This PDF file contains the front matter associated with SPIE Proceedings Volume 9798 including the Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.

Soft artificial skin with embedded sensors and actuators is proposed for a crosscutting study of cognitive science on a facial expressive humanoid platform. This paper focuses on artificial muscles suitable for humanoid robots and prosthetic devices for safe human-robot interactions. Novel composite artificial skin consisting of sensors and twisted polymer actuators is proposed. The artificial skin is conformable to intricate geometries and includes protective layers, sensor layers, and actuation layers. Fluidic channels are included in the elastomeric skin to inject fluids in order to control actuator response time. The skin can be used to develop facially expressive humanoid robots or other soft robots. The humanoid robot can be used by computer scientists and other behavioral science personnel to test various algorithms, and to understand and develop more perfect humanoid robots with facial expression capability. The small-scale humanoid robots can also assist ongoing therapeutic treatment research with autistic children. The multilayer skin can be used for many soft robots enabling them to detect both temperature and pressure, while actuating the entire structure.

Several reports have appeared on the topic of anisotropic actuation in dielectric elastomers. Most of these, including our own published in Advanced Materials (2014), incorporate aligned microfibers into the VHB adhesive. In all these studies, the results have been quite promising, demonstrating that anisotropic actuation is achieved primarily in the direction normal to the fiber axis. We have previously explored this phenomenon in detail using polyurethane and carbon fibers. In the present study, we shall use these results to set the stage for our ongoing studies that employ our unique thermoplastic elastomer gel (TPEG) design, which provides much more versatility than VHB. These results allow us to decouple the roles of dielectric constant and mechanical modulus in actuation development.

Use of dielectric gel encapsulation is reported to make acrylic elastomer (VHB 4905) electrically stronger. Acrylic dielectric elastomer actuators (DEA) with silicone gel encapsulation can sustain an electrical breakdown field of up to 532MV/m, higher than 315MV/m of non-coated ones. Hence, its ultimate areal strain of 228% is larger than 189% of latter. This enhanced dielectric strength and actuation is attributed to the delayed electrothermal breakdown of VHB with silicone gel encapsulant that bars oxygen supply in air.

Dielectric elastomers are a class of soft, active materials that have recently gained significant interest due to the fact that they can be electrostatically actuated into undergoing extremely large deformations. An ongoing challenge has been the development of robust and accurate computational models for elastomers, particularly those that can capture electromechanical instabilities that limit the performance of elastomers such as creasing, wrinkling, and snap-through. I discuss in this work a recently developed finite element model for elastomers that is dynamic, nonlinear, and fully electromechanically coupled. The model also significantly alleviates volumetric locking due that arises due to the incompressible nature of the elastomers, and incorporates viscoelasticity within a finite deformation framework. Numerical examples are shown that demonstrate the performance of the proposed method in capturing electromechanical instabilities (snap-through, creasing, cratering, wrinkling) that have been observed experimentally.

Energy efficiency, lightweight and scalability are key features for actuators in applications such as valves, pumps or any portable system. Dielectric electroactive Polymer (DEAP) technology is able to fulfill these requirements¹ better than commonly used technology e.g. solenoids, but has limitations concerning force and stroke. However, the circular DEAP membrane actuator shows a potential increase in stroke in the mm range, when combined with an appropriate biasing mechanism². Although, thus far, their force range is limited to the single-digit Newton range, or less^3,4. This work describes how this force limit of DEAP membrane actuators can be pushed to the high double-digit Newton range and beyond. The concept for such an actuator consists of a stack of double-layered DEAPs membrane actuator combined with a biasing mechanism. These two components are combined in a novel way, which allows a compact design by integrating the biasing mechanism into the DEAP membrane actuator stack. Subsequently, the single components are manufactured, tested, and their force-displacement characteristic is documented. Utilizing this data allows assembling them into actuator systems for different applications. Two different actuators are assembled and tested (dimensions: 85x85x30mm³ (LxWxH)). The first one is able to lift 7.5kg. The second one can generate a force of 66N while acting against a spring load.

In this paper, we present a simple printing method for a highly resilient stretch sensor. The stretch sensors, based on multi-walled carbon nanotubes (MWCNT)/silicon rubber (Ecoflex® 00-30) polymer nanocomposites, were printed on silicon rubber (SR) substrate. The sensors exhibit good hysteresis with high linearity and small drift. Due to the biocompatibility of SR and is very soft, strong and able to be stretched many times its original size without tearing and will rebound to its original form without distortion, the proposed stretch sensor is suitable for many biomedical and wearable sensors application.

In this work we present a new fabrication technique to print thin dielectric elastomer actuators (DEAs), reducing the driving voltage below 300 V while keeping good actuation performance. With operation voltages in the kV-range, standard DEAs are limited in terms of potential applications. Using thinner membranes is one of the few existing methods to achieve lower operation voltages. Typical DEAs have membranes in the 20-100 μm range, values below which membrane fabrication becomes challenging and the membrane quality and uniformity degrade. Using pad printing we produced thin silicone elastomer membranes, on which we pad-printed compliant electrodes. We then fabricated DEAs by assembling two membranes back to back. We obtain an actuation strain of 7.5% at only 245 V on a 3 μm thick DEA. In order to investigate the stiffening impact of the electrodes we developed a simple DEA model that includes their mechanical properties. We also developed a strain-mapping algorithm based on optical correlation. The simulation results and the strain-mapping measurements confirm that the stiffening impact of the electrodes increases for thinner membranes. Electrodes are an important element that cannot be neglected in the design and optimization of ultra-thin DEAs.

In this paper, we report on the fabrication of a self-sensing electroactive polymer cantilevered bimorph beam actuator and its frequency response. Tip deflections of the beam, induced by applying an AC signal across ferroelectric relaxor polyvinylidene fluoride-trifluoroethylene chlorotrifluoroethylene (P(VDF-TrFE-CTFE)), reached a magnitude of 350μm under a field of ~55MV/m and were recorded externally using a laser Doppler vibrometer (LDV). Deflections were determined simultaneously by applying a sensing model to the voltage measured across the bimorph’s integrated layer of piezoelectric polymer polyvinylidene fluoride (PVDF). The sensing model treats the structure as a simple Euler- Bernoulli cantilevered beam with two distributed active elements represented through the use of generalized functions and offers a method through which real time tip deflection can be measured without the need for external visualization. When not being used as a sensing element, the PVDF layer can provide an additional means for actuation of the beam via the converse piezoelectric effect, resulting in bidirectional control of the beam's deflections. Integration of flexible sensing elements together with modeling of the electroactive polymer beam can benefit the developing field of polymer microactuators which have applications in soft robotics as "smart" prosthetics/implants, haptic displays, tools for less invasive surgery, and sensing.

We are developing soft, flexible micromanipulators such as micro- tweezers for the handling and manipulation of biological species including cells and surgical tools for minimal invasive surgery. Our aim is to produce tools with minimal dimensions of 100 μm to 1 mm in size, which is 1-2 orders of magnitude smaller than existing technology. However, the displacement of the current developed micromanipulator remains limited due to the low ionic conductivity of the materials. Here, we present developed methods for the fabrication of conjugated polymer trilayer structure which exhibit potential to high stretchability/flexibility as well as a good adhesion between the three different layers. The outcomes of this study contribute to the realisation of low-foot print devices articulated with electroactive polymer actuators for which the physical interface with the power source has been a significant challenge limiting their application. Here, we present a new flexible trilayer structure, which will allow the fabrication of metal-free soft microactuators.

In anticipation of deep space travel, new materials are being explored to assist and relieve humans in dangerous environments, such as high radiation, extreme temperature, and extreme pressure. Ras Labs Synthetic Muscle – electroactive polymers (EAPs) that contract and expand at low voltages – which mimic the unique gentle-yet-strong nature of human tissue, is a potential asset to manned space travel through protective gear and human assist robotics and for unmanned space exploration through deep space. Generation 3 Synthetic Muscle was proven to be resistant to extreme temperatures, and there were indications that these materials may also be radiation resistant. The purpose of the Ras Labs-CASIS-ISS Experiment is to test the radiation resistivity of the third and fourth generation of these EAPs, as well as to make them even more radiation resistant or radiation hardened. On Earth, exposure of the Generation 3 and Generation 4 EAPs to a Cs-137 radiation source for 47.8 hours with a total dose of 305.931 kRad of gamma radiation was performed at the US Department of Energy’s Princeton Plasma Physics Laboratory (PPPL) at Princeton University, followed by pH, peroxide, Shore Hardness Durometry, and electroactivity testing to determine the inherent radiation resistivity of these contractile EAPs and to determine whether the EAPs could be made even more radiation resistant through the application of appropriate additives and coatings. The on Earth preliminary tests determined that selected Ras Labs EAPs were not only inherently radiation resistant, but with the appropriate coatings and additives, could be made even more radiation resistant. Gforce testing to over 10 G’s was performed at US Army’s ARDEC Labs, with excellent results, in preparation for space flight to the International Space Station National Laboratory (ISS-NL). Selected samples of Generation 3 and Generation 4 Synthetic Muscle™, with various additives and coatings, were launched to the ISS-NL on April, 14 2015 on the SpaceX-6 payload, and will return to Earth in 2016. The most significant change from the on Earth radiation exposure was color change in the irradiated EAP samples, which in polymers can be indicative of accelerated aging. There was visible yellowing in the irradiated samples compared to the control samples, which were not irradiated and were clear and colorless. While the Synthetic Muscle Experiment is in orbit on the ISS-NL, photo events occur every 4 to 6 weeks to observe any changes, such as color, in the samples. The bulk of the testing will occur when these EAP samples return back to Earth, and will be compared to the duplicate experiment that remains on Earth (the control experiment). Smart electroactive polymer 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.

Dielectric elastomers are widely investigated for use as actuators, stretch/force sensors and mechanical energy harvesters. As performance of such devices is limited by the elastomer’s dielectric strength, it is important to investigate the factors that mostly affect the electrical breakdown of those materials. In this paper, we present a preliminary study on the breakdown strength of a widely used poly-acrylic elastomer film, VHB 4905 by 3M with an equi-biaxial pre-strain of 300%. The breakdown was measured with two metal electrodes, one hemispherical and the other one planar, and was characterized under different conditions to investigate the effects of the hemispherical electrode’s curvature, the force applied by the two electrodes and the environmental humidity. With a given radius of curvature, the breakdown field increased by about 50% for a nearly ten-fold increase of the applied mechanical force, while, for a given mechanical force, the field decreased by about 20% for a two-fold increase of the radius of curvature. Furthermore, for a given radius of curvature, an increase of the environmental relative humidity from 0% to 80% caused a reduction of the breakdown field of about 20%. This study shows that the breakdown field of the studied dielectric elastomer is highly dependent on the boundary conditions of the breakdown test, as well as the environmental/storage conditions of the material. Therefore, such conditions must be reported carefully to allow for critical evaluations/comparisons of experimental results. As suggested by our data, variations of the compression, electrode’s curvature and environmental humidity are likely to cause a diversity of possible interplaying effects, some of which are preliminary proposed in this paper and are referred to as topics requiring deeper future investigations.

Dielectric elastomer membrane has the ability of shrinking the thickness and expanding surface area when a voltage is applied through its thickness. Dielectric elastomer has been widely studied and used as dielectric elastomer actuator (DEA), dielectric elastomer generator (DEG) and dielectric elastomer sensor (DES). We study the behavior of several DEAs connected in series and parallel, and find that the different connecting models can achieve different responses of the DEAs. DEAs connected in series can enhance the actuation, while DEA connected in parallel can enhance the actuation force. In our experiment, DEAs connected in series and parallel are loaded in actuation direction under a dead load providing pre-stretch. We discuss the results of the experiments and give the conclusions.

Some recent developments in the areas of soft and basically incompressible electro-electrets (dielectric elastomers) with large strains, of anisotropic polymer ferro- or piezo-electrets with quasi-ferroelectric behavior, of moleculardipole electrets with significant ferro-, pyro- and piezo-electricity, and of space-charge polymer electrets with locally stabilised charges are described. Such materials may be applied, e.g., in soft actuators, energy harvesters and flexible and stretchable sensors for devices such as artificial muscles, electrically controllable refractive and diffractive optics, flexible pyroelectric detectors, motion and displacement sensors, earphones and microphones, ultrasonic transducers, air filters, radiation dosimeters, etc. The performance of dielectric elastomers for actuator, energy-harvester and sensor applications relies on a high relative permittivity and a low elastic modulus. High densities of electric charges in the electrodes are required in order to provide large Maxwell stresses or high energy densities. Significant amounts of localised or trapped charges, as well as electric dipoles from pairs of charges, lead to useful electro-mechanical and mechano-electrical effects (or inverse and direct piezoelectricity, respectively) if they are properly arranged in dielectric materials with extremely low conductivities. Space-charge electret films and ferroelectret systems should exhibit thermal and long-term stability of the trapped charges within the respective materials. Ferroelectric polymers and other polar polymers show useful piezo- and pyroelectric properties if their polymer-chain conformations allow for parallel packing of the molecular dipoles. Space-charge and molecular-dipole electrets are widely applied, e.g. in microphones, air filters, radiation dosimeters, ultrasonic transducers, etc. Basically, the performance of all electro-active polymers relies on the attraction (and repulsion) of electric charges and thus directly on the electro-magnetic interaction, one of the four fundamental interactions.

Soft and stretchy dielectric elastomer (DE) sensors can measure large strains on robotic devices and people. DE strain measurement requires electric energy to run the sensors. Energy is also required for information processing and telemetering of data to phone or computer. Batteries are expensive and recharging is inconvenient. One solution is to harvest energy from the strains that the sensor is exposed to. For this to work the harvester must also be wearable, soft, unobtrusive and profitable from the energy perspective; with more energy harvested than used for strain measurement. A promising way forward is to use the DE sensor as its own energy harvester. Our study indicates that it is feasible for a basic DE sensor to provide its own power to drive its own sensing signal. However telemetry and computation that are additional to this will require substantially more power than the sensing circuit. A strategy would involve keeping the number of Bluetooth data chirps low during the entire period of energy harvesting and to limit transmission to a fraction of the total time spent harvesting energy. There is much still to do to balance the energy budget. This will be a challenge but when we succeed it will open the door to autonomous DE multi-sensor systems without the requirement for battery recharge.

Dielectric Elastomer Generators (DEG) offer an opportunity to capture the energy otherwise wasted from human motion. By integrating a DEG into the heel of standard footwear, it is possible to harness this energy to power portable devices. DEGs require substantial auxiliary systems which are commonly large, heavy and inefficient. A unique challenge for these low power generators is the combination of high voltage and low current. A void exists in the semiconductor market for devices that can meet these requirements. Until these become available, existing devices must be used in an innovative way to produce an effective DEG system. Existing systems such as the Bi-Directional Flyback (BDFB) and Self Priming Circuit (SPC) are an excellent example of this. The BDFB allows full charging and discharging of the DEG, improving power gained. The SPC allows fully passive voltage boosting, removing the priming source and simplifying the electronics. This paper outlines the drawbacks and benefits of active and passive electronic solutions for maximizing power from walking.

One of the main challenges for the practical implementation of dielectric elastomer generators (DEGs) is supplying high voltages. To address this issue, systems using self-priming circuits (SPCs) — which exploit the DEG voltage swing to increase its supplied voltage — have been used with success. A self-priming circuit consists of a charge pump implemented in parallel with the DEG circuit. At each energy harvesting cycle, the DEG receives a low voltage input and, through an almost constant charge cycle, generates a high voltage output. SPCs receive the high voltage output at the end of the energy harvesting cycle and supply it back as input for the following cycle, using the DEG as a voltage multiplier element. Although rules for designing self-priming circuits for dielectric elastomer generators exist, they have been obtained from intuitive observation of simulation results and lack a solid theoretical foundation. Here we report the development of a mathematical model to predict voltage boost using self-priming circuits. The voltage on the DEG attached to the SPC is described as a function of its initial conditions, circuit parameters/layout, and the DEG capacitance. Our mathematical model has been validated on an existing DEG implementation from the literature, and successfully predicts the voltage boost for each cycle. Furthermore, it allows us to understand the conditions for the boost to exist, and obtain the design rules that maximize the voltage boost.

Dielectric elastomers generators (DEGs) constitute promising systems due to their high energy density. This latter is influenced by viscoelasticity and the leakage current. An understanding of this leakage current and how it can be influenced by the stretch state of material is required to predict or optimize DEGs. In this context, our work consisted in studying the evolution of the leakage current in commercial electroactive polymer (3 M VHB4910) using silver grease as electrodes. This analysis has been performed in order to evaluate the influence of three different factors: the biaxial prestretch (λ² = 4, 9 and 16), the temperature (from 20°C to 80°C) and the high electric field (from 1MVm^-1 to 20MVm^-1). Main results are (i) the increase in the leakage current at higher pre-stretch due to the increase of the electric field, (ii) a predominant Schottky conduction mechanism (iii) a lower current at room temperature for asymmetric pre-stretch compared to an equivalent area surface ratio with symmetric pre-stretch, (iv) the point iii fails when the material works at temperatures higher than room temperature. Probable changes in the molecular chains with strain explain these results.

We develop theoretical model based on a general thermodynamic theory of the stress-composition interaction. The electromechanical responses are investigated by means of electrochemical impedance spectroscopy and bending displacement measurements. The model takes into account the electrochemical stress due to the intercalation (de-intercalation) process which generates the strain and bending of the actuators. The relationship between the strains and the real part of the complex capacitance by introducing the strain-capacitance coefficient ξ_C was analyzed.

Polyelectrolyte hydrogels are ionic gels with viscoelastic properties. They are able to reversibly swell and deswell in response to different external stimuli. In the present work stacked layers of hydrogels - also referred to as hydrogel layers - under chemical stimulation are numerically investigated. For this, a set of coupled partial differential equations describing the chemical, the electrical and the mechanical field is solved by using the finite element method. The swelling behavior of the hydrogel layers - obtained by a novel approach for the osmotic pressure - is in excellent agreement with other investigations available in the literature.

The emerging field of soft robotics offers the prospect of applying soft actuators as artificial muscles in the robots, replacing traditional actuators based on hard materials, such as electric motors, piezoceramic actuators, etc. Dielectric elastomers are one class of soft actuators, which can deform in response to voltage and can resemble biological muscles in the aspects of large deformation, high energy density and fast response. Recent research into dielectric elastomers has mainly focused on issues regarding mechanics, physics, material designs and mechanical designs, whereas less importance is given to the control of these soft actuators. Strong nonlinearities due to large deformation and electromechanical coupling make control of the dielectric elastomer actuators challenging. This paper investigates feed-forward control of a dielectric elastomer actuator by using a nonlinear dynamic model. The material and physical parameters in the model are identified by quasi-static and dynamic experiments. A feed-forward controller is developed based on this nonlinear dynamic model. Experimental evidence shows that this controller can control the soft actuator to track the desired trajectories effectively. The present study confirms that dielectric elastomer actuators are capable of being precisely controlled with the nonlinear dynamic model despite the presence of material nonlinearity and electromechanical coupling. It is expected that the reported results can promote the applications of dielectric elastomer actuators to soft robots or biomimetic robots.

Dielectric elastomers have received a great deal of attention recently as potential materials for many new types of sensors, actuators and future energy generators. When subjected to high electric field, dielectric elastomer membrane sandwiched between compliant electrodes undergoes large deformation with a fast response speed. Moreover, dielectric elastomers have high specific energy density, toughness, flexibility and shape processability. Therefore, dielectric elastomer membranes have gained importance to be applied as micro pumps for microfluidics and biomedical applications. This work intends to extend the electromechanical performance analysis of inflated dielectric elastomer membranes to be applied as micro pumps. Mechanical burst test and cyclic tests were performed to investigate the mechanical breakdown and hysteresis loss of the dielectric membrane, respectively. Varying high electric field was applied on the inflated membrane under different static pressure to determine the electromechanical behavior and nonplanar actuation of the membrane. These tests were repeated for membranes with different pre-stretch values. Results show that pre-stretching improves the electromechanical performance of the inflated membrane. The present work will help to select suitable parameters for designing micro pumps using dielectric elastomer membrane. However this material lacks durability in operation.This issue also needs to be investigated further for realizing practical micro pumps.

This study takes the conceptual idea of the helical dielectric elastomer actuator (HDEA) and explores mathematical concepts for the actuator capabilities to provide a reasonable function in an industrial role. In the past, other researchers have demonstrated the contractile capabilities of the HDEA through experimental work and analytical modeling. The researchers in those work fabricated helical dielectric elastomer actuators with helical compliant electrodes interposed in an elastomeric insulator. Although an analytical electromechanical model was described, it was applicable only for relatively small strains and the elastomer was designed as a linearly elastic body. It is desirable to consider large strains for better prediction of the performance of the actuator. We begin our analysis by considering the 3D actuator as a purely hyperelastic model with no viscoelastic effects. The constructed mathematical concepts show the displacement, model capabilities, and also overall functionality of the HDEA. The electromechanical coupling of the actuator is modeled to produce a history of the actuator’s strain response for specific activation voltages. The performance of the HDEA is also numerically compared using a commercial grade software.

Depending on the electrode material and on the cations, the electrolysis of water starts at significantly higher voltages than the standard potential of the water electrolysis cell, which is 1.23V. We present the simple methodic of determining the "safe" voltage of aqueous IPMCs below what there is no water electrolysis, with the corresponding quantitative data. Higher voltages applied to IPMC cause irreversible formation of platinum oxides and absorption of hydrogen on the platinum electrodes that can change the mechanism of water electrolysis and decrease the minim required voltage of water electrolysis even below the 1.23V.

Ionic Polymer Metal Composites (IPMCs) are known to be compliant, reliable and able to produce a large current when deformed under a wide range of frequencies. In a previous study, our group demonstrated that cylindrical IPMC hair-like transducers can be used as mechano-electrical sensors. In this paper we characterize the sensing performance of the IPMC hair-like sensor and present methodologies on how to increase its sensitivity while reducing its size. Furthermore an array of 4 hair-cell sensors is built and characterized for tactile sensing texture detection.

Ionic Polymer-Metal Composites (IPMC) are useful actuators because of their ability to be fabricated in different shapes and move in various ways. However, the process to produce an IPMC is complicated and takes a few days. To make it possible to mass produce in any desired shape, the fabrication process must be updated. Presented here is a new way of producing the Nafion® base through a spraying method, then the electrode will be plated with spraying method as well. To verify that this method of fabrication produces a Nafion® sample similar to that which is commercially available, a sample that was made using spraying method and N117 purchased from DuPont™ were tested for various characteristics and compared.

Artificial muscle (AM) technology is an excellent candidate for creating cilia-based structures for bio-inspired locomotion, maneuvering, and acoustic systems. We developed an AM based cilia fiber which are soft, flexible, easily shaped and low power consumption. The developed cilium has a diameter of around 200 µm and prepared through polymer injection technique. Nafion was used for base polymer for cilia and fabricated IPMCs via platinum electroless plating process. The prepared cilia were characterized by Fourier transform infrared spectroscopy, differential scanning calorimetry, and thermogravimetric analysis. The 2 point probe was conducted to measure electrode surface resistance of prepared IPMCs. We further characterized the cross-sectional morphology and studied the electromechanical performances (displacement and blocking force) of the prepared IPMC actuators. Also we created prototype mm-sized AM fiber cilia array (3x20) and tested the actuation of AM cilia fiber under external electric field.

The intrinsically conductive polymer polypyrrole is conventionally synthesized as monolithic films that exhibit significant actuation strains when subjected to an applied electric potential. Though numerous linear and bending actuators based on polypyrrole films have been investigated, the limitations inherent to planar film geometries inhibit the realization of more complex behaviours. Hence, three-dimensional polypyrrole structures are sought to greatly expand the potential applications for conductive polymer actuators. This research aims to develop a novel additive manufacturing method for the fabrication of three-dimensional structures of conductive polypyrrole. In this investigation, radiation-curing techniques are employed by means of digital light processing (DLP) technology. DLP is an additive manufacturing technique where programmed light patterns emitted from a dedicated source are used to selectively cure a specially formulated polymer resin. Successive curing operations lead to a layered 3D structure into which fine features may be incorporated. Energy dispersive spectroscopy (EDS) is subsequently employed to examine the unique microstructural features of the resultant 3D printed polymer morphology in order to elucidate the nature of the conductivity. These polymer microstructures are highly desirable since actuation response times are highly dependent on ion transport distances, and hence the ability to fabricate fine features offers a potential mechanism to improve actuator performance.

Dielectric elastomer actuator (DEA) is one of the promising artificial muscles through light weight, high energy density and capability of large actuation stresses and strains. It is well known that a force generated by DEAs is dominated by the Maxwell equation. In other word, there are three ways, thinning, multi-layering and increasing electric permittivity to increase the force generated by DEAs. Even the mechanism is really simple, a difficulty of fabrication prevents many researchers from developing high performance DEAs. In this work, multi layered DEAs with thin lamina are semi automatically fabricated by using air pulse type dispenser. The dispenser is suitable for drawing an elaborate pattern of several type solutions, including organic and water solvent. The most relevant parameter sets of viscosity, depositing pressure, pitch, nozzle scanning speed and number of over coating for depositing CNT electrode solutions and dielectric elastomer solutions are experimentally investigated. In this paper, A fabricated DEA’s performances, i.e. bending displacements and blocking forces are measured and compared with the prediction by an elastic prediction model.

Controllable adhesion is a requirement for a wide variety of applications including robotic manipulation, as well as locomotion including walking, crawling and perching. Electroadhesives have several advantages such as reversibility, low power consumption and controllability based on applied voltage. Most demonstrations of electroadhesive devices rely on fairly rigid materials, which cannot be stretched reversibly, as needed in some applications. We have developed a fast and reliable method for building soft, stretchable electroadhesive pads based on acrylic elastomers and electrodes made of carbon nanotubes. The devices produced were tested pre-deformation and in a stretched configuration. The adhesive force was determined to be in the 0.1 – 3.0 N/cm² range, depending on the adhering surface. The electroadhesive devices were integrated with pre-stretched dielectric elastomer actuators to create a device in which the adhesion force could be tuned by changes in either the applied voltage or total area.

For the processing of dielectric elastomer actuators (DEAs) one promising class of materials are silicones. They are lowcost and easily accessible. At the same time these materials offer unique mechanical, chemical, low temperature, and optical properties. An active field of research is the optimisation of the silicones’ properties by modifying their framework on the structural level. The focus of this work is to improve the actuation performance of DEAs made up from polydimethylsiloxane (PDMS) by incorporating organic dipoles directly into the polymer’s chains as network points. For this purpose, a diallyl functionalised nitroaniline derivative was utilised as crosslinker for appropriate PDMS starting materials. Silicone films with dipole concentrations varying from 0.5wt% to 1.0wt% were manufactured and the chemical, mechanical, electrical, and electromechanical properties of these novel materials were investigated in dependency of the dipole content.

The intractable nature of intrinsically conductive polymers (ICP) leads to practical limitations in the fabrication of ICP-based transducers having complex three-dimensional geometries. Conventional ICP device fabrication processes have focused primarily on thin-film deposition techniques; therefore this study explores novel additive manufacturing processes specifically developed for ICP with the ultimate goal of increasing the functionality of ICP sensors and actuators. Herein we employ automated polymer paste extrusion processes for the direct ink writing of 3D conductive polyaniline (PANI) structures. Realization of these structures is enabled through a modified fused filament fabrication delta robot equipped with an integrated polymer paste extruder. This unique robot-controlled additive manufacturing platform is capable of fabricating high-resolution 3D conductive PANI and has been utilized to produce structures with a minimum feature size of 1.5 mm. The required processability of PANI is achieved by means of a counter-ion induced thermal doping method. Using this method, a viscous paste is formulated as the extrudate and a thermo-chemical treatment is applied post extrusion to finalize the complexation.

Conducting polymer linear actuators, for example sodium dodecylbenzenesulfonate (NaDBS) doped polypyrrole (PPy/DBS), have shown moderate strain and stress. The goal of this work was to increase the obtainable strain and stress by adding additional active material to PPy/DBS. In recent year’s carbide-derived carbon (CDC)-based materials have been applied in actuators; however, the obtained displacement and actuation speed has been low comparing to conducting polymer based actuators. In the present work, a CDC-PPy hybrid was synthesized electrochemically and polyoxometalate (POM) – phosphotungstic acid – was used to attach charge to CDC particles. The CDC-POM served in the presence of NaDBS as an additional electrolyte. Cyclic voltammetry and chronopotentiometric electrochemomechanical deformation (ECMD) measurements were performed in Lithium bis(trifluoromethanesulfonyl)- imide (LiTFSI) aqueous electrolyte. The ECMD measurements revealed that the hybrid CDC-PPy material exhibited higher force and strain in comparison to PPy/DBS films. The new material was investigated by scanning electron microscopy (SEM) to evaluate CDC particle embedding in the polymer network.

The dielectric relaxation processes of polymethyl methacrylates that have been functionalized with Disperse Red 1 (DR1) in the side chain (DR1-co-MMA) were studied with temperature dependent impedance spectroscopy and thermally stimulated depolarization current (TSDC) techniques. Copolymers with dipole contents which varied between 10 mol% and 70 mol% were prepared. All samples showed dipole relaxations above the structural-glass transition temperature (T_g). The β-relaxation of the methyl methacrylate (MMA) repeating unit was most visible in DR1(10%)-co-MMA and rapidly vanishes with higher dipole contents. DSC data reveal an increase of the T_g by 20 °C to 125°C with the inclusion of the dipole into the polymethyl methacrylate (PMMA) as side chain. The impedance data of samples with several DR1 concentrations, taken at several temperatures above T_g, have been fitted with the Havriliak-Negami (HN) function. In all cases, the fits reveal a dielectric response that corresponds to power-law dipolar relaxations. TSDC measurements show that the copolymer can be poled, and that the induced polarization can be frozen by lowering the temperature well below the glass transition. Relaxation strengths ΔƐ estimated by integrating the depolarization current are similar to those obtained from the impedance data, confirming the efficient freezing of the dipoles in the structural glass state.

Previous studies reported that a twisted and coiled polymer actuator (TCA) generates strong force and large stroke by heating. Nylon 6,6 is known to be the most suitable polymer material for TCA because it has high thermal expansion ratio, high softening point and high toughness which is able to sustain gigantic twisting. In order to find the optimal structure of TCA fabricated with silver-coated nylon sewing threads, an equipment for twist-insertion (structuralization), composed of single DC motor, a slider fabricated by 3D printer and a body frame, is developed. It can measure the behaviors of TCAs as well as fabricate TCAs with desired characteristics by structuralizing fibers with controlled rotation per minutes (RPM) and turns. Comparing performances of diverse structures of TCAs, the optimal structure for TCA is found. For the verification of the availability of the optimal TCA, a TCA-driven biomimetic finger is developed. Finally, we successfully demonstrate the flexion/extension of the finger by using the actuation of TCAs.

Highly oriented nylon and polyethylene fibers shrink in length and expand in diameter when heated. Using this property, in this work, for the first time we are introducing a type of bending artificial muscle from nylon filaments such as fishing line. Reversible radius of curvature of 0.23 mm^-1 was achieved with maximum reversible bending amplitude of 115 mm for the nylon bending actuator. Peak force of up to 2040 mN was measured with a catch-state force of up to 40% of the active force. A 3 dB roll-off frequency of around 0.7 Hz was observed in the frequency response of the bending actuator in water.

We present a novel experimental method for qualitative visualization and quantitative characterization of the time-dependent behavior of bending ionic electroactive polymer actuators. The thin fibers, attached to the actuator, represent the surface normal at the given points of the bending actuator. The structure, formed by the skeleton of many adjacent fibers, amplifies the visual overview about the whole actuator. The four coordinates formed by four tips of two fibers enable determining the axial as well as the bending strains of a bending actuator.

We report on a multifunctional four-finger gripper for soft robotics, suitable for performing delicate manipulation tasks. The gripping device is comprised of separately driven gripping and lifting mechanisms, both made from a separate single piece of smart material - ionic capacitive laminate (ICL) also known as artificial muscle. Compared to other similar devices the relatively high force output of the ICL material allows one to construct a device able to grab and lift objects exceeding multiple times its own weight. Due to flexible design of ICL grips, the device is able to adapt the complex shapes of different objects and allows grasping single or multiple objects simultaneously without damage. The performance of the gripper is evaluated in two different configurations: a) the ultimate grasping strength of the gripping hand; and b) the maximum lifting force of the lifting actuator. The ICL is composed of three main layers: a porous membrane consisting of non-ionic polymer poly(vinylidene fluoride-co-hexafluoropropene) (PVdF-HFP), ionic liquid 1-ethyl-3-methylimidazolium trifluoromethane-sulfonate (EMITFS), and a reinforcing layer of woven fiberglass cloth. Both sides of the membrane are coated with a carbonaceous electrode. The electrodes are additionally covered with thin gold layers, serving as current collectors. Device made of this material operates silently, requires low driving voltage (<3 V), and is suitable for performing tasks in open air environment.

Cellular mechanotransduction is crucial for physiological function in the lower urinary tract. The bladder is highly dependent on the ability to sense and process mechanical inputs, illustrated by the regulated filling and voiding of the bladder. However, the mechanisms by which the bladder integrates mechanical inputs, such as intravesicular pressure, and controls the smooth muscles, remain unknown. To date no tools exist that satisfactorily mimic in vitro the dynamic micromechanical events initiated e.g. by an emerging inflammatory process or a growing tumour mass in the urinary tract. More specifically, there is a need for tools to study these events on a single cell level or in a small population of cells. We have developed a micromechanical stimulation chip that can apply physiologically relevant mechanical stimuli to single cells to study mechanosensitive cells in the urinary tract. The chips comprise arrays of microactuators based on the electroactive polymer polypyrrole (PPy). PPy offers unique possibilities and is a good candidate to provide such physiological mechanical stimulation, since it is driven at low voltages, is biocompatible, and can be microfabricated. The PPy microactuators can provide mechanical stimulation at different strains and/or strain rates to single cells or clusters of cells, including controls, all integrated on one single chip, without the need to preprepare the cells. This paper reports initial results on the mechano-response of urothelial cells using the micromechanical stimulation chips. We show that urothelial cells are viable on our microdevices and do respond with intracellular Ca2+ increase when subjected to a micro-mechanical stimulation.

One of the greatest challenges to modern technologies is what to do with them when they go irreparably wrong or come to the end of their productive lives. The convention, since the development of modern civilisation, is to discard a broken item and then procure a new one. In the 20th century enlightened environmentalists campaigned for recycling and reuse (R and R). R and R has continued to be an important part of new technology development, but there is still a huge problem of non-recyclable materials being dumped into landfill and being discarded in the environment. The challenge is even greater for robotics, a field which will impact on all aspects of our lives, where discards include motors, rigid elements and toxic power supplies and batteries. One novel solution is the biodegradable robot, an active physical machine that is composed of biodegradable materials and which degrades to nothing when released into the environment. In this paper we examine the potential and realities of biodegradable robotics, consider novel solutions to core components such as sensors, actuators and energy scavenging, and give examples of biodegradable robotics fabricated from everyday, and not so common, biodegradable electroactive materials. The realisation of truly biodegradable robots also brings entirely new deployment, exploration and bio-remediation capabilities: why track and recover a few large non-biodegradable robots when you could speculatively release millions of biodegradable robots instead? We will consider some of these exciting developments and explore the future of this new field.

Soft robots are gaining in popularity due to their unique attributes such as low weight, compliance, flexibility and diverse range in motion types. This paper illustrates soft robots and actuators which are developed using dielectric elastomer. These developments include a jellyfish robot, a worm like robot and artificial muscle actuators for jaw movement in a robotic skull. The jellyfish robot which employs a bulged dielectric elastomer membrane has been demonstrated too generate thrust and buoyant forces and can move effectively in water. The artificial muscle for jaw movement employs a pure shear configuration and has been shown to closely mimic the jaw motion while chewing or singing a song. Thee inchworm robot, powered by dielectric elastomer actuator can demonstrate stable movement in one-direction.

Bistable electroactive polymers (BSEP) usually exhibit glass transition that spans a rather broad temperature range and are normally actuated above 70 °C. High actuation temperature limits the BSEP for wearable and personal assistive applications. A phase-changing polymer is synthesized and employed as BSEP having a narrow rigid-to-rubbery transition temperature range. Shape memory effect with both fixation and recovery rate close to 100% was observed. Diaphragm actuators of the BSEP can be electrically actuated at 50 °C up to 70% strain, and the deformed shape was fixed after cooling the BSEP below the transition temperature. The rigid-to-rigid actuation can be repeated for at least 10,000 cycles.

Dielectric elastomer actuators have the advantage of mimicking the salient feature of life: movements in response to stimuli. In this paper we explore application of dielectric elastomer actuators to artificial muscles. These artificial muscles can mimic natural masseter to control jaw movements, which are key components in facial expressions especially during talking and singing activities. This paper investigates optimal design of the dielectric elastomer actuator. It is found that the actuator with embedded plastic fibers can avert electromechanical instability and can greatly improve its actuation. Two actuators are then installed in a robotic skull to drive jaw movements, mimicking the masseters in a human jaw. Experiments show that the maximum vertical displacement of the robotic jaw, driven by artificial muscles, is comparable to that of the natural human jaw during speech activities. Theoretical simulations are conducted to analyze the performance of the actuator, which is quantitatively consistent with the experimental observations.

Dielectric elastomers (DEs) have been extensively studied as DE actuators, DE generators, and DE sensors. Compared with DE actuators and generators, DE sensing application has the advantage that it is no need for high voltage. However, to realize the high sensitivity of the DE sensor, a well-designed structure is essential. A typical DE sensor consists of DE membrane covered by compliant electrodes on both sides. Expanding in the area and shrinking in the thickness of DE membrane subjected to external force will lead to the increasement of the capacitance. We propose a novel DE sensor to detect compressive force. The DE sensor consists of three layers. The two layers of outside can penetrate each other to deform the middle layer and achieve high sensitivity for compressive force measurement. This sensor consists of a series of sensor elements made of DE membrane with out-of-plane deformation. Each sensor element experiences highly inhomogeneous large deformation to obtain high sensitivity. We conduct the experiment to optimize the performance of the sensor element, and also the corresponding theoretical analysis is developed. The effects of the prestretches and the aspect ratios of the sensor element on the sensitivity are achieved. The soft sensor composed of a series of such sensor elements may comply with complicated surfaces and can be used to detect both the total value and the distribution of the compressive force exerted on the surface. Furthermore, the reliability of the sensor element is studied by additional experimental investigation. The experiment shows that the sensor element operates steadily after 2000 cyclic loadings. This study provides guidance for the design and performance analysis of soft sensors. This work has been published in the Journal of Applied Mechanics, 82(10), No. 101004 (2015).

In this contribution we present recent findings of our efforts to qualify the so called Aerosol-Jet-Printing process as an additive manufacturing approach for stacked dielectric elastomer actuators (DEA). With the presented system we are able to print the two essential structural elements dielectric layer and electrode in one machine. The system is capable of generating RTV-2 silicone layers made of Wacker Elastosil P 7670. Therefore, two aerosol streams of both precursor components A and B are generated in parallel and mixed in one printing nozzle that is attached to a 4-axis kinematic. At maximum speed the printing of one circular Elastosil layer with a calculated thickness of 10 μm and a diameter of 1 cm takes 12 seconds while the process keeps stable for 4.5 hours allowing a quite high overall material output and the generation of numerous silicone layers. By adding a second printing nozzle and the infrastructure to generate a third aerosol, the system is also capable of printing inks with conductive particles in parallel to the silicone. We have printed a reduced graphene oxide (rGO) ink prepared in our lab to generate electrodes on VHB 4905, Elastosil foils and finally on Aerosol-Jet-Printed Elastosil layers. With rGO ink printed on Elastosil foil, layers with a 4-point measured sheet resistance as low as 4 kΩ can be realized leaving room for improving the electrode printing time, which at the moment is not as good as the quite good time-frame for printing the silicone layers. Up to now we have used the system to print a fully functional two-layer stacked DEA to demonstrate the principle of continuously 3D printing actuators.

Optical transparency of an indium-tin-oxide (ITO) thin film depends on its topography. Wrinkling of ITO thin film can reduce normal transmittance or visibility by scattering the incident light away. In this paper, we study topography change of ITO thin film and its effect on normal transmittance of light. Coating of ITO thin film on adhesive poly-acrylate elastomer forms wrinkles and folds when subjected to mechanical compression and surface buckling. At excessive compression, such as 25% equi-biaxial, folds of the ITO thin film are so deep and convoluted like crumpling of a piece of paper. This crumpled form of ITO thin film can well obscure the light passing even though a flat ITO thin film is transparent. Surprisingly, the crumpled ITO thin film remains continuous and conductive even with 25% equi-biaxial compression despite the fact that ITO is known to be brittle. These crumpled ITO thin films were subsequently used to make compliant electrodes for Dielectric elastomer actuator (DEA). These crumpled ITO thin film can be reversibly unfolded through the DEA’s areal expansion. This DEA with 14.2% equi-biaxially crumpled ITO thin films can produce 37% areal expansion and demonstrate an optical transmittance change from 39.14% to 52.08% at 550nm wavelength.

The blended ion exchange membrane between Nafion and ethylene vinyl alcohol (EVOH) was used for fabrication of the ionic polymer–metal composite (IPMC) to redeem inherent drawbacks of Nafion such as high cost or environment-unfriendliness. EVOH solution was blended in Nafion solution by a volume ratio of 15 and 30 % membranes were prepared through solution casting method. The prepared blended Nafion membranes can be fabricated IPMCs with deposition of platinum electrode onto its surface without crack or delamination. The surface resistance of all prepared IPMCs is measured through 2 point probe. This study investigated the chemical structure and thermal properties of prepared membranes. Moreover, we characterized the cross-section morphology and studied the electromechanical performances (displacement and blocking force) of prepared IPMC actuators. The IPMC actuators with proposed blended Nafion membranes were demonstrated comparable electromechanical performance by significantly reducing the content of Nafion.

The reduction the operation voltage has been the key challenge to realize of dielectric elastomer actuators (DEA) for many years - especially for the application fields of robotics, lens systems, haptics and future medical implants. Contrary to the approach of manipulating the dielectric properties of the electrically activated polymer (EAP), we intend to realize low-voltage operation by reducing the polymer thickness to the range of a few hundred nanometers. A study recently published presents molecular beam deposition to reliably grow nanometer-thick polydimethylsiloxane (PDMS) films. The curing of PDMS is realized using ultraviolet (UV) radiation with wavelengths from 180 to 400 nm radicalizing the functional side and end groups. The understanding of the mechanical properties of sub-micrometer-thin PDMS films is crucial to optimize DEAs actuation efficiency. The elastic modulus of UV-cured spin-coated films is measured by nano-indentation using an atomic force microscope (AFM) according to the Hertzian contact mechanics model. These investigations show a reduced elastic modulus with increased indentation depth. A model with a skin-like SiO₂ surface with corresponding elastic modulus of (2.29 ± 0.31) MPa and a bulk modulus of cross-linked PDMS with corresponding elastic modulus of (87 ± 7) kPa is proposed. The surface morphology is observed with AFM and 3D laser microscopy. Wrinkled surface microstructures on UV-cured PDMS films occur for film thicknesses above (510 ± 30) nm with an UV-irradiation density of 7.2 10^-4 J cm^-2 nm^-1 at a wavelength of 190 nm.

Dielectric elastomer actuators (DEA) are often referred to as artificial muscles due to their high specific continuous power, which is comparable to that of human skeletal muscles, and because of their millisecond response time. We intend to use nanometer-thin DEA as medical implant actuators and sensors to be operated at voltages as low as a few tens of volts. The conductivity of the electrode and the impact of its stiffness on the stacked structure are key to the design and operation of future devices. The stiffness of sputtered Au electrodes on polydimethylsiloxane (PDMS) was characterized using AFM nanoindentation techniques. 2500 nanoindentations were performed on 10 x 10 μm² regions at loads of 100 to 400 nN using a spherical tip with a radius of (522 ± 2) nm. Stiffness maps based on the Hertz model were calculated using the Nanosurf Flex-ANA system. The low adhesion of Au to PDMS has been reported in the literature and leads to the formation of Au-nanoclusters. The size of the nanoclusters was (25 ± 10) nm and can be explained by the low surface energy of PDMS leading to a Volmer-Weber growth mode. Therefore, we propose (3-mercaptopropyl)trimethoxysilane (MPTMS) as a molecular adhesive to promote the adhesion between the PDMS and Au electrode. A beneficial side effect of these self-assembling monolayers is the significant improvement of the electrode’s conductivity as determined by four-point probe measurements. Therefore, the application of a soft adhesive layer for building a dielectric elastomer actuator appears promising.

Dielectric elastomer actuators (DEA) are one of the best candidate materials for next generation of robotic actuators, soft sensors and artificial muscles due to their fast response, mechanical robustness and compliance. However, high voltage requirements of DEAs have impeded their potential to become widely used in such applications. In this study, we propose a method for fabrication of silicon based multilayer DEA fibers composed of microlevel dielectric layers to improve the actuation ratios of DEAs at lower voltages. A multi-walled carbon nanotube - polydimethylsiloxane (MWCNT/PDMS) composite was used to fabricate mechanically compliant, conductive parallel plates and electrode connections for the DEA actuators. Active surface area and layer thickness were varied to study the effects of these parameters on actuation ratio as a function of applied voltage. Different structures were fabricated to assess the flexibility of the fabrication method for specific user-end applications.

With advantages of low driving voltage, good flexibility and high electromechanical efficiency, ionic polymer-metal composites (IPMCs), which are one of the most attractive smart materials, have been research hotspot in actuators, sensors and artificial muscles. However, a serious drawback of little deformation of thick IPMC actuator limits its application. In this paper, we fabricated thick porous Nafion membranes by freeze-drying process. A series of Thermogravimetric analyses (TGA), Field emission scanning electron microscopy (FE-SEM) and Water uptake (WUP) tests were performed to examine the validity of the freeze-drying process and the pore size and the porosity. Then, the porous IPMCs were fabricated with the freeze-drying processed Nafion membranes by the solution casting and reducing plating. Finally, the IPMC actuators with the dimensions of 25× 5× 1 in millimeters were achieved and tested. The terminal deformation of the porous IPMC actuator increased by 739.7%, compared with the ordinary IPMC actuator with the same dimensions under the driving voltage of 2VDC.

Ionic electro-active polymer (iEAP) actuators are composite materials that change their mechanical properties in response to external electrical stimulus. The interest in these devices is mainly driven by their capability to generate biomimetic movements, and their potential use in soft robotics. The driving voltage of an iEAP-actuator (0.5… 3 V) is at least an order of magnitude lower than that needed for other types of electroactive polymers. To apply iEAP-actuators in potential real-world applications, the capability of operating in different environments (open air, different solvents) must be available. In their natural form, the iEAP-actuators are capable of interacting with the surrounding environment (evaporation of solvent from the electrolyte solution, ion or solvent exchange, humidity effects), therefore, for prevention of unpredictable behavior of the actuator and the contamination of the environment, encapsulation of the actuator is needed. The environmental contamination aspect of the encapsulation material is substantial when selecting an applicable encapsulant. The suitable encapsulant should form thin films, be light in weight, elastic, fit tightly, low cost, and easily reproducible. The main goal of the present study is to identify and evaluate the best potential encapsulation techniques for iEAPactuators. Various techniques like thin film on liquid coating, dip coating, hot pressing, hot rolling; and several materials like polydimethylsiloxane, polyurethane, nitrocellulose, paraffin-composite-films were investigated. The advantages and disadvantages of the combinations of the above mentioned techniques and materials are discussed. Successfully encapsulated iEAP-actuators gained durability and were stably operable for long periods of time under ambient conditions. The encapsulation process also increased the stability of the iEAP-actuator by minimizing the environment effects. This makes controlling iEAP-actuators more straight-forward and reliable since there is no need to take the environmental factors like relative humidity and/or gas circulation into account.

The presentation focuses on the performances of flexible all-polymer electroactive actuators under space-hazardous environmental factors in laboratory conditions. These bending actuators are based on high molecular weight nitrile butadiene rubber (NBR), poly(ethylene oxide) (PEO) derivative and poly(3,4-ethylenedioxithiophene) (PEDOT). The electroactive PEDOT is embedded within the PEO/NBR membrane which is subsequently swollen with an ionic liquid as electrolyte. Actuators have been submitted to thermal cycling test between -25 to 60°C under vacuum (2.4 10^-8 mbar) and to ionizing Gamma radiations at a level of 210 rad/h during 100 h. Actuators have been characterized before and after space environmental condition ageing. In particular, the viscoelasticity properties and mechanical resistance of the materials have been determined by dynamic mechanical analysis and tensile tests. The evolution of the actuation properties as the strain and the output force have been characterized as well. The long-term vacuuming, the freezing temperature and the Gamma radiations do not affect significantly the thermomechanical properties of conducting IPNs actuators. Only a slight decrease on actuation performances has been observed.

Ionic polymer-metal composites (IPMCs) have inherent underwater sensing and actuation properties. They can be used as sensors to collect flow information. Inspired by the hair-cell mediated receptor in the lateral line system of fish, the impact of a flexible, cupula-like structure on the performance of IPMC flow sensors is experimentally explored. The fabrication method to create a silicone-capped IPMC sensor is reported. Experiments are conducted to compare the sensing performance of the IPMC flow sensor before and after the PDMS coating under the periodic flow stimulus generated by a dipole source in still water and the laminar flow stimulus generated in a flow tank. Experimental results show that the performance of IPMC flow sensors is significantly improved under the stimulus of both periodic flow and laminar flow by the proposed silicone-capping.

A three-dimensional (3D) fused filament additive manufacturing (AM) technique (3D printing) is described for creating ionic polymer-metal composites (IPMC) actuators. The 3D printing technique addresses some of the limitations of existing manufacturing processes for creating IPMCs, which includes limited shapes and sizes and time-consuming steps. In this paper, the 3D printing process is described in detail, where first a precursor material (non-acid Nafion precursor resin) is extruded into a thermoplastic filament for 3D printing. A custom designed 3D printer is described which utilizes the filament to manufacture custom-shaped IPMC actuators. The 3D printed samples are hydrolyzed in an aqueous solution of potassium hydroxide and dimethyl sulfoxide, followed by application of platinum electrodes. The performance of 3D-printed IPMC actuators with different infill patterns are characterized. Specifically, experimental results are presented for electrode resistance, actuation performance, and overall effective actuator stiffness for samples with longitudinal (0 degrees) and transverse (90 degrees) infill pattern.

Wearable assistive devices are the future of rehabilitation therapy and bionic limb technologies. Traditional electric, hydraulic, and pneumatic actuators can provide the precise and powerful around-the-clock assistance that therapists cannot deliver. However, they do so in the confines of highly controlled factory environments, resulting in actuators too rigid, heavy, and immobile for wearable applications. In contrast, biological skeletal muscles have been designed and proven in the uncertainty of the real world. Bioinspired artificial muscle actuators aim to mimic the soft, slim, and self-sensing abilities of natural muscle that make them tough and intelligent. Fluidic artificial muscles are a promising wearable assistive actuation candidate, sharing the high-force, inherent compliance of their natural counterparts. Until now, they have not been able to self-sense their length, pressure, and force in an entirely soft and flexible system. Their use of rigid components has previously been a requirement for the generation of large forces, but reduces their reliability and compromises their ability to be comfortably worn. We present the unobtrusive integration of dielectric elastomer (DE) strain and pressure sensors into a soft Peano fluidic muscle, a planar alternative to the relatively bulky McKibben muscle. Characterization of these DE sensors shows they can measure the full operating range of the Peano muscle: strains of around 18% and pressures up to 400 kPa with changes in capacitance of 2.4 and 10.5 pF respectively. This is a step towards proprioceptive artificial muscles, paving the way for wearable actuation that can truly feel its environment.

Since the late 1990’s dielectric elastomers (DEs) have been investigated for their use as sensors. To date, there have been some impressive developments: finger displacement controls for video games and integration with medical rehabilitation devices to aid patient recovery. It is clear DE sensing is well established for dry applications, the next frontier, however, is to adapt this technology for the other 71% of the Earth’s surface. With proven and perhaps improved water resistance, many new applications could be developed in areas such as diver communication and control of underwater robotics; even wearable devices on land must withstand sweat, washing, and the rain. This study investigated the influence of fresh and salt water on DE sensing. In particular, sensors have been manufactured with waterproof connections and submersed in fresh and salt water baths. Temperature and resting capacitance were recorded. Issues with the basic DE sensor have been identified and compensated for with modifications to the sensor. The electrostatic field, prior and post modification, has been modeled with ANSYS Maxwell. The aim of this investigation was to identify issues, perform modifications and propose a new sensor design suited to wet and underwater applications.

Dielectric elastomer sensors for the measurement of compression loads with high sensitivity are described. The basic design of the sensors exhibits two profiled surfaces between which an elastomer film is confined. All components of the sensor were prepared with silicone whose stiffness can be varied in a wide range. Depending on details of the sensor design, various effects contribute to the enhancement of the capacitance. The intermediate elastomer film is stretched upon compression and electrode layers on the elastomer profiles and in the elastomer film approach each other. Different designs of the pressure sensor give rise to very different sensor characteristics in terms of the dependence of electric capacitance on compression force. Due to their inherent flexibility, the pressure sensors can be used on compliant substrates such as seats or beds or on the human body. This gives rise to numerous possible applications. The contribution describes also some examples of possible sensor applications. A glove was equipped with various sensors positioned at the finger tips. When grabbing an object with the glove, the sensors can detect the gripping forces of the individual fingers with high sensitivity. In a demonstrator of the glove equipped with seven sensors, the capacitances representing the gripping forces are recorded on a display. In another application example, a lower limb prosthesis was equipped with a pressure sensor to detect the load on the remaining part of the leg and the load is displayed in terms of the measured capacitance. The benefit of such sensors is to detect an eventual overload in order to prevent possible pressure sores. A third example introduces a seat load sensor system based on four extended pressure sensor mats. The sensor system detects the load distribution of a person on the seat. The examples emphasize the high performance of the new pressure sensor technology.

When we communicate face to face, we subconsciously engage our whole body to convey our message. In telecommunication, e.g. during phone calls, this powerful information channel cannot be used. Capturing nonverbal information from body motion and transmitting it to the receiver parallel to speech would make these conversations feel much more natural. This requires a sensing device that is capable of capturing different types of movements, such as the flexion and extension of joints, and the rotation of limbs. In a first embodiment, we developed a sensing glove that is used to control a computer game. Capacitive dielectric elastomer (DE) sensors measure finger positions, and an inertial measurement unit (IMU) detects hand roll. These two sensor technologies complement each other, with the IMU allowing the player to move an avatar through a three-dimensional maze, and the DE sensors detecting finger flexion to fire weapons or open doors. After demonstrating the potential of sensor fusion in human-computer interaction, we take this concept to the next level and apply it in nonverbal communication between humans. The current fingerspelling glove prototype uses capacitive DE sensors to detect finger gestures performed by the sending person. These gestures are mapped to corresponding messages and transmitted wirelessly to another person. A concept for integrating an IMU into this system is presented. The fusion of the DE sensor and the IMU combines the strengths of both sensor types, and therefore enables very comprehensive body motion sensing, which makes a large repertoire of gestures available to nonverbal communication over distances.

Ionic polymer-metal composite (IPMC) actuators and sensors have been developed and modeled over the last two decades for use as soft-robotic deformable actuators and sensors. IPMC devices have been suggested for application as underwater actuators, energy harvesting devices, and medical devices such as in guided catheter insertion. Another interesting application of IPMCs in flow sensing is presented in this study. IPMC interaction with fluid flow is of interest to investigate the use of IPMC actuators as flow control devices and IPMC sensors as flow sensing devices. An organized array of IPMCs acting as interchanging sensors and actuators could potentially be designed for both flow measurement and control, providing an unparalleled tool in maritime operations. The underlying physics for this system include the IPMC ion transport and charge fundamental framework along with fluid dynamics to describe the flow around IPMCs. An experimental setup for an individual rectangular IPMC sensor with an externally controlled fluid flow has been developed to investigate this phenomenon and provide further insight into the design and application of this type of device. The results from this portion of the study include recommendations for IPMC device designs in flow control.

Dielectric elastomers exhibit extended capabilities as flexible sensors for the detection of load distributions, pressure or huge deformations. Tracking the human movements of the fingers or the arms could be useful for the reconstruction of sporting gesture, or to control a human-like robot. Proposing new measurements methods are addressed in a number of publications leading to improving the sensitivity and accuracy of the sensing method. Generally, the associated modelling remains simple (RC or RC transmission line). The material parameters are considered constant or having a negligible effect which can lead to serious reduction of accuracy. Comparisons between measurements and modelling require care and skill, and could be tricky. Thus, we propose here a comprehensive modelling, taking into account the influence of the material properties on the performances of the dielectric elastomer sensor (DES). Various parameters influencing the characteristics of the sensors have been identified: dielectric constant, hyper-elasticity. The variations of these parameters as a function of the strain impact the linearity and sensitivity of the sensor of few percent. The sensitivity of the DES is also evaluated changing geometrical parameters (initial thickness) and its design (rectangular and dog-bone shapes). We discuss the impact of the shape regarding stress. Finally, DES including a silicone elastomer sandwiched between two high conductive stretchable electrodes, were manufactured and investigated. Classic and reliable LCR measurements are detailed. Experimental results validate our numerical model of large strain sensor (>50%).

Dielectric elastomers (DE) are a subgroup of electroactive polymers which may be used as soft transducers. Such soft transducers exhibit high energy density and silent operation, which makes them desirable for life-like robotic systems such as a robotic hand. A robotic hand must be able to sense the object being manipulated, in terms of normal and shear force being applied, and note when contact has been achieved or lost. To this end, a dielectric elastomer actuator (DEA) with integrated tactile sensing has been developed to provide simultaneous actuation and sensing. The tactile sensing dielectric elastomer actuator consists of a unimorph-type structure, where the active portion is a laminate of alternating DE and electrode material which expands under applied voltage, and the sensing portion is a stiffer sensing dielectric elastomer which has no electrical connection to the active portion. Under applied voltage, the deformation of the active portion expands but is constrained on one side by the sensing portion, resulting in bending actuation. The sensing portion is a DE with electrodes patterned to form 2x2 capacitive sensing arrays. Dome-shaped bumps positioned over the sensing arrays redistribute tactile forces onto the sensor segments, so that measurement of the capacitance change across the array allows for reconstruction of magnitude and direction of the incoming force.

Transducers based on dielectric elastomers (DE) are able to fulfill various requirements as generator, sensor and actuator applications. Depending on the application their design implementation differs. An advantageous transducer topology to improve the strain and force are DE stack-transducers which consist of multiple layers of DE films coated with a compliant electrode. Their actuation behavior is strongly depended on the total number of layers and the mechanical interface to its environment. Considering different application cases customized actuator designs are proposed and the utilized manufacturing process is briefly presented. Within this publication a FE model is used to simulate the deformation under consideration of various mechanical boundaries. After-wards, experimental investigations are conducted to verify the simulation results. Actuator configurations with different mechanical interfaces are analyzed regarding their static actuation behavior. Furthermore, dynamic tests were conducted to show differences between actuators made from silicone and polyurethane (PUR). In summary, the tests confirm the results of the FE analysis and provide promising results appropriate for various future applications.

This work reports on the modelling and control of ionic electroactive polymer actuators with electrodes based on nanoporous carbon, which are working in ambient environment. The model incorporates the humidity level value as one of the input parameters, and so captures the environment-dependent dynamics of the actuator. The effect of ambient humidity on the actuators is studied through the frequency response analysis and is followed by neural network method of modelling. A closed loop set point tracking control system based on gain scheduled model predictive control is designed and developed for position control of actuator and is verified experimentally. The developed model and controller is capable to predict and control the actuators at under the humidity conditions varying in the range of 3% - 97%.

The research efforts for silicone based elastomers with high dielectric permittivity (Ɛ’) intensified significantly in the last years since such materials would allow the construction of dielectric elastomer actuators (DEA) with low operation voltages. Polar groups can be introduced to elastomers to adjust their permittivity. The results obtained regarding the functionalization of silicones with polar nitrile (CN) and trifluoropropyl (CF₃) groups are presented. Those with CN groups were synthesized via anionic polymerization of nitrile containing cyclosiloxanes or via a post-polymerization modification of functional polysiloxanes. Polysiloxanes containing CF₃ groups were prepared by anionic copolymerization of 1,3,5-tris(3,3,3-trifluoropropyl)-1,3,5-trimethylcyclosiloxane with octamethylcyclotetrasiloxane. Importantly, we have found that all polysiloxanes have glass transition temperatures (Tg) well below room temperature (<-50°C). This ensures that the materials turn into true elastomers after cross-linking. In addition to this, a linear increase in Ɛ’ with increasing content of polar groups was observed with maximum values of Ɛ’ = 18 and Ɛ’ = 8.8 for polysiloxanes modified at every repeating unit with either CN or CF₃ groups, respectively.

TiO₂ nanomaterials were prepared by a sol-gel derived electrospinning, calcination from 500°C to 650°C, and subsequent mechanical grinding to investigate the effect of calcination temperature on crystal structure, crystallinity, and photocatalytic activity of methylene blue (MB). XRD results indicated that TiO₂ nanorods calcined at 500°C is composed of anatase TiO₂ only. However, mixed crystals of anatase and rutile were observed for TiO₂ calcined above 550°C. Higher MB degradation was found for the TiO₂ nanorods calcined at 550°C probably due to the mixed crystals and larger surface area. However, the improved photocatalytic activity was achieved for TiO₂ nanotube due to the synergic combinations of mixed crystals, larger specific surface area, and light trapping effect.

An ionic polymer material can generate electrical potential and function as a bio-sensor under a non-uniform deformation. Ionic polymer-metal composite (IPMC) is a typical flexible ionic polymer sensor material. A multi-physical sensing model is presented at first based on the same physical equations in the physical model for IPMC actuator we obtained before. Under an applied bending deformation, water and cation migrate to the direction of outside electrode immediately. Redistribution of cations causes an electrical potential difference between two electrodes. The cation migration is strongly restrained by the generated electrical potential. And the migrated cations will move back to the inner electrode under the concentration diffusion effect and lead to a relaxation of electrical potential. In the whole sensing process, transport and redistribution of charge and mass are revealed along the thickness direction by numerical analysis. The sensing process is a revised physical process of the actuation, however, the transport properties are quite different from those of the later. And the effective dielectric constant of IPMC, which is related to the morphology of the electrode-ionic polymer interface, is proved to have little relation with the sensing amplitude. All the conclusions are significant for ionic polymer sensing material design.

Recently, fishing line artificial muscle has been developed and is paid much attention due to the properties such as large contraction, light weight and extremely low cost. Typical fishing line artificial muscle is made from Nylon thread and made by just twisting the polymer. In this paper, because of the structure of the actuator, such actuators may be named as coiled polymer actuators (CPAs). In this paper, a CPA is fabricated from commercial Nylon fishing line and Ni-Cr alloy (Nichrome) wire is wound around it. The CPA contracts by the Joule heat generated by applied voltage to the Nichrome wire. For designing the control system, a simple model is proposed. According to the physical principle of the actuator, two first-order transfer functions are introduced to represent the actuator model. One is a system from the input power to the temperature and the other is a system from the temperature to the deformation. From the system identification result, it is shown that the dominant dynamics is the system from the input power to the temperature. Using the developed model, position control of the voltage-driven CPA is discussed. Firstly, the static nonlinearity from the voltage to the power is eliminated. Then, a 2-DOF PID controller which includes an inversion-based feed forward controller and a PID controller are designed. In order to demonstrate the proposed controller, experimental verification is shown.

Recently, Ionic polymer metal composites (IPMCs), becoming an increasingly popular material, are used as soft actuators for its inherent properties of light weight, flexibility, softness, especial efficient transformation from electrical energy to mechanical energy with large bending strain response to low activation voltage. This paper mainly focuses on the suitable conditions for surface-roughening of Nafion 117 membrane. The surfaces of Nafion membrane were pretreated and optimized by sandblasting, mainly considering the change of sandblasting time and powder size. The modified surfaces are characterized in terms of their topography from the confocal laser scanning microscope (CLSM) and SEM. Then, the detailed change in surface and interfacial electrodes and performances for IPMC actuators prepared by the roughened membranes, were measured and discussed. The results show that an optimized roughening condition with large interface area (capacitance) can effectively increases the electromechanical responses of IPMC.

In this paper, we developed a new kind of ionic polymer metal composite (IPMC) actuator by doping sulfonated carbon nanotube (SCNT) into Nafion matrix to overcome some major drawbacks, such as low output force and short air-operation time, which restrict applications of conventional Nafion IPMC actuators. Firstly, SCNT was synthesized by coupled reaction of multi-walled carbon nanotubes and azo compounds and then doped into Nafion matrix by casting method. Subsequently, several key parameters of the SCNT-reinforced Nation matrix, water uptake ratio and equivalent stiffness, were revealed and the inner morphology of the membranes were observed by scanning electron microscopy. Finally, the effects of the SCNT on the electromechanical properties of IPMC actuators, especially the actuating performance, were evaluated experimentally and analyzed systematically. The results showed that SCNT was evenly dispersed in Nafion matrix and a small amount of SCNT could improve the performance of IPMC actuators significantly.

Dielectric elastomer sensors show great potential for wearable electronics and mechatronic applications. However, these sensors have some deficiencies in their appearance and low sensitivity to compressive force measurements. We demonstrate a novel dielectric elastomer sensor enabled by ionic liquid that has fully transparent appearance, low resistivity and the capacity of actuation at large-scale frequencies. We investigate the basic mechanical behaviors of the sensor experimentally. It is noted that the sensor has a remarkable sensitivity to measure compressive force, which is higher than the existing stacked dielectric elastomer sensors.

To design systems utilizing dielectric elastomer transducers (DET) models are necessary to describe the behaviour of the DET and assess the system performance in advance. For basic set-ups simple analytical models or lumped parameter models are available and provide reasonable results. For more complex set-ups these models only allow a rough estimation of the system performance, not accurate enough to achieve an optimal system design. Therefore system designers typically resort to numerical simulation tools. Commercially available tools and models specialize on either electrical or mechanical domain thus simplifying or even neglecting effects in the other domain respectively. In this work we present a simulation tool taking into account the transient electrical and mechanical behaviour of DET under different mechanical load conditions and electrical driving frequencies. Our model can describe transient electrical and mechanical behaviour, such as electrical resistance, mechanical hyperelastic and viscosity of the electrodes and dielectric material. Model parameters are derived from measurements of the dielectric and the electrode resistance as well as e.g. the materials Young’s modulus. The results from the simulation are compared to simple lumped parameter based models.

Tunable, optical microcavities (MC) gain more and more importance for display, laser or other optical applications. The setup of dielectric elastomer actuators (DEA) enables a simple integration of an optical cavity, since reflective electrodes can confine a cavity that is filled with a transparent elastomer. Applying a voltage to the electrodes leads to squeezing of the elastomer and, due to the cavity thickness decrease, the resonator modes of interfering light changes. In this work we present an electrically tunable, optical MC based on ultra-soft poly(dimethylsiloxane) (PDMS). The PDMS gel is coated on a glass substrate with a distributed Bragg reflector, an ITO bottom electrode and a flexible, highly reflective metal electrode and mirror on top. The usage of an ultra-soft PDMS gel, with a storage modulus of about 1kPa, allows to decrease the operating voltage down to a few hundred or even several ten volts. The critical step of fabrication is the metallization of the PDMS gel layer that requires a previous oxidizing surface activation to gain reflective and conductive silver based layers on top. Therefore, the effects of oxygen plasma and UV/ozone treatment on PDMS and the created metal layer were investigated intensively. The performance of the electrically tunable, optical MC is tremendously dependent from an adequate surface activation and structuring of the top electrodes considering the mirror displacement and activation voltage. Here we could show that tunable MCs based on oxygen plasma activated PDMS show a homogenous and high thickness decrease up to 70% at 200V.

Ionic Polymer-Metal Composite (IPMC) actuators have been attracting a growing interest in extensive applications, which consequently raises the demands on the accuracy of its theoretical modeling. For the last few years, rough landscape of the interface between the electrode and the ionic membrane of IPMC has been well-documented as one of the key elements to ensure a satisfied performance. However, in most of the available work, the interface morphology of IPMC was simplified with structural idealization, which lead to perplexity in the physical interpretation on its interface mechanism. In this paper, the quasi-random rough interface of IPMC was described with fractal dimension and scaling parameters. And the electro-chemical field was modeled by Poisson equation and a properly simplified Nernst–Planck equation set. Then, by simulation with Finite Element Method, a comprehensive analysis on he inner mass and charge transportation in IPMC actuators with different fractal interfaces was provided, which may be further adopted to instruct the performance-oriented interface design for ionic electro-active actuators. The results also verified that rough interface can impact the electrical and mechanical response of IPMC, not only from the respect of the real surface increase, but also from mass distribution difference caused by the complexity of the micro profile.

High speed, low flying and high Maneuvering, Good methods are needed in high speed Turn maneuvering tracking algorithm. An adaptive version of the H∞ filter which has a practical real-time implementations developed in the paper and it is demonstrated that it has superior worst case performance when compared with the standard Kaman filter to target tracking. when used in turn maneuvering tracking algorithm, the new filter yields improved worst-case performance in the case of model uncertainties. The simulation results indicate that the real-tine maneuvering target turn tracking algorithm can maintain track under severe correlates maneuvers.

Ionic polymer-metal composites (IPMCs) have intrinsic sensing and actuation properties. An IPMC sensor typically has the beam shape and responds to bending deflections only. Recently tubular IPMCs have been proposed for omnidirectional sensing of bending stimuli. In this paper we report, to our best knowledge, the first study on torsion sensing with tubular IPMCs. In particular, a dynamic, physics-based model is presented for a tubular IPMC sensor under pure torsional stimulus. With the symmetric tubular structure and the pure torsion condition, the stress distribution inside the polymer only varies along the radial direction, resulting in a one-dimensional model. The dynamic model is derived by analytically solving the governing partial differential equation, accommodating the assumed boundary condition that the charge density is proportional to the mechanically induced stress. Experiments are further conducted to estimate the physical parameters of the proposed model.

Dielectric electroactive polymers have demonstrated their significant potential in a variety of applications due to their material strength and elastomeric material properties. Mechanical pre-strain has been shown to enhance material actuation potential significantly. However, with this enhancement comes sacrifices. Mechanical pre-strain imposes a stiff mechanical boundary on the dielectric material in order to maintain the strain. In this research, investigations were made into the mechanisms of mechanical pre-strain and into alternate pre-strain methods. These studies discovered alternate methods capable of producing enhanced pre-strains and final actuation without the addition of the solid strain boundary.

This paper proposes a flexible dual mode tactile and proximity sensor using Carbon Microcoils (CMCs). The sensor consists of a Flexible Printed Circuit Board (FPCB) electrode layer and a dielectric layer of CMCs composite. In order to avoid damage from frequent contacts, the sensor has all electrodes on the same plane and a polymer covering is placed on the top of the sensor. CMCs can be modeled as complex LCR circuit and the sensitivity of the sensor highly depends on the CMC content. Proper CMC content is experimentally investigated and applied to make the CMCs composite for the dielectric layer. The CMC sensor measures the capacitance for tactile stimulus and inductance for proximity stimulus. A prototype with a size of 30 × 30 × 0.6 𝑚𝑚³, is manufactured and its feasibility is experimentally validated.

Human uses various sensational information for identifying an object. When contacting an unidentified object with no vision, tactile sensation provides a variety of information to perceive. Tactile sensation plays an important role to recognize a shape of surfaces from touching. In robotic fields, tactile sensation is especially meaningful. Robots can perform more accurate job using comprehensive tactile information. And in case of using sensors made by soft material like silicone, sensors can be used in various situations. So we are developing a tactile sensor with soft materials. As the conventional robot operates in a controlled environment, it is a good model to make robots more available at any circumstance that sensory systems of living things. For example, there are lots of mechanoreceptors that each of them has different roles detecting simulation in side of human skin tissue. By mimicking the mechanoreceptor, a sensory system can be realized more closely to human being. It is known that human obtains roughness information through scanning the surface with fingertips. During that times, subcutaneous mechanoreceptors detect vibration. In the same way, while a robot is scanning a surface of object, a roughness sensor developed detects vibrations generated between contacting two surfaces. In this research, a roughness sensor made by an elastomer was developed and experiment for perception of objects was conducted. We describe means to compare the roughness of objects with a newly developed sensor.

Vacuum grippers are often used for the handling of wafers and small devices. In order to evacuate the gripper, a gas flow is created that can harm the micro structures on the wafer. A promising alternative to vacuum grippers could be adhesive grippers with switchable adhesion. There have been some publications of gecko-inspired adhesive devices. Most of these former works consist of a structured surface which adheres to the object manipulated and an actuator for switching the adhesion. Until now different actuator principles have been investigated, like smart memory alloys and pneumatics. In this work for the first time dielectric elastomer stack transducers (DEST) are combined with a structured surface. DESTs are a promising new transducer technology with many applications in different industry sectors like medical devices, human-machine-interaction and soft robotics. Stacked dielectric elastomer transducers show thickness contraction originating from the electromechanical pressure of two compliant electrodes compressing an elastomeric dielectric when a voltage is applied. Since DESTs and the adhesive surfaces previously described are made of elastomers, it is self-evident to combine both systems in one device. The DESTs are fabricated by a spin coating process. If the flat surface of the spinning carrier is substituted for example by a perforated one, the structured elastomer surface and the DEST can be fabricated in one process. By electrical actuation the DEST contracts and laterally expands which causes the gecko-like cilia to adhere on the object to manipulate. This work describes the assembly and the experimental results of such a device using switchable adhesion. It is intended to be used for the handling of glass wafers.

Currently, dielectric elastomer actuators (DEA) are mainly based on micrometer-thin polymer films and require operating voltages of several hundred volts. In medical applications, however, voltages as low as a few tens of volts are required. To this end, we prepared nanometer-thin dielectric elastomer layers. It is demonstrated that alternating current, electro-spray deposition allows for the fabrication of homogenous, flat, nanometer-thin polydimethylsiloxane (PDMS) films. The growth of the PDMS with average number molecular weights ranging from 800 to 62,700 g/mol, at a constant flow rate of 267 nL/s, was in situ monitored by means of spectroscopic ellipsometry. The Cauchy layer model used for data interpretation may only be applied to flat PDMS layers. Thus, in the present study the droplet morphology was also determined by atomic force microscopy. Spectroscopic ellipsometry does allow for the qualitative determination of the thin film morphology. However, for high molecular weight polymers the precise measurement during deposition is challenging. Independent of the molecular weight, the roughness of the deposited PDMS films considerably smoothens during the ultra-violet radiation treatment. After curing, the electro-sprayed nanometer-thin PDMS films are homogeneous enough to qualify for the fabrication of low-voltage DEA.

Screen printing is used as a method for printing electrodes on silicone thin films for the fabrication of dielectric elastomer transducers (DET). This method can be used to manufacture a multitude of patternable designs for actuator and sensor applications, implementing the same method for prototyping as well as large-scale production. The fabrication of DETs does not only require the development of a flexible, highly conductive electrode material, which adheres to a stretched and unstretched silicone film, but also calls for a thorough understanding of the effects of the different printing parameters. This work studies the influence of screen dimensions (open area, mesh thickness) as well as the influence of multiple-layer- printing on the electrode stiffness, electrical resistance and capacitance as well as actuator performance. The investigation was conducted in a custom-built testing device, which enabled an electro-mechanical characterization of the DET, simultaneously measuring parameters such as strain, voltage, current, force, sheet resistance, capacitance and membrane thickness. Magnified pictures of the electrodes will additionally illustrate the effects of the different printing parameters.

Electroactive polymer (EAP) based technologies have shown promise in areas such as artificial muscles, actuator, aerospace, medical and soft robotics. Still challenges remain such as low induced forces and defects-driven electrical breakdown, which impede the practical implementation of this technology. Multilayered or stacked configuration can address the low induced force issue whereas self-clearing can be a technique to improve breakdown limit of EAP based actuators. Self-clearing refers to the partial local breakdown of dielectric medium due to the presence of impurities, which in turn results in the evaporation of some of the metalized electrode. After this evaporation, the impurity is cleared and any current path would be safely cut off, which means the actuator continues to perform. It is a widely studied concept in the capacitor community, while it has not been studied much for EAP technologies. In this paper we report a systematic approach to precondition a silver-metalized electroactive polymer (EAP), more specifically P(VDF-TrFE-CTFE) terpolymer, using self-clearing concept. First, we show improvement in the dielectric breakdown strength of EAP based unimorph actuators after pre-clearing the impurities using low electric field (lower than dielectric breakdown of the terpolymer). Inspired by this improvement, we used Weibull statistics to systematically estimate the self-clearing/ preconditioning field needed to clear the defects. Then electrical breakdown experiments are conducted with and without preconditioning the samples to investigate its effect on the breakdown strength of the sample.