This PDF file contains the front matter associated with SPIE Proceedings volume 7287, including the Title Page, Copyright information, Table of Contents, Introduction, and the Conference Committee listing.

This paper presents a brief review of our ongoing work on the biomechanical simulation of the human body. Our comprehensive musculoskeletal model, which includes more or less all of the relevant articular bones and muscle actuators, plus soft tissue deformations, raises the challenge of simulating natural body movements by controlling hundreds of contractile muscles. We have begun to confront this problem by developing a trainable neuromuscular controller for the important special case of the neck-head-face complex. Additionally, I briefly review our relevant earlier work on the motor control of anthropomorphically articulated dynamic models, as well as the biomechanical modeling of lower animals such as fish, including motor control algorithms that enable these simulated animals to learn natural, muscle-actuated locomotion.

Human-like robots are increasingly becoming an engineering reality thanks to recent technology advances. These robots, which are inspired greatly by science fiction, were originated from the desire to reproduce the human appearance, functions and intelligence and they may become our household appliance or even companion. The development of such robots is greatly supported by emerging biologically inspired technologies. Potentially, electroactive polymer (EAP) materials are offering actuation capabilities that allow emulating the action of our natural muscles for making such machines perform lifelike. There are many technical issues related to making such robots including the need for EAP materials that can operate as effective actuators. Beside the technology challenges these robots also raise concerns that need to be addressed prior to forming super capable robots. These include the need to prevent accidents, deliberate harm, or their use in crimes. In this paper, the potential EAP actuators and the challenges that these robots may pose will be reviewed.

The priority programme "Intelligent Hydrogels" was established by the German Research Foundation (DFG) in 2006 in order to strengthen the hydrogel-related research in Germany. The programme is being coordinated by Gabriele Sadowski, Technische Universität Dortmund. The aim of this priority programme is to develop new methods for the synthesis and characterization of smart hydrogels and to develop new modelling strategies in order to a) prepare the hydrogels for special applications and/or b) to develop and extend their capabilities for any desired use. In this programme, 73 scientists (36 professors and 37 scientific assistants/PhD students) from all over Germany are involved, working in 23 projects.

Ctenophores or "comb jellies" are small sea creatures that propel themselves with rows of ciliated bending actuators or 'paddles'. In some species the actuators are coordinated via mechano-sensitivity; the physical contact of one paddle triggers the motion of the next resulting in a wave of activation along the row. We seek to replicate this coordination with an array of capacitive self-sensing Dielectric Elastomer Minimum Energy Structure(s) (DEMES) bending actuators. For simplicity we focused on a conveyor application in air where four DEMES were used to roll cylindrical loads along some rails. Such a system can automatically adjust to changing load dynamics and requires very little computational overhead to achieve coordination. We used a finite element modelling approach for DEMES development. The model used a hybrid Arruda-Boyce strain energy function augmented with an electrostatic energy density term to describe the DEA behaviour. This allowed the use of computationally efficient membrane elements giving simulation times of approximately 15 minutes and thus rapid design development. Criteria addressing failure modes, the equilibrium state, and stroke of the actuators were developed. The model had difficulty in capturing torsional instability in the frame thus design for this was conducted experimentally. The array was built and successfully propelled teflon and brass rollers up an incline. Noise in the capacitive sensor limited the sensitivity of the actuators however with PCB circuit fabrication this problem should be solved.

The excellent overall performance and compliant nature of Dielectric Elastomer Actuators (DEAs) make them ideal candidates for artificial muscles. Natural muscle however is much more than just an actuator, it provides position feedback to the brain that is essential for the body to maintain balance and correct posture. If DEAs are to truly earn the moniker of "artificial muscles" they need to be able to reproduce, if not improve on, this functionality. Self-sensing DEAs are the ideal solution to this problem. This paper presents a system by which the capacitance of a DEA can be sensed while it is being actuated and used for feedback control. This system has been strongly influenced by the desire for portability i.e. designed for use in a battery operated microcontroller based system. It is capable of controlling multiple independent DEAs using a single high voltage power supply. These features are important developments for artificial muscle devices where accuracy and low mass are important e.g. a prosthetic hand or force-feedback surgical tools. A numerical model of the electrical behaviour of the DEA that incorporates arbitrary leakage currents and the impact of arbitrary variable capacitance has been created to model a DEA system. A robust capacitive self-sensing method that uses a slew-rate controlled Pulse Width Modulation (PWM) signal and compensates for the effects of leakage current and variable capacitance is presented. The numerical model is then used to compare the performance of this new method with an earlier method previously published by the authors.

We consider the embodiment of a microbial fuel cell using artificial muscle actuators. The microbial fuel cell digests organic matter and generates electricity. This energy is stored in a capacitor bank until it is discharged to power one of two complimentary artificial muscle technologies: the dielectric elastomer actuator and the ionic-polymer metal composite. We study the ability of the fuel cell to generate useful actuation and consider appropriate configurations to maximally exploit both of these artificial muscle technologies. A prototype artificial sphincter is implemented using a dielectric elastomer actuator. Stirrer and cilia mechanisms motivate experimentation using ionic polymer metal composite actuators. The ability of the fuel cell to drive both of these technologies opens up new possibilities for truly biomimetic soft artificial robotic organisms.

Artificial skin materials were synthesized using platinum-cured silicone elastomeric material (Reynolds Advanced Materials Inc.) as the base consisting of mainly polyorganosiloxanes, amorphous silica and platinum-siloxane complex compounds. Systematic incorporation of porosity in this material was found to lower the force required to deform the skin in axial direction. In this study, we utilized foaming agents comprising of sodium bicarbonate and dilute form of acetic acid for modifying the polymeric chain and introducing the porosity. Experimental determination of functional relationship between the concentration of foaming agent, slacker and non-reactive silicone fluid and that of force - deformation behavior was conducted. Tensile testing of material showed a local parabolic relationship between the concentrations of foaming agents used (per milliliter of siloxane compound) and strain. This data can be used to optimize the amount of additives in platinum cured silicone to obtain desired force - displacement characteristics. Addition of "silicone thinner" and "slacker" showed a monotonically increasing strain behavior. A mathematical model was developed to arrive at the performance metrics of artificial skin.

Among the electronic polymers EAPs especially the dielectric elastomers are functional materials that have promising potential as muscle-like actuators due to their inherent compliancy and good overall performance. The combination of huge active deformations, high energy densities, good efficiencies and fast response is unique to dielectric elastomers. Furthermore, they are lightweight, have a simple structure and can be easily tailored to various applications. Up to now most scientific research work has been focused on the planar expanding actuation mode due to the fact that the commercially available acrylic material VHB 4910 (3M) can easily be processed to planar actuators and has demonstrated very high actuation performance when pre-strained. Many different actuator designs have been developed and tested which expands in plane when voltage is applied and shrinks back as soon as the applied charges are removed from the electrodes. Obviously the contractive operation mode at activation is required for a wide range of application. Due to the principle of operation of soft DE EAP, mainly two directions to performed work against external loads are possible. Beside of the commonly used expanding actuation in planar direction the contractile actuation in thickness direction of the DE film represents a very promising option in the multilayer configuration. First approaches have been presented by the folded actuator design and by the multilayer tactile display device. In this study a novel approach for active structures driven by soft dielectric EAP is presented, which can perform contractive displacements at external tensile load. The device is composed of an array of equal segments, where the dielectric films are arranged in a pile-up configuration. In order to maintain satisfying structural integrity when external tension load is applied special attention was paid to the compliant electrode design which takes a central importance concerning the force transmission capability between each layer of the actuator. Due to the stack configuration of the actuator the commonly used and pre-strained acrylic film was replaced by the stress-free IPN modified acrylic film in order to eliminate the need for external pre-strain-supporting structures. Introductorily, the specific problems on conventional expanding actuators are discussed and the aims for contractive tension force actuators are specified. Then some structural design parameters are addressed in order to achieve a high rate of yield 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.

The miniaturization of dielectric elastomer actuators requires compliant electrodes that are clean, reliable, and that can be easily patterned on a mm or μm scale. Carbon-based electrodes, which are commonly used to make large-scale actuators, are not well suited for this application. Metal ion implantation at low energies has, on the other hand, the ability to create compliant and patternable electrode through the creation of nanometer scale clusters in the first tens of nanometers below the elastomer surface. We present the mechanical and electrical properties of metal (Au, Pd, Ti, Cu) implanted electrodes on polydimethylsiloxane, as well as the application of Au-implanted electrode to the fabrication of small-size (∅1.5-3 mm) diaphragm actuators that exhibit vertical displacements up to 25% of their diameter.

The rapidly growing adoption of dielectric elastomer (DE) actuators as a high performance EAP technology for many kinds of new applications continuously opens new technical challenges, in order to take always the most from each adopted device and actuating configuration. This paper presents a new type of DE actuators, which show attractive potentialities for specific application needs. The concept here proposed adopts an incompressible fluid to mechanically couple active and passive parts. The active parts work according to the DE actuation principle, while the passive parts represent the end effector, in contact with the load. The fluid is used to transfer actuation hydrostatically from an active to a passive part and, then, to the load. This can provide specific advantages, including improved safety and less stringent design constraints for the architecture of the actuator, especially for soft end effectors. Such a simple concept can be readily implemented according to different shapes and intended functionalities of the resulting actuators. The paper describes the structure and the performance of the first prototype devices developed so far.

Tubular dielectric electro-active polymer actuators, also referred as tubular InLastors, have many possible applications. One of the most obvious is as a positioning push-type device. This work examines the feedback closed-loop control of a core-free tubular InLastor fabricated from sheets of PolyPowerTM, an EAP material developed by Danfoss PolyPower A/S, which uses a silicone elastomer in conjunction with smart compliant electrode technology. This is part of an ongoing study to develop a precision positioning feedback control system for this device. Initially proportional and integral (PI) control is considered to provide position control of the tubular InLastor. Control of the tubular Inlastors require more than conventional control, used for linear actuators, because the InLastors display highly nonlinear static voltage-strain and voltage-force characteristics as well as dynamic hysteresis and time-dependent strain behavior. In an attempt to overcome the nonlinear static voltage-strain characteristics of the Inlastors and for improving the dynamic performance of the controlled device, a gain scheduling algorithm is then integrated into the PI controlled system.

We present a new approach to the fabrication of soft dielectric elastomer actuators using a 3D printing process. Complete actuators including active membranes and support structures can be 3D printed in one go, resulting in a great improvement in fabrication speed and increases in accuracy and consistency. We describe the fabrication process and present force and displacement results for a double-membrane antagonistic actuator. In this structure controlled prestrain is applied by the simple process of pressing together two printed actuator halves. The development of 3D printable soft actuators will have a large impact on many application areas including engineering, medicine and the emerging field of soft robotics.

Ionic Polymer Metal Composite (IPMC) materials are bending actuators that can achieve large tip displacements at voltages less than 10V, but with low force output. Their advantages over traditional actuators include very low mass and size; flexibility; direct conversion of electricity to mechanical energy; biocompatibility; and the potential to build integrated sensing/actuation devices, using their inherent sensing properties. It therefore makes sense to pursue them as a replacement to traditional actuators where the lack of force is less significant, such as micro-robotics; bio-mimetics; medical robotics; and non-contact applications such as positioning of sensors. However, little research has been carried out on using them to drive mechanisms such as the rotary joints. This research explores the potential for applying IPMC to driving a single degree-of-freedom rotary mechanism, for a small-force robotic manipulator or positioning system. Practical issues such as adequate force output and friction are identified and tackled in the development of the mechanical apparatus, to study the feasibility of the actuator once attached to the mechanism. Rigid extensions are then applied to the tip of the IPMC, as well as doubling- and tripling the actuators in a stack to increase force output. Finally, feasibility of the entire concept is considered by comparing the maximum achievable forces and combining the actuator with the mechanism. It is concluded that while the actuator is capable of moving the mechanism, it is non-repeatable and does not achieve a level that allows feedback control to be applied.

Dielectric elastomer (DE) membranes are one of the most promising transducers for developing in situ sensors for the vasculature. It is widely accepted that diseased arteries at various stages have a unique constitutive response. This means that the output of an in situ artery sensor would have distinct profiles corresponding to various stages of unhealth. An in situ sensor can potentially allow access to information about the mechanical state of the artery that is not currently available. Furthermore, the potential to combine the functions of providing structural support (stent) and monitoring the mechanical state (sensor) is truly unique (multifunctionality). Traditional sensors such as strain gages and piezoelectric sensors are stiff and fail at low strains (<1%) whereas some dielectric elastomers are viable at strains up to and even surpassing 100%. Investigating the electromechanical response of a deformable tube sensor sandwiched between a pulsating pressure source and a nonlinear elastic distensible thick wall has not been attempted before now. The successful development of a multiphysics model that correlates the electrical output of a pulsatile membrane sensor to its state of strain would be a significant breakthrough in medical diagnostics. The artery is modeled numerically and represented theoretically as a fiber reinforced tubular membrane subject to a pulsating pressure signal. In this paper, the fundamental mechanics associated with electromechanical coupling during dynamic finite deformations of DEs is derived. A continuum model for the dynamic response of tubular dielectric elastomer membranes configured for sensing is presented.

The dielectric constant (ε) of a polymer can significantly be increased by blending it with conducting fillers. Given our interest in developing highly efficient and long-lasting actuators for muscle replacement, we set out to explore all key issues which could help to reduce the required voltage and at the same time ensure long term stability. The presentation describes experiments which prove that the water content in carboxylic acid-decorated phthalocyanines (Pcs), commonly falsely referred to oligo-Pcs, is a critical factor determining the absolute value of ε. Several publications on ε values of these oligo-Pcs led to contradicting conclusions because the effect of water was not sufficiently considered. The water content is relevant because o-Pcs are often used as fillers to increase ε of polymer matrices. This presentation also describes an experimental evaluation on whether or not as-prepared polyaniline (PANI) and poly(divinyl benzene)- encapsulated (PDVB) PANI can be reasonably used as high ε fillers in matrix materials. For this purpose several blends with polystyrene-polybutadiene block copolymer gels (PS-b-PB) and polydimethyl siloxane (PDMS) were prepared and their dielectric properties investigated. The former part of this presentation has in part already been published (D. M. Opris et al. Chem. Mater. 20(21), 6889-6896, 2008), the latter is completely new.

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). Recently Akle and Leo[1] reported extensional actuation in ionic polymer transducers. In this study, extensional IPTs are characterized under forced and free displacement boundary condition as a function of transducer architecture. The electrode thickness is varied from 10 μm up to 40 μm while three extensional actuators with Lithium, Cesium, and tetraethylammonium (TEA) mobile cations are characterized. Three fixtures are built in order to characterize the extensional actuation response. The first fixture measures the free displacement of an IPT sample sandwiched between two aluminum plates glued using the electrically conductive silver paste. In the second fixture a spring is compressed against the test sample with variable amounts to generate different levels of pre-stress and prevents the bending of the IPT. In the third fixture dead weights are placed on top of the sample in order to prevent bending. In the spring loaded fixture a thermocouple is placed in the proximity of the actuator and temperature is measured. The different transducers are characterized using a step voltage input and an alternating current (AC) sine wave input. The step input resulted in a logarithmic rise like displacement curve, while the low frequency (<0.1 Hz) AC excitation generated a sine wave displacement response with a strong first harmonic. The high frequency AC excitation generated a response similar to that of the step input. Comparing the measured temperature for step and AC response demonstrated that the sample is heating up when exited with a high frequency signal; which is leading to the expansion of the sample. Initial experimental results demonstrate a strong correlation between electrode architecture and the peak strain response. Strains on the order of 2% are observed with air stable ionic liquid based transducers. A correlation between the strain and charge buildup in the polymer is also characterized. Cesium (Cs) mobile cation outperformed all other tested mobile charges, while Potassium displaced the least. Keywords: Ionic Polymers, Transducer, Actuator, Electroactive Polymer, Extensional Actuator.

Dielectric elastomer actuators have attracted a great deal of attention thanks to their remarkably large actuation strain and energy density. Several different design concepts and configurations have been fabricated for many proposed applications. However, high rates of failure and short lifetime caused by dielectric breakdown have prevented their use in commercial applications. Employing single-walled carbon nanotube electrodes of tens of nanometer thickness and a coating of dielectric oil on the electrode surface, the actuators can be operated continuously at larger than 150% area strain for longer than 1500 minutes without terminal failure. As a comparison, under the same test conditions, actuators with carbon grease electrodes can be driven for less than 60 minutes before terminal failure. It has been demonstrated that the carbon nanotube electrodes endow the actuators with the ability to self-heal following localized dielectric failure, which should make them more amenable to practical applications.

Dielectric Elastomer (DE) transducers are essentially compliant capacitors fabricated from highly flexible materials that can be used as sensors, actuators and generators. The energy density of DE is proportional to their dielectric constant (ε_r), therefore an understanding of the dielectric constant and how it can be influenced by the stretch state of the material is required to predict or optimize DE device behavior. DE often operate in a stretched state. Wissler and Mazza, Kofod et al., and Choi et al. all measured an ε_r of approximately 4.7 for virgin VHB, but their results for prestretched DE showed that the dielectric constant decayed to varying degrees. Ma and Cross measured a dielectric constant of 6 for the same material with no mention of prestretch. In an attempt to resolve this discrepancy, ε_r measurements were performed on parallel plate capacitors consisting of virgin and stretched VHB4905 tape electroded with either gold sputtered coatings or Nyogel 756G carbon grease. For an unstretched VHB tape, an ε_r of 4.5 was measured with both electrode types, but the measured ε_r of equibiaxially stretched carbon specimens was lower by between 10 to 15%. The dielectric constant of VHB under high fields was assessed using blocked force measurements from a dielectric elastomer actuator. Dielectric constants ranging from 4.6-6 for stretched VHB were calculated using the blocked force tests. Figure of merits for DE generators and actuators that incorporate their nonlinear behavior were used to assess the sensitivity of these systems to the dielectric constant.

In principle EAP technology could potentially replace common motion-generating mechanisms in positioning, valve control, pump and sensor applications, where designers are seeking quieter, power efficient devices to replace conventional electrical motors and drive trains. Their use as artificial muscles is of special interest due to their similar properties in terms of stress and strain, energy and power densities or efficiency. A broad application of dielectric elastomer actuators (DEA) is limited by the high voltage necessary to drive such devices. The development of novel elastomers offering better intrinsic electromechanical properties is one way to solve the problem. We prepared composites from cross-linked silicone elastomers or thermoplastic elastomers (TPE) by blending them with organic fillers exhibiting a high dielectric constant. Well characterized monomeric phthalocyanines and modified doped polyaniline (PANI) were used as filler materials. In addition, blends of TPE and an inorganic filler material PZT were characterized as well. We studied the influence of the filler materials onto the mechanical and electromechanical properties of the resulting mixtures. A hundredfold increase of the dielectric constant was already observed for blends of an olefin based thermoplastic elastomer and PANI.

Dielectric Electro-Active Polymer (DEAP) technology has reached a level of maturity that makes it possible to fabricate reliable devices, which can be implemented in various industrial applications. Danfoss PolyPower has established scalable industrial manufacturing processes to enable commercialization of PolyPower film and actuators. The new series of DEAP actuators is based on the design of core-free rolled push actuators or folded pull actuators, by rolling or folding of long length of electro active material. The manufacturing processes involve roll-to-roll coating of elastomer mixtures to form endless micro-structured elastomer film/web, roll-to-roll vacuum deposition (PVD) of electrode material onto the micro-structured elastomer film, and roll-to-roll lamination and winding of tailored Pull and Push DEAP elements, also called InLastor. The paper will describe the processing steps and the scalable pilot production set up having capability of manufacturing kilometres of DEAP material per week.

Novel linear electromechanical actuators based on nanoporous TiC-derived carbons were prepared and studied. Traditionally, thin membranes containing mobile ions are used for bending actuators. We describe a linear actuator which consists of carbon material thin film and an ionic liquid. The thin film is made from nanoporous TiC-derived carbon powder and polytetrafluoroethylene (PTFE) as a binder agent. The working mechanism of the actuators is based on the interactions between the high-surface-area carbide-derived carbon (CDC) and the ions of the electrolyte. These actuators are able to generate linear actuation of about 1% from their thickness under voltages less than 3 V. The motion starts already at 0.8V and the magnitude of actuation depends on the electrical charge stored by the device. Two different types of electrolyte were used: 1) Ionic liquid (EMITf) and 2) Tetra-alcyl-ammonium salt in propylene carbonate (PC) solution. The actuators with ionic liquid have 60% higher movement. The electromechanical parameters of the actuators were studied by using cyclic voltammetry and electrochemical impedance spectroscopy methods.

Traditional ionic polymer/conductor network composite (IPCNC) electromechanical actuators exhibit low actuation speed and efficiency. In order to improve these parameters while still maintaining low voltage operation, we investigated IPCNC with a range of composite layer (active layer) and middle ionomer layer (passive layer) thicknesses. We show that it is the slow ion transport in the porous composite electrode layer that limits the actuation speed of IPCNCs. By reducing the thickness of the composite electrode layers, both the actuation speed and efficiency can be improved. Moreover, we show that the IPCNC actuator speed and efficiency are intimately related to the morphology of the composite electrode layer and the conductor network composites fabricated by ionic self-assembled layer-by-layer (LBL) exhibit higher strain response compared with that from the traditional IPCNC. For example, LBL composites show very high intrinsic strain of about 7%. Detailed device analysis points out directions of further improvement of these actuators.

The application of stimuli-responsive or smart cross-linked gels in chemical sensors is based on their ability to a phase transition under the influence of external excitations (temperature, pH, concentration of additives in water). The external stimulus lowers the energy barrier between two possible gel states: a stable state (shrunk gel) and a metastable state (swollen gel), and thereby makes possible the gel transition into the swollen state. The amount of the solvent absorbed due to the external stimulus has been modeled and calculated taking into account the polymer parameters (concentrations of the hydrophilic, hydrophobic, ionisable and ionised groups as well as polymer cross-linking degree) and the solution parameters (analyte concentration, ionic strength, viscosity as well as temperature and temperature change rate). Combining a smart hydrogel and a micro fabricated pressure sensor chip allows to continuously monitor the analytedependent swelling of a hydrogel and hence the analyte concentration in ambient aqueous solutions. The sensitivity of hydrogels with regard to the concentration of such additives as H+-ions (pH sensor), transition-metal ions and salts in water was experimentally and numerically investigated at different temperatures. It has been demonstrated that the sensor's sensitivity depends on the polymer composition as well as on the polymer cross-linking degree. A higher sensitivity was observed for polyelectrolyte hydrogels with higher concentrations of ionisable groups. The long-term measurements have shown that the lifetime of piezoresistive chemical sensors can be prolonged up to several years provided that specific operation and storage conditions are fulfilled.

The bending actuation of IPMCs is caused by the electrochemical reactions under imposed electric fields. The bending properties of the IPMC actuators as well as the sensitivity of IPMC sensors depend on the several particular impedances of the material, e.g. the conductivity of the electrodes, the capacitance of the ionomer, etc. The variation of the shape of the IPMCs causes the variations of those impedances and, therefore, leads to changes in their behavior. This effect is important in understanding the behavior of IPMC devices and could be exploited to obtain the feedback signal from them. This paper presents the results of the measurements of variations of the impedances of the surface electrodes as well as the IPMC devices in full during the course of their bending depending on the curvature of the device. The electrochemical analyses, including voltammetry and electrochemical impedance spectroscopy were carried out with two different IPMC materials. We show that the dynamical mechanical properties of the bending IPMC device and the particular impedances are correlated.

This paper aims to introduce newly developed Ionic Polymer-metal Composites (opto-IPMCs) targeting optical applications. The thin optical film of ZnO was deposited on IPMC by an electroless deposition method. This ZnO/Pt IPMC demonstrates photoluminescence (PL) quenching phenomenon, which is reduction in PL intensity (PLI) with an increase in applied electric fields. The crystal structure, morphology and atomic compositions of the resulting ZnO incorporated IPMCs were proved by X-ray diffraction, scanning electron microscopy, and the energy dispersive X-ray spectroscopy, respectively. We observed that ZnO incorporated IPMCs show stable and large displacement under a square current pulse. Also, the electro-optical responses of the manufactured opto-IPMCs were characterized by the PL spectra. The working range of the newly developed electro-optical system was measured to be within the 375-475 nm wavelength.

In this study, we introduce a newly developed Ionic Polymer-Metal Composite (IPMC) family that is manufactured using a novel ionic exchange membrane-a randomly sulfonated fluoropoly(ether amide) (TFIPA-90)-as the base material. The thermal behavior and mechanical properties of the ionic polymer were probed by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). Electrochemical properties and the actuation performance of the TFIPA-90 based IPMCs were also investigated in this study. The stiffness of the TFIPA polymer was significantly higher than that of Nafion® and much noted at high temperatures (>100 oC). The thermal behavior of the TFIPA polymer also showed better stability than Nafion^(R) at high temperatures due to the more rigid chemical structure of the ionomer. As an actuator, a new IPMC prepared from TFIPA-90 showed improved performance with rapid response time to the electric field and a large bending displacement. The TFIPA-based IPMC may be useful for microwave-driven robotic applications.

Materials that exhibit negative refraction demonstrate physical phenomena that may be used for novel applications. This work serves to evaluate the possibility of hyperbolic focusing due to an indefinite anisotropic permittivity tensor. Two single-loop antennas were used to approximately achieve a transverse magnetic (TM) point source and detector. Using an Agilent 8510C Vector Network Analyzer (VNA), the frequency spectrum was scanned between 7 and 9 GHz. Relative gain or loss measurements were taken at equal spatial steps around the center of the sample. A scanning robot allowed for the automatic scanning of the space behind the sample in the x, y, and z directions, to establish the focusing patterns, and to compare the signal amplitudes in the presence and absence of the sample. The robot was controlled using LabVIEW, which also collected the data from the VNA and passed it to Matlab for processing. A soft focusing spot was observed when the antennas were placed in a symmetric configuration with respect to the sample. These results suggest a method of focusing electromagnetic waves using negative refraction in indefinite materials.

The electro-active behavior of ionic polymer gel was modeled and the optimum condition of decision parameters that maximize the deflection of gel was investigated. An actuation model characterizing the bending deformation of polymer gel under electric field was proposed considering the chemo-electro-mechanical parameters. In the modeling, swelling or shrinking phenomenon due to the difference of concentration at the boundary between the gel and solution was considered first before the electric field is applied. Then, bending deformation under the concentration difference of ions was calculated. Differential osmotic pressure at the boundary of gel and solution determine the degree of swelling or shrinking of gel. From this actuation behavior, strain or deformation of gel is calculated. To find the optimum conditions for the deformation of gel, a non-linear constrained optimization model was proposed, where the equation for bending deflection of gel is used as the objective function and the relationship among the decision variables and the range of the variables are used as constraints. In the optimization model, electric voltage, thickness of gel, concentration of polyion in the gel, ion concentration in the solution and degree of cross-linking in gel were considered as decision variables. The predictions by the proposed model were compared with experimental data.

Recently, cellulose has been discovered as a smart material that can be used as sensors and actuators. This newly discovered material is termed as electro-active paper (EAPap) that has merits in terms of lightweight, flexible, dryness, biodegradable, biocompatible, easy to chemically modify, cheap and abundance. The actuation principle of cellulose EAPap bending actuator is known to be a combination of piezoelectric effect and ion migration effect. This paper presents further investigation of cellulose EAPap for its possibilities in biomimetic actuator, sensor, MEMS, acoustic devices and others. Biomimetic actuator is made with cellulose EAPap by fabricating rectifying antenna (rectenna) array on it. Cellulose EAPap material is customized to satisfy the material requirement for actuators and other devices. The material improvement all about cellulose EAPap is introduced. To fabricate the rectenna array, micro patterning of metallic layer in conjunction with Schottky diode fabrication on the cellulose was made. The Schottky diode fabrication allows possibility of thin film transistor fabricated on a cellulose paper. Microwave power transmission is demonstrated by using rectenna arrays, which can be used for many applications. Some of the device fabrication along with brief demonstrations is illustrated.

Ionic polymer transducers (IPT) are a class of devices that leverage electroactive polymers (EAP), specifically electrolyte-swollen ionomeric membranes, to perform energy conversions. Energy transformation from input to output is referred to as transduction and occurs between the electrical and mechanical domains. The present study expands on IPT investigations with a novel series of sulfonated polysulfones (sBPS), with specific interest in the effect of polymer topology on actuator performance. A hydrophilic ionic liquid was combined with a series of sBPS through a casting method to create hydrated membranes that contained target uptakes (f) of the diluent. The ionic liquid's hydrophilic, yet organic nature raised the issue of its degree of compatibility and miscibility with the microphase separated domains of the host ionomeric membrane. Initial studies of the ionomer - ionic liquid morphology were performed with synchrotron small angle X-ray scattering (SAXS). The effective plasticization of the membranes was identified with dynamic mechanical analysis (DMA) in terms of varied storage modulus and thermal transitions with ionic liquid uptake. Electrical impedance spectroscopy (EIS) was employed to quantify the changes in ionic conductivity for each sBPS ionomer across a range of uptake. Combined results from these techniques implied that the presence of large amounts of ionic liquid swelled the hydrophilic domains of the ionomer and greatly increased the ionic conductivity. Decreases in storage modulus and the glass transition temperature were proportional to one another but of a lesser magnitude than changes in conductivity. The present range of ionic liquid uptake for sBPS was sufficient to identify the critical uptake (f_c) for three of the four ionomers in the series. Future work to construct IPTs with these components will use the critical uptake as a minimum allowable content of ionic liquid to optimize the balance of electrical and mechanical properties for the device components.

Environmentally responsive or smart hydrogels show a volume phase transition due to changes of external stimuli such as pH or ionic strength of an ambient solution. Thus, they are able to convert reversibly chemical energy into mechanical energy and therefore they are suitable as sensitive material to be integrated in biochemical microsensors and MEMS devices. In this work, micro fabricated silicon pressure sensor chips with integrated piezoresistors were used as transducers for the conversion of mechanical work into an appropriate electrical output signal due to the deflection of a thin silicon bending plate. Within this work two different sensor designs have been studied. The biocompatible poly(hydroxypropyl methacrylate-N,N-dimethylaminoethyl methacrylate-tetra-ethyleneglycol dimethacrylate) (HPMADMA- TEGDMA) was used as an environmental-sensitive element in piezoresistive biochemical sensors. This polyelectrolytic hydrogel shows a very sharp volume phase transition at pH values below about 7.4 which is in the range of the physiological pH. The sensor's characteristic response was measured in-vitro for changes in pH of PBS buffer solution at fixed ionic strength. The experimental data was applied to the Hill equation and the sensor sensitivity as a function of pH was calculated out of it. The time-dependent sensor response was measured for small changes in pH, whereas different time constants have been observed. The same sensor principal was used for sensing the ionic strength. The time-dependent electrical output signal of both sensors was measured for variations in ionic strength at fixed pH value using PBS buffer solution. Both sensor types showed an asymmetric swelling behavior between the swelling and the deswelling cycle as well as different time constants, which was attributed to the different nature of mechanical hydrogel confinement inside the sensor.

Actuators based on carbon nanotubes (CNT) have the potential to generate high forces at very low voltages. The density of the raw material is just 1330 kg/m3, which makes them well applicable for lightweight applications. Moreover, active strains of up to 1% can be achieved - due to the CNTs dimensional changes on charge injection. Therefore the nanotubes have to be arranged and electrically wired like electrodes of a capacitor. In previous works the system's response of the Nanotubes comprising a liquid electrolyte was studied in detail. The major challenge is to repeat such experiments with solid electrolytes, which is a prerequisite for structural integration. In this paper a method is proposed which makes sure the expansion is not based on thermal expansion. This is done by analysing the electrical system response. As thermal expansion is dominated by ohmic resistance the CNT based actuators show a strong capacitive behavior. This behavior is referable to the constitution of the electrochemical double layer around the nanotubes, which causes the tubes to expand. Also a novel test setup is described, which guarantees that the displacement which is measured will not be caused by bending of a bimorph but due to expansion of a single layer of nanotubes. This paper also presents experimental results demonstrating both, the method of electrical characterization of CNT based actuators with implemented solid electrolytes and the novel test setup which is used to measure the needed data. The actuators which were characterized are hybrids of CNT and the solid electrolyte NAFION which is supplying the ions needed to constitute the electrochemical double layer. The manufacturing, processing of these actuators and also some first experimental results are shown. Unfortunately, the results are not as clear as those for liquid electrolytes, which depend on the hybrid character of the analyzed devices. In the liquid electrolyte based case the CNTs are the only source of stiffness, whereas in the solid electrolyte case electrodes and electrolyte contribute to the overall stiffness and damping as well. Since the introduction of solid electrolytes is a major stumbling block in the development of such actuators, this work is of particular importance.

Conducting polymers have sparked much research interest due to their unique ability to be electrically stimulated. However, these polymers are very brittle and have poor mechanical properties. In order to improve upon its structural integrity, it can be blended with other host polymers that have better mechanical properties. These blended composites would then possess the benefits of conductive properties while having sufficient mechanical properties to be more suitable for practical applications. Polypyrrole-polylactic acid blends were processed using chemical oxidative polymerization and compression molding, followed by gas foaming and saturation techniques to create porous structures. Characterization of these porous blends included its physical, thermal, and mechanical properties.

Ionic polymer-metal composites (IPMCs) form an important category of electroactive polymers. In this paper, a nonlinear, physics-based model is proposed for IPMC actuators. A key component in the proposed model is the nonlinear capacitance of IPMC, demonstrated by the nonlinear relationship between an applied step voltage and the induced charge. A nonlinear partial differential equation (PDE) is fully considered in analytical derivation of the capacitance of IPMC. The nonlinear capacitance is incorporated into a circuit model, which includes additionally the pseudo capacitance, the ion diffusion resistance, and the nonlinear DC resistance of the polymer. The model is verified in experiments.

In this paper, a finite element-based dynamic model is developed for a miniature underwater vehicle propelled by Ionic Polymer Metal Composite (IPMC) actuator. The proposed approach describes the electro-mechanical actuation using a large deflection beam model. Hydrodynamic forces including frictional effects are also considered. The hydrodynamic force coefficients are identified based on the results of extensive computational fluid dynamics (CFD) simulations. Experimental results have shown that the proposed model predicts the motion of the vehicle accurately for different actuation signals. The proposed model can lead to the development of an underwater vehicle, which can achieve complex set of maneuvers. It can also contribute to developing both open and closed-loop control algorithms for the robotic vehicles.

This work investigates the characterization and modelling of hysteresis in a core-free dielectric electro-active polymer (EAP) tubular actuator. The overall hysteresis effect of the voltage driven system comprises the inherent hysteresis of the fabricated tubular actuator plus a time lag introduced by the associated power supply when charging and discharging the actuator. Specifically the dynamic asymmetric hysteretic model of the voltage driven tubular actuator is decomposed into two models in series, comprising the nonlinear static voltage-strain characteristic of the actuator and an approximate symmetric hysteretic characteristic. The Bouc-Wen model approach is popular in engineering because of its simple interpretation as a nonlinear black-box model, the relatively low number of parameters needed to describe it, and the availability of both optimization and least squares estimation approaches to identify model parameters from experimental data. A disadvantage of the Bouc-Wen modelling approach is that it cannot accurately model asymmetric hysteresis behaviour. The use of the decomposition approach allows the Bouc-Wen model to be used to describe the approximate symmetric hysteretic characteristic. The model parameters are identified using an evolutionary computational algorithm - particle swarm optimization (PSO). PSO is an evolutionary based optimization approach that has been shown to be superior to genetic algorithms.

Dielectric elastomers (DE) are the most promising electroactive polymer materials capable of being applied in smart actuators. When the DE film sandwiched between two compliant electrodes is applied high electric field, due to the electrostatic force between two electrodes, the film expands in-plane and contracts out-of-plane such that its thickness becomes thinner. The thinner thickness results in higher electric field which inversely squeezes the film again. This positive feedback induces a mode of instability, known as electromechanical instability or pull-in instability. When the electric field exceeds certain critical value, the DE film collapses. In this paper, the elastic strain energy function with two material constants is applied to analyze the stability of dielectric elastomers, which facilitates to understand fully Suo's nonlinear theory. The results verify again the truth of this theory and exploit larger application spectrum. The method is capable of analyzing the stability of different dielectric materials with different values of k and the result can be useful on design of the dielectric elastomer actuator.

In this paper, we analyze the effect of electrode surface roughness on the capacitance of Ionic Polymer Metal Composites (IPMCs). We use the linearized Poisson-Nernst-Planck (PNP) model to describe the steady-state spatial distribution of the electric potential and counterion concentration in the polymer region. We account for the electrode surface roughness by solving the PNP model in a three-dimensional region, whose planar dimensions are infinite and whose transverse dimension is varying in the neighborhood of a nominal constant thickness. In this framework, the electrode roughness is described by a zero-mean function whose key-features, such as spatial correlation and peak-to-peak variation, can be potentially inferred by IPMC microscopy. We use the method of asymptotic expansions to determine a second-order accurate solution of the PNP model in terms of the statistical properties of the electrode surface. Further, we establish a handleable closed-form expression for the IPMC capacitance that elucidates the interplay among the IPMC nominal dimensions, the statistical properties of the electrode surface, and the Debye screening length. We specialize our findings to isotropic surface roughness models, including random and fractal roughness. We validate our theoretical findings through extensive experimental work on Nafion-based IPMCs.

In this paper, a comprehensive actuation model for IPMC material is presented. The charge motion within the polyelectrolyte membrane under a dynamic electric potential is first investigated. Based on the Nernst-Planck equation, the Poisson's equation and the continuity equation, the charge redistribution under dynamic electric potential is formulated. Subsequently, the dynamic ion-ion interactions within the polyelectrolyte membrane clusters are presented. By analyzing the volumetric changes of the membrane clusters due to the electric field induced stresses and the elastic stresses in the backbones of the membrane, the bending strain and stress are determined. Finally, the bending moment expression due to the applied electric potential is obtained. By using this bending moment expression, the vibrations of a cantilevered IPMC sample under different electric excitations are calculated. The actuation characteristics of the IPMC are then discussed with comparison of experimental observations.

As a major human sensory function, the implementation of the tactile sensation for the human-machine interface has been one of the core research interests for long time. In this research, tactile display devices based on dielectric elastomer are introduced among the works recently done by ourselves. Using dielectric elastomer for the construction of the tactile interface, it can provide stimulation on the human skin without any additional electromechanical transmission. Softness and flexibility of the device structure, ease of fabrication, possibility for miniaturization, and cost effectiveness are the representative benefits of the presented devices. Especially, the device application is open to a wide variety of purposes since the flexible structure offers excellent adaptability to any contour of the human body as well as the other objects. In this paper, the design of the interfaces is briefly explained and several examples of implementation are introduced.

Tactile perception is the human sensation of surface textures through the vibrations generated by stroking a finger over the surface. The skin responds to several distributed physical quantities. Perhaps the most important are high-frequency vibrations, pressure distributions (static shape) and thermal properties. The integration of tactile displays in man-machine interfaces promises a more intuitive handling. For this reason many tactile displays are developed using different technologies. We present several state-of-the-art tactile displays based on different types of dielectric elastomer actuators to clarify the advantages of our matrix display based on multilayer technology. Using this technology perpendicular and hexagonal arrays of actuator elements (tactile stimulators) can be integrated into a PDMS substrate. Element diameters down to 1 mm allow stimuli at the range of the human two-point-discrimination threshold. Driving the elements by column and row addressing enables various stimulation patterns with a reduced number of feeding lines. The transient analysis determines charging times of the capacitive actuators depending on actuator geometry and material parameters. This is very important to ensure an adequate dynamic characteristic of the actuators to stimulate the human skin by vibrations. The suitability of multilayer dielectric elastomer actuators for actuation in tactile displays has been determined. Beside the realization of a static tactile display - where multilayer DEA are integrated as drives for movable contact pins - we focus on the direct use of DEA as a vibrotactile display. Finally, we present the scenario and achieved results of a recognition threshold test. Even relative low voltages in the range of 800 V generate vibrations with 100% recognition ratio within the group of participants. Furthermore, the frequency dependent characteristic of the determined recognition threshold confirms with established literature.

Ras Labs, LLC, is committed to producing a variety of electroactive smart materials and actuators that are strong, resilient, and respond quickly and repeatedly to electrical stimuli over a wide temperature range. Cryogenic and high temperature experiments (4.22 K to 137°C) were performed on the contractile electroactive materials developed by Ras Labs with very favorable results. One of the biggest challenges in developing these actuators, however, is the interface between the embedded electrodes and the electroactive material because of the pronounced movement of the electroactive material. If the electroactive material contracts very quickly, the electrode is often left behind and thus becomes detached. Preliminary experiments explored the bonding between these electroactive materials with plasma treated metals provided by the Department of Energy's Princeton Plasma Physics Laboratory (PPPL) at Princeton University. The results were encouraging, with much better bond strengths in the plasma treated metals compared to untreated controls. Plasma treatments, and other treatments to non-corrosive metal leads, were further investigated in order to improve the attachment of the embedded electrodes to the electroactive material. Surface water drop contact angle tests, modified T-peel testing, and mechanical testing were used to test metal surfaces and metal-polymer interfaces for stainless steel and titanium. X-ray photoelectron spectroscopy (XPS) was used to determine the atomic surface composition of stainless steel and titanium after various plasma treatments. Mode of failure after T-peel testing and mechanical testing was determined using scanning electron microscopy (SEM) and stereo microscopy. Nitrogen plasma treatment of titanium produced a strong metal-polymer interface; however, oxygen plasma treatment of both stainless steel and titanium produced even stronger metal-polymer interfaces. Plasma treatment of the electrodes allows for the embedded electrodes and the electroactive material of the actuator to work and move as a unit, with no detachment, by significantly improving the metal-polymer interface.

DEAP Actuator structures are being developed and optimized with focus on high volume automated manufacturing techniques and processes. New core-free and self-supporting structures are capable of providing PUSH forces without external mechanical tension mechanisms or film pre-strain. Fundamental actuator design and construction principles are presented. A simple quasi-static model governing behaviour is presented and actual results from this new class of push actuator devices are compared to modelled behaviour. These actuators have the capability of modest stroke and high actuation forces. Actuators can be easily scaled to fit the application based upon physical size and force-stroke relationship.

An unmanned underwater vehicle (UUV) was designed inspired by the form and functionality of a Jellyfish. These natural organisms were chosen as bio-inspiration for a multitude of reasons including: efficiency of locomotion, lack of natural predators, proper form and shape to incorporate payload, and varying range of sizes. The structure consists of a hub body surrounded by bell segments and microcontroller based drive system. The locomotion of UUV was achieved by shape memory alloy "Biometal Fiber" actuation which possesses large strain and blocking force with adequate response time. The main criterion in design of UUV was the use of low-profile shape memory alloy actuators which act as artificial muscles. In this manuscript, we discuss the design of two Jellyfish prototypes and present experimental results illustrating the performance and power consumption.

We describe a low profile and lightweight membrane rotary motor based on the dielectric elastomer actuator (DEA). In this motor phased actuation of electroded sectors of the motor membrane imparts orbital motion to a central gear that meshes with the rotor. Two motors were fabricated: a three phase and four phase with three electroded sectors (120°/sector) and four sectors (90°/sector) respectively. Square segments of 3M VHB4905 tape were stretched equibiaxially to 16 times their original area and each was attached to a rigid circular frame. Electroded sectors were actuated with square wave voltages up to 2.5kV. Torque/power characteristics were measured. Contactless orbiter displacements, measured with the rotor removed, were compared with simulation data calculated using a finite element model. A measured specific power of approximately 8mW/g (based on the DEA membrane weight), on one motor compares well with another motor technology. When the mass of the frame was included a peak specific power of 0.022mW/g was calculated. We expect that motor performance can be substantially improved by using a multilayer DEA configuration, enabling the delivery of direct drive high torques at low speeds for a range of applications. The motor is inherently scalable, flexible, flat, silent in operation, amenable to deposition-based manufacturing approaches, and uses relatively inexpensive materials.

The effect of cycling on charge-storage, actuation and sensing behavior of a polypyrrole is studied, having its application for an electroactive catheter in mind. It is shown that the electrochemical capacitance of a polypyrrole film decreases by about 15 % over the course of 100 cycles, while the per cycle rate of this decrease drops by 75 % between the first and the last ten cycles, implying that a steady-state value may exist. The decrease in capacitance is shown to have a significant effect on actuation strain. In order to achieve a more constant capacitance and more robust actuation performance, it is proposed to pre-cycle the potential of the film to exhaust the effect of processes that contribute to the decrease in capacitance and allow it to reach a more constant value. The ability of a polypyrrole film to generate currents corresponding to applied external load during actuation is verified and the cycle life time of such a sensor is studied. It is shown that after an initial decrease, the sensor current reaches a steady-state value as well, and maintains that value at least over 5600 cycles.

In this paper conducting polymer based active catheters are presented. Design considerations along with the promise and challenges associated with conducting polymer driven devices are discussed. A conducting polymer driven intravascular catheter is described briefly and its design challenges such as structural rigidity and angle of bending are studied. Then a detailed description of a polypyrrole based active catheter that is ultimately intended for in-vivo imaging applications will be presented. The active catheter contains an optical fibre and is designed to scan the fibre in two dimensions at a speed of 30 Hz to provide real time imaging. The preliminary design was realized by fabricating polypyrrole actuators on a commercially available catheter and patterning the polymer using laser machining technique. The initial device was tested at lower speeds and an image was taken using optical coherence tomography (OCT). The primary challenge to achieving an effective polypyrrole driven catheter for real time imaging is to demonstrate high speed actuation with reasonable liftetime. According to our model, electrochemical characteristics of the conducting polymer such as electronic conductivity, ionic conductivity and electrochemical strain need to be improved to achieve the desired catheter scanning speed.

The development of a multiline, refreshable Braille display will assist with the full inclusion and integration of blind people into society. The use of both polyvinylidene fluoride (PVDF) film planar bending mode actuators and silicone dielectric elastomer cylindrical tube actuators have been investigated for their potential use in a Braille cell. A liftoff process that allows for aggressive scaling of miniature bimorph actuators has been developed using standard semiconductor lithography techniques. The PVDF bimorphs have been demonstrated to provide enough displacement to raise a Braille dot using biases less than 1000V and operating at 10Hz. In addition, silicone tube actuators have also been demonstrated to achieve the necessary displacement, though requiring higher voltages. The choice of electrodes and prestrain conditions aimed at maximizing axial strain in tube actuators are discussed. Characterization techniques measuring actuation displacement and blocking forces appropriate for standard Braille cell specifications are presented. Finally, the integration of these materials into novel cell designs and the fabrication of a prototype Braille cell are discussed.

In this paper, a model is proposed for a biomimetic robotic fish propelled by an ionic polymer metal composite (IPMC) actuator with a rigid passive fin at the end. The model incorporates both IPMC actuation dynamics and the hydrodynamics, and predicts the steady-state speed of the robot under a periodic actuation voltage. Experimental results have shown that the proposed model can predict the fish motion for different tail dimensions. Since its parameters are expressed in terms of physical properties and geometric dimensions, the model is expected to be instrumental in optimal design of the robotic fish.

The positioning control of IPMC is generally considered difficult. Our previous study, however, clarifies that IPMC's position can be controlled by integral control if the residual deformation remains in the same side of the initial deformation. In this study, the effects of the positive counter ions and the negative ions on the deformation characteristics were examined. The direction of the residual strain was changed by the pH of the negative ion at around pH5.5 - pH6. If the pH is more alkaline, IPMC can be controlled its position. A mechanism of residual deformation is proposed.

Conjugated polymer actuators provide delicate solutions in biomimetic robotics and bio/micromanipulation. For these applications, it is highly desirable to have large deformation. Because linear elasticity theory is only valid when the strain is small, this poses significant challenges in the electromechanical modeling. In this paper, we use a nonlinear strain energy function to capture the stored elastic energy under actuation-induced swelling, which further allows us to compute the induced stress. Numerical method is used to obtain the deformation variables by solving the force and bending moment balance equations simultaneously. Experimental results for a trilayer conjugated polymer beam can be predicted by the proposed model better than the linear model. This proposed framework can also be applied to the analysis of large deformations of other electroactive polymers.

Large-strain electroactive polymer bending actuators may consist of two conductive polymer layers electropolymerized on opposing faces of a porous membrane core that facilitates ion migration and electrolyte storage. Although several studies have been devoted to the conditions of the polymerization process, far less effort has been devoted to the systematic selection of the core material and the impact of the core's cellular morphology on the resulting actuation characteristics. This study introduces our initial work towards elucidating the relationship between the material properties of the porous core and the underlying actuation mechanism by reviewing how the physical characteristics of the membrane core are intrinsically captured by existing conductive polymer actuator models. The electromechanical response of polypyrrole trilayer actuators having poly(vinylidene fluoride) and Nylon cores is also explored.

Toward the construction of the unified model of ionic polymer actuators, this paper discusses the system modeling with the electro-stress diffusion coupling theory. The theory can explain the differences of the relaxation phenomenon of polymer electrolytes with respect to the various counter ion species in the polymer. In addition to the mechanical system which employs a simple beam model, the electrical system and the electro-mechanical coupling systems are also represented by partial differential equations. The electrical system is modeled based on the non-uniform distributed circuit which represents the electrode roughness. The electro-mechanical coupling system is derived from the electro-stress diffusion coupling theory. The overall system is represented by a statespace equation with a feedback structure. The comparisons between the simulation result and the experimental result show the validity of the model.

Shape memory polymer (SMP) is a promising smart material, which is able to perform a large deformation upon applying an external stimulus, such as heat, light and moisture, etc. In recent years, many investigations have been advanced in thermo-responsive SMP actuation, and several novel actuations have been applied in SMP. In this paper, the mechanism and demonstration of three types of SMP actuations (infrared laser, physical swelling effect and electricity) are presented. These novel actuation approaches may help SMP to fully reach its potential application. Firstly, for the infrared laser-activated SMP, it is concerned about the drive of SMP by infrared light. The infrared laser, transmitted through the optical fiber embedded in the SMP matrix, was chosen to drive the SMP. The working frequency of infrared laser was installed in 3-4μm. Moreover, this paper presents a study on the effects of solution on the glass transition temperature (T_g). It shows that the hydrogen bonding of SMP was aroused by the absorbed solution that significantly reduces transition temperature of polymer. In this way, the shape memory effect (SME) can undergo solution-driven shape recovery. Finally, the actuation of two types of electro-active SMP composites filled with electrically conductive powders (carbon black, nickel powers) have been carried out, and the SMP composite can be driven by applying a relatively low voltage.

The electrical resistivity of a thermoset styrene-based shape-memory polymer (SMP) filled with Ni powders is investigated in this paper. We demonstrate a simple approach to improve the electrical conductivity 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 particles into a styrene-based SMP, the electrical resistivity is reduced. Furthermore, if these Ni particles are aligned into chains, by applying a low magnetic field on SMP/Ni solution and then drying to fix the conductive chains, the drop of electrical resistivity is more significant. Due to the improvement of electrical conductivity of the SMP composite, it is more suitable for Joule heat induced shape recovery.

Nanostructured organic materials derived from block copolymers solvated by block-selective solvents have shown considerable potential as versatile dielectric elastomers. These materials can easily be tuned to achieve the mechanical and electrical properties required for actuator applications. They are lightweight and attractive due to their facile processing, robust properties and reliable performance. Their superb actuation behavior is realized when they are used as dielectric materials under actuation conditions promoting Maxwell compression, which produces large mechanical displacements, coupling efficiencies, and energy densities. These properties generally improve when the material is subjected to mechanical pre-strain. In most cases, mechanical pre-strain is needed to safely achieve application of a desired electrical field. Requisite pre-strain generally necessitates additional overhead in terms of weight and space for the device, and promotes changes in mechanical properties. In this study a new electroactive nanostructured polymer (ENP) is prepared from a triblock copolymer and a nonvolatile block-selective solvent, and evaluated as an actuator candidate. The copolymer exhibits reasonably high actuation strains (up to 70 area%) at relatively low electric fields and energy densities up to 50 kJ/m³ without pre-strain. These performance metrics exceed those reported for conventional dielectric materials such as the VHB acrylic elastomer, as well as those of ENPs derived from styrenic triblock copolymers under no pre-strain.

A new type of polymeric actuator has been developed based on a micro-scale hydraulic mechanism, in which electroosmotic flow (EOF) is used to pump a fluid from one place to another in the device. This "nastic" actuator is in principle capable of producing both large displacements and high forces at reasonable speeds. Prototypes were fabricated from polydimethylsiloxane (PDMS) by micro-molding a fluid supply chamber, an expansion chamber, and connecting channels, and then topping this layer with a thin PDMS membrane. Upon applying a voltage across the two chambers, fluid flowed into the expansion reservoir, deflecting the membrane upward by hundreds of μm within a few seconds. The performance of these prototypes have been characterized in terms of deflection under load at various applied voltages, deflection vs. time upon input of a step potential, and repeatability. The performance of the actuator has been modeled, and the experimental and theoretical results are in reasonable agreement. The modeling work predicts that as the channel size is scaled down, the actuation stress will increase substantially, up to GPa for nanochannels, rivaling piezoelectrics and shape memory alloys but with much higher strain. Future applications of these actuators may include valves, shape-changing materials, and soft robotics.

Dielectric elastomers (DEs) are one particular type of electroactive polymers. The excellent features of merit possessed by dielectric elastomers make them the most performing materials which can be applied in many domains: biomimetics, aerospace, mechanics, medicals, etc. In order to maximize actuator performance, the dielectric elastomer actuators should have a high dielectric constant and high dielectric breakdown strength. In this paper, multi-walled carbon nanotube (MWNT) is used to develop a particulate composite based on silicone elastomer matrix, with dielectric permittivity improved. And the composite is designed to a new configuration of dielectric elastomer actuator to show electrically activated linear contractions. Prototype samples of this folded actuator, along with the fabrication and analysis is discussed here.

Dielectric elastomers are light weight, low-cost, and highly deformable smart materials widely in used as sensors and actuators. Compounding of silicone rubber with various fillers can enhance efficiency of smart materials. Effect of organically modified Montmorillonite (OMMT) nanoclay on improvement of dielectric properties and actuation stress was considered in this study. Room Temperature Vulcanized (RTV) silicone rubber was compound with 2% and 5% of OMMT by solution method and a composite film was cast. Dielectric measurements show enhancement of both dielectric permittivity and dielectric loss in these composites. Actuation stress for different composites was measured by using an in-house actuation set-up, which showed that actuation stress for a given electric field intensity is higher for composites than that for pristine silicone rubber. Furthermore, time dependent actuation response of the samples was evaluated. Dielectric properties of the composites were measured under AC electric fields, and results were compared with the reference silicone rubbers with no filler. Results shows increase in both storage and loss dielectric constants of base silicone rubber when it is compounded with OMMT.

The effects of dielectric constant and electric field strength on the deflection angle and the dielectrophoresis force of acrylic elastomers and styrene copolymers were investigated. The dielectrophoresis forces of six elastomers were determined in a vertical cantilever fixture by measuring the deflection distance under various electric field strengths. The forces were calculated from the non-linear deflection theory of the cantilever. As an electric field is applied, five elastomers, with the exception of SAR, deflect towards the anode side of the electrodes. For these elastomers, internal dipole moments are generated under electric field leading to the attractive force between the elastomers and the anode. SAR contains metal impurities (Cu and Zn) determined by EDX. Their presence introduces a repulsive force between the Cu²⁺ and Zn²⁺ ions and the aniodic electrode, leading to the bending towards the neutral electrode. The dielectrophoresis forces of the six elastomers generally increase with increasing electric field strength, and increase monotonically with the dielectric constants. AR71 (ε' = 6.33) has the lowest electrical yield point (75 V/mm) but it generates the highest force. On the other hand, SIS (ε' = 2.74) has the highest electrical yield point (400 V/mm) and it generates the lowest force.

A feasibility study into the appropriateness of using a laminated dielectric electro active polymer (DEAP) film, called PolyPower^TM, for energy scavenging purposes is reviewed in this work. The maximum strain in the film is limited to < 35% and the maximum applied voltage is currently limited to < 3000 V, strains and voltages much less than those applied to acrylics already utilised in DEAP-based energy harvesting applications. This work will examine the amount of electrical energy that can be produced using PolyPower^TM to provide insight into (a) the practicality of using the material for energy scavenging and (b) to highlight feasible scavenging applications. A test rig was designed and a series of experiments carried out to investigate energy scavenging using the DEAP material. Three different levels of initial mechanical strain, 5%, 10% and 15% were investigated with three different levels of maximum applied voltage during the charging stage, 1.2 kV, 1.5 kV and 1.8 kV. For each, of the nine, experiment the total amount of electrical energy available for scavenging was determined and results compared with a model of the energy scavenging cycle. The recovery of the scavenged electrical energy was not addressed in this work, though the relevant advantages and disadvantages of different types of continuous operation of the cycle are discussed.

Of the range of dielectric EAP-based actuators that currently exist those having a cylindrical configuration are perhaps the most important. Up until now the most popular tubular actuator designs have exploited the exceptional pre-strain performance of the acrylics VHB 2910 and VHB 2905. Unfortunately pre-stained acrylic film rolled tubular actuators with a spring core experience problems concerning reliability and life expectancy. Partly because of these problems research is beginning to be directed towards the design, fabrication and characterisation of core free tubular actuators. This work reviews the Voltage-Strain modeling of core free rolled actuators that are constructed using a dielectric electro active polymer film that employs smart electrode technology. Position response tests, whereby a step input of 1500 V was applied to each actuator, confirmed that time dependent strain influences the Voltage-Strain behaviour of the actuators. To represent the time dependent strain behaviour a creep effect model was combined with Pelrine's electromechanical model to provide a more accurate representation of the Voltage-Strain characteristics of the actuators.

In late years many kinds of home-use robot have been developed to assist elderly care and housework. Most of these robots are designed with conventional electromagnetic motors. For safety it is desirable to replace these electromagnetic motors with artificial muscle. However, an actuator for such a robot is required to have simple structure, low driving voltage, high stress generation, high durability, and operability in the air. No polymer actuator satisfying all these requirements has been realized yet. To meet these we took following two approaches focusing on conducting polymer actuators which can output high power in the air. (Approach 1) We have newly developed an actuator by multiply laminating ionic liquid infiltrated separators and polypyrrole films. Compared with conventional actuator that is driven in a bath of ionic liquid, the new actuator can greatly increase generated stress since the total sectional area is tremendously small. In our experiment, the new actuator consists of minimum unit with thickness of 128um and has work/weight ratio of 0.92J/kg by laminating 9 units in 0.5Hz driving condition. In addition, the driving experiment has shown a stable driving characteristic even for 10,000 cycles durability test. Furthermore, from our design consideration, it has been found that the work/weight ratio can be improved up to 8J/kg (1/8 of mammalian muscle of 64J/kg) in 0.1Hz by reducing the thickness of each unit to 30um. (Approach 2) In order to realize a simplified actuator structure in the air without sealing, we propose the use of ionic liquid gel. The actuation characteristic of suggested multilayered actuator using ionic liquid gel is simulated by computer. The result shows that performance degradation due to the use of ionic liquid gel is negligible small when ionic liquid gel with the elasticity of 3kPa or less is used. From above two results it is concluded that the proposed multilayerd actuator is promising for the future robotic applications because it has advantages of high work/weight ratio and in-the-air operation, in addition to advantages of conventional polymer actuators.

A recently introduced elective to the Master's of Science in Mechatronics program at Southern Denmark University, entitled 'Mechatronics: Design and Build' concentrates on some of the interdisciplinary aspects of Mechatronics Engineering. The 'Motion Control of Mechatronic Devices' is the main theme of this elective. Within this 'theme' the modelling, identification and compensation of nonlinear effects such as friction, stiction and hysteresis are considered. One of the most important components of the elective considers 'Smart Materials' and their use for actuation purposes. The theory, modelling and properties of piezoceramics. magneto- and electro- rheological fluids and dielectric electro active polymers (DEAP) are introduced in the 'Smart Materials' component. This paper initially reviews the laboratory experiments that have been developed for the dielectric electro active polymer section of the 'Mechatronics: Design and Build' elective. In lectures the students are introduced to the basic theory and fabrication of tubular actuators, that use DEAP material based on smart compliant electrode technology. In the laboratory the students to (a) carry out a series of experiments to characterise the tubular actuators, and (b) design a closed-loop position controller and test the performance of the controlled actuator for both step changes in desired position and periodic input reference signals. The last part of this contribution reviews some of the DEAP-based demonstration devices that been developed by Danfoss PolyPower A/S using their PolyPower^TM material which utilizes smart compliant electrode technology.

Ionic Polymer-Metal Composites (IPMCs) of EAP actuators is famous for its good property of response and durability. The performance of Ionic Polymer-Metal Composites (IPMCs) is an important issue which is affected by many factors. There are two factors for deciding the performance of IPMC. By treating anisotropic plasma etching process to 6 models of the IPMCs, enhanced experimental displacement and force results are obtained. Plasma patterning processes are executed by changing the groove and the land length of 6 patterns. The purpose of the present investigation is to find out the major factor which mainly affects the IPMC performance. Simulations using ANSYS have been executed to compare with the experimental results about the values and the tendency of data. Experimental and simulating data of the performances seem to have similar tendency. In the next part of the paper, we observed the other properties like capacitance, resistance and stiffness of 6 plasma patterned IPMCs. And we observed that the stiffness is the major factor which affects the performance of IPMCs. As we seen, our problem has been reduced to investigate about the property of stiffness. We suggest that the stiffness is largely changed mainly because of the different thickness of Platinum stacked of the groove and the land part which are produced by anisotropic plasma etching processes. And we understand that anisotropic plasma patterned IPMCs of better performance can be applied to various applications.

This paper describes a linear dynamic model of an elongated bending Electroactive Polymer (EAP) actuator applicable with deformations of any magnitude. The model formulates relation of a) voltage applied to the EAP sheet, b) current passing through the EAP sheet, c) force applied by the actuator and d) deformation of the actuator. In this model only the geometry of EAP piece and four empirical parameters of the EAP material: a) bending stiffness, b) electromechanical coupling term, c) electrical impedance and d) initial curvature are considered. The contribution of this paper is introducing a model that can be used to characterize the properties of different EAP materials and compare them. The advantage of the model is its simplicity and ability to provide insights in to the behavior of bending EAPs. Additionally, due to linearity of the model, the real-time control is feasible. Experiments, using Ionomeric Polymer-Metal Composite (IPMC) sheet from Environmental Robotics Inc., where carried out to verify the model. The experimental results confirm the model is valid.

Human intention recognition is becoming a key part of powered prosthetics research. With the advent of smart materials, the usefulness of powered prosthetics has increased. Correspondingly, there is a greater need for control technology. Electromyography (EMG) has previously been used to control myoelectric hands; however the approach to electrode placement has been speculative at best. Carpi, Raspopovic and De Rossi have shown that dielectric elastomer actuators (DEAs) can be controlled by a variety of human electrophysiological signals, including EMG. To control a DEA device with multiple degrees of freedom using EMG, multiple electrode sites are required. This paper presents an approach to control an array of DEAs using a series of electrodes and an optimized electrode data filtering scheme to maximize classification accuracy when differentiating between hand grasps. A silicon mould of a human forearm was created with an array of electrodes embedded within it. Data from each electrode site was recorded using the Universal Electrophysiological Mapping (UnEmap) system developed at the University of Auckland Bioengineering Institute for the amplification and filtering of multiple biopotential signals. The recorded data was then processed off-line, in order to calculate spatial gradients; this would determine which electrode sites would give the best bipolar readings. The spatial gradients were then compared to each other in order to find the optimal electrode sites. Several points in the extensor compartment of the forearm were found to be useful in recognizing grasping, while several points in the flexor compartment of the forearm were found to be useful in differentiating between grasps.

Ionic polymer-metal composite (IPMC) is an attractive actuator among many electro-active polymers. In order to improve the performance of IPMC actuator, an IPMC actuator with the patterned surface was proposed. It is named the patterned IPMC actuator. In order to make use of its maximum effect, it is needed to establish a valid mathematical model. Among many models of IPMC actuator, the grey box modeling proposed by Kanno et al. was suited to model the patterned IPMC actuator. In this paper, we applied the grey box model based on Kanno's model. Theoretical and experimental results demonstrate that the model is practical and effective enough in predicting the bending displacement partly.

Ionic polymer metal composites is the proposing material for applications, since it has many attractive qualities that are durability, aquatic, miniature and light-weighted. Especially, IPMC has extraordinary advantages that are large displacement at low driving voltage(~3V), low power consumption and simple structure. However, slow time response prevents IPMC from various applications. Since IPMC is generally used in simply-supported configuration, which has same characteristic with a cantilever beam, IPMC has natural frequency and it oscillates extremely at natural frequency. We propose new open loop control method based on frequency response, which is combined with conventional DC input. This method is experimentally tested and compared with result by conventional input.

Cellulose has been reported as a smart material that can be used as sensors and actuators. The cellulose smart material is termed as Electro-active paper (EAPap), which is made by regenerating cellulose. However, regeneration of cellulose resulted in reduced performance output of actuators at low humidity levels. To solve this drawback, EAPap bending actuators were made by activating wet cellulose films in three different room temperature ionic liquids BMIPF₆, BMICL and BMIBF₄. Results showed that the actuator performance was dependent on the type of anions in the ionic liquids and it was in the order of BF₄¯ > Cl¯ > PF₆¯. BMIBF₄ activated actuator showed the maximum displacement of 3.8 mm with low electrical power consumption at relatively low humidity level. Also, it found that, although size of PF₆¯ anion is larger than BF₄¯ anion it showed the low displacement output due to poor adsorption as indicated the FTIR analysis.

Ionic polymer-metal composites (IPMC), piezoelectric polymer composites and nematic elastomer composites are materials, which exhibit characteristics of both sensors and actuators. Large deformation and curvature are observed in these systems when electric potential is applied. Effects of geometric non-linearity due to the chargeinduced motion in these materials are poorly understood. In this paper, a coupled model for understanding the behavior of an ionic polymer beam undergoing large deformation and large curvature is presented. Maxwell's equations and charge transport equations are considered which couple the distribution of the ion concentration and the pressure gradient along length of a cantilever beam with interdigital electrodes. A nonlinear constitutive model is derived accounting for the visco-elasto-plastic behavior of these polymers and based on the hypothesis that the presence of electrical charge stretches/contracts bonds, which give rise to electrical field dependent softening/hardening. Polymer chain orientation in statistical sense plays a role on such softening or hardening. Elementary beam kinematics with large curvature is considered. A model for understanding the deformation due to electrostatic repulsion between asymmetrical charge distributions across the cross-sections is presented. Experimental evidence that Silver(Ag) nanoparticle coated IPMCs can be used for energy harvesting is reported. An IPMC strip is vibrated in different environments and the electric power against a resistive load is measured. The electrical power generated was observed to vary with the environment with maximum power being generated when the strip is in wet state. IPMC based energy harvesting systems have potential applications in tidal wave energy harvesting, residual environmental energy harvesting to power MEMS and NEMS devices.

Dielectric elastomer actuators (DEA) are a class of eletro-active polymers with promising properties for a number of applications, however, such actuators are prone to failure. One of the leading failure mechanisms is the electrical breakdown. It is already well-known that the electro-mechanical actuation properties of DEA are strongly influenced by the mechanical properties of the elastomer and compliant electrodes. It was recently suggested that also the electrical breakdown in such soft materials is influenced by the mechanical properties of the elastomer. Here, we present stress-strain measurements obtained on two tri-block thermoplastic elastomers (SEBS 500040 and SEBS 500120, poly-styrene-ethylene-butadiene-styrene), with resulting large differences in mechanical properties, and compare them to measurements on the commonly used VHB 4910. Materials were prepared by either direct heat-pressing of the raw material, or by dissolving in toluene, centrifuging and drop-casting. Experiments showed that materials prepared with identical processing steps showed a difference in stiffness of about 20%, where centrifuged and drop-casted films were seen to be softer than heat-pressed films. Electric breakdown measurements showed that for identically processed materials, the stiffness seemed to be a strong indicator of the electrical breakdown strength. It was therefore found that processing leads to differences in both stiffness and electrical breakdown strength. However, unexpectedly, the softer drop-cast films had a much higher breakdown strength than the heatpressed films. We attribute this effect to impurities still present in the heat-pressed films, since these were not purified by centrifuging.

We reported some work on flexible tactile sensors based on Flemion ionic polymer metal composites previously. In this work, we compared the signals in both voltage and current with the signals obtained from a giant nerve fiber reported previously by other researchers. We found some similarities between the artificial tactile sensor and the nerve fiber, in both of which ionic movement play a very important role. This bio-inspired Flemion based ionic polymer metal composites would be a good candidate for bio-related sensors especially for prosthetic limb socket interface applications.

Ionic polymer metal composite (IPMC) is an ideal material for underwater biomimetic robots. Its softness is very helpful for generating biomimetic motion. Because IPMCs naturally contain water they do not require extra sealing. The resulting robot can be soft and lightweight. Previous research on swimming robots is focused on robots swimming in water. In our study we compare the suitability of two different locomotion patterns - tail oscillation and body undulation, for swimming in viscous fluid. We found that in water both patterns could propel the robot by generating vortices behind the robot body. In viscous fluid the robot could be propelled only by body undulation without much disturbance of nearby fluid. Unlike tail oscillation, the whole body undulation was shown to be a suitable pattern for locomotion in both water and viscous fluid.

In this paper we are presenting a concept of a dielectric elastomer actuator (DEA) driven gas valve array for use in a micro burner unit. Such a unit consists of a spatial array of gas nozzles. Every valve controls the gas flow through a single nozzle. With individual control of each valve the burner can be activated partially in controlled spatial patterns. Therefore, the heat dissipation can be controlled and adjusted according to the current needs. For the individual valves a simple control valve rather than a proportional valve can be used. Using dielectric elastomer actuators to control the gas flow an additional demand for thermal decoupling between firing chamber and dielectric elastomer actuator must be met. Therefore, the valve seat is made of a heat-resistant material. With a polymer based ceramic the thermal decoupling can be achieved. Additionally, this material permits the fabrication of arbitrary three dimensional structures. To control the gas flow different configurations of actuator and valve seat are possible. They are compared according to the complexity of the assembly and the possibility of a monolithic fabrication. The different configurations contain different actuation modes (thickness variation versus lateral deformation), direct or indirect control of gas flow and different valve movements relative to gas flow.

The functional principle of peristaltic motion is inspired by the pattern in which hollow organs move. The technology of dielectric elastomer actuators provides the possibility to design a very compact peristaltic pump. The geometries of the whole pump and the actuator elements have been determined by numerical simulations of the mechanical behaviour and the fluid dynamics. With eight independent actuators the pumping channel is self-sealing and there is no need for any valves. The first generation of this pump is able to generate flow rates up to 0.36 μl/min.

The applicability of the polymer-steel sandwich structures has become a topic of interest over the last few years. To study the effect of polymers (which are well-known energy absorbers) on the performance of sandwich structures under blast loads, a set of experiments were carried out on circular polyurea-steel sandwich samples in a 3 Hopkinson bar setup. Using a physics-based material model for polyurea, the test was numerically modeled in LS-DYNA and verified by comparing to experimental results.