This PDF file contains the front matter associated with SPIE Proceedings Volume 10594, including the Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.

The engineering world has exploded with recent interest in the craft of origami. This traditional art form most often associated with Japan has become fertile ground for inspiration of devices with applications ranging from medicine to aerospace. What is it about origami that makes it attractive, and why is the origami revolution occurring now? This talk will present an overview of the prominent figures and applications that are currently driving innovation in the field. Engineers and artists alike have come together to develop new techniques that take the practice from paper curiosities to practical engineered devices and systems. Foldable tools are now entering the human body during minimally invasive surgery, and foldable optical structures are being designed for the next generation of space-based telescopes. Mathematicians, material scientists, roboticists, architects, and mechanical designers are all investigating classical origami patterns and inventing new ones, benefiting from the insights and craftsmanship of partnering artist. The resulting software tools are accessible by engineers, tinkerers, and artists alike, some of who then leverage laminated manufacturing techniques to fabricate fully operational systems with embedded electrical components and smart material actuation. While engineering is often influenced by external disciplines, such as biology or aesthetics, the melding of engineering and origami has been uniquely synergistic. The interaction of scientists and artists has mutually benefited both sides: beyond the novel advancements in engineering, the artists themselves are taking back the numerical tools and material innovations, using them to produce revolutionary pieces of balanced complexity and elegance.

Electroactive polymers (EAPs) are novel polymeric materials that generate large displacement or strain under electrical field. EAPs show many attractive features such as high electromechanical response, environmental tolerance, lightweight, flexibility, biocompatibility and long-term durability. In 1998, we reported the discovery of a new class of EAP, e.g., high energy electron irradiated P(VDF-TrFE) (poly(vinylidenefluoride-trifluoroethylene)) based electrostrictive polymers, showing large electrostrictive strain (-5%) and relaxor ferroelectric characteristic. Since then, the P(VDF-TrFE) based terpolymers were developed which eliminate the irradiation process. P(VDFTrFE-CFE) terpolymer exhibits very high electromechanical responses (elastic energy density ∼ 1.1 J/cm and electromechanical coupling factor ∼55%). Further, blends approach was studied to increase elastic modulus. Devices based on the high electrostrictive polymers have also been demonstrated, such as micro pump, braille displays, soft robot, et al. These results suggest that P(VDF-TrFE) based electrostrictive polymers are promising for many electromechanical device applications.

Dielectric elastomer (DE) technology is based on the interactions of electrostatic charge with deformable polymer materials. While such materials and their electrical interactions have a long history of investigation, the discovery in the early 1990s that certain thin elastomer films, such as silicone films, were capable of supporting significant electric stress and producing large mechanical output increased interest in this phenomenon. This paper discusses the history of DE technology, presents developments, and considers future progress. Discoveries of large strain outputs with commercially available polymer films has allowed many researchers world-wide to research the technology and explore a wide range of applications. As the technology has matured, new modalities of the fundamental DE operation have emerged. In addition to actuators, researchers began to develop sensors and generators based on the technology. Additionally, explorations of the component materials, actuator geometries, electrode materials, packaging for environmental factors and high-voltage electronics are addressing the lifetime and other limitations of the technology. Examples addressing lifetime include: bistable and shape-memory configurations and self-clearing, carbon nanotubes electrodes. Improved modeling and failure mode investigations are also enabling the technology to progress. A number of commercial products based on DE technology have already hit the market. Although the impact of DEs thus far is well below that of other transducer technologies such as electromagnetics, their technical story and potential continue to expand.

Polyvinyl chloride (PVC) gel is a promising, soft-smart material with electroactive properties, which can be used to make soft robotic actuators with impressive characteristics. However, until now, PVC gel actuators have always been made with rigid metal electrodes, preventing the fabrication of fully soft devices. Here, we present a novel conceptual design for PVC gel actuators. By moving the microstructure from the electrode to the gel itself, we enable PVC gels which exhibit linear contraction when sandwiched between planar electrodes made from any conductive material. We investigate four different microstructures, three of which exhibit higher displacements compared with a traditional (mesh-based) PVC gel actuator. The best performing gel achieved a displacement of 26% of the microstructure height. Finally, we demonstrate an entirely soft PVC gel actuator with thin conductive rubber electrodes. This article is a first step towards totally compliant artificial muscles made from soft electrodes and PVC gels.

To date, water-based ionic polymer metal composite (IPMC) is just regarded as a kind of electroactive material, whereas humidity is traditionally regarded as a disadvantageous factor, the change of which negatively influences the performance of the IPMC. However, the deformation of the IPMC is greatly sensitive to ambient humidity, and can be enhanced dramatically by changing the humidity. In this study, a novel actuation mode is proposed to control the deformation behavior of IPMC by employing moisture as an independent or collaborative incentive source together with the electric field. The deformation is continuously recorded under electric field and electric field-moisture coupling stimulus. These results are consistent with the view that the bending properties of the IPMC are a result of the balance of osmotic pressure and electrostatic stress in the membrane, which is greatly dependent on the change of humidity. Therefore, development of the coupling-drive mode is of great significance for the guidance of material design and application for the IPMC.

Electro-active polymers undergo large deformations while being typically very thin; this encourages us to study the geometric nonlinear set up within the structural mechanics framework of thin plates and shells as a material surface. In this paper, the full set of three dimensional, geometric nonlinear field equations are incorporated to develop constitutive relations by introducing a generalized free energy function, which takes parts from a pure mechanical strain energy (e.g. neo-Hookean) and a mixed electro-mechanical free energy. The key feature is the multiplicative decomposition of the deformation gradient tensor, which allows for separate constitutive models for any electro-mechanic coupling phenomenon. We apply this model exemplary to the case of electrostriction and use the Gauss law of electrostatics in order to incorporate charge controlled actuation, which has been reported to omit pull-in instability. In order to translate the resulting equations to their two-dimensional geometrically nonlinear counterparts for thin plates, a plane stress condition is imposed on the total stress tensor and the effect of the electrostrictive coupling is investigated on voltage controlled as well as on charge controlled actuation, employing non-linear Finite Elements. Finally, results are compared to numerical as well as experimental results on electrostrictive coupling and charge controlled actuation.

Dielectric elastomer actuators (DEAs) are compliant capacitors, which are able to transduce electrical into mechanical energy and vice versa. As they may be applied in different surrounding conditions and in applications with alternating excitations, it is necessary to investigate both, the thermal behavior and the influence of the temperature change during operation. Due to mechanical and electrical loss mechanisms during the energy transfer, the DEA is subjected to an intrinsic heating. In detail, the dielectric material, which has viscoelastic properties, shows a mechanical hysteresis under varying mechanical loads. This behavior leads to a viscoelastic loss of energy in the polymer layer, resulting in a heating of the structure. The non-ideal conduction of the electrode provokes a resistive loss when charging and discharging the electrode layer. Operation with frequencies in the kilohertz-range leads to remarkable local heat dissipation. The viscoelastic material behavior and the resistivity are assumed to be dependent on the temperature and/or on the strain of the material. By this, a back-coupling from the thermal field to the mechanical field or the electrical field is observed. In order to provide a thermal equilibrium, also the convective cooling – the structure is subjected to – has to be considered. Depending on the frequency and the type of electrical driving signal and mechanical load, viscoelastic and resistive heating provide different contributions during the dynamic process. In the present study we capture the described effects within our modeling approach. For a given dielectric elastomer actuator, numerical investigations are performed for a given electrical load.

Dielectric Elastomer Actuators (DEAs) represent a promising alternative technology for common small- and micro-drives, due to their lightweight, high energy density, high design flexibility, and silent operations. In order to obtain a stroke, membrane DEAs need to be preloaded with mechanical biasing elements. The use of negative stiffness mechanisms results in a relatively large stroke, in comparison with conventional biasing systems based on masses or linear springs. Centrally loaded, pre-stressed buckled beams show this negative stiffness behavior in a well-defined range. In particular, their force-displacement characteristics is highly nonlinear and depends on the beam geometry and axial pre-compression.

This paper provides a fast model-based design approach for large stroke DEA systems biased with pre-stressed and centrally loaded buckled beams. The method is based on a Finite Element model of a buckled beam, implemented in COMSOL Multiphysics®. Large deformations are considered in order to accurately design compact DEA systems with highly compressed beams. Stroke optimization is achieved by combining nonlinear beam elements with linear spring mechanisms. This method allows the calculation of the required beam geometry and pre-compression in order to achieve the desired characteristics of the preloading mechanism. The proposed methodology is validated by numerous simulations.

Ionic polymer metal composites (IPMCs) have been the object of intensive research in the last two decades. IPMC actuators promise to find application in medical and industrial settings, where large deformations and low operating voltages are of critical importance. Here, we present a detailed mathematical analysis of IPMC actuation to illuminate the role of counterion size and ionomer-metal composite layers on transient response and back-relaxation. We build on previous work by our group on thermodynamically-consistent modeling of IPMC mechanics and electrochemistry to afford important insight into the physics of actuation across different spatial and temporal scales.

Nafion membranes, are polymeric thin films widely employed in micro-batteries and fuel cells. These devices are expected to play a key role in the next generation energy systems for use in vehicles as a replacement to combustion engines. In fact, a minimum environmental impact is guaranteed by reduced carbon dioxide emissions. It is usually complicated to investigate the behavior of thin membranes through experiments. Therefore, numerical simulations are carried out in order to enable a better understanding of the phenomena and of the multi-field couplings occurring in polymeric membranes.

A continuum-based, three-dimensional and electro-chemo-mechanical (ECM) model for a hydrated polymer membrane is presented. Different effects are taken into account: (i) mechanics, (ii) water uptake, (iii) ion transport, and (iv) electrostatics. The dissipation inequality drives the choice of the suitable constitutive equations of the multi-physics theory. In the mechanical field, an additive decomposition of the deformation gradient in (i) a distortion part, related to the ion motion, and (ii) an elastic part, is assumed. The multi-field model is numerically solved within the finite element framework. Time-dependent simulations are performed by using the commercial tool COMSOL Multiphysics. Furthermore, two closed form solutions are obtained by using (i) a one-dimensional reduced model and (ii) an approach based on the bar theory with an electro-chemical distortion field.

This paper reviews state-of-the-art modeling of viscoelastic behavior elastomer (DE) as active material for actuators. First reviewed are the fundamentals of viscoelasticity theory and modeling based on Boltzmann's Superposition Principle, the key operator based on Laplace transform and its inverse Laplace transform, and Correspondence Principle by which solutions of viscoelastic boundary value problems can be determined if the elastic solution is known. Also discussed are the experimental methods of characterizing viscoelastic behavior of DE materials. Finally, viscoelastic constitutive equations are demonstrated to predict the time-dependent bending displacement and blocking force of DE actuators.

DEAs used in applications such as tunable lenses, soft robotics, etc. are expected to survive many thousands to millions of stretching cycles without degradation of their performance. Here, we present a measurement technique to characterise the evolution of the resistance of compliant electrodes submitted to cyclic biaxial strain, which represents the stretching configuration to which DEAs are usually submitted. We apply the novel electrode resistance degradation (NERD) method to the characterisation of compliant electrodes obtained by inkjet printing a carbon black suspension. We show that although the electrodes can sustain 1 million cycles of stretching at 5%, a 10% cyclic strain causes a much faster degradation, leading to a reduced actuation strain over time. We show that increasing the thickness of the electrodes leads to cracking and accelerated degradation; two layer electrodes degrade more rapidly than single layer electrodes. The NERD setup represents an efficient tool to quickly evaluate the suitability of different electrode formulations for use as compliant electrodes for DEAs.

Advances in soft robotics and fluidic medical devices motivate the development of large, soft pumps that can efficiently pressurize and/or control volumes of fluid. Dielectric elastomer actuators (DEAs) have gathered recent interest due to their low cost, large strains, power efficiency, and high energy density. However, developing reliable, compliant electrodes for DEAs remains an open problem due to challenges with patterning robust conductors that do not appreciably stiffen the actuators. In this work, we present a method for utilizing fluid electrodes to drive an elastomeric diaphragm pump, where a dielectric elastomer membrane separates the internal fluid of the pump, which we connect to a power supply, from an external fluid connected to ground. Two one-way check valves govern the flow of fluid into and out of the internal chamber of the pump. When we apply a voltage to the internal fluid with respect to the external, grounded fluid, the electric field across the dielectric membrane induces an electrostatic force on the membrane, which compresses the membrane and causes it to expand outward, causing an increase in the volume of the internal chamber of the pump. This volume increase draws fluid in through the input check valve. When the electric field is removed, the elastic restoring force of the membrane returns the internal chamber of the pump to its original volume, forcing the excess fluid through the output check valve. This soft pump has a minimum of moving parts, operates silently, and obviates the need for the lubrication and maintenance required of traditional diaphragm pumps. This research opens the door for low-cost, silent, elastomeric pumps for biomedical or soft robotic applications, especially where excess noise, vibration, or contaminating materials are a concern.

Pathological tremor is an involuntary, rhythmic movement that can inhibit the ability of a person to perform everyday tasks. Recent research explores mechanical means of tremor suppression as an alternative to drugs and surgery. However, traditional control methods also suppress voluntary movements due to the close proximity of tremor frequency and the frequency range of typical voluntary motions. Therefore, the controller must identify and suppress the tremor torque with minimal influence on voluntary movement. In addition to the control design, the actuator plays a critical role in the performance and potential for clinical implementation of a tremor suppression system. Dielectric elastomers offer unique actuation capabilities due to their low stiffness compared to traditional engineering actuators. In particular, dielectric elastomers have similar mechanical properties as human tissue, making them ideal for actuation of the human body. This work applies an adaptive notch filter algorithm for vibration attenuation in a narrow frequency range using dielectric elastomer stack actuators. In this controller, an estimation of the tremor frequency ensures suppression of only the tremor motion. The adaptive filter estimates the tremor torque, and a force controller for the dielectric elastomer tracks the specified force. Simulations show excellent tracking of the desired motion for slower voluntary motions and for slowly varying tremor amplitudes. Even though the controller has diminished tremor suppression in the presence of rapid changes in tremor amplitude, it still offers a significant improvement over the uncontrolled case. Altogether, this work demonstrates the potential for the use of dielectric elastomer actuators in a soft orthosis to suppress pathological tremor.

Cellular biology is a promising field of application for dielectric elastomer actuators (DEAs) given that large strains are needed but only low forces are required. The development of devices compatible with standard cell culture protocols and equipment is however challenging. We recently demonstrated that DEAs can be interfaced with living cells and used to control their mechanical environment. Here we detail the fabrication process of our DEA-based cell stretcher and present a holder which was designed to provide a simple and safe experience for our biologist partners. We also evaluate the actuation performance of the device in terms of strain amplitude, spatial distribution and stability during periodic actuation. Results show that the device can generate more than 30% uniaxial tensile strain, and achieve more than 12 h of stable actuation performance when cycled between 0% and 12% strain at a 1 Hz frequency.

Dielectric fluid transducers (DFTs) are electrostatic devices which alternate solid compliant dielectric layers/electrodes with dielectric fluid layers, and they enable the conversion of electrical energy into mechanical work (and vice versa) through capacitance variations associated with a modification of their shape. Compared to other capacitive transducers, e.g., dielectric elastomer transducers, DFTs feature better tolerance to electrical break-down and larger ratio between converted energy and stored elastic energy. To date, practical DFT topologies have been proposed and demonstrated for both actuation and generation purposes, showing promising performance in terms of converted energy density and efficiency. This paper presents an overview on operating principles/layouts, introduces a simplified analytical modelling approach and proposes some figure of merit to evaluate the performances of this new class of transducers.

A novel glove with dielectric elastomer sensors is introduced which serves as a wearable operation device for the control of a multitude of technical functions. The glove carries three types of capacitive sensors which are attached to various fingers. Two strain sensor films on the backside of the index finger and middle finger can monitor the bending of the fingers which causes a stretch of the sensor films. Proximity sensors consisting of two components which are distributed on different fingers are capable to detect the mutual approach and the contact of the fingers. Finally, with a dielectric elastomer pressure sensor on the thumb, the force which is exerted by pressing another finger on the thumb can be continuously measured. Using combinations of these different sensors, even complex control operations may be performed with the glove. The pressure and strain sensors are exploited to tune a technical function such as light intensity, sound loudness or temperature to an intended value. With the contact sensors, the tuned value can be fixed. Some test scenarios to evaluate the performance of the different types of dielectric elastomer sensors on the glove were carried out. In two operation scenarios, the possible exploitation of the glove for the tuning of technical functions is outlined.

Dielectric Elastomer (DE) stack-transducers enable high force densities and considerable deformations since they consist almost only of active material. Within this contribution a transducer system comprising a DE stacktransducer and a bidirectional fly back converter as efficient power supply is considered. Based on an analytical model of this system an impedance and position controller is designed. Using this model, the transducer force can be determined with the measured driving voltage and deformation so that an explicit force measurement is not required. Due to the characteristics of the control plant the sliding mode control design is applied here. Adaptations of the controller ensure both high dynamics and accuracy with significantly reduced switching frequencies. Finally, the control is experimentally validated with different scenarios for exemplary applications using a prototypic bidirectional fly back converter and automatically manufactured DE stack-transducer.

Fabrication of dielectric elastomer actuator (DEA) using additive manufacturing techniques can provide an alternative solution for current manufacturing processes of DEAs that are generally inconsistent and time consuming. In addition, additive manufacturing can allow DEAs with complex geometric configurations to be realized. This study investigates analytical approaches to optimize the performance of helical dielectric elastomer actuator (HDEA) based on additive manufacturing technologies. Optimized geometric configurations tailored to additive manufacturing and proper material selection for elastomer and electrode can improve the overall performance of HDEA. Due to the absence of pre-stretch in the elastomer membranes with additive manufacturing, associated drawbacks, such as electromechanical instability, high external voltage requirement, and their alternate solutions are analyzed and discussed. The performance of HDEA are evaluated by displacement, block force, and weight-to-force ratio by varying multiple geometric parameters including membrane thickness, pitch angle, inner-toouter electrode ratio, and actuation voltage. Since the selection of materials is as important as the geometric parameters of the actuator, printable elastomer and electrode materials with dielectric and mechanical properties for HDEA are evaluated. By optimizing geometric parameters and selecting appropriate materials based on its properties, appropriate manufacturing techniques are discussed to print both dielectric elastomer and electrode layers.

Soft electroactive devices such as dielectric elastomer actuators have been the subject of research for several decades. One of the reasons they have not found many industrial applications to date is the challenge of manufacturing such devices cost-effectively. 3D printing is now widely used to cut manufacturing time and cost in many industries, but functional and soft materials for 3D printing are still very limited. Here we present a process that could be used to 3D print functional soft, electroactive devices like dielectric elastomer actuators and sensors. We propose a simple, low-cost 3D printing platform that uses direct ink writing of elastomer composites with low filler loading of carbon-based nanoparticles. These composites allow the deposition of smooth, uniform layers as well as rapid curing of printed materials with UV light. A diode laser is then used to induce a chemical transformation of the elastomer to create conductive patterns for electrodes with arbitrary shapes and high detail. The process is still limited by the low elasticity of the laser induced electrode material but if more suitable materials can be found, this process could dramatically reduce the time, cost and complexity involved in manufacturing dielectric elastomer devices while at the same time greatly increasing the possible geometric and functional complexity of the 3D printed devices.

We made low-resistance electrodes for a dielectric elastomer system (DES) without the use of thin film deposition or wet lab processes by utilizing a stretchable conductive fabric, Less EMF Stretch Conductive Fabric (SCF), for electrode material. Carbon-based DES electrodes are easy to make, but they have high resistances (kilo ohms) that hamper dynamic operation and reduce energy efficiency. Metal and hydrogel DES electrodes have much lower resistances (tens to hundreds of ohms), but they require complex manufacturing processes, such as thin film deposition or wet lab synthesis. Conductive fabrics can have low resistance and they can be made into DES electrodes with merely a laser cutter and a dry lab environment, but their stiffness may hinder DES performance. This work reports electrical and mechanical properties of SCF and a more compliant, though less conductive fabric, MedTex P70+B, and describes the assembly and performance of DES variable stiffness modules using them.

SCF had low sheet resistance, less than 3.0 ohm/square even during 125% biaxial stretch, and both fabrics stretched beyond 200 % uniaxial elongation before mechanical failure. The assembly of modules with conductive fabric electrodes was comparable in terms of difficulty to that with carbon powder electrodes, and produced functional modules. However, the stiffness of the fabrics diminished DES stiffness-reduction performance to merely 12.8 % and 13.4 % compared to the 24.5 % stiffness reduction a DES module with carbon powder electrodes achieved. Future work should investigate or develop more compliant conductive fabrics that would yield greater DES performance.

Electro-active polymers (EAPs) such as P(VDF-TrFE-CTFE) was demonstrated to be greatly promising in the field of flexible sensors and actuators[1], but their low dielectric strength driven by ionic conductivity is main concern for achieving high electrostrictive performance. The well-known quadratic dependence of applied electric field on strain response as well as mechanical energy density highlights the importance of improving EAPs electrical breakdown while reducing the leakage current. This paper demonstrates that by controlling processing parameters of polymer synthesis and fabrication procedure, it is possible to drastically increase the electrical breakdown and decrease the ionic conductivity, giving rise to an enhancement in breakdown voltage of around 64% and a reduction in leakage current intensity of 73% at 30V/μm. Effect of polymer crystallinity, molecular mass, as well as crystallization temperature on leakage current were also investigated..

In this paper, we present the preparation of a novel elastomeric electrode and characterize its properties. Meanwhile, a casting process is developed to manufacture multilayer dielectric elastomer actuator, which based on silicone material and elastomeric electrode. This process casts every layer by a casting coater, and the formed thickness was adjustable. Besides, the casting process makes it possible to make complex electrode geometries in the millimeter scale. At last, the experiment results demonstrate that the multilayer DEA manufactured by this process enjoys the advantage of homogenous and reproducible properties as well as no performance degradation after one-year use.

Several studies have been reported on the development of controllable catheters in the biomedical field. Electronic conductive polymers (ECP) actuators appeared to be among the most suitable systems thank to their biocompatibility, low operating potential (± 2V) with a reasonable deformation (2%)[1–3]. Electroactive catheters, especially in neurosurgery, should have two levels of properties: strong deformations tip in order to reach, for example the aneurysms and sweep the total volume of the pouch, and sufficient rigid middle part for getting forward in the tortuous vessels network. We designed an electroactive catheter, constituted of two parts with different deformation ability and modulus. The high deformations tip can be obtained with a weak modulus actuator. On the other hand, the second part needs to possess high modulus where small deformations are sufficient. In this work, interpenetrating polymer networks (IPN) will be used as the structural material of the catheter. The IPN architecture allows the synthesis of actuators containing the ions necessary for the redox process and thus avoiding any interference of the position control due to the exchange with the ions from the physiological medium. In addition, the fact that the catheter can be synthesized in a customized way allows modulating its mechanical properties. By introducing a rigid polystyrene network into a specific part of the actuator, it is possible to locally increase the rigidity of the device while keeping reasonable deformation. First, we will describe the synthesis and the characterization of a beam shape actuators with different local stiffnesses. Then, the first steps for the elaboration of tubular actuator will be presented.

Humanoid robot head designs that have embedded actuators within the elastomeric skin solve most of the problems of hardware integration and space requirement of perepheral elements. Presently, most humanoid robotic heads use actuators such as servo motors and pneumatic actuators to achieve head movements and facial expressions. These actuators are expensive, bulky, heavy in weight, and take up a lot of space. The use of embedded actuators will closely mimic the natural human head that consists of numerious muscles and sensors. Here, we present soft actuators based on twisted and coiled polymer (TCP) muscles within elastomeric skin for the robot face design and development. The TCPs are made of silver-coated nylon 6,6 following the common fabrication process: twisting, coiling, annealing and training. The fabricated skin was mounted on a 3D printed humanoid head and facial expressions were tested. We showed several head movements and the six basic facial expressions. It is for the first time such significant improvement is shown in humanoid robots with facial expressions due the embedded actuators in the silicone skin.

Actuators are the most important elements that affect the performance of biorobotic systems design and development. One of the objectives of this project is to design stronger, lighter, 3D printable, functionally graded bone-like structures and bio-inspired musculoskeletal system for the articulation of robots. Another objective is to identify the fundamental science of manufacturing and modeling of the muscle systems. A modular building block is presented consisting of bone-like structures, cartilages and artificial muscles (that are inexpensive and powerful), which can be cascaded to create complex robots. In this paper, we present terrestrial robots as a demonstration of the building blocks for biorobotic systems. We particularly illustrate a humanoid robot developed using soft actuators based on twisted and coiled polymer (TCP) muscles. The integration of TCPs in biorobotic systems has some challenges to overcome such as initial pre-stress, adding multiple actuators in parallel or in antagonistic pair and speed of actuation and other accessories. We will quantify the performance of these robots experimentally. We presented two TCP muscles types, one without heating element and the other one that incorporates a heating element that allows electrical actuation.

In this paper, we present a new design of head immobilization system for head and neck (H and N) cancer radiotherapy. The immobilization system consists of a radio-translucent 3D printed thermoplastic, helmet-like structure open partially in the front and custom-made fluidic actuators. The system can be actuated using compressed air to induce pitch and roll rotations. The mechatronic components of the system include two valves for each chamber, a microcontroller, airflow sensor, power supply, a compressed air source, and one pump to remove air. All of these are kept away from the patient's head so as not to interfere with the radiation beams, and radiation transparent tubing are connected with the chambers to the mechatronic components. The design provides comfort to patients due to curvature fit of patient head/neck and the use of soft actuators. The material used for custom-made actuators is silicone elastomer Eco-Flex 30. The main design variables are air chamber size, air pressure, volume flow rate, number of chambers, layers of sealing and shore hardness of the elastomer. Various arrangements of actuators and designs are investigated. The fabricated new actuators specifically designed for the positioning system were characterized using a humanoid robot head that mimics an actual patient’s head. We hope that the new device will give comfort to patients due to curvature fit of patients’ head/neck and the soft compliant actuators.

Natural flyers including birds, bats, and insects have been the subject of increasing interest for scientists and engineers to understand their physical flight mechanisms. It is also of interest to translate natural mechanisms to micro-aerial vehicles (MAV’s). The compliant skin of the wing distinguishes bats from all other flying animals, and contributes to bats’ remarkable, highly maneuverable flight performance and high energetic efficiency. Here, a simplified constitutive model accounting for an active wing membrane is implemented in ABAQUS and coupled with an in house CFD solver for FSI problems on a standard airfoil configuration. The preliminary results show that a highly compliant membrane that allows kinematic motions leads to areal strains than can enhance aerodynamic performance and provides an operating space unavailable to flexible and rigid airfoils. The results suggest that intramembranous muscle-like activation can significantly modulate camber under static conditions, which increases aerodynamic performance and may allow local control to maintain attached flow.

Dielectric Elastomers (DE) represent an attractive technology in the field of electromechanical transducers for the realization of low cost actuators and sensors. These devices consist of a thin DE membrane with flexible electrodes resulting in a stretchable capacitor. An electrical field, applied by the electrodes causes a thickness reduction due to the dielectric forces in the membrane resulting in a mechanical output. The actuator performance strongly depends on the material properties of the membrane, especially permittivity and breakdown field strength. To characterize the enhanced materials developed by current researches a reproducible testing method is needed. This work presents the development, realization and validation of a scientific test stand to investigate the electrical breakdown in dielectric elastomer films under different environmental conditions. The presented test setup allows the study of various film thicknesses at comparable conditions. Exchangeable electrode tips allow the research of different electrical field distribution induced by the electrode geometry. A fine adjustable contact pressure ensures a defined mechanical contact with the film surface while creating minimal film thickness deformation in a repeatable manner. Furthermore, this enables to research the influence of the contact pressure on the electrical breakdown field strength. An exchangeable specimen frame offers easy film preparation with different pre-stretch strains and spatial resolved thickness measurements in preparation of the breakdown test. To allow the characterization of the film under different ambient conditions the test stand is placed in a climate chamber controlling ambient temperature and humidity. A remote-controlled servo motor allows spatial resolved breakdown voltage measurements resulting in combination with the local thickness measurements in a breakdown field strength.

Ionic polymer-metal composites (IPMCs) have inherent sensing properties, one application of which is flow sensing. However, the transduction physics and mechanics of IPMC pose challenges in deciphering the sensor output for DC flows. In this work we propose a novel IPMC flow sensor that exploits self-generated von Kármán vortices to produce vibration of the sensor, the frequency and amplitude of which are correlated with the stream flow. The sensor consists of a 3D-printed soft cylindrical sheath housing an IPMC beam, and one end of the sheath takes the shape of a sphere. In the sensing configuration, the sheath is placed parallel to the stream flow direction, with the sphere end fixed. Experiments are conducted in a flow channel to measure the IPMC sensor output and free-end displacement of the sheath under different flow speeds. The results indicate that the proposed sensor structure can produce significant oscillatory signals for effectively decoding the flow speed.

In this paper, we designed and demonstrated an IPMC actuated wing for mimicking flapping motion of a butterfly. Unlike other insects, such as dragonfly, housefly, mosquito etc. with high frequency of vibration (>30Hz on flying), the flapping times of butterfly wing is less than ten times. That’s to say, the frequency of butterfly wing is lower than 10Hz. So it is feasible that utilizing IPMC actuator with excellent advantage of low frequency response to imitate the flapping motion of butterfly. Firstly, to improve the frequency response of IPMC actuator, we fabricated the strip shaped IPMC with the thickness less than 100μm and Au electroplating was employed in the preparation process. Secondly, IPMC actuated wing and biomimetic butterfly fully made of IPMC were designed and fabricated. Finally, we measured and evaluated the deformations, block forces and lift forces of the flapping wing. Experimental results demonstrated that thin IPMC exhibits a large flapping with light weight, which is more suitable for flapping wing.

Increasing research interest and immense development of electroactive polymers (EAP) has paved way for various micro positioning tasks and underwater applications. Ionic Polymer Metal Composite (IPMC) a subset of electroactive polymers encompasses a wide range of control applications. Open loop behavior of IPMC is often not repeatable and is always troublesome to maintain a constant specified tip-position in open loop. Also open loop response of IPMC is prone to a larger overshoot hence, an efficient closed loop IPMC control becomes evident for many high precision applications. In this article an optimal position control of IPMC based on Particle swarm optimization (PSO) technique is proposed. A comparative study of PI (Proportional integral) tuning parameters based on conventional Ziegler-Nichols (ZN) and PSO tuning technique is done. This comparative study accounts for various important step response characteristics like rise time, settling time and maximum overshoot. Ziegler-Nichols (ZN) tuned parameters ݇k_p=22.24 and k_l=1588.7 decreased the overshoot from 523% to 23.2% and reduced the settling time from 113s to 54.4ms. However the gain parameters ݇k_p=668.0479 and ݇k_l=1246.4 obtained from the Particle Swarm Optimization technique eliminated the overshoot and further reduced the settling time to 1.2ms successfully minimizing the closed loop error. Hence this study shows that PSO tuning technique is advantageous over conventional ZN method in estimating the optimal tuning parameters and thereby alleviating the system dynamic performance.

This paper presents the design, fabrication, and testing of a novel 6 legged terrestrial walking robot inspired by the movements of an ant, while the ionic polymer-metal composite(IPMC) is used as the leg actuators. This terrestrial walking robot (size: 34 mm × 20mm ×28 mm, weight: 2.43g) is able to move in open air independently. The legs of the robot are made of a spatial two-degree-of-freedom (2DOF) IPMC actuator structure which shows great characteristics in movement and load-carrying capability. The different dimension of the IPMC actuator and the parameters of the leg structure are tested and optimized to cater the demand of different part of the leg structures. The robot is controlled by a microprocessor, an on-board lithium battery is used as the power and the square wave signal is employed to drive the 6 independent leg structures.

One-dimensional artificial muscles like natural muscles have been studied for robots and artificial limbs to exoskeletons. Particularly, an artificial muscle using carbon nanotube (CNT) is very light and has excellent mechanical performance, and therefore CNT is researched as a promising material for artificial muscle. Here, we demonstrated large tensile stroke of CNT based artificial muscle with graphene inside. Using biscrolling method shown in previous CNT hybrid yarn supercapacitors, electrochemical capacitance of artificial muscles could be increased by implanting graphene into CNT yarns. These graphene biscrolled CNT artificial muscles have slightly lower mechanical properties than bare CNT yarn artificial muscles, however it shows superior tensile stroke because of its large capacitance. In addition to graphene, these artificial muscles have shown the possibility that other materials or strategies in reported supercapacitor studies can also be applied to improve the performance of electrochemical artificial muscles. Larger actuation of graphene biscrolled CNT artificial muscles could be applied to such areas as prosthetics devices.

For centuries scientists have dreamt with devices able to mimic the behavior of the biological organs. One of the key aspects of that behavior is the ability to sense the working conditions while actuating. This is due to the electrochemical reactions taking place in the intracellular matrix which provoke the exchange of ions and water with the surroundings. With the view to reaching that potentiality conducting polymers have been widely studied, they are reactive materials constituted by polymeric molecular motors giving multifunctional sensing-actuators whose working principles are the same that those of the biological cells. They are soft materials, containing macromolecules whose conformational movements allow ionic and water exchange. In this work polypyrrole/dodecyl benzene sulfonate (PPy/DBS) films were electrogenerated using different electrochemical parameters giving as a result polymer with different thickness whose mechanical and actuating properties were studied finding relationship between them and with the oxidation state that could lead to the production of conducting polymers with tailor-made properties.

Ionic electro-active polymers (EAP) are promising materials for actuation and sensing. In order to operate in open-air, they are usually built in a trilayer configuration where the internal polymer membrane is soaked with an exogenous electrolyte and sandwiched between two electronic conducting polymer (ECP) layers. The use of exogenous electrolytes can be a limitation in several applications since it may lead to evaporation issues and leakage. Moreover, the soaking step, necessary to introduce the electrolyte in the device, can become tricky as soon as microdevices are considered. In this work we describe the synthesis and characterization of truly “all-solid-state” ionic actuators by using polymeric ionic liquids (PILs). PILs are a new class of polyelectrolytes presenting ionic liquid-like ions along their polymer backbone. First, ECP electrodes containing PIL are synthesized by vapor phase polymerization and their thickness and electronic conductivity are characterized. Then, electrodes and PIL-based membranes are assembled into a trilayer configuration as a proof of concept of solid-state ionic actuator. Under 1.75V, a strain difference about 1% is reached.

Bio-inspired polymeric artificial muscles have been regarded as perfect candidates for future soft electronic devices such as human-friendly wearable electronics, and soft haptic-feedback systems. However, for more practical applications of polymeric artificial muscles, the drawbacks of the artificial muscles including response time, power generation, durability, and cost-effectiveness remain to be resolved. Here, we report a bio-inspired high-performance artificial muscles based on three-dimensional networked carbon nanostructures, which provide an electrically conductive network in the electrodes. The three-dimensional networked carbon nanostructures exhibit high specific capacitance in both aqueous and non-aqueous electrolyte, large specific surface area, and high electrical conductivity. Moreover, the bio-inspired artificial muscles were successfully demonstrated with high strain and long-term durability under low input voltages, owing to the outstanding features of three-dimensional networked carbon nanostructures. Therefore, the bio-inspired artificial muscles with 3D-networked carbon nanostructures can play key roles for next-generation soft and wearable electronics.

Among the main issues with the implementation of Dielectric Elastomer Generators (DEGs) is the need for pre-charging to perform mechanical-to-electrical energy conversion. In cases when energy harvesting has to be performed in an environment with unpredictable characteristics (e.g., wind, waves, human walking), defining the best times for charge injection and energy extraction in a cycle is a non-trivial problem. In this paper, we present a novel Self-Sensing with Peak Detection (SSPD) method to control the charges on the material using capacitive self-sensing techniques, which defines an optimal cycle and requires no knowledge of the mechanical excitation amplitude or frequency. The effectiveness of the approach is proved by means of numerical simulations based on an highly accurate model of the DEG device.

Dielectric Elastomers (DE) represent an attractive technology for the realization of low cost and highly stretchable capacitive sensors. The novel contribution of this work is the development of a nonintrusive DE sensor (DES) for polymer tubes, capable of measuring pressure levels inside the tube up to 60 bar. A novel solution is proposed to perform the measurement, in which a membrane DES is wrapped around the tube. While the tube expands due to high pressure, the DES capacitance increases accordingly. To perform system characterization, a test rig is designed to measure the expansion of a polymer tube while applying an external pressure. Several experiments are performed to obtain the tube characteristics at different pressure levels. Based on theoretical predictions and tube characterization, membrane DES are developed, manufactured, and then characterized. Finally, it is shown how the change in capacitance can be related to the pressure inside the tube, allowing to obtain the desired measurement. The performance of the device is assessed by means of several experiments.

Networks of soft wearable stretch sensors offer a distinctive advantage over camera based motion capture systems, since they can operate outside studios or laboratories. Soft sensors can be placed tightly against the skin, and are therefore capable of detecting soft tissue deformation, which is essential for reconstructing natural motion. However, the large number of sensors necessary to capture multiple limbs at a high enough spatial resolution requires many non-stretchable wires and rigid connectors, which severely compromise user comfort. In previous work, we have demonstrated how the wiring can be minimised in soft capacitive stretch sensing. Multiple sensors were interconnected with fixed external resistors along a R-C transmission line, which allowed capacitances to be measured through a single channel. We have now taken a similar approach towards resistive stretch sensors that change their resistance under deformation. The proposed method is based on a sensing transmission line consisting of resistive stretch sensors and fixed capacitors. The transmission line impedance was measured by applying excitation voltages with different frequencies. A system of nonlinear equations was established from measured and mathematically modelled transmission line resistances, and solved numerically for the unknown sensor resistances. Measuring multiple sensor resistances through one channel reduces the number of wires and connector, and potentially leads to a smaller circuit board footprint.

Accurately capturing human motion underwater has potential applications in diver health monitoring, human- machine interaction and performance sport coaching. Unfortunately the human body has approximately 200 bones and 600 skeletal muscles giving rise to a broad range of degrees of freedom. To effectively capture this movement with dielectric elastomer sensors a substantial network is required. One often overlooked challenge is the connection between the dielectric elastomer sensor and central electronics. On land this is as simple as wires connecting the two. Underwater however, especially when considering a network of sensors, this becomes a more complicated task.

In the proposed method parallel plate capacitors are used to transfer power across the encapsulation layer to the sensor, removing any need for protruding wires or cable glands. With one electrode placed within the encapsulation and the second connected to the sensor, sensors are replaceable even underwater. To maintain sensor performance however, a relatively high capacitance is required. For example if the coupling capacitance is 20x greater than sensor capacitance, sensitivity is reduce by approximately 20%. Whereas if the coupling capacitance is only 10x greater, sensitivity is reduced by 40%. Due to these high capacitance requirements combined with the area and weight restrictions of wearable applications, we have investigated the practicality of implementing capacitive coupling. A capacitive coupling interface has been developed and tested with dielectric elastomer sensors underwater. Analysis of the interface's impact on sensor sensitivity, measurement electronics and overall coupling capacitor size is presented.

The lateral line system is the flow-sensing organ of fishes, which consists of arrays of flow sensors, known as neuromasts, with hair cells embedded inside a gel-like structure called cupula. There are two types of neuromasts: the superficial ones, which extend from the skin and respond directly to the local velocity, and the canal ones, which are located in recessed canals under the skin and tend to respond to the flow pressure gradient. Inspired by the canal system of fish lateral lines, we propose a pressure gradient sensor integrating an ionic-polymer metal composite (IPMC) sensor with a 3D-printed canal filled with a viscous fluid. Unlike the biological counterpart that has open ends on the surface of the body, the proposed canal has two pores that are covered with a latex membrane, which prevents the canal fluid from mixing with the ambient fluid. Experimental results involving a dipole source show that the proposed sensor is able to capture the pressure difference across the two pores, and the viscosity of the canal fluid has a pronounced effect on the sensitivity of the device. Preliminary finite-element simulation results are also presented to provide insight into the experimental observations.

Vibration-based energy harvesters have been extensively studied and investigated to harvest the energy produced by environmental mechanical vibration sources as mean to produce low electrical energy, thereby supplying low-power sensors and actuators. Different devices have been proposed as energy harvesters, cantilevers-based geometries have been pursued frequently in the literature. Here, we propose the geometry of an elastomeric circular membrane coupled with an electret (soft electrostatic generator) with a central proof mass. By soliciting the designed device around its resonance frequency of 14Hz with an acceleration of 0.4g for a mass of 9.5g, the system produced an average electric power of 24μW for an optimal resistance of 150MΩ. An analytical study developed closely with a finite element simulation with Comsol® allowed to validate the obtained experimental results, suggesting that this approach can be used as a tuning method to develop other geometrical shapes and conceive large-scale devices for vibration energy harvesting applications.

Soft creeping robots have great potential in fields of search-and-rescue for their excellent body compliance and adaptability in unstructured environments and the capacity of passing through a narrow space. But most of the reported soft creeping robots can only crawl forward or backward except a few ones can swerve using a differential actuation mechanism, the maneuverability of the existing soft creeping robots are generally poor which limits their practical applications. In this paper, we design a soft creeping robot driven by dielectric elastomer (DE) which has the ability of omnidirectional movement. The robot mainly consists of a circular deformable body and six thin feet which are evenly distributed around the body circumference. The robot body is an annular dielectric elastomer actuator (ADEA) made by connecting a six-segment dielectric elastomer minimum energy structure end to end, which has excellent ability of active deformation controlled by applied voltages. The six feet are essentially six paper-based electroadhesion actuators which can achieve adhesion or detachment with the ground. Experimental tests for the active deformation performance of the ADEA are implemented for optimizing design of the robot. Then through activating different DE segments, the ADEA deforms from a circle to an ellipse or some irregular shapes, cooperating actuation with the six electroadhesion actuators the robot realizes free movement towards twelve directions around the plane.

Cephalopods employ their colour-changing skin for rapid active camouflage and signalling in complex visual environments. This is achieved with chromatophores, pigment organs which stretch under electrical stimulation to affect local skin colouration. Mimicry of the dynamic skin patterns of cephalopods in soft materials has the potential to produce novel cloaking suits and illuminated clothing. Here, we present the experimental investigation of bioinspired artificial cephalopod skin made from dielectric elastomer. Using simple local feedback mechanisms, we explore a variety of scalable dynamic patterns which include the travelling waves of the cuttlefish passing cloud display and other complex dynamic patterning.

Embedding polyethylene oxide (PEO) in polypyrrole doped with dodecylbenzenesulfonate (PPy/PEO-DBS) leads to increase linear actuation due to improved ionic conductivity. In this research our goal is to investigate the effect of solvent exchange from aqueous (aq) to propylene carbonate (PC) using same concentration of electrolyte bis(trifluoromethane) sulfonamide lithium (LiTFSI). As previously observed for the case of PPy/DBS films, the actuation direction of PPy/PEO-DBS changed from purely cation-driven in (aqueous) LiTFSI-aq to purely anion driven in (propylene carbonate) LiTFSI-PC. Cyclic voltammetry driven electro-chemo-mechanical-deformation (ECMD) measurements showed that the strain in LiTFSI-PC was more than double than that of aqueous electrolyte consuming only half of the charge density. The diffusion coefficients were determined from the chronoamperometric measurements with higher values found in LiTFSI-PC. Energy dispersive X-Ray spectroscopy and scanning electronic microscopy measurements were performed to characterize the PPy/PEO-DBS films.

The ionic electroactive polymer (IEAP) actuators are the type of smart material that is capable of generating large deformations on the application of a small potential across the electrodes. In addition, the IEAP actuators with ionic liquid as an electrolyte are capable of operating in an open-air environment. These aspiring characteristics put forward these actuators to be a promising candidate for replacing traditional actuators in micro-actuation applications. The CPC actuators are distinguished from other types of IEAP’s by the presence of porous carbon as an electrode material and an ionic liquid as electrolyte. In this work we propose design and fabrication of a multi-degree freedom motion platform based on four carbon-polymer composite (CPC) actuators. The complete platform is fabricated as a single structure with appropriate masking. This motion system is highly dexterous and is capable of generating three different motion namely tip, tilt and piston motion. The experiment results have demonstrated high levels of manipulability from the CPC actuators that are outstanding in the class of soft ionic actuators while keeping the fabrication method simple, scalable and cost-effective.

Conventional electronics are typically rigid, introducing unwanted stiffness to otherwise entirely soft systems. Emerging soft and stretchable electronics provide a platform for integrating driving electronics in soft robotics and structures. A stretchable electrode having strain-dependent resistance is the dielectric elastomer switch (DES). The DES enables direct control of artificial muscles, or dielectric elastomer actuators (DEA), a popular material in soft robotics. Electromechanically interacting DEA and DES together make up smart actuator networks, with the DES as piezoresistive-charge gates. The DES is a unique stretchable electrode in that it directly couples mechanical strain with a logic state change. We have previously demonstrated logic gates and memory elements using DES/DEA arrays. Performance, particularly speed and cycle life, were limited due largely to acrylic-based, viscoelastic materials and hand-made fabrication process. Here we present computing elements with enhanced performance, comprising silicone membranes and airbrushed silicone-based electrodes. We also demonstrate a new model - a dielectric elastomer digital oscillator. The oscillator provides the timing signal for sequential logic elements, which reduces number of wires and inputs needed for DE circuits. Finally, we also use the mechanosensitive DES to implement adjustable frequency of the DE oscillators.

Interest in soft actuating mechanism using by soft elastomeric materials is gradually growing for next-generation devices such as wearable electronics, haptic feedback systems, and soft robotics. However, for more practical and feasible applications in diverse devices, soft and flexible actuators require multi-functionalities. Here, we report the morphological variation of void-patterned dielectric elastomer actuators with mechanically stretchable AgNWs electrodes on elastomer surfaces, utilizing simple void-patterning process. In macroscopic view, the actuator showed one-directionally deformed actuation properties in pre-patterned void-direction. And, the ridges and vertices of the deformed surfaces were observed under the control of an input voltage to the elastomer haptic interface. In addition, the variation in the morphology of the stretchable electrodes deposited on elastomer film under various electrical input were verified by measuring the vertical displacement of the elastomeric actuator, showing the surface roughness, from 0 to 120 um along the void-direction. Also, the deformed-area can be controlled by AgNWs electrode patterning. The present study successfully demonstrated the elastomeric actuator performance under electrically controlled inputs, which were used to modulate the elastomeric surfaces with continuous roughness levels. These results reveals that the morphological variation of the flat surface can be applicable to haptic interface for regenerating surface texture.

Artificial muscles have the potential to fill inherent gaps left behind by large, hard, complex traditional actuators. One such emerging category of artificial muscles which is showing potential in filling these gaps is composite yarn hydrogel actuators. Hydrogels are soft, potentially biocompatible, polymer materials which can be tuned to have varying swelling ratios to produce the desired mechanical response. Composite yarn hydrogel actuators function by an embedded hydrogel swelling within the confined fibrous structure of a twisted yarn. This hydrogel swelling exerts pressure on the yarn which, in turn, drives either torsional or linear actuation, depending on the twisted structure of the composite yarn. The focus of this research is to develop techniques to produce, test and model this new class of actuator. We will endeavor to garner a deeper understanding of the effects of hydrogel swelling ratio, applied yarn-twist, and the complex structure of the composite actuator. Composite yarn hydrogel actuators comprising of niobium nanowire/hydrogel twisted composites have been produced that can generate large and fast torsional stroke as high as 300 deg/mm over 15 seconds when stimulated by water. Simple cotton/hydrogel coiled composites have demonstrated large repeatable linear stroke lengths of 30% contraction upon hydration. A new class of composite actuator (hydrogel composite tube actuators) can show combined linear and torsional actuation within the same device.

Windows whose transmittance can be modified by an applied voltage have previously been fabricated from soft, transparent elastomers sandwiched between ITO coated glass and a compliant, silver nanowire top electrode.1 In this contribution we extend the capabilities of the tunable window so that the optical transmittance can be varied spatially over the window according to voltage signals applied to different segments of the back electrode of the window, defined by patterning of individually addressable electrodes. The actuation signals are controlled using TTL-level input signals applied to high voltage switches. We also show that the spatially tunable window can be fabricated on a flexible substrate, such as PET, and the optical transmittance is not affected by bending of the substrate. The use of a polymer substrate not only increases possible applications of this class of voltage controlled light modulation device but also has the potential of reducing cost at an industrial scale by replacing more costly ITO coated glass substrate.

A novel artificial muscle actuator called as twisted and coiled polymer actuator can be easily fabricated by commercially available Nylon fibers. It can be thermally activated and has remarkable properties such as large deformation and flexibility. The actuator using conductive Nylon fibers can be activated by Joule heating and easily controlled; however, it is reported that dynamics exhibit nonlinear property due to a heat transfer and a thermomechanical property. In addition, it is reported that dynamic characteristics change from several conditions such as load, ambient temperature and the fabrication method. These finding suggested that the actuator may not able to achieve high accuracy control compared to electrical motors. Therefore, it is desirable to construct controllers that have good robustness and high tracking performance. PID controls with nonlinear compensator have been applied for the twisted and coiled polymer actuator. The PID controller should be adjusted for good robustness and high tracking performance depending on external disturbance, load weight fluctuation or reference signal. In this paper, a control system with the disturbance observer is applied to solve these problems. The actuator model is identified by using input-output data and a control system is designed to compensate the external disturbance based on the actuator model. The validity of the applied method is investigated through numerical simulations.

Dielectric elastomers (DEs) stand out among various soft actuators for their exceptionally fast response and large actuation. A dielectric elastomer can emerge out-of-plane vibration under alternating voltage and change its resonance frequency by adjusting the direct voltage. In this paper, the emerging conditions of the out-of-plane vibration of dielectric elastomer resonator (DER) are obtained by changing the pre-stretch, electrode area and the amplitude of the voltage. Sweep frequency tests are conducted to obtain the resonance frequency of DER, and the modals of the vibration are also obtained by experimental measurements. The nonlinearity vibration phenomenon which appears along with the increase of the amplitude of voltage is analyzed. The resonance mechanism of DER has a high energy exchange efficiency, which has a potential application in soft robot.

This paper shows an experimental demonstration of a high efficiency step-down circuit for a dielectric elastomer generator. The step-down circuit, consisting of a surge arrester and a transformer, is classified as a passively-switched flyback converter and can transfer energy efficiently. In the experiments, the efficiency of the step-down circuit is nearly 100 times higher than that of a Zener diode, which is used for the simplest step-down conversion. Also, we discovered that the harvested power and the efficiency are improved better if the breakdown voltage of the surge arrester is selected to be higher. Finally, the wireless transmission of a microprocessor is demonstrated using the step-down circuit connected to a dielectric elastomer generator and a self-priming circuit.

This paper focuses on the torsional motion of a torsional type fishing-line artificial muscle actuator, so to speak, Twisted Polymer Fiber (TPF) actuator. TPFs are expected as limited rotation motors or limited angle motors for mechatronic applications. Aiming to construct a gray-box model for TPF actuators, this paper derives the first-order transfer function as the model from the applied electrical power to the generated torque of an actuator. The relation from the temperature to the generated torsional torque is simply assumed as a linear function of which coefficient is the torsional rigidity. In the experiment, the validity of the obtained model is evaluated, and then the blocked torque of the TPF actuator is controlled.

Dielectric elastomer generators (DEG) are well suited to harvest energy from natural motion sources (e.g. water, human locomotion). DEG require a source of high voltage charge to generate energy. In low cost, low power DEG, a high voltage charge source is expensive and impractical to implement. The Self Priming Circuit (SPC) can be used to remove the high voltage charge source and replace it with a low voltage one. The SPC works by moving charge onto and off the DEG in synchrony with DEG compression to enable voltage boosting. For the initial cycle a low voltage source is still required in the form of a battery or similar device which in some instances can completely discharge, rendering the DEG useless. Another approach is to include an electret into the DEG design. The electret acts as a permanent voltage source for the DEG and SPC. This allows the DEG to receive a medium voltage (much higher than a battery) from the electret and then boost this voltage up to a high voltage where generation efficiency is improved. This paper presents an integrated SPC with an electret charge source that is capable of boosting quickly to a high voltage without the addition of external charge.

Ras Labs Synthetic Muscle^TM – a class of electroactive polymers (EAPs) that contract and expand at low voltages – mimic the unique gentle-yet-strong nature of human tissue. These EAPs also attenuate force and sense mechanical pressure, from gentle touch to high impact. This is a potential asset to prosthetics and robotics, including manned space travel through protective gear and human assist robotics and for unmanned space exploration through deep space. Fifth generation Synthetic Muscle^TM is very robust and attenuates impact force through non-Newtonian mechanisms. Various electrolyte solutions and conductive additives were also explored to optimize these EAPs. In prosthetics, the interface between the residual limb and the hard socket of the prosthetic device is a pain point. EAP pads that gently contract and expand within the prosthetic socket using 1.5 V batteries will allow for extremely comfortable, adjustable, perfect fit throughout the day for amputees. For robot grippers, EAP linkages can be actuated and EAP sensors placed at the fingertips of the grippers for tactile feedback. Onset of actuation of these EAPs at the nano-level was determined to be within 48 milliseconds, with macro-scale actuation visible to the naked eye within seconds. Smart EAP based materials and actuators promise to transform prostheses and robots, allowing for the treatment, reduction, and prevention of debilitating injury and fatalities, and to further our exploration by land, sea, air, and space.

For actuator applications, conducting polymers are typically deposited at lower temperatures e.g. -20°C, in order to obtain more regular, smooth and ordered films with fewer defects. Clearly, standard aqueous electrolyte solutions cannot be used at these temperatures, and some organic solvents cannot be used, as not all salts are soluble in these. A wellknown approach is to use ethylene glycol: water mixtures (often 50:50 wt%, PPy/CDC(EG:W). The goal of this work is to analyze the role of water in the solution: to compare the linear actuation properties of conducting polymer hybrid films PPy/CDC(EG) polymerized from just ethylene glycol solution and that with 50% water, both at -20°C. Cyclic voltammetry and chronoamperometric electro-chemo-mechanical-deformation (ECMD) measurements were performed to study the linear actuation properties in lithium bis(trifluoromethylsulfonyl)imide in aqueous solution (LiTFSI-aq). Both conductivity and linear actuation strain were found dependent on the solvent in the polymerization solution with ethylene glycol: water the clearly superior solvent choice.

Multi touch sensors are widely used for screen interfaces, but are at an early stage of development for soft wearable technology and humanoid devices. We demonstrated a soft, flexible and stretchable tactile dielectric elastomer (DE) capacitive sensor array which is designed for multi-touch applications. The touch input is measured by the capacitance variation resulting from the deformation of the sensor modelled as a variable parallel plate capacitor. The flexibility and soft nature of capacitive DE sensor makes them comfortable to wear and versatile. This sensor module is composed of a 2-D capacitive sensor array composed of a grid of DE sensors. The sensor arrangement enables the measurement of touch capacitance on and between sensor centerlines. This technology has fewer connections with fewer wires and enables continuous location identification; convenient for emerging wearable technology as well as humanoid devices. It is possibility solution for wearable technology that needs to measure the reaction of forces in the human body; and can also be applicable to measure/control in humanoid devices to determine grasp ability to pick up an object.

Carbide-derived carbon (CDC) based actuators have been typically formulated as trilayer systems and applied in bending displacement. In this work, we want to demonstrate that CDC deposited on glass fiber fabric (CDC-TL) with an additional poly-3.4-ethylenedioxythiophene (PEDOT) layer electropolymerized on top forming a polylayer (expressed as CDC-PEDOT-TL) can be used as a linear actuator. Isotonic and isometric electro-chemo-mechanical deformation (ECMD) measurements in lithium bis(trifluoromethane) sulfonamide propylene carbonate (LiTFSI-PC) were performed, revealing that the CDC expansion at discharging can be found in CDC-PEDOT-TL (main expansion at oxidation of 0.5% strain) in same extent of 0.24 %. The stress found in similar values of 30 kPa for both system. Besides the nearly 5times better conductivity of CDC-PEDOT-TL, the charge density reduce nearly half in comparison to CDC-TL.

Future low-voltage dielectric elastomer transducers (DET) based on nanometer-thin elastomer membranes rely on soft and compliant metal electrodes with reasonable electrical conductivity and sound adhesion to the elastomer. State-of-the-art adhesion promoters, including nanometer-thin Cr/Ti films, form defects for applied areal strains larger than 3% and lead to the stiffness increase of DETs. To generate forces in the Newton range, these lowvoltage DETs have to be stacked to thousands of layers. Herein, we present a compliant electrode, which consists of gold covalently bonded to thiol-functionalized polydimethylsiloxane (SH-PDMS) films. The membranes were fabricated using molecular beam deposition and in situ and/or subsequent ultraviolet light (UV) radiation. Peeloff tests demonstrate the expected strong binding of Au to the SH-PDMS network. The highly stretchable Au/SHPDMS layer withstands strains of at least to 60% without losing the conductivity. Optical micrographs exhibit cracks for strained pure Au and Au/Cr electrodes but not for the Au/SH-PDMS layer. The mechanical properties and adhesion forces of Au/SH-PDMS were extracted by means of atomic force microscopy (AFM) using a spherical Au tip coated with methyl groups (CH₃). The elastic modulus of (12 ± 9) MPa is slightly higher than for 20 nmthin Au/PDMS, but can be tailored by the cross-linking density of Au/SH-PDMS via the UV-irradiation dose. Unloading nanoindentation curves revealed the pull-off forces between the CH₃-functionalized AFM tip and the Au/SH-PDMS layer at the time of separation. For Au/SH-PDMS, the spectral distribution of pull-off forces exhibits repulsive forces with the CH₃ groups of the PDMS network as well as adhesive forces resulting from interactions with the nanometer-size Au clusters. This approach proves the way to homogenously bind gold clusters within the SH-PDMS film. Such compliant electrodes are the prerequisite to fabricate low-voltage DETs stretchable by more than 50%.