EuroEAP platform

In the IoT (Internet of Things) society, electrically activated polymers (EAPs) are promising key materials as soft actuators and sensors because of their light weight, flexibility, and processability. From the viewpoint of human interaction applications, ionic EAP actuators have been receiving much attention because of low driving voltages (~3V). On these backgrounds, we have studied on ionic EAP actuators consisting of carbon nanotubes (CNTs), ionic liquids (ILs), and a base polymer (BP) called as nanocarbon polymer (NCP) actuators. NCP actuators have a three-layered structure where a gel electrolyte layer is laminated by two electrode layers as shown in Fig. 1. The three-layered NCP actuators show a bending motion to the anode side (electromechanical response) when voltages are applied to the actuators. On the contrary, the same three-layered NCPs generate sensing voltages (~mV) when they are bended mechanically from outside (mechanoelectrical response). In this presentation, we will present our research results on the actuation and the sensing properties of NCP composites. Furthermore, we will introduce our application trials with NCP actuators.

Dielectric Elastomers (DEs) are flexible capacitors consisting of a highly deformable membrane coated with compliant electrodes. A DE can be operated as an actuator, by converting applied stimuli into motion, or as a sensor, since its electrical capacitance can be related to the membrane geometry. Eventually, actuation and sensing can be performed simultaneously, achieving the so-called self-sensing mode. Despite their many attractive features, the practical use of DE transducers is currently limited by several factors, such as the high amount of voltage required for achieving a significant deformation (on the order of kV), or the strong input-output nonlinearities which significantly complicate design, modeling, and control. To truly embody smartness into smart materials such as DEs, intelligent control algorithms need to be developed and used to compensate their nonlinearities. In this talk, recent advances on smart algorithms for DE systems will be presented. Topics related to model-based design optimization, motion control paradigms, position/force self-sensing, and sensorless control will be discussed, with a special emphasis on engineering applications in the fields of actuators and soft robotics. Such methods represent a fundamental step towards the development of the next generation of smart material systems.

This talk will discuss recent progress in utilizing liquid metals as conductors for stretchable, soft, and reconfigurable components for electroactive polymeric devices. Alloys of gallium are noted for their low viscosity, low toxicity, and near-zero vapor pressure. Despite the large surface tension of the metal, it can be patterned into non-spherical 2D and 3D shapes due to the presence of an ultra-thin oxide skin that forms on its surface. Because it is a liquid, the metal is extremely soft and flows in response to stress to retain electrical continuity under extreme deformation. By embedding the metal into elastomeric or gel substrates, it is possible to form soft, flexible, and conformal electrical components, stretchable antennas, and ultra-stretchable wires that maintain metallic conductivity up to ~800% strain. Thus, these materials are well-suited for soft robotics, stretchable electronics, and actuators because they can maintain metallic properties during deformation. In addition to introducing the advantages of these materials for such applications (e.g. conductive and self-healing electrodes in electroactive polymers), this talk will focus on recent work to utilize liquid metal for energy absorbing / harvesting materials, stretchable sensors, electrodes for electroadhesion, and soft materials logic. These advances have implications for soft machines and robots that have ultra-soft mechanical properties.

Continuously monitoring flexions and torsions of the human trunk via wearable sensors could help various types of workers to reduce risks associated to incorrect postures and movements. Dielectric elastomer (DE) stretch sensors have been described as a wearable, lightweight and cost-effective technology to monitor human kinematics. Their stretching causes an increase of capacitance, which can be related to angular movements. Here, we describe a wearable wireless system to detect flexions and torsions of the trunk, based on such sensors. In particular, we present: i) a comparison of different calibration strategies for the sensors, using an accelerometer and a gyroscope; ii) a comparison of the DE sensors' performance with that of the accelerometer and gyroscope; to that aim, the three types of sensors were evaluated relative to stereophotogrammetry. Findings show that DE stretch sensors are attractive as a complementary, rather than alternative, technology to inertial sensors.

Supercoiling of double-stranded DNA is a fascinating molecular phenomenon implicated in vital cellular functions such as gene expression, DNA folding and replication. Supercoiling is a response to torsional strain imposed on topologically constrained DNA segments such that any change in the double helix twist is represented as a concomitant change in molecular shape known as writhe. For example, intercalation of small molecules into the double helix can generate plectoneme structures where the DNA wraps around itself rather like a twisted telephone cord. Plectoneme formation draws distant parts of the DNA molecule into close proximity enabling specific protein interactions that trigger processes such as transcription. While DNA supercoiling is not known to be involved in cellular mechanical functions, our analysis of tensile experiments on single DNA molecules shows a work per mass exceeding skeletal muscle. Intercalation of non-tethered DNA leads to unwinding of the double helix in a process similar to the swelling-induced torsional actuation in macroscopic twisted fibres and yarns. Indeed, we were able to demonstrate supercoiling in twisted composite yarns made from polyester sewing thread infused with a pH-sensitive hydrogel. The supercoiling transition generated actuation strokes of 90% and with work capacities exceeding 1 J/g. Coiling the composite yarns by over-twisting produced coiled coils when swollen with simultaneously high strokes and high work capacities.

This presentation describes a 2D positioner made of a double-cone dielectric elastomer actuator. The device consists of two conically-shaped VHB membranes forming a 3D hyperbole. Each membrane is spray-coated on either side with carbon black-silicone electrodes, forming four independent radial actuation segments. The two conical membranes support a central end effector. Via image processing-based motion tracking, we show how, by modulating the activation of the actuation segments, the end effector can be finely positioned in two dimensions. The direction and the amplitude/speed of motion of a central dot are tuned via a custom-made, Arduino-driven, multichannel, high-voltage control unit. Different trajectories forming geometrical shapes (e.g. figure of eight, star, square, cross, circle) are shown, so as to demonstrate the accuracy of the device.

Due to the high demand for human-machine-interaction, especially in the industry 4.0 environment, a flexible and safe interaction between the working tools and the worker, for example through haptic feedback, is very important. Actual systems to facilitate force feedback to a user are mostly very bulky and expensive and the classic actuator and sensor principles are not suitable for integration into textiles. Dielectric Elastomers (DEs) are highly stretchable transducers suitable for a number of application, which allow, in particular, integrating sensor and actuation capabilities into a single soft unit. Due to their lightweight, high energy density, and large deformation, they are particularly suitable to develop user-interface textiles and integrated applications. However, despite the great potential of DEs in the haptic field, the topic has received only little attention so far. This poster shows first results of the development of an intelligent glove prototype based on DE elements. DE elements are used for gesture recognition, haptic feedback to the worker, and potentially combined vibro-acoustic feedback. A DE element with 8 DE Sensors, which is fully integrated into a Glove, is presented. The concept for the integration of haptic and acoustic feedback elements into the Glove, as well as a strategy to embed the driving electronic into the system, is shown. Finally, some possible use- and demonstration scenarios for the envisaged glove prototype are presented.

Electronically conducting polymers (ECP) are promising candidates for the development of flexible microelectromechanical systems (MEMS) and electroactive textiles due to their ability to change dimensions in response to electrochemical stimulation, but also to generate an electrical signal following mechanical stimulation. However, these electroactive polymers require the presence of an ion source, generally in the form of a liquid electrolyte phase, which can limit their range of applications due to leakage and toxicity issue. Turning such "wet" ionic EAPs into "dry" ionic EAPs is then of primary importance to make possible their transfer to practical applications. We describe here the elaboration and characterizations of all-solid-state ionic EAPs, containing no liquid-based electrolyte and behaving both as actuators and sensors. These "dry" ionic EAPs are prepared by using linear polymeric ionic liquids (PIL) associated with a poly(ethylene oxide) (PEO) network and highly conducting poly(3,4-ethylenedioxythiophene) :poly(styrene sulfonate) (PEDOT:PSS) electrodes. The results showed that the use of ECP electrodes and highly conductive PLI-based membranes resulted in actuators and sensors with performances equivalent to similar systems containing a liquid electrolyte phase.

or the production of stacked and individually shaped dielectric elastomer (DE) transducers the aerosol-jet-printing had been chosen and further developed at our institute. This printing technology allows the alternating direct deposition of thin layers of either silicone dielectrics or reduced graphene particle electrodes. As the layers are deposited line-wise the surface quality is an issue which has to be considered to obtain constant and predictable electro mechanical parameters. Typically the characterisation of those material systems is performed following the standards for DE testing by Carpi, et al.. Based on this established standard we built up our test bench for mechanical and electrical multi-analysis of the printed DE. Furthermore, the setup has been automated to make DE characterization more precise and to facilitate the comparison of a large number of samples in order to create a validation routine to optimize the production process. To allow precise positioning of the specimen the four axis have been motorized and the program interfaces are used to align the generated information with other measurable parameters such as environmental conditions or timestamps.

Soft stretchable dielectrics and sensor designs with so called self-sensing capabilities have facilitated the development of large-area electronics (LAE) used for sensing, enabling the deployment of dense compliant sensor networks mimicking sensing skin to allow cost-effective monitoring. A sensing skin based on a soft elastomeric capacitor (SEC) technology was developed in prior work. The SEC is as thin-film, highly compliant, and scalable polymer sensors that transduces geometric variations into a measurable change in capacitance. In this contribution, we proposed a new generation of the SEC sensor equipped with a corrugated surface to provide the sensor with higher sensitivity and sensing directionality. We have selected multiple patterns, inspired by auxetic structures, and designed a set of numerical simulations to predict the functionality of surface textured SECs. These simulations are used to evaluate the performance of textured SECs under composite effect, and to determine the effect on stress re-distribution when fully glued onto biological skin. Results show that the auxetic patterns can yield a significant increase in the overall gauge factor and also decrease the stress experienced by the biological skin located under the SEC. It is shown that a hexagonal honeycomb pattern allows the best performance compared to the other selected patterns.

Dielectric Elastomers (DEs) show several advantages compared to alternative actuator and sensor technologies, e.g., in terms of large deformation, low production cost, and energy efficiency. DEs mainly consist of two elements, i.e., the dielectric membrane and the conductive electrodes. Both of them play a key role in determining the performance of a DE. In particular, the electrical conductivity is attractive, since it allows furthering the bandwidth and the energy efficiency of DE actuators. At the same time, a monotonic, hysteresis-free, and rate-independent relationship between electrode resistance and membrane stretch is attractive for a DE sensor. In our previous research, a bimodal behavior of the electrode resistance w.r.t. the stretch of a strip DE was observed. In this study, the influence of the electrode composition on the behavior of the resistance is investigated. The electrodes composition is based on silicone as matrix material, in which conductive Carbon Black (CB) is used as filler to ensure a conductive behavior. Different CBs, silicones, and CB-to-silicone ratios are investigated. The absolute resistance value, as well as the shape of the resistance-stretch curve, are shown to be strongly dependent on the electrode composition. After showing experimental results, a possible explanation for the bimodal behavior is also presented.

Textile muscle is an important part of the new field of soft electronics since they open new perspectives in promising applications such as robotics or medicine. In order to operate in open-air, yarns or textile actuators employing ionic electroactive-active polymers require an ionic source. This can be provided by the development of ionic coating combining low initial viscosity and fast polymerization for the coating process, good stretchability and ionic conductivity for their operation and no toxicity for contact with user skin. In this work we describe the synthesis of photopolymerizable and biofriendly ionogel coatings, made of UV polymerized poly(hydroxyethylacrylate) networks percolated with Choline Acetate as biocompatible ionic liquid. The low viscosity precursor solution (0.739Pa/s) jellifies in 1 second and present ionic conductivity of 0. 5 mS/cm with stretchability of 85%. In order to improve further the mechanical properties of these ionogels, double network architecture is also explored and demonstrated significant improvement of toughness while maintaining ionic conduction. These coatings appear as a promising candidate for electroactive textile coatings and will be evaluated in a near future for in-air textile muscles.

Dielectric elastomer actuators (DEAs) have gained a significant popularity in application fields such as soft robotics and wearables, due to their unique mix of large deformation, lightweight, and high compliance. In order to produce a significant actuation stroke, a membrane DEA must be coupled with a mechanical biasing system. Commonly used spring-like bias elements, however, are generally made of rigid materials such as steel, and thus they do not meet the compliance requirements of soft robotic and wearable applications. To overcome this issue, in this work we propose a novel type of compliant mechanism as biasing elements for DE actuators, namely a three-dimensional polymeric dome. When properly designed, such types of mechanisms exhibit a region of negative stiffness in their force-displacement behavior. This feature, in combination with the intrinsic softness of the polymeric material, ensures large actuation strokes and high compliance at the same time. After presenting the novel biasing concept, a physics-based finite element model of the biasing dome is derived and experimentally validated. A model-based design algorithm is developed to optimize the dome geometry, in such a way to maximize the overall DEA stroke. Finally, the optimized soft actuator is designed, manufactured, and assembled, and its experimental characterization is conducted. The developed concept will be used, in future research, to develop small-scale and flexible arrays of cooperative DEAs.

Soft materials, such as elastomers, are the materials of choice for dampers due to their inherent energy dissipation. Their dissipative nature results from the entangled network structure formed by long chain polymers connected by chemical crosslinks. We explore silicone-based elastomers blends for their dissipation by using a ball drop test. This offers a simple and quick way to determine the dissipative properties by monitoring the rebound of a steel sphere dropped onto the samples. The steel sphere`s motion is monitored with a high-speed camera and provides information on quantities such as trajectory, acceleration and velocity of the ball before and after impact. We not only evaluated the dissipated energy by rebound resilience, but also calculated work of deformation. To complement the ball drop experiment, the materials were characterized by conventional measurement methods such as dynamic thermo-mechanical analysis and uniaxial tensile testing, with the results obtained being evaluated by theoretical models in conjunction with the results of the ball drop experiment. Both the experimental and theoretical data show excellent agreement and prove that the ball drop test is indeed a simple but effective alternative to conventional measurement approaches.

Here, we present a novel electrostatic actuator that combines the use of thin films, liquid dielectric and stiffening rings, assembled to form circular actuation units that undergoes to out-of-plane expansion/contraction. Prototypes of these actuation units have been tested showing a contraction of up to 40%, a maximum power density during contraction of 100 W/kg, a maximum strain rate of 1000% per second, a bandwidth of approximately 10 Hz, and the ability to lift hundreds of times their weight. Additionally, these units resulted easy to manufacture in different dimensions and can be assembled in arrays and stacks to form electrostatic bellow muscles (EBM) that can be effectively employed as a contractile artificial muscle, as pump and as electrostatic generator. EBM demonstrated their flexibility in matching a wide range of requirements and scales in terms force-displacement combinations and bandwidth. The compact 2-D shape, the low-cost of components, the simple assembling procedure, the high level of reliability and the relevant performance make the EBM a possible enabling technology for a variety of high-performance robotic and mechatronic systems. In this contribution we compare the performance EBM devices implemented with different dielectric materials including biaxially oriented polyethylene, polymide and Polyvinylidene fluoride.

Two-dimensional grids of dielectric elastomer actuators (DEAs) are central to the development of reprogrammable DEA-based shape-morphing devices. A multilayered two-dimensional grid of DEAs can be created by depositing one-dimensional arrays of rectangular electrodes on each layer, placed perpendicularly to the ones on the adjacent layers. In this design, n2 actuators can be addressed using only 2n high-voltage switches, simplifying the control circuitry of high-resolution DEA matrices. The challenge with such a design, however, is to minimize the crosstalk between the individual DEAs. Two types of crosstalk will be described in this presentation. The first type is inherent because all the electrodes in the system act as floating electrodes, resulting in activation of all DEAs in the system but with lower charge. The second type of crosstalk occurs when the DEAs on row r1 and column c1 and row r2 and column c2 are activated simultaneously. In this case, two other DEAs will also be activated inadvertently, one on row r1 and column c2 and the other on row r2 and column c1. It will be shown that this type of crosstalk can be resolved by addressing one DEA at a time and using the fast charging and slow discharging of the low-leakage DEAs.

Dielectric elastomers (DE) are often referred to as being suitable for acoustic applications. Nevertheless, only few concepts have been developed and realized so far, which can hardly compete with conventional electrodynamic loudspeakers. The most prominent examples are vibrating DE-diaphragms that are inflated by a bias pressure. However, adding support or other mechanical systems (pressure pump, magnets, springs, etc.) usually prevents achieving the desired technological advantage using DE and can be further detrimental to broad frequency behavior. We realized and investigated an alternative approach to sound sources based on DE using unimorph membrane configurations. These consist of a circular multilayer stack of a substrate PET-membrane, coated on one side with a metal film and on the other side with a silicone film, with a compliant electrode on top, clamped in a ring structure. Due to the different mechanical properties of the materials, the application of a voltage induced Maxwell stress results in an out-of-plane bending motion and thus a volume displacement. The unimorph membranes were installed as replacement drivers in conventional on-ear headphones, where they showed promising frequency response, sound pressure levels and linearity. Compared to conventional electrodynamic drivers, the DE unimorph membranes are lightweight, free of magnets and magnetically permeable materials, can potentially be manufactured at very low costs and achieve outperforming efficiency.

In this work, we develop a coreless rolled dielectric elastomer actuator (CORDEA) to be used as artificial muscles in soft robotic structures. The new CORDEA concept is based on a 50 µm silicone film, with screen-printed electrodes made of carbon black suspended in polydimethylsiloxane. Two printed silicone films are stacked together and then tightly rolled in a spiral-like structure, which is suitable to be used as tendon-like actuators in soft robotic applications. Readily available off-the-shelf components are used to implement both electrical and mechanical contacts. A novel manufacturing process is developed to enable the production of rolled actuators without a hollow core, with a focus on simplicity and reliability. In this way, actuator systems with high energy density can be effectively achieved. After presenting the design, an experimental evaluation of the CORDEA electromechanical behavior is performed. Actuator experiments in which the CORDEA is pre-loaded with a mass load and subsequently subject to cycling voltage are illustrated, and the resulting performance is discussed. In addition, we observed a repeatable and linear relationship between the strain and the capacitance, which make the CORDEA highly suitable for future implementation of self-sensing concepts.

In recent years, dielectric elastomer actuators (DEA) have gained an increasing importance in research and development studies. Especially in the field of soft robotics, there are many applications at the prototype stage. DEAs consist of a thin electroactive elastomer layer between two compliant electrodes. When an electric field is applied to the elastomer layer, the attractive electrostatic force between the electrodes causes a reduction in thickness and hence an extension in the free spatial directions. In literature, mostly experiments on silicone- and acrylic-based DEAs are reported. However, better actuator performance can be expected with materials that have a higher relative permittivity. This makes unconventional electroactive polymers, such as polyurethane, chloroprene or nitrile rubber, interesting. This poster presents a polyurethane-based planar actuator with respect to its mechanical, dielectric and actuation properties. The hyperelastic material behavior of crosslinked polyurethane elastomer is represented by a nine-parameter Mooney-Rivlin model. A simulation approach for FEA software is shown for the prediction of voltage-induced deformations and compared to the experimental operation of the DEA.

Most of currently available dielectric elastomer actuators (DEAs) operate by using a single membrane, whose stroke ranges on a macroscopic scale (several cm). Alternatively, many small DEA elements can be arranged in an array configuration, thus allowing the development of flexible, energy efficient, and self-sensing cooperative actuator systems. Despite being highly attractive, only few preliminary examples of cooperative DEA systems have been presented up to date. In a DEA array, the closely packed actuators may exhibit a strong electro-mechanical coupling with their neighbours. Such interactions have a strong effect on the overall array performance, and depend on several design parameters. In order to properly design and optimize cooperative DEA arrays, these coupling effects have to be systematically understood first. In our poster, we present on development and modeling of a first prototype of DEA array system. The considered system consists of a 3-by-1 matrix of individually controllable DEA elements, deployed on a single silicone membrane clamped at its outer edges. After describing the system, experimental characterization results are shown. The collected data are then used to validate a physics-based model of the device, which is subsequently used to study the influence of the design parameters (e.g., geometry, pre-stretch) on the spatially-coupled system response. These findings will serve as a first steps towards the development of cooperative DEA arrays.

Current methods of manufacturing dielectric elastomer transducers (DETs) are developed from spin-coating and spray coating technologies. The spin coating method is suitable for thin silicone elastomer film with good uniformity, while the spray coating method is advantageous on fabricating stacked DETs. Also, other silicone objects can be produced traditionally through injection molding, a mature technology developed specifically for large series production. However, for the prototyping of small series of customized products, the process may be expensive. This has motivated the development of advanced manufacturing methods, such as 3D printing technologies, which allows the construction of three-dimensional objects layer by layer following a digital model. Silicone materials such as thermoplastics or metal composites cannot be thermally processed, and to make it possible to use silicones for this purpose, we have had to develop a completely different process. Our technology based on UV-activated curing process requires low energy consumption and is not polluting. In addition, the process is very fast and generates materials with excellent properties for DET technologies.

This work justifies the nonlinearity errors in ionic electroactive polymer actuator lumped-parameter models. The errors are traced back into the model parameters variations as functions of voltage and payload mass. Six experiments with different voltages and payload masses were carried out. Experiments showed that a linear lumped-parameter model with corrected parameters accurately predicts actuator's behaviors as a linear second-order system. Therefore, nonlinearities are mapped to lumped parameter variations. The changes in resistance, capacitance, mechanical pole, and mechanical gain according to the voltage and payload mass are calculated and illustrated. Mechanical pole and mechanical gain are functions of mechanical parameters, namely, second moment of inertia, Young's modulus, and viscosity. Geometrics and electrical transitions due to actuator movement and voltage are responsible for the changes in parameters. The results are promising for a linear and straightforward but accurate loaded and unloaded actuator model.

Recently, electrically driven conductive polymer (CP) coated yarn has shown a great effect to develop soft wearable actuators with synergetic actuation. To address these issues in this work, we introduced and demonstrated a lightweight and flexible actuator technology that can be integrated into fabrics. For this, nonconductive KDK and intrinsically conducting Ag plated KDK commercial yarns were used, and a range of electroactive conductive yarn was prepared by dip-coating with poly (3,4-ethylene dioxythiophene) polystyrene sulfonate (PEDOT: PSS) followed by polypyrrole (PPy) electro-polymerization. Moreover, using one nonconductive and one intrinsically conducting yarn, to understand the voltage drop mechanism during the electro-chemo-mechanical actuation, two different approaches also applied. In the first approach, after applied preload, the actuation behavior of active yarns length was measured by adding the required amount of sodium dodecylbenzene sulphonate (NaDBS) electrolyte in the electrochemical cell. In the second approach, a requisite length of active yarn was cut, and actuation behavior was measure after applied a pre-load. The resultant electroactive yarn exhibit low electrical resistance, high strain (0.64%), and superior electrical stability in NaDBS electrolytes. The new highly conductive yarns will shed light on the development of next-generation textile-based exoskeleton suits, assistive devices, wearables, and haptics garments.

For dielectric elastomer (DE) transducers, the elastic and viscous behavior of both elastomer and electrode materials have significant influence on the actuation performance. Whereas the elastic stiffness affects against the electrostatic pressure depending on the stretch ratio, viscose effects are time-dependent and occur only by changing the stretch ratio. Therefore, not only the stiffness but also the viscosity of materials plays an important role by the material choice, especially for DE-transducers when providing high dynamic actuation. In this contribution, a model based on a combination of a Kelvin-Voigt element and Maxwell element for the viscous-elastic behavior is introduced and subsequently the quasi-static and the dynamic compression tests with an elastomer and two electrode materials are conducted. The dynamic behavior is analyzed by step function responses and sine sweep excitations in order to estimate the model's parameters by an appropriate fitting method. Besides the DE's hyperelasticity, the obtained parameters describe the viscosity-dependent hysteresis, frequently observed in DE-transducers. Finally, the mechanically characterized materials are compared and the results are discussed regarding to the actuation performance of DE-transducers.

Although dielectric elastomers (DEs) typically make use of simple deformation patterns to perform actuation task, in the presence of high-frequency excitation they exhibit higher-order structural modes and complex structural dynamics. Predicting and controlling the voltage-driven continuum dynamics of DEs might pave the way to new applications such as morphing structures, and tunable optic and acoustic devices. We carried out an experimental campaign aimed at the characterisation of the voltage-driven vibrations in a cone DE actuator (C-DEA) layout. By using a 3D laser vibrometer, we measured the complex structural mode shapes and velocity spectra generated applying a broadband excitation on the C-DEA. We were able to explain the observed mode shapes and their natural frequency resorting to a multi-physics model. In particular, we observed that the air pressure loads generated by the DEA vibrations are able to significantly affect the natural modes' frequency. We hence set up a model accounting for the electro-elastic and aero-elastic coupling contributions, and validated it against the data. The model is able to predict the profiles of the different velocity components at different points of the C-DEA surface, within a broad frequency range. The development modelling framework might be used, in the future, for the design of multi-function C-DEAs capable of exploiting different vibration regimes to concurrently accomplish different actuation tasks.

Dielectric Elastomers (DEs) represent an emerging electromechanical transduction technology which enables a variety of new sensor and actuator applications. Features such as low weight, inexpensive materials and high design flexibility make it particularly attractive and competitive compared to traditional solutions. To further develop the technology towards market readiness, there is a growing interest on systematic quantification of its long-term performance in order to obtain a deeper understanding of aging and fatigue behaviour as a function of material, design, manufacturing and load conditions. This work introduces an electromechanical multi-characterization setup on a modular base, which enables this systematic long-term investigation on DEs. Each module permits to arbitrarily program mechanical stroke and electrical voltage, and enables simultaneous testing of five samples. Three modules are placed inside of a climate chamber, which provides reproducible environmental testing conditions. Investigated quantities are force and displacement as well as electric current, voltage, capacitance and resistance. A table control interface enables high flexibility in programming different test routines which are executed sequentially. Extensive safety facilities enable fully automatic 24/7 operation without interruption. First test results are given and evaluated in terms of change of the reaction force, capacitance and resistance over number of fatigue cycles.

Soft electrostatic generators (SEG), typically made of electroactive polymers, represent an efficient way to power up devices widely used in the IoT, including smart clothes, biomechanical energy harvesters or sensors. The working principle of these generators is to use the variation of capacitance to convert mechanical energy into electrical one. Our team demonstrated that an electret can be used to replace the external voltage supply needed for these SEGs leading to an energy self-sufficient soft generator. The goal of our work is to extend the performance of our electrostatic generator by adding a sliding-mode triboelectric function. Both the electret and the triboelectrification contribute to biasing the electrostatic generator made of silicone. We modelled by finite elements the electrical power generated during the mechanical deformation (50% of strain) of our centimeter-scale generator coupling these electrostatic, triboelectric and electret modes. We will compare those results with analytical simulations performed with Matlab, as well as with some preliminary tests of a pure sliding mode triboelectric nanogenerator.

Is a tapered design of dielectric elastomer finger good for grip strength? A dielectric elastomer finger can flex a large angle to grasp an object but the earlier design was flimsy using a single layer of dielectric elastomer actuator and a weak base flexure. How dielectric elastomer fingers can be designed with increased strength to carry at least an apple? It remains a design challenge because multiplying the dielectric elastomer layers or thickening the base flexure are at the great expense of reduced actuation stroke. Interestingly, the anatomy of tendon-driven finger provides some useful design tips. It is known that playing musical instrument or typing a typewriter can blunt the finger tips. This inspires a strengthened design of dielectric elastomeric fingers by having a tapered base flexure but a blunt (heightened) tip. With this optimized finger design, the three- finger grippers of 22.5-gram total weight can carry a 181 gram apple without giving way.

We report an experimental study of the effect of relative humidity, temperature and electric field on the lifetime of silicone-based dielectric elastomer actuators (DEAs) under DC voltage. We then show that lifetime can be increased by up to 300x by using thin passivation layers, with negligible effect on actuation strain. Our DEAs consist of equibiaxially prestretched 50 mm diameter silicone membranes (Elastosil 2030/20, 20 um initial thickness, 12 um thick after prestretch) sandwiched between 4 um thick carbon black - PDMS composite circular electrodes, 5 mm in diameter. A constant DC voltage is applied to the DEAs, whose lifetime is measured under different environmental conditions and electric fields. Relative humidity is an important accelerating factor for dielectric breakdown failure of DEAs. At 90 V/um and at 85°C, the median lifetime drops from 117 hours at 20%RH to 2.8 hours at 85%RH. A similar strong RH dependence is seen at 80 V/um and 100 V/um, as well as at 50°C and 20°C. We demonstrate that adding a 4 um thick soft silicone encapsulating layer on both sides of the DEA yields an improvement in DC lifetime at 85°C - 85% RH of 25x at 90 V/um and of 20x at 100 V/um, leading to much more robust DEAs.

Dielectric elastomers (DEs) are electroactive polymers, capable of realizing multiple functionalities. They are used as soft actuators, sensors and energy harvesters. In recent years, also soft electronic circuits have been successfully built with DE components. This circuitry has the advantage of being intrinsically compatible with other DE devices because they are made of the same materials and with the same processes. An easy-to-use model that can simulate the behaviour of these structures accurately in short times would be an important tool that could support the development of new and more complex circuits. DE devices possess a complex electro-mechanical behaviour. Many models exist for studying DE properties like actuation, leakage current and time-dependent viscoeleastic response. However, they usually rely on complex and time-consuming multi-physics finite element simulations and they usually take into account a single aspect of the device (e.g. actuation, leakage current or viscoelasticity). Here, we present a Matlab/SIMULINK model that takes into account the full electro-mechanical behaviour of DE devices and interconnects multiple units in a circuit network. The model shows a correct prediction of the circuits behaviour and it can be used to study the effectiveness of DE circuit networks before physically building them.

Wrinkled materials are widespread in the natural world and underpin the functionality of a variety of emerging modern technologies. Indeed, the implementation of wrinkles can improve the performance of various devices such as photovoltaics and dielectric elastomer actuators. However, despite tremendous progress to date, the reversible post-fabrication tuning of wrinkle sizes across multiple length scales has remained quite challenging, and the development of comprehensive relationships between structure and function for optically-active wrinkled surfaces has often been fraught with difficulties. Herein, by drawing inspiration from natural micro- or nano-structured cephalopod skin components and leveraging methodologies established for artificial adaptive infrared-reflecting and infrared-transmitting soft actuators, we engineer camouflage surfaces with dynamically-reconfigurable morphologies and concomitant tunable visible-to-infrared spectroscopic properties, while also developing an enhanced understanding of the relationship between their local surface structures and global functionalities. When mechanically actuated, our systems can reconfigure their height frequency distributions by around 180-fold and root-mean-square roughnesses by around 215-fold; When electrically actuated, our systems maintain their highly-desirable visible and thermal functionalities and feature competitive figures of merit and good stabilities upon repeated actuation.

In recent years, soft robots have received increasing attention due to the growing needs in human-robot collaboration. Due to their large deformation, high compliance, and lightweight, Dielectric Elastomer (DE) transducers are suitable for actuation and self-sensing applications in the field of soft robotics. While mathematical models for simple DE actuators configurations have been widely explored in the literature, up to date only few authors have attempted to model complex and multi-degree-of-freedom DE soft robotic structures. In this work, we present a dynamic model for a DE soft robotic system, which can be used for system simulation, design optimization, as well as for the development of control systems and self-sensing algorithms. The structure under consideration consists of a flexible T-shaped backbone with two tendon-like DE roll actuators mounted at the tips, resulting in a multi-degree-of-freedom bending motion. Such a system is intended to be used as a building block for a modular soft robotic tentacle arm. The developed model accounts for both DE material behavior and elastic properties of the flexible structure, as well as for the interaction between the two, by means of a free-energy approach grounded on Lagrangian mechanics Actuation performance of the soft robotic structure, quantified in terms of angular deflection, is compared for different backbone stiffnesses, actuator mounting positions, and DE membrane dimensions.

Currently, ionic electro-active polymers (IEAP) using increases due to their interesting characteristics i.e., large strain response, soft actuation, similarities to biological muscles, . However, IEAP actuators have a complex behavior. This work presents a study on the modeling of an IEAP based trilayer actuator [PEDOT:PSS-PEO/NBR-PEO/PEDOT:PSS-PEO] using the bond-graph method which is a graphical approach based on energetic exchanges. As power is a universal currency in physical systems, it allows taking into account the electro-chemo-mechanical phenomena and the interactions between them. The proposed model is able to predict the electro-chemical (current, voltage) and chemo-mechanical (force, displacement) behaviors of the actuator. Most relevant, with this model, simulation results are in good keeping with experimental ones. In addition, this model can be used to estimate physical values that could not directly be measured. This work is illustrated with simulation results and experimental validations.

The working principle of membrane pumps is based on linear displacements, which are commonly generated by converting rotational motion of electric motors through mechanical transmissions. A more efficient way to generate such motion patterns consists of using linear actuators, e.g., based on dielectric elastomer (DE) transducers. DE technology is known for its advantages concerning weight, energy efficiency, and driving strategies. Membrane pumps consist of three main components: the pump chamber containing the pump membrane, the valves, and the actuator system. All three parts exhibit a different working principle, and have a strong influence on the performance of the pump. In order to use a DE transducer as actuator system for membrane pumps, the influence of the individual components on the load force has to be properly accounted for. First, commonly used working principles are compared and rated according their performance and suitability in conjunction with DEs, with the aim to optimize the system performance. After choosing the most efficient combination of pump chamber and valves, it is possible to determine the load force for different pressures. Based on this analysis, a DE system is designed accordingly. Finally, the functionality of the design method is verified experimentally, based on a custom-developed system prototype.

This work presents a multi-stimuli responsive sensor for artificial skin applications. The sensor can detect surrounding changes in force, temperature and humidity. The proposed design consists of a hydrogel core, responsive to temperature and humidity changes; and a piezoelectric shell for force/pressure sensing. Swelling of the hydrogel core when stimulated, mechanically strains the piezoelectric shell, which results in a measurable electrical output. The two active materials are combined into core-shell nanorods, using vapor-based deposition techniques, namely, plasma-enhanced atomic layer deposition (PEALD) and initiated chemical vapor deposition (iCVD). These deposition techniques provide control over material's mechanical, optical and electrical properties as well as deposition conformity and uniformity. . Fabrication of hydrogel core: humidity (14.2 nC at 96% RH) and temperature (2.1 nC at 30°C) responsive hydrogel, Poly-N-vinylcaprolactam (pNVCL), is deposited using iCVD. The technique gives control over the lower critical solution temperature (LCST).(1) . Fabrication of piezoelectric shell: piezoelectric zinc oxide shell is deposited using PEALD. In PEALD, substrate temperature defines the preferential crystallographic orientation of the deposited material.(2) In this work, piezoelectric zinc oxide with (100) and (002) crystallographic orientation is deposited at 35°C, with piezoelectric charge response of 340 pC at F= 20 N.

For a usual Dielectric Elastomer (DE) actuator, the attraction between the electrodes owing to Maxwell forces entails a reduction of thickness with an expansion of in-plane area. However, the overall response also depends on the local effects induced by polarization, which can be macroscopically accounted for assuming the dielectric constant as a function of the strain. In this case, actuators can exhibit the remarkable theoretical property of CONTRACTING and THICKENING under an electric stimulation. In this work, we show that such counterintuitive behaviours can be achieved by tuning the electric input on tailored hierarchical dielectric composites whose phases obey an ideal dielectric behaviour. Our study concerns laminates for which we highlight the main design parameters, i.e. the shear modulus-- and dielectric constant-ratios as well as the lamination angle, to achieve the new modes. The effect of the layout in limiting, suppressing or promoting electromechanical instability under voltage control is also presented; in some cases, where the instability is suppressed, the maximum in-plane stretch orthogonal to the laminae can increase considerably with respect to a homogeneous actuator. On the basis of our results, hierarchical DE composite materials can be conceived, whose counterintuitive properties can be taken advantage of in the design of innovative actuators, sensors and energy harvesters.

In this work, the mechanical deformation of ionic electroactive polymer (IEAP) based tri-layer micro-actuator subjected to an electrical excitation and mechanical payload is presented. A detailed study on the electrical response of the micro-actuator during charging and discharging process is investigated. Electrical charges, capacitance and resistance of the simplified equivalent electrical circuit are analyzed. The results have shown that, the micro-actuator exhibits a linear behavior for applied voltage lower than 1V. Beyond that, non-linearities appear and are related to the discharging process, especially the corresponding electrical resistance which increases in a non-linear way. Moreover, accumulated electrical charges depend on the previously applied voltage and are not totally restored during the discharging process. The results of this study are illustrated with experimental and theoretical results.

Besides actuation and energy harvesting, dielectric elastomers exhibit also high potential for sensor applications. Dielectric elastomer sensors (DES) are mostly used for strain monitoring, where simple thin elastomer films with stretchable electrode layers are convenient. When the DES is stretched, the capacitance between the electrode layers is enhanced due to the increase of the area and the decrease of the thickness of the capacitor. However, for compression measurements modified sensor designs are necessary, because the known strain sensors are very insensitive to pure pressure loads due to the inherent volume incompressibility of elastomers. Therefore, a new sensor design with enhanced sensitivity for pressure loads is presented. The new sensors consist of a DES film in multi-layer configuration with several dielectric and electrode layers, which is covered on both sides by plates with a pattern of openings. When this sensor composite is compressed, the DES film can locally deform and shift the elastomer material into the neighbored openings, which relieves its compression and the corresponding increase of the capacitance. In contrast, if the plates exhibit no openings or the sensor exhibits no plates, the expansion of the DES film is hindered due to friction. The plates with openings can be made either stiff or flexible. The performance of such compression sensors evaluated in experiments is described and compared with the results of corresponding simulations.

Silicones represent one of the best-performing dielectric elastomers, exhibiting excellent long-term stability and reliability, low creep, scalability, fast response and biocompatibility. However, finding new silicone dielectric elastomers capable to respond to multiple stimuli has attracted the interest of many researchers. Therefore, this work reveals the possibility of extending the applicability of silicone-based dielectric materials by combining the excellent properties of silicone elastomers with those of spin-crossover complexes (SCO). Spin-crossover materials (SCO) are capable of undergoing reversible switching between two electronic configurations (low spin - LS and high spin - HS) upon application of external stimuli, such as temperature, pressure, light, pH, electric and magnetic field. SCO material plays a dual function when incorporated into the silicone elastomer: enhance the dielectric permittivity and induce sensitivity to new stimuli. The results obtained on these composites may contribute to the development of a new generation of materials capable to enlarge the applicability of conventional elastomers.

Commercial yarns can be functionalized with conducting polymers (CPs) to develop yarn and textile actuators. Here we show a method of functionalization of commercial polyamide yarns by poly-3,4-ethylenedioxythiophene:polystyrenesulfonate (PEDOT:PSS) coating. After coating, while PEDOT:PSS is drying, it is possible to twist and coil the yarns, resulting in a major improvement of their linear strain and speed of movement. By using a potential window between +0.6 V and -1.2 V vs Ag/AgCl it was possible to obtain a fully reversible actuation of a coiled yarn providing up to 1.62% strain. A strain higher than 1% was achieved in less than 1 second. Compared to the untwisted, regular yarns, the twisted and coiled yarns produce >9× and >20× higher strain, respectively. These results are a step forward towards the development of soft, silent and compliant smart textile exoskeletons.

Dielectric elastomer (DE) has been extensively studied and considered as a critical component for soft robotics due to its high flexibility and stretchability. However, implementing the integration and fabrication of multi-functional structures on the same DE substrate still remains challenging. In this work, an actuator and square wave patterns with alternative inks were successfully integrated and fabricated on the dielectric elastomer, yielding a soft inverter. The highly electrically conductive carbon nanotube-polydimethylsiloxane (CNT-PDMS) composites were prepared for the dielectric elastomer actuator (DEA) and horizontal patterns, while the vertical patterns (dielectric elastomer switch, DES) were made from piezoresistive carbon black-polydimethylsiloxane (CB-PDMS) nanocomposites. All inks were applied to the dielectric elastomer film (3M VHB) through spray painting. The results indicated that the electrical resistance change of the dielectric elastomer switch could be up to three orders of magnitude when 2500V voltage was applied to the actuator. This entirely soft inverter structure can be potentially applied to develop biomimetic robotics in terms of driving, controlling, monitoring, sensing, and self-regulation.

Over the last 20 years, dielectric elastomers have drawn the attention of scientists due to their versatile properties. They found applications in many areas, including robotics, pumps, valves, sensors, generators, and solid-state electrolytes, to name just a few. Polydimethylsiloxanes are among the best materials for such applications, however, their low permittivity value (around 3) is too low. Here, we report the synthesis, the glass transition temperature (Tg), and the dielectric properties of polysiloxanes with different polarities. For this, we set out from poly(dimethyl-co-methyvinyl)siloxanes with different vinyl group content. The vinyl groups were then transformed into polar groups of various nature by an efficient one-step thiol-ene addition post-polymerization modification. The synthesized polymers were used to establish structure-property relationships. Our results show that the Tg increases with the polar group content and the strength of the polar group. A similar trend is observed for the dielectric permittivity as long as the Tg of the polymer is well below 0°C. Our findings guided us to design polysiloxanes with a permittivity as high as 27.7 and a Tg of -18.2 °C. To the best of our knowledge, this is the highest dielectric permittivity of a polymer with a Tg well below room temperature.

Flexible wearable fabrics have attracted the researcher's attention due to the widely promising applications in real-time display, health monitoring, active and haptic devices, etc. The recent development of electrochemical textile muscles based on conducting polymer is now pushing the demand of ionic coatings combining processability, stretchability and high ionic conductivity for their in-air operation. Additionally, ideal ionic coating must be dry to solve toxicity/leakage issue, with precursors presenting low viscosity and ultra-fast polymerization speed for homogenous coating on textile. Polymeric ionic liquid (PIL) has become one of the excellent candidates for dry ionic coatings. Meanwhile, PEO network has been proved with self-standing ability and good ion-pair dissociation. Therefore, in this work, we described the synthesis of semi-interpenetrating polymer networks based on PEO network and entangled linear polyanion/polycation-type PILs. Their ionic precursor has a low initial viscosity (<0.5 Pa.s) and a fast in-air photopolymerization speed (< 1min), which is suitable for yarn coating. The fabricated materials exhibit good stretchability (up to ~100 % of the original length) and high ionic conductivity (up to 10-5 S/cm), which is even maintained after dry washing process. These materials coatings will be evaluated in a near future as ionic coating on electroactive yarns for haptic textile application incorporated as part of the WEAFING project.

Ionic electroactive polymers are promising materials for actuation and sensing due to their unique benefits such as flexibility, low driving voltage, and large displacement. Their electromechanical behaviour relies on ion exchanges between electroactive electrodes and a surrounding electrolyte under low voltage stimulation (few volts), and opens promising applications in soft (micro)robotics, biomedical devices and recently into electroactive textile muscles. While air-operation of such devices requires an ion source that can be provided by ionogels (combining properties of crosslinked polymer networks and those of ionic liquids), leakage and toxicity issues can arise from the presence of embedded liquid electrolyte. In this work, "dry" and easily processable ionically conducting materials based on polymeric ionic liquid are presented for truly all-solid-state electroactive devices. Besides, the recent progress of vitrimers inspired us to introduce dynamic covalent bonds to endow the all-solid electrolyte with reprocessability and self-healing ability. These materials can be processed through classical coating methods compatible with textile production on classic yarn. Hence, they appear as promising materials for developing actuators integrated in active and haptic clothe.

Recently electronic conducting polymer (ECP) materials have received a critical interest in several applications. Their electromechanical properties are especially interesting in biomedical applications since these biocompatible soft materials can present volume changes under low voltage stimulation in a physiological electrolyte. Thus, they open the possibility of both electrical and mechanical stimulation of cell or biological tissues when implemented in 3D porous materials, providing them with a 4th and time-resolved dimension. The purpose of the project is to develop poly(3,4-ethylenedioxythiophene) (PEDOT) based 4D electrostimulable scaffold as innovative cell culture platform that will combine controlled biochemical, topographical, mechanical and electrical cues, along with tunable actuation. The smart electrostimulable scaffolds are developed through PEDOT functionalization of passive porous polyHIPE structures. These porous polymers are processed by the polymerization of an external phase in a high internal phase emulsions (HIPEs). The final materials present spherical and highly interconnected pores usually ranging from 1 to 100 µm. The electroactive 4D polyHIPE/PEDOT scaffolds present an excellent electroactivity response with a modulated volume variation response. Additionally these scaffolds show promising cells viability and proliferation as well as adhesion of fibroblast cells.

Powered prosthetic devices promise to restore the functionality of lost limbs. However, the design of these devices is limited by the nearly exclusive use of DC motors. The heavy weight, heat generation and slow speed of these motors are significant drawbacks that often lead to abandonment of the device. The field of soft robotics has demonstrated new types of muscle-like actuators, thereby opening up new design opportunities for prosthetic devices that more closely resemble the neuromuscular systems they are designed to replace. Hydraulically amplified self-healing electrostatic (HASEL) actuators are a new type of soft, electro-hydraulic actuator that demonstrates fast actuation speed and high specific energy. This poster presents an evaluation of the first attempt to drive a prosthetic finger with linearly contracting Peano-HASEL actuators. A kinematic model is used to inform the design of a finger that better utilizes the force-strain characteristics of the Peano-HASEL actuator. When compared to a weight-matched DC motor, the Peano-HASEL system consumes 8.7 times less electrical energy to grasp, and is 10.6 times faster with 11.1 times higher bandwidth. However, the DC motor produces 10 times the pinch force at a relevant grip position. We discuss ways to increase the force of the Peano-HASEL actuators, and show how this type of soft actuator allows for prosthetic devices that deliver improved capability to the user.

Traditionally, articulated robots are driven by electric motors giving them strength, speed, and precision, which make them ideal for applications in controlled environments. However, in unstructured environments and in the vicinity to humans these robots often lack the necessary adaptability and can even be dangerous. Replacing electric motors with soft actuators may alleviate this problem by limiting the maximum output force and making the joints backdrivable. This poster presents spider-inspired electrohydraulic soft-actuated (SES) joints that use an electrohydraulic mechanism for actuation that was inspired by the mechanics of spider legs. In SES joints a flexible, dielectric shell is attached to a rotary joint and filled with a liquid dielectric. The liquid dielectric is pressurized with an electric field, which causes deformation of the shell and thus rotation of the joint. We demonstrate actuation angles up to 70°, blocking torques up to 70 mN?m, and specific torques up to 21 N?m/kg. These results are rationalized with an electromechanical model. SES joints also exhibit roll-off frequencies up to 24 Hz and specific powers as high as 230 W/kg. We demonstrate their use in a bidirectional joint, a multisegmented artificial limb with independently addressable joints, and a compliant gripper. Their low profile and weight in combination with their good performance make SES joints ideal actuators for mobile articulating robots for applications in which space is constrained.

Conducting polymer actuators exhibit large strain in response to an external stimulation, thus representing promise materials for MEMS. Presented as a trilayer structure composed of an ion reservoir membrane sandwiched between two electronically conducting polymers (ECP) as electrodes, the actuator exhibits bending deformation as a result of ions movements between the two electrodes during their redox process. We recently reported on the development of micro-actuators based on PEDOT:PSS, a commercially available ECP. Although micro-actuators are very often characterized by applying an AC voltage, many applications require subjecting the actuators to a DC voltage for several seconds or minutes. Some of these applications are the closing of a micro-gripper and the actuation of a cochlear implant during a surgery. With the aim of developing a micro-gripper, the dynamics strain of PEDOT:PSS-based trilayer micro-actuators have been studied by applying DC voltages in order to reach the maximum strain and force. The application of a DC voltage for an extended time shows that the actuator does not go back to its initial position after switching off the power supply. This study reveals the appearance of a memory effect, which is directly related to the intrinsic operation of the ECP-based actuator. These results allow a better understanding of the actuation process and are needful for the modelling and future control of integrated ECP actuators in microsystems devices.

In recent years, many different concepts of smart floors have been presented, which aim to track movement of people or trigger functions in smart home environments. Usually, they are realized by integrating pressure sensitive elements distributed in the area of the floor. In order to minimize costs and thus making these designs commercially attractive as well as reduce crosstalk, the position of the individual units and their shape needs to be optimized, which requires a detailed understanding of how a localized pressure load on top spreads over the floor into the sensitive layer. In this study, we present a multiphysics finite element model of a piezoelectric strain sensor array integrated in a parquet floor tile. The model, which is implemented in COMSOL Multiphysics, takes as input the applied pressure distribution on the topside of the floor. Based on the predefined material parameters we are able to predict the signal of each individual sensor unit in the sensor layer. This takes into account the distribution of strain along the floor tile and thus allows predicting the response of different sensor designs before prototyping. In order to validate this model we have equipped a parquet tile with a screen-printed P(VDF-TrFE) sensor array. Then, we performed a controlled pressure loading with a circular stamp, while simultaneously reading out the signals of all sensor pixels. The comparison of the experimental values and the modelled output shows an excellent agreement.

Conducting polymer-based textile actuators are promising devices that have shown great features, e.g., processability, flexibility, and stretchability. The actuation of these materials is based on the mass transfer from the surrounding electrolyte to the polymer matrix and vice versa. The dopant incorporated during electropolymerization establishes the actuation mechanism of these actuators. Small or mobile anions lead to the anion motion, whereas big anions that cannot move lead to the exchange of cations. So far, most of the developed yarn-based actuators were doped with immobile anions in liquid solutions. However, little is known about the anion exchange in yarns. Here, we present a study on the effect of the dopants, solvents, and polymers on single yarns' strain and actuation mechanism. This work will help understand and develop electrically conductive yarns that can be used to build wearable smart textiles.

Dielectric elastomer generators (DEGs) are a promising option for the implementation of sea wave energy converters (WECs). This contribute introduces a concept of a novel pressure differential WEC equipped with a DEG power take-off operating in direct contact with sea water. The device consists of a closed submerged air chamber, with a fluid-directing duct and a deformable DEG power take-off mounted on its top surface. The DEG is cyclically deformed by wave-induce pressure, thus acting both as the power take-off and as a deformable interface with the waves. This layout allows the partial balancing of the stiffness due to the DEG's elasticity with the negative hydrostatic stiffness contribution associated with the displacement of the water column on top of the DEG. This feature makes it possible to design devices in which the DEG exhibits large deformations over a wide range of excitation frequencies. We propose a modelling approach for the system that relies on potential-flow theory and electro-elasticity theory. This model makes it possible to predict the system dynamic response in different operational conditions and it is computationally efficient to perform iterative and repeated simulations, which are required at the design stage of a new WEC. We performed tests on a small-scale prototype in a wave-tank with the aim of investigating the fluid-structure interaction between the DEG membrane and the waves in dynamical conditions and validating the numerical model.

Dielectric elastomer transducers (DETs) progressively attract attention in research and industry. One major reason is their diverse use as actuators, sensors or even generators. Basically, DETs consist of a dielectric elastomer coated with compliant electrodes. By stacking several of these layers, multilayer transducers can be realized. When electrical voltage is applied to the electrodes, the electrostatic pressure leads to an actuation of the stacked films. With regard to manufacturing, submodules with a small number of layers are produced and DETs can be created by stacking multiple of these submodules. In order to minimize the scrap rate, increase the productivity and monitor the manufacturing process, testing of multilayer composite during manufacturing process could be favorable. The proposed test is capacitance-based and applied on submodule level whereby the composite is placed between two capacitor plates. An electrical voltage is applied to the capacitor plates, so the multilayered composite between the two plates is exposed to an electric field, e.g. 50 V/µm. If two electrode layers are conductively connected due to a defect in production, a breakdown may occur. In this way, faulty submodules can be detected. Methodologically, an analytical approach and FEM simulation are used to design the set-up. Finally, a test procedure to reduce the scrap rate and to improve the production quality is presented and validated by conducting experiments in a laboratory scale.

Dielectric Elastomers represent an attractive technology for the realization of low-cost actuators and sensors. The transduction performance of such systems strongly depends on the material properties of the membrane, especially permittivity and breakdown field strength. To properly characterize these properties, a reproducible testing method is required. In an ongoing study the electrical breakdown in dielectric elastomer thin films subject to voltage application via different electrode shapes - ranging from small spherical and large flat ones to hollow cylindrical shapes - is investigated. A scientific test stand facilitates the exchange of gold-plated electrode tips and thus enables the investigation of different electrical field distributions induced by various electrode geometries. A laser is additionally attached to the setup to provide information about membrane thickness changes during voltage application. The main focus of this presentation, however, is not the illustration of these test results but the depiction of unique enlarged photos, showing amazing geometrical formations and indentations of the silicone film right after breakdown. Additionally, photos and movies were taken over the course of the voltage application until breakdown showing the electro-mechanical effect on the silicone film. These beautiful pictures are intended to make amends to the frustrated researcher, when early breakdown takes place after a carefully assembled experiment.

Textile actuators are a class of wearable technologies that convert electrical energy to mechanical movement through electrochemical reactions by means of conducting polymers. The main merits of textile actuators over the current commercial actuator technologies are that they are light-weight, flexible, and not bulky which all together make them attractive candidates for wearable applications. We have shown that by knitting or weaving actuator yarns into a fabric, it is possible to intensify the total force or strain created by individual yarns which signifies the importance of the performance of individual textile yarn actuators. In this work, we have investigated the effect of the core yarn on the linear actuation of conducting polymer-coated textile yarns. Different yarns, viscose multifilament, viscose Rotorspun, polyamide bulky, and polyamide knit-de-knit were coated with PEDOT:PSS as the first coating layer to make them electrically conductive. Next, PPy was electropolymerized on the PEDOT:PSS coated yarns as the electromechanically active layer. Then, linear strain, as well as blocking force of the different actuator yarns, were investigated as a response to an electrical potential in the range of -1.2 to +0.2 V in an aqueous solution of NaDBS. The actuation results depict that the yarn actuator with viscose core yarn can show linear isotonic strain up to 0.99 % or equivalently linear isometric blocking force of 95 mN.

The project ROBOCOP (ROBOtization of COchlear imPlant) aims at creating a new prototype of cochlear implant with active and sensing part to better control its insertion process, in order to facilitate the work of surgeon, to increase the success ratio, and to decrease the probability of trauma. Such robotization can be provided by the development of low voltage ionic actuators based on conducting polymers. Previous works from LPPI/IEMN demonstrated the possibility to fabricate PEDOT:PSS based trilayer microactuators according to microsystem processes. However, this proof of concept relies on materials and chemical no suitable with biomedical application, more specifically containing and potentially releasing toxic substances. In this work, first results are presented on the fabrication of the micro-transducers. First the composition and synthesis of the PEDOT:PSS electrodes and of the ionic conducting membranes are optimized to limit the presence of any extractible compound. In a second step, two solutions are proposed to avoid the use of toxic ionic liquids: i) using a non-toxic electrolyte such as Saline solution, choline aqueous solution or choline based biocompatible ionic liquid; ii) synthesis of all-solid-state micro-transducers containing no liquid phase able to leak by the use of polymeric ionic liquid. Synthesis, characterization and first actuation results will be described.

Powering DEAs has always been a challenging aspect of the technology due to the voltages required. Especially when the aim of the application is to be portable, compact and efficient. It is for this reason that we developed an electronics system capable to not only supply the necessary high voltages but also recover parts of the electrical energy stored in a DEA that is fully charged. Our device, based on the DC/DC flyback converter topology, is capable to take as input a voltage of only 12V and charge to at least 8kV (and potentially more) a capacitive load. It is also capable to discharge an actuator back through itself, thus recovering energy without any additional electronics. With the current design, we were able to charge a 2.4nF DEA in as little as 10ms to 8kV and discharge it equally fast. The overall efficiency was estimated at around 55% for both the charge and discharge when using a standard capacitor as a load. A drop in efficiency is to be expected when used with a DEA due to the access resistance. During the conference, we plan to present in detail the converter and its various components, as well as show how it performs with various loads going from the basic capacitor to multilayer DEA tubes.