This PDF file contains the front matter associated with SPIE Proceedings Volume 12945, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.

This work presents a novel and innovative design for a dielectric elastomer-based pump with a focus on resonance optimization. Dielectric elastomer pumps are increasingly relevant in fluid transport applications, but their efficiency and control remain critical challenges. This study presents a novel approach to addressing these issues. The proposed design leverages the concept of resonance optimization, a cutting-edge approach that enhances the performance of dielectric elastomer pumps by exploiting their inherent resonant frequencies. The mechanical design is systematically chosen to ensure that the system's resonance matches the pump's working frequency, and when an appropriate electric field is applied, it significantly enhances the pump's efficiency through resonance enhancement. To demonstrate the effectiveness of this approach, a fully functional dielectric elastomer-based pump demonstrator is built and tested. The demonstrator showcases how the systematic selection of mechanical design elements, including pump chamber, pump membrane geometry, biasing mechanism and dielectric elastomer design, combined with resonance optimization, results in an optimized pump adapted to handle different loads effectively. Dielectric elastomers (DEs), known for their exceptional properties such as high-frequency operation, high energy efficiency and the ability to freely tailor geometries to suit specific applications, serve as a keystone in achieving these improvements. By exploiting these characteristics, this innovative approach opens up new possibilities for fluid transport technologies, making it an ideal candidate for applications demanding reliability and low energy consumption. In conclusion, this design approach for DE-based pumps with resonance optimization holds promise for overcoming existing limitations in dielectric elastomer technology in the field of pump applications, presenting a pathway towards more efficient and versatile pump systems.

High strains of the relaxor ferroelectric polymers allows to build efficient actuators. While the mechanical impedance of such actuators can be optimized via their morphology, their practical realization requires flexible and versatile fabrication processes. This work devises an efficient procedure for manufacturing unimorph bending actuators basing on the P(VDF-TrFE-CTFE) electroactive polymer (EAP). The fabrication process consists of inkjet printing the Ag electrodes and stencil printing the active P(VDF-TrFE-CTFE) layer. The effect of constituent layer dimensions and properties are analytically modelled to estimate the optimal morphology for highest strains. Actuators are manufactured on polyethylene naphthalate (PEN) and polyethylene terephthalate (PET) substrates and their performance is characterized. On PET substrate, the EAP layer thicknesses of 5 μm up to 24 μm are studied. The PEN-based actuators achieved up to 759 μm deflections in quasi-static (1 Hz, 560 V_pp) and up to 5.95 mm in resonant operation (52 Hz, 550 V_pp). The PET-based actuators achieved up to 486 μm deflections in quasi-static (1 Hz, 980 V_pp) and up to 4.44 mm in resonant operation (116 Hz, 700 V_pp). These results indicate an up to 123% improvement in quasi-static and 60% resonant actuation strains compared to the previously reported similar actuators. Modelling predicts that significantly larger deflections are feasible when fabricating the transducers with optimized morphology.

From our cell phones to game controllers, haptics – the use of skin stimulation, often in the form of vibrations, to relay information – has expanded its pervasiveness over the last few decades. Most applications leverage low-cost solutions, such as linear resonant and eccentric rotating mass actuators, which are limited in either their bandwidth or response time. However, some time-sensitive applications that require complex representation of the environment, such as obstacle avoidance and emergency response, pose restrictive requirements for haptic technologies. To this end, our team has recently developed a new type of high-performance haptic actuators, based on composites of piezoelectric materials called macro fiber composites (MFCs). The MFCs are glued on an aluminum back, enclosed by a custom-made case, and put in contact with a hollow cylinder, filled with a dense material. The mass in the cylinder allows the tuning of the frequency response of the actuator, toward increasing the amplitude of the response in the frequency range in which skin is most sensitive (10-250 Hz). In this paper, we put forward a detailed characterization of this new type of haptic actuators. First, we experimentally detail their mechanical and piezoelectric response. We then assess their frequency response while varying the mass in the cylinder. Finally, we study how actuators would interact mechanically with the skin. To this end, we conduct experiments with an actuator in contact with a pre-stretched membrane, whose mechanical properties are within the range of variability of human skin. We measure the frequency response of the actuator while varying the pre-stretch level of the membrane, simulating different skin indentations. Our results demonstrate that this new type of actuators can maintain an amplitude over the skin discrimination threshold over a large bandwidth, while offering low latency due to the fast piezoelectric response times.

Urinary incontinence (UI) is prevalent and distressing medical condition affecting millions of patients worldwide. Current treatment options for severe cases often involve surgical intervention, such as the implantation of an artificial urinary sphincter (AUS). However, existing AUS devices have limitations, including mechanical complexity, a risk of complications and have been mainly developed for male patients. In this context, dielectric elastomers actuators (DEAs) often referred as artificial muscles are a promising alternative. This study explores the potential of DEAs as a more efficient and less invasive AUS. Thanks to simulations performed on human urethra and tubular DEA, we designed a tubular DEA with an active thickness of 250 μm a length of 40 mm and an internal radius of 2.5 mm. We demonstrated the capability of this DEA to close the urethra with an internal pressure applied from the bladder varying from 0 to 10 000 Pa. We also demonstrated the capability of opening the urethra with a diameter of 0.58 mm at 10 000 Pa. Those results are promising and prove the potential of using DEAs as an Artificial Urinary Sphincter.

The burden of urinary incontinence is profound, affecting individuals both physically and emotionally. Treatment pathways typically progress from conservative measures to surgical interventions, sometimes culminating in the implantation of artificial sphincters. While existing models like the AMS 800™ have demonstrated efficacy, concerns regarding the operating by patients and high rates of re-operation persist. Complications such as tissue erosion further underscore the need for innovation in this field. Here, we propose an approach utilizing Hydraulically Amplified Self-healing Electrostatic (HASEL) actuators to develop an advanced artificial urethral sphincter. By employing HASEL actuators arranged in a cuff configuration, we aim to address the limitations of current devices. Initial in vitro testing on porcine urethrae has shown promising results, demonstrating the ability to mimic sphincter function. This approach holds potential to significantly enhance the quality of life for patients suffering from incontinence as they regain control over their bodies. Further research and clinical trials are warranted to validate the efficacy and safety of this approach.

The Dielectric Elastomer Actuator (DEA) has garnered significant attention as an emerging electromechanical transducer across a variety of applications, including soft robotics, artificial muscles, loudspeakers, and haptic devices, among others. Researchers have explored and fabricated diverse DEA configurations to enhance their actuation forces and responses. The conical DEA construction involves pre-stretching the elastomer layer using two concentric circular rings in an out-of-plane direction, enabling the device to expand further vertically upon electrical stimulation. This study focuses on configuring a conical DEA to produce adaptive haptic feedback for a rotary knob, a component commonly utilized in automotive interiors, such as radio volume or air conditioning controls. Traditional knob designs employ a coil spring with a fixed constant to deliver predefined torque feedback during rotation without any capability to offer different haptic feeling. To overcome this limitation, a conical DEA has been fabricated, integrated with a knob, and validated with an analytical model. By manipulating the driving voltage's amplitude, frequency, and waveform, the DEA-enhanced knob can generate varied torque profiles, offering distinct detents and tactile sensations. This innovative approach in automotive applications presents the opportunity to outfit the dashboard with a single knob for multiple functions, each with unique haptic performance.

Ras Labs makes Tactile Fingertips™, which are remarkably like human fingertips, but are more sensitive and robust (20,000,000+ cycles) with 25X faster response times. Tactile Fingertips are based on Synthetic Muscle™, which is a class of electroactive polymers (EAPs) that sense pressure (gentle pressure to high impact), contract and expand at low voltage, and attenuate force.

Dielectric elastomer (DE) transducers are promising candidates for the development soft cooperative actuator systems, due to their high compliance, stretchability, lightweight, and intrinsic self-sensing capabilities. By combining several DE micro-actuators and arranging them as an array, cooperative devices such as distributed loudspeakers, soft robots, and wearable devices can be created. To achieve an effective interaction among the individual actuators and accomplish a shared task, feedback control strategies are required. In the case of cooperative DE devices, a way to fulfil the demanding requirements of lightness, compactness, and flexibility is to exploit the intrinsic material self-sensing capability. Cooperative self-sensing paradigms allow several interconnected actuators to estimate their own displacement as well as the one of their neighbors based on electrical measurement only, and use this information as a feedback for implementing a cooperative control task. In this paper, we investigate for the first time a self-sensing approach for cooperative DE actuator systems. A soft array of 1-by-3 DE elements is used as case of study. Since a single soft membrane is shared across the different actuating DEs, the capacitance of each element in the array changes by a different amount depending on which DE is actuated and/or deformed. Building upon established self-sensing algorithms for single-degree-of-freedom DE actuators, we experimentally investigate the relationship between the DEs capacitive state and the array deformation state, with the goal of reconstructing the latter based on the former for different actuation patterns (corresponding to different combinations of DEs being actuated). These results will pave the way for the future development of cooperative control algorithms for interconnected DE array systems.

Soft robotic technology offers the potential for enhanced safety in human-robot collaboration. Our research introduces a compact robotic arm segment, actuated by silicone-based rolled dielectric elastomer actuators (RDEAs), in combination with a ball joint, showcasing large-angle multi-directional bending. A simplified kinematic, quasistatic model is presented. The segment was built utilizing PCBs as structural components a custom, low friction ball joint, and 3 groups of 3 RDEAs. Two different modes of operation are identified in the model as well as in experiments. One mode with smaller bending angles of 0° to 7°, and one mode with a larger, but constant angle of 25°. The results demonstrate significant bending capabilities in a compact form-factor, laying the foundation for the development of multi-segment RDEA-actuated soft robotic tentacle arms.

Dielectric elastomer actuators (DEAs) consist of thin and highly stretchable dielectric membranes coated with compliant electrodes, which react to an applied high voltage with a controllable mechanical deformation. DEAs are lightweight, stretchable, flexible, and soft, and thus they are suitable for the development of soft robots, wearable actuators, and smart skins. To increase the actuation stroke, DEAs are commonly combined with negative-stiffness mechanical biasing mechanisms, such as pre-compressed metal beams. These beams are subjected to high inherent stresses, and thus they are not well suited for miniaturization and integration into soft structures. Alternative negative-stiffness solutions based on buckling silicone domes, on the other hand, are affected by limited reproducibility, complex manufacturability, and large hysteresis. To overcome these issues, this work proposes novel biasing mechanisms based on thermoplastic polymers, which exhibit negative stiffness and thus are well suited for miniaturized and fully-polymeric DEA systems. In comparison to silicone-based domes and metal beams, they exhibit less hysteretic losses while maintaining high softness and flexibility. The new type of bias is also designed in a simple beam shape with stress-free configuration, due to the adopted thermoforming process. Their mechanical characteristics can be shaped by changing the thermoforming process parameters, as well as on their shape and dimensioning. This paper presents the thermoforming manufacturing process, and demonstrates its reproducibility by experimentally characterizing and comparing the force-displacement behavior of several biasing elements with various geometries. In this way, the suitability of the new bias in DEA applications can be assessed.

Dielectric elastomer (DE) energy harvesting device can be used as power source for battery-free or battery-maintenancefree wireless sensors, owing to the lightweight, high energy density and excellent deformability of DE. Previous research has shown that the power generation output of a DE device can be enhanced by increasing the permittivity of DE. However, the permittivity decreases with the mechanical stretching deformation. In this work, we investigated the influence of the stretch-dependent permittivity on power generation output of DE device. As a DE with increased permittivity, a composite material consisting of silicone elastomer base and rod-like titanium dioxide fillers (RTC) was used. Pure-silicone elastomer-based DE (PSR) was also used for comparison. The permittivity of the DE was measured under different stretching states and the lumped parameter model proposed by Schlögl et al. was used to fit the measurement results. Then the theoretical power generation output of DE device was simulated based on the fitting results. The results showed that the permittivities of RTC and PSR decreased by 28% and 17%, respectively when the DEs were uniaxially stretched to a stretch ratio of 5. The simulated power generation outputs of DE devices with RTC and PSR are similar, due to the large decrease in permittivity of RTC. The conclusion is that it is essential for enhancing power generation output of DE device not only to increase permittivity but also to weaken the stretch dependence on the permittivity because the permittivity decreases with stretching.

The actuation performance of dielectric elastomers (DE) is determined by the electric field when voltages are applied. As the field-dependence is quadratic, higher voltage leads to more efficient actuation. The limiting factor, however, is dielectric breakdown. Due to early-stage and complex manufacturing processes, thin films at present may still contain local imperfections, limiting the overall breakdown field and sometimes causing early breakdown in DE actuators. In particular, when manufacturing multi-layer actuators, a premature breakdown in only one layer causes failure of the entire actuator system. To overcome this problem and to increase the yield of functional actuators, this paper presents a novel method to test and repair DE layers. In a first step, a DE layer is tested for required breakdown voltage in a specially designed breakdown tester and the location of early breakdown spots is identified. In a second step, a method for the repair of these breakdown spots is introduced. A final validation of the repaired DE layer for quality control concludes the process, hence ensuring higher yield of functional actuators in an early manufacturing stage. The testing process using a specially designed breakdown box is described as well as the subsequent repair method of a patch/glue combination. Results about the influence of the repaired spots on the stress/strain behavior of a silicone thin film w/o electrode as well as the performance of the DE prepared with screen-printed carbon black electrodes are included in the presentation.

This work presents a comparison of ionic coatings (ICs) developed specifically for electroactive yarn actuators, able to operate in open-air. Six ionically conducting materials, previously reported in different studies from our group, were used and compared. Two all-solid-state crosslinked materials based on polymeric ionic liquids and four ionogels are described. They are all soft but differ from (i) their nature, i.e. all-solid polymeric ionic liquid vs “wet” ionogel, and from (ii) their ionic charge carriers, i.e. conventional ionic liquid vs biofriendly ionic liquid. As a result, they have conductivities ranging over two orders of magnitude. In spite of the different electrical stimulations applied on the yarn actuators and their electrochemical charging behavior, i.e. bipolar or unipolar, we achieved a conceptual understanding of the key characteristics that ICs should exhibit to induce optimal CNT yarn actuation through the establishment of a relationship between stroke rate-to-potential of coiled CNT yarn actuators’ operation in open air.

This paper discusses a time-domain analysis of the exact transfer function of Zhu’s multiphysics model of IPMC sensors. The authors recently derived the exact transfer function that describes the output voltage of Zhu’s IPMC sensor model. This paper shows that some time-domain constants such as the peak voltage and the steady-state voltage of a step response can be derived from the transfer function. It is shown that the values estimated from the exact transfer function agree with the numerical simulation in the time domain by COMSOL.

The multifunctional sensing that enhance static and dynamic performance have emerged as a hot research topic. This study proposes an integrated approach to achieve multifunctional sensing capabilities in IPMC sensors. The ionic signal is utilised for capturing dynamic information, while the resistance signal for gather static signal. By integrating the ionic and resistive signals of IPMC sensors, we conduct the detection of displacement and velocity. Experimental findings show success in realising both dynamic and static signal sensing functions. Furthermore, by employing data fusion technology, we combined the estimated displacement from the resistance signal with the velocity from the ion signal. The results indicate that the absolute error can be reduced by up to 56% through the predictive angle obtained after data fusion. This combined method significantly expands the sensing ability and range of IPMC sensors, showcasing their potential for diverse applications in sensing technology.

A common method for creating compliant electrodes for dielectric elastomer actuators (DEAs) and soft sensors is to incorporate electrically conductive carbon particles into a polymer matrix. However, using unidirectional aligned carbon fibers instead not only forms a conductive network but also results in a highly mechanically anisotropic electrode. While there is ongoing research to explain the dynamic non-monotonic conductivity-strain behavior of particle-based percolative systems, the mechanics of fiber-based percolative systems have not been thoroughly investigated. Therefore, this work aims to characterize fiber- and fiber-particle-based electrodes. The study reports a counter-intuitive finding that the dynamic behavior of a purely fiber-based electrode is opposite to that of a particle-based electrode. Specifically, while the conductivity of conventional particle-based electrodes decreases when strained, fibrous electrodes generally increase their conductivity with rising strain. This phenomenon may be attributed to the compressive stress experienced by the fibers when the electrode is strained perpendicular to them, resulting in buckling and increased undulation of the fibers, which in turn leads to a higher number of contact points within the network. A more comprehensive understanding of this phenomenon could enable the adjustment of percolation systems that rely on fibers and particles to produce conductors with consistent conductivity within a specific range of strain.

Dielectric elastomers (DEs) have received significant attention for their good performance among different smart material transducers. This study demonstrates the feasibility of fabricating dielectric elastomer actuators (DEAs) using exclusively inkjet printing technique. The manufactured unimorph bending cantilevers are composed of a polydimethylsiloxane (PDMS) active layer, sandwiched between two compliant electrodes, and printed onto a thin polyimide (PI) substrate. This study addresses the key fabrication challenges associated with inkjet printing such a layered actuator structure. This entails the consistent printing of the Ag electrodes on the smooth PI substrate, a PDMS layer on the Ag electrodes, the Ag electrodes on the smooth PDMS surface, and the respective steps of processing and curing. The fully inkjet-printed DEAs exhibited a maximum tip displacement of 36 μm in quasi-static operation (1 kV_pp) and 12.8 μm in resonant operation (50 Hz, 800 V_pp). This is the first time that inkjet-printing has been employed to print an entire dielectric elastomer actuator, broadening the outlooks to develop innovative devices that base on smart material transducers.

Dielectric Elastomer Actuators (DEAs) have emerged as versatile and promising devices for a multitude of applications, including soft robotics, haptic interfaces, and artificial muscles. DEAs are an interesting soft actuator technology due to their high energy density, and fast response. They can be described as compliant capacitors composed of a dielectric elastomer film situated between two electrodes. When a voltage is applied, it induces a compressive Maxwell stress, causing a reduction in thickness and thus an expansion in the other dimensions. However, DEAs tend to exhibit limited deformations under uni-axial forces. To overcome this limitation and induce substantial uni-axial deformations, it is suggested that DEAs should be constrained in the other directions. This constraint can be realized by reinforcing the DEA with unidirectional fibers, resulting in strains up to 75% higher for reinforced DEAs than for conventional DEAs. In this paper, the response time of uniaxial fiber-reinforced DEAs is studied, to evaluate the influence of the reinforcement on the frequency response. To that end, uni-axial fiber reinforced DEAs with a silicone dielectric layer are fabricated by embedding 3D printed fibers of different materials onto the actuators. Fused deposition modelling is used by tuning the infill of the printed part, allowing a fast, simple, and accessible fabrication of the fibers. The response time of the actuators is improved with the use of uni-axial fiber reinforced DEAs, as they provide a more rigid structure and less losses, with a decrease of up to 15% in the response time.

Dielectric elastomer transducers exhibit extraordinary actuator properties due to their huge actuation, small construction volume and low energy consumption. Dielectric elastomer actuators (DEA) consist of a thin dielectric elastomer (DE) film covered with stretchable electrodes on both surfaces. If a high voltage is applied, the electrodes attract each other which leads to a reduction of the elastomer film thickness and due to the incompressibility of the elastomer film to an actuator area enlargement. Based on extensive developments, a variety of actuator forms are standard in research and, in some cases, in application. With special designs, such as out-of-plane actuators, dielectric elastomer actuators are able to transmit larger forces with deflections in the range of around one millimeter. Here, we present the fabrication and characterization of DE multilayer actuators as well as their embedding in out-of-plane actuators. In detail, the multilayer actuator consists of eight elastomer layers with thicknesses of 100 μm each and electrode widths of 30 mm and lengths of 50 mm or 80 mm. The developed multilayer actuators provide in-plane deflections of about 2% and out-of-plane deflections of about 400 μm and 800 μm for actuators with lengths of 50 mm and 80 mm, respectively, when operated with an electric field of 50 MV/m. The out-of-plane multilayer actuators exhibiting a blocking force of e.g. 1.8 N at an electric field of 70 MV/m. In order to describe the actuator behavior, an analytical model based on the neo-Hookean hyperelastic material model is developed. The comparison of the calculated and experimental data shows a good agreement for the in-plane investigations of the actuator multilayers and an approximate agreement for the out-of-plane actuators.

Dielectric elastomer (DE) transducers consist of thin elastomer films and compliant conductive electrodes on each side. Several DE-based systems, e. g. DE stack transducers, loudspeakers or sensors, have a great potential in industrial applications. Using a sheet-to-sheet film handling process enables laminating thin, pre-fabricated elastomer sheets which are characterized by reproducible and homogeneous properties. In combination with a droplet-based electrode application process, multilayer DE transducers can be manufactured. For successfully integrating DE transducers into higher-level processing systems, manufactured large-scale DE laminates must be precisely cut into smaller DE units. Moreover, the electric contact points need to be advantageously designed to enable a reliable electrical interlayer connection and low contact resistance for external electrical bonding. For this purpose, an alternative laser-cutting concept is presented which comprises the selective cutting of each laminated elastomer layer and its integration into the DE manufacturing process. Based on theoretical preliminary considerations, an 18W CO₂-laser is selected and test on cutting 50 μm thin Wacker Elastosil 2030 films are carried out. Using one elastomer film on a PET liner suitable laser parameters for cutting the elastomer without significantly damaging the layer below are determined experimentally. By integrating laser-cutting into the DE manufacturing process, a DE laminate is produced and the cut edges are visually inspected. The results show that the presented concept works in general.

Recently, dielectric elastomers like polydimethylsiloxane (PDMS) and acrylic elastomers have become prevalent as foundational materials for wearable sensors and electroactive polymers. Nevertheless, a significant challenge in using these elastomers lies in their notably low surface energy, presenting issues for electrode deposition and adhesion. In applications like sensors and electroactive polymers (EAPs), it is essential to cover dielectric elastomer substrates with thin, stretchable electrodes. However, the low surface energy of these substrates complicates the production of a thin, uniform film using ink materials. Materials based on nanowires or metal vapor deposition exhibit poor adhesion to PDMS, easily peeling off and resulting in unreliability. Surface treatments, such as exposure to plasma and UV light, can temporarily elevate the surface energy of PDMS. However, this treated surface reverts to its original state within a few hours, forming a brittle surface layer prone to cracking when stretched. Notably, such treatments are ineffective for acrylic elastomers. To overcome these challenges, we have developed a viscous liquid composite ink consisting of PEDOT:PSS and PDMS (A/B). This ink can be easily applied to pristine PDMS substrates through methods like blade casting and screen printing. The coatings form a highly transparent and stretchable surface layer, acting as a compliant electrode. These coatings created using PEDOT:PSS/PDMS composite ink with Elastosil (PDMS) and 3M VHB 4910 as dielectric elastomers, result in transparent dielectric elastomer actuators. The actuation strain and breakdown fields are slightly lower than those in dielectric elastomer actuators (DEAs) with conventional graphite electrodes. However, the self-cleaning capability of these PEDOT:PSS/PDMS composite electrodes provides an advantage over conventional electrodes, particularly in terms of resistance to localized dielectric breakdown of DEAs.

When dielectric elastomer actuators (DEAs) are used in micro-scale applications, the resulting area-to-thickness ratio is expected to be much smaller in comparison to that of macro-scale systems. In this case, local effects such as fringing field are expected to have a non-negligible impact on the resulting actuator behavior. As a result, numerical predictions obtained via conventional models, which in turn are based on uniform field assumptions, are expected no longer to be accurate. Motivated by the need to develop and optimize micro-scale DEA applications, this paper presents a numerical study on how the electro-mechanical performances of a DEA are affected when reducing the system scale. In-plane and out-of-plane DEA configurations are investigated via dedicated finite element simulations, in which the system relative dimensions are progressively decreased, and the performance are evaluated in terms of both mechanical (i.e., stroke/force) and electrical (i.e., capacitance) response. The finite element predictions are then compared with the results obtained via commonly used lumped-parameter models based on uniform field distributions. The results obtained provide insights into the scale at which the performance of DEAs can no longer be explained with conventionally used lumped-parameter models, and will pave the way for future DEA cooperative micro-actuator applications.

Dielectric elastomer actuators (DEAs) have been proclaimed as a transformative technology with applications spanning from robotics to biomedical devices. They are especially appealing because of their key characteristics, including low weight and lifetime. However, there are still challenges in tuning these actuators for desirable mechanical performance. Here, we examine the effects of geometry and material characteristics like inner diameter and Young's modulus on the performance of hollow fiber dielectric elastomer actuators (HFDEAs). These parameters were chosen because they are amenable to experimental validation and play a straightforward, yet significant, role in DEA performance. The model's parameters are based on experimental data, giving our computational simulations a solid foundation. The study takes into consideration the electro-mechanical coupling using finite element method (FEM) simulations in COMSOL Multiphysics. While the electrodes' attraction to one another results in length expansion, the results suggest that the larger surface charge density on the internal electrode compared to the inner one in hollow fiber DEAs results in radial expansion as well. This model also provides an estimation on the actuator holding force which is challenging to evaluate experimentally. According to preliminary results, careful parameter selection can indeed increase the holding force, thereby enhancing the actuator's overall effectiveness. In conclusion, this study provides an understanding of design parameters of HFDEA offering a comprehensive framework for HFDEA design by integrating both experimental and computational approaches.

Dielectric elastomer actuators commonly use flexible conductive electrodes to apply an electric potential for actuation. Depending on the material used, these electrodes often possess predictable piezo-resistive properties. Combining electrical impedance tomography (EIT) with a dielectric elastomer actuator (DEA) is investigated in this work to map compressive forces occurring throughout the electrode surfaces. This technology could allow for enhanced closed-loop control of electroactive actuators, extending their already extensive set of applications. This deformation mapping system also has the potential to be used with other piezoresistive materials, opening up more applications requiring a large hardness range and pressure sensitivity. With the material used in this work, the DEA-EIT device has an inherent trade-off between actuation and pressure mapping accuracy driven by the compliant electrode thickness of the DEA. The DEA-EIT device exhibited actuation strains of 2.5 % with a mean centre-of-mass error from a range of loads applied were 7.9 ± 0.7mm for 2mm thick DEA electrodes. It is proposed that future work on custom hardware could be devised for the DEA-EIT system so the sensing and actuation can occur concurrently in real-time. Real-time control mean that applications requiring human-like manipulation can be designed, ranging from biomedical implant devices to agricultural processing equipment.

Flexible and stretchable electronics have garnered significant interest for their potential applications in fields like soft robotics, sensor-integrating machine elements, Industry 4.0, biomechanics, and wearable technology. Among these innovations, multi-layer capacitive strain sensors based on dielectric elastomers (DEs) stand out for their sensitivity, large deformation range, and compatibility with complex shapes. In this study, the focus is on advancing the design, fabrication, and evaluation of multi-layer capacitive strain sensors based on DEs. The goal is to explore novel approaches to enhance stability, sensitivity, and manufacturability. The research in this work introduces a comprehensive classification of four-electrode layer DES (4EL-DES) structures, including a new 50 μm-C configuration, to identify designs maximizing capacitance and sensitivity. Additionally, investigation into electrode pin designs is conducted which considers manufacturing feasibility and mechanical stability, utilizing finite element (FE) simulations and experimental validation to assess various options. Novel fabrication techniques, such as upside-down electrode layering and the use of conductive thread paired with conductive carbon grease for electrode connections, aim to streamline manufacturing and enhance reliability. FEM simulations analyze stacked 4EL-DES structures’ deformation behavior and the relationship between capacitance change and strain, providing insights into their mechanical and electrical properties under different loading conditions. Experimental results from various sensor configurations, including individual 4EL-DES sensors and stacked and "open" 5EL-DES structures, offer insights into performance capabilities and potential applications. This research contributes to advancing flexible sensor technology, laying the groundwork for high-performance sensors applicable in soft robotics, biomechanics, and beyond.

Fringe field sensors based on piezo dielectrics offer opportunities in under water sensing as they are solid state, incompressible and robust. Questions remain regarding their susceptibility to noise. Specifically, we refer to anomalous outputs when the sensor is brought in close proximity to or just touching a conductive object. One solution involves isolation through a flexible Faraday cage. We have investigated two approaches for such a Faraday cage. One approach utilizes a conductive fabric while the other is based on a carbon filled dielectric. We compared the performance of both shielding approaches regarding noise suppression and their influence on sensitivity. The anomalous effects upon contact with conductive objects leading to inconsistent measurements were overcome. Furthermore, their response to salinity levels and submersion time were investigated and the influence of design parameters on the performance of the sensor determined in a Design of Experiment study. Varied parameters include overall footprint alongside electrode spacing and width. Performing a full factorial design plan enabled us to quantify the relations between the parameters. This investigation improved signal stability in the piezo dielectric fringe field sensors, making it possible to design a broader range of sensory systems able to withstand the harsh marine environment. The sensor will assist fish robots in their exploration of the ‘Silent World’.

Scoliosis is a spinal deformity that can be treated with a scoliosis brace that applies pressure to the trunk. The child's body adapts to the applied pressure and the spine is corrected. However, the braces are adjusted periodically or after rapid growth without monitoring the adaptation process. This study proposes to investigate the pressure distribution in the internal padding of the brace in order to adapt the orthosis to the individual needs of the patient in the long term. For this purpose, the implementation of dielectric elastomer sensors is used to detect pressure peaks and valleys on a mutual capacitance sensing grid. Subsequently, direct ink writing is used to print electrode lines, allowing analysis of the flexible electrode grid geometries. The electrodes are characterized and tested under uniaxial strain. Furthermore, by placing the electrodes on the padding of the orthosis, the relative pressure distribution can be assessed. Our results demonstrate the application of dielectric elastomer sensors in orthopedics and explore the effect of different printed geometries. Although absolute values have not been evaluated, characterization of relative pressure differences is sufficient to detect pressure points. By monitoring long-term changes, therapy can be tailored to the body's individual adaptation process.

Stretchable electronic conductors are an important class of material enabling electroactive polymer (EAP) research. One of the most common approaches to creating a stretchable conductor is to embed conductive particles within a nonconductive matrix material to create a composite with favourable electromechanical properties. Whether an EAP device employs these composites for specific functions like strain sensing or simply as deformable electronic interconnects, the interplay between mechanical deformation and electronic conductivity frequently emerges as a central concern. While these materials are simple to produce, the relationship between mechanical strain and changes in electrical resistivity (piezoresistivity) can be complex and difficult to predict, and the factors that influence this behaviour are not well understood. This study focused on the comprehensive electromechanical characterization of various samples of piezoresistive elastomer composites. The work examined how a range of factors such as filler loading, matrix material, strain properties, additives, and production methodologies affected the piezoresistive properties of these composites. This work identifies key factors that can affect the magnitude, time dependence, and even direction of piezoresistivity. By identifying important influencing factors, the results of this work are intended to assist researchers in designing materials that are best suited for their specific use case.

Dielectric elastomer actuators (DEAs) have raised interest due to their remarkable capabilities in various applications, such as soft robotics, haptic feedback systems, and biomedical devices. To harness the full potential of DEAs, the choice of the electrode material and fabrication method is critical. This study investigates the application of carbon based printed electrodes for DEAs, focusing on three prominent printing techniques: pad printing, inkjet printing and stencil printing. Comparisons are made to evaluate their performance in terms of electrical conductivity, mechanical properties and actuator performance. Findings from this research aim at providing valuable insights into selecting the most suitable electrode fabrication method for specific DEA applications.

Dielectric Elastomer Actuators (DEAs) are a type of smart material described as compliant capacitors. They show impressive performances as soft actuators, such as a high strain and fast response. Nonetheless, replicating natural muscle function with DEAs has posed a challenge since DEAs exhibit in-plane expansion, whereas natural muscles contract when stimulated. This publication aims to investigate the use of a normal configuration of DEAs to obtain a contractile movement for post paralysis facial reanimation, by inversing its actuation cycle: the voltage applied on the DEA will constantly be on to keep the DEA stretched and will be off when a contraction movement is wanted, for instance for smiling. Several difficulties linked to this solution need to be considered, such as the self-discharge rate of the DEA, linked to the leakage current flowing through the dielectric when a voltage is applied. The leakage current corresponds to a leakage of charge between the two electrodes and is suggested to influence the self-discharge rate but also the dielectric breakdown and the performance of the actuator. As DEAs present a fast self-discharging rate, the charging frequency of DEAs should be determined to avoid unwanted displacement leading to visible facial spasms. DEAs and their self-discharge rate are characterized, to determine the chosen charging frequency and duty cycle for facial reanimation. The goal is to have the minimum discharge between two actuation cycles. A discharge model was proposed and validated experimentally, allowing to determine a chosen frequency of 2 Hz and 50% duty cycle, leading to a discharge of less than 3% between two actuation cycles, and thus allows to consume 1.5% less energy over each cycle compared to a continuous actuation.

This study proposes a vibration excitation technique using a dielectric elastomer actuator (DEA) that can attach to a conductive structure based on an electro adhesion technique. Vibration responses of mechanical structures are experimentally analyzed to assess their mechanical characteristics. Conventionally, impulse hammers, heavy and rigid exciters, and lead zirconate titanate (PZT) actuators are applied to excite the vibration of the structure in a vibration experiment. However, the other vibration excitation technique should be applied for flexible structures with curved surface to evaluate their vibration response accurately without damages on them. Herein, a DEA can be applied to the vibration excitation taking advantage of its features of high flexibility, stretchability, and fast response. Conventional DEAs are attached to the target structures with adhesives degrading DEAs’ reusability. In this study, the electro adhesion technique, which can generate an attraction force were applied to the DEA. The proposed DEA can attach to the target without adhesives. The proposed DEA was fabricated by stacking layers that can generate the excitation force and that can generate the attraction force of the electro adhesion. Then, a vibration experiment for an aluminum pipe structure was conducted applying the DEA excitation. Finally, the effectiveness of the proposed vibration excitation technique was evaluated based on vibration responses of the target structure.

Dielectric elastomer actuators (DEAs) have gained an increasing importance in various research applications. In literature the most explored dielectric elastomers (DEs) are silicones and acrylics. As promising alternatives, polyurethanes have been identified due to their inherent higher dielectric constant, higher dielectric strength, and appropriate response behavior. However, polyurethane systems are known to have hygroscopic properties that can lead to changes in the dielectric properties when they are exposed to moisture. In this work, a circular DEA composed of a thermosetting polyurethane film and carbon grease electrodes is exposed to four stabilized levels of relative humidity (RH = 22 %, 36 %, 56 %, 70 %) at a constant temperature of 22 °C. The actuation strain is measured to study the effect of moisture absorption on the DEA performance. In addition, impedance spectroscopy is performed on the DEA to investigate the influence of moisture on its dielectric properties. Impedance, phase angle and dielectric constant of the DEA are evaluated at the respective RH level. The results show a rise in the dielectric constant of 15 % with increasing the humidity from 22 % to 70 %. However, increasing the humidity does not necessarily lead to an increase in actuation strain.

Project BROADCAST will deliver a new class of powerful soft, biomimetic systems that can interact with their environment in a safe, bio-inspired way. The approach is based on major advances in the production technology of dielectric elastomers (DE) circuitry, new soft electronic materials, and new approaches in signal processing. BROADCAST investigates multi-functional DEs that drive robotic structures based on bio-inspired electro-mechanical control strategies such as central pattern generators, autonomous peristalsis, locomotion and similar others. This requires new materials for flexible electrodes and sensors that provide curtailed electrical and electro-mechanical properties, such as Young’s modulus, conductivity and piezoresistivity. These materials will provide new features in robotics such as sensorless system where the DEA will act both as an actuator and a sensor by providing continuous feedback in real-time.

With the characteristics of lightweight, low driving voltage and biocompatibility, ionic polymer-metal composites have attracted much attention in the field of soft-robotics and artificial muscles. This paper introduces the development of a novel design of a segmented tubular ionic-polymer metal composite (IPMC) actuator. This configuration allows a large bidirectional movement, paving the way for the development of intelligent and adaptable structures. In this study, the IPMC actuator is manufactured from a 40-mm long prefabricated Nafion polymer tube with an inner diameter of 1.3 mm and an outer diameter of 1.6 mm. The outer surface is plated via an electroless-plating process. The proposed tubular IPMC design consists of an additional inner electrode and two outer isolated segments, setting it apart from existing approaches. It includes a new coating method of the inner electrode, offering a more efficient and versatile solution for actuation and sensing applications. Preliminary experimental investigation is employed to characterize the electromechanical performance of the actuator, as well as to quantify the maximal angular bending. Furthermore, the presented results establish the operational principles of the innovative design and validate the proof-of-concept. The experimental results show improved performance compared to the state-of-the-art.