This PDF file contains the front matter associated with SPIE Proceedings Volume 6524, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and the Conference Committee listing.

Fish are capable of remarkable locomotor performance and use their fins extensively for both propulsion and maneuvering. Recent interest in using fishes as inspiration for the design of a new generation of autonomous underwater vehicles has prompted both new experimental studies of fish locomotor function and efforts to use electroactive polymers (EAP) as actuators in fish-inspired propulsive devices. The fins of fishes allow precise control over body position and vectoring of thrust during propulsion and maneuvering. Recent experimental studies of fish locomotion have revealed that fins exhibit much greater flexibility than previously suspected and that there is considerable deformation of the fin surface during locomotion. The fins of the large group known as ray-finned fishes are supported by fin rays, which have a bilaminar structure that allows active curvature control of the ray and fin surface by the fin musculature. Fish have up to seven different fins, and these fins may interact with each other hydrodynamically during locomotion. Fish fins provide an excellent test platform for the use of electroactive polymer actuators as the frequency of movement is typically less than 5 Hz, and fin muscle strains typically range from 2 to 10%. Recent developments of biorobotic fish pectoral fins actuated with EAP are reviewed.

Nature is filled with highly effective biological mechanisms that were refined thru evolution over millions of years offering an incredible model for inspiring human innovation. Humans have always made efforts to imitate nature's inventions. Advances in technology led to capabilities that allow adapting nature innovation beyond simply copying and the pool of possibilities in materials, structures, methods, processes and systems is enormous. Electroactive polymers (EAP) are increasingly being recognized as an important enabling technology for making biologically inspired capabilities. Using them as artificial muscles they are being considered for use a wide range of fields including medical, commercial, entertainment and many others. This paper reviews the up to date role that EAP is playing in advancing biomimetics and the field outlook.

Electroactive polymers (EAPs) are receiving increasing interest from researchers due to their unique capabilities and numerous potential applications in biomimetic robots, smart structures, biomedical devices, and micro/nanomanipulation. Since these materials are relatively new, it is imperative to educate students and the general public to raise their awareness of EAP potentials and produce the talent pool needed for continuing, rapid advances in the field of EAPs. In this paper we describe our concerted effort in teaching EAP to undergraduates, grade school students, and the general public, through hands-on research and learning on EAP-based biomimetic robots. Two integrated activities are highlighted: A senior Capstone design program on EAP robots, and the subsequent programs that use these developed robots to reach out to pre-college students. A robotic fish and a sociable robot enabled by ionic polymer-metal composite materials are used as examples throughout the paper.

Ionic Polymer Metal Composites (IPMCs) have several unique characteristics such as, low driving voltage, no moving parts, etc., that allow the material to fulfill specific needs for medical device applications. However, there are numerous challenges that must be addressed in order to utilize IPMC in medical devices. The research presented is a culmination of efforts that address a number of these issues; such as electrolysis of water, safety concerns, material characterization and in vitro testing. Work on IPMC development has raised the threshold of the electrolysis of water during actuation from 2.35 V to 2.46 V in Tyrode's solution. The problem of back relaxation under DC excitation has been reduced. To ensure accurate measurements of IPMC performance, for medical applications, it is imperative that the appropriate in vitro testing conditions are chosen, such details are discussed. Material characterization techniques developed and used by Pavad Medical, which are based on medical device needs, are also highlighted.

Fundamental studies of Dielectric Elastomer Actuators (DEAs) using viscoelastic materials such as VHB 4905/4910 from 3M showed significant advantages at high stretch rates. The film's viscous forces increase actuator life and the short power-on times minimize energy losses through current leakage. This paper presents a design paradigm that exploits these fundamental properties of DEAs called discrete actuation. Discrete actuation uses DEAs at high stretch rates to change the states of robotic or mechatronic systems in discrete steps. Each state of the system is stable and can be maintained without actuator power. Discrete actuation can be used in robotic and mechatronic applications such as manipulation and locomotion. The resolution of such systems increases with the number of discrete states, 10 to 100 being sufficient for many applications. An MRI-guided needle positioning device for cancer treatments and a space exploration robot using hopping for locomotion are presented as examples of this concept.

Conjugated polymers are promising actuation materials for bio and micromanipulation systems, biomimetic robots, and biomedical devices. Sophisticated electrochemomechanical dynamics in these materials, however, poses significant challenges in ensuring their consistent, robust performance in applications. In this paper an effective adaptive control strategy is proposed for conjugated polymer actuators. A self-tuning regulator is designed based on a simple actuator model, which is obtained through reduction of an infinite-dimensional physical model and captures the essential actuation dynamics. The control scheme is made robust against unmodeled dynamics and measurement noises with parameter projection, which forces the parameter estimates to stay within physically-meaningful regions. The robust adaptive control method is applied to a trilayer polypyrrole actuator that demonstrates significant time-varying actuation behavior in air due to the solvent evaporation. Experimental results show that, during four-hour continuous operation, the proposed scheme delivers consistent tracking performance with the normalized tracking error decreasing from 11% to 7%, while the error increases from 7% to 28% and to 50% under a PID controller and a fixed model-following controller, respectively. In the mean time the control effort under the robust adaptive control scheme is much less than that under PID, which is important for prolonging the lifetime of the actuator.

Interpenetrating polymer networks (IPN) in which one elastomer network is under high tension balanced by compression of the second network have been shown to exhibit electrically-induced strain up to 300% and promise a number of polymer actuators with substantially enhanced performance and stability. This paper describes the mechanical and thermal properties of the IPN electroelastomer films. The quasi-linear viscoelastic model and Yeoh strain energy potential are used to characterize the viscoelastic response and stress-strain behavior of the IPN films in comparison with 3M VHB films, primary component network in the IPN films. Material parameters were determined from uniaxial stress relaxation experiments. An analysis of the results confirms that the IPN composites have reduced viscoelasticity and fast stress-strain response due to preserved prestrain. Differential scanning calorimetry showed two glass transition temperatures that are slightly shifted from the two component networks, respectively. The two networks in the IPN are considered to be independent of each other. The thermal property is also studied with termogravimetric analysis (TG).

Dielectric elastomer actuators in a cylindrical configuration, called "spring roll", have been used by the Empa team for the first arm wrestling match between a human and a robotic arm driven by electroactive polymers (EAP) on the EAPAD conference 2005 in San Diego. In this work, electromechanical coupling in EAP is investigated at the example of spring rolls. The commonly used equation derived by Pelrine et al. (Sensors and Actuators A, 64, 1998) is analyzed and the influence of the uncoated ("passive") parts is evaluated. Longer passive parts cause a force reduction in axial direction which affects the performance of the actuator. Results have shown that (i) the equation of Pelrine represents a simplified description of electromechanical coupling; (ii) the equation can be used for modeling electromechanical coupling in spring rolls and (iii) the relative force reduction agrees to a great extent with the ratio between the uncoated area of a spring roll and the total (coated and uncoated) area. These results are relevant for design and optimization of spring rolls.

Currently, there is a major engineering challenge associated with Ionic Polymer-Metal Composites (IPMCs) that needs to be resolved before they can be widely adopted in future engineering markets--relaxation of the IPMC actuator under a DC voltage. In this paper, we rigorously discuss the origin of the relaxation phenomena of IPMCs. Our measured voltammograms and deflection data of IPMCs reveal that the relaxation phenomena of the IPMC actuators are primarily caused by the overpotential of surface electrodes. The overpotential values of ca. +1 V were clearly noted in many IPMC samples. We believe that the relaxation of IPMCs originate from the platinum oxide formation during actuation-a key surface reaction. The IPMC solvated with 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim] [PF6]) showed a large bending, but there was no relaxation during actuation because there was no platinum oxide formation.

This paper presents a electro-mechanical model of an IPMC sheet. The model is developed using Finite Element method. The physical bending of an IPMC sheet due to the drift of counter-ions (e.g Na+) and water in applied electric field are simulated. Our model establishes a cause-effect relationship between the charge imbalance of the counter-ions and the mechanical bending of the IPMC sheet. The model takes into account the mechanical properties of the Nafion polymer as well as the platinum coating. As the simulations are time dependent, a transient model is used and some additional parameters, such as damping coefficients, are included. In addition to electro-mechanical model, electrochemical reactions are introduced. Equations describing periodic adsorption and desorption of CO and OH on a platinum electrode of an IPMC muscle immersed into formaldehyde solution are coupled to mechanical properties of the proposed model. This permits us to simulate self-oscillatory behavious of an IPMC sheet. The simulation results are compared to experimental data.

In this paper, one-dimensional charge redistribution of IPMC material under dynamic electric potentials is studied. An analytical solution of normalized charge density is obtained to account for the charge movement under applied electric potentials. This solution is applicable for both static and dynamic electric potentials applied to IPMC material. Based on this solution, the thicknesses of boundary layers under dynamic potentials can be calculated. The obtained solutions are useful for further understanding and modeling of the mechanism of IPMC sensing and actuation.

New lightweight, compliant, reliable and cheap contractile linear actuators are demanded today for many fields of application, such as robotics, automation and biomedical disciplines. Within the family of electroactive polymers, dielectric elastomers are rapidly emerging as high-performance transduction materials, resulting particularly attractive in order to accomplish different kinds of tasks. The design of efficient device architectures, capable of taking the most from the material properties with practical solutions, is not trivial. In particular, the state of the art of contractile dielectric elastomer actuators offers device configurations resulting not always of easy fabrication. To overcome this drawback, a new actuating configuration, referred to as 'folded dielectric elastomer actuator', has been recently described. This paper presents prototype samples of this new type of actuator, along with different examples of applications currently being developed.

Cell-based sensors are being developed to harness the specificity and sensitivity of biological systems for sensing applications, from odor detection to pathogen classification. These integrated systems consist of CMOS chips containing sensors and circuitry onto which microstructures have been fabricated to transport, contain, and nurture the cells. The structures for confining the cells are micro-vials that can be opened and closed using polypyrrole bilayer actuators. The system integration issues and advances involved in the fabrication and operation of the actuators are described.

Artificial molecular motors have recently attracted considerable interest from the nanoscience and nanoengineering community. These molecular-scale systems utilize a 'bottom-up' technology centered around the design and manipulation of molecular assemblies, and are potentially capable of delivering efficient actuations at dramatically reduced length scales when compared to traditional microscale actuators. When stimulated by light, electricity, or chemical reagents, a group of artificial molecular motors called bistable rotaxanes - which are composed of mutually recognizable and intercommunicating ring and dumbbell-shaped components - experience relative internal motions of their components just like the moving parts of macroscopic machines. Bistable rotaxanes' ability to precisely and cooperatively control mechanical motions at the molecular level reveals the potential of engineering systems that operate with the same elegance, efficiency, and complexity as biological motors function within the human body. We are in a process of developing a new class of bistable rotaxane-based electroactive/photoactive biomimetic muscles with unprecedented performance (strain: 40-60%, operating frequency: up to 1 MHz, energy density: ~50 J/cm³, multi-stimuli: chemical, electricity, light). As a substantial step towards this longterm objective, we have proven, for the first time, that rotaxanes are mechanically switchable in condensed phases on solid substrates. We have further developed a rotaxane-powered microcantilever actuator utilizing an integrated approach that combines "bottom-up" assembly of molecular functionality with "top-down" micro/nano fabrication. By harnessing the nanoscale mechanical motion from artificial molecular machines and eliciting a nanomechanical response in a microscale device, this system mimics natural skeletal muscle and provides a key component for the development of nanoelectromechanical system (NEMS).

The objective of this research was to describe and characterize the performance of an innovative new method of actuating a synthetic jet. This particular method utilizes a pre-strained dielectric elastomer membrane excited to operate at resonance. The paper describes the mechanism by which the actuator operates, the experimental techniques used to characterize it and discusses the results of the characterization. A series of experiments were devised to capture the influence of specific device parameters on the actuator system performance. The device parameters considered were: chamber volume, orifice diameter, orifice length, electrode area, excitation frequency, and excitation amplitude. Six metrics were collected for each of the tests: membrane displacement, chamber pressure, exit velocity, auditory signal, supply voltage, and supply current. Based on the cases tested, peak attainable orifice velocity was experimentally determined to be approximately 17 m/s, though the authors believe this can be significantly increased. Basic system design guidelines were also determined, and directions for future work have been identified.

In this paper we present a new artificial muscle actuator for rectilinear motion made of synthetic elastomer, which is mainly focused on the robotic applications. Previously, we have developed a new material for actuating means, named "synthetic elastomer". Synthetic elastomer allows their material properties such as mechanical as well as electrical properties to be adjusted according to the requirements. Using the synthetic elastomers made of the recipe adjusted for the robotic application, a new design of the artificial muscle actuator, called multi stacked actuator is proposed. The actuator is comprised of multiple stacks of synthetic elastomer coated with compliant electrodes and connecting disks. This unique design enables its linear actuation with the large strain of active length as well as large force. Experimental works are conducted and the effectiveness of the actuator is validated.

Material properties of Electro-active paper (EAPap) actuator were investigated under different environmental conditions such as humidity and temperature. Understanding of humidity and temperature effects on the material behavior of EAPap during visco-elastic deformation regime provided useful information on structural changes of EAPap by environmental factors. The pulling test results showed that the humidity and temperature heavily impact the mechanical properties of EAPap. Electro-mechanical coupling effects were investigated by applying electric field during the pulling test. Change of elastic modulus under different electric fields provides directional dependency of EAPap and strong shear electro-mechanical coupling. Creep behavior of cellulose paper was studied to figure out mechanical strength of EAPap under different ambient conditions. Tests under different humidity levels with fixed temperature and different temperatures with fixed humidity provided the coupled hygrothermal effects on the performance of EAPap.

Polymeric actuators, electroactive polymer actuators, electromechanical polymeric actuators, artificial muscles, and other, are usual expressions to name actuators developed during the last 15-20 years based on interactions between the electric energy and polymer films. The polymeric actuators can be divided into two main fields: electromechanical actuators working by electrostatic interactions between the polymer and the applied electric fields, and electrochemomechanical actuators, or reactive actuators, working by an electrochemical reaction driven by the flowing electric current. The electromechanical actuators can be classified into electrostrictive, piezoelectric, ferroelectric, electrostatic and electrokinetic. They can include a solvent (wet) or not (dry), or they can include a salt or not. Similitude and differences related to the rate and position control or to the possibility or not to include sensing abilities are discussed.

Most hydrogel actuators and sensors are made via acrylate polymerizations. Because these chain reactions are inhibited by oxygen, it is difficult to prepare thin films or dots with good control. Epoxy curing chemistry is much less sensitive to experimental conditions. We have previously shown that hydrogels formed from reaction between water-soluble amines and epoxides can be readily printed. If the gel is filled with conducting carbon at a level close to the percolation threshold, the resistance changes as water is taken up or removed from the gel. In particular, a pH decrease results in ionization of amine groups and drives swelling of the gel. By incorporating an enzyme, such as glucose oxidase, that releases hydrogen ions when its substrate is present, a resistance change can be used to measure substrate concentrations. These gels also respond to stress with a change in resistance. By making the gel the anode or cathode of an electrolytic cell, they can also be formed as actuators that expand or contract as the pH changes locally. Epoxy chemistry has been little explored for gels. It is very versatile and could be used to make a wide range of gel composites with one or more phases, varying water contents, varying functional groups and a range of electrical conductivity.

Dielectric elastomer actuators exert strain due to an applied electric field. With advantageous properties such as high efficiency and their light weight, these actuators are attractive for a variety of applications ranging from biomimetic robots, medical prosthetics to conventional pumps and valves. The performance and reliability however, are limited by dielectric breakdown which occurs primarily from localized defects inherently present in the polymer film during actuation. These defects lead to electric arcing, causing a short circuit that shuts down the entire actuator and can lead to actuator failure at fields significantly lower than the intrinsic strength of the material. This limitation is particularly a problem in actuators using large-area films. Our recent studies have shown that the gap between the strength of the intrinsic material and the strength of large-area actuators can be reduced by electrically isolating defects in the dielectric film. As a result, the performance and reliability of dielectric elastomers actuators can be substantially improved.

One drawback of Electro Active Polymer (EAP) materials for industrial actuation purposes is that the power needed to scale up the technology is prohibitive both in the sheer magnitude and cost. The development of a reversible ionic photo-activated polymer (IPAP) actuator material is a way to circumvent the prohibitive power needs and gain industrial acceptance of polymer actuator materials. By doping electro active or ionic polymers with photo reversible ionic sources it is possible to create similar response characteristics to that of ionic EAP actuators. The power needed to drive a single light source would inherently be much less that needed to drive individual EAP actuators as size of application increased, this reduction in power would also be multiplied by the number of actuators in a given system. It is also theorized that the speed of actuation cycles would be increased by diffuse irradiation throughout the material. Even more attractive is the possibility of the material being activated from natural daylight irradiation and the need for electrical power eliminated.

As polymer actuator performance improves there is an increasing demand to understand and compare properties. Past comparisons have relied on general statements of properties but do not capture the interdependence of these properties or keep up with the rapid pace of change. Modeling such interdependencies is complex. An alternative is to compile many measurements. A new actuator database has been created that is a compilation of experimental methods and results (mechanical, electrical, chemical and other properties) combined with a web interface. The objective is to capture actuator performance under a wide variety of conditions. The current content of the page is presented and justified. Researchers may submit data to the web page via an online form.

Ionomeric polymer transducers have received considerable attention in the past ten years due to their ability to generate large bending strain and moderate stress at low applied voltages. Ionic polymer transducers consist of an ionomer, usually Nafion, sandwiched between two electrically conductive electrodes. Recently, a novel fabrication technique denoted as the direct assembly process (DAP) enabled controlled electrode architecture in ionic polymer transducers. A DAP transducer consists of two high surface area electrodes made of uniform distributed particles sandwiching an ionomer membrane. In this paper theoretical investigations as well as experimental verifications are performed. The model consists of a convection-diffusion equation describing the chemical field as well as a Poisson equation describing the electrical field. This modeling technique is modified to capture the chemo-electric behavior in the high surface area electrodes of a DAP fabricated transducer. The model assumes highly conductive particles randomly distributed in the electrode area. This is the first electro-chemical modeling account of high surface area electrodes in ionic polymer transducers. Traditionally, these kinds of electrodes were simulated with boundary conditions representing flat electrodes with a large dielectric permittivity at the polymer boundary. In the experimental section, several transducers are fabricated using the DAP process on Nafion 117 membranes. The architecture of the high surface area electrodes in these samples is varied. The concentration of the spherical gold particles is varied from 30 vol% up to 60 vol%, while the overall thickness of the electrode is varied from 10 &mgr;m up to 40 &mgr;m micrometer at a fixed concentration. The flux and charge accumulation in the materials are measured experimentally and compared to the results of the numerical simulations. Finally, the high surface area electrodes are compared to flat gold electrodes.

Ionic polymer-metal composites (IPMC) are soft actuators with potential applications in the fields of medicine and biologically inspired robotics. Typically, an IPMC bends with approximately constant curvature when voltage is applied to it. More complex shapes were achieved in the past by pre-shaping the actuator or by segmentation and separate actuation of each segment. There are many applications for which fully independent control of each segment of the IPMC is not required and the use of external wiring is objectionable. In this paper we propose two key elements needed to create an IPMC, which can actuate into a complex curve. The first is a connection between adjacent segments, which enables opposite curvature. This can be achieved by reversing the polarity applied on each side of the IPMC, for example by a through-hole connection. The second key element is a variable curvature segment. The segment is designed to bend with any fraction of its full bending ability under given electrical input by changing the overlap of opposite charge electrodes. We demonstrated the usefulness of these key elements in two devices. One is a bi-stable buckled IPMC beam, also used as a building block in a linear actuator device. The other one is an IPMC, actuating into an S-shaped curve with gradually increasing curvature near the ends. The proposed method of manufacturing holds promise for a wide range of new applications of IPMCs, including applications in which IPMCs are used for sensing.

Investigations of the actuation properties of free standing PPy and PEDOT films in a propylene carbonate-triflate electrolyte (PC/TBACF₃SO₃) under isotonic (constant load) conditions are presented in this work. The PPy film showed mixed ion movement during charging and discharging in cyclic voltammetric and chronoamperometric experiments. At a potential of -1.0 V the maximum strain was in the range of 1-2 % whereas at the anodic potential of +1.0 V strains in the range of 3-4 % were observed. Cyclic voltammetry experiments at higher scan rates to 10 mV/s led to a decrease in the anodic strain and an increase in the cathodic strain before it declined at higher scan rates. The free-standing PEDOT films showed mainly cathodic actuation at the potential -1.0 V and the size of actuation was again dependent upon the scan rate. Cation movement is discussed in terms of the immobilisation of CF₃SO₃^- anions during polymerisation. Extended potential step experiments showed good actuation and low creep in the potential range between 0.0 and +1.0 V. The surface morphology (SEM) showed an open porous structure for PEDOT in contrast to the smooth morphology of PPy.

Polyaniline conductive polymers exhibit great potential for linear actuator applications. Many recent studies report methods to develop polyaniline-based materials with increased mechanical properties, electrical conductivity, and faster response time during actuation. In this study, porous blends of poly(methylmethacrylate) and polyaniline are processed using a two phase batch foaming setup. The effect of materials, processing, and system parameters on the physical properties of the resulting cellular structure are investigated. Hence, the effect of density and cell morphology on the electrical conductivity is elucidated.

We report on the use of the bulge test method to characterize the mechanical properties of miniaturized buckling-mode dielectric elastomer actuators (DEA). Our actuator consists of a Polydimethylsiloxane (PDMS) membrane bonded to a silicon chip with through holes. Compliant electrodes are fabricated on both sides of the membrane by metal ion implantation. The membrane buckles when a critical voltage is applied to the electrodes. The maximum displacements as well as the efficiency of such actuators strongly depend on the mechanical parameters of the combined electrode-elastomer-electrode layer, mainly effective Young's modulus E and residual stress &sgr;. We report measured E and &sgr; obtained from bulge tests on PDMS membranes for two PDMS brands and for several different curing methods, which allows tuning the residual stress by controlling the rate of solvent evaporation. Bulge test measurements were then used to study the change in membranes' mechanical properties due to titanium ion implantation, compared to the properties obtained from depositing an 8 nm thick gold electrode. At the doses required to create a conductive layer, we find that the Ti ion implantation has a low impact on the membrane's overall rigidity (doubling of the Young's modulus and reducing the tensile stress) compared to the Au film (400% increase in E). The ion implantation method is an excellent candidate for DEAs' electrodes, which need to be compliant in order to achieve large displacements.

Ionic polymer transducers (IPT), sometimes referred to as artificial muscles, are known to generate a large bending strain and a moderate stress at low applied voltages. Bending actuators have limited engineering applications due to the low forcing capabilities and the need for complicated external devices to convert the bending action into rotating or linear motion desired in most devices. Recently Akle and Leo (2006) reported extensional actuation in ionic polymer transducers. Model prediction indicates that such actuators can produce strain up to 10% and a blocked stress up to 20MPa under a +/- 2V applied electric potential. Compared to other smart materials, IPT is a flexible membrane and it has a reliability of over one million cycles. In this work novel extensional IPT actuators are developed for the purpose of increasing the overall displacement of the actuator. The electromechanical coupling is measured and a correlation of the experimental data with the active areas model by Akle and Leo (2006) and the numerical electromechanical model by Wallmersperger and Leo (2004) are presented. The coupling between each test case with the model parameters enables further understanding of the physical actuation phenomena as the role of diffusion of ions and diluents and the electrostatic forces between the charged species. In this study the displacement of an extensional ionic polymer transducer is measured and compared to the bending of the same IPT actuator. The bending strain is measured to be approximately 2.5%, while the extensional strain for the same ionomer is in the order of 17.5%. Finally an interesting behavior, reported for the first time is the steady expansion of the IPT sample due to the application of a symmetrical sine wave. This indicates that charge accumulation is occurring at the electrode.

Conjugated polymers have promising applications as actuators in biomimetic robotics and bio/micromanipulation. For these applications, it is highly desirable to have predictive models available for feasibility study and design optimization. In this paper a geometrically-scalable model is presented for trilayer conjugated polymer actuators based on the diffusive-elastic-metal model. The proposed model characterizes actuation behaviors in terms of intrinsic material parameters and actuator dimensions. Experiments are conducted on polypyrrole actuators of different dimensions to validate the developed scaling laws for the quasi-static force and displacement output, the electrical admittance, and the dynamic displacement response.

In this paper, a self-sensing McKibben actuator using dielectric elastomer sensors is presented. Fiber-reinforced cylindrical actuators offer one potential solution to the low-force output problem that plagues many artificial muscle actuators. Placing a cylindrical dielectric elastomer sensor in direct contact with the inner surface of the McKibben actuator facilitates in situ monitoring of actuator strains and loads. The deformation of the McKibben actuator and hence the cylindrical dielectric elastomer sensor results in a change in the electrical signal read from the electroded surfaces of the dielectric elastomer. In this paper, we present a model for predicting the response of fiber reinforced cylindrical constructs (McKibben actuators) that are actuated by an inflation pressure, which is used to support an axial load. The model is based on Adkins and Rivlin's large deformation model for the inflation and contraction of tubes reinforced with inextensible fibers. In this model, the McKibben actuator is considered as a surface of revolution since the initially near cylindrical shape is nearly always compromised during mechanical loading. A series of experiments measuring the force versus contraction behavior of the actuators are used to validate the numerical model. The material constants for an Ogden model were determined by uni-axial extension of cylindrical samples. A comparison of the numerical and experimental results shows that the correlation is good. The model enables a number of key analyses such as the effect of the braid angle and the tension generated in the fibers.

This paper presents a method for creating a smart Dielectric Elastomer Actuator (DEA) with an integrated extension sensor based on resistance and voltage measurement. Such a sensor can reduce cost, complexity, and weight compared to external sensor solutions when used in applications where external sensing is difficult or costly, such as Micro-Electro- Mechanical Systems (MEMS). The DEAs developed for integrated feedback are 20mm by 70mm and 30 &mgr;m thick double layer silicone-dielectric actuators with reinforcing silicone ribs. Loose-carbon-powder electrodes produced the best electrical and mechanical characteristics out of several possibilities tried. Electrically isolated circuits were used to measure electrode resistance and driving voltage. These parameters were then related to experiment using a model to predict DEA length. An offline regression method was used to fit the model to within 2% of the full sensor range and the results were verified experimentally. The sensor feedback inaccuracy immediately after a position step disturbance was shown to be around 20% of the full sensor range. This improved over 5 seconds to less than 5% as the transient creep effects in the silicone membrane that introduced the initial inaccuracy decayed. Long term creep reduced the accuracy of the model, necessitating periodic retraining of the sensor. Overall the sensor-estimated extension shows a very good qualitative or 'shape' match with the actual extension in the system.

From the observation of the measured frequency response, the electrical impedance of IPMC has the characteristics of a distributed parameter system. Especially in the case of TEA ion, we found that the frequency response cannot be approximated by a simple ideal capacitor or even by low-order transfer functions. In this study, we discuss a black-box circuit modeling of the electrical system of IPMC from the point of view of the frequency response. We employ some models whose transfer functions are not rational. One of such models is a distributed circuit (transmission line). Another is a black-box circuit model with a distributed parameter element (constant phase element). Both transfer functions consist of square root of 's'. In the experiment, the electrical impedance of an IPMC (gold plated Nafion) is measured under some conditions such as electrode clamp sizes and two cation species, Na ion and TEA ion. From the result, we found that the electrode clamp condition less affects the measured impedance. However, we observed that the impedance highly depends on the cation species. From the experimental frequency response, the parameters of the model are identified. Larger resistance and smaller capacitive element are identified in TEA case than those in Na case. The identified parameters are consistent with the physical intuition that TEA ion movement is slower than Na ion.

pH-sensitive hydrogels are capable of reversibly converting chemical energy into mechanical energy and therefore they are widely used as sensitive materials for pH sensors. However nonlinear effects such as hysteresis and drift are observed in the swelling behaviour of the polyelectrolytic hydrogels complicating the calibration procedure for the pH sensor and affecting the signal reproducibility. In the present work, in order to realize a pH sensor with a high signal reproducibility and high long-term stable sensor sensitivity, the complicated kinetics of gel swelling/deswelling processes is analysed and the origin of the hysteresis nonlinearities is elucidated. It is found that the long-time drift in the sensor characteristic is caused by the drift of hydrated ions and water into the gel or out of the gel in dependence on the pH range of the solution and on the chemical reactions which occur in the gel during the swelling or shrinking processes. The rate of the water drift is determined by the change rate of the concentration of ionized groups which increase the gel hydrophilicity and consequently the gel swelling.

An electric active polymer (EAP) using a dielectric elastomer is superior in the points of view of generated stress and strain, response velocity, and energy efficiency. On the other hand, it is well known that a high polymer material has creep properties. There is no research about creep of a dielectric elastomer actuator (DEA) as far as we know. It is necessary to get a clear grasp of the creep properties of a DEA in order to design a DEA. The purpose of our research was to investigate the creep characteristics and propose a mechanism of a DEA that can generate a large displacement without creep deformation. At first, a sample element of a DEA was made and tested. As a result, it was found that creep deformation was generated and accumulated by the repeated actions. Secondly, an element structure of a DEA was proposed. The element had two driven areas on opposite sides and these two areas are actuated alternately. Therefore, the proposed element worked as a vibration element. The repeated fatigue tests of the proposed vibration element gave proof of the effectiveness against creep deformation. At last, a unit mechanism of a DEA was proposed. The proposed unit mechanism was a combination of the vibration element and a ratchet mechanism. Through a performance test of the proposed experimental unit mechanism, it was confirmed that the mechanism was able to be driven and the transport velocity was changed by changing the drive frequency of the vibration element.

Nowadays, the bottleneck of the fabrication of hybrid microsystems is the assembling phase of microscopic components. Indeed, at microlevel, as a result of the high surface to volume ratio, superficial forces become dominant with respect to other ones and the development of new handling techniques is strongly required. In this context, innovative handling systems have been studied at ITIA. The possibilitiy of controlling and exploiting the capillary force has been investigated and an original handling system, based on capillary force, has been conceived. The theoretical studies led to the development of a first prototype of a gripper with variable curvature and the results obtained from this prototype encouraged the development of a smaller prototype, able to manipulate objects with weight of the order of milligrams. Regarding the actuation system of such a gripper, smart materials seemed to be required. Specifically, a novel configuration based on electroactive polymers (EAP) has been conceived. A feasibility study to evaluate their functionality and performances, as actuation system, has been carried out and the results are presented in this paper.

The Ionic Polymer Metal Composite (IPMC), an electro-active polymer, has many advantages including bending actuation, low weight, low power consumption, and flexibility. These advantages coincide with the requirements of flapping-wing motion. Thus, IPMC can be an adequate smart material for the generation of the flapping-wing motions. In this research, a flapping actuator module operated at the resonant frequency is developed using an IPMC actuator. First, IPMC actuators are fabricated to investigate the mechanical characteristics of IPMC as an actuator. The performances of the IPMC actuators, including the deformation, blocking force and natural frequency, are then obtained according to the input voltage and IPMC dimensions. Second, the empirical performance model and the equivalent stiffness model of the IPMC actuator are established. Third, flapping actuator modules using the first resonance frequency are developed, and their flapping frequency and stroke characteristics are investigated. Fourth, adequate flapping models for a flapping actuator module are selected, and dimensional data such as wing area and wing mass are obtained. Finally, the flapping actuator module is designed and manufactured to adjust the flapping models and its performance is tested. Experimental results demonstrate the potential IPMC has for use as a flapping actuator.

We present a novel linear actuator made from a single Ionic Polymer-Metal Composite (IPMC) strip. In its simplest form the device activates into the shape of a double-clamped buckled beam. This structure was chosen following observation of the buckle failure modes of axially compressed beams. The practical realization of this device is made possible by the development of new manufacturing techniques also described. The benefit of this buckled beam structure is that bending moments in the two halves of the beam cancel each other out. As a result, only one bending actuator is needed to form a single linear actuator and there is no need for mechanical joining of separate actuators - a disadvantage of previous linear actuator designs. The non-rotating nature of the end fixing in the double-clamped buckled beam also means that joining multiple elements to increase displacement or force is trivial. We present initial experimental results of a single linear actuator and a balanced, pair-connected linear actuator.

The Ionic Polymer Metal Composite (IPMC) is an Electroactive Polymer (EAP) capable of soft sensing as well as soft actuation under low driving voltage. Typically, the transduction model includes two resistors and two capacitors, which primarily accounts for the effective electrodes on the surface of the IPMC (top and bottom). There is a resistor placed between the two RC circuits to account for material between the electrodes and the resistance due to ion migration through the polymer matrix. In this paper we report our recent effort on IPMCs in connection with the application in energy harvesters. The experiments conducted use IPMC samples with various lengths, various widths and various thicknesses, and compare the charging rates of the different transducer sizes. The experimental results clearly indicate that IPMCs are attractive applicants for energy harvesting.

A sensor-actuator coupled device was developed using solid polymer electrolyte membrane (SPM) as an active tracheal tube for ventilator. Active tracheal tube is a novel type of tube for ventilator that removes patient's phlegm automatically upon sensing the narrowing of trachea by phlegm. This type of active tube is extremely useful in clinical settings as currently the sole measure to remove phlegm from patient's tube is to do it manually by a nurse every few hours. As SPM works both as a sensor and an actuator, an effective compact device was developed. SPM based sensor-actuator coupled device was fabricated with modified gold plating method. Prepared SPM was fixed as an array on a plastic pipe of diameter 22 mm and was connected to a ventilator circuit and driven by a ventilator with a volume control ventilation (VCV) mode. SPM was connected both to a sensing unit and an actuation unit. Generated voltage developed by the membrane with the setting of the maximum pressure from 5 cmH₂O to 20 cmH₂O was in order of several hundred &mgr;V. SPM sensor demonstrated a biphasic response to the ventilator flow. The sensor data showed nearly linearly proportional voltage development to the intra-tracheal pressure. The sensed signal was filtered and digitized with an A/D converting unit on a PC board. A real time operating program was used to detect the sensed signal that indicates the narrowing of trachea. The program then activated a driving signal to control the actuation of the membrane. The signal was sent to a D/A converting unit. The output of the D/A unit was sent to an amplifier and the galvanostat unit which drives the membrane with constant current regardless of the change in the load. It was demonstrated that the sensor-actuator unit detects the narrowing of trachea within several hundreds milli-seconds and responds by actuating the same membrane with the driving voltage of 3-4 V and driving current of several hundred milli-ampere for each membrane. SPM array actuated the obstructing material of 2 g to expel from the trachea tube. Also, a theoretical model of the propagating wave generated by SPM was examined.

Conducting polymers are becoming viable engineering materials and are gradually being integrated into a wide range of devices. Parallel efforts conducted to characterize their electromechanical behavior, understand the factors that affect actuation performance, mechanically process films, and address the engineering obstacles that must be overcome to generate the forces and displacements required in real-world applications have made it possible to begin using conducting polymers in devices that cannot be made optimal using traditional actuators and materials. The use of conducting polymers has allowed us to take better advantage of biological architectures for robotic applications and has enabled us to pursue the development of novel sensors, motors, and medical diagnostic technologies. This paper uses the application of conducting polymer actuators to a biorobotic fin for unmanned undersea vehicles (UUVs) as a vehicle for discussing the efforts in our laboratory to develop conducting polymers into a suite of useful actuators and engineering components.

While Electroactive Polymer Artificial Muscle (EPAM) has been presented extensively as a solution for actuation and generation technology, EPAM technology can also be used in multiple novel applications as a discrete or integrated sensor. When an EPAM device, an elastic polymer with compliant electrodes, is mechanically deformed, both the capacitance of the EPAM device, as well as the electrode and dielectric resistance, is changed. The capacitance and resistance of the sensor can be measured using various types of circuitry, some of which are presented in this paper. EPAM sensors offer several potential advantages over traditional sensors including operation over large strain ranges, ease of patterning for distinctive sensing capabilities, flexibility to allow unique integration into components, stable performance over a wide temperature range and low power consumption. Some existing challenges facing the commercialization of EPAM sensors are presented, along with solutions describing how those challenges are likely to be overcome. The paper describes several applications for EPAM sensors, such as an integrated diagnostic tool for industrial equipment and sensors for process and systems monitoring.

The large strain, high elastic modulus, and easy processing of P(VDF-TrFE-CFE) electrostrictive terpolymer make it very attractive to replace low strain piezoceramics and piezopolymers in many applications with much improved performance. In this paper, a compact polymer actuator is developed utilizing the electrostrictive terpolymer, which is suitable for full page Braille Display and graphic display. Key issues related to the reliability of electroactive polymers used in the compact actuators and for the mass fabrication of these polymer actuators are investigated. Making use of a recently developed conductive polymer, a screen printing deposition method was developed which enables direct deposition very thin conductive polymer electrode layer (< 0.1 &mgr;m) with strongly bonding to the terpolymer surface and short fabrication time. It was observed that the thin conductive polymer electrodes lead to the self-healing of the polymer after electric breakdown. An EAP compact Braille actuator was designed and fabricated with these terpolymer films wound on a spring core. The test results demonstrate that the EAP Braille actuator meets all the functional requirements of actuators for refreshable full Braille display, which offers compact size, reduced cost and weight.

Twist-spun carbon nanotube yarns actuate when extra charge is added to the yarn. This charge can be stored in a doublelayer capacitor formed when the yarn is submersed in an electrolyte. The dependence of the actuation stress and strain on the stored charge must be studied if double layer charging models are to be fully verified over large potential ranges. However, background currents are generated in the system when an electrical potential is applied, making it hard to discern the charge stored in the actuator and the charge that passes through the cell due to faradaic processes. A model is developed to separate the capacitive and faradaic portions of the actuator current. The model is then applied to the analysis of the actuation data. The consistency of the results paves the way to understanding the real strain-charge behavior of the actuator.

We have used inkjet printing to deposit silver conducting lines and small PEDOT (conducting polymer) sensors onto fabrics. The printed conductors penetrate into the fabric and can be shown to coat the individual fibers within the yarn, through the full thickness of the cloth. The PEDOT sensor has a resistance in the region of a few kilo-ohms and is connected to measuring equipment by printed silver lines with a resistance of a few ohms. In this way, local strains can be measured at different sites on a fabric. The PEDOT responds to a tensile strain by a reduction in resistance with a gauge factor (change in resistance/strain) from -5 to -20. This compares with conventional strain gauges where the gauge factor is normally +2. These sensors cycle to strains of over 10%. We have measured gauge factors as a function of the orientation of the sensing line to the fabric axes, to the strain axes for different fabric structures. We can correlate the gauge factor with the extent to which the twisted multifilament yarns are expected to become laterally compressed. In preliminary tests we have shown that these printed sensors can be used to monitor knee and wrist motions and so could be used to provide information in applications such as rehabilitation from joint damage.

The ability of conducting polymer actuators to convert electrical energy into mechanical energy is influenced by many factors ranging from the actuators physical dimensions to the chemical structure of the conducting polymer. In order to utilise these actuators to their full potential, it is necessary to explore and quantify the effect of such factors on the overall actuator performance. The aim of this study is to investigate the effect of various geometrical characteristics such as the actuator width and thickness on the performance of tri-layer polypyrrole (PPy) actuators operating in air, as opposed to their predecessors operating in an appropriate electrolyte. For a constant actuator length, the influence of the actuator width is examined for a uniform thickness geometry. Following this study, the influence of a varied thickness geometry is examined for the optimised actuator width. The performance of the actuators is quantified by examination of the force output, tip displacement, efficiency as a function of electrical power and mechanical power, and time constant for each actuator geometry. It was found that a width of 4mm gave the greatest overall performance without curling along the actuator length (which occurred with widths above 4mm). This curling phenomenon increased the rigidity of the actuator, significantly lowering the displacement for low loads. Furthermore, it was discovered that by focussing a higher thickness of PPy material in certain regions of the actuators length, greater performances in various domains could be achieved. The experimental results obtained set the foundation for us to synthesize PPy actuators with an optimised geometry, allowing their performance to reach full potential for many cutting applications.

Electroactive polymers, Nafion and Flemion, have been widely investigated as actuator materials due to their good performance, such as light weight, good flexibility, low actuation voltage, large strain. However, less research work has been done on the sensing behaviors of these materials. In this work, we design and fabricate a tactile sensor based on Flemion with water as solvent. Several mechano-electro relationships were obtained when different mechanical input pulses were applied. According to the experiment results, Flemion-based composite could survive much longer time as sensor materials than that as actuator materials in air. By proper design and fabrication, a tactile sensor for potential three-dimensional sensing could be achieved based on this material. Electroactive based polymers would be a good candidate for bio-related sensors especially for artificial derma applications.

We present an electrically tunable diffraction grating, driven by thin-film dielectric elastomer actuators. The device combines the advantages of dielectric elastomer actuators, capable of generating very large strains, with the desirable properties of Micro-Opto-Electro-Mechanical Systems (MOEMS). The soft materials based tunable diffraction grating achieves a continuous grating period change of 19.2%, when a voltage of 500 V is applied. This is an improvement by a factor of 90 compared to conventional analog tunable diffraction gratings based on hard materials. Further device characterization yielded a tunable angular range of more than 100 mrad. Additionally, we show that in combination with a collimated white light source (e.g. white light emitting diode), the discussed tunable diffraction grating can be used for wavelength-adjustable luminous sources. Integrated into displays, these light sources could facilitate the first technology able to reproduce all perceivable colors.

Adaptive structures are capable to change their shape in a smart way in order to "adapt" to variable external conditions. Active shell structures with large out-of-plane deformation potential may be used to generate an interaction between the structural shape and the environment. Exemplarily, such shell-like actuators may be utilized for the propulsion of vehicles through air or water. Among the electroactive polymers (EAPs) especially soft dielectric EAP are promising for driving shell-like actuators due to their huge active strain potential and intrinsic compliancy. The challenging task of this study was to explore the potential of the DE actuator technology for the design of shell-like actuators with the ability to perform complex out-of-plane deflections. We present and evaluate concepts for the design of active shell structures driven by soft dielectric EAP. Preliminary experiments were conducted for selected approaches in order to basically verify their principle of operation and to quantify their active out-of-plane deformation potential. These experiments showed that the so-called agonist-antagonist configuration, where pre-strained DE films are attached on both sides of a hinged backbone structure, holds good performance in terms of active out-of-plane deflections and forces.

Extremely large, lightweight, in-space deployable active and passive microwave antennas are demanded by future space missions. This paper investigates the development of PVDF based piezopolymer actuators for controlling the surface accuracy of a membrane reflector. Uniaxially stretched PVDF films were poled using an electrodeless method which yielded high quality poled piezofilms required for this applications. To further improve the piezoperformance of piezopolymers, several PVDF based copolymers were examined. It was found that one of them exhibits nearly three times improvement in the in-plane piezoresponse compared with PVDF and P(VDF-TrFE) piezopolymers. Preliminary experimental results indicate that these flexible actuators are very promising in controlling precisely the shape of the space reflectors. To evaluate quantitatively the effectiveness of these PVDF based piezopolymer actuators for space reflector applications, an analytical approach has been established to study the performance of the coupled actuator-reflector-control system. This approach includes the integration of a membrane reflector model, PVDF piezopolymer actuator model, solution method, and shape control law. The reflective Newton method was employed to determine the optimal electric field for a given actuator configuration and loading/shape error.

In this paper the worldwide first EAP actuated blimp will be presented. It consists of a slightly pressurized Helium filled body of a biologically inspired form with Dielectric Elastomer (DE) actuators driving a classical cross tail with two vertical and horizontal rudders for flight control. Two versions of actuators will be discussed: The first version consisted of "spring-roll" type of cylindrical actuators placed together with the electrical supply and control unit in the pay load gondola. The second version consisted of a configuration, where the actuators are placed between the control surfaces and the rudders. This novel type of EAP actuator named "active hinge" was developed and characterized first in the laboratory and afterwards optimized for minimum weight and finally integrated in the blimp structure. In the design phase a numerical simulation tool for the prediction of the DE actuators was developed based on a material model calibrated with the test results from cylindrical actuators. The electrical supply and control system was developed and optimized for minimum of weight. Special attention was paid to the electromagnetic systems compatibility of the high voltage electrical supply system of the DE actuators and the radio flight control system. The design and production of this 3.5 meter long Lighter-than-Air vehicle was collaboration between Empa Duebendorf Switzerland and the Technical University of Berlin. The first version of this EAP blimp first flew at an RC airship regatta hold on 24^th of June 2006 in Dresden Germany, while the second version had his maiden flight on 8^th of January 2007 in Duebendorf Switzerland. In both cases satisfactory flight control performances were demonstrated.

In this study, we investigated the mechanical properties of various type ionic polymer-metal composites (IPMCs) and Pt, Au, Pd, and Pt electroded ionic liquid (IL-Pt) IPMCs, by testing tensile modulus and dynamic mechanical behavior. The SEM was utilized to investigate the characteristics of the doped electroding layer, and the DSC was probed in order to look into the thermal behavior of various types of IPMCs. Au IPMCs, having a 5~7 &mgr;m doped layer and nano-sized Au particles (ca. 10 nm), showed the highest tensile strength (56 MPa) and modulus (602 MPa) in a dried condition. In a thermal behavior, Au IPMC has the highest T_g (153°C) and T_m (263°C) in both the DMA and DSC results. The fracture behavior of various types IPMCs followed base material's behavior, Nafion^TM, which is represented as the semicrystalline polymer characteristic.

Data from comprehensive thermomechanical tests of shape memory polymers are reported, with specimens tested up to 75% strain and between 30-120°C temperatures. The data is analyzed and key observations are drawn. The stress/strain behavior during loading at temperatures above glass transition for the Veriflex shape memory polymer tested was linear and did not show much variation with the actual temperature. When the polymer is cooled with end constraints, thermally induced tensile stresses developed, but only after the temperature reduced below glass transition and the material stiffened. When the constraints were then released, 97-98% of the original strain was locked in. Reheating the shape memory polymer beyond the glass transition temperature resulted in shape recovery (shape memory effect). When the polymer was reheated while constraining the strain, the full recovery stress developed was about the stress the polymer was initially loaded to during deformation at high temperature. Examining the Young's modulus at elevated temperature and low temperature showed that Veriflex softened by around 40-60 times when heated through glass transition.

Electroactuated polymer (EAP) hydrogels based on JEFFAMINE® T-403 and ethylene glycol glycidyl ether (EGDGE) are used in an infusion pump based on the proprietary Pulse Actuated Cell System (PACS) architecture in development at Medipacs LLC. We report here significant progress in optimizing the formulation of the EAP hydrogels to dramatically increase hydrolytic stability and reproducibility of actuation response. By adjusting the mole fraction of reactive components of the formulation and substituting higher molecular weight monomers, we eliminated a large degree of the hydrolytic instability of the hydrogels, decreased the brittleness of the gel, and increased the equilibrium swelling ratio. The combination of these two modifications to the formulation resulted in hydrogels that exhibited reproducible swelling and deswelling in response to pH for a total period of 10-15 hours.

For military applications, the availability of safe, disposable, and robust infusion pumps for intravenous fluid and drug delivery would provide a significant improvement in combat healthcare. To meet these needs, we have developed a miniature infusion prototype pump for safe and accurate fluid and drug delivery that is programmable, lightweight, and disposable. In this paper we present techniques regarding inter-digitated IPMCs and a scaleable IPMC that exhibits significantly improved force performance over the conventional IPMCs. The results of this project will be a low cost accurate infusion device that can be scaled from a disposable small volume liquid drug delivery patch to disposable large volume fluid resuscitation infusion pumps for trauma victims in both the government and private sectors of the health industry.

Normally, various micro-scale devices adopt electromechanical actuators for their basic mechanical functions. Those types of actuators require a complicated power transfer system even for generating a tiny scale motion. Since the mechanical power transfer system for the micro-scale motion may require many components, the system design to fit those components into a small space is always challenging. Micro-optical zoom lens systems are recently popularly used for many portable IT devices such as digital cameras, camcorder, and cell phones, Noting the advantages of EAP actuators over the conventional electromechanical counterparts in terms of simple actuator mechanisms, a micro-optic device that is driven with the EAP actuator is introduced in the present work. EAP material selection, device design and fabrication will be also delineated.

Our work focuses on a contractile dielectric elastomer actuator (DEA) based on the McKibben pneumatic muscle concept. A coupled-field ABAQUS (Hibbit, Karlsson & Sorensen, Inc., USA) FEA model has been developed where the constraints of the orthotropic fibre weave and end caps of this actuator design are included. The implementation of the Maxwell pressure model that couples electrical inputs to mechanical loads using the ABAQUS user subroutine DLOAD is the focus of this paper. Our model was used to perform a study of actuator design parameters including the fibre weave angle, dielectric thickness, and the DEA's length. At a fibre angle of 45° relative to the longitudinal axis, no axial deformation was predicted by our model. A weave angle above this resulted in an axial expansion during actuation, whereas axial compression occurred if the fibre angle was less than 45°. For instance, at a fibre angle of 30° with respect to the longitudinal axis, this model predicted a compressive axial strain of 4.5% before mechanical failure for an actuator with an outer radius of 2mm, wall thickness of 0.5mm, and length of 20mm.

In-plane piezoelectric charge constant of Electro-Active paper (EAPap) was investigated based on direct and converse piezoelectric effects. EAPap samples were made with cellulose film with very thin gold electrode coated on both sides of the film. To characterize direct piezoelectricity of EAPap, induced charge was measured when mechanical stress was applied to EAPap. In-plane piezoelectric charge constant was extracted from the relation between induced charge and applied in-plane normal stress. To investigate converse piezoelectricity, induced in-plane strain was measured when electric field was applied to EAPap. Piezoelectric charge constant was also extracted from the relation of induced inplane strain and applied electric field. Piezoelectric charge constants obtained from direct and converse piezoelectricity are 31 pC/N and 178 x 10^-12m/V for 45 degree sample, respectively. Measured piezoelectric charge constants of EAPap provide promising potential as a piezoelectric material.

In this paper we investigated the actuation behavior of the antagonistically driven Dielectric Elastomer Actuators (DEAs). The motivation is to improve the viscoelastic creeping behavior that intrinsically exists within most DEAs, since creeping behavior may cause some unwanted effects to the performance of DEAs, especially when we apply the DEAs to some mechanical devices which need to operate stably for a long time. Our experimental results showed that the actuator can generate very stable displacement, make the pattern of actuator's movement more regular and take advantage of mechanical energy in a more efficient way by coating two dielectric elastomers with different area ratios and applying DC voltage to both of them at the same time.

Dielectric Elastomer Actuators (DEAs) have received considerable attention recently due to their large strains, over 100% in some cases, when subject to an electric field. Previous research yielded a large deformation quasi-static model that describes the out of plane deflections of clamped diaphragms. The numerical modeling results compare well with experimental results for the same configuration. A theoretical dynamic model has also been developed for the dynamic inflation of a spherical DEA membrane. With relevance to dynamic applications, the time varying response of dielectric elastomer membranes configured for out-of-plane deflections has not been reported until now. In this paper, an experimental investigation and analysis of the dynamic response of a dielectric elastomer membrane is reported. The experiments were conducted with DEAs fabricated from VHB 4905 films and carbon grease electrodes. The experiments covered the electromechanical spectrum by investigating membrane behavior due to (i) a voltage time varying input and (ii) a mechanical time varying input, resulting in a combined electromechanical loading state during the experiments. The results reveal that the response of the membrane is a departure from the classical dynamic response of continuum membrane structures. As a result of this work, we have identified which typical modeling assumptions are valid and hence can authentically be used to develop new dynamic predictive modeling tools.

Electrochemical actuators were fabricated based on conducting polypyrrole (PPy) and acrylic elastomer substrate. An ultrathin layer of single-wall carbon nanotubes (SWNT) was employed as the electrode for the electrochemical deposition of PPy onto the substrate. The permeability of the nanoporous SWNT layer enabled the electrolyte solution to penetrate the electrode and the polymerization of pyrrole both on the surface and at the interior of the substrate surface. The resulting PPy was intimately attached to the substrate. The two materials could not be detached by any physical means. Reversible and stable actuation has been demonstrated from the new PPy/SWNT/acrylic/SWNT/PPy bimorph structure.

Actuation of polypyrrole in aqueous sodium hexafluorophosphate solution has been shown to produce relatively large strains. However little has been published on appropriate potential range of actuation in this electrolyte. This information is clearly crucial for applications. Our particular interest is in disposable applications where a relatively small number of cycles are needed, and maximum strain is desired. The electrochemical degradation as a function of voltage is investigated by cycling the film between fixed voltages and measuring the charge transfer. The experiment was done on a glassy carbon substrate in order to reduce effects of change in resistance with oxidation state, preventing actuation. The dependence of charging on voltage and the rate of reduction in the extent of charging are measured. The voltage range for effective operation of the device was found to be -0.4 V to 0.8 V versus a Ag/AgCl reference electrode in order to achieve stable performance over at least 30 minutes. The mechanisms of degradation at potentials beyond 0.8 V appear to be the substitution of hydroxyl ions in the polymer backbone, as suggested in reports on degradation of polypyrrole in other electrolytes. An observed reduction in charge transfer rate at potentials lower than -0.4 V is consistent with a reduction in ionic conductivity at highly reduced states, as has also been suggested in the literature.

Ras Labs, L.L.C., is committed to producing a variety of electroresponsive smart materials that are strong, resilient, and respond quickly and repeatedly to electrical stimuli. By effectively combining the synthetic expertise of Ras Labs with the plasma expertise of the Princeton University Plasma Physics Laboratory (PPPL), Ras Labs, L.L.C., is committed to producing superior electroresponsive materials and actuators. One of the biggest challenges in developing these actuators was the interface between the embedded electric electrodes and the electroresponsive materal because of the pronounced movement of the electroresponsive material. Preliminary experiments explored the bonding between these electroresponsive materials with plasma treated metals provided by PPPL. The results were encouraging, with much better bond strengths in the plasma treated metals compared to the untreated control. Ras Labs is expanding upon improving the attachment of the embedded electric leads to the electroresponsive materials in these actuators using plasma treatment and other treatments to non-corrosive metal leads. Coating or encapsulating the smart material in an elastomeric material, which acts as a "skin," can allow for the actuator, even when removed from an electrolytic bath, to be fully operational. Strong, encapsulated, electroresponsive smart materials will have a profound impact on prosthetics, valves, and automated systems, particularly robotics, allowing for revolutionary designs that can move smoothly and seamlessly in three dimensions with superb control, dexterity, and durability.

Dielectric elastomers have demonstrated high energy density and high strains as well as high electromechanical efficiency and fast speeds of response. These properties, combined with their projected low cost make them attractive for a variety of actuator applications including linear actuators, diaphragm pumps, rotary motors, and haptic displays. Dielectric elastomers have also been shown to offer high energy density, high efficiency, and large strains when operated as generators. Dielectric elastomers have reached a stage of development where standardized products can be applied to new applications. In some cases, dielectric elastomer devices are improvements over existing devices. In other cases, however, dielectric elastomers can enable new types of devices that cannot be made with existing technologies, such as new types of loudspeakers and power generating devices. A new dipole loudspeaker system was developed using a commercially available push-pull diaphragm configuration. This same transducer configuration was used to develop a new power generating system. This generator system enables a power generation of 0.06 to 0.12 W by manually displacing the device by 5 to 6 mm once a second. By introducing a voltage step-down conversion circuit, the device was able to power wireless communications, allowing the control of devices separated by a distance of a few meters. These two devices are examples of the new applications that are enabled as the dielectric elastomer technology commercially emerges. Future improvements to dielectric elastomers could enable new capabilities in clean electrical power generation from ocean waves, for example.