This PDF file contains the front matter associated with SPIE Proceedings Volume 7976, including the Title Page, Copyright information, Table of Contents, Introduction, and the Conference Committee listing.

Developing bionic ankles poses great challenges due to the large moment, power, and energy that are required at the ankle. Researchers have added springs in series with a motor to reduce the peak power and energy requirements of a robotic ankle. We developed a "robotic tendon" that reduces the peak power by altering the required motor speed. By changing the required speed, the spring acts as a "load variable transmission." If a simple motor/gearbox solution is used, one walking step would require 38.8J and a peak motor power of 257 W. Using an optimized robotic tendon, the energy required is 21.2 J and the peak motor power is reduced to 96.6 W. We show that adding a passive spring in parallel with the robotic tendon reduces peak loads but the power and energy increase. Adding a passive spring in series with the robotic tendon reduces the energy requirements. We have built a prosthetic ankle SPARKy, Spring Ankle with Regenerative Kinetics, that allows a user to walk forwards, backwards, ascend and descend stairs, walk up and down slopes as well as jog.

Electrically deformable materials have a long history, with first quotations in a letter from Alessandro Volta. The topic turned out to be hot at the end of the 19th century, with a landmark paper of Röntgen anticipating the dielectric elastomer principle. In 2000, Pelrine and co-workers generated huge interest in such soft actuators, by demonstrating voltage induced huge area expansion rates of more than 300%. Since then, the field became mature, with first commercial applications appearing on the market. New frontiers also emerged recently, for example by using dielectric transducers in a reverse mode for scavenging mechanical energy. In the present survey we briefly discuss the latest developments in the field.

In last few years, the rate of development and advances in the field of EAP has accelerated significantly and it is increasingly getting closer to the point of finding them used in commercial products. Substantial development has been reported in the understanding of their drive mechanisms and the parameters that control their electro-activation behavior. Further, efforts are being made to develop mass production techniques with greatly improved actuation capability and operation durability. The recent efforts to develop energy harvesting techniques, haptic interfacing (including refreshable braille displays), and toys are further increasing the likelihood of finding niches for these materials. In this paper, the author sought to examine the potential directions for the future development of the field of EAP in relation to the state-of-the-art.

Dielectric elastomers offer the promise of energy harvesting with few moving parts. Power can be produced simply by stretching and contracting a relatively low-cost rubbery material. This simplicity, combined with demonstrated high energy density and high efficiency, suggests that dielectric elastomers are promising for a wide range of energy harvesting applications. Indeed, dielectric elastomers have been demonstrated to harvest energy from human walking, ocean waves, flowing water, blowing wind, and pushing buttons. While the technology is promising, there are challenges that must be addressed if dielectric elastomers are to be a successful and economically viable energy harvesting technology. These challenges include developing materials and packaging that sustains long lifetime over a range of environmental conditions, design of the devices that stretch the elastomer material, as well as system issues such as practical and efficient energy harvesting circuits. Progress has been made in many of these areas. We have demonstrated energy harvesting transducers that have operated over 5 million cycles. We have also shown the ability of dielectric elastomer material to survive for months underwater while undergoing voltage cycling. We have shown circuits capable of 78% energy harvesting efficiency. While the possibility of long lifetime has been demonstrated at the watt level, reliably scaling up to the power levels required for providing renewable energy to the power grid or for local use will likely require further development from the material through to the systems level.

Dielectric elastomer energy harvesters are an emerging technology that promise high power density, low cost, scalability, and the capability of fitting niche markets that have yet to be exploited. To date, materials issues that limit their overall performance have hampered the full potential of these devices. In order to supplant existing technologies, even in niche markets, dielectric elastomer generators must increase their reliability and energy density. Previous work has indicated that stiffer elastomers should be capable of higher energy densities; the increased stiffness of the elastomer films should results in lower Maxwell pressure induced strains, and thus allow the elastomer to relax further, resulting in a larger swing in capacitance and larger energy gains. In this paper we examine the use of VHB-based acrylic interpenetrating polymer network dielectric elastomers with a trimethylolpropane trimethacrylate additive network for energy harvesting purposes. We test films with varying additive content and compare their performance with highly prestrained VHB acrylic elastomers. We show that by increasing additive content, Maxwell induced strains can be suppressed and larger energy gains can be achieved at higher bias fields. Moreover, the introduction of the additive network stabilizes the highly prestrained acrylic elastomers mechanically, thereby increasing their mechanical robustness. However, the interpenetrating polymer network films suffer from an increase in viscoelastic behavior that hinders their overall performance.

Recent energy harvesting research has developed dielectric elastomer (DE) energy harvesting devices for use in low frequency applications including waves, wind and human motion. The use of dielectric elastomers for energy harvesting is a growing field, which has great potential from an energy density viewpoint. While DE has shown promise for energy harvesting applications such as walking where the mechanical behavior could affect the user, there has been little investigation into the damping effects induced by DE energy harvesting. As devices capable of harvesting larger amounts of energy are developed harvesting-induced changes in the mechanical behavior of the dielectric must be investigated. This paper investigates the structural damping effects of DE energy harvesting in order to develop a more in-depth understanding of the changes in system response due to increased energy harvesting. Results relating energy harvesting strain and bias voltage to damping provide a framework for developing energy harvesting techniques which improve the overall performance of the system.

In this paper, we analyze underwater energy harvesting from the flutter instability of a heavy flag hosting an ionic polymer metal composite (IPMC). The heavy flag comprises a highly compliant membrane with periodic metal reinforcements to maximize the weight and minimize the bending stiffness, thus promoting flutter at moderately low flow speed. An IPMC strip is mechanically attached to the host flag and connected to an external load. The entire structure is immersed in a background flow whose intensity is parametrically varied to explore the onset of flutter instability along with the relation between the vibration frequency and the mean flow speed. Manageable theoretical models for fluid-structure interaction and IPMC response are presented to inform the harvester design and interpret experimental data. Further, optimal parameters for energy scavenging maximization, including resistive load and flow conditions, are identified.

The global demand for renewable energy is growing, and ocean waves and wind are renewable energy sources that can provide large amounts of power. A class of variable capacitor power generators called Dielectric Elastomer Generators (DEG), show considerable promise for harvesting this energy because they can be directly coupled to large broadband motions without gearing while maintaining a high energy density, have few moving parts, and are highly flexible. At the system level DEG cannot currently realize their full potential for flexibility, simplicity and low mass because they require rigid and bulky external circuitry. This is because a typical generation cycle requires high voltage charge to be supplied or drained from the DEG as it is mechanically deformed. Recently we presented the double Integrated Self-Priming Circuit (ISPC) generator that minimized external circuitry. This was done by using the inherent capacitance of DEG to store excess energy. The DEG were electrically configured to form a pair of charge pumps. When the DEG were cyclically deformed, the charge pumps produced energy and converted it to a higher charge form. In this paper we present the single ISPC generator that contains just one charge pump. The ability of the new generator to increase its voltage through the accumulation of generated energy did not compare favourably with that of the double ISPC generator. However the single ISPC generator can operate in a wider range of operating conditions and the mass of its external circuitry is 50% that of the double ISPC generator.

Dielectric Elastomer Generator(s) (DEG) have many unique properties that give them advantages over conventional electromagnetic generators. These include the ability to effectively generate power from slow and irregular motions, low cost, relatively large energy density, and a soft and flexible nature. For DEG to generate usable electrical energy circuits for charging (or priming) the stretched DEG and regulating the generated energy when relaxed are required. Most prior art has focused on the priming challenge, and there is currently very little work into developing circuits that address design issues for extracting the electrical energy and converting it into a usable form such as low DC voltages (~10 V) for small batteries or AC mains voltage (~100 V). This paper provides a brief introduction to the problems of regulating the energy generated by DEG. A buck converter and a charge pump are common DC-DC step-down circuits and are used as case studies to explore the design issues inherent in converting the high voltage energy into a form suitable for charging a battery. Buck converters are efficient and reliable but also heavy and bulky, making them suitable for large scale power generation. The smaller and simpler charge pump, though a less effective energy harvester, is better for small and discrete power generation. Future development in miniature DE fabrication is expected to reduce the high operational voltages, simplifying the design of these circuits.

Piezoelectric energy harvester (PEH) has been commonly considered as energy sources for self-reliant systems or wireless sensor nodes. They mainly consist a vibration source, an energy harvesting circuit and a storage device like battery. Currently, PEH suffers from low efficiency energy harvesting circuit and lack of battery model. Most of the energy harvesting circuits exploits switching techniques with inductor, which require peak detection or zero crossing detection. This paper discusses the balance between the harvested energy and the energy costs of the switching. In addition, a battery model is developed to predict the real-time charge on the battery.

The success of dielectric elastomer materials in actuator technology as well as in energy harvesting is much influenced by the material parameters, e.g. breakdown field, dielectric constant, and elastic modulus which have a direct impact on the driving voltage. By increasing the dielectric constant of a material the activation voltage can be decreased, however this increase is very often associated with a decrease in the breakdown field. In this proceeding, dielectric elastomer materials based on polydimethylsiloxanes with increased strain at break and high breakdown fields are presented.

Electro Active Polymers can be used as generators to convert mechanical strain energy into electrical energy. The relative energy gain basically depends on the capacity change induced by the mechanical strain, while the amount of energy gain requires a certain initial quantity of charges, which can be shown by analytical equations as well as by experimental tests. Because the harvested energy is reduced by electrical losses, an energy-optimal cycle is established under consideration of the overall system efficiency.

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.

Dielectric elastomer actuators are soft electro-mechanical transducers with possible uses in robotic, orthopaedic and automotive applications. The active material must be soft and have a high ability to store electrical energy. Hence, 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 with a higher dielectric constant, which can be classified as insulating or conducting. In this paper, an overview of all approaches proposed so far for dielectric constant improvement in these soft materials will be provided. Insulating particles such as TiO2 nanoparticles can raise the dielectric constant, but may also lead to stiffening of the composite, such that the overall actuation is lowered. It is shown here how a chemical coating of the TiO2 nanoparticles leads to verifiable improvements. Conducting material can also lead to improvements, as has been shown in several cases. Simple percolation, relying on the random distribution of conducting nanoparticles, commonly leads to drastic lowering of the breakdown strength. On the other hand, conducting polymer can also be employed, as has been demonstrated. We show here how an approach based on a specific chemical reaction between the conducting polymer and the elastomer network molecules solves the problem of premature breakdown which is otherwise typically found.

In recent years, many studies on electroactive polymer (EAP) actuators have been reported. One promising technology is the elaboration of electronic conducting polymers based actuators with Interpenetrating Polymer Networks (IPNs) architecture. Their many advantageous properties as low working voltage, light weight and high lifetime (several million cycles) make them very attractive for various applications including robotics. Our laboratory recently synthesized new conducting IPN actuators based on high molecular Nitrile Butadiene Rubber, poly(ethylene oxide) derivative and poly(3,4-ethylenedioxithiophene). The presence of the elastomer greatly improves the actuator performances such as mechanical resistance and output force. In this article we present the IPN and actuator synthesis, characterizations and design allowing their integration in a biomimetic vision system.

Recently micro-structured solid electrodes were applied to dielectric elastomers. Compared with common powder or liquid electrodes the electrical conductivity of the electrodes is enhanced while the compliance necessary for large active deformations is retained. Envisaged applications range from energy harvesting to structural damping and actuation. The compliant conducting electrodes can be attached to the passive dielectric materials in a standardized and well controlled process. This enhanced the general interest in the technology and more applications are expected. While some of these applications aim for maximum actuation performance others require a superior reliability at moderate performance. For both strategies design and optimization of the active parts are essential. This work provides results of an extensive experimental characterization of the passive and active response of a novel PolyPower membrane. We further developed a 3D nonlinear viscoelastic model suitable for finite element simulation and verified the main assumptions of the modeling approach with mechanical tests. The model is shown to provide good predictions of both passive behavior as well as active deformation of an actuator system.

A promising alternative of multi-layered devices showing electrochromic properties results from the design of a self-supported semi-interpenetrating polymer network (semi-IPN) including an electronic conductive polymer (ECP) formed within. The formation of the ECP in the network has already been described by oxidative polymerization using iron trichloride as an oxidant and leading to conducting semi-IPN with mixed electronic and ionic conductivities as well as convenient mechanical properties. This presentation relates to the elaboration of such semi-IPN using polyethyleneoxide (PEO) network or a PEO/NBR (Nitrile Butadiene Rubber) IPN in which a linear poly (3,4-ethylenedioxythiophene) (PEDOT) is formed symmetrically and selectively as very thin layers very next to the two main faces of the film matrix. PEO/PEDOT semi-IPNs lead to interesting optical reflective properties in the IR between 0.8 and 25 μm. Reflectance contrasts up to 35 % is observed when, after swelling in an ionic liquid, a low voltage is applied between the two main faces of the film. However the low flexibility and brittleness of the film and a slow degradation in air at temperature up from 60°C prompted to replace the PEO matrix by a flexible PEO/NBR IPN one. Indeed, the combination of NBR and PEO in an IPN leads to materials possessing flexible properties, good ionic conductivity at 25°C as well as a better resistance to thermal ageing. Finally, NBR/PEO/PEDOT semi-IPNs allow observing comparable reflectance contrast in the IR range than those shown by PEO/PEDOT semi-IPNs.

Silicone elastomers are highly suitable for application in the field of dielectric elastomer actuators (DEA) due to their unique material properties (e.g. low glass temperature, thermal stability, large capability of chemical tailoring). The elastomer forming Polydimethysiloxane (PDMS) employed for this study consists of chains with vinyl termination and is cross linked via hydrosilylation to a cross linking molecule in the presence of platinum catalyst. Here, dipole molecules (N-Allyl-N-methyl-4-nitroaniline) were specifically synthesized such that they could chemically graft to the silicone network. The most prominent advantage of this approach is the achievement of a homogeneous distribution of dipoles in the PDMS matrix and a suppression of phase separation due to the grafting to the junction points of the rubber network. Several films with dipole contents ν ranging from 0 %_wt up to 10.9 %_wt were prepared. The films were investigated to determine their mechanical (tensile testing), dielectric (dielectric relaxation spectroscopy) and electrical (electrical breakdown) properties. This new approach for composites on the molecular level leads to homogeneous films with enhanced material properties for DEA applications. An increase in permittivity from 3.3 to 6.0, a decrease in electrical breakdown from 130 V/μm to 50 V/μm and a lowering of the mechanical stiffness from 1700 kPa to 300 kPa was observed.

In this work we report an actuator material, that consist of carbon aerogel, 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIBF4) and poly(vinylidene-co-hexafluoropropylene) (PVdF(HFP)). Actuators were made by using layer-by-layer casting method and they work as a bending actuators. Carbon aerogel is synthesized from 5- methylresorcinol, which is a waste product in oil-shale industry. It makes the material "environmentally green". Carbon aerogels have a very low density and considerable specific surface area. It is generally understood that the large interfacial surface area of electrodes gives rise to better actuation performance; therefore, designing actuators with high specific surface area electrodes is of interest. The assembled three layer actuators require low voltage to operate and work steadily in open air due to non-volatile electrolyte. The electromechanical and electrical characteristics of prepared actuators were examined and compared to our previously reported actuators based on the carbide-derived carbon and activated carbon electrodes. The differences in actuation performance were analyzed in the context of pore characteristics and degree of graphitization of carbons. The gas sorption measurements were performed to characterize pore size distribution. These actuators show high strain, low back-relaxation and low power consumption and they are good for slow-response applications compared to carbon nanotube actuators.

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 behavior of dielectric elastomer actuators in general is not known or has not been published. The first goal of the study is to characterize the overall lifetime under laboratory conditions and to identify potential factors influencing lifetime. For this we have designed a test setup to examine 16 actuators at once. The actuators are subdivided into 4 groups each with a separate power supply and driving signal. To monitor the performance of the actuators driving voltage and current are measured continuously and additionally, the amplitude of the deformations of each actuator is measured sequentially. From our first results we conclude that lifetime of these actuators is mainly influenced by the contact 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 2700 h at 200 Hz with an electrical field strength of 20 V/μm. This results in more than 3 billion cycles. Actually, there are further actuators driven at 10 Hz for more than 4000 hours and still working.

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. In cantilever configuration, while low voltage (3 V) is applied to these electrodes, the CPC sheet undergoes bending. To date, virtually no research into sensing properties of these materials has been conducted. In order to determine the tip displacement (curvature) of the CPC actuator, change of surface resistance in the process of bending is measured. Within the scope of this paper, it is also to investigate whether the acquired signals are feasible for use as a feedback to the actuator's driving mechanism and thus creating a self-sensing CPC device. Experimental data is presented to report that both resistive and capacitive effects are present on surface electrodes and alter during the actuator's work-cycle.

Miniaturizing dielectric electroactive polymer (EAP) actuators will lead to highly-integrated mechanical systems on a chip, combining dozens to thousands of actuators and sensors on a few cm2. We present here µm to mm scale electroactive polymer (EAP) devices, batch fabricated on the chip or wafer scale, based on ion-implanted electrodes. Low-energy (2-10 keV) implantation of gold ions into a silicone elastomer leads to compliant stretchable electrodes consisting of a buried 20 nm thick layer of gold nanoparticles in a silicone matrix. These electrodes: 1) conduct at strains up to 175%, 2) are patternable on the µm scale, 3) have stiffness similar to silicone, 4) have good conductivity, and 5) excellent adhesion since implanted in the silicone. The EAP devices consist of 20 to 30 µm thick silicone membranes with µm to mm-scale ion-implanted electrodes on both sides, bonded to a holder. Depending on electrode shape and membrane size, several actuation modes are possible. Characterization of 3mm diameter bi-directional buckling mode actuators, mm-scale tunable lens arrays, 2-axis beam steering mirrors, as well as arrays of 72 cell-size (100x200 µm2) actuators to apply mechanical strain to single cells are reported. Speeds of up to several kHz are observed.

Electrical breakdown due to electro-mechanical instability is the main intrinsic failure mechanism of dielectric elastomer actuators (DEA). The same mechanism may also be responsible for failure in soft insulating materials for other high voltage applications. We report on the validation of a model determining the electrical breakdown in dependence of material properties. The model includes hyper-elastic material behavior and includes a proper description of the experimental boundary condition.

In this paper we present a transparent and stretchable dielectric elastomer actuator(DEA). The device, called "active skin" is under development as a new means of human interfaces. The active skin consists of elastomeric films sandwiched between compliant patterned electrodes. Thus, depending on the properties of the elastomer or electrodes, it is possible to realize a wide variety of implementations as transducers. As a critical issue of the transparent active skin, transparency in the electrode including that of the substrate is challenging, which has not been solved yet. In this paper, a compliant, transparent and highly conductive electrode layer on the elastomeric film by using graphene is presented. The fabrication method of graphene electrodes dedicated to the elastomeric materials is addressed and its compatibility to the existing materials is discussed. Also, preliminary implementations on the embossed actuator are given to validate the proposed idea.

We present the design, fabrication process and characterization of multilayer miniaturized polydimethylsiloxane (PDMS)-based dielectric elastomer diaphragm actuators. The conductive stretchable electrodes are obtained by lowenergy metal ion implantation. To increase force, decrease the required voltage, and avoid dielectric breakdown, we present here a technique to fabricate multilayer devices with embedded electrodes with complex shapes. By implanting electrodes on a partially cured PDMS film, then casting on it the next layer of PDMS, it is possible to have the compliant electrodes "molded" inside PDMS. Using custom shadow masks allows defining electrodes of any shape or size, we report sizes down to 0.1 mm. The minimal distance between independent electrodes inside the PDMS is limited solely by the breakdown voltage of PDMS and can be also as small as 0.1 mm. Using this approach, we have fabricated miniature compact devices consisting of several independent dielectric elastomer actuators on a single PDMS film. Applying different voltages to the separate actuators allows to achieve complicated movements of the whole device, e.g. to act as a 3-DOF parallel manipulator. A distinctive feature of the multi-layer actuators is that they attain similar strain with lower voltage than the single-layer actuators of the same thickness. We report on a 3 mm diameter 2-axis beam steering device combining three actuators.

A stacked dielectric elastomer actuator (DEA) consists of multiple layers of elastomeric dielectrics interleaved with compliant electrodes. It is capable of taking a tensile load if only the interleaving compliant electrodes provide a good bonding and enough elasticity. However, the stacked configuration of DEA was found to produce less actuation strain as compared to a single-layer configuration of pre-stretched membrane. It is believed the binder for compliant electrodes has a significant influence on the actuation strain. Yet, there has yet systematic study on the effect of binder. In this paper, we will study the effects of binder, solvent, and surface fictionalization on the compliant electrodes using the conductive filler of Multi-Walled Carbon Nanotube (MWCNT). Two types of binders are used, namely a soft silicone rubber (Mold Max 10T) and a soft silicone gel (Sylgard 527 gel). The present experiments show that the actuators using binders in the compliant electrodes produce a much lower areal strain as compared to the ones without binders in them. It is found that introducing a binder in the electrodes decreases the conductivity. The MWCNT compliant electrode with binder remains conductive (<1TΩ) up to a strain of 300%, whereas the one without binder remains conductive up to a strain of 800%. Changing the type of binder to a softer and less-viscous one increases the percolation ratio for MWCNT-COOH filler from 5% to 15% but this does not significantly increase the actuation strain. In addition, this study investigates the effect of MWCNT functionalization on the dielectric elastomeric actuation. The compliant electrodes using the MWCNT functionalized with (-COOH) group was also found to have a lower electrical conductivity and areal actuation strain, in comparison to the ones using the pristine MWCNT filler. In addition to binder, solvent for dispersing MWCNT-COOH was found to affect the actuation strain even though the solvent is eventually removed by evaporation from the MWCNT-COOH electrode. The actuators with MWCNT-COOHs electrodes, prepared from the solvent dispersion, produce a low actuation strain even though these electrodes have good conductivity and these solvents do not degrade the physical properties of the dielectric layer. This finding on the solvent effect has yet been clearly understood.

So-called 'hydrostatically coupled' dielectric elastomer actuators (HC-DEAs) have recently been shown to offer new opportunities for actuation devices made of electrically responsive elastomeric insulators. HC-DEAs include an incompressible fluid that mechanically couples a dielectric elastomer based active part to a passive part interfaced to the load, so as to enable hydrostatic transmission. Drawing inspiration from that concept, this paper presents a new kind of actuators, analogous to HC-DEAs, except for the fact that the fluid is replaced by fine powder. The related technology, here referred to as 'granularly coupled' DEAs (GC-DEAs), relies entirely on solid-state materials. This permits to avoid drawbacks (such as handling and leakage) inherent to usage of fluids, especially those in liquid phase. The paper presents functionality and actuation performance of bubble-like GC-DEAs, in direct comparison with HC-DEAs. For this purpose, prototype actuators made of two pre-stretched membranes of acrylic elastomer, coupled via talcum powder (for GC-DEA) or silicone grease (for HC-DEA), were manufactured and comparatively tested. As compared to HC-DEAs, GC-DEAs showed a higher maximum stress, the same maximum relative displacement, and nearly the same bandwidth. The paper presents characterization results and discusses advantages and drawbacks of GC-DEAs, in comparison with HC-DEAs.

A synthetic chemical strategy aimed at altering the cross-linking density of the electropolymerized conjugated polymer polypyrrole has been devised and implemented. The actuation performance of the synthesized material was assessed using a new type of apparatus capable of making rapid, non-contact dynamic measurements. The affect of cross-linking on the actuation performance of polypyrroles, was investigated.

Refreshable tactile displays can significantly improve the education of blind children and the quality of life of people with severe vision impairment. A number of actuator technologies have been investigated. Bistable Electroactive Polymer (BSEP) appears to be well suited for this application. The BSEP exhibits a bistable electrically actuated strain as large as 335%. We present improved refreshable tactile display devices fabricated on thin plastic sheets. Stacked BSEP films were employed to meet the requirements in raised dot height and supporting force. The bistable nature of the actuation reduces the power consumption and simplifies the device operation.

Refreshable Braille displays require many, small diameter actuators to move the pins. The electrostrictive P(VDF-TrFECFE) terpolymer can provide the high strain and actuation force under modest electric fields that are required of this application. In this paper, we develop core-free tubular actuators and integrate them into a 3 × 2 Braille cell. The films are solution cast, stretched to 6 μm thick, electroded, laminated into a bilayer, rolled into a 2 mm diameter tube, bonded, and provided with top and bottom contacts. Experimental testing of 17 actuators demonstrates significant strains (up to 4%). A novel Braille cell is designed and fabricated using six of these actuators.

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 simultaneously. The work we present in this paper is focused on the implementation of a DEA-based tactile display into a mobile device. The generation of the driving voltage of up to 1.1 kV out of a common rechargeable battery and the implementation of the sensor functionality are the most challenging tasks. To realize a large range of tactile experiences, both static and dynamic driving voltages are required. We present a structure combining different step-up topologies to realize the driving unit. The final circuitry complies with typical requirements for mobile devices, like small size, low weight, high efficiency and low costs. The sensing functionality has to be realized for different actuator elements regardless of their actual state. An additional sensing layer on top or within the actuators would cause a higher fabrication effort and additional interconnections. Therefore, we developed a high voltage compatible sensing system. The circuitry allows sensing of user input at every actuator element. Both circuits are implemented into a handheld-like device.

This paper reports a new method to prepare organic-inorganic hybrid Nafion/SiO2 membranes by adding different contents (0 %, 0.5 %, 1 %, 1.5 %) of tetraethyl orthosilicate (TEOS) into the perfluorosulfonic acid ionomer, which are applied to fabricate ionic polymer metal composites (IPMCs). The water contents were calculated, the cross sections of Nafion membranes were observed with scanning electron microscopy (SEM). Starting from cast Nafion membranes, IPMCs were fabricated by electroless plating. Furthermore, the blocking force of IPMCs were measured on the test apparatus. The results showed that as the TEOS content gradually increased, the blocking force increased. When TEOS content was 1.5 %, IPMC showed the best improved mechanical property.

The present study investigates the frequency response of IPMC actuator. By using the electroless plating method, IPMC actuator with palladium electrode was obtained in 60 minutes, which was shorter than the conventional fabrication time. In the observation of response to step voltages, IPMC actuator with palladium electrode showed larger deformation and slower backward motion than the conventional IPMC actuators with platinum electrode. In the experiments of frequency response, IPMC actuator showed the resonance phenomenon at a specified frequency, and the resonance frequency could be predicted by the simple cantilever beam model. Then, the phase shift increased drastically when the resonance phenomena were observed. Finally, the frequency response of IPMC actuator was modeled by using the transfer function.

Ionic polymer metal composites (IPMC) are a low-voltage driven Electroactive Polymers (EAP) that can be used as actuators or sensors. This paper presents a comparative study of millimeter thick ionic polymer membrane-based IPMCs with high-performance Pd-Pt electrodes and conventional Pt electrodes. IPMCs assembled with different electrodes are characterized in terms of electromechanical, -chemical and mechanolelectrical properties. The SEM and energy dispersive X-ray (EDS) analysis are used to investigate the distribution of deposited electrode metals in the cross-section of Pd-Pt IPMCs. The study shows that IPMCs assembled with millimeter thick ionic polymer membranes and bimetallic Pd-Pt electrodes are superior in mechanoelectrical sensing and, also, show considerably higher blocking forces compared to the conventional type of IPMCs. Blocking forces more than 30 grams are measured under 4V DC. However, the actuation response is slower than conventional IPMCs having approximately 0.2-0.3 mm thickness.

Polyvinylidene fluoride (PVDF) based electrostrictive electroactive polymers (EAPs) have many advanced features such as large strain, high elastic modulus, and millisecond response time which make them suitable for high performance actuator applications. Recently, polymer blends of poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) (P(VDF-TrFE-CFE)) terpolymers and other polymers have been developed, exhibiting an elastic modulus of 700 MPa and electromechanical strain of 2.5% under an electric field of 100 V/μm, yielding a large elastic energy density. These EAPs are of great promise in many actuator applications requiring compact size and flexible structure while maintaining a large mechanical energy output. To reduce operation voltage, ultrathin films with thickness down to 3 μm have been developed. Multilayer thin film structures have been fabricated for an increase in force output. With these developments, several commercial actuator applications can be realized, including micro-steerable catheters and tactile feedback systems. Micro-steerable catheters, with large bending angles, fast response, and reasonable lifetime are demonstrated. Tactile feedback actuators with high force and acceleration over the haptic frequency range from 100-300 Hz are demonstrated with a single layer of EAP film.

Haptic is one of well-considered device which is suitable for demanding virtual reality applications such as medical equipment, mobile devices, the online marketing and so on. Nowadays, many of concepts for haptic devices have been suggested to meet the demand of industries. Cellulose has received much attention as an emerging smart material, named as electro-active paper (EAPap). The EAPap is attractive for mobile haptic devices due to its unique characteristics in terms of low actuation power, suitability for thin devices and transparency. In this paper, we suggest a new concept of haptic actuator with the use of cellulose EAPap. Its performance is evaluated depending on various actuation conditions. As a result, cellulose electrostatic force actuator shows a large output displacement and fast response, which is suitable for mobile haptic devices.

As a means to improve versatility and safety of dielectric elastomer actuators (DEAs) for several fields of application, so-called 'hydrostatically coupled' DEAs (HC-DEAs) have recently been described. HC-DEAs are based on an incompressible fluid that mechanically couples a DE-based active part to a passive part interfaced to the load, so as to enable hydrostatic transmission. This paper presents ongoing developments of HC-DEAs and potential applications in the field of haptics. Three specific examples are considered. The first deals with a wearable tactile display used to provide users with tactile feedback during electronic navigation in virtual environments. The display consists of HCDEAs arranged in contact with finger tips. As a second example, an up-scaled prototype version of an 8-dots refreshable cell for dynamic Braille displays is shown. Each Braille dot consists of a miniature HC-DEA, with a diameter lower than 2 mm. The third example refers to a device for finger rehabilitation, conceived to work as a sort of active version of a rehabilitation squeezing ball. The device is designed to dynamically change its compliance according to an electric control. The three examples of applications intend to show the potential of the new technology and the prospective opportunities for haptic interfaces.

Conducting polymer materials can be employed as actuation elements, length sensors, force sensors, energy storage devices, and electrical components. Combining the various functionalities of conducting polymers to create singlesubstrate, integrated systems remains a challenge, as chemical and electrical insulation barriers, adhesion techniques, and the possibility of scaling need to be taken into consideration. Here fabrication techniques for combining multiple conducting polymer components by means of electrically insulated, mechanical attachments are developed. Electrochemically synthesized polypyrrole substrates were coated with thin films of polystyrene, Parylene, and polyimide. The isotonic actuation performance of each coated film was evaluated in comparison to non-coated films, with an observed decrease in peak-to-peak maximum strain output near 95% (polystyrene and Parylene), 20% (vacuum, 0.8 Pa), 50% (curing at 110°C) and 20% (localized polyimide deposition). The chemical barrier properties of each manufacturing technique were evaluated by exposing the coated polypyrrole substrates to an oxidative chemical vapor deposition of Poly(3,4-ethylenedioxythiophene) (PEDOT). Vapor-deposited PEDOT made the insulation layers of polystyrene and Parylene conductive at thicknesses up to four microns. Spin-coated films of polyimide, greater than ten microns thick, maintained electrical insulation properties after PEDOT depositions. Conducting polymer film-to-film attachments using each manufacturing technique were attempted, with polyimide working successfully when employed under a specific deposition, drying, and curing protocol, as discussed. Three dimensional conducting polymer actuation systems composed of actuators, length sensors, and energy storage devices were constructed on flexible, single substrates. These results build a foundation upon which scalable, self-powered, polymer actuation systems can be developed.

This paper presents two new methods for the segmentation of ionic polymer metal composites (IPMCs) in order to create sophisticated multi-segment sensor-actuators. The first method is based on the application of a heated stylus which, through a combination of water vaporization and melting of the Nafion substrate removes and redistributes electrode material. The second method is based on spark discharge machining; a process used in industry to machine extremely hard conducting materials such as titanium and pre-hardened steel. In contrast to previous segmentation methods including laser ablation, machining and manual scraping these methods are extremely inexpensive, safe, accurate and quick. Spark discharge segmentation in particular is an attractive method due to its self-limiting nature, which makes it robust to variations in segmentation speed and applied pressure. These two methods are presented and assessed through the fabrication of a series of multi-segment actuators. Actuation results are presented for a two segment spark-discharge segmented cilia-like IPMC actuator.

Dielectric polymer actuators promise to revolutionize user interfaces by enabling surface actuators that can change surface shape and give tactile feedback from a thin layer. We have realized a programmable surface actuator, based on non-pre-stretched silicone, which is capable of realizing large freeform surface deformations from relatively thin layers, while maintaining very good control over the shape of the actuated surface. Moreover, the actuator setup allows the use of a thin, stiff top layer, which addresses friction and stickiness problems commonly associated with using soft elastomers in tactile displays. Out-of-plane deformations exceeding 300 μm are possible, facilitating 'tactile exploration' of the actuated shapes.

While much of the research on dielectric elastomer actuators used to concentrate on VHB 4910 as dielectric material, lately many new, specifically developed materials have come into focus. The acrylic VHB has been thoroughly characterized in a macro-scale agonist-antagonist configuration on an active hinge. This was carried out with the aim of using it on an airship, which was activated, undulating body and a fin and thus propelled in a fish-like manner. The concept was proved in flight, but still lifetime and viscosity of the actuators and the time-costing fabrication due to the necessary large pre-stretches of the dielectric membrane caused severe inconveniences. In order to evaluate the usability of other materials for this specific purpose, two other materials, a corrugated silicone with silver electrodes (by PolyPower) and an acrylic with interpenetrating network (IPN) developed by Pei et al. were characterized under similar conditions. The influence of the material on performance and design of the actuators and the conclusions for the use of the materials on the airship (and on applications with similar performance requirements) are presented.

When using smart actuators, an appropriate power electronics and a well designed force control are necessary in order to established a common force interface. Driving the actuators at high voltages and typically low currents requires special topologies, which have to meet the necessity of a bidirectional energy flow, a high efficiency and bandwidth. An inverter topology is presented, which is modeled afterwards in order to design a high dynamic voltage controller. For the force control of Dielectric Elastomer Actuators, the nonlinear relations between voltage and Maxwell stress as well as the mechanical hysteresis have to be compensated. The resulting open-loop force control can be used for superimposed motion controls, such as position, vibration and impedance controls.

Dielectric elastomers (DE) have proved to have high potential for smart actuator applications in many laboratory setups and also in first commercially available components. Because of their large deformation capability and the inherent fast response to external stimulation they proffer themselves to applications in the field of active vibration control, especially for lightweight structures. These structures typically tend to vibrate with large amplitudes even at low excitation forces. Here, DE actuators seem to be ideal components for setting up control loops to suppress unwanted vibrations. Due to the underlying physical effect DE actuators are generally non-linear elements with an approximately quadratic relationship between in- and output. Consequently, they automatically produce higher-order frequencies. This can cause harmful effects for vibration control on structures with high modal density. Therefore, a linearization technique is required to minimize parasitic effects. This paper shows and quantifies the nonlinearity of a commercial DE actuator and demonstrates the negative effects it can have in technical applications. For this purpose, two linearization methods are developed. Subsequently, the actuator is used to implement active vibration control for two different mechanical systems. In the first case a concentrated mass is driven with the controlled actuator resulting in a tunable oscillator. In the second case a more complex mechanical structure with multiple resonances is used. Different control approaches are applied likewise and their impact on the whole system is demonstrated. Thus, the potential of DE actuators for vibration control applications is highlighted.

An accurate physical-based electromechanical model of a commercially available tubular dielectric elastomer actuator has been developed at University of Southern Denmark. This model has been validated for a range of different periodic input voltage signals as well as for different loading conditions. In this contribution we are interested in seeing how the physical-based electromechanical model can be used directly within a model-based control scheme. The choice of control scheme was dictated by the desire for transparency in both controller design and operation. The Internal Model Control (IMC) approach, which is based on the Internal Model Principle, which states that 'control can be achieved only if the control system encapsulates, either implicitly or explicitly, some representation of the process to be controlled' was chosen. If the IMC approach is implemented based on an exact model of the plant, perfect control is theoretically possible. IMC -based control is investigated for servo control of the dielectric elastomer actuator position as well as its ability to reject disturbances. The approach comprises (a) the use of the DE actuator model in parallel to the real actuator - the difference between the two outputs providing an estimate of any disturbance entering the system, (b) the estimated disturbance being fed back and compared with the reference input and (c) the difference between the reference and the estimated disturbance provides the input to the IMC controller which is based on an inverse model of the DE actuator. In the IMC implementation considered here the full nonlinear electromechanical model of the actuator is used to provide the disturbance estimate. The use of a linearizing gain scheduler, placed in series with the real actuator, allows a linearized inverse of the electromechanical model to be used in the formulation of the IMC controller.

Dielectric elastomer actuators are suited for the fabrication of gas valves in micro systems. Based on the application of a micro burner unit a complete valve, consisting of the seat, the actuator and a spring structure to produce the closing force, is designed and evaluated. The required flow rate and the allowed pressure drop are derived and used to define the design of the valve seat, actuator and spring structure. This includes dimensions and shape of the valve seat with the outlet and channels for the gas flow. One valve in 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. For the fabrication a Top-Down process was chosen. The dielectric elastomer actuator is directly fabricated onto a sacrificial substrate containing the spring structure and finally assembled with the valve seat by an plasma bonding process. The fabricated valves are characterized in respect of achieved deflection and flow rates.

An electrochemical actuator demands that it should act as a sensor of the working conditions for its efficient application in devices. Actuation and sensing characteristics of a biopolymer/conducting polymer hybrid microfiber artificial muscle fabricated through wet spinning of a chitosan solution followed by in situ chemical polymerization with pyrrol employing bis(triflouro methane sulfonyl) imide as dopant and ferric chloride as a catalyst is presented. The polypyrrol/chitosan hybrid microfiber was investigated by FTIR, scanning electron microscopy (SEM), electrical conductivity measurement, cyclic voltammetric and chronopotentiometric methods. The electrochemical measurements related to the sensing abilities were performed as a function of applied current, concentration and temperature keeping two of the variables constant at a given time using NaCl as electrolyte. Cyclic voltammograms confirmed that the electro activity is imparted by polypyrrol (pPy). The fiber showed an electrical conductivity of 3.21x10^-1 Scm^-1and an average linear electrochemical actuation strain of 0.54%. The chronopotentiometric responses during the oxidation/reduction processes of the microfiber for the different anodic/cathodic currents and the linear fit observed for the consumed electrical energy during the reaction for various applied currents suggested that it can act as a sensor of applied current. The chronopotentiometric responses and the linear fit of consumed electrical energy at different temperatures suggested that the actuator can act as a temperature sensor. Similarly a semi logarithmic dependence of the consumed electrical energy with concentration of the electrolyte during reaction is suggestive of its applicability as a concentration sensor. The demand that an electrochemical actuator to be a sensor of the working conditions, for its efficient application in devices is thus verified in this material.

The constitutive relation and electromechanical stability of Varga-Blatz-Ko-type compressible isotropic dielectric elastomer is investigated in this paper. Free-energy in any form, which consists of elastic strain energy and electric energy, can be applied to analyse the electromechanical stability of dielectric elastomer. The constitutive relation and stability is analyzed by applying a new kind of free energy model, which couples elastic strain energy, composed of Varga model as the volume conservative energy and Blatz-Ko model as the volume non-conservative energy, and electric field energy with constant permittivity. The ratio between principal planar stretches m(t₀) (λ₂ = m(t₀)λ₁), the ratio between thickness direction stretch and length direction stretch 0 n(t₀) (λ₃ = n(t₀)λ₁ ), and power exponent of the stretch k(t₀) are defined to characterize the mechanical loading process and compressible behavior of dielectric elastomer. Along with the increase of material parameters m(t₀) , n(t₀) , k(t₀) and poison ratioV , the nominal electric field peak is higher. This indicates that the dielectric elastomer electromechanical system is more stable. Inversely, with the increase of the material parameter α , the nominal electric field peak, critical area strain and the critical thickness strain increase, coupling system is more stable.

Hydrogels are viscoelastic active materials. They consist of a polymer network with bound charges and a liquid phase with mobile anions and cations. In water based solutions these gels show large swelling capabilities under the influence of different possible stimulation types, such as chemical, electrical or thermal stimulation. In the present work a coupled chemo-electro-mechanical formulation for polyelectrolyte gels using the Finite Element Method (FEM) is applied. In addition to the three given fields, the dissociation reactions of the bound charges in the gel are considered. Thus, we are able to model and simulate pH-stimulation and to give the different ion concentrations, the electric potential and the mechanical displacement. Depending on the initial conditions and the dissociation ratio, different kinds of stimulation cycles can be simulated. Concluding, the developed model is applicable for chemical stimulation and can model both, hydrogel actuators and sensors.

A curvature sensor based on Ionic Polymer-Metal Composite (IPMC) is proposed and characterized for sensing of curvature variation in structures such as inflatable space structures in which using low power and flexible curvature sensor is of high importance for dynamic monitoring of shape at desired points. The linearity of output signal of sensor for calibration, effect of deflection rate at low frequencies and the phase delay between the output signal and the input deformation of IPMC curvature sensor is investigated. An analytical chemo-electro-mechanical model for charge dynamic of IPMC sensor is presented based on Nernst-Planck partial differential equation which can be used to explain the phenomena observed in experiments. The rate dependency of output signal and phase delay between the applied deformation and sensor signal is studied using the proposed model. The model provides a background for predicting the general characteristics of IPMC sensor. It is shown that IPMC sensor exhibits good linearity, sensitivity, and repeatability for dynamic curvature sensing of inflatable structures.

The Biomimetics Laboratory has developed a soft artificial muscle motor based on Dielectric Elastomers. The motor, 'Flexidrive', is light-weight and has low system complexity. It works by gripping and turning a shaft with a soft gear, like we would with our fingers. The motor's performance depends on many factors, such as actuation waveform, electrode patterning, geometries and contact tribology between the shaft and gear. We have developed a finite element model (FEM) of the motor as a study and design tool. Contact interaction was integrated with previous material and electromechanical coupling models in ABAQUS. The model was experimentally validated through a shape and blocked force analysis.

Smart materials are active and multifunctional materials, which play an important part for sensor and actuator applications. These materials have the potential to transform passive structures into adaptive systems. However, a prerequisite for the design and the optimization of these materials is, that reliable models exist, which incorporate the interaction between the different combinations of thermal, electrical, magnetic, optical and mechanical effects. Polymeric electroelastic materials, so-called electroactive polymer (EAP), own the characteristic to deform if an electric field is applied. EAP's possesses the benefit that they share the characteristic of polymers, these are lightweight, inexpensive, fracture tolerant, elastic, and the chemical and physical structure is well understood. However, the description "electroactive polymer" is a generic term for many kinds of different microscopic mechanisms and polymeric materials. Based on the laws of electromagnetism and elasticity, a visco-electroelastic model is developed and implemented into the finite element method (FEM). The presented three-dimensional solid element has eight nodes and trilinear interpolation functions for the displacement and the electric potential. The continuum mechanics model contains finite deformations, the time dependency and the nearly incompressible behavior of the material. To describe the possible, large time dependent deformations, a finite viscoelastic model with a split of the deformation gradient is used. Thereby the time dependent characteristic of polymeric materials is incorporated through the free energy function. The electromechanical interactions are considered by the electrostatic forces and inside the energy function.

This paper presents a study of IPMCs for twisting motion. To accomplish the twisting electromechanical transduction of IPMC, patterned electrodes were used. Here we present a three dimensional (3D) finite element (FE) model based on the fundamental physical principles. Due to very high aspect ratio of the dimensions of IPMC materials, constructing a full scale 3D model that includes charge transport, continuum mechanics, and electrostatics equations for the electrodes is challenging. Therefore, a process where some of the data is calculated in a scaled 2D domain and is later used to calculate the mechanoelectrical transduction in a full scale 3D domain is presented. The modeling results are compared to experimentally measured data. In the second part of the paper, the twisting mechanoelectrical transduction study of the IPMCs is introduced. A 3D FE model, again based on the fundamental physical principles, was developed to estimate the generated charge. In case of the mechanoelectrical transduction simulations, the full model was calculated in a 3D domain.

We use our thumbs and forefingers to rotate an object such as a control knob on a stereo system by moving our finger relative to our thumb. Motion is imparted without sliding and in a precise manner. In this paper we demonstrate how an artificial muscle membrane can be used to mimic this action. This is achieved by embedding a soft gear within the membrane. Deformation of the membrane results in deformation of the polymer gear and this can be used for motor actuation by rotating the shaft. The soft motors were fabricated from 3M VHB4905 membranes 0.5mm thick that were pre-stretched equibiaxially to a final thickness of 31 μm. Each membrane had polymer acrylic soft gears inserted at the center. Sectors of each membrane (60° sector) were painted on both sides with conducting carbon grease leaving gaps between adjoining sectors to avoid arcing between them. Each sector was electrically connected to a power supply electrode on the rigid acrylic frame via narrow avenues of carbon-grease. The motors were supported in rigid acrylic frames aligned concentrically. A flexible shaft was inserted through both gears. Membranes were charged using a step wave PWM voltage signal delivered using a Biomimetics Lab EAP Control unit. Both membrane viscoelasticity and the resisting torque on the shaft influence motor speed by changing the effective circumference of the flexible gear. This new soft motor opens the door to artificial muscle machines molded as a single part.

Recently, stacked dielectric polymer actuators have gained a lot of attention as MEMS actuators. In this paper we present a new kind of in-plane stack actuator. In contrast to its multilayer counterparts, it consists of only one active layer with inter-digitated microstructured soft electrodes which allow for a linear, radial or even asymmetric pulling motion in the working plane. The single layer design makes it in principle compatible with standard MEMS processes like deep reactive ion etching as well as silicone casting for optical components. Nevertheless, the wafer level fabrication process does not require any photolithography or clean room processes. The actuator consists of a microstructured layer of carbon black or nanotube filled PDMS which is suspended over a KOH etched trench on a (111) silicon wafer. The conductive PDMS electrodes are structured by laser ablation and subsequently embedded in a dielectric. The use of a (111) silicon wafer enables a mask less definition of the trench as the (111) layer is almost not attacked by the KOH etchant. The trench is defined by laser induced damage of the silicon wafer, so only exposed areas are etched. This allows for a true rapid prototyping of actuators with a fabrication time of less than one day.

This study describes modeling and computational analysis technique for design of humanoid head that can generate human-like facial expression. Current humanoid prototypes utilize either traditional servo motors or other form of bulky actuators such as air muscles to deform soft elastomeric skin that in turn creates facial expression. However, these prior methods have inherent drawbacks and do not resemble human musculature. In this paper, we report the advances made in design of humanoid head using shape memory alloy actuators. These muscle-like actuators are often in discrete form and finite in number. This brings up the fundamental question regarding their arrangement and location of terminating and sinking points for each action unit. We address this question by developing a Graphical Facial Expression Analysis and Design (GFEAD) technique that can be used to optimize the space, analyze the deformation behavior, and determine the effect of actuator properties. GFEAD will be described through generic mathematical models and analytical geometry confining the discussion to two-dimensional planes. The implementation of the graphical method will be presented by considering different practical cases.

It has been found that by introducing defects into the P(VDF-TrFE) copolymers, it is possible to convert the polymer from a normal ferroelectric to a relaxor ferroelectric. A new class of ferroelectric polymers, i.e., the terpolymers of P(VDF-TrFE-CFE) or of P(VDF-TrFE-CTFE), was developed from the normal ferroelectric PVDF-TrFE polymer by employing proper defect modifications which eliminate detrimental effects associated with a normal first order F-P transition while maintaining high material responses. Relevant studies show that this class of electroactive polymers offers unique properties in comparison with other ferroelectric polymers. The syntheses of these relaxor ferroelectric polymers have been done by a combination of the suspension polymerization process and an oxygen-activated initiator at a temperature of 40 °C. Films from cast solution can be made in different length and thicknesses. Stretching of these films increases the performance as well as the mechanical properties. These relaxor-ferroelectric terpolymers P(VDF-TrFE-CFE), P(VDF-TrFE-CTFE) are multifunctional i.e. electrostrictive material, dielectric for electric energy storage. The terpolymer exhibits high electrostrictive strain (>7%) with relatively high modulus (>0.4GPa). Examples of devices applications using unimorphe systems are presented. Micropump and Optical device concerning a liquid-filled varifocal lens on a chip are described.

For optimal performance, actuators designed for biologically-inspired robotics applications need to be capable of mimicking the key characteristics of natural musculoskeletal systems. These characteristics include a large output stroke, high energy density, antagonistic operation and passive compliance. The actuation properties of dielectric elastomer actuators (DEAs) make them viable for use as an artificial muscle technology. However, much like the musculoskeletal system, rigid structures are needed to couple the compliant DEA layers to a load. In this paper, a cone DEA design is developed as an antagonistic, multi-DOF actuator, viable for a variety for biologically-inspired robotics applications. The design has the advantage of maintaining pre-strain through a support structure without substantially lowering the overall mass-specific power density. Prototype cone DEAs have been fabricated with VHB 4910 acrylic elastomer and have characteristic dimensions of 49mm (strut length) and 60mm (DEA diameter). Multi-DOF kinematical outputs of the cone DEAs were measured using a custom 3D motion tracking system. Experimental tests of the prototypes demonstrate antagonistic linear (±10mm), rotational (±25°) and combined multi-DOF strokes. Overall, antagonistic cone DEAs are shown to produce a complex multi-DOF output from a mass-efficient support structure and thus are well suited for being exploited in biologically-inspired robotics.

Sensing the electrical characteristics of a Dielectric Elastomer Actuator(s) (DEA) during actuation is critical to improving their accuracy and reliability. We have created a self-sensing system for measuring the equivalent series resistance of the electrodes, leakage current through the equivalent parallel resistance of the dielectric membrane, and the capacitance of the DEA whilst it is being actuated. This system uses Pulse Width Modulation (PWM) to simultaneously generate an actuation voltage and a periodic oscillation that enables the electrical characteristics of the DEA to be sensed. This system has been specifically targeted towards low-power, portable devices. In this paper we experimentally validate the self-sensing approach, and present a simple demonstration of closed loop control of the area of an expanding dot DEA using capacitance feedback.

Life shows us that the distribution of intelligence throughout flexible muscular networks is a highly successful solution to a wide range of challenges, for example: human hearts, octopi, or even starfish. Recreating this success in engineered systems requires soft actuator technologies with embedded sensing and intelligence. Dielectric Elastomer Actuator(s) (DEA) are promising due to their large stresses and strains, as well as quiet flexible multimodal operation. Recently dielectric elastomer devices were presented with built in sensor, driver, and logic capability enabled by a new concept called the Dielectric Elastomer Switch(es) (DES). DES use electrode piezoresistivity to control the charge on DEA and enable the distribution of intelligence throughout a DEA device. In this paper we advance the capabilities of DES further to form volatile memory elements. A set reset flip-flop with inverted reset line was developed based on DES and DEA. With a 3200V supply the flip-flop behaved appropriately and demonstrated the creation of dielectric elastomer memory capable of changing state in response to 1 second long set and reset pulses. This memory opens up applications such as oscillator, de-bounce, timing, and sequential logic circuits; all of which could be distributed throughout biomimetic actuator arrays. Future work will include miniaturisation to improve response speed, implementation into more complex circuits, and investigation of longer lasting and more sensitive switching materials.

The focus of this paper is on the characterization of a balloon-shape actuator (BSA), based on dielectric electroactive polymers, which has a spherical shape, and it is pre-strained by pressurized air. Under electrical activation, the electrodes on the inner and outer surfaces of the BSA squeeze the elastomer in its radial thickness direction which results in a radial expansion of the BSA. This actuator has the potential to display large deformations under high compression loads. In this paper, a finite element model of the BSA is created by using ANSYS11 software. The mechanical behaviour of the BSA is studied, and the simulation results are presented. The mechanical properties of dielectric elastomers are experimentally measured and hyperelastic models used to fit the experimental data.

This research was conducted with the aim of developing an energy-efficient, noiseless, movable bionic eye for use in bionic toys. This novel bionic eye is actuated by an ionic polymer-metal composite actuator. The overall size of the eye was 39 mm in length, 45 mm in width, and 45 mm in thickness. The experimental results revealed such a bionic eye design is feasible. This type of bionic eye is appropriate for use in toys and robots to increase their visual impact.

This study presents the design and development of an underwater Jellyfish like robot using Ionic Polymer Metal Composites (IPMCs) as propulsion actuators. For this purpose, IPMCs are manufactured in several variations. First the electrode architecture is controlled to optimize the strain, strain rate, and stiffness of the actuator. Second, the incorporated diluents species are varied. The studied diluents are water, formamide, and 1-ethyl-3-methyimidazolium trifluoromethanesulfonate (EmI-Tf) ionic liquid. A water based IPMC demonstrates a fast strain rate of 1%/s, but small peak strain of 0.3%, and high current of 200mA/cm², as compared to an IL based IPMC which has a slow strain rate of 0.1%/s, large strain of 3%, and small current of 50mA/cm². The formamide is proved to be the most powerful with a strain rate of approximately 1%/s, peak strain larger than 5%, and a current of 150mA/cm². The IL and formamide based samples required encapsulation for shielding the diluents from being dissolved in the surrounding water. Two Jellyfish like robots are developed each with an actuator with different diluents. Several parameters on the robot are optimized, such as the input waveform to the actuators, the shape and material of the belly. The finesse ratio of the shape of the robotic belly is compared with biological jellyfish such as the Aurelia-Aurita..

Much attention has been given to ionic electroactive devices constructed using conducting polymers due to their low voltage requirements, high strain, and similarities to natural muscle. However, the time response and output force of conducting polymer actuators has always been a limiting factor in their implementation. In this study, we report on a processing technique and parametric optimization for multilayer polypyrrole-gold-polyvinylidene fluoride (PPy- Au-PVDF) composite actuators that have the possibility of overcoming the prior problems. These actuators are operable in air, have faster time response, and are projected to generate higher force compared to that of conventional conducting polymer actuators. These improvements are made possible due to the improvement in processing conditions and novel multilayer geometry of the actuators. A five layer PPy-Au-PVDF-Au-PPy actuator operating in air with 0.5M KCl electrolyte was shown to generate deflections up to 90% of the actuator length at a rate of 50% per second.

In this paper, we discuss a new form of electroactive material that consists of both synthetic polymers and biological molecules. This modular material system is inspired by the compartmentalized and hierarchical organization of cellular systems and features an artificial cell membrane, or lipid bilayer, which acts as the primary transduction element in the material. Building on recent developments by our group, the lipid bilayer is formed at the interface between phospholipid-encased hydrogel volumes surrounded by oil and contained in a solid substrate. Results are presented that demonstrate how the electromechanical properties of the lipid bilayer can be used for both static and dynamic sensing and actuation. Specifically, a relative change in length of the outer substrate of 10-15% due to an applied force yields large changes in capacitance (> 90% reduction) or resistance (20-30% increase) depending on the composition of the bilayer. The capacitive nature of the membrane is also used in a dynamic sensing application, whereby the perturbation of an artificial hair structure induces bending in a bilayer formed at the base of the hair. This oscillation results in a time-varying membrane capacitance that in turn produces an electrical current on the order of 1 - 100pA. The ability to actuate the amount of contact between neighboring modules is also discussed and a concept for fabricating higher-order biomolecular arrays that connect internally to form networks of lipid bilayers is also presented.

The lateral line system, consisting of arrays of neuromasts functioning as flow sensors, is an important sensory organ for fish that enables them to detect predators, locate preys, perform rheotaxis, and coordinate schooling. Creating artificial lateral line systems is of significant interest since it will provide a new sensing mechanism for control and coordination of underwater robots and vehicles. In this paper we propose recursive algorithms for localizing a vibrating sphere, also known as a dipole source, based on measurements from an array of flow sensors. A dipole source is frequently used in the study of biological lateral lines, as a surrogate for underwater motion sources such as a flapping fish fin. We first formulate a nonlinear estimation problem based on an analytical model for the dipole-generated flow field. Two algorithms are presented to estimate both the source location and the vibration amplitude, one based on the least squares method and the other based on the Newton-Raphson method. Simulation results show that both methods deliver comparable performance in source localization. A prototype of artificial lateral line system comprising four ionic polymer-metal composite (IPMC) sensors is built, and experimental results are further presented to demonstrate the effectiveness of IPMC lateral line systems and the proposed estimation algorithms.

Sensing and delivering tactile information is of interest not only in robotic researches but in most of broad sensor technology areas since along with olfactory it is one of the most difficult sensory information to detect and transfer. Most of the tactile sensors developed are using either brittle ceramic base material or bulky electromagnetic material. Although those tactile sensors provides some advantages like a certain level of accuracy in terms of the applied force measurement and reliable fabrication methods such as MEMS, there is still a significant drawback due to its brittle material characteristics. Especially for biomimetic applications the material flexibility might be the major concern in order to achieve the application objectives. In the present work, a multi-axis force sensor using polymeric material are developed. The sensor has ability to differentiate applied force directions such as normal and tangential and it to be deployed as an massive array so that a set of tactile sensors can be easily organized. Having the material flexibility, the present work successfully demonstrates a tactile sensor array affixed on a human-hand-like robot finger tip.

This paper presents a bio-inspired, dielectric elastomer (DE) based tubular pumping unit, developed for eventual use as a component of an artificial digestive tract onboard a microbial fuel cell powered robot (EcoBot). The pump effects fluid displacement by direct actuation of the tube wall as opposed to excitation by an external body. The actuator consists of a DE tube moulded from silicone, held in a negative pressure chamber, which is used for prestraining the tube. The pump is coupled with custom designed polymeric check valves in order to rectify the fluid flow and assess the performance of the unit. The valves exhibited the necessary low opening pressures required for use with the actuator. The tube's actuation characteristics were measured both with and without liquid in the system. Based on these data the optimal operating conditions for the pump are discussed. The pump and valve system has achieved flowrates in excess of 40μl/s. This radially contracting/expanding actuator element is the fundamental component of a peristaltic pump. This 'soft pump' concept is suitable for biomimetic robotic systems, or for the medical or food industries where hard contact with the delivered substrate may be undesirable. Future work will look at connecting multiple tubes in series in order to achieve peristalsis.

A new concept for a tube-like dielectric elastomer actuator (DEA) utilizes rigid micro-electrodes to stabilize the tube structure in azimuthal direction. The individual electrodes are stacked in axial direction within the tube wall. An axial arrangement of a number of those electrode stacks forms a single actuator filament. Application of electrical voltage induces mechanical tension into those stacks by the effect of Maxwell-stress. The interaction of individual electrodes causes a change of the total length of selected actuator filaments. A circular arrangement of a number of actuator filaments allows bending of the tube in any direction. The desired tube actuator is focused on thin walled structures with an outer diameter less than 6 mm and an available wall thickness of less than 0.4 mm. To supply individual electrode stacks with different electric potentials an efficient electrical circuit has to be integrated within the DEA structure. The challenges for the design and fabrication of this circuit primarily lie on the micro-electrode dimensions, the minimization of electrical resistances and severe requirements regarding low mechanical interference. As assumption the actuator electrodes are already stacked and each individual electrode must be accessible at the edge. Considering different surface manufacturing technologies an especially shaped conductor geometry should be deposited onto the electrode edges and the surrounding dielectric. The design of the interconnections considers electrical and mechanical requirements as well as the definition of applicable material parameters. The present work details different concepts for interconnecting rigid electrodes of a thin walled tube-like DEA and discusses related manufacturing technologies.

Ras Labs produces contractile electroactive polymer (EAP) based materials and actuators that bend, swell, ripple, and contract (new development) with low electric input. In addition, Ras Labs produces EAP materials that quickly contract and expand, repeatedly, by reversing the polarity of the electric input, which can be cycled. This phenomenon was explored using molecular modeling, followed by experimentation. Applied voltage step functions were also investigated. High voltage steps followed by low voltage steps produced a larger contraction followed by a smaller contraction. Actuator control by simply adjusting the electric input is extremely useful for biomimetic applications. Muscles are able to partially contract. If muscles could only completely contract, nobody could hold an egg, for example, without breaking it. A combination of high and low voltage step functions could produce gross motor function and fine manipulation within the same actuator unit. Plasma treated electrodes with various geometries were investigated as a means of providing for more durable actuation.

Binary Pneumatic Air Muscles (PAM) arranged in an elastically-averaged configuration can form a cost effective solution for Magnetic Resonance Imaging (MRI) guided robotic interventions like prostate cancer biopsies and brachytherapies. Such binary pneumatic manipulators require about 10 to 20 MRI-compatible valves to control the pressure state of each PAM. In this perspective, this paper presents the design of a novel dielectric elastomer actuator (DEA) driven jet-valve to control the states of the PAMs. DEAs are MRI compatible actuators that are well suited to the simplicity and cost-effectiveness of the binary manipulation approach. The key feature of the proposed valve design is its 2 stages configuration in which the pilot stage is moved with minimal mechanical friction by a rotary antagonistic DEA made with acrylic polymer films. The prismatic geometry also integrates the jet nozzle within the DEA volume to provide a compact embodiment with a reduced number of parts. The low actuation stretches enabled by the rotary configuration minimize viscoelastic losses, and thus, maximize the frequency response of the actuator while maximizing its reliability potential. The design space of the proposed jet valve is studied using an Ogden hyperelastic model and the valve dynamics is predicted with a 1D Bergstrom-Boyce viscoelastic model. Altogether, the low friction of the pilot stage and optimized DEA dynamics provide an experimental shifting time of the complete assembly in the 200-300ms range. Results from this work suggest that the DEA driven jet valve has great potential for switching a large number of pneumatic circuits in a MRI environment with a compact, low cost and simple embodiment.

With the rapid development of micro systems technology and microelectronics, smart electronic systems are emerging for the continuous surveillance of relevant parameters in the body and even for closed-loop systems with a sensor feedback to drug release systems. With respect to diabetes management, there is a critical societal need for a sensor that can be used to continuously measure a patient's blood glucose concentration twenty four hours a day on a long-term basis. In this work, thin films of "stimuli-responsive" or "smart" hydrogels were combined with microfabricated piezoresistive pressure transducers to obtain "chemomechanical sensors" that can serve as selective and versatile wireless biomedical sensors. The sensitivity of hydrogels with regard to the concentration of glucose in solutions with physiological pH, ionic strength and temperature was investigated in vitro. The response of the glucose-sensitive hydrogel was studied at different regimes of the glucose concentration change and at different temperatures. Sensor response time and accuracy with which a sensor can track gradual changes in glucose was estimated.

In 2003 Takuzo Aida and coworkers reported that single-walled carbon nanotubes (SW-CNTs), when ground with imidazolium based ionic liquids (ILs), create a physical gel, named "bucky gel"¹. This gel was used to prepare bimorph electrochemical actuators using a polymer-supported internal IL electrolyte layer². These actuators can operate in air at low voltage showing improved frequency response and strain. Usual bucky gel actuators rely on a bimorph configuration where the electrodes are used alternatively as cathode and anode thus producing a bending motion. This kind of motion is limiting the possible applications, especially when, like in artificial muscles, linear strain and motion are required. We present a new design for bucky gel actuators capable of both linear and bending motion that uses a three electrode configuration with two active electrodes and a third passive one, made from a metal spring (serpentine shaped), acting as counter plate. We have built such a device and report here its linear and bending actuation performance. In these preliminary experiments we have obtained a linear strain of 0.6% and a bending strain difference between two bucky gel electrodes of 0.25%.

This paper describes how to generate the vibration of IPMC effectively. First, it was found that IPMC generates large spiky deformation by applying long-term period saw-tooth wave voltage. The deformation quantity is increased with the longer period saw-tooth wave. Vibration with the proportional control was also investigated. IPMC cannot control its position by proportional control because of its frequent polarity change of the applied voltage. In this study, the proportional control is used for making vibration. However, the displacement induced by the proportional control is basically the same to the application of the AC rectangular pulse voltage if the frequency is equivalent to the equilibrium frequency of the proportional control. An automatic frequency tuning program was also made to vibrate IPMC effectively. The controller estimates the IPMC's vibration from the laser displacement sensor and changes the frequency of AC rectangular pulse voltage. The program tunes the frequency to maximize the average moving speed. The searching algorism is basically a hill climbing algorism. This program can tune IPMC's vibration frequency automatically if the surrounding circumstance is changed from water to air.

Electroactive polymers (EAP) are promising materials for actuators in different application areas. This paper reports inkjet printing as a versatile tool for manufacturing EAP actuators. Drop-on-demand inkjet printing can be used for additive deposition of functional materials onto substrates. Cantilever bending actuators with lateral dimensions in the mm range are described here. A commercially available solution of electroactive polymers is dispensed onto metalized polycarbonate substrates using inkjet printing. These polymers exhibit piezoelectric behavior. Multiple layers are printed resulting in a film thickness of 5 to 10 μm. After printing, the polymer layers are annealed thermally at 130 °C. Top electrodes are deposited onto the EAP layer by inkjet printing a silver nanoparticle ink. The as-printed silver layers are sintered using an argon plasma - a recently developed sintering technique that is compatible with low TG polymer foils. After printing the EAP layers are poled. When applying an electric field across the polymer layer, piezoelectric strain in the EAP leads to a bending deflection of the structures. With driving voltages of 200 V the actuators generate displacements of 20 μm and blocking forces of approximately 3 mN. The first resonance frequency occurs at 230 Hz.

Dielectric elastomer generators can be used as continuously controllable damping devices, by using e.g. a design with two single circular devices, clamped on the upside and downside of a rigid pipe and mechanically mounted in series with a piston inside the rigid pipe. In case of a mechanical excitation of the piston through the vibrating surface, one of the generators is stretched, while the other contracts and vice versa respectively. By using an appropriate concept for charging and discharging, the controllable damper can then be used for vibration isolation. These concepts are evaluated by simulation results with the two generator concept.

The impact of the modification of silicone rubber with barium titanate particles on the permittivity and hence on the performance of dielectric elastomer actuators has been investigated. Barium titanate powders with different particle sizes in the micrometer and nanometer range were used in this study. The mechanical properties of the composite materials in terms of the Young's modulus in tension and compression load as well as the viscoelastic behavior in shear load were experimentally determined. Additionally, the electric properties like permittivity, specific conductivity and electric breakdown field strength were evaluated. Model film actuators with the modified silicone material were prepared and their actuation strain was measured. With a concentration of 20 vol.% barium titanate particles, an enhancement of the permittivity of 140 % and an increase of the actuation strain of about 100 % with respect to the unmodified material could be achieved. Furthermore, first multilayer actuators were manufactured with an automatic spin coating process and their permittivity and strain were measured. The results of these investigations are in good agreement with the data of the experiments with single layer dielectric elastomer films.

This paper considers driving an Ionic Polymer-Metal Composite (IPMC) actuator using a Pulse Width Modulation (PWM) amplifier, in order to shed light on the characteristics of PWM driving of IPMCs. Generally, it is said that an efficiency of a PWM amplifier is higher than that of a linear amplifier. However, high current flows across the IPMC in the use of a PWM amplifier, and it is supposed to become the power consumption high. We solve this problem by putting an inductor between the PWM amplifier and the IPMC. The simulation and the experiment results demonstrate the effectiveness of the proposed method.

A promising application for dielectric elastomer actuators (DEA) is the active vibration control in the low frequency range (0 - 200 Hz). The active and passive properties of the actuator can be joined to eliminate the disturbances in the whole frequency range. These actuators can be used for protection of lightweight sensible equipment like optic e. g. components. This paper describes the dynamic modeling of dielectric elastomer actuators (DEA) and the design of control algorithms for applications like active suspensions. The used least mean squares parametric estimation method for dynamic modeling of DEA shows a good accordance with the real system. Moreover, the developed feedback controller improves the isolation characteristics of passive dielectric elastomer.

Today's Dielectric Electro Active Polymer (DEAP) actuators utilize high voltage (HV) in the range of kilo volts to fully stress the actuator. The requirement of HV is a drawback for the general use in the industry due to safety concerns and HV regulations. In order to avoid the HV interface to DEAP actuators, a low voltage solution is developed by integrating the driver electronic into a 110 mm tall cylindrical coreless Push InLastor actuator. To decrease the size of the driver, a piezoelectric transformer (PT) based solution is utilized. The PT is essentially an improved Rosen type PT with interleaved sections. Furthermore, the PT is optimized for an input voltage of 24 V with a gain high enough to achieve a DEAP voltage of 2.5 kV. The PT is simulated and verified through measurements on a working prototype. With the adapted hysteretic based control system; output voltage wave forms of both impulse response and sinusoidal shapes up to 2.5 kV are demonstrated. The control system, together with a carefully designed HV output stage, contributes to low power consumption at a static DEAP force. The HV stage consists of a HV measurement circuit and a triple diode voltage doubler optimized for low leakage current drawn from the DEAP. As a result, a 95 mm x 13 mm x 7 mm driver is integrated in a 110 mm x 32 mm actuator, forming a low voltage interfaced DEAP actuator.

Ionic electroactive polymer (i-EAP) actuators with large strain and low operation voltage are extremely attractive for applications such as MEMS and smart materials and systems. In-depth understanding of the ion transport and storage under electrical stimulus is crucial for optimizing the actuator performance. In this study, we show the dominances of ion diffusion charge and we perform direct measurements of the steady state ion distribution in charged and frozen actuators by using Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS). High temperature actuators that consist Aquivion ionomer membrane and high melting temperature ionic liquid 1-butyl-2,3-dimethylimidazolium chloride (BMMI-Cl]) served in this study. Electrical impedance, I-V characteristics, and potential step charging of the actuator are characterized at 25°C and 100°C. The conductivity of the actuator is 0.3mS/cm at 100°C and 2.9μS/cm at 25°C, respectively. The electrochemical window of the device is 3V and a 2mm tip displacement is observed under 2.5V 0.2Hz at 100°C. A semi-quantitative depth profile of the relative ion concentration in charged and frozen actuators is measured by ToF-SIMS. The result shows that, unlike semiconductors, ions do not deplete from the electrodes with same signs. Due to a strong cluster effect between the ions, Cl- and BMMI+ accumulate near both cathode and anode. Furthermore, the profile indicates that the ion size difference causes the BMMI+ space charge layers (~6um) much thicker than those of Cl- (~0.5um).

Due to technological advances in the optical information processing and optical communication fields, the demands for higher performance in spatial light modulator. The anti-ferroelectric liquid crystal (AFLC) has a possibility of achieving multi-tone control by applied voltage similar to nematic LCD. The AFLC was developed as a new spatial light modulator, and furthermore, a high-speed drive method with polarization properties was proposed. From this, a high-speed drive of 500 μsec was confirmed. In addition, basic studies were conducted on necessary functions required for phase modulators, and phase modulation due to the effect of voltage control was verified. From these results, the feasibility for a high-speed multi-level spatial light modulator with the effect of AFLC was verified.

Ionic polymer-metal composites (IPMCs) are an interesting subset of smart, multi-functional materials that have shown promises in energy conversion technologies. Being electromechanically coupled, IPMCs can function as dynamic actuators and sensors, transducers for energy conversion and harvesting, as well as artificial muscles for medical and industrial applications. Like all natural materials, even IPMCs undergo fatigue under dynamic load conditions. Here, we investigate the electromechanical fatigue induced in the IPMCs due to the application of cyclic mechanical bending deformation under hydrodynamic energy harvesting condition. Considering the viscoelastic nature of the IPMC, we employ an analytical approach to modeling electromechanical fatigue primarily under the cyclic stresses induced in the membrane. The polymer-metal composite undergoes cyclic softening throughout the fatigue life without attaining a saturated state of charge migration. However, it results in (1) degradation of electromechanical performance; (2) nucleation and growth of microscopic cracks in the metal electrodes; (3) delamination of metal electrodes at the polymer-electrode interface. To understand these processes, we employ a phenomenological approach based on experimentally measured relaxation properties of the IPMC membrane. Electromechanical performance improves significantly with self-healing like properties for a certain range of relaxation time. This is due to reorientation of the backbone polymer chains which eventually leads to a regenerative process with increased charge transport.

To reduce the likelihood of ventilator induced lung injury a neonatal lung simulator is developed based on Dielectric Elastomer Actuators (DEAs). DEAs are particularly suited for this application due to their natural like response as well as their self-sensing ability. By actively controlling the DEA, the pressure and volume inside the lung simulator can be controlled giving rise to active compliance control. Additionally the capacitance of the DEA can be used as a measurement of volume eliminating the integration errors that plague flow sensors. Based on simulations conducted with the FEA package ABAQUS and experimental data, the characteristics of the lung simulator were explored. A relationship between volume and capacitance was derived based on the self sensing of a bubble actuator. This was then used to calculate the compliance of the experimental bubble actuator. The current results are promising and show that mimicking a neonatal lung with DEAs may be possible.

Because of size and complexity concerns, implementing feedback control for ionic polymer-metal composite (IPMC) actuators is often difficult or costly in many of their envisioned biomedical and robotic applications. It is thus of interest to develop open-loop control strategies for these actuators. Such strategies, however, are susceptible to change of IPMC dynamics under varying environmental conditions, a predominant example being the temperature. In this paper we present a novel approach to open-loop control of IPMC actuators in the presence of ambient temperature changes. First, a method is proposed for modeling the temperature-dependent actuation dynamics. The empirical frequency response of an IPMC actuator, submerged in a water bath with controlled temperature, is obtained for a set of temperatures. For each temperature, a transfer function of a given structure is found to fit the measured data. A temperature-dependent transfer function model is then derived by curve-fitting each zero or pole as a simple polynomial function of the temperature. Open-loop control is then realized by inverting the model at a given temperature based on the auxiliary temperature measurement. However, the obtained model for IPMC actuators is of non-minimum phase and cannot be inverted directly. A stable but non-causal algorithm is adopted to implement the inversion. Furthermore, a finite-preview algorithm is proposed to enable near real-time tracking of desired outputs. Experimental results show that the proposed approach is effective in improving the tracking performance of IPMC actuators under varying temperatures.

The electrode of Ionic polymer-metal composites (IPMCs) is the key to understand their working mechanisms and mechano-electrical properties; however, there is little experimental report on the electrode morphologies and their forming mechanisms. In this paper, several typical IPMC samples with different electrode morphologies are fabricated by combining various process steps. The influence of the process steps, such as roughing treatment, immersing reduction and chemical plating, on the electrode surface and cross-section morphologies is investigated by SEM study, where the reaction principles are employed to explain that how the metal particles generate and grow at different directions of the electrode. The current and deformation responses of the samples are measured at the present of a voltage to characterize the mechano-electrical properties. Then it is concluded that immersing reduction is only suitable as a pre-deposition process step, and chemical plating is necessary for IPMC with desirable performance.

Commercial elastomer materials are available for dielectric electroactive polymer (DEAP) purposes but the applied commercial elastomers have not been developed with the specific application in mind. It is therefore obvious that optimization of the elastomer material should be possible. In this study we focus on optimization of the mechanical properties of the elastomer and show that it is possible to lower the elastic modulus and still not compromise the other required mechanical properties such as fast response, stability, low degree of viscous dissipation and high extensibility. The elastomers are prepared from a vinyl-terminated polydimethyl siloxane (PDMS) and a 4-functional crosslinker by a platinum-catalyzed hydrosilylation reaction between the two reactants. Traditionally, elastomers based on hydrosilylation are prepared via a 'one-step two-pot' procedure (with a mix A and a mix B mixed in a given ratio). An alternative network formulation method is adopted in this study in order to obtain an elastomeric system with controlled topology - a so-called bimodal network. Bimodal networks are synthesized using a 'two-step four-pot' mixing procedure which results in a nonhomogeneous network structure which is shown to lead to novel mechanical properties due to the low extensibility of the short chains and the high extensibility of the long chains. The first ensures stability and the last retards the rupture process thereby combining two desired properties for DEAP purposes without necessarily compromising the viscous dissipation. Several elastomers are prepared and tested for the linear viscoelastic behaviour, i.e. behaviour in the small-strain limit (up to approximately 10% strain). The bimodal networks are, however, capable of extensions up to several times their initial length but the focus here is the small-strain limit.

Chemical sensor technologies play an important role in development and improvement of public health and environment through applications in many areas. Conducting polymers are unique among the sensing materials known to us at present. They have many advantages over conventional metal sensors. Poly(p-phenylenevinylene) (PPV) can serve as the active material in sensor devices because PPV possesses good optical and electrical properties, and it can be synthesized by a relative simple technique. Zeolite is chosen to be introduced into a polymer matrix in order to increase sensitivity toward ammonium nitrate gas. This work will focus on the effect of Si/Al ratio and cation type on the electrical conductivity sensitivity towards the target gas.

Having a combination of a gel-like soft lens, ligaments, and the Ciliary muscles, the human eyes are effectively working for various focal lengths without a complicated group of lens. The simple and compact but effective optical system should deserve numerous attentions from various technical field especially portable information technology device industry. Noting the limited physical space of those deivces, demanding shock durability, and massive volume productivity, the present paper proposes a biomimetic optical lens unit that is organized with a circular silicone lens and an annular dielectric polymer actuator. Unlike the traditional optical lens mechanism that normally acquires a focus by changing its focal distance with moving lens or focal plane. the proposed optical system changes its lens thickness using a annulary connected polymer actuator in order to get image focuses. The proposed biomimetic lens system ensures high shock durability, compact physical dimensions, fast actuations, simple manufacturing process, and low production cost.

Conductive grease and powder are commonly applied as compliant electrodes for dielectric elastomer actuators (DEAs). Unfortunately, they can be rubbed off easily and DEAs based on them cannot self-heal from localised electrical breakdowns. Metallic thin films are cleaner and more resilient alternatives for electrodes. They are currently widely used in metalized plastic capacitors, which are known for their self-healing capability. However, they are not widely used in DEAs due to limitations in strain. In this paper, we demonstrate that a metalized DEA is capable of areal strains of up to 21%. The inexpensive and simple method of electroless silver deposition had been used to create the electrodes for the single-layer DEA. The lightly pre-stretched 80μm thick dielectric film demonstrated a 21% areal strain, which is a 17% reduction in thickness, with an applied voltage of 2.5kV. Self-healing properties of the silver electrodes have also been observed. Localised breakdowns of the dielectric film self-healed, thereby averting electrical breakdown and allowing actuation to continue, even at higher applied voltages. With higher breakdown voltages, larger breakdown fields were obtained, which would in turn lead to greater electrostatic forces. Relatively high breakdown fields of up to 75 MV/m were obtained. This is in contrast to the 35 MV/m obtained by silver grease under the same conditions. In mechanical strain tests, the silver films remained conductive while subjected to a uni-axial mechanical strain of up to 50%, which ascertains the ability of such electrodes to sustain high strains.

The manta ray, Manta birostris, demonstrates excellent swimming capabilities; generating highly efficient thrust via flapping of dorsally flattened pectoral fins. In this paper, we present an underwater robot that mimics the swimming behavior of the manta ray. An assembly-based fabrication method is developed to create the artificial pectoral fins, which are capable of generating oscillatory with a large twisting angle between leading and trailing edges. Ionic polymer-metal composite (IPMC) actuators are used as artificial muscles in the fin. Each fin consists of four IPMC beams bonded with a compliant poly(dimethylsiloxane) (PDMS) membrane. By controlling each individual IPMC strips, we are able to generate complex flapping motions. The fin is characterized in terms of tip deflection, tip blocking force, twist angle, and power consumption. Based on the characteristics of the artificial pectoral fin, a small size and free-swimming robotic manta ray is developed. The robot consists of two artificial pectoral fins, a rigid body, and an on-board control unit with a lithium ion rechargeable battery. Experimental results show that the robot swam at a speed of up to 0.055 body length per second (BL/sec).

This paper presents an experimental investigation of three different, small profile and scalable DEAP actuators. These actuators are designed for use in small scale pumping and valve applications. The actuators used in this paper consist of a biasing element (either a mass, linear spring, or a non-linear spring) coupled with a circular dielectric electro-active polymer (DEAP). These mechanisms bias the DEAP allowing out-of-plane actuation when the voltage is cycled. A constant force input, a linear spring, and a non-linear spring are separately tested as the biasing element of a circular/diaphragm DEAP. Tests are systematically performed at various DEAP pre-deflections, biasing stiffness and electrical loading rates. The displacement stroke performance of each test is examined and analyzed. It was found that the non-linear spring provided the largest displacement stroke over two other biasing elements. It also showed better performance at higher electrical loading rates. Thus, of the three types of biasing tested the non-linear spring shows most promise for use in fluid pump/valve applications. Future work will include optimizing this biasing element for the current DEAP design.

Human health and energy problems associated with the lack of control of sunlight in contemporary buildings have necessitated research into dynamic windows for energy efficient buildings. Existing window technologies have made moderate progress towards greater energy performance for facades but remain limited in their response to dynamic solar conditions, building energy requirements, and variable user preferences for visual comfort. Recent developments in electropolymeric display technology provide opportunities to transfer electroactive polymers to windows that can achieve high levels of geometric and spectral selectivity through the building envelope in order to meet the lighting, thermal and user requirements of occupied spaces. Experimental simulations that investigate daylight quality, energy performance, and architectural effects of electropolymeric glazing technology are presented.

A number of adaptive structure applications call for the generation of intense electric fields (in excess of 70 MV/m). Such intense fields across the thickness of a thin polymer dielectric layer are typically used to exploit the direct electromechanical coupling in the form of a Maxwell stress: (see manuscript) Where V/d is the applied field, ε0 is the permittivity of vacuum and ε is the relative permittivity of the material. The field that can be applied to the dielectric is limited by the dielectric strength of the material. Below the limit set by the breakdown, the material is generally assumed to have a field independent dielectric constant and to be a perfect insulator, i.e. to have an infinite volume resistivity. While extensive investigations about the mechanical properties of the materials used for electronic Dielectric Elastomer Actuators (DEA) are available from literature, the results of the investigation of the insulating and dielectric properties of these materials, especially under conditions (electric field and frequency) similar to the ones encountered during operation are not available. In the present contribution, we present a method and a set-up for the measurement of the electric properties of thin polymer films, such as the ones used for the fabrication of electronic DEAs, under conditions close to operations. The method and setup where developed to investigate the properties of 'stiff' thin polymer films, such as Polyimide or Polyvinylidenefluoride, used for Electro-Bonded Laminates (EBLs). The properties of the well known VHB 4910 acrylic elastomer are presented to illustrate how the permittivity and the leakage current can be measured as a function of the electric field and the deformation state, using the proposed set-up. The material properties were measured on membranes under different fixed pre-stretch conditions (λ 1, λ2=3, 4, 5), in order to eliminate effects due to the change in sample geometry, using gold sputtered electrodes, 20nm thick. The values obtained for the permittivity of the material are in good agreement with the work of other authors. The dissipative properties revealed by the measurements performed at high fields, similar to the ones encountered in operation, indicate that this less investigated aspect of VHB needs to be taken in consideration for real world applications.