affects an ionic mobility for divalent cations.

A nature loves symmetry it is quite logical to think that, X-rays may also exhibit the reverse of Compton effect. Such new modified scattering from low-density polyethylene (LDPE) and polyethylene terepthalate has been observed. The Compton scattered ejected electrons collide with other incident photons before reaching the continuum state transferring a part or whole of its kinetic energy to the photons; thereby producing photons of shorter wavelength called anti-Compton effect. In Quantum theory, external fields (if it changes rapidly) can cause transition from a state of positive energy to negative energy. The lifetime of the excited state is inversely proportional to square of the average atomic number. Hence solid polymers are the ideal system to observe anti-Compton scattering, since binding energy is less. Initial state wave function (psi) _i was calculated by LDPE by extended Huckel-LCAO-MO theory. Final state wave function (psi) _f was formulated and differential cross section was expressed in terms of the profile function J(z) using impulse approximation (IA). This scattering cross section was compared with quantum electrodynamics scattering cross section i.e. Klein-Nishina scattering cross section to solve J(z). The anti-Compton wavelength shift was calculated using relativistic corrections in the IA, hence the valence electron contribution terms z = -P_ocos(phi) , where (phi) is the angle between the electrons initial momentum and the x-ray vector. The anti-Compton profile for the LDPE was obtained from z ~ J(z) graph. The volume plasmon excitation energy was experimentally found out to be 12 eV.

Electroactive polymers (EAP) are an emerging class of actuation materials. Their large electrically induced strains (longitudinal or bending), low density, mechanical flexibility, and ease of processing offer advantages over traditional electroactive materials. However, before the benefits of these materials can be exploited, their electrical and mechanical behavior must be properly quantified. Two general types of EAP can be identified. The first class is ionic EAP, which requires relatively low voltages (<10V) to achieve large bending deflections. This class usually needs to be hydrated and electrochemical reactions may occur. The second class is Electronic-EAP and it involves piezoelectric, electrostrictive and/or Maxwell stresses. These materials can require large electric fields (>100MV/m) to achieve longitudinal deformations at the range from 4 - 360%. Some of the difficulties in characterizing EAP include: nonlinear properties, large compliance (large mismatch with metal electrodes), non-homogeneity (resulting from processing) and hysteresis. To support the need for reliable data, the authors are developing characterization techniques to quantify the electroactive responses and material properties of EAP materials. The emphasis of the current study is on addressing electromechanical issues related to the ion-exchange type EAP also known as IPMC. The analysis, experiments and test results are discussed in this paper.

Direct effects of electrical currents on polyelectrolyte gels are always associated with changes in their Donnan potential. Thus electrical stimulation of gels can be only completely understood if the direct effect of electric fields on the potential profile within the gels are known. The purpose of this study is to present recordings of Donnan potentials in electroactive gels of various compositions, especially under the influence of electric fields. An important finding is that opposite alterations in the Donnan potential simultaneously occur at the current inflow and outflow region of the gel. In anionic gels hyperpolarization, i.e. higher negativity, is induced on the anode-side of the gel, whereas depolarization is found on the cathode-side. As these shifts in the potential are supposed to affect swelling or deswelling of polyelectrolyte gels, they will primarily promote bending motions of the gel. To demonstrate the opposite bending behavior of anionic and cationic polymer gels under the influence of an electric field a short video sequence of an EAP gripper in action is presented. It is made exclusively of polyelectrolyte gel strips taking advantage of the fact that anionic and cationic polyacrylamide gels can be attached firmly to each other without any adhesive.

Dielectric elastomer actuators, based on the field-induced deformation of elastomeric polymers with compliant electrodes, can produce a large strain response, combined with a fast response time and high electromechanical efficiency. This unique performance, combined with other factors such as low cost, suggests many potential applications, a wide range of which are under investigation. Applications that effectively exploit the properties of dielectric elastomers include artificial muscle actuators for robots; low-cost, lightweight linear actuators; solid- state optical devices; diaphragm actuators for pumps and smart skins; acoustic actuators; and rotary motors. Issues that may ultimately determine the success or failure of the actuation technology for specific applications include the durability of the actuator, the performance of the actuator under load, operating voltage and power requirements, and electronic driving circuitry, to name a few.

Electroactive polymer artificial muscles (EAP) can be used to mimic human muscles. In an attempt to exploit these properties we are developing in our laboratory a human-like android unit able to replicate human facial expressions. The android is equipped with linear actuators and is made up of a multisensing acquisition system able to assess rheological and organoleptic properties of food. After the data analysis, the android looks like a man who tastes similar substances. It develops expressions mimicking human responses to the same foodstuff. In this paper we will present the design and relevant features of the artificial muscles and the performance of the android. Human anatomy and mechanical studies were needed to construct the carbon fiber composite holding structure. Location and electromechanical characteristics of EAP actuators were investigated. The system holds sensors, artificial skin and actuators to obtain suitable expressions, implementing the chewing phase, performed by a dedicated actuator, from the expressive phase achieved through multiactuator synergistic drive.

There is increasing realization that some tasks can be performed significantly better by humans than robots but, due to associated hazards, distance, etc., only a robot can be employed. Telemedicine is one area where remotely controlled robots can have a major impact by providing urgent care at remote sites. In recent years, remotely controlled robotics has been greatly advanced and the NASA Johnson Space Center's robotic astronaut, Robonaut, is one such example. Unfortunately, due to the unavailability of force and tactile feedback the operator must determine the required action by visually examining the remote site and therefore limiting the tasks that Robonaut can perform. There is a great need for dexterous, fast, accurate teleoperated robots with the operator's ability to feel the environment at the robot's field. The authors conceived a haptic mechanism called MEMICA (remote MEchanical MIrroring using Controlled stiffness and Actuators) that can enable the design of high dexterity, rapid response, and large workspace haptic system. The development of a novel MEMICA gloves and virtual reality models are being explored to allow simulation of telesurgery and other applications. The MEMICA gloves are being designed to provide intuitive mirroring of the conditions at a virtual site where a robot simulates the presence of a human operator. The key components of MEMICA are miniature electrically controlled stiffness (ECS) elements and Electrically Controlled Force and Stiffness (ECFS) actuators that are based on the use of Electro-Rheological Fluids (ERF). In this paper the design of the MEMICA system and initial experimental results are presented.

In previous works, the possibility of the electrostrictive polymer as the actuator use has been proved. In this paper we address an actual design of an actuator and an inchworm type robotic mechanism using the electrostrictive polymer. The robot will be developed to move horizontally, vertically with steering capability, aiming for navigation in small tubular structures such as flexible pipes but now in this stage a simple bellows type robot capable of accomplishing the linear movement like that of an inchworm is introduced. The issues about the mechanism design of the prototype, which has already been developed and under the consideration of reduction in size, are discussed and preliminary results of experiments are given.

Electrostrictive polymers such as silicone, acrylic, and polyurethane can achieve large strain and stress with high electric field. This property can make electrostrictive polymers useful actuators. While there are some limitations in reducing existing actuators, there are few in electrostrictive polymer actuators. Therefore, an electrostrictive polymer can be used to design an actuator of a micro robot system. In this paper, an actuator system, which consists of an electrostrictive polymer actuator and its controller, is designed and is implemented. Major characteristics about this actuator system are measured and are discussed. Also the performance of this actuator system under a control technique is measured.

A tactile feel display device for virtual reality was developed using Nafion-Platinum composite type EAP actuator (known as IPMC or ICPF). Conventional tactile displays can hardly express tactile human feeling of the fine touch of the surface of a cloth, because their mechanisms cannot excite minute distributed stimuli on human skin. We propose a new ciliary device using ICPF actuators. The ICPF has sufficient softness, utilizing the passive material property, that complex control is not required. The low drive voltage is safe enough for the touch of fingers. Its simple operation mechanism allows miniaturization for practical equipments. The developed device was designed with a number of cilia consisting of ICPF actuators, where a cilium is 2 mm wide and 5 mm long. An ICPF membrane is cut into pectination, and only the cilium part is plated and has a function of an actuator. An inclined configuration of the cilia produces variety of stimuli to human skin controlling frequencies. We tried to display both pressure and vibration at the same time using modulated low and high frequencies. The result clearly shows that over 80% of the subjects sensed some special tactile feeling. A comparison with real material samples shows that this display can present a subtle distinction of tactile feeling of cloth, especially like a towel and denim.

The ability to manipulation of biological cells while having reflective-force information from the cells is a key technology necessary for many new applications in Bio-MEMS, but is currently lacking in all cellular manipulators. We will report on our preliminary experimental work in using an Ionic Conducting Polymer Film (ICPF) to develop a biological cell robotic gripper with force sensing capability. ICPF actuators are able to give large deflection with small input voltage (~5V), and also able to give relatively large output voltage due to deflection by a mechanical forces, thus are investigated as a possible material to make force-feedback controlled cellular manipulators in our work. A laser micromachining process is introduced to fabricate arrays of ICPF griping devices, which can be potentially integrated onto a substrate to develop a micro manipulation system. Individual multi-finger grippers with dimensions of 200micrometers x 200micrometers x 3000micrometers for each finger were realized. We will report on the design, fabrication procedures, and operating performance of these micro-grippers. Further development in the reduction of size of these actuators will enable effective force-feedback control of underwater micro objects and lead to new frontiers in cellular manipulation.

Presented is a novel mammalian heart compression/assist device in the form of a multi-fingered robotic hand equipped with an assembly of thick ionic polymer-metal composite (IPMC) fingers encased inside a water bag. The proposed multi-fingered heart compression device (MFHCD) is entirely endoscopically implantable and can be directly or transcutaneously energized by inductive magnetoresonant generators.

The fabrication, testing and performance of a new device for the protection of optical sensors will be described. The device consists of a transparent substrate, a transparent conducting electrode, insulating polymers, and a reflective top electrode layer. Using standard integrated circuit fabrication techniques, arrays of apertures can be created with sizes ranging from micrometers to millimeters. A stress gradient resulting from different thermal coefficients of expansion between the top polymer layer and the reflective metal electrode, rolls back the composite thin film structure from the aperture area once a release layer is chemically etched away, forming a tightly curled film at one side of the aperture - the open condition. The application of a voltage between the transparent conducting and reflective metal electrodes creates an electrostatic force which unrolls the curled film, closing the artificial eyelid. Fabricated devices have been completed on glass substrates with indium tin oxide electrodes. The curled films have diameters of less than 100micrometers with the arrays having mechanical transparencies of over 80%. Greater transparencies are possible with optimized designs. The electrical and optical results from the testing of the artificial eyelid will be discussed including the optimization of the design and fabrication for applications in systems that extend into the IR spectrum. A primary area of investigation is the choice of the transparent conducting electrode.

Herein we report the design, synthesis, and properties of novel electromechanical actuators based on organic polymers that are capable of redox-induced dimensional change at the molecular level. Specifically, this report will focus on regioisomers of poly(cyclooctatetrathiophene), and evidence of corresponding single molecule actuation. Cyclooctatetrathiophene has been calculated to undergo atom-to-atom dimensional changes of up to 10% upon redox switching. In theory, this distance change occurring within the repeat unit of the polymer can be translated into dimensional changes in both the single polymer chain and bulk material. As such, electromechanical actuation in this system is an intrinsic property of the individual chains, not a bulk property of the material. However, this translation varies as a function of both environment and regioisomer. Our ultimate goal of demonstrating single-molecule electromechanical actuation will be discussed herein.

This paper deals with the discovery of giant low voltage electromechanical actuation and sensing effects in an electroactive polymer composite made with a composite of poly(ethylene oxide), PEO, and poly(ethylene glycol), PEG. The experimental observations and robust performance of the new solid-state polymer actuators and sensors in the form of a strip, which is suitably surface-electroded and cation- doped, are reported herein. Recent laboratory discovery shows that such solid-state actuators are polymeric materials capable of exhibiting large motion actuation capabilities (>2% strain) in a low electric field imposed across the strip (<10 V/mm) with considerable stress (>10MPa) and fast responses (>10Hz). Moreover, a stable operation over ten million's of cycles in air is achieved with nearly no performance degradation. Also, by bending the strip, a voltage is produced across the thickness of the strip showing direct mechanoelectric behaviors that can be used in polymeric sensors either dynamically or quasi- statically. It must be pointed out that effectively constructed solid-state polymer sensors and actuators overcome many inherent problems that other state-of-the-art polymer sensors and actuators have, such as rate limiting dopant intercalation of conducting polymers, high voltage requirement of ferroelectric polymers, favored wet conditions for ionic polymer metal composites, and poor mechanical properties of ionic polymeric gels. Therefore, the reported solid-state polymer actuators and sensors show a tremendous potential for use in biomimetic/medical, industrial, and domestic applications superior to any other polymer materials identified so far.

Recently, it was reported that an electrostrictive graft elastomer exhibits large electric field-induced strain (4%). Combined with its high mechanical modulus, the elastomer can offer very promising electromechanical properties, in terms of output mechanical energy density, for an electroactive polymeric material. Therefore, it has been considered as one of the candidates that can be used in high performance, low mass actuation devices in many aerospace applications. Various bi-layer-based bending actuators have been designed and fabricated. An analytic model based on beam theory in the strength of materials has been derived for the transverse deflection, or curvature, and the longitudinal strain of the bi-layer beam. The curvature and strain are functions of the applied voltage and the thickness, width, and Young's modulus of the active and passive layers. The model can be used to optimize the performance of electrostrictive graft elastomer-based actuators to meet the requirements of various applications. In this presentation, optimization and sensitivity studies are applied to the bending performance of such actuators.

Piezoelectric thin films incorporating poly(sodium 4- styrenesolfonate)(PSS) and poly(diallyldi-methylammonium chloride)(PDDA) were 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 very important role in molecular alignment resulting in net polarization in the layer-by-layer structured ultrathin film, a process quite different from that used to form conventional piezoelectric films. Further study concerning the principles governing the novel ESA processing of piezoelectric films is on-going.

Polyaniline, (PANI) in the form of emeraldine base, was synthesized by polymerizing aniline in acid solutions at different sub-zero temperatures to give a range of molecular weights between 100,000 and 300,000 gmol^-1. Molecular weights were measured using gel permeation chromatography (GPC). The polymers were formed into solvent-cast films using an acid processing technique, involving 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPSA) as the solvating/protonating acid group and dichloroacetic acid (DCA) plus formic acid (FA) as the solvent. The dried, free-standing films were stretched by drawing over a hot pin to align the polymer chains. Fibers were prepared by spinning more concentrated solutions into a butanone coagulation bath. Conductivity measurements were then made on the drawn films and fibers, and tensile test measurements performed to determine the peak stress and modulus of the drawn films and fibers. The reaction conditions under which the different polyanilines were synthesized, and their molecular weight, were found to have a definite effect upon both the electrical and mechanical properties of the drawn films and fibers. The drawn films and fibers can be used as mechanical actuators.

The low actuating voltage and quick bending responses of ion-exchange polymer metal composite (IPMC) are considered very attractive for the construction of various types of actuators. The principle of IPMC actuation under electric field has been believed to be the ion cluster flux and electro-osmotic drag of water from anode to cathode direction through the hypothetical hydrophilic channels in the perfluorinated sulfonic acid polymer chains. In this study, the effect of water content residing in the perfluorinated polymer was investigated in terms of CV (cyclic voltammetry response, deformation, and bending moment. As a preliminary result of DSC thermal analysis, the water residing in the IPMC actuator seems to reside as free water and bound water, each corresponding to interstitial and hydrogen-bonded water molecules. Using the classical lamination theory (CLT), a modeling methodology was developed to predict the deformation, bending moment, and residual stress distribution of anisotropic IPMC thin plates. In this modeling methodology, the internal stress evolved by the unsymmetric distribution of water inside IPMC was quantitatively calculated and subsequently the bending moment and the curvature were estimated for various geometry of IPMC actuator. The model prediction and experimental results were compared well with practical observation and experimental results demonstrating the validity of the developed modeling methodology.

Recently, Electrostrictive polymers (EPs) are studied for micro-actuator, because of similarity of body tissue. Electrostrictive polymers (EPs) are based on the deformation of dielectric elastomer polymer in the presence of an electric field. Modeling of electrostrictive polymer has been studied, which is about voltage and displacement. And there are many parameters such as Young's modulus, voltage, thickness of EPs, pre-strain, dielectric, frequency and temperature which effect to movement of EPs. To do exact modeling, all parameters are included. In order to use as actuator, we accurately understood about the parameter that we refer above. And we have to execute modeling which parameters are considered. We used FEM in order to understand effects of parameters. Specially, because of pre-strain effects are very important, we derive the relations of stress and strain by using elastic strain energy.

The actuation of electrostrictive polymer (EP) actuator under electric field is known due to the electrostatic force between the parallel compliant electrodes on both sides of polymer film, which means the magnitude of electric potential between the electrodes is one of the determinative parameters of the actuation. The actuation is also dependent on the material properties such as dielectric constant and elastic modulus of polymers. In order to maximize the actuation behavior, high dielectric constant and low elastic modulus is essential. Dielectric constant of polymers is typically known to lie between 2.5 and 10, and it depends highly upon the frequency of electric field. The elastic modulus of polymeric elastomers is also dependent highly on the mechanical frequency of motion, when the EP actuator is periodically actuated. The mechanical frequency is generally equivalent to the electric one, since the mechanical motion is induced by the changes of the electric field. In this study, the electrostriction behavior was modeled with the response to the applied electric field in view of the dielectric and the mechanical characteristics of polymeric elastomer.

Electro-Active Paper (EAPap) is a paper that produces large displacement with small force under electrical excitation. EAPap is made with a chemically treated paper by bonding thin aluminum foils on both sides of the paper to comprise electrodes. When electric voltage is applied on the electrodes the EAPap produces bending displacement. However, the displacement output has been unstable and degraded with time scale. To improve the bending performance of EAPap, different paper fibers-broad-leaf, needle-leaf, bacteria cellulose and Korean traditional paper, and additive chemicals are tested. It was observed that needle-leaf paper exhibits better results then others. By eliminating the effect of adhesive layer and selecting a proper paper fiber, the displacement output has been stable with long time scale. The operational principle of EAPap is, we believe, based on the electrostriction effect associated with intermolecular interaction of the constituents of the paper. To confirm this result, more investigation of the paper quality should be followed in the beginning of paper manufacturing process. Since EAPaps are quite simple to fabricate and lightweight, various applications including flexible speakers, active sound absorbing materials and smart shape control devices can be possible.

In this work, we investigated the electrochemical actuation of gilded polyaniline bilayers in acidic aqueous electrolytes. Gilding was found to be a useful method to ensure a uniform potential distribution across polyaniline films so that well-defined electrochemistry and electrochemical actuation could be obtained. Electrochemical actuation of gilded polyaniline bilayers was studied by means of bending and linear actuation. Actuation could be obtained by a number of electrical stimulation modes including cyclic voltammetry (CV), square wave potential (SWP) and square wave current (SWC). Within the potential range of -0.2 ~ 0.6 V (vs Ag/AgCl), the polyaniline films expanded upon oxidation and contracted upon reduction, which corresponds to the first redox process of polyaniline between the leucomeraldine and emaraldine oxidation states. Actuation obtained in this potential range is related to the insertion/deinsertion of the electrolyte anion upon oxidation/reduction of polyaniline. It was found that, due to the thin thickness of the gold layer, not only fast bending actuation but also linear actuation could be achieved for the resulting gilded polyaniline bilayers. Extending the applied potential to more positive potentials, polyaniline degradation and oxidation of gold layer were observed.

In the near future, we will find biomimetic undersea robots in the forefront of unmanned underwater applications due to their ability to operate in new, challenging, and highly dynamic environments such as rivers, surf, and turbulent pipe flow. In particular, fish-like vehicles (FLVs) have emerged as a viable technology for highly maneuverable, efficient and stealthy platforms. Attempts to produce fish-like motion using conventional mechanical means have proven difficult, however, resulting in complex and unreliable machines, especially when compared to the simplicity of a rotating propeller and conventional control surfaces. To take full advantage of fish-like propulsion, a new actuation strategy is needed, to which artificial muscles may be uniquely suited. Some artificial muscles are made of materials with relatively low specific gravity (compared to conventional mechanical systems), and so will be nearly neutrally buoyant in underwater applications. This is critical in FLV actuation, as correct longitudinal mass distribution is required to avoid stability problems. Additionally, some artificial muscle formulations require water, sometimes including an electrolyte, which is easily provided in underwater applications. Finally, for stealthy applications, artificial muscles may provide acoustically quiet actuation due to their suppleness and reduced number of interconnecting mechanical components. In this paper, we suggest artificial muscle-based actuation strategies for FLVs, based on experience with the Vorticity Control Unmanned Undersea Vehicle (VCUUV), an eight-foot long autonomous robotic tuna. Recently developed artificial muscles are surveyed and evaluated as to their suitability for fish-like propulsion. Requirements for force, power, and strain as well as implementation issues are discussed.

Electrostrictive composites of thermoplastic elastomer polyurethane (PU) and the ferroelectric lead zirconate titanate (PZT) of various volume fractions have been prepared by hot-roller miller. X-ray diffraction results and SEM micrographs showed that the ceramic crystallized in the ferroelectric phase and was dispersed uniformly in the elastomer. The elastic modulus and dielectric permittivity increased with PZT volume fractions. For composites of low PZT volume fraction, negative electrostrictive strain (contraction) was observed. As the PZT volume fraction increased to more than 6%, the composites exhibited a switching characteristic when the applied electric field was increased to a critical value. The critical electric fields decreased with increasing PZT volume fractions. This effect can be explained as the resultant of the electrostriction of PU and polarization reversal of the PZT at high field. This interesting property of the PU/PZT composite will lead to some switching actuations for high electric field applications.

Conducting polymer actuators generate forces that exceed those of mammalian skeletal muscle by up to two orders of magnitude for a given cross-sectional area, require only a few volts to operate, and are low in cost. However application of conducting polymer actuators is hampered by the lack of a full description of the relationship between load, displacement, voltage and current. In an effort to provide such a model, system identification techniques are employed. Stress-strain tests are performed at constant applied potential to determine polypyrrole stiffness. The admittance transfer function of polypyrrole and the associated electrolyte is measured over the potential range in which polypyrrole is highly conductive. The admittance is well described by treating the polymer as a volumetric capacitance of 8*10⁷ F*m³ whose charging rate is limited by the electrolyte resistance and by diffusion within polypyrrole. The relationship between strain and charge is investigated, showing that strain is directly proportional to charge via the strain to charge density ratio, (alpha) = 1*10+-10 m³*C^-1, at loads of up to 4 MPa. Beyond 4 MPa the strain to charge ratio is time dependent. The admittance models, stress/strain relation and strain to charge relationship are combined to form a full description of polypyrrole electromechanical response. This description predicts that large increases in strain rate and power are obtained through miniaturization, yielding bandwidths in excess of 10 kHz. The model also enables motor designers to optimize polypyrrole actuator geometries for their applications.

The classic movie Metropolis (1926), which is nowadays considered a cinema milestone, has shown the possibility to build robots called androids that are science and fiction run together to realize a dream: the human-like robot. In that movie, Dr. Rotwang transforms a simple and cold calculating robot into the body of a beautiful woman. Robots have often been depicted as metal creatures with cold steel bodies, but there is no reason why metals should be the only kind of material for construction of robots. The authors examined the issues related to applying electroactive polymers materials (EAP) to the entertainment industry. EAP are offering attractive characteristics with the potential to produce more realistic models of living creatures at significantly lower cost. This paper seeks to elucidate how EAP might infiltrate and ultimately revolutionize entertainment, showing some applicative examples.