EuroEAP platform

We report new-type of bio-machine reconstructed from the chemically cross-linked muscle protein: actin-myosin and microtubule-kinesin gels (Nanobiomachine) both fueled by an adenosine triphosphate(ATP). This might be the first man-made biomachine gels fueled by ATP.@Since these gels are originated from cytoskeleton proteins which are characterized by their high hierarchical structure with three dimensional structure, they can exhibit so-called hemergent functiong@such as self-healing, switching, memory, and self-oscillating through reversible sol-gel transition across the hierarchies which are becoming one of the central interests of life science now-a-days.

The ability to produce reversible, large-strain, bistable actuation has been a missing puzzle in the pursuit of smart materials and structures. Conducting polymers are bistable, but the achievable strain is small. Large deformations have been achieved in dielectrical elastomers at the sacrifice of mechanical strength. The gel or gel-like soft polymers generally have elastic moduli around or less than 10 MPa. The deformed polymer relaxes to its original shape once the applied electric field is removed. We will present the new, bistable electroactive polymer (BSEP) that is capable of electrically actuated strains as much as 580% (area expansion). The BSEP could be useful for constructing rigid structures. The structures can support high mechanical loads, and be actuated to large-strain deformations. Applications of the BSEP for new tranducers and systems including refreshable tactile displays will be presented.

Electronic EAPs have made tremendous progress in theory, materials, devices, and applications in the past 20 years. This talk takes a big picture look at the status and capabilities of electronic EAPs, with emphasis on dielectric elastomers. We discuss both capabilities and applications. Applications where EAPs may have unique capabilities, such as for inertial drives or compliant actuators, are of particular interest. As electronic EAPs move towards more practical use, areas which in the past may have been lower research priority for the technology have become increasingly important. These areas include packaging, electronics, environmental, lifetime, and integration aspects. Yet while these practical areas are critical, it is equally important to continue progress in the fundamental areas such as theory, new materials, and novel actuator design. Predicting the future is always a hazardous activity, but we will look into our crystal ball and attempt to identify fruitful areas, both practical and fundamental, to advance the technology in this exciting field.

Actuator materials capable of producing a rotational motion are rare and, yet, rotary systems are extensively utilized in mechanical systems like electric motors, pumps, turbines and compressors. Rotating elements of such machines can be rather complex and, therefore, difficult to miniaturize. Rotating action at the microscale, or even nanoscale, would benefit from the direct generation of torsion from an actuator material. We have discovered that the electrochemical charging of helically wound multiwall carbon nanotubes in the form of a twisted yarn generates such rotational action. Large scale rotations are produced from small voltage stimuli. The rotation angles are orders of magnitude larger than piezoelectric or shape memory alloy torsional actuators. The torsional strain, torque, speed and lifetime have been evaluated under various electrochemical conditions to provide insight into the actuation mechanism and performance. Finally, the rotating motion has been coupled to a mixer for use in a prototype microfluidic system.

special presentation on first market product of Bayer MaterialScience / Artificial Muscle Inc special presentation on first market product of Bayer MaterialScience / Artificial Muscle Inc

Ionic polymers offer low voltage operation, producing moderate strains at high stresses. Developments discussed include the demonstration of carbon nanotube yarn actuators, application of polypyrrole in catheters and the modeling of coupling and rate. Yarn actuators operate at high stresses (300 MPa), with small strains (0.5 %), and high work densities. Strains are proportional to charge density (inserted electrochemically), and charges expelled (in sensing) are proportional to load. Electromechanical coupling is modeled based on strain to charge ratio and capacitance. The mechanism of actuation may be applicable to other nanostructured materials, including carbon used in batteries. There is interest in creating active catheters, including early work in Pisa. The advantages of low voltage, moderate strain and high stresses are tempered by slow actuation, high currents and cycle limits. Existing catheters for treatment of stroke are disposable and can take more than 1 hour to position, and thus a device that can guide the tip to speed placement is useful. Polypyrrole actuators achieve the mechanical deformation needed. The remaining challenge is to encapsulate them. Since actuation is slow, understanding and modeling rate limiting mechanisms is important. Strain is proportional to charge, and thus electronic and ionic transport determine rate. Transmission line models are shown to be effective at describing the response. Making electrodes more porous speeds charging.

Dielectric elastomers offer the potential of efficient energy harvesting with little added mass and few moving parts. Electric power can be produced by stretching and contracting a relatively low-cost rubbery material. This high efficiency and high energy density, combined with simplicity and low cost, suggests that dielectric elastomers may be promising for a wide range of energy harvesting applications. Dielectric elastomers have shown the ability to harvest energy from energy sources as diverse as human walking, ocean waves, flowing water, and blowing wind. Challenges remain in order for dielectric elastomers to realize their full potential, including the development of materials and transducer configurations that can sustain long lifetime in severe environmental conditions as well as system issues such as practical and efficient energy harvesting circuits and mechanical interfaces and transmissions. Progress has been made in these areas that suggest that the challenges can be overcome. Energy harvesting transducers have operated over 5 million cycles. Dielectric elastomer material has been shown to survive for months underwater while undergoing voltage cycling. Circuits capable of 78% energy harvesting efficiency have been demonstrated. Scaling up to the power levels required for providing renewable energy to the power grid or for local use will likely require further development and include implementation strategies such as fault tolerance.

Relaxor ferroelectric EAPs have been developed by modifing poly(vinylidene fluoride-co-trifluoroethylene) copolymers using molecular engineering. The unique EAPs have high dielectric constant above 50 at room temperature and can be processed into thin film with thickness below 5 microns as semicrystalline thermoplastic polymers. This EAP family materials combine high stress (modulus above 300 MPa) and high strain response (>3%) and can be driven at low voltage. They are currently under development for a broad applications such as high energy density film capacitors, advanced actuators, and unconventional electrocaloric cooling devices.

There is a need for devices that can allow a dialog between electronics and cells in tissue or culture. Since cells are soft, wet and respond to chemical signals while electronic devices are hard and dry, bionic devices will be more like soft batteries than like any conventional device. This talk will discuss the processing methods, gel mechanical properties and transport properties of small and large molecules. In processing we have used inkjet printing and extrusion methods to form gels based on epxoy-amine chemistry, on photocured acrylates and in self-assembled polyelectrolytes. This last group of gels can only be made by layerwise processes and have strange and interesting properties. To enhance mechanical strength, we have been studying elastic-fiber reinforced gels which have excellent strength and toughness. To transport chemical signals, most gels will allow diffusion of small molecules but careful design will be needed to allow proteins to diffuse through gels. Finally these properties will be discussed in the context of forming a bionic device with flexible electrodes embedded in an active gel.

Subject to a voltage, a membrane of a dielectric elastomer reduces thickness and expands area, possibly straining over 100%. The phenomenon is being developed as transducers for broad applications, including soft robots, adaptive optics, Braille displays, and electric generators. This talk reviews the theory of dielectric elastomers, coupling large deformation and electric potential. The theory is developed within the framework of continuum mechanics and thermodynamics. The theory attempts to answer commonly asked questions. How do mechanics and electrostatics work together to generate large deformation? How efficiently can a material convert energy from one form to another? How do molecular processes affect macroscopic behavior? The theory is used to describe nonlinear and nonequilibrium behavior, such as electromechanical instability and viscoelasticity. It is hoped that the theory will aid the creation of soft active materials and soft machines. This talk is based on a recent article: Zhigang Suo, Theory of dielectric elastomers, http://www.seas.harvard.edu/suo/papers/243.pdf.

Skeletal muscles are strengthened by training or repeat exercise. Electrochemomechanical deformation (ECMD) of conducting polymers also shows training or learning effect. Namely, the stroke of ECMD (strain) increases by repeat cycle of electrochemical oxidation and reduction. The training effect is due to (1) increase in the electrochemically activity of the film, (2) anisotropic deformation by high tensile loads, which results from creeping. The elongated film by creeping, which is induced by electrochemical cycle under high tensile loads, can be retained at the oxidized state. The retention results from the ionic cross link between polycations of conducting polymer. The retained shape can be relaxed to the original shape by removal of tensile stress and several electrochemical cycles (recover of creeping).

Liquid crystal elastomers (LCEs) are remarkable materials that combine orientational ordering of liquid crystals with the elastic properties of polymer networks [1]. This coupling is responsible for large reversible thermo-mechanical response of monodomain samples, with possible applications in the fields of actuation and mechanically tunable optics. One of the most important physical properties of monodomain LCEs is the orientational ordering of constituent molecules. The local orientational order can easily be determined by deuterium nuclear magnetic resonance (DNMR), since the measured frequency splitting is directly proportional to the order parameter. However, this requires deuterated LCEs, a problem avoided by doping the samples with conventional liquid crystal such as 8CB [2]. In this work we investigate the ordering behavior of three building blocks of LCE: mesogen, crosslinker and comonomer. Three chemically equivalent samples with selectively deuterated mesogen, crosslinker and comonomer, respectively, were prepared. The corresponding DNMR spectra reveal that the ordering of deuterated mesogen is similar to the order of doped samples investigated previously, whereas the crosslinker and comonomer moieties exhibit lower orientational ordering. [1] Warner M., Terentjev E. M., Liquid Crystal Elastomers, Clarendon Press, Oxford, 2003. [2] Lebar A., Kutnjak Z., Zumer S., Finkelmann H., Sanchez-Ferrer A., Zalar B., Phys. Rev. Lett., 94 (2005) 197801-197803.

Dental implants have been widely utilized in clinical treatments since they can integrate or bond with the alveolar bone almost similar to natural teeth. The wide use of the implants has also been prompted by its esthetic appearance, as well as from a clinical viewpoint on minimal invasion to healthy tooth tissue. However, an excessive stress due to the occlusal force applied to the implant can reportedly cause damage or defect at the interface between the implant and the bone, and the structure of implant including an artificial tooth. Hence, it is important for the implant to mimic a natural tooth with periodontal membrane or periodontal ligament (PDL) that essentially connects a tooth and the bone. The PDL has two important functions related to mechanical stimulus, shock absorber or cushion effect, and sensory nerve which can detect the force applied to the tooth. To mimic a natural tooth, the authors fabricated a new implant model with an artificial PDL. This model consisted of a fixture or an implant body, an abutment made of stainless steel, an artificial tooth, and an artificial PDL made of a polyvinylidene fluoride (PVDF) film mounted between the fixture and abutment. To characterize the model, we measured the electromechanical behavior of PVDF film under impact force by dropping an impactor onto an artificial tooth, and examined the correlation between the peak voltage and the mass or height of the impactor to study the PVDF film as an artificial PDL.

The thickness vibrations of an infinite periodic laminate made out of two alternating layers of dielectric elastomers is studied. The laminate is pre-stretched by inducing a bias electric field along its thickness. Incremental time-harmonic fields superimposed on the initial finite deformation are considered next. Utilizing the Bloch-Floquet theorem along with the transfer matrix method the dispersion relation which relates the incremental fields frequency and the Bloch-parameter is determined. Ranges of frequencies for which the Bloch-parameter is complex are termed band-gaps, as waves with these frequencies cannot propagate. Abstract The Band-gap diagram depends on the phases properties, their volume fraction, and most importantly the electric bias field. Numerical investigation of the resulting equation demonstrate how these band-gaps can be shifted and their width can be modified by changing the bias electric field. The latter implies how by a suitable choice of the electrostatic field one can filter desired frequencies over the whole spectrum. Finally, a representative example of a laminate made out of an alternating layers of VHB 4910 and fluorosilicone 730 is evaluated. Keywords: electroactive polymers; dielectric elastomers; band-gaps; finite deformations; soft actuators; non-linear electroelasticity;

Polypyrrole (PPy) as electroconductive polymer has potential in applications as sensors, flexible points in electronic devices, electromagnetic shielding, artificial muscles etc. From the application point of view is good to know its degradation of electroactivity and thus its lifetime of usability. We chemically synthesized PPy with different oxidants and dopants, namely FeCl3, FeCl3.6H2O, Fe2(SO4)3, (NH4)2S2O8 and FeCl3 + DBSA. The degradation of DC conductivity with time was followed by X-ray photoelectron spectroscopy and related to the increase of oxygen species on the surface, change of chemical states of anions and the ratio anions/N+. Furthermore the disruption of the Pi-conjugated system was followed by D-parameter of 1st differential of Auger CKLL peak [Turgeon S., Paynter R.W. Thin Solid Films 394 (2001), 44-48].

This paper describes the use of a tubular dielectric electro-active polymer (DEAP) actuator for active vibration isolation. The DEAP tubular push actuator developed by Danfoss PolyPower A/S has been used. First, the characteristics of the actuator are examined. It is seen that the actuator is inherently non-linear, involving an approximately quadratic relationship between excitation and extension. Next, it is seen that internal resonances in the actuator limit the bandwidth over which it can be used for active control (to 75 Hz or so). The potential for active vibration isolation is then explored. The dynamic performance is limited by the potential bandwidth, the inherent nonlinearity, the maximum force that can be generated and the maximum range of movement. Performance for tonal disturbances is investigated experimentally within an adaptive feedforward control scheme. Attenuation of 57dB of the excitation frequency is achieved but compensation is required to avoid increase in the higher harmonics introduced by the actuator nonlinearity. In an alternative approach adaptive control is applied not only at the harmonic of the disturbance but also at twice that frequency, to suppress the harmonic distortion introduced by the nonlinearity. In this case the first harmonic is reduced by 52dB and the second harmonic by 3dB. Isolation in response to a band-limited random input is then demonstrated, with attenuation of 19dB being achieved over a frequency range from 2-8 Hz.

Dielectric elastomer stack actuators (DESA) are well suited for the use in mobile devices, fluidic applications and small electromechanical systems. Despite many improvements during the last years the long term behaviour of dielectric elastomer actuators in general is not known or has not been published. In a first step we have characterized the lifetime under laboratory conditions to identify potential factors influencing lifetime. From first results we conclude that lifetime of these actuators is mainly influenced by the conductive material between feeding line and multilayer electrodes. So far, actuators themselves are not affected by long term actuation. With the best contact material actuators can be driven for more than 500 hours at 200 Hz with an electrical field strength of 20 V/µm. Now, the characterization is continued under controlled climatic conditions. We have examined the actuators at constant elevated climatic conditions for several months. Additionally, actuators were exposed to climatic profiles ranging from -20°C to 80°C and from 10% r.h. to 90% r.h., respectively. The first results show that the electrical properties of the actuators are influenced by temperature and humidity. Nevertheless, the preliminary results show no evidence that whether elevated temperature nor humidity limit the lifetime of the actuators.

Implementation of perception in mobile robot has been a major challenge for many research teams. Recently a lot of efforts have been devoted to biomimetic perception system. Since electro active polymer (EAP) actuators are realizing motions and sensing similar to natural muscles they are very attractive as artificial muscle for biomimetic perception system in robot. Moreover electronic conducting polymers based actuators with Interpenetrating Polymer Networks (IPNs) architecture are promising technology because of their many advantageous properties as low working voltage, soft, noiseless, light weight and high lifetime (several million cycles). Our laboratory recently synthesized new conducting IPN actuators based on high molecular weight nitrile butadiene rubber, poly(ethylene oxide) derivative and poly(3,4-ethylenedioxithiophene). The presence of the elastomer greatly improves the actuator/sensor performances such as mechanical resistance and output force. In this poster we present the actuator/sensor synthesis, characterizations and design allowing their integration in two biomimetic perception systems an eye vision system and an artificial whisker system. First vision and whisker prototypes with fully controlled actuator position and sensory feedback will be presented.

Danfoss PolyPower A/S have applied their EAP film technology to three configurations of sensor. The configurations measure stroke, surface strain and pressure distribution and all benefit from the elasticity of the material and its electrodes. This poster illustrates the three configurations and describes the value that PolyPower film brings to applications that require these types of sensor.

Design and manufacture of DEAP based devices used for energy harvesting is a challenging multidiscipline task. Research has predominately focused on small scale proof of concept designs and human powered size devices. Methods for scaling from the proof of concept size into large scale DEAP devices are addressed. DEAP material properties for energy harvesting applications are established. Results of the mechanical and electrical characterization of large scale DEAP energy harvesting devices are presented. Manufacturing and quality controls concepts used by Danfoss PolyPower for large scale energy harvesting are presented.

Intrinsically Conducting Polymers are emerging materials which provide a huge interest for a great number of applications. These materials are already being employed in electronic capacitors, polymer light emitting displays, through-hole metallization of multilayer printed circuit boards (PCBs), and transparent antistatic coatings for insulating substrates. Nowadays, new emerging applications are being studied such as electroactuators, all-polymer electrochromic devices and organic solar cells, among others. This work illustrates a success history in the emerging field of Organic Electronics: the use of an ElectroActive Polymer for the construction of flexible, large-area pressure sensors; technology developed and patented by the presenting authors [PCT/ES2006/000398]. Previous technologies employed metallic microparticles embedded in a polymer film or metallic central films separated by an elastomeric polymer film. Since high cost materials are unviable for large surface/large scale applications, our work was focused on the use of a piezoresistive polymer thin film in order to develop low-cost, all-plastic, flexible and large-area pressure sensors. The technology shows great advantages for application on high surface area. At this moment, the technology is being applied in robotics; there is an increasing interest in this application due to the advances in the capability of adding intelligence with powerful low cost electronic devices.

Quincke rotation is the rotation of non-conducting objects immersed in liquid dielectrics and subjected to a strong homogeneous DC electric field. The rotation is spontaneous when the field exceeds a threshold value. Wide range of applications (e.g. microscopic motor) motivates researchers to find materials with micro-fabrication possibilities. Polymer composites that fulfill these requirements have been developed. Electro-rotation of disk shaped polymer composites is studied as a function of electric field intensity. Based on the polymer Quincke rotor, a totally new class of material is expected to be designed.

During the past decade, tremendous progress has been accomplished in the field of EAP research by a worldwide community. However, up to now, the practical usage of dielectric EAP actuators in consumer products has yet to be demonstrated. Some of the issues that have prevented the adoption of this technology by product manufacturers are the high driving voltages, the viscoelastic behaviour of the used elastomers, and the slow response speed. Over the past two years Optotune AG has extensively worked on developing a dielectric EAP technology combining low actuation voltage (300V), fast response time (<1ms), and high reliability (>4 billion cycles at full voltage). With this know-how, Optotune developed a laser speckle reducer (LSR) which drastically reduces the speckle contrast in Laser-based projection systems (speckle contrast <2.5%). An electronic driving system integrated in the packaging leads to a compact ø41mm x 8.8mm design with a standard 5V micro-usb connector as power supply for the device. A miniaturized version of the LSR with an overall size of 9.8 x 6.3x 1.1 mm3 (without electronics) was also developed and paves the way for the development of miniaturized handheld picoprojectors.

The future success of dielectric elastomer materials in actuator technology as well as in energy harvesting critically depends on the material parameters, e.g. breakdown field, dielectric constant, and elastic modulus. They have a direct impact on the driving voltage which should be as low as possible. By increasing the dielectric constant of a material, this voltage can be decreased. The increase of dielectric constant, however, is often associated with an unwanted decrease in the breakdown field. In this presentation, dielectric elastomer materials with increased dielectric constant and high breakdown fields are presented.

Dielectric elastomer stack actuators (DESA) promise breakthrough functionality in user interfaces by enabling freely programmable surfaces with various shapes. Besides the fundamental advantages of this technology, like comparatively low energy consumption, it is well known that these actuators can be used as sensors at the same time. The work we present in this paper is focused on the implementation of a DEA-based vibrotactile display into a mobile device. The display is used to present several operating conditions of a machine in form of haptic information to a human finger. As an example the design of music-player interface is introduced. Besides the concept of the user?s interaction with the interface we summarize challenging features like the high voltage generation, tactile stimuli encoding and especially the sensing capabilities. Using the actuators themselves for sensing offers a reliable possibility to detect user input. Other technologies, like resistive or additional capacitive layers are not needed and interconnections, feeding lines, electronic components, etc. can be economized. Energy efficient design and additional wireless communication emphasize the autonomous usability of the battery driven device. Finally, we present a characterization of the mobile device. We show results of user testing proving the intuitive handling with this kind of interface and high recognition values of different output signals.

All electromechanical transducers with a polymer dielectric as essential element have one basic principle in common: Electric charges that are fixed to the material itself permit the coupling of electrical and mechanical parameters and thus the transduction between the two domains in both directions. In dielectric elastomers, the charges are on the electrodes and the nonlinear movement is that of a soft capacitor. In space-charge electrets, charges of one polarity are embedded on or in the dielectric and move along with it. In the relatively novel piezoelectrets, charge layers of both polarities are trapped at internal surfaces and form macroscopic dipoles that are easily deformed by mechanical or electrical stresses. In piezoelectric polymers, the positive and negative charges are found in the form of relatively rigid molecular dipoles in the polymer chains. The density of those dipoles is changed by external mechanical and electrical stresses because of the elastic compliance of the amorphous matrix. These are the major mechanisms that can be easily compared. In this contribution, we will make an attempt to classify the various polymeric electromechanical transducer principles according to applications-relevant parameters such as frequency response, acoustic impedance, electrical and mechanical sensitivity, etc.

Electroactive polymers are a very attractive class of actuation materials with remarkable mechanical and electrical properties and with a great similarity to biological contractile tissues. Electroactive polymers (EAP) are lightweight, fracture-tolerant and are able to be manufactured in variable shapes. They can be classified in electronic and ionic electroactive polymers. In this work the active behavior of different ionic electroactive polymers - such as ionic polymer gels, ionomeric polymer-metal composites, and carbon nanotubes - is investigated. The modeling as well as the simulation of these materials is performed on different scales: If only the global behavior is of interest, a macroscopic theory can be used. By refining the scale, a coupled chemo-electro-mechanical formulation can be applied on the mesoscale in order to compute the concentrations, the electric potential and the mechanical displacement. By further refining the scale, the structure can be investigated on the microscale by the discrete element method. In this model, the material is represented by distributed particles comprising a certain amount of mass; the particles interact with each other mechanically by a truss or beam network of massless elements. In this work it is shown how the different models can be applied and which methods are predestined for describing the behavior of the various EAP materials.

Dielectric elastomer (DE) actuators are constructed from thin sheets of DE material sandwiched between compliant electrodes. The actuation principle of DE actuators is based on the electrostatic pressure being induced between oppositely charged electrodes which deforms the imcompressible DE material. This contribution reviews the dynamic characterization, modeling, and control of the PolyPower tubular DE actuator. First a schematic manufacturing process of the tubular DE actuator is presented. The dynamic characterization of the actuator is divided in; i) passive characterization where the mechanical characteristics of the actuator is examined, and ii) the dynamic electromechanical characteristics in a limited range of frequency. The dynamic modeling part is focused on developing a comprehensive and at the same time tractable dynamic electromechanical model for the tubular DE actuators undergoing relatively small deformations. The model is a combination of two sub-models describing the mechanical and electrical parts. These models are subsequently coupled via electrostatic forces by using the Maxwell equation. Dynamic control strategies of the DE actuators are developed for active vibration control and servo positioning purposes. The dynamic model of DE is used to improve the control performance and robustness. Two types of model-based control strategies are carried out; i) model-based adaptive feedfoward control, and ii) model-based internal model control.

It has recently been shown that anionic surfactants become incorporated into polypyrrole (PPy) structure during the chemical oxidative polymerization, while cationic and non-ionic surfactants affect the properties of PPy prepared in their presence only marginally. Still, it is essential to bring evidence for their existence at the outermost layers. In this work, XPS was used to track the surface chemical composition of surfactant-containing polypyrrole powders. Polypyrrole was synthesized by chemical oxidative polymerization of pyrrole in aqueous solution containing an oxidant, ferric chloride or ferric sulfate, and various anionic surfactants. PPy powders were characterized by elemental analysis, scanning electron microscopy, FTIR spectroscopy, XPS, conductivity measurements and inverse gas chromatography (IGC). The presence of anionic part of sodium bis(2-ethylhexyl) sulfosuccinate (AOT) was detected by both bulk and surface analytical techniques indicating that it was incorporated into the PPy structure. However, comparison of the bulk and surface compositions highlights a gradient concentration of AOT within the PPy structure. At low loading, AOT acts essentially as a co-dopant, whereas at high loading it co-dope PPy in the bulk of the particles and moreover acts as a surfactant. The addition of AOT during PPy preparation using FeCl3 as oxidant increases the conductivity by one order of magnitude compared to the pristine PPy-chloride.

Dielectric Electro-Active Polymers (DEAP?s) can achieve substantial deformation (>300% strain) while, compared to their ionic counterparts, sustaining large forces. This makes them attractive for various actuation and sensing applications such as light weight and energy efficient valve and pumping systems. Many applications operate DEAP actuators and sensors at higher frequencies where rate-dependent effects influence their performance. This motivates the need for dynamic characterization of these actuators beyond the quasi-static regime. This work provides a systematic experimental investigation of the quasi-static and dynamic electro-mechanical properties of DEAP actuators and sensors. The actuators used in this work consist of a biasing element (either a mass, linear spring, or a non-linear spring) coupled with an active out-of-plane DEAP element. The resistive and capacitive sensing capabilities of these out-of-plane DEAP elements are also investigated. The experiments are conducted with a particular focus on the hysteretic and rate-dependent material behavior. These experiments provide insight into the electrical dynamics and viscoelastic relaxation inherent in DEAP materials. This study is intended to provide useful information including high frequency performance analysis to anyone designing dynamic actuator and sensing systems using DEAP?s.

We present an array of 72 100 µm x 200 µm electroactive polymer actuators (EAP), which impose uni-axial strain when a voltage is applied. The devices are designed to stretch single cells adhered on each actuator to study their behavior when they are mechanically stimulated by a periodic strain. Our dielectric elastomer actuators consist of a 30 µm thick Polydimethylsiloxane (PDMS) membrane bonded to a Pyrex chip with 200 µm wide and 100 µm deep channels. Perpendicular to the channels, 100 µm wide compliant electrodes are patterned by low energy gold ion implantation into the PDMS on the bonded (lower) side of the membrane, and a blanket electrode is implanted on the top surface. Metal ion implantation of PDMS allows for highly compliant stretchable electrodes. Each actuator is thus at the intersection of the ion-implanted electrodes, where the electrostatic pressure locally compresses the soft elastomer out-of-plane, and the channels in the Pyrex, where the membrane is free to expand in-plane. To characterize the achievable strain respect to the applied voltage, an array of 4 µm diameter aluminum dots is deposited on the electrodes through a stencil mask. The position of the dots is detected by an automatic image-processing program before and after applying the voltage. From this, we derive the displacement profile of the membrane and differentiate it to calculate the strain. At the electric field of 88 V/µm, the device has achieved 2.45% strain.

Ionic polymer metal composite (IPMC) is a very attracting soft actuator having large strain under low application voltage. It consists of an ionic polymer membrane and thin electrodes formed on the both sides of the membrane. By applying voltage in water, it bends by movement of hydrated counter ions and accompanying electroosmotic water flow. We fabricated Flemion®-based IPMCs by incorporating ionic liquids (EMIBF4, BMIBF4, BMIPF6) exchanging counter ion, and also an IPMC with Li+ as counter ion. Various heights of step voltages (0.5 to 2.0V) were applied to the IPMCs in water, and responses of bending curvature and driving current were measured. Effects of the kind of the ionic liquid and the voltage height on the responses were evaluated. The responses of bending curvature 1/R and electric charge Q transferred by counter ion, which was obtained by integrating the driving current, were well corresponded, and seemed to consist of two stages; the first is accumulation process of counter ion to the electrical double layer between the electrode and the ionic polymer with response times less than 5s, and the second stage is slower process longer than 10min. 1/R]Q curves tended to saturate with increase in the charge Q in the IPMCs including the ionic liquids, though the IPMC with Li+ had no such tendency. This saturation is considered to arise from the water flow of the opposite direction to that of the movement of the counter ion due to pressure gradient in the IPMCs.

Dielectric Elastomers (DE) are thin films made of rubber material, which can be used as electrostatic generators converting ambient mechanical strain energy into electrical. The amount of energy gain depends on the mechanical setup of the device, the material parameters and the utilized energy harvesting cycle. While the device has to provide a sufficient contraction of the polymer, the material should be stiff and obtain a high dielectric constant, DBS and polymer resistivity. The energy harvesting cycle can either be realized with constant charges, voltage, or electric field during relaxation or with an energy-optimal cycle with different phases considering further limitations. All possible cycles have in common, that a specific amount of initial energy has to be charged to the DE generator at maximum stretch and a certain amount of energy has to be discharged at minimum stretch. Additionally, some cycles also provide energy during the relaxation phase. Depending on the utilization of the energy harvesting, different setups are required for the overall system, which has to be controlled by an energy management system. Beside the DE generator itself and a power electronics for the bidirectional energy flow, a battery with sufficient storage capacity is required for an isolated operation, while in case of energy harvesting into the public power supply, a bidirectional inverter connected to the power net with a supercap has to be considered.

This paper reports a polymer nano-composite with enhanced electro-mechanical performance by mixing TiO2 nano-particles into polydimethylsiloxane (PDMS) matrix. The nano-composites with TiO2 concentration up to 30 wt% were synthesized by in-situ polymerization. High energy ball milling and surfactant polyethylene glycol was used to reduce the agglomeration and ensure a stable dispersion. The properties of nano-composites, i.e. transmittance, elastic modulus, response time and dielectric constant, can be tuned by controlling the TiO2 concentration. The nano-composites were applied in tunable gratings and showed reduced driving voltage and response time, comparing with traditional electroactive polymers (EAPs).

This paper reports a polymer nano-composite with enhanced electro-mechanical performance by mixing TiO2 nano-particles into polydimethylsiloxane (PDMS) matrix. The nano-composites with TiO2 concentration up to 30 wt% were synthesized by in-situ polymerization. High energy ball milling and surfactant polyethylene glycol was used to reduce the agglomeration and ensure a stable dispersion. The properties of nano-composites, i.e. transmittance, elastic modulus, response time and dielectric constant, can be tuned by controlling the TiO2 concentration. The nano-composites were applied in tunable gratings and showed reduced driving voltage and response time, comparing with traditional electroactive polymers (EAPs).

In order to realize reliable dielectric elastomer stack actuators that are suitable for industrial applications a new design approach is developed and experimentally tested. Whereas for most stack actuators either carbon powder or conductive polymers have been used, in this work a stack actuator is built with rigid, perforated electrodes made of thin metal sheets. In this way the whole actuator contracts in only one direction whereas all other directions remain unde-formed, which leads to a number of practical advantages like reducing parasitic boundary effects. After analyzing the new design approach on a numerical level and optimizing the design pa-rameters accordingly different elastomer materials and electrode designs are examined and compared. With the knowledge gained in these pre-tests a multilayer stack actuator is manu-factured and tested in different application scenarios. Its performance as actuator and sensor element is tested under various load conditions and its suitability as an active component in a control loop for active vibration control is demonstrated. Furthermore the actuator is tested in a high-cycle test and its long-term performance is studied. The work shows the great potential for elastomer actuators with perforated, rigid electrodes for future applications especially in the field of active mounts. It also shows the high demands for a precise manufacturing technology in order to minimize functional failures.

Ionic polymer-metal composite (IPMC) is one of the most attractive soft actuators because it have several unique characteristics such as low driving voltage and large strain. Therefore, it allows the material to fulfill specific needs for medical device applications. IPMC consists of a polyelectrolyte membrane and thin noble metal electrodes formed on the both surfaces of the membrane. By fabricating IPMC with patterned electrodes, it will be capable of complex motions such as peristaltic movement. In spite of numerous challenges in order to utilize IPMC in medical devices, there are many technological subjects to fabricate it. Conventionally, the most reliable formation method is a chemical gold plating method. For this reason, we already developed a formation method of patterned electrode using photolithography techniques and the chemical plating method. However, in this method, the side wall of the IPMC was also plated when it was not covered by the photo resist, and the both electrodes are short-circuited. To solve this problem, we developed a new formation method of patterned electrode using SF6 plasma treatment. In this method, during the plating, the electrode cannot be formed on the SF6 plasma-irradiated areas of the membrane probably by decreasing of ion-exchange group due to fluorine termination process to the polymer chains. Therefore, the cutting process of the side wall does not need, and this method can be easily incorporated with micro machining technologies.

Low-voltage electroactive polymer (EAP) actuators have the large potential for a variety of practical applications, if they are operable in air quickly over a long period of time with a large movement under ambient conditions. In previous papers, [1-3] we have reported the dry actuator that can be fabricated simply by layer-by-layer casting, using ebucky gelf, a gelatinous room-temperature ionic liquid (IL) containing single-walled carbon nanotubes (SWCNTs). Our actuator@(the bucky-gel actuator) has a bimorph configuration with a polymer-supported internal ionic liquid electrolyte layer sandwiched by polymer-supported ebucky gelf layer@(bucky-gel electrode layer), which allow large and long-lived operation in air at low applied voltage. We also reported a second-generation SWNT actuator composed of polymer-free nanotube electrodes, which showed a much better performance than reported edryf EAP actuators including our first-generation design. [4] The actuator worked even at a much higher frequency such as 100 Hz without any notable deterioration in more than 10,000-times continuous operations in air. In this paper, some of the recent improvements of our bucky-gel actuators will be reported. [1] Fukushima et al., Angew. Chem. Int. Ed. 44 2410 – 2413(2005). [2] Mukaiet al.. Electrochim. Acta 53 5555 – 5562 (2008). [3] Takeuchi et al. Electrochim. Acta 54 1762 – 1768 (2009). [4] Mukai et al., Advanced Materials 21 1582-1585(2009).

The propagation of elastic and electric waves in soft dielectric elastomer plates is investigated. We consider incremental fields superimposed on a pre-loaded finitely stretched layer. Three different loading paths which result in the aforementioned deformation are accounted for. The dispersion relation between the waves speed of propagation and lengths is evaluated by satisfying the corresponding coupled equations of incremental electroelastodynamics along with the pertained boundary conditions. Subsequently, numerical examples for the fundamental branches are evaluated, demonstrating the dependency of the propagation velocity on the bias fields. The foregoing results reveal a stabilizing effect of the pre-stretch, in agreement with experimental data. Our findings hints at the possibility of a method for controlling the propagation velocity, as well as filtering particular frequencies by a suitable choice of the electrostatic bias field. Keywords: electroactive polymers; dielectric elastomers; wave propagation; finite deformations; soft actuators; non-linear electroelasticity;

EAPs undergo large deformations in response to electrostatic excitation, a property which makes them attractive. However, these dielectrics materials require high excitation voltage to generate a meaningful deformation. To overcome this difficulty, the mechanical response of electroactive elastomer composite to an electrostatic excitation is examined. Recent experimental works on soft elastomers incorporating randomly distributed high dielectric fillers demonstrated an enhancement of the mechanical response to applied voltage. Corresponding studies based on analyses of idealized microstructure at small strains predict that the use of multiphase soft dielectric system will significantly improve the electromechanical coupling. Motivated by these findings, we seek for feasible heterogeneous microstructures that will allow to reduce the needed voltage. To this end we consider a periodic cell with appropriate periodic boundary conditions on both the electrostatic and the displacement fields. The electromechanical coupling is introduced into the model in terms of the so called Maxwell electrostatic stress. The analysis is performed by application of the commercial finite element code COMSOL MULTIPHYSIC. We demonstrate that an order of magnitude improvement of the electromechanical coupling can be achieved with the right choice of morphology and analyze the physical mechanism by which the enhancement is achieved.

DEA promise to revolutionize user interfaces by enabling surface actuators that can change surface shape. They can give tactile feedback as output and act as sensors for user input at the same time. In order to bring actual application demonstrators closer to real product applications it is getting important to take care of an appropriate fabrication process. Several structures have been introduced in the past combining ease of fabrication and maximum actuator deformation. One of the most effective setups is the ?thickness-mode? actuator configuration, introduced by Prahlad, et al. in 2005. As a further simplification of this setup we build such actuators using only one passive thickness enhancement layer leading to an asymmetric setup. The resulting deformation of these actuators is quite surprising: the typical bulging at the electrode-boundary interface is not measurable. Instead we observed the whole electrode area moving as a whole flat surface in the direction away from the passive layer, even against gravity. Due to the absence of any further bending effects we call this type of movement ?duck mode?. We will present different measurement results showing the observed behavior. Different layer ratios will be compared as well as different shapes and sizes of electrodes. Based on an active dielectric film with a thickness of less than 100 ?m and a passive enhancement layer of about 500 ?m we can realize actuators with a deflection of more than 300 ?m.

The main problem in the field of DEs is today represented by the high driving electric fields (orders of 10-100 V/?m) necessary for their activation. Although several attempts have been made in order to increase strains enhancing the dielectric constant (?) of such matrices and keeping low elastic moduli (Y) to control the ?/Y ratio, currently several challenges have still to be faced. In this work, a new approach is presented to enhance the electromechanical performance of DEs. Soft elastomeric polyurethane matrices with foam structure were prepared to be electrically charged and poled via Corona process. Such matrices, after the treatment, showed electret-like properties and enhanced electromechanical strains possibly due to the presence of macrodipoles induced both at the matrix/pore surfaces and inside the bulk. Morphological (SEM, Bet), dielectric, dynamical-mechanical (DMA) and electromechanical tests have been performed in order to characterize the material. Results show that corona charging may represent a new promising route for obtaining dielectric elastomers with improved transduction performance to be used as actuators.

Dielectric elastomers are an important class of materials currently employed in the design and realization of electrically-driven, highly-deformable actuators and devices which find application in aerospace, biomedical and mechanical engineering. Composite materials can improve their performance, specially when a stiff and a high-permittivity phase is included in a soft elastomeric matrix --inducing a considerable increase of the overall dielectric constant of the material--, thus enhancing the coupling between electrical input and mechanical response. In the talk, the behaviour of laminated soft-dielectric composites under plane-strain deformation is highlighted with particular reference to the instability of a prestretched layer (a configuration useful for the design of buckling-like actuators), where the effectiveness of the composite layout is shown. Results are shown for an extended hyperelastic model where also electrostrictive effects can be taken into account.

We present the design, fabrication process and evaluation of a gas valve using dielectric elastomer stack actuators. The elastomer actuators are integrated into a micro system consisting of the valve seat and spring structure to produce the closing force for the valve. Based on the application as gas valve for a micro burner the required flow rate and the allowed pressure drop are derived. For this application it is important to control several small valve elements independently. With the used fabrication technology multiple valves can be realized within a single device. One valve in such an array has the size of 15 x 15 mm2. The actuator thickness and the shape of its active region are determined to achieve a deflection of up to 50 µm by the use of a finite element simulation. To generate the closing force a spring structure made of nickel with intrinsic layer stresses is fabricated using an electroplating process. The fabricated valves are characterized with respect to the deflection of the actuator and the flow characteristic of the valve. The measurement shows that the required deflection of 50 µm is achieved. The flow rate can be adjusted between 20 ml/min and 120 ml/min at a gas pressure of 50 mbar.

Dielectric elastomers are capable of large deformations induced by applied electric field. This electromechanical coupling can be utilized in manufacturing of promising soft actuators. In this work, large-scale instabilities that may develop in these materials are investigated. Basing on a finite deformation theory of dielectrics, a general criterion for the instability onset is introduced. The criterion is implemented to a class of anisotropic materials. To this end an exact analytical solution for layered soft dielectrics is derived. By implementation of the general instability criterion together with the exact analytical solution, the stability of the heterogeneous system is analyzed. It is demonstrated that the microstructures significantly impact the stability of the anisotropic materials.

Bucky gel actuators are promising because they can operate at low voltage in air with good frequency and strain perfromance. The existing technology for bucky gel artificial muscles is based on bimorph configuration thus producing a bending motion. We have designed an actuator capable of both linear and bending motion by using a three electrode configuration in which two electrodes are active and the third one is a passive counter plate. Results for actuators prepared using two different kinds of passive metal counter electrodes will be reported and discussed. We have also successfully cross-linked Super-Growth single walled carbon nanotubes (SG-CNTs) and used the resulting nanocarbon in bucky gel actuators. The cross-linking probably prevents sliding between tubes and gives rise to an increase in the specific capacitance of the composite material that, when used in bucky gel actuators, results in a dramatic improvement of the performance in terms of strain and efficiency. Strain for modified SG-CNTs is higher at every tested frequency even if the amount of SG-CNTs in the composite is less than an half with respect to pristine material. Efficiency of the actuation is also increased: at the same charge level modified nanotubes based actuators have a strain that is approximately double than for the pristine SG-CNTs one. The effect of the cross linked SG-CNTs on the blocking force is to significantly shorten response time with respect to devices based on pristine nanotubes.

Three properties of the elastic medium in a dielectric elastomer actuator affect the actuation properties directly: dielectric constant, electric breakdown strength, and mechanical stiffness. The dielectric constant of a given elastomer can be improved by mixing it with other components. Insulating particles are commonly metaloxides, we present our results on nanoparticulate TiO2 and BaTiO3. We demonstrate how the permittivity may increase faster than expected due to the high surface of the nanoparticles, but with drastic effect on electrical loss. A chemical coating is shown to lead to strong improvements. Also, we show studies on conducting nanoparticles. Especially, we demonstrate how ?simple? percolation causes detrimental side effects, leading to overall reduction in actuation. Careful distribution of nanoparticulate metal in mesoporous silica-spheres leads to useful increases in permittivity, but the mechanical properties are not technologically useful. A ?molecular composite? approach, in which the conducting nanoparticles are docked chemically to the backbone appears valuable. The achieved improvements seem to be all connected to avoiding a random distribution of the conducting entity, and instead achieving a constant nearest neighbour separation. Finally, grafting of molecular dipoles to the elastomer backbone with simultaneous variation in crosslinking statistic strongly enhances electromechanical response.

The contribution describes a new kind of structures with a variable stiffness based on electroactive polymers (EAP). These structures are supposed to be components of new smart, self-sensing and -controlling composite materials. Dielectric Elastomers from Danfoss Polypower are used to drive the actuators because of their commercial availability. The basic idea is to change the area moment of inertia of bending beams. These beams are built up as multi-layer stacks of thin metal plates. Its internal structure can be changed by electroactive-polymer-driven actuators controlling the area moment of inertia. So it is possible to strongly change the stiffness of bending beams up to two orders of magnitude. Thereby, the magnitude of varying the stiffness can be scaled by the number of layers used in the bending beam. The control mechanism is based on form closure between the actuator and the metal multi-layer. By using flexural hinges it is possible to pre-strain the electroactive polymer. The pre-straining force can be adjusted by flexural hinge parameters. Modeling of the mechanical structure including the EAPs uses a pseudo rigid-body model, a strain energy model as well as a finite element analysis. First results show the feasibility of the proposed structures with stiffness control.

Subject to a voltage, a dielectric elastomer deforms. Voltage-induced strains of above 100% have been observed when dielectric elastomers are pre-stretched, and for dielectric elastomers of certain network structures. Understanding mechanisms of large actuation strains is an active area of research. We propose that the voltage-stretch response of dielectric elastomers may be modified by pre-stretch, or by using polymers with ?short? chains. This modification results in suppression or elimination of electromechanical instability, leading to large actuation strains. Our theory also provides a qualitative explanation on the experimental observation that ?the dielectric strength appears to be enhanced by stretch?. We further propose a method to select and design a dielectric elastomer, such that the actuation strain is maximized. The theory may contribute to the development of dielectric elastomers with exceptional performance.

The effect of mechanical forces on cells is a relatively unexplored area of cell biology. However, mechanical forces play an important role in cell proliferation, function, and stem cell differentiation. For instance in muscle contraction, bone growth, and morphogenesis. There is only a limited selection of tools to study this on a single cell level and/or follow the events in real time. Here, we present novel tools in order to mechanically stimulate (stem) cells both on a single cell level as well as parts of functional monolayers. The devices are designed in order to function with different imaging techniques commonly used in cell biology. The mechanical stimulus is provided by polypyrrole microactuators. These actuators can be operated in salt solutions including cell culture media, making them well suited for cell biology applications. In addition, polypyrrole is known to be biocompatible. We will present devices with which we can stretch cells and show the cellular response to this mechanical stimulation. Since the dawn of eukaryotic cells many parallel molecular mechanisms that respond to mechanical stimuli have evolved. This technology allows us to begin the investigation of these mechanisms on a single cell level.

CPC (carbon-polymer composite) is a type of low voltage electromechanically active material, which is often built using two layers of electrodes containing nanoporous carbon separated by a thin ion-permeable polymer film; ionic liquid is used as electrolyte. An artificial muscle composite material consisting of Carbide Derived Carbon (CDC) and 1-ethyl-3-methylimidazolium tetrafluoroborate (EMI-BF4) ionic liquid was modeled using Molecular Dynamics (MD) simulations, in order to determine the molecular structural rearrangements causing actuation. CDC was represented as separate curved graphene-like flakes. The charge distribution in the flakes was determined by PM6 semi-empirical optimization. The pore size distribution of CDC and the density of the material were comparable to experimental data. The molecular structure analysis revealed a preferential parallel orientation for the cations over the negatively charged CDC surfaces, while cationic rotations and reorientations could be observed for positively charged CDC. Changes in the pore occupancy for each ionic type were observed for pore sizes between 4 and 7 Å, which together with the replacement of large cations with smaller anions could explain the volume decrease in the anodes (and vice versa the volume increase in the cathodes) in this type of actuator.

Soft actuators based on conducting polymers are new high-performance materials that are not only compact and lightweight, but also flexibility deform and require only a low driving voltage. Therefore, conducting polymer soft actuators are attracting attention as future power supplies for various devices. The mechanism of electrically conducting polymer soft actuators involves electrochemomechanical deformation by doping-dedoping of ions. The electrochemomechanical deformation properties of polyaniline (PAn), poly(o-methoxyaniline) (PmAn), poly(3-alkylthiophene) (PAT) and polypyrrole (PPy) have been clarified. Recently, soft actuators with multilayered structures have been actively studied. We have developed a bimorph conducting polymer actuator based on polypyrrole. Furthermore, micropumps that use conducting polymers soft actuators as their driving sources have been constructed and developed for practical applications. The purpose of the present study is to clarify the basic characteristic of the bending actuation of the bimorph conducting polymer actuator based on polypyrrole. The bimorph conducting polymer actuator consisted of an anion-driven layer actuator, PPy.DBS, and a cation-driven layer actuator, PPy.DBS. A bending actuation of the bimorph conducting polymer actuator depended on the ion volume per charge strongly. If the ion volume of anion differed from that of cation, the bending actuation of the bimorph conducting polymer actuator became irreversible.

Soft dielectric EAPs have attracted much interest in recent years due to their outstanding active deformation potential. Nevertheless, their drawback is the huge voltages required to stimulate the mechanical actuation. One strategy to reduce the driving voltage is by increasing the dielectric constant of the polymer. The unique mechanical and electrical properties of carbon nanotubes (CNTs) and functionalized graphene sheets (FGS) make them the ideal candidates to increase the dielectric constant of the material at extremely low loading fractions while retaining the intrinsic elastomeric nature of the matrix following a subpercolation approach. In the current work, the potential of both CNTs and FGS as fillers was studied towards the development of improved DEAs. Three loading fractions, 0.5, 1 and 2 wt.-% of CNTs and FGS were homogeneously dispersed in a PDMS matrix and were subsequently vulcanized at 170 C for 5 min. The inclusion of small quantities of CNTs and FGS in the silicone matrix enabled an increase of the relative permittivity as a function of the filler content, while the elastic modulus increased with a much lower rate than that of the dielectric constant. The 1 wt.-% CNT filled films show a two fold increase in the dielectric permittivity, while there was a ten-fold increase for 2 wt.-% FGS/PDMS films at 10 Hz. The addition of the fillers resulted in a slight decrease of the elongation at break values although a good stretchability was still retained.

Dielectric elastomer actuators (DEA´s) enable a wide range of interesting applications since they are soft, lightweight and have direct voltage control. Demonstrators already exist for an arm wrestling robot, miniaturized pumps, optical adjustment actuators, an electro-mechanical logic gate for distributed multielement smart systems, etc.. However, one of the main obstacles to their wide-spread implementation is their high operating voltage, which tends to be several thousand volts. In principle, the operating voltage can be lowered by reducing the thickness of the elastomer film, increasing the permittivity or lowering the mechanical stiffness. Therefore a novel chemical method is established to enhance the permittivity of a silicone matrix, which prevents agglomeration and give elastomer films that are homogeneous even at molecular level. A push-pull dipole is synthesized to be compatible with the silicone crosslinking chemistry, allowing direct grafting to the crosslinker molecules in a one-step film formation process. The chemical, thermal, mechanical and electrical properties of films with dipole containing a range between 0 wt% to 13.4 wt% were thoroughly characterized. The grafting of dipoles increases the relative permittivity and simultaneously decreases the stiffness, resulting in the actuation performance being improved by a factor of six compared to the non-modified silicone.

Skin is a natural paradigm for biomimetic soft active materials. Here, we introduce a new multifunctional microvascular polymer composite capable of undergoing large stiffness changes. The material is based on the biological concepts of thermoregulation and muscle activation. The composite is an actively heated and cooled shape memory polymer with embedded microchannels for fluid flow. The active heating/cooling by this local mechanism significantly increases the response time of the material, which to date has been a major drawback. The change in stiffness is due to the shape memory effect. Changing the temperature of the solid above and below its transition temperature, transforms the solid from a glassy phase to a rubbery phase. If the polymer is coated with compliant electrodes, then the electrostatic effect or Maxwell stress effect can be used to deform the soft rubbery SMP to different stable deformation states that can be maintained after the removal of the electric field. We have successfully fabricated multifunctional microvascular polymer composites with stable hollow channels (100 ?m in diameter). Thermomechanical characteristics and electro-thermo-mechanical characteristics of the microvascular composite with different fiber architectures will be presented.

To realize compliant electrodes with good electrical conductivity that can undergo large strains without adding too much stiffness is one of the main technical challenges for dielectric elastomer actuators. Metal electrodes are normally not feasible due to their high stiffness, though their electrical properties are excellent. For stack actuators often carbon powder electrodes have been realized. Regarding mechanical connections one of the main disadvantages of polymer stack actuators is the inhomogeneous strain distribution along its length. In order to avoid this effect a new stack actuator with rigid, perforated electrodes is considered. Here the whole actuator only contracts in one direction whereas all other directions remain undeformed. In this way it is possible to build actuators with only a few layers without losing performance by boundary effects. To find an optimal design a numerical model for actuators is developed. At first a mechanical 2D finite element model is considered to analyze the deformation behaviour of an elastomer between perforated metal sheets. To investigate the distribution of the electrical field between the electrodes and the resulting electromechanical interactions the model is enhanced. In the last step additionally the nonlinear contact behaviour between electrode and elastomer is considered. The studies show the potential of the proposed approach and also demonstrate the need for a careful design and the advantage of numerical optimization.

Legged robots are using hydraulic or electric actuation. However, the former require bulky power supplies, while the latter require heavy batteries and transmissions that increase the overall weight. The possibility of using EAP actuators as artificial leg muscles is therefore a very interesting option. In this presentation, we will describe the actuation problem for legged robots and present experiments, results from employing EAP actuators in a legged robot, as well as pertinent guidelines.

Poly-L-lactic acid (PLLA) which exhibits shear piezoelectricity, is a typical example of chiral polymer used as an industrial raw material. To fabricate a workpiece with a complicated shape and a small area, it is easier to use PLLA than to use lead zirconate titanate ceramics. To realize a PLLA actuator, we considered a simple device consisting of a hemispherical container that can rotate on the top end face of a PLLA film roll under the application of a voltage. Actually, we placed the PLLA film roll transducer vertically on a fixed stand. A plastic hemispherical container with a thin wall, a diameter of 3 cm and a weight of 4.2 g was placed on the upper end face of the PLLA film roll transducer so that the center axis of the PLLA film roll and that of the hemispherical container coincided with the upper end face of the PLLA film roll in contact with the plastic hemispherical container. Then, to induce the rotation of the plastic hemispherical container, an ac voltage with an amplitude of 350 V. The plastic hemispherical container rotated smoothly in the counterclockwise direction when an ac voltage with a frequency of 5.25 kHz was applied. In this case, the plastic hemispherical container rotated counterclockwise at a speed of 150 rpm. Here, we emphasize that there are no special complex mechanical parts in the proposed device. The experimental result indicates the strong possibility of realizing a soft actuator using chiral polymers such as PLLA.

Polypyrrole/DBS films and bilayer muscles were characterized under flow of constant currents by changing different working variables: electrolyte concentrations, temperature, weight of objects attached to the bottom of the muscle, or current flowing through the device will be presented. The bending movement of the bilayer muscles was characterized through a constant angle described by the free bending end of the device. The device is a faradic machine working under control of the charge consumed per weight unit of reduced polymer. So, the angular rate is a linear function of the charge consumed per unit of time (current) and per unit of reduced polymer weight and the described angle is a linear function of the charge. The electrochemical redox reactions in a film of any conducting polymer are influenced by ambient conditions: electrolyte concentration, temperature, mechanical conditions. Driven by constant current decreasing electrical energies will be consumed at increasing values of the variables improving the reaction rate. Both, the potential evolution and the consumed electrical energy are sensors of the ambient variable during the reaction. Acknowledgements: Ministerio de Ciencia e Innovación (MICCIN) (MAT 2008-067021 MAT), Fundación Séneca (CO8684/PI/08).

Ionic polymer-metal composites (IPMCs), one of the electroactive polymers, have attracted great attentions [1]. Nafion® membranes have been used for the manufacturing an IPMCs due to their excellent ionic conductivity and mechanical strength but they have high cost and limited thickness options. Radiation grafted membranes are one of the promising alternatives mostly used in fuel cells [2]. Radiation grafting is a well-known method for introduction of functional groups into a base polymer for design of the polymer architecture [2]. In this study, novel IPMC actuators employing radiation-grafted fluoropolymers as the ionomeric matrix have been developed. The process involves pre-irradiation of poly(ethylene-alt-tetrafluoroethylene) or ETFE polymer, grafting of irradiated ETFE with styrene to form a graft copolymer, subsequent sulfonation of the graft to introduce proton exchange sites and finally deposition of platinum (Pt) on both sides of membranes. A series of ETFE based radiation grafted membranes with varying graft levels (GL) and thickness were prepared. Ionic conductivity, water uptake and the displacement of the resultant IPMCs as a function of GL and film thickness and were determined. It was found that IPMC actuators based on radiation grafted membranes exhibited larger displacements for all thickness compared to Nafion®. 1. M. Shahinpoor, Electrochim. Acta 2003, 48(14-16), 2343. 2. L. Gubler, S. A Gürsel, G. G. Scherer, Fuel Cells 2005, 5, 317.

The state-of-the-art technology to drive refreshable cells for Braille displays is represented by piezoceramic bimorph cantilever actuators. The cantilever-like structure that is necessary to amplify the small stroke of piezoceramics makes the actuators highly bulky, so that displays based on those cells can not be made with more than two rows. This makes the realization of full-page refreshable Braille displays impossible. Full-page displays are meant as the Braille-coded tactile analogs for the blind people of displays commonly used by sighted people to visualize text and images. To develop such kinds of systems, we are currently designing, manufacturing and testing refreshabe Braille cells based on ?hydrostatically coupled? dielectric elastomer actuators (HC-DEAs). Each Braille dot consists of a bubble-like HC-DEA having a diameter of about 1.5 mm. It includes an electromechanically active membrane (made of a DE film coated with compliant electrodes), a passive membrane in contact with the finger, and an incompressible fluid confined between them. The bottom active membrane buckles outwards as a voltage difference is applied between its electrodes, while the passive membrane passively follows inwards, according to the fluid-enabled transmission. Therefore, the cell dot is lowered or raised as a voltage is applied or removed, respectively. This presentation shows opportunities of this configuration and challenges for implementations with effective materials.

We present the experimental validation of an analytical model for the response time of fluidically coupled ion-implanted DEAP actuators. Niklaus et al. have demonstrated the feasibility of tunable lenses with these actuators [1]. The actuators are 15 to 30 um thick PDMS membranes on which electrodes are deposited by gold ion implantation, with a very low impact on the Young?s modulus [2]. The device is a PDMS fluidic body that encloses a buried channel with, at both ends, 3mm diameter cylindrical openings reaching the surface. We seal them with two membranes: one is the actuator and the other the tunable lens. We pattern the outer electrode of the actuator by ion implantation, and the inner electrode is the liquid. The out-of-plane deflection of lens and actuator are measured as a function of time in response to voltage steps up to 1500V. The dynamic response of the system can be modeled by a 2nd order hydraulic impedance circuit with electrical circuit analogy. The parameters are the fluidic resistance, inertia and compliance. We extract the resistance and the inertia from the geometry and the liquid properties. The compliance is derived from the membrane behavior. We report on response times tr for different channel dimensions, membrane parameters, and initial pressure. Typical tr values are below one second, in reasonable agreement with the simple analytical model. [1] Niklaus M. et al., Proc. of SPIE, Vol. 7642, 2010 [2] Rosset S. et al., JMEMS, vol.18 no. 6, 2009

To ensure the autonomy of various sensors, a promising alternative to batteries is to scavenge mechanical ambient energy. In many applications, such as e-textiles, boat sails, shock absorbers or door hinges, the transducers must be deformable, adaptable and modular. Dielectric polymers can well answer these three constraints. In addition, these polymers are economic, light, flexible and resistant. They have a fast response time, are efficient and deform significantly. Nevertheless, they are passive materials requiring the installation of an external high-voltage (HV) source to polarize them and create energetic cycles. Thus, the improvement of dielectric generator will require the development of performing power management as well as the improvement of the dielectric polymers. Here, we present a new design of scavenger using electrets for poling the dielectric polymer which is a first step toward a fully autonomous system. Our scavenger is composed of commercial dielectric polymer (3M VHB 4910) with patterned Teflon electrets developing a potential of -300V, and patterned grease electrodes. This solution is analytically modelled and simulated. The performances are compared with those obtained with a constant charge cycle. The power management of all these structures are explained and compared in term of efficiency and useful output energy. The manufacture of these new scavengers is under development.

The dielectric elastomers (DE) are part of the electronic electroactive polymers (EAPs) and present a good combination of electromechanical properties such as high achievable strains and stresses, fast response speeds, long lifetime, high reliability and high efficiency. A polymer network is a three-dimensional entity formed by the interconnection of polymer chains and is sometimes referred to as an elastomer. In the present paper elastomeric bimodal networks are synthesized using two different molecular weight vinyl-terminated polydimethyl siloxanes (short PDMS chains and long PDMS chains), a 4-functional crosslinker and a platinum-catalyst. The bimodal networks are prepared using a ?two-step four-pot? mixing procedure. The pre-premixes A contain PDMS and crosslinker, while the pre-premixes B contain PDMS and catalyst. Films with a thickness of 100 µm are prepared using an in-house constructed coating device. The viscoelastic behaviour as function of the applied frequency (LVE diagram) is shown for different systems with varying stoichiometric values and the short chain:long chain mass ratio. The macromolecular structure of the new silicone networks is a controlled alternance between strength and flexibility/elasticity. The final networks are characterized by a low viscous dissipation and a low elastic modulus. The systems have promising properties for DEAP purposes as they are highly extendible, with a fast response, and have great stability and hence postpone the rupture.

Materials consisting in polymeric matrix with incorporated metallic compounds are of high interest for micro-electro-mechanical systems. Such materials combine the properties induced by the presence of the metal with those specific for polymers, among those being the easy processability. As is known, silicones exhibit an interesting combination of properties and are considered as proper polymeric matrixes for the incorporation of various inorganic powders. Here we present the preparation of polymeric composites based on polysiloxanes reinforced with fumed silica. Different amounts of metal oxides were physically incorporated in these matrices. The resulted composite samples were processed as thick films and crosslinked by radical mechanism. Their responses as a result of applying an electric field were registered using an AGILENT 5529A system, which is able to measure the linear micro and nanodisplacement with high resolution interferometer. Acknowledgments: This work is part of COST Action grant MP1003 and was financially supported by Project PN II-PC 12-128/2008 (ELOTRANSP).

Polydimethylsiloxanes (PDMS) are materials of high interest in micro-electro-mechanical systems applications due to their properties such as mechanical robustness, high chemical inertness, unique surface properties, good thermal/electrical insulation, stability against oxidation, high elongation ratio, low Young`s modulus, easy processing, and affordable costs. PDMS were recently used as dielectric elastomers for electromechanical actuators. When soft enough, they can change their shape when an electric field is applied. However, due to their low dielectric constant, large electric fields are required to induce a change. Several approaches were used to increase the dielectric constant of polymers which include blending with conductive fillers or ceramic particles. Our approach is to chemically modify the silicone backbone with cyanide or other polar groups. Several cyano-containing PDMS were prepared and their mechanic, dielectric, and electromechanic properties were investigated. Acknowledgments: This work is part of COST Action MP1003 and was financially supported by Project PN II-PC 12-128/2008 (ELOTRANSP).

Silicone rubber is one of the most common elastomer materials used for dielectric elastomer actuators (DEA). However, the main drawback of silicone rubber is its relatively low permittivity. Therefore, the objective of this work is the development of improved silicone materials with enhanced permittivity, but without balancing this improvement by a deterioration of other properties. Different approaches to enhance the permittivity without increasing the Young?s modulus correspondingly were evaluated. Electric and dielectric properties like permittivity, specific conductivity and electric breakdown strength, mechanical properties like Young?s modulus and viscoelastic shear modulus as well as actuation strain of single film actuators in the electric field were determined. The first approach was an inorganic modification of silicone rubber with highly dielectric barium titanate particles. With a concentration of 20 vol.% barium titanate particles, the permittivity of the silicone rubber has been increased by about 140 %. Simultaneously, the Young?s modulus of the silicone rubber was kept nearly constant at about 100 kPa. The strain of the modified material was approximately doubled with respect to the pure silicone rubber. In the second approach, an organic modification of the silicone rubber with fluorinated propyl groups was conducted. With this material an increase of the permittivity by about 70 % and a significant rise of the actuation strain were achieved as well.

A mechanism for the macroscopic charge balance during the transport of anions and cations across polypyrrole based composite membranes is proposed. For the mechanism to be studied, anions and cations were monitored simultaneously across PPy based composite membranes, which are known to have cation exchange (PPy(PSS)), anion exchange (PPy(ClO4)) and mixed ion exchange properties (PPy(pTS)). Even though none of the membranes were found to be completely permselective, the flux of cations was higher than that of anions across the PPy(PSS) composite membrane, while the flux of anions was higher than that of cations across the PPy(ClO4) composite membrane. A clear trend in the change in pH of the receiving solution was observed; decrease in pH (acidic) when using anion exchange membrane and increase in pH when using cation exchange membrane. In the case, when an equal flux of anions and cations was observed, the pH of the receiving solution was ca 6-8. There was only a negligible flux of Ca2+ across PPy(PSS) membrane in the transport experiments carried out with the source solution consisting of either Ca(NO3)2 or an equimolar mixture of KNO3 and Ca(NO3)2. The PPy(PSS) composite membrane was impermeable towards NO3- ions when the source solution was Ca(NO3)2 but permeability towards NO3- was observed when the source solution was either KNO3 or an equimolar mixture of KNO3 and Ca(NO3)2. Thus, the movement of anions is accompanied by cations across PPy(PSS) composite membranes.

Dielectric elastomer actuators require reliable and highly compliant electrodes. We have evaluated the electrical and mechanical resistance of thin gold films on silicone based dielectric elastomers to extended cyclic uni-axial loading, and found that 50nm thick gold films on 1mm thick silicone substrate remain electrically conducting over 100,000 cycles to 20% tensile strain. The film morphology evolves from a random micron size crack pattern into a square-like crack pattern. We discuss potential application of stretchable metal electrodes for their use in dielectric elastomer actuators.

Smart materials change their properties with external energy supply. Besides the known ferro-fluids and Magneto Rheological Fluid (MRF) also the Electro Active Polymer (EAP) and Magneto Rheological Elastomer (MRE) belong to these intelligent materials. The latest generation of magnetic elastomers represents a new class of composite materials. This consists of small magnetized particles which are sized in the micron or even nanometer range that in turn is bounded in a highly elastic rubber matrix. These materials are very often called MRE. Only recently, it has managed to develop these materials even further, so that very soft composite materials with a young?s modulus up to 10 kPa are possible. These soft polymers could be named magneto-active polymers. The combination of polymers with magnetic materials show novel and often enhanced properties. A precisely controllable young?s modulus and hardness, giant and non-homogeneous deformation behavior and rapid response to the magnetic field opens up new possibilities for various applications. Since MAP represent a very new technology, the behavior of these materials as a function of their composition and external conditions so far are not yet sufficiently understood. Therefore, some fundamental studies are necessary. In this paper, the mechanical surface properties are studied using a micro hardness meter. This work shows the possibility to control mechanical properties at the surface of MAP with new developed magnetic systems.

Polypyrrole is electromechanically active and actuates due to ion and solvent movements during redox switching, causing both reversible and irreversible swelling. The swelling of polymers is known to be highly dependent on the degree of cross-linking. Despite this, little research has been undertaken to date on the affect that cross-linking has on the actuation of conjugated polymers. It is likely that there exists a level of cross-linking, that results in optimum actuation performance. An understanding of this relationship, would allow actuators to be designed that are capable of greater movement, operating speeds and force generation. Here we present novel synthetic strategies aimed at altering the cross-linking density of electrosynthesised polypyrrole. The actuating performance of these materials has been assessed using new apparatus capable of making non-contact dynamic measurements. Our synthetic strategies, measurement setup and results will be presented.

Movement of artificial muscles based on conducting polymers is driven by electrochemical reactions. The polymer chains are oxidized or reduced when anodic or cathodic currents are applied promoting volume variations by interchange of anions and solvent, resulting in macroscopic movements. Artificial muscles use to work under flow of constant currents. Under electrochemical considerations, the evolution of the muscle potential with time (t) during current flow is: E=E0+{RT/(1-á)nF} {ln(it/FV)?a ln[A-]?b ln[Pol*]?ln ka0} (2) Where E is the muscle potential; R is the universal gas constant; T is the working temperature; á is the charge transfer coefficient; F is the Faraday constant; i is the applied current; V is the volume of polymer; a and b are the reaction orders related to the concentration of anions ([A-]) or the concentration of active centers ([Pol*]), respectively; and ka0 is the rate constant or rate coefficient of the reaction. This is a sensing equation: the evolution of the muscle potential is a function of working temperatures, concentration of anions in the electrolyte, or of the applied current. The same two connecting wires include driving current (actuating) and potential response (sensing) signals. Good agreements were attained between experimental results and simulated responses from Eq. 2 for different experimental conditions. Acknowledgements: Spanish Government (MICINN) Projects MAT2008-06702, Seneca Foundation Project 08684/PI/08.

Patients who are affected by motor disorders of the hand and have residual voluntary movements of fingers can benefit of self-rehabilitation programs to be performed by means of so-called dynamic hand splints. These systems consist of orthoses equipped with elastic bands or springs which exert a passive resistance to voluntary elongations of one or more fingers. So, such systems allow for rehabilitation of fingers that still can voluntarily be moved against the recovery force of the counteracting elastic component. Although attractively simple, this approach is limited by the impossibility of modulating the counteracting action in real time. This does not allow for customized training and real-time control of the rehabilitation exercise, which might desirable to improve the rehabilitation efficacy. To solve this problem, electromechanically active versions of dynamic hand splints are needed. To address this issue with a solution relying on compact and light-weight devices, we are currently studying possible benefits of using dielectric elastomer (DE) transducers as variable-stiffness devices. The transducer is connected to a tendon wire, to be pulled and released by the user, and to a load cell. A processing unit controls the stiffness, so as to train the patient according to desired rehabilitation plans. This presentation shows the current stage of implementation of this concept using a multilayer transducer made of the PolyPower DE film.

Dielectric elastomer material systems are becoming attractive systems as possible key components in sensors, actuators, and energy generators due to their high stress and strain, fast response time, small electrical and mechanical losses and low production cost. These systems consist of an incompressible dielectric elastic material sheet (thickness: 50-200 µm) with compliant electrodes (thickness: 50-250 nm) on the two opposing sides. When a voltage is applied the two electrodes attract each other thereby squeezing the material. In this work we consider folded dielectric elastomer actuator. While this approach has been investigated previously a detailed model has so far been missing. The modelling of folded dielectric elastomer actuators is challenging as the problem is both multiscale and multiphysics in nature. In this work a macroscopic modelling approach is presented, which includes the electromechanical coupling in the constitutive equations, similar to what is currently done for piezoelectric systems. By using this approach the detailed microscopic structure of the actuators need not be taken into account. This is a huge simplification of the problem thus enabling solutions to be found using numerical schemes like the finite element method as the mesh size needs no longer be on the scale of micrometers.