Human-like robots, which have been a science fiction for many years, are increasingly becoming an engineering reality thanks to many technology advances in recent years. Humans have always sought to imitate the human appearance, functions and intelligence and as the capability progresses they may become our household appliance or even companion. Biomimetic technologies are increasingly becoming common tools to support the development of such robots. As artificial muscles, electroactive polymers (EAP) are offering important actuation capability for making such machines lifelike. The current limitations of EAP are hampering the possibilities that can be adapted in such robots but progress is continually being made. As opposed to other human made machines and devices, this technology raises various questions and concerns that need to be addressed. These include the need to prevent accidents, deliberate harm, or their use in crimes. In this paper the state-of-the-art and the challenges will be reviewed.

Designing components using SmartMOVE^TM electroactive polymer technology requires an understanding of the basic operation principles and the necessary design tools for integration into actuator, sensor and energy generation applications. Artificial Muscle, Inc. is collaborating with OEMs to develop customized solutions for their applications using smartMOVE. SmartMOVE is an advanced and elegant way to obtain almost any kind of movement using dielectric elastomer electroactive polymers. Integration of this technology offers the unique capability to create highly precise and customized motion for devices and systems that require actuation. Applications of SmartMOVE include linear actuators for medical, consumer and industrial applications, such as pumps, valves, optical or haptic devices. This paper will present design guidelines for selecting a smartMOVE actuator design to match the stroke, force, power, size, speed, environmental and reliability requirements for a range of applications. Power supply and controller design and selection will also be introduced. An overview of some of the most versatile configuration options will be presented with performance comparisons. A case example will include the selection, optimization, and performance overview of a smartMOVE actuator for the cell phone camera auto-focus and proportional valve applications.

The significant electromechanical performances typically shown by dielectric elastomer actuators make this polymer technology particularly attractive for possible active orthoses for rehabilitation. Folded contractile actuators made of dielectric elastomers were recently described as a simple configuration, suitable to easily implement linear contractile devices. This paper describes an application of folded actuators for so-called hand splints: they consist of orthotic systems for hand rehabilitation. The dynamic versions of the state-of-the-art splints typically include elastic bands, which exert a passive elastic resistance to voluntary elongations of one or more fingers. In order to provide such splints with the possibility of electrically modulating the compliance of the resistive elements, the substitution of the passive elastic bands with the contractile actuators is here described. The electrical activation of the actuators is used to vary the compliance of the system; this enables modulations of the force that acts as an antagonist to voluntary finger movements, according to programmable rehabilitation exercises. The paper reports results obtained from the first prototype implementations of such a type of system.

The need for high driving electric fields currently limits the diffusion of dielectric elastomer actuation in some areas of potential application, especially in the case of biomedical disciplines. A reduction of the driving fields may be achieved with new elastomers offering intrinsically superior electromechanical properties. So far, most of attempts in this direction have been focused on composites between elastomer matrixes and high-permittivity ceramic fillers, yielding to limited results. In this work, the electromechanical response of a silicone rubber (poly-dimethyl-siloxane) was improved by blending, rather than loading, the elastomer with a highly polarizable conjugated polymer (undoped poly-hexyl-thiophene). Very low percentages (1-6 wt%) of poly-hexyl-thiophene yielded both an increase of the dielectric permittivity and an unexpected reduction of the tensile elastic modulus. Both these factors contributed to a remarkable increase of the electromechanical response, which reached a maximum at 1 wt% content of conjugated polymer. This approach may lead to the development of new types of improved dielectric elastomers for actuation.

Carbon nanotubes (CNTs) have attracted extensive attention in the past few years because of their appealing mechanical and electronic properties. Yarns made through spinning multi-walled carbon nanotubes (MWNTs) have been reported. Here we report the application of these yarns as electrochemical actuators, force sensors and microwires. When extra charge is stored in the yarns, change in length. This actuation is thought to be because of electrostatic as well as quantum chemical effects in the nanotube backbones. We report strains up to 0.7 %. At the same time, the charged yarns can respond to a change in the applied tension by generating a current or a potential difference that is related to the applied tension force. As current carriers, the yarns offer a conductivity of ~300 S/cm, which increases linearly with temperature. We report a current capacity of more than 10⁸ A/m², which is comparable to those of macroscopic metal wires. However, these nanotube yarns have a density (0.8 g/cm³) that is an order of magnitude lower than metallic wires. The MWNT yarns are mechanically strong with tensile strengths reaching 700 MPa. These properties together make them a candidate material for use in many applications including sensors, actuators and light-weight current carriers.

In this paper the behavior of conjugated polymers as mechanical sensors is experimentally characterized and modeled. A trilayer conjugated polymer sensor is considered, where two polypyrrole (PPy) layers sandwich an amorphous polyvinylidene fluoride (PVDF) layer, with the latter serving as an electrolyte tank. A theory for the sensing mechanism is proposed by postulating that, through its influence on the pore structure, mechanical deformation correlates directly to the concentration of ions at the PPy/PVDF interface. This provides a key boundary condition for the partial differential equation (PDE) governing the ion diffusion and migration dynamics. By ignoring the migration term in the PDE, an analytical model is obtained in the form of a transfer function that relates the open-circuit sensing voltage to the mechanical input. The model is validated in experiments using dynamic mechanical stimuli up to 50 Hz.

In this paper we are reporting a newely developed IPMC fabrication method, "IPMC Paint", which can be directly sprayed onto any complex surface. In order to fabricate the IPMC paint, liquid Nafion^TM was used for the ionic conducting polymer instead of the typical film/sheet type Nafion^TM. The viscosity of liquid Nafion^TM was adjusted by adding Polyvinylpyrrolidone (PVP) to perform spray painting. Modified Nafion was sprayed onto the conducting substrate, Polyfoil^TM which acts as base electrode layer. After three times spraying, ionic polymer layer has 45 μm thickness and 10 μm of surface roughness. Sensing tests show that IPMC paint sensor has more sensitivity (± 0.06 of producing voltage) than that of the typical IPMC (± 0.005 of producing voltage) when dynamic bending with 10 Hz frequency and 1.3 cm of displacement is applied to.

A new fabrication system for Ionic Polymer Metallic Composites (IPMC) entitled Micro Deposition Method(MDM) is introduced. The tolerances in prototyping IPMC's using available fabrication techniques does not meet the tight limits for fabricating the polymer transducer. The MDM overcomes this limitation by using a microfluidic dispersion head that can deposit 3 to 10 picoliters of the electrode layer dissolved in a solvent at a high throughput. The MDM in its existing configuration can be used to fabricate micron scale polymer transducers with features 2 microns and above with high accuracy and repeatability. A commercially available piezoelectric deposition head from an inkjet printer is modified and used to disperse the electrode material of controlled thickness as a concept demonstration. The physical properties of the dispersed fluid are adjusted to meet the requirements of the deposition head to fabricate the prototype. The dispersion fluid used had a viscosity of 3.47 ±0.06 cP, a surface tension of 23.6 ±.1 mNm^-1, and a conducting power volume load set at 10%.

The characteristics of Ionic polymer metal-composites, containing bimetallic Pt-Pd electrodes which had been prepared by an electroless chemical reduction method on a polymer membrane, were investigated. Bimetallic Pt-Pd electrodes with various compositions (Pt:Pd weight ratios) were compared with those of monometallic Pt and Pd electrodes that had been prepared under similar conditions. The surface compositions of the Pt and Pd on the electrodes were compared using an energy dispersive X-ray spectroscopy (EDS). The crystal structures of the electrodes were investigated by an X-ray diffraction (XRD); surface morphologies were also compared by scanning electron microscopy (SEM) which depends on the palladium amounts. The optimal composition of the Pt and Pd affects not only surface morphology, but also the improvement of the actuation and associated relaxation phenomena of IPMCs.

Nafion is widely known as one of the most popular membrane materials for low temperature fuel cell applications. However, the particular exchange membrane material properties make it also valuable for other applications. One of the electroactive polymer (EAP) subclasses, ionic polymer metal composites (IPMC) commonly exploits Nafion as the ion exchange polymer membrane. The ion conducting properties of Nafion are extremely important for IPMCs. Although, ion conductivity depends strongly on the structural properties of the polymer matrix, there has been very little insight at the atomistic level. Molecular dynamics simulations are one of the possibilities to study the ion conduction mechanism at atomistic level. So far, the simulation results have been rather contradictory and very much dependent from the force fields and polymer matrix setup used. In the present work, new force field parameters for Li⁺ and Na⁺ - nafion based on DFT calculations are presented. The developed potentials and the force field were tested by molecular dynamics simulations. It can be concluded that Li⁺ and Na⁺ ions are coordinated to different Nafion side-chain terminal group (SO₃^-) oxygens and to very few water molecules. One cation is coordinated to three different side-chains. Oxygens of SO₃ groups and cations form complicated multi-header systems. In the equilibrium state, no cations dissociated from side chains were found.

Ionic-polymer metal composites are innovative materials that offer combined sensing and actuating ability in lightweight and flexible package. As such, they have been exploited in robotics and a wide variety of biomedical devices, for example, as fins for propelling aquatic robots and as an injector for drug delivery. One of the main challenges of IPMC-based actuators is precision control of their movements, especially at high operating speed (frequency) because of dynamic effects. As the frequency increases, the dynamics cause vibration which leads to significant tracking error. A model-based feedforward controller is applied to control the position of a custom-made Nafion-based IPMC actuator. The feedforward controller was designed to account for the linear dynamics, and the feedforward input was computed by considering the magnitude of the input signal and the tracking precision. To account for unmodeled effects not captured by the linear model, a feedback controller was integrated with the feedforward controller. The feedback controller provides robustness. Experimental results show a significant improvement in the tracking performance using feedforward control. In particular, the feedforward controller resulted in over 75% improvement in the tracking error compared to the case without dynamic compensation. Then by adding a proportional-integral feedback controller, the tracking error was less than 10% at 18 Hz scan frequency.

This paper presents a distributed model of an IPMC (Ionomeric Polymer-Metal Composite). Unlike other electromechanical models of an IPMC, the distributed nature of our model permits modelling the non-uniform bending of the material. Instead of modeling solely the tip deflection of the material, we model the changing curvature. Our model of the IPMC describes the actuator or sensor as a distributed one-dimensional RC transmission line. The behavior of the IPMC at its each particular position in time-domain is described by a system of Partial Differential Equations. (PDE). The parameters of the PDE-s have a clear physical interpretation: the conductivity of the electrodes, the pseudocapacitance of the arising double-layer at the boundary of the electrodes, the electric current caused by electrode reactions etc. The electromechanical coupling between the electrical parameters and the bending motion is implemented by means of distribution of electric current along the material in a time domain. The distributed nature of the model permits predicting the non-uniform bending of the IPMC actuators in time domain or to reconcile the output of an IPMC-based position sensor with its shape. Taking into account several nonlinear parameters, the model is consistent with the experimental results even when the inflexion of the actuator or sensor is large or the water electrolysis appears.

Although the Ionic Polymer-Metal Composite (IPMC) actuators developed up to date are in the form of bending actuators, development of extensional actuators based on IMPC is highly desirable from practical applications and fundamental understanding points of view. This talk presents the design, fabrication and characterization of a recent work on an extensional Ionic Polymer-Metal Composite actuator. The extensional actuator consists of the Nafion ionomer as the matrix and the sub-micron size RuO₂ particles as the conductive filler for the conductor/ionomr composites. In this investigation, several ionic liquids (IL) were investigated. For a Nafion/RuO₂ composite with 1-Ethyl-3-methylimidazolium trifluoromethanesulfonate (EMI-Tf) IL, it was found that as the ions are driven into the ionomer/RuO₂ composite (the composite under negative voltage), an extensional strain of 0.9% was observed; while as the ions were expelled from the ionomer/RuO₂ composite (under positive voltage), a contraction of -1.2% was observed. The results indicate that multiple ions are participating in charge transport and actuation process. In this paper, we also discuss several design considerations for future extensional actuators with fast response, much improved strain and stress level. Especially an actuator based on multilayer configuration can significantly increase the electric field level in the actuator and consequently significantly improve the actuator speed. The extensional actuator investigated here provides a unique platform to investigate various phenomena related to ion transport and their interaction with the ionomer/conductor matrix to realize high electromechanical performance.

Ionic polymer-metal composites (IPMCs) have built-in sensing and actuation capabilities which make them attractive in many biomedical and biological applications. In this paper a physics-based but control-oriented dynamic model is proposed for IPMC actuators. The modeling work starts from the governing partial differential equation (PDE) that describes the charge redistribution dynamics under external electrical field, electrostatic interactions, ionic diffusion, and ionic migration along the thickness direction. It is further extended by incorporating the effect of distributed surface resistance. The electrical impedance model is obtained by deriving the exact solution to the governing PDE in the Laplace domain. By assuming a linear electromechanical coupling, an actuation model which relates bending displacement to voltage input is derived. The model is represented as an infinite-dimensional transfer function, which is amenable to model reduction and real-time control design while capturing fundamental physics. It thus bridges the traditional gap between the physics-based perspective and the system-theoretic perspective on modeling of IPMC materials. The model is expressed in terms of fundamental material parameters and dimensions of the IPMC, and is therefore geometrically scalable. The latter has been further confirmed in experiments.

Ionic polymer transducers (IPT), sometimes referred to as artificial muscles, are known to generate a large bending strain and a moderate stress at low applied voltages (<5V). Bending actuators have limited engineering applications due to the low forcing capabilities and the need for complicated external devices to convert the bending action into rotating or linear motion desired in most devices. Recently Akle and Leo reported extensional actuation in ionic polymer transducers. In this study, extensional IPTs are characterized as a function of transducer architecture. In this study 2 actuators are built and there extensional displacement response is characterized. The transducers have similar electrodes while the middle membrane in the first is a Nafion / ionic liquid and an aluminum oxide - ionic liquid in the second. The first transducer is characterized for constant current input, voltage step input, and sweep voltage input. The model prediction is in agreement in both shape and magnitude for the constant current experiment. The values of α and β used are within the range of values reported in Akle and Leo. Both experiments and model demonstrate that there is a preferred direction of applying the potential so that the transducer will exhibit large deformations. In step response the model well predicted the negative potential and the early part of the step in the positive potential and failed to predict the displacement after approximately 180s has elapsed. The model well predicted the sweep response, and the observed 1st harmonic in the displacement further confirmed the existence of a quadratic in the charge response. Finally the aluminum oxide based transducer is characterized for a step response and compared to the Nafion based transducer. The second actuator demonstrated electromechanical extensional response faster than that in the Nafion based transducer. The Aluminum oxide based transducer is expected to provide larger forces and hence larger energy density.

The emergence of soft polymer actuators brings a great deal of excitement in the robotics and biomedical engineering community because of the possibilities to easily mimic the motion of living organisms and ability to manipulate living tissue and cells without damaging it. Some of the applications of soft polymer actuators, such as micropumps, require them to operate at high frequency and large displacement, which usually achieved near resonance. It would be beneficial for the designer, if he could easily tailor the frequency response and the resonance frequency to suit the operating conditions. We propose such an effective method of modification of the frequency response of ionic polymer metal composite (IPMC) actuators by introducing an anisotropic roughness on their surface.

"Effective" electromechanical coupling coefficient for IPMC by equivalent bimorph beam model is studied. The collective effect of the membrane thickness and operating voltage is demonstrated by using a design of experiment of three and four levels of the two factors, respectively. Experiments and finite element analyses using MSC.NASTRAN are used to evaluate the tip displacement and the coupling coefficient for which approximations as function of the thickness and voltage are constructed. Initial curvature of the strips before electrical excitation is also shown to be a factor in "effective" coupling coefficient. A correction factor approach is proposed to include the effect of the preimposed curvature.

The paper provides a summary review of the accomplishments and challenges in the field of electroactive polymers (EAP). It consists of three parts. The first part outlines the main classes of EAP, their properties and applications. Efforts to enhance the functional performance of EAP are discussed. The second part summarizes the development and use of electroactive polymer based composites. Challenges, opportunities and future research directions in the field are discussed in the third part. The issues of particular interest concern accurate material characterization of electroactive polymers, their time dependent behavior, constitutive modeling, and cyclic loading effects that determine the long-term functionality, integrity and durability of electroactive polymers. Research efforts in these focus areas are necessary to ensure effective integration of EAP in multifunctional material systems.

Polyaniline nanofibers (Pani nanofibers) have exhibited high performance and fault tolerant properties for dielectric elastomer actuator devices. Electrodes comprised of uniformly sprayed Pani nanofibers in thicknesses 0.7 μm, 1.1 μm, 1.3 μm, and 1.5 μm have shown the following high strains: 65% in area for 0.7 μm electrodes at 3 kV, 97% in area for 1.1 μm thick electrodes at 3.5 kV, 84% in area for 1.1 μm thick electrodes at 3 kV, and 114.% in area for 1.5 μm thick electrodes at 3.5 kV. Optimal performance was achieved with actuators with electrodes 1.1 μm thick, which demonstrated self-healing properties at 3 kV. These actuators displayed a preserved strain of 91% after the clearing and sustained a 93% area strain for 10 minutes at 3 kV. Devices with 1.1 μm thick electrodes were also able to perform 700 actuation cycles over a total duration of 75 minutes with a pulsed half-sinusoidal voltage of 3 kV. Mechanical compliance tests performed on a film with a 1.1 μm thick Pani nanofiber electrode reveals that the electrode material does not significantly alter the mechanical properties of the film. The estimated Young's modulus was found to be 32 MPa for the film with the electrode and 31 MPa for the film itself.

Dielectric elastomer actuators which consist of an electrode/dielectric elastomer/electrode sandwich structure show greater than 100% electromechanical strain performance when high electrical field is applied. The strain in the dielectric elastomer film occurs due to attraction of opposite charges across the dielectric film and repulsion of similar charges on each compliant electrode. Structural defects present in these elastomers such as gel particles, uneven thickness, and stress concentration may cause dielectric breakdown, leading to premature failure during continuous or repeated actuations. Dielectric breakdown consequently reduces production yield and device lifetime. Carbon nanotubes (CNTs) have been introduced as compliant electrodes for dielectric elastomers. Higher than 100% electromechanical strain was obtained with ultrathin CNT electrodes due to the high aspect ratio and the high electrical conductivity of the nanotubes. These ultrathin CNT electrodes also exhibit fault-tolerance in dielectric elastomers through the local degradation of CNTs during dielectric breakdown. The degraded areas electrically isolate the defects, while keeping the rest of the elastomer active. The "self-clearing" electrodes significantly increase the lifetime of the dielectric elastomers, making the dielectric elasomer actuator much more reliable.

Thin polymer foams with a closed cell void-structure can be internally charged by silent or partial discharges within the voids. The resulting material, which carries positive and negative charges on the internal void surfaces is called a ferroelectret. Ferroelectrets behave like typical ferroelectrics, hence they provide a novel class of ferroic materials. The soft foams are strongly piezoelectric in the 3-direction, but show negligible piezoelectric response in the transverse direction. This, together with a very low pyroelectric coefficient, make ferroelectrets highly suitable for flexible electroactive transducer element which can be integrated in thin bendable organic electronic devices. Here we describe some fundamental characteristics of cellular ferroelectrets and present a number of promising examples for a possible combination with various functional polymer systems. Our examples focus on flexible ferroelectret field-effect transistor systems for large-area sensor skins and microphones, flexible large-array position detectors (touchpad), and stretchable large-array pressure sensors.

Dielectric electroactive polymer membranes have been shown to have capabilities both as actuators and generators. Recent models of actuators have shown input to output dynamics that link the electrical energy input to the acceleration of a mass. Models such as these are useful for implementing closed loop control systems and will be necessary in the future for the construction of robust and fault tolerant controls. On the other hand, explanations of the generator behavior of dielectric EAP devices tend to ignore full dynamics. In this paper it is demonstrated that an EAP actuator model with full electrical-mechanical dynamics can be used as a generator model with the generator input force equivalent to the actuator disturbance force. Since the generator and actuator models are equivalent, it can be shown how disturbance inputs can cause energy surges back toward the electrical input. Simulations and experimental results are provided of a device model that describes generation and actuation.

After having successfully integrated Dielectric Elastomers (DE) in a cross tail for flight control, a novel biologically inspired propulsion system based on DE is envisaged. The basic idea is to mimic a fish body motion by deforming a) the envelope of the rear lifting body and b) flapping an aft-tail. In both cases, planar DEs are used, either fully integrated in the envelope (for a) and/or arranged as an active hinge (for b). In a theoretical study the specifications of a steady-state horizontal indoor flight of 1 m/s were defined. In an experimental work the concept of an active hull element, which consists of a balloon hull material and several layers of DE actuators was verified. The specific boundary conditions of a slightly pressurized elliptical membrane body were simulated in a biaxial test. It could be shown, that the necessary active strains to reach the specified body deformations were reached. In a second study an aero-elastic fin was designed. Based on fluid-dynamic similarity principles the size, shape and stiffness of the fin were determined and tested in preliminary flight test with a three meter long blimp. The main goal of 1 m/s flight velocity could be shown.

This paper presents an experimentally validated, nonlinear finite element model capable of predicting the blocked force produced by Dielectric Elastomer Minimum Energy Structure (DEMES) bending actuators. DEMES consist of pre-stretched dielectric elastomer (DE) films bonded to thin frames, the complex collapse of which can produce useful bending actuation. Key advantages of DEMES include the ability to be fabricated in-plane, and the elimination of bulky pre-stretch supports which are often found in other DE devices. Triangular DEMES with 3 different pre-stretch ratios were fabricated. Six DEMES at each stretch ratio combination were built to quantify experimental scatter which was significant due to the highly sensitive nature of the erect DEMES equilibrium point. The best actuators produced approximately 10mN blocked force at 2500V. We integrate an Arruda-Boyce model incorporating viscoelastic effects with the Proney series to describe the stress-strain response of the elastomer, and a Neo-Hookean model to describe the frame. Maxwell pressure was simulated using a constant thickness approximation and an isotropic membrane permittivity was calculated for the stress state of the DEMES membrane. Experimental data was compared with the model and gave reasonable correlation. The model tended to underestimate the blocked force due to a constant thickness assumption during the application of Maxwell stress. The spread due to dielectric constant variance is also presented and compared with the spread of experimental scatter in the results.

In this paper we present a dielectric elastomer actuator, which has the ability to sense the force acting on it without any additional sensing device. Basic physical behaviors of the dielectric elastomer are experimentally investigated and it is noted that the impedance of the dielectric elastomer varies depending on external forces acting on it. Based on that concept, we propose the principle of a self-sensing actuator according to experimental result. In addition, a multi-stacked actuator with self-sensing capability is realized to validate its feasibility.

This article presents metal ion implantation as an alternative technique to fabricate compliant electrodes for small-size dielectric elastomer actuators. When reducing the size of these actuators to below 1 cm, the ability to pattern the electrodes is added to the need for compliance. Metal ion implantation on Polydimethylsiloxane (PDMS) layers allows the creation of conductive and compliant electrodes, which can be easily defined by photolithography or with a shadow mask. Mechanical testing show that implantation has a limited impact on the PDMS' properties, with a Young's modulus increase of 50%-200% depending on the dose. Uniaxial stretching tests show that conductivity is conserved for strains up to 50% and present no hysteresis. Dielectric breakdown tests were conducted for Au and Pd implantations, which exhibited high breakdown fields (> 100V/μm), similar to non-implanted PDMS layers. Other advantages of ion implanted electrodes include transparency and a negligible mass. Buckling mode diaphragm actuators were fabricated with ion-implanted electrodes and exhibited out-of-plane displacements up to 7% of their lateral dimensions.

The rolled actuator represents a design where the pre-stretched EAP film is wrapped many times around a spring core in order to form a multilayer actuator system with unidirectional actuation. The freestanding rolled configuration enables the use of the DE film for muscle like linear actuators with a broad application potential. The stress state of the pre-strained acrylic film in the rolled configuration and the required stiff core can cause several serious problems concerning lifetime, size and efficiency of the actuator. In order to obtain an acceptable specific actuator performance and lifetime the pre-stretching stress has to be essentially reduced or even eliminated. This can be achieved by the interpenetrating polymer network (IPN) process newly developed at the UCLA. Thereby a trifunctional methacrylate monomers is introduced into the highly pre-strained acrylic films and subsequently curing the monomers to form an interpenetrating elastomeric network. The as obtained interpenetrating polymer network (IPN) can effectively support the pre-strain of the acrylic film and consequently eliminate the need for external pre-strain-supporting structures. In this study a new rolled actuator design is presented based on the IPN post treated VHB material. Due to the stress free state of the wrapped film no spring core is necessary. As a result a significantly longer lifetime and better specific volume efficiency of the actuator has been achieved at lower unidirectional elongation when activated. Introductorily, the specific problems on conventional rolled actuators are discussed and the aims for core free rolled actuators are specified. Then some structural design parameters are addressed in order to achieve a slight shape and reliable working principle. In the main part of the study the manufacturing process of the actuators and some measurement results and experiences are discussed in detail.

Polyelectrolyte gels are ductile elastic electroactive materials. They consist of a polymer network with charged groups and a liquid phase with mobile ions. Changing the chemical or electric conditions in the gel-surrounding solution leads to a change of the chemo-electro-mechanical state in the gel phase: diffusion and migration of ions and solvent between the gel and solution phases trigger the swelling or shrinkage of the polymer gel. In case of chemical stimulation (change of pH or salt concentration), a swelling ratio of up to 100% may be obtained. Due to this large swelling ratio the gels exhibit excellent actuatoric capabilities. In this paper, a polyelectrolyte gel placed in a solution bath is investigated. The actuatoric and sensoric capabilities are described by a chemo-electro-mechanical model. The chemical field is represented by a convection-migration-diffusion equation while the electric field is described by a quasi-static Laplace equation. For the mechanical field a partial differential equation of first order in time is applied. Inertia effects are neglected due to the relatively slow swelling/shrinkage process. On the one hand, the coupling between the chemo-electrical and the mechanical field is realised by the differential osmotic pressure stemming from the concentration differences between gel and solution. On the other hand, the mechanical deformation influences the concentration of the bound charged groups in the gel. The three fields are solved simultaneously by applying the Newton Raphson method using finite elements in space and finite differences in time. The developed model is applicable for both, hydrogel actuators and sensors. Numerical results of swelling and bending are given for chemically and electrically stimulated polymer gels. In this paper we show the differences between the chemo-electric and the fully coupled chemo-electro-mechanical formulation for polymer gels in different solution baths. The inverse (sensor-) effect is demonstrated by the influence of the mechanical deformation on the gel, which results in a change of the chemical and electrical unknowns in the gel. The validity of the employed numerical model is shown by a comparison of the obtained results with experimental measurements.

The reduction-oxidation (redox) level of a conjugated polymer has significant impact on its electro-chemo-mechanical properties, such as conductivity, impedance, and Young's modulus. A redox level-dependent impedance model is developed in this paper by including the dynamics of ion diffusion, ion migration, and redox reactions. The model, in the form of a transfer function, is derived through perturbation analysis around a given redox level. Experimental measurements conducted under different redox conditions correlate well with the model prediction and thus validate the proposed model. This work, for the first time, incorporates the effect of redox level into the dynamics of conjugated polymers, and facilitates the future use of nonlinear control methods for the effective control of these materials.

Soft active materials have many important applications. We develop a theory of large deformation in a family of soft active materials known as dielectric elastomers. We show that the Maxwell stress is not applicable to deformable dielectrics in general, and that the effect of electric field on deformation is material specific. Based on available experimental data, we construct for a class of model materials, which we call ideal dielectric elastomers, a free-energy function comprising contributions from stretching and polarizing. We show that the free-energy function is typically non-convex, causing the pull-in instability of dielectric elastomers.

This paper presents an electro-mechanical Finite Element Model of an ionic polymer-metal composite (IPMC) material. Mobile counter ions inside the polymer are drifted by an applied electric field, causing mass imbalance inside the material. This is the main cause of the bending motion of this kind of materials. All foregoing physical effects have been considered as time dependent and modeled with FEM. Time dependent mechanics is modeled with continuum mechanics equations. The model also considers the fact that there is a surface of platinum on both sides of the polymer backbone. The described basic model has been under developement for a while and has been improved over the time. Simulation comparisons with experimental data have shown good harmony. Our previous paper described most of the basic model. Additionally, the model was coupled with equations, which described self-oscillatory behavior of the IPMC material. It included describing electrochemical processes with additional four differential equations. The Finite Element Method turned out to be very reasonable for coupling together and solving all equations as a single package. We were able to achieve reasonably precise model to describe this complicated phenomenon. Our most recent goal has been improving the basic model. Studies have shown that some electrical parameters of an IPMC, such as surface resistance and voltage drop are dependent on the curvature of the IPMC. Therefore the new model takes surface resistance into account to some extent. It has added an extra level of complexity to the model, because now all simulations are done in three dimensional domain. However, the result is advanced visual and numerical behavior of an IPMC with different surface characteristics.

Controlling turbulence is a major aim for many engineering disciplines. Decades of research, have shown that the large frictional drag in turbulent flows is attributed to the existence of near-wall coherent structures. Turbulence control is therefore likely to be achieved by manipulating these coherent structures. The challenge this presents is to find actuators that are functional at the spatial scales of those coherent structures (10 μm to 0.1 mm) and their temporal scale (100 kHz). Recent advances in MEMS technology have made possible the construction of such actuators. Electroactive polymers (EAP) provide excellent performance, are lightweight, flexible, and inexpensive. Therefore EAPs, and in particular dielectric elastomers (DEAs), provide many potential applications as micro-actuators. The modelling and simulating of EAP actuators are a cost-effective way of providing a better understanding of the material itself in order to optimise designs. A technique to accurately model DEA materials, taking into account its non-linearities as well as its large deformations, is being developed in this study.

Energy harvesting and storage systems (EHSS) for future AF vehicles are reviewed with emphasis on thermoelectics, organic materials, specifically, dye-sensitized solar cells and polymer batteries. The organic solar cells include solid-state organic solar cells and dye-sensitized solar cells (DSSC). The advantages of using such organic EHSS for AF vehicles are their specific performance, its scalability to larger skin area and low-temperature processing route, thus cost-effective however, there are several technical challenges preventing us to develop the organic EHSS in a speedy way.

Proposed thin film battery is comprised of a polymer-lithium ion cell material with barrier-layer packaging and mechanical reinforcing layers. A semi-solid/ solid electrolyte and a mesoporous polymer separator are sandwiched in between of anode and cathode. A composite film with a carbon nanotube (CNT) network serves as the anode and a mesoporous transitional metal oxide Li_xCoO₂ as the cathode, where porous metal sheets serve as the current collector. The CNT network fabrics have high in-plane tensile strength. LiCoO₂ is used as the cathode, because the Co atoms do not migrate to Li layers, so that cathode does not generate flammable gases during charging that create safety problems. Merit of this study is using the porous metal sheet, which is flexible, lightweight, low electric resistance, high strength and strong stability in alkaline solution. This paper presented development of electrolyte for laminated polymer lithium rechargeable battery. Two-type electrolytes, semi-solid and solid, were attempted; high ionic conductivity of Li ion electrolytes was achieved.

The type of electroactive polymer known as dielectric elastomers has shown considerable promise for a variety of actuator applications and may be well suited for harvesting energy from environmental sources such as ocean waves or water currents. The high energy density and conversion efficiency of dielectric elastomers can allow for very simple and robust "direct drive" generators. Preliminary energy harvesting generators based on dielectric elastomers have been tested. A generator attached to a rotating waterwheel via a crankshaft produced 35 mJ per revolution in a laboratory test with an actual water flow. A generator that harvests the energy of ocean waves for purposes of supplying power to ocean buoys (such as navigation buoys) was tested at sea for two weeks. This buoy-mounted generator uses a proof-mass to provide the mechanical forces that stretch and contract the dielectric elastomer generator. The generator operated successfully during the sea trials. Wave conditions were very small during this test. Although the device did not produce large amounts of power, it did produce net power output with waves as small as 10 cm peak-to-peak wave height. Both the waterwheel and buoy-mounted generators will be scaled up to produce larger amounts of power. The use of significantly larger amounts of dielectric elastomer material to produce generator modules with outputs in the kilowatt range is being investigated for application to ocean wave power systems.

More and more sensors are embedded in human body for medical applications, for sport. The short lifetime of the batteries, available on the market, reveals a real problem of autonomy of these systems. A promising alternative is to scavenge the ambient energy such as the mechanical one. Up to now, few scavenging structures have operating frequencies compatible with ambient one. And, most of the developed structures are rigid and use vibration as mechanical source. For these reasons, we developed a scavenger that operates in a large frequency spectrum from quasi-static to dynamic range. This generator is fully flexible, light and does not hamper the human motion. Thus, we report in this paper an analytical model for dielectric generator with news electrical and mechanical characterization, and the development of an innovating application: scavenging energy from human motion. The generator is located on the knee and design to scavenge 0.1mJ per scavenging cycle at a frequency of 1Hz, enough to supply a low consumption system and with a poling voltage as low as possible to facilitate the power management. Our first prototype is a membrane with an area of 5*3cm and 31µm in thickness which scavenge 0.1mJ under 170V at constant charge Q.

We demonstrate a simple approach to significantly reduce the electrical resistivity of thermo-responsive shape-memory polymers (SMPs), so that they can be easily triggered for shape recovery by Joule heating at a low electrical voltage. After adding a small amount of Ni micro particles into a polyurethane SMP filled with carbon black (CB), the electrical resistivity is slightly reduced. However, if these Ni particles are aligned into chains (by applying a low magnetic field on SMP/CB/Ni solution and then drying to fix the conductive chains), the drop of electrical resistivity is significant. This kind of SMP composites is suitable for cyclic operation as only micro/nano particles are used. A sample (40×15×1mm) with 10vol% of CB and 0.5vol% of chained Ni can be heated to 80°C for shape recovery at 30 V (1.2 W) of power. This approach is generic and applicable for producing other conductive polymers.

Phthalocyanine dyes are well known for their intense absorption in the red and near-IR regions. We synthesized novel phthalocyanines for dye-sensitized solar cell (DSSC). Those dyes can absorb in the red and near-IR regions and adsorb onto the surface of TiO₂. Using such phthalocyanines as working electrode with TiO₂, DSSCs were assembled and its photocurrent-voltage and IPCE characteristics have been studied and compared. Light energy conversion efficiency of DSSCs depended on the structures of phthalocyanine, the co-adsorbent, and the electrolytes. Furthermore, multi-dye type DSSC was investigated, which mixed a phthalocyanine and a carotenoid derivative. The conversion efficiency of the multi-dye DSSC increased compared with the DSSC which used single dye.

Bio-mimetic actuators are inspired to the human or animal organ and they are aimed at replicating actions exerted by the main organic muscles. We present here an inflated dielectric Electroactive Polymer actuator based on acrylic elastomer aiming at mimicing the ocular muscular of the human eye. Two sheets of polyacrylic elastomer coated with conductive carbon grease are sticked to a rotatable backbone, which function like an agonist-antagonist configuration. When stimulating the two elastomer sheets separately, the rotatable mid-arc of the actuator is capable of rotating from -50° to 50°. Experiments shows that the inflated actuator, compared with uninflated one, performs much bigger rotating angle and more strengthened. Connected with the actuator via an elastic tensive line, the eyeball rotates around the symmetrical axes. The realization of more accurate movements and emotional expressions of our native eye system is the next step of our research and still under studied. This inflated dielectric elastomer actuator shows as well great potential application in robofish and adaptive stucture.

Ionic polymer metal composites based on Nafion and Flemion have attracted great attention as an newly developed actuator and sensor materials due to their good performance, such as light weight, good flexibility, low actuation voltage, large strain, good sensitivity. Previous investigations were mostly focused on actuation performance. Recently, we reported some work on flexible tactile sensors based on Flemion ionic polymer metal composites. In this work, we expanded the previous single-dome tactile sensor into a three by three arrayed structure. The correlated substrate and signal collective lines were designed. Several mechanical-electrical relationships on different test domes were obtained when different mechanical input pulses were applied. According to the experiment results, this tactile sensor arrays could achieve good special resolution. By further improving signal circuits, a flexible large-area sensing system could be achieved based on this material. Flemion based ionic polymer metal composites would be a good candidate for bio-related sensors especially for artificial derma applications.

The future of Dielectric Elastomer Actuator (DEA) technology lies in miniaturizing individual elements and utilizing them in array configurations, thereby increasing system fault tolerance and reducing operating voltages. An important direction of DEA research therefore is real-time closed loop control of arrays of DEAs, particularly where multiple degrees-of-freedom are desirable. As the number of degrees-of-freedom increases a distributed control system offers a number of advantages with respect to speed and efficiency. A low bandwidth digital control method for DEA devices is presented in this paper. Pulse Width Modulation (PWM) is used as the basis for a current controlled DEA system that allows multiple degrees-of-freedom to be controlled independently and in parallel using a single power supply set to a fixed voltage. The amplitude and the duty cycle of the PWM signal control the current flow through a high speed, high voltage opto-coupler connected in series with a DEA, enabling continuous control of both the output displacement and speed. Controlling the current in real-time results in a system approaching a stable and robust constant charge system. Closed loop control is achieved by measuring the rate of change of the voltage across the DEA in response to a step change in the current input generated by the control signal. This enables the capacitance to be calculated, which in combination with the voltage difference between the electrodes and the initial dimensions, enables the charge, strain state and Maxwell pressure to be inferred. Future developments include integrating feedback information directly with the control signal, leaving the controller to coordinate rather than control individual degrees-of-freedom.

This paper presents an overview of a new type of thermal micro-actuators using thermally expandable polymers with embedded skeletons. Embedding a stiff skeleton enhances the actuation capability of the thermally expandable polymer. Consequently, the skeleton-reinforced polymers feature a large maximum actuation stress (often above 100 MPa) and a moderate maximum strain (often above 1%) besides a faster thermal response. In addition, the present composite design has room for performance improvement by tuning the volume fraction of the polymeric expander or selecting a proper expander material. Furthermore, the micro-actuators can be taylored for different motion characteristics, using various skeleton shapes. Finally, we discussed the possible applications using the present actuators.

Trilayer actuators were constructed using polypyrrole (PPy) films doped with dodecylbenzene sulfonate (DBS). Identical 5-20 μm PPy/DBS films were grown on either side of a 110 μm poly(vinylidene fluoride) (PVDF) membrane to serve as working and counter electrodes with respect to each other. The performance of the trilayer actuator was tested using potential step experiments between -0.8 and +0.8 V at different frequencies (0.03 to 10 Hz) and trilayer lengths (1 to 2.5 cm), and the extent of deflection was measured using a CCD camera. Satisfactory deflections in the range of 1-3 mm were observed for 10 μm thick PPy layers on trilayers 1.5 to 2.5 cm in length when operated at 1-5 Hz for over 40,000 cycles. The trilayer actuators were examined in a fluidics channels, and mathematical modelling using finite element analysis was used to predict overall fluid movement and flow rates. The trilayers were also used to construct a 'fish-tail' positioned at the back of a self-driven robotic fish.

A concept for the suppression of resonant vibration of an elastic system undergoing forced vibration coupled to electroactive polymer (EAP) actuators based on dielectric elastomers is demonstrated. The actuators are utilized to vary the stiffness of the end support of a clamped beam, which is forced to harmonic vibration via a piezoelectric patch. Due to the nonlinear dependency of the elastic modulus of the EAP material, the modulus can be changed by inducing an electrostrictive deformation. The resulting change in stiffness of the EAP actuator leads to a shift of the resonance frequencies of the vibrating beam, enabling an effective reduction of the vibration amplitude by an external electric signal. Using a custom-built setup employing an aluminum vibrating beam coupled on both sides to electrodized strips of VHB tape, a significant reduction of the resonance amplitude was achieved. The effectiveness of this concept compared to other active and passive concepts of vibration reduction is discussed.

Using proprietary technology, Discover Technologies has developed ionomeric polymer transducers that are capable of long-term operation in air. These "Plastic Muscle^TM" transducers are useful as soft distributed actuators and sensors and have a wide range of applications in the aerospace, robotics, automotive, electronics, and biomedical industries. Discover Technologies is developing novel fabrication methods that allow the Plastic Muscles^TM to be manufactured on a commercial scale. The Plastic Muscle^TM transducers are capable of generating more than 0.5% bending strain at a peak strain rate of over 0.1 %/s with a 3 V input. Because the Plastic Muscles^TM use an ionic liquid as a replacement solvent for water, they are able to operate in air for long periods of time. Also, the Plastic Muscles^TM do not exhibit the characteristic "back relaxation" phenomenon that is common in water-swollen devices. The elastic modulus of the Plastic Muscle^TM transducers is estimated to be 200 MPa and the maximum generated stress is estimated to be 1 MPa. Based on these values, the maximum blocked force at the tip of a 6 mm wide, 35 mm long actuator is estimated to be 19 mN. Modeling of the step response with an exponential series reveals nonlinearity in the transducers' behavior.

Cellulose based Electro-Active Paper (EAPap) has been reported as a smart material that has merits in terms of lightweight, dry condition, biodegradability, sustainability, large displacement output and low actuation voltage. However, its actuator performance is sensitive to humidity: its maximum bending performance was shown at high humidity condition. To overcome this drawback, we introduce an EAPap made with cellulose and chitosan blend. Cellulsoe-chitosan blend films with varied mixing ratio were prepared by dissolving the polymers in trifluoroacetic acid as a co-solvent followed by spincoating onto glass substrates. A bending EAPap actuator is made by depositing thin gold electrodes on both sides of the cellulose-chitosan films. The performance of the EAPap actuator is evaluated in terms of free bending displacement with respect to the actuation frequency, activation voltage, humidity level and content of chitosan. The actuation principle is also discussed.

Ras Labs, LLC, is committed to producing a variety of electroresponsive smart materials that are strong, resilient, and respond quickly and repeatedly to electrical stimuli. By effectively combining the synthetic expertise of Ras Labs with the plasma expertise of the Princeton University Plasma Physics Laboratory (PPPL), Ras Labs is actively developing superior electroresponsive materials and actuators. One of the biggest challenges is the interface between the embedded electric electrodes and the electroresponsive material because of the pronounced movement of the electroresponsive material. If the electroresponsive material moves very quickly, the electric lead is often left behind and thus becomes detached. Preliminary experiments explored the bonding between these electroresponsive materials with plasma treated metals provided by PPPL. The results were encouraging, with much better bond strengths in the plasma treated metals compared to the untreated control. Ras Labs expanded upon improving the attachment of the embedded electric leads to the electroresponsive materials in these actuators using plasma treatment and other treatments to non-corrosive metal leads at PPPL. Water drop contact angle tests were performed on plasma treated stainless steel and titanium. The strength of the metal-polymer interface was determined at TRI/Princeton using modified T-peel tests on samples of electroresponsive material sandwiched between plasma treated stainless steel and titanium foils. Based on the water drop contact angle tests and the T-peel tests, nitrogen plasma treatment of titanium produced the best metal-polymer interface. Metallic plasma treatment allowed for the embedded electric leads and the electroresponsive material to work and move as a unit, with no detachment, by significantly improving the interface between the electric leads and the electroresponsive material.

This paper discusses the design, fabrication and characterization of lens for smart sunglasses based on electrochromic devices. The prepared electrochromic device was fabricated with ITO coated PET plastic. The working EC material film was poly [3,3-dimethyl-3,4-dihydro-2H-thieno [3,4-b][1,4]dioxepine] (PProDOT-Me₂), while the counter layer of the device was vanadium oxide titanium oxide (V₂O₅/TiO₂) composite film, which serves as an ion storage layer. A solution type electrolyte as the ionic transport layer was sandwiched between the working and counter layers. The lens exhibited tuneable shade in visible light wave length, with a maximum contrast ratio at 580nm.

IPMC-EMIM (Ionic Polyer Metal Composites + 1-ethyl-3- methyl imidazolium trifluromethane sulfonate, EMIM-Tfo) is fabricated by substituting ionic liquid for water in Nafion film, which improves water sensitiveness of IPMC and guarantees uniform performance regardless of the surrounding environment. In this paper, we will briefly introduce the procedure of fabrication of IPMC-EMIM and proceed to introduce the Hook-type actuator using IPMC-EMIM and application to AF Lens actuator. Parameters of Hook-type actuator are estimated from experimental data. In the simulation, The proposed AF Lens Actuator is assumed to be a linear system and based on estimated parameters, PID controller will be designed and controlled motion of AF Lens actuator will be shown through simulation.

Small, highly-mobile "swimming" robots are desired for underwater monitoring operations, including pollution detection, video mapping and other tasks. Actuator materials of all types are of interest for any application where space is limited. This constraint certainly applies to the small-scale swimming robot, where multiple small actuators are needed for forward/backward propulsion, steering and diving/surfacing. A number of previous studies have demonstrated propulsion of floating objects using IPMC type polymer actuators [1-3] or piezoceramic actuators [4, 5]. Here, we show how propulsion is also possible using a multi-layer polypyrrole bimorph actuator. The actuator is based on our previously published work showing very fast resonance actuation in polypyrrole bending-type actuators [6]. The bending actuator is a tri-layer structure, in which the gold-PVDF (porous poly(vinylidene fluoride) membrane) substrate was coated on both sides with polypyrrole layers to form an electrochemical cell. Polypyrrole films on gold coated PVDF were grown galvanostatically at a current density of 0.10 mA/cm2 for 12 hours from propylene carbonate (PC) solution containing 0.1 M Li+TFSI-, 0.1 M pyrrole and 1% (w/w) water. The polypyrrole deposited PVDF was thoroughly rinsed with acetone and stored in 0.1 M Li+TFSI- / PC solution. The edges of the bulk film were trimmed off and the bending actuators were prepared as rectangular strips typically 2mm wide and 25 mm long. These actuators gave fast operation in air (to 90 Hz), and were utilised as active flexural joints on the tail fin of a fishshaped floating "boat". The actuators were attached to a simple truncated shaped fin and the deflection angle was analysed in both air and liquid for excitation with +/- 1V square wave at a range of frequencies. The mechanical resonance of the fin was seen to be 4.5 Hz in air and 0.45 Hz in PC, which gave deflection angles of approximately 60° and 55° respectively. The boat contained a battery, receiver unit and electronic circuit attached to the actuator fin assembly. Thus, the boat could be operated by remote control, and by varying the frequency and duty cycle applied to the actuator, the speed and direction of the boat could be controlled. The boat had a turning circle as small as 15 cm in radius and a maximum speed of 2m/min when operating with a tail frequency of approximately 0.7 Hz. The efficiency of the flapping tail fin was analysed and it was seen that operation at this frequency corresponded with a Strouhal number in the optimal range.

The objective of the present work is to demonstrate the efficiency and feasibility of NBR (Nitrile Butadiene Rubber) based conducting polymer actuator that is fabricated into a micro zoon lens driver. Unlike the traditional conducting polymer that normally operates in a liquid, the proposed actuator successfully provides fairly effective driving performance for the zoom lens system in a dry environment. And this paper is including the experiment results for an efficiency improvement. The result suggested by an experiment was efficient in micro optical zoom lens system. In addition, the developed design method of actuator was given consideration to design the system.

Step-motor, piezo, liquid lens and voice coil motor (VCM) have been thought as good candidates for actuators in auto-focusing compact camera module (CCM). Currently, VCMs take possession of big place in auto-focusing CCM market. However, VCMs have limitations in developing thin, low-power CCMs. Therefore, ionic polymer-metal composites (IPMCs) could be thought as one of the best candidates in developing auto-focusing CCM due to their well-known characteristics such as low-power consumption and large displacement. It is required that fast bending response (20 μm/20 ms) and large blocking force (800 mgf) should be achieved for the practical applications of IPMCs in developing auto-focusing CCM. Here, we present the method for increasing IPMC's bending response and displacement by anisotropic plasma treatment. Furthermore, we demonstrate the fabrication of a prototype of CCM actuated by IPMC and its remarkable low power consumption.

The dynamic response of dielectric elastomer membranes subject to time-varying voltage inputs for various initial inflation states is investigated. These results provide new insight into the differences observed between quasi-static and dynamic actuation and presents a new challenge to modeling efforts. Dielectric elastomer membranes are a potentially enabling technology for soft robotics and biomedical devices such as implants and surgical tools. In this work, two key system parameters are varied: the chamber volume and the voltage signal offset. The chamber volume experiments reveal that increasing the size of the chamber onto which the membrane is clamped will increase the deformations as well as cause the membrane's resonance peaks to shift and change in number. For prestretched dielectric elastomer membranes at the smallest chamber volume, the maximum actuation displacement is 81 microns; while at the largest chamber volume, the maximum actuation displacement is 1431 microns. This corresponds to a 1767% increase in maximum pole displacement. In addition, actuating the membrane at the resonance frequencies provides hundreds of percent increase in strain compared to the quasi-static strain. Adding a voltage offset to the time-varying input signal causes the membrane to oscillate at two distinct frequencies rather than one and also presents a unique opportunity to increase the output displacement without electrically overloading the membrane. Experiments to capture the entire motion of the membrane reveal that classical membrane mode shapes are electrically generated although all points of the membrane do not pass through equilibrium at the same moments in time.

This study expands the number of novel synthetic ionomers specifically designed for performance as ionic polymer transducers (IPT) membranes, specifically employing a highly branched sulfonated polysulfone. Control of the synthetic design, characterization, and application of the novel ionomer is intended to allow fundamental study of the effect of polymer branching on electromechanical transduction in IPTs. Fabrication methods were developed based upon the direct application process (DAP) to construct a series of stand-alone electrodes as well as full IPTs with corresponding electrode compositions. Specifically, the volumetric ratio of RuO₂ conducting particles to the novel ionomeric matrix was varied from 0 - 45 vol % in the electrodes. Electrical impedance spectroscopy was employed to determine the electrical properties and their variation with electrode composition separate from and in the IPT. A percolation threshold was detected for increased ionic conductivity of the stand-alone electrodes and the full IPTs based on increased loading of conducting particles in the electrodes. An equivalent electrical circuit model was applied to fit the impedance data and implicated interfacial and bulk effects contributing differently to the electrical properties of the electrodes and IPT as a whole. The fabricated IPT series was further tested for bending actuation in response to applied step voltages and represents the first demonstration of IPTs constructed with the DAP process using 100 % novel ionomer in all components. The percolation behavior extended to the bending actuation responses for strain and voltage-normalized strain rate and is useful in optimizing IPT components for maximum performance regardless of the ionomer employed.

Optical gratings are used for light steering, wavelength separation, and filtering. So far, tunable diffraction gratings were based on relatively stiff materials allowing only a limited spatial tuning range. In this paper, we describe a technology for the implementation of shape changing, electrically adjustable, transmissive optical elements. To achieve large shape changes, soft optical materials and dielectric elastomer actuators (DEAs) are combined. The discussed optical transmission gratings operate with high transmission (> 90 %), good optical quality, high damage threshold (> 93 kW/cm²), are polarization independent, and achieve very large, continuous changes in their main optical properties (7.5 % in-plane compression of the active optical region). Further, the excellent properties of the novel optical components are highlighted by the implementation of a low cost, objective launched, total internal reflection fluorescence (TIRF) microscope that can be switched from epifluorescence operation to TIRF mode by simply applying a voltage to a DEA tuned diffractive transmission grating.

In this paper, we introduce a novel, self-sensing technique for dielectric elastomer (DE) actuators which will adequately measure the in-situ impedance variation of the DE under a deformation. A standard signal processing technique was introduced to accurately mix and extract actuating and sensing signals. Although the technique is limited to the actuation-bandwidth of several tens of Hz, its practical use for applications and tests is attractive. With the proposed technique, the self-sensing actuation system was effectively demonstrated without using auxiliary sensors. The proposed technique is useful for many attractive robotic applications including space-limited micro-actuation systems and multi-DOF systems that use hyper redundant manipulators.

Conducting polymer trilayers are attractive for use in functional devices, given low actuation voltages, operation in air and potentially useful stresses and strains; however, their dynamic behavior must be understood from an engineering perspective before they can be effectively incorporated into a design. As a step towards the identification of the actuator dynamics, frequency response analysis has been performed to identify the magnitude and phase shift of displacement in response to a sinusoidal voltage input. The low damping of the trilayer operating in air and the use of a laser displacement sensor has allowed the frequency response to be continuously identified up to 100Hz, demonstrating a resonant peak at 80Hz for a 10mm long actuator. Two linear transfer function models have been fitted to the frequency response of the trilayer displacement (i) a 3rd order model to represent the dynamics below 20Hz and (ii) a higher complexity 6th order model to also include the resonant peak. In response to a random input signal, the 3rd order model coarsely follows the experimental identified displacement, while the 6th order model is able to fully simulate the real trilayer movement. Step responses have also been obtained for the 3rd and 6th order transfer functions, with both models capable of following the first 4 seconds of experimental displacement. The application of empirical transfer function models will facilitate accurate simulation and analysis of trilayer displacement, and will lead to the design of accurate positional control systems.

The conductive polymer polyaniline is typically blended with conventional industrial thermoplastics in order to obtain an electrically conductive polymer blend with adequate mechanical properties. Processing these polyblends into foams yields a porous conductive material that exhibits immense application potential such as dynamic separation media and low-density electrostatic discharge protection. In the current study, the morphology of a thermally-processable blend consisting of an electrically conductive polyaniline-dodecylbenzene sulfonic acid complex and poly(methyl methacrylate) is explored using a two-phase batch foaming setup. The effect of blend composition and processing parameters on the resulting cellular morphology is investigated. Finally, the impact of the underlying microstructure on the frequency dependent electrical conductivity is elucidated.

A solution made from blending cycloolefin copolymer (COC) and polystyrene (PS) was proposed to create a double-sided electret polymer film. This electret polymer was then sandwiched to form an electret-metal-electret structure by using the MEMS processes. The upper and lower polymer layers were found to both enhance charge storage capacity significantly and to improve the machining property. It was identified that lower concentration of PS led to sphere-like morphology distributed uniformly within the COC/PS blends, which created better electret properties than that of pure COC or pure PS polymers. In addition, it was also found that these COC/PS blends have better adhesion to both metal and polymers. A series of processes developed to optimize this line of new electret polymers for actuator development are detailed. The recipe of this new material and the associated fabricating process to develop an electret loudspeaker are also detailed. In comparison, the pros and cons of this speaker system versus a typical electrostatic loudspeaker or a headphone, which require both bulky and expensive DC-to-DC converters, are detailed as well.

Electro-active paper (EAPap) is a new smart material that has a potential to be used in biomimetic actuator and sensor. It is made by cellulose that is very abundant material in nature. This material is fascinating with its biodegradability, lightweight, large displacement, high mechanical strength and low actuation voltage. It has been reported that ionic and piezoelectric effects play a dominant roll in the actuation mechanism. However, the electromechanical actuation mechanisms are not clearly established yet. This paper presents the modeling of the actuation behavior of water infused cellulose samples and their composite dielectric constant calculated by Maxwell- Wagner theory. Electro-mechanical forces are calculated using Maxwell stress tensor method. Also, bending deflection is evaluated from simple beam model and compared with experimental observation.

There is growing interest in searching for new smart materials, which responds to external stimuli by changes in shape or size and can be utilized in biomimetic motions. To develop artificial muscles with improved performance, a novel electro-active polymer actuator was prepared by employing the newly-synthesized ionic networking membrane of poly (styrene-alt-maleimide) (PSMI)-incorporated poly (vinylidene fluoride) (PVDF). Scanning electron microscope (SEM) and transmission electron microscopy (TEM) revealed that much smaller and more uniform platinum particles were formed on the surfaces of the actuator fabricated through the electroless-plating technique as well as within its polymer matrix. Under constant voltage excitation, the tip displacement of the actuator constructed with the ionic network membrane was several times larger than that of its Nafion^(R) counterpart of similar thickness without straightening-back. Under the stimulus of alternating-current voltage, the newly-developed actuator displayed an excellent harmonic performance, and the measured mechanical displacement was comparable to that of the Nafion^(R)-based actuator. The nice electromechanical response, especially the large tip displacement, is attributed to two factors: the inherent large ionic-exchange capacity and the unique hydrophilic nanochannels of the ionic networking membrane. The actuator of PSMI-incorporated PVDF has some advantages over the most widely-used traditional Nafion-based actuator by diversifying niche applications in biomimetic motion, and the present study may possibly open a new avenue for the design and fabrication of the electro-active polymer with unique functional properties.

Composite actuators consisting of sheets of the solid polymer electrolyte (similar to Nafion^(R)) with Cu²⁺ counter-ions inserted and coated with platinum and copper metal layers (so-called Ionomeric Polymer-Metal Composites; IPMCs) have been synthesised and their electromechanical performance upon actuation has been monitored. Resistance measurements on the electrodes show that the electrical conductivity of the membranes metal surface increases on the cathode side during the actuation process, contradictory to the situation when Cu is absent from the metal coating. This phenomenon is explained by the subsequent reduction of Cu²⁺ ions on the cathode upon actuation; Cu layer growth in this side prevents it from cracking and decreases its electrode resistance. The phenomenon opens up for longer life-times for Cu-based IPMCs. However, additional problems with Cu layer oxidation and Cu dendrite growth on the electrodes should be considered.

IPMC (Ionic Polymer Metal Composite) is a class of electroactive polymers (EAP) that bend when electric field is applied to the material. From our theoretical studies of the material it appears that IPMC can be modelled as a lossy transmission line. From simulations it appears that IPMC reaction time depends on length of the strip used. Also the shorter the transmission line the less complex it is to model. We have also mechanically modeled an IPMC. It appears that the output force does not depend on length on IPMC but on width. Also the shape unpredictability is the larger the longer the strip is. Based on these results the concept of a short IPMC with rigid extension was created. From simulations and experiments it was seen that there exists a certain length of IPMC at which output force and deflection angle remain close to those of a long IPMC while precision increases. Also, the material becomes easier to model and its short-term stability appears to be sufficient to be controlled. A manipulator was built to verify IPMC compatibility as links, tested for accuracy and compared with a long sheet of IPMC. The manipulator appeared to be 314% more accurate and twice as fast compared to the long strip of an IPMC and thus confirming the usability of the described design.

The actuation properties of free standing films of poly-3,4-ethylenedioxythiophene (PEDOT) prepared from propylene carbonate (PC) solutions of tetrabutylammonium trifluromethanesulfonate have been studied in a range of aqueous and organic (PC) solvent electrolytes. The following electrolyte salts were investigated: TBACF₃SO₃, LiCF₃SO₃, TBAPF₆, NaPF₆, NaDBS and TMACl. The best actuation performance was achieved in TMACl (aq.) with >4 % strain, 0.18 % s^-1 strain rate and a low creep of 2.3 % after 50 cycles using potential step experiments. The PEDOT film morphology was significantly changed from an open sub-micron pore polymer network to a morphology with fewer and less open pores when the solvent was changed from PC to water.

Trilayer polypyrrole benders are capable of generating voltages and currents when applied with an external force or displacement, demonstrating potential as mechanical sensors. Previous work has identified the effects of dopant and electrolyte on the sensor output, and a 'deformation induced ion flux' model was proposed. The current work aims to identify the change in sensor response with input amplitude and bender geometry as a function of frequency. The current and charge output from the trilayer benders were found to increase proportionally with input displacement and bender strain for multiple input frequencies, indicating linearity. Sensitivities of the current and charge output have also been calculated in response to strain, and are found to increase as the volume of the conducting polymer is increased. Some guidelines for sensor geometry are then suggested, using the identified sensitivities as a guide.

Stacked dielectric elastomer actuators (DEA) act as solid state actuators. Modeling such an electromechanical system demands the knowledge about the mechanical and electrical parameters of the used materials as well as the real static and dynamic behavior. In elastomer actuators the electrical properties of the materials might change with applied mechanical stress or applied voltage as it is known from some materials (e. g. polyacryl). Therefore, we examined the PDMS used in stacked dielectric elastomer actuators regarding such dependencies. We present results from testing the permittivity of two different silicones (Elastosil P7670, Wacker Silicones; RTV410, Bayer) versus mechanical stress, frequency of the driving voltage, film thickness and curing temperature. The resulting movement of a stacked actuator is not a single displacement of the elements but a rather complex bulk deformation. Therefore, a planar displacement measurement system is necessary. Laser displacement sensors offer the possibility of a two-sided measurement. This allows to determine the actual thickness variation even if the actuator array moves out of plane. The setup includes a prestretching device to clamp the actuators symmetrically and to simulate an uniaxial load. The realized measurement setup has an effective vertical measurement range of 10 mm, a resolution of 100 nm at a sample rate of 20 kHz. This allows the static and dynamic displacement measurement of planar actuators.

Stacked dielectric elastomer actuators are fabricated by an automated process using spin coating of uncured elastomers. To improve the performance of these multilayer actuators we present two different ways. To reduce the driving voltage it is desirable to fabricate dielectric films with a thickness below 20 μm. This can be achieved by high speed spin coating of an uncured elastomer. Analyzing the automated process reveals nine principal process parameters. An adequate design of experiment reduces the number of necessary tests to an acceptable value. With these results we are able to spin thin films with a thickness of less than 5 μm and a thickness variation of about 3%. Secondly, we examine the influence of nanosized particles of metal oxide powder on the permittivity of the elastomer film. Three different materials, namely aluminiumoxide, titaniumdioxide and bariumtitanate with a bulk permittivity of about 10, 100, 1000, respectively, are used to increase the overall permittivity of the composite. To predict the resulting performance of an elastomer actuator the figure of merit Κ is introduced.

This paper discusses a model of IPMC sensors and the characteristics of the frequency responses. There are two different methods of measurements, the current sensing and the voltage sensing, which exhibit completely different frequency responses each other. A simple model based on Onsager's equation is shown in order to explain the experimental results of the current sensing. The voltage sensing model is derived by the equivalent transform of the voltage and the current sources. In contrast to the constant gain of the charge response, the characteristics of the voltage response are directly related to the impedance dynamics. In the experiments, the frequency responses of the charge/current sensing and the voltage sensing for two species of counter ion are measured. The ratio of the obtained frequency responses and the measured impedance are also compared to validate the voltage sensing model. Though the theoretical prediction of the sensor coefficient does not match the experimental one, the structure of the model agrees with the experimental data.

The IPMC-EMIM actuator is an improved IPMC actuator to replace the water by stable ionic liquids (1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([EtMeIM][TA])). Just as a general IPMC actuator which uses the solvent of water has hysteresis, so do the IPMC-EMIM actuator exhibits hysteresis like other smart materials such as piezoceramics (PZT), magnetostrictive materials, and shape memory alloys (SMA). Hysteresis can cause it to be unstable in closed loop control. The Preisach Model has been used to model the hysteretic response arising in PZT and SMA. Noting the similarity between IPMC-EMIM and other smart materials, we apply the Preisach model for the hysteresis in the IPMC-EMIN actuator. This paper reviews the basic properties of the Preisach model and confirms that the Preisach model of IPMC-EMIM actuator is possible.

DE EAP(Dielectric Elastomer ElectroActive Polymer) has advantages in its weight, ease of fabrication and low power consumption. There are many efforts applied to various field in recent ten years. But the present modeling is not enough to appear its characteristics because of its hysteresis. In this paper, we propose modeling of DE EAP with Preisach Model that is used in order to model the hysteretic response arising in PZT and SMA. The modeling of DE EAP with Presach model is verified by experiment with various DE EAP actuators.

Molecular Dynamics (MD) techniques have been used to study the structure and dynamics of a model system of an interpenetrating polymer (IPN) network for actuator devices. The systems simulated were generated using a Monte Carlo-approach, and consisted of poly(ethylene oxide) (PEO) and poly(butadiene) (PB) in a 80-20 percent weight ratio immersed into propylene carbonate (PC) solutions of LiClO₄. The total polymer content was 32%, in order to model experimental conditions. The dependence of LiClO₄ concentration in PC has been studied by studying five different concentrations: 0.25, 0.5, 0.75, 1.0 and 1.25 M. After equilibration, local structural properties and dynamical features such as phase separation, coordination, cluster stability and ion conductivity were studied. In an effort to study the conduction processes more carefully, external electric fields of 1×10⁶ V/m and 5×10⁶ V/m has been applied to the simulation boxes. A clear relationship between the degree of local phase separation and ion mobility is established. It is also shown that although the ion pairing increases with concentration, there are still significantly more potential charge carriers in the higher concentrated systems, while concentrations around 0.5-0.75 M of LiClO₄ in PC seem to be favorable in terms of ion mobility. Furthermore, the anions exhibit higher conductivity than the cations, and there are tendencies to solvent drag from the PC molecules.

With the aim of discovering, designing and developing a novel actuator, existing technologies are broken down into components. These are the material or phenomena that provide mechanical power, the type of stimulus required to "excite" the technology and the geometrical arrangement, or configuration of the technology to manifest as an actuator. To date, a number of attempts have been made to classify and compare actuators. Existing comparisons typically use active material performance as a source for actuator data, even though a material alone is not active. A stimulus generation must be present for an active material to be used as an actuator and the addition of local stimulus generation can severely affect the performance of an actuator. Little or no attempt to classify different actuation technologies and configurations with consideration of the nature and provision of stimulus has been made. By classification of stimulus and actuator configuration, many further research areas are identified. The structured actuator categorisation along with a fundamental view of the requirements of an actuator forms the basis of an engineering biased selection strategy.

Dielectric elastomer actuators (DEAs) are a promising artificial muscle technology that will enable new kinds of prostheses and wearable rehabilitation devices. DEAs are driven by electric fields in the MV/m range and the dielectric elastomer itself is typically 30μm in thickness or more. Large operating voltages, in the order of several kilovolts, are then required to produce useful strains and these large voltages and the resulting electric fields could potentially pose problems when DEAs are used in close proximity to the human body. The fringing electric fields of a DEA in close association with the skin were modelled using finite element methods. The model was verified against a known analytic solution describing the electric field surrounding a capacitor in air. The agreement between the two is good, as the difference is less than 10% unless within 4.5mm of the DEA's lateral edges. As expected, it was found that for a DEA constructed with thinner dielectric layers, the fringe field strength dropped in direct proportion to the reduction in applied voltage, despite the internal field being maintained at the same level. More interestingly, modelling the electric field around stacked DEAs showed that for an even number of layers the electric field is an order of magnitude less than for an odd number of layers, due to the cancelling of opposing electric fields.

The electromechanical performance of interpenetrating polymer networks (IPN) in which one elastomer network is under high tension balanced by compression of the second network, were investigated. Uniaxial stress relaxation analysis confirmed significant decrease in viscoelasticity in comparison with 3M VHB films, the primary component network in the IPN films. In dynamic mechanical analysis, the IPN composite showed a higher mechanical efficiency, suggesting delayed relaxation of the acrylic chains in the presence of IPN formation. This improvement was found to be dependant on the contents of poly(TMPTMA). Actuation performance without mechanical prestrain showed that these IPN electroelastomers had demonstrated high elastic strain energy density (3.5 MJ/m³) and a high electromechanical coupling factor (93.7%). These enhanced electromechanical performances indicate that IPN electroelastomer should be suitable for diverse applications.

One problem related to the actuation principle of macroscopic dielectric elastomer actuators is the high voltage required, typically in the Kilovolt range, that imposes particular care in the insulation of the whole actuator from the surrounding environment. This high actuation voltage, however, can be drastically reduced if a thin film of dielectric elastomer is used. Despite this, the manufacture of a macroscopic stack-like actuator, starting from thin films of dielectric elastomer can present many manufacture difficulties, like the handling and the assembly of the films, the power distribution to hundreds or thousands of layers, the presence of defects in one single layer that can cause the complete failure of the whole actuator. In this paper, a fast, semi-automatic process is proposed for the manufacture of modular units of dielectric elastomer, each of them consisting of many layers of rolled thin dielectric film. All the manufactured units are independent and take their power from a lateral, compliant supply rail that contacts the sides the electroded layers. This design is very suitable for industrial production: each module can be independently tested and then assembled in a complete macroscopic actuator composed by an unlimited number of these modules. The simple assembly methodology and the semi-automatic manufacture process described in this paper allows the fabrication of multilayer stacked devices, that can be used both as contractile or expanding actuators.