EuroEAP platform

Research on electrically tunable optical lenses for various applications, such as machine vision, microscopy, and mobile devices, has grown significantly in recent decades. Effective adaptive lenses have been demonstrated through the adoption of innovative actuation technologies, including electrowetting effect, liquid crystal actuation, dielectrophoretic effect, piezoelectric/electrostrictive, external pumpshydraulic/pneumatic driving, electromagnetic driving, electrostatic zipping, electro-thermal activation, and dielectric elastomer actuation. Some have been demonstrated with fluid lenses, while others with elastomeric lenses. The latter are particularly attractive, as they are less sensitive to thermal variations, mechanical vibrations and gravitational sagging. To date, most of the actuation technologies which demonstrated focal length tunability of elastomeric lenses with compact driving (thereby excluding hydraulic and pneumatic systems), critically limit the achievable range of focal length variation, owing to a limited ability to vary the lens curvature. Especially, they make it difficult to switch between a curved surface (close-distance focus) and a flat surface (far-distance focus). Here, we present a new concept for a dielectric elastomer actuation-based tuneable lens that is capable of large variations of focal length. The lens uses a dielectric elastomeric layer as both actuation and optical medium, resulting in a thin structure, capable of large tuning range.

Wearable robots and devices-garments with embedded elements that actuate to change shape or apply forces to the wearer-offer promise for assistive and augmentative applications including rehabilitative gloves, haptic devices, and dynamically thermoregulating clothing. Early iterations of wearables from the 1950s and 60s took the form of rigid exoskeletons; however, in the past twenty years, a growing subset of this field has transitioned to the use of soft components and materials to improve portability, fit, and comfort, guided in part by advances in the related field of soft robotics. Based on the unique requirements for wearables, including personalization for varied bodies and low cost of production for wide accessibility, automated and highly customizable textile-compatible manufacturing strategies must be developed to support fabrication and integration of all the necessary components (sensors, actuators, control components, interconnections). Considering actuation, shape changing yarn mechanisms including those employing electroactive polymers (EAPs), are especially promising due to their ability to support a low profile, light weight, and the potential for seamlessly integrated devices. This talk will discuss the intersection of knowledge from the field of textiles with the needs of soft robots, focused on wearable applications, including performance metrics, architected material designs, and fabrication strategies, considering opportunities in utilizing EAPs.

Ferroelectric polymers from the class of PVDF materials are ideally suited as multimodal sensors in electronic skins, industrial production and mobility, as their ferroelectric properties allow them to be used for multiparameter sensing of strain, pressure, touch, vibration, temperature, IR radiation and vital parameters, as well as for the conversion of mechanical to electrical energy (energy harvesting). In particular, if fabricated by a scalable technique like screen or inkjet printing, ferroelectric polymer devices can easily be integrated on flexible substrates like plastic foils, paper, textile, leather, rubber, metal foils and so on. This is very important since energy autonomy and conformability are essential elements in the next generation of wearable and flexible electronics. In the talk I will summarize the state of the art of flexible ferroelectric polymer devices with respect to materials, processing and applications and will then present recent developments of our PVDF-TrFE based PyzoFlex® technology with novel material combinations, innovative integration concepts and more sophisticated demonstrators for sensing and energy harvesting.

We present trilayer electroactive liquid crystal elastomer (eLCE) systems made of two smart materials, liquid crystal elastomer (LCE) and ionic electroactive polymer device (i-EAD). These trilayer eLCEs are bi-functional and can perform either bending or contractile deformations under low voltage stimulation (< 10V). They can also function as mechanoelectrical sensors to respond to the bending deformation. This approach of combining two smart polymer technologies, i.e., LCE and i-EAD, in a single device, is promising for the development of smart materials with multiple degrees of freedom in the fields of soft robotics, electronic devices, and sensors.

As one of the most promising artificial muscle materials, dielectric elastomers (DEs) have been widely studied and applied. In recent years, a variety of high-performance dielectric elastomers have been developed, especially the bimodal networked elastomer (PHDE) which has achieved energy and power densities superior to those of natural muscles. However, it remains a challenge to significantly reduce the driving voltage of dielectric elastomers while maintaining their high mechanical output. This talk will introduce the recent progress from our group on developing multilayer structured dielectric elastomer actuators (DEAs) with low driving voltages and high mechanical outputs. These high-performance DEAs are enabled by simultaneously tuning the mechanical/dielectric properties of PHDE, developing new ways to prepare uniform ultra-thin elastomer films, and modifying the dry-stacking method to fabricate large-area dielectric elastomer stacks. The potential of newly developed DEAs for applications in wearable devices and soft robots will also be demonstrated.

Continuum robots are an innovative class of semi-soft robots that overcome some limitations of the conventional rigid ones. The main characteristic of continuum robots is represented by a flexible spine-like structure capable of performing complex bending patterns. To achieve precise bending and motion, continuum robots employ different soft actuation solutions which are generally based on tendon-driven, pneumatic, and hydraulic principles. These technologies are typically noisy and require a significant amount of installation space compared with the robotic structure itself, posing an obstacle to its portability and practical use. A possible solution comes from the use of unconventional actuators such as Shape Memory Alloy (SMA) wires. These transducers, commonly consisting of Nickel and Titanium, can undergo a contraction in length when heated. Being metal and shaped as wires, they can be activated thermically through an electric current due to the Joule effect. Some SMA advantages are high flexibility, lightweight, high energy density, and the ability to act simultaneously as actuator and sensor. In this work, we present a model-based framework for the design, simulation, and control of SMA continuum robot. The robot concept involves the use of an elastic backbone made of superelastic SMA to replace the outer flexible tube. A port-oriented hybrid modeling framework enables efficient modeling and simulation of complex SMA structures in a modular and physics-oriented way.

High voltage is a powerful mechanism for driving soft electrostatic transducers with a variety of behaviors, such as high-speed actuators, energy-efficient generators or controllable adhesives. Off-the-shelf high-voltage amplifiers are bulky, expensive and have only one output - rendering them unsuitable for driving and controlling multi-channel systems, and imposing cost-limitations on developing such systems. Existing multi-channel solutions used open-loop control or were embedded within larger systems, limiting their functionality and versatility. Here we present an accessible, modular tool for splitting any constant-output high-voltage power supply into a user-defined number of independently-controllable output channels, each with closed-loop voltage control, enabling simultaneous tracking of arbitrary, reversing polarity voltage waveforms over multiple channels. Each independent channel is controlled by one low-cost module (~250 Euro); modules are stacked together vertically and share a single high-voltage power supply, and a single USB connection controls all modules in the stack. Each module can provide up to 1 mA current at 10 kV, enabling a 1 W electrical workspace sufficient for driving a variety of electrostatic transducers. Altogether, our modular architecture enables controlled delivery of high voltages to a wide variety of electrostatic devices, providing researcher with an accessible and versatile tool for driving multi-component electrostatic robotic systems.

Polymers that can change their shape and at the same time act as their own sensor may become important systems of tomorrow. Due to their multifunctionality, they are also referred to as smart materials. Dielectric elastomers (DE) combine these properties perfectly as they can be used as both actuators and sensors. Over the years, Carbon Black has become the preferred electrode material for DEs. Besides their well-known good properties, a high initial resistance and a limited spatial resolution due to the applied manufacturing processes makes it disadvantageous to use these electrodes in some types of applications. Especially when high excitation frequencies are required, metal based compliant electrodes take advantage of their low electrical resistance. Sputter deposited onto a pre-stretched silicone membrane, the 10 nm thick nickel-based electrode exhibits a wrinkled surface after the relaxation of the membrane giving the structure the required compliance. In addition, with a laser structuring process the spatial resolution is in the range of 20 micrometers. In the presented work, the idea of a functional glove, equipped with DEs based on metallic electrodes is presented. A hapto-acoustic element as well as a sensor matrix are to be integrated in the glove. The concept of the glove is shown together with a new manufacturing process for the creation of reliable electrical contacts through a stack of DE membranes. In addition, first acoustic characterizations are presented.

Silicone elastomers have received vast attention for their use in products such as stretchable electronics, implants, and medical devices. In recent years, there has been a growing interest in developing elastomers that possess mechanical stability, softness, and elasticity similar to human muscles for integration into soft robotic devices. The incorporation of silicone elastomers with actuation properties into textiles could, for example, revolutionize the production of soft wearables and lightweight exoskeletons. A new class of silicone elastomers, characterized by a network composed of concatenated (interlocked) polymer rings, has recently emerged. These elastomers demonstrate interesting characteristics such as extreme softness and stretchability compared to traditional covalently crosslinked elastomers. In this work, two telechelic hydride- or vinyl-functional polydimethylsiloxane polymers with reactive double bonds in the main chain were prepared. The synthesized polymers were utilized to prepare silicone elastomers with a concatenated ring network structure. The presence of the carbon-carbon double bonds inside the soft ring network allows for further functionalization to, e.g., increase the dielectric permittivity with dielectric moieties, introduce self-healing properties, or create conductive silicone elastomers.

The outstanding design versatility of IPMC technology enables the creation of a tubular continuum structure with an actively moving outer skin and an inner hollow space. Therefore, it can guide a variety of functional elements such as solids, gases, and liquids. This structure has the potential to significantly impact a wide array of fields ranging from medical engineering to micro-manipulator applications. This work introduces the development of a novel segmented tubular ionic polymer metal composite (IPMC) actuator design. This configuration allows for large bidirectional movement, paving the way for the creation of intelligent and adaptable structures. The tubular IPMC actuator is fabricated from a 40-mm long prefabricated Nafion polymer tube with an inner diameter of 1.5 mm and an outer diameter of 1.8 mm. The outer surface is plated using an electroless-plating process. The proposed tubular IPMC design incorporates an additional inner electrode and two isolated outer segments, setting it apart from existing approaches. Preliminary experimental investigations were conducted to characterize the electromechanical performance of the actuator and quantify its maximum angular bending. The results demonstrate the improved performance of this innovative tubular IPMC design compared to conventional IPMC configuration, validating the proof-of-concept, and establishing the operational principles of this novel approach.

Dielectric elastomer actuators (DEA) are suitable for soft robotic systems because they offer sufficient forces and rates, are compliant, and remain functional after large deformations [1]. Such actuators require electrodes with high electrical conductivity and electro-mechanical properties that remain constant upon deformation. Carbon grease has been used for DEA fabrication, owing to its adhesion properties, for devices such as grippers [2]. Its conductivity is low, however, fabrication and use are hampered by the remaining liquid nature, and long-term stability suffers from drying or diffusion [3]. Soft and conductive composites can solve many of these issues. In this study, we discussed a conductive soft composite that is suitable for use in DEA, characterized by high electrical conductivity and stable electro-mechanical properties. Composites containing conductive silver particles (AgP) and carbon black in liquid silicone were blended using a speedmixer. The resulting paste was screen-printed onto silicone film (Wacker). The electro-mechanical properties and durability of the composites were assessed under 10% strain for 4000 cycles. The resistance change of the AgP-CB-Ecoflex composites in response to loading is less significant than that of two other commercial pastes, even when subjected to strains of up to 190%. Furthermore, the cycling stability of the composites is enhanced by the presence of carbon black, which improves the connectivity of the conductive network.

Hydraulically Amplified Self-healing ELectrostatic (HASEL) zipping actuators have received much interest due to their high performance in terms of actuation strain and force. HASEL actuators consist of two parallel polymer films partly coated with flexible electrode layers at their outer surfaces and sealed along their edges to a pouch, which is filled with an oil. When a high voltage is applied between the electrodes, the electrostatic attraction leads to a zipping effect and displaces the oil to the pouch region without electrodes. This oil displacement generates a strong actuatoric deformation of the pouch. A series of HASEL actuators can be used to cause a bending displacement of a flexible and soft robotic gripping finger. The performance of the single HASEL actuator and the gripping finger depends on various geometrical and material parameters. In order to optimize the actuation performance, a simple mathematical model was established to calculate the dependence of the stroke and force of the HASEL actuator as well as the bending angle and blocking force of the gripping finger on the applied voltage. This model was used to predict the performance of HASEL actuators consisting of different polymer materials. The calculated data was compared with the results of experimental investigations on corresponding HASEL actuators and related bending finger structures giving valuable information on the requirements on the actuator materials and the finger structure.

Dielectric elastomer actuators (DEAs) have gained a high popularity in wearable and user interaction units. We propose a multi-modal DEA concept that leverages a single voltage input to concurrently work as linear actuator and loudspeaker, while also integrating self-sensing capabilities. Low-frequency linear actuation is obtained by inducing tangential stretching of the DEA membrane surface, whereas sound generation is achieved through structural vibrations of the DEA membrane surface. Multi-mode actuation is combined with a new self-sensing paradigm: measuring the current signal arising from the acoustic excitation (including highly polychromatic driving voltages) and processing it in real-time with capacitance estimation algorithms, the actuator stroke can be reconstructed with no need for additional transducers or probing signals. The proposed self-sensing approach is evaluated in terms of the correlation between capacitance estimates and the low-frequency stroke of the device. Concurrent self-sensing and multi-mode actuation are demonstrated in a number of application scenarios, in which the DEA acoustic output is adjusted in closed-loop as a function of externally induced deformations, such as impacts with obstacles, or interactions with a user. This multi-modality paradigm paves the way to new applications, such as multi-sensory user interfaces or integrated sensor-actuator units able to sense their state during operation and provide feedback accordingly.

Almost 80 million people worldwide live with tremor, involuntary movements of body parts. Wearable soft robotic devices are potentially a major practical solution for active tremor suppression, instead of traditional treatments. However, current prototypes face limitations in actuation performance and complex clinical testing procedures. Here we introduce a comprehensive approach for rapid evaluation of emerging tremor suppression technologies; this method combines reproduction of patient-recorded tremor episodes in a robotic test-bed ("mechanical patient"), with validation of achieved suppression performance of novel soft actuators via biomechanical modeling, avoiding time-consuming clinical testing in early stages of development. This approach highlights that an antagonistic pair of slim (1 mm) and lightweight (15 gr) HASEL actuators is fast and strong enough to suppress clinically relevant tremors of frequencies between 2-8 Hz by 76-94%. Using recordings of natural tremor amplitudes from patients, we show that a PID controller successfully adapts the response of these actuators, despite their non-linearity. The biomechanical model confirms that a single pair of these lightweight actuators generates adequate suppression forces for suppression across all tested tremors. Hence, this comprehensive approach confirms the potential of electrohydraulic actuation for further development in assistive devices, that may improve the quality of life for individuals living with tremor.

Electroactive polymers show promising characteristics, such as lightness, compactness, flexibility, and large displacements, making them a candidate for application in cardiac assist devices, robotics and other compact applications. This revives the need for quasi-square wave voltage supply switching between 0 and several kilovolts. It must be efficient in both the charge and discharge phases, to limit the heat dissipation, and compact in order to be implanted. The high access resistance, associated with compliant electrodes, represents an additional difficulty. Here, a solid-state Marx modulator is adapted to cope with electroactive polymer characteristics, taking advantage of an efficient energy transfer over a sequential multistep charge/discharge process. To ensure compactness, efficiency, as well as the needs of an implanted device, a wireless magnetic field-based communication and power transfer system has been implemented. This work demonstrates the benefit of this design through simulations and experimental validation on a cardiac assist device. At a voltage of 7 kV, an overall efficiency of up to 88% has been achieved over a complete charge/discharge cycle.

An ideal electrode for EAP would posses negligible stiffness, near-perfect conductivity and adhesion, while being resistant to stretching or dessication. So far, achieving all these properties simultaneously remains beyond reach. Acceptable strains and compliance, coupled with ease of manufacturing, often come at the expense of conductivity. Resistive electrodes reduce both the EAP efficiency and operational bandwidth, which is particularly relevant for large capacitors (with resulting large RC time constants), such as large-scale energy harvesters, or for high frequency applications, like loudspeakers. Herein we describe a continuum time-domain model that predicts the electrical dynamics of EAPs by considering the electrode resistance. The model describes the non-uniform distribution of the electric potential over the EAP electrodes during fast supply voltage variations. Model results closely align with the voltage distributions measured in silicone-carbon composite electrodes via multiple electrical contacts integrated directly into the bulk of the electrode. The validated model allows performing estimates of the electrical time constants and maximum working frequencies of EAP transducers based on their dielectric properties, size and electrode resistivity. The outputs of our analysis can be used as an electrical design tool to establish electrode resistivity limits based on target application dynamics.

Bioinspired devices such as artificial muscles, have gained increasing attention in academic research and industrial development with the aim of improving the patient's quality of life. Materials used for designing artificial muscles should meet various requirements like high flexibility, fast response time, low power consumption, low manufacturing costs and straightforward procedures, light weight, long life time, etc. Electroactive polymers, especially conducting polymers (CPs) in the form of fibre morphology meet the mentioned requirements due to the high active area, high flexibility, fast response time under low applied voltages, revealing impressive actuation properties and even sensing capabilities during movement. In this context, a novel material configuration based on shape memory polymer (SMP) electrospun nanofibers and a CPs which can perform mechanical motion by applying an external stimulus is proposed. Thus, free standing SMP meshes were metalized in order to make them conductive and then the metalized nets were functionalized with a CP film with dispersed gold nanoparticles. The prepared material was morphologically, structurally, mechanically analyzed and from biocompatibility and actuation point of view. The shape memory behavior and addition of gold nanoparticles should improve the actuation performances by increasing the conductivity of the material and therefore improving the stimulus distribution along the fibres.

Facial paralysis is a highly burdening condition, resulting in a patient's inability to move his musculature on one or both sides of his face. This condition compromises the patient's communication and facial expressions, and thus dramatically reduces his quality of life. The current treatment for chronic facial paralysis relies on a complex reconstructive surgery. The use of DEAs is proposed as a less invasive approach for dynamic facial reanimation, thus avoiding the traditional two-stage free muscle transfer procedure and allowing for a faster recovery of the patient. A study of the facial muscles and neural interfaces is performed, in order to implement a realistic setup and restore movement in the corner of the mouth, the eyebrows and blinking.

Both urinary and fecal incontinence are common conditions in the general population that place a high degree of physical and psychological stress on those affected. For example, pads or transurethral urinary catheters are used to manage the disease, but these still considerably restrict the patient's activities. For more severe cases, there are implant-based therapies including artificial sphincters. The existing models including the AMS 800T show high revision rates due to complications such as tissue erosion. To address these challenges, we propose an approach utilizing Hydraulically Amplified Self-healing Electrostatic (HASEL) actuators to develop an advanced artificial sphincter. We aim to demonstrate the feasibility of this approach through testing on porcine urethrae, which yielded promising results with a HASEL cuff effectively stopping water flow at a hydrostatic pressure of 20 centimeters water column. Further research is needed to optimize device force, reduce actuation voltage, and ensure safety for clinical application.

In the past decade, numerous studies have proposed optimization strategies targeting components of electro-adhesive devices (EAD) to enhance their performance in terms of normal or shear grasping force. Notably, the comb-shaped interdigital geometry, widely utilized in EAD grasping applications, has demonstrated superior performance in terms of shear force on dielectric objects as well as the suitability to grasp electrically floating conducting objects. While much of the literature has focused on determining the optimal electrode geometry for specific applications by means of theoretical models and finite element method (FEM) simulations, only a few have conducted a systematic exploration of the optimal combination of electrode gap and width through empirical evaluation. This work presents a study aimed at optimizing the geometry parameters of EAD interdigital electrodes to maximize the shear force of the device. This optimization is achieved through a proper experimental campaign developed using the statistical Design of Experiment (DoE) methodology. The EAD samples are fabricated by inkjet printing Ag electrodes, of different comb-shaped geometries, on the same PET film, and their breakaway force on a dielectric object is evaluated using a custom test-bench.

Traditional robotics has focused on enhancing the range of motion and functionality of machines, with most of their mechanical structures being made from rigid materials. The rigid robots have always faced mechanical limitations, such as the difficulty in achieving motions similar to biological models. The development of soft robots, which exhibit behaviors like animals, has opened up new perspectives and applications in robotics. This contribution aims to investigate soft robot structures based on multi-functional Dielectric Elastomer (DE) that can be used as actuators, sensors and signal processors. Our goal is to explore a method for constructing entirely soft robots, where the robot body, control system, power supply system, memory components, and so forth are all designed as soft structures. We have designed an inchworm like soft robot structure, capable of creeping forward under the drive of DEO (DE Oscillator). The inchworm-like soft robot features integrated control components and soft actuators composed of DEAs, without any traditional hard electronic parts. Through an external DC voltage, the robot autonomously generates all signals required to drive its dielectric elastomer actuators and converts planar electromechanical oscillations into creeping motion. This demonstration highlights the potential of soft robotics, providing practical experience for the development of more complete, complex, and intelligent soft robots in the future.

Dielectric elastomer generators (DEGs) are soft transducers capable of converting mechanical energy into electrostatic energy. Increasing the mechanical stretch amplitude and the electric field applied to the DEG leads to higher energy conversion, but at the cost of reduced lifetime. Here, we assess the mechanical fatigue and electrical ageing of a silicone-based DEG, and use the findings to build an electro-mechanical reliability model. The operating parameters (stretch amplitude and electric field) that maximize energy conversion are obtained through a 2-dimensional optimization approach, which considers the antagonistic relationship between energetic cycles and long-term reliability. Energy densities reported in the literature are often obtained by pushing the DEG on the knife-edge of their intrinsic capabilities for a limited number of cycles. In contrast, our approach presents more realistic values in the endurance domain, leading to a substantial reduction of the practical performance that can be achieved.

Artificial muscles, mimicking natural biological movements, show promise in robotics and prosthetics and recent advancements include fiber-reinforced actuators inspired by biological tissues. Enhancing uni-axial deformation in DEAs is possible by applying pre-stretch to the actuator membrane, achieved through uni-directional fibers. However, combining pre-stretch and fiber reinforcement may cause instabilities like fiber buckling due to compressive loads or wrinkling during actuation, which can affect performance. In this work, a novel model aresses these instabilities. The validation of the model presented along with an extensive experimental investigation allow for a comprehensive analysis to explore the impact of fiber buckling on the performance and the force of uni-axial DEAs.

Electrochemically driven yarn actuators providing fast actuation and large contractile stroke are promising soft transducers, and are considered as precursors of artificial muscles for applications in smart textiles, prosthetics, soft robotics or exoskeletons. Among them, electrochemically driven coiled carbon nanotube (CNT) yarn actuators operate by the means of low voltage electrical stimulation, where the accumulation of ions during charge and discharge of their electrochemical double layer capacitance (EDLC) provides stable reversible tensile stroke. Air-operation of such yarn muscles requires the combination of two coiled CNT yarns, acting respectively as anode and cathode, and an ionic coating, acting as an ion source. The optimization of coiled CNT yarn performances and the development of highly ionically conducting, non-toxic and air-stable gels are of primary interest for the integration of these actuators into practical applications. Therefore, this work presents a systematic study on maximizing the electromechanical response of coiled CNT yarns obtained from commercially available yarns, the elaboration of easily synthesizable, environmentally- and biofriendly electrolytes, and the first results on their association into functional devices.

Dielectric elastomer actuators (DEAs) offer lightweight, resilient, cheap, and fast-response capabilities ideal for soft robotics applications. The goal of DEA robots is to interact with their environment in a new save bio-inspired way. DEAs are limited by small actuation and force output, but stacking multiple layers of DEAs can increase the actuation force and deformation. In this study, we propose a novel design for a soft robotic hand based on multilayer DEAs that mimics the human hand. The individual soft fingers are fabricated by bonding multilayer DEAs to a soft silicone body possessing embedded bone structures, to maintain the necessary pre-stretch, to ensure optimum performance of the individual DEAs. The finger design possesses hinge like structures with non-isotropic bending stiffness, as human fingers. We here present first design, optimized by finite element analyses (FEA) , done with Abaqus and compare obtained FEA designs with first experimental studies. The aim of this contribution is, to introduce a new bio-inspired design paradigm for soft continuum robotic structures, combining the advances soft continuum structures, non-isotropic bending structure in minimum energy dielectric elastomer actuators and the biological approach of integrating stiff bones in soft tissue.

Dielectric elastomer actuators (DEAs) offer a promising avenue for the development of soft, flexible, and highly adaptable systems. They consist of a thin dielectric membrane between two compliant electrodes. When the actuator is electrically activated the structure compresses and expands in plane. Due to different desired application scenarios, research is also concentrating on the development of new variants. For this, the evaluation of composites, damage detection methods must be tested and evaluated. Generally, for higher functionality and a longer lifetime, the relationship between the structure of dielectric elastomer actuators and their damage behavior must be known. Therefore, the identification of structural damage is crucial to prevent future failures or more serious accidents. In addition to the well-known failure criterion of electrical breakdown, which has already been analyzed more frequently, other types of damage, including those that occur during manufacturing must be addressed. Therefore, the goal of this work is to identify other fundamental defects that occur. A uniaxial strip actuator reinforced with carbon fiber fabric is investigated. To characterize the DEAs and to detect the damage, different analysis methods, which are already established for other materials, will be tested. Methods such as classical microscopy and less-known lock-in thermography are presented.

(Following abstract is for Invited industry talk - no poster will be prepared on powerpoint) At Toyota, there is a growing interest in advancing mobility for all, characterized by future mobility solutions capable of accommodating occupants of varying sizes and diverse needs. Achieving this objective necessitates highly adaptive designs capable of reconfiguring and adapting to occupant size, environmental conditions, and performance criteria. One facet of this endeavor is the development of safety enablers, such as airbags, energy-absorbing pads etc. that are capable of adopting to occupant size and position to optimize protection. We are actively pursuing innovative solutions, including reconfigurable and programmable soft energy-absorbing surfaces. These solutions integrate various concepts such as origami structures, electrostatic clutches, shape memory polymers, and other smart materials and sensors into inflatable structures to provide occupant protection during impacts. We are also looking into how such soft inflatable and actuators can help robots that can work with humans. We plan to share our current research interests, the technology under development and examples of such systems already developed to enhance safety and comfort. We will also share key challenges in developing such reconfigurable features in the vehicles.

Wearable technologies have made significant progress in recent decades. Wearables utilizing electroactive yarns have emerged and developed as a prominent technology in this respect. However, a key challenge in utilizing ionic electroactive polymer-based actuators for wearable technology lies in operation in air without the need for a liquid electrolyte. This challenge can be addressed by developing an ionogel containing an ionic liquid with mobile ions. In this study, we have investigated a two-electrode system based on ionic electroactive polymer actuators that operates effectively in air. The actuator comprises of two coiled commercial yarns coated with poly(3,4-ethylenedioxythiophene) (PEDOT)-based conducting polymers, connected through an ionogel. To evaluate the actuator's performance, we investigated isotonic and isometric tests in air by applying a ±1V potential. The latest results of the linear isotonic strain and isometric force will be presented. These findings suggest that the introduced two-electrode system holds promise for the advancement of actuator devices based on ionic conducting polymers.

Development of artificial muscles based on dielectric elastomers for biomimetic implants evolved steadily thanks to their adaptability and high flexibility. Dielectric elastomers present an important interest for various applications due to their lightweight and large deformation through the conversion of the electrical energy into mechanical work. The dielectric based actuators are electrically driven actuators which need electrodes in order to transform the external electrical energy into mechanical's one. It is rather straightforward to fabricate high quality contacts onto flexible or rough substrates such as plastics, paper, or textiles. This becomes even more difficult when constant, long term mechanical motion is added. For such applications, high electrical conductivity and flexibility are both important prerequisites since the device is expected to perform thousands of movements during its lifetime. Withal, electrospun fibers are an excellent reinforcement material, useful for manufacturing soft actuators due to their features like good flexibility, high specific area, good mechanical stability and easy to be obtained. The aim of this study is to develop a new architecture of artificial muscles based on nylon 6/6 metalized microfibers attached to a thin PDMS membrane as possible candidates for biomimetic applications. The prepared materials were analyzed from morphological, electrical and mechanical stability point of view and some actuator skills were highlighted.

The exploration and monitoring of underwater environments, such as coral reefs, present unique challenges due to their delicate nature and the biodiversity they support. Traditional underwater robotic systems often rely on propeller-driven motion, which can be disruptive to marine life and potentially harmful to the fragile coral ecosystems. This underscores the need for innovative approaches that ensure silent operation and minimal environmental impact. Soft artificial muscle propulsion solutions, such as Dielectric Elastomer Actuators (DEAs) and Hydraulicly Amplified Self-healing ELectrostatic (HASEL) actuators, into underwater vehicles have the potential to achieve superior maneuverability, energy efficiency, and adaptability in various aquatic conditions compared to conventional rigid-bodied solutions. Here, in partnership with industry, we consider the manufacturing processes and implementation of dielectric actuator muscle technology for use in medium scale underwater vehicles. To move this vessel, intend to use HASEL actuators and explore potential types of movements, including: (a) fish-like (side-to-side tail); (b) dolphin-like (up-and-down tail fin); (c) cuttlefish (undulating fin); (d) sea-snake (swimming form). These different designs have advantages and disadvantages. In this research, we are going to analise the actuator topologies and discuss means of operating them for compact underwater applications.

Dielectric elastomer actuators (DEAs) are known for their lightweight, softness, and rapid actuation capabilities, and shape memory alloys stand out for the shape memory effect and their superelastic property. This poster presents the first hybrid multi-material actuator technology using both smart materials. The superelasticity and the structurability of SMA thin films can be exploited to realize a flexible and highly conductive electrode for a hybrid smart material DEA system. This work examines the potential synergy between dielectric elastomers and SMAs, demonstrating the feasibility of the novel technology by utilizing a superelastic, auxetic structured TiNiCuCo thin film on a silicone elastomer as an actuator. The hybrid system can potentially improve the performance of actuators, by overcoming limitations of individual materials and providing new opportunities for enhanced actuation efficiency, speed and longevity.

Collaborative multi-actuator systems will become important in future applications such as robotics, medical devices, and advanced user interfaces. Potential uses for such devices range from macro to micro scales. To obtain smart, entirely soft bio-inspired robots, fully soft electronic circuits are required. Combining several multi-functional dielectric elastomers with Hydraulically Amplified Self-Healing Electrostatic actuators (HASELs), enable multi-actuator networks that combine HASEL's performance and DE's multifunctionality. This approach enables soft structures that implement basic logic computation and memory functions. We here present the application of complex DE-circuitry, to combine and intrinsically control multiple DEA-HASEL unit cells. We present a mathematical model for such unit cells and networks capable of complex actuation tasks. Drawing from our research on DE sensors and actuators, we have developed a model that integrates DE components to simulate multi-actuator networks. Multiple DE switches are interconnected through logic unit designs to achieve complex electro-mechanical behaviors. We predict the multiple outputs of a single input pulse voltage for a highly integrated inverter system through simulation. It opens more possibilities in the application field of cooperative multi-actuator systems.

With the ongoing climate crisis and UN goals of achieving net-zero by 2050, there is growing need for innovative, cost-effective renewable energy solutions. Wave energy could supply up to 10% of Europe's total energy demand. Wave Energy Scotland (WES) has been at the forefront of pioneering wave energy research, funding over 50 million GBP of projects through a series of competitive-funded programs since 2014. There are real indications of commercialisation for several devices around the world, but there are opportunities to reduce costs even further. Novel electrostatic generation technologies based on Dielectric Elastomer Generators (DEGs) and Dielectric Fluid Generators (DFGs) can directly transform movement (stretching, twisting, bending) of a material into electrical energy, i.e., Direct Generation (DG), leading to fewer structural cost centres compared to conventional devices. WES currently has a suite of enabling R&D projects which focus on addressing the R&D needs of DG, starting with two 12-month Supergen ORE Impact Hub FlexFund projects and one 4-year PhD. The University of Oxford will be investigating origami inspired DFGs, Manchester University will be investigating novel soft transducers for DEGs, and Swansea University will be will performing electromechanical fatigue life experiments for DEG and DFG systems. WES now wants to engage with academics and industry leaders at EuroEAP for the next stages of DG development.

This research investigates the integration of Distributed DE-Electronics at the interfaces of soft robotic structures, particularly focusing on enhancing collaboration between robots and humans in various domains including industrial and medical applications. By embedding soft DE sensors and electronics, this study aims to create safer and more intuitive human-machine interfaces while advancing the capabilities of soft robotics.

This work presents a dynamic design method for pumps based on dielectric elastomers (DEs), integrating resonance optimization and self-sense capabilities. Dielectric elastomer pumps offer numerous advantages but face challenges in achieving energy-efficient control and optimized operation across varying load conditions. Therefore, they are not used in everyday applications, despite their potential advantages. To address this, we propose a novel model-based design approach leveraging the dynamic behavior especially resonance optimization of the pump system. A prototype is developed, operating at resonance under maximum load conditions for consistent pressure delivery. However, lower load pressures lead to resonance shifts due to pressure-dependent stiffness changes, impacting efficiency. To overcome this, we integrate a self-sense-based frequency control depending on the load pressure inside the pump chamber. Thus, the pump can operate across its entire operating range with maximum efficiency.

The development of "4D" materials represents a promising area of research for the coming years, as these materials have the ability to change shape, volume or morphology in response to various external stimuli such as mechanical, electrical, chemical, thermal or photochemical stimulation. In this work, we explored the fabrication of electroactive 4D macroporous materials derived from a suspension of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS), an electroactive polymer. Different formulations, gelling and drying methods were first explored to select the best candidates for the elaboration of these materials, in particular for their stability in aqueous media. The selected materials were obtained by gelation in the presence of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and CaCl2, in the presence or absence of chemical crosslinker, and dried by freeze-drying. The porosity of the resulting materials was characterized using scanning electron microscopy (SEM) revealing pore sizes ranging from 100 to 200 micrometers. Under electrical stimulation in a PBS electrolyte, the materials showed an electrochemical and electromechanical response with a size variation of up to 13.5%. These findings suggest the potential of these materials for the development of electromechanically active 4D scaffolds.

This study proposes a vibration excitation technique using a dielectric elastomer actuator (DEA) applied an electro adhesion technique. Vibration responses of mechanical structures are experimentally analyzed through the vibration experiment for evaluation of their mechanical characteristics. These days, the vibration experiment are required for quality assessment of fruits and vegetables. The vibration excitation method should be non-destructive and adapt to fruits' complex surface. Therefore, conventional excitation technique (e.g. impulse hammers, lead zirconate titanate actuators) are not suitable for them. Herein, a DEA can be applied to the vibration excitation. The DEA can fit to the structure with curved surface and excite vibrations owing to its features of high flexibility, stretchability, and fast response. Here, conventional DEAs are attached to the target structures by adhesives. To compose automated experiment systems for quality assessment of fruits and vegetables, DEAs without adhesives should be applied. In this study, the electro adhesion technique, which can generate an electrical attraction force was applied to the DEA. The proposed DEA was fabricated by stacking two different layers composed of elastomers and electrodes. Then, a preliminary vibration experiment for an aluminum cylindrical shell was conducted using the proposed DEA. Finally, the effectiveness of the proposed method was evaluated based on vibration responses of the target structure.

Electrodes are of great significance regarding the softness and response time of dielectric elastomer (DE) transducers. Moreover, electrodes provide an adhesive function between prefabricated DE layers, especially in multilayer structures. However, electrodes are often not given sufficient consideration when investigating the behavior of DE transducers. On the one hand, the electrical capacitance is a measurable parameter that can be used to describe the storable energy, taking the driving voltage into account. On the other hand, the electrical resistance of the electrode material causes dissipation of supplied energy. This contribution investigates the effect of the different electrode materials on the capacitance and resistance of multilayer DE transducers produced with various printed electrode materials. An automated test rig is designed to measure the DE transducers' capacitance and resistance under mechanical stretching, and depending on the actuation cycles. Measurements are conducted using varying electrical actuation cycles and stretching cycles. Results regarding the DE transducers' material choice and their performance impairments are discussed.

In the broad domain of soft robotics, electrostatic actuators utilizing compliant materials like electro-ribbon actuators, stand out for their promising capabilities. These actuators offer useful features, including light weight, high efficiency, extensive scalability, and direct electrical control, positioning them at the forefront of advancements in soft robot application. Despite their potential, a thorough understanding of their underlying mechanics has not been fully developed. We introduce an electromechanical model that integrates large deformation beam theory and then validated by experimental results. This model elucidates the actuation mechanism and forecasts the quasi-static behavior of electro-ribbon actuators, thereby contributing valuable insights into their operation. Additionally, we explore the role of various insulation materials in enhancing actuator performance, offering guidance for optimizing design and material selection in soft robotic applications.

Electrostatic 3-phase actuator consists of two flexible printed circuit boards with 3-phase electrodes that slide over each other. The actuators have been around since 1990's and have generated forces up to 300N. Our 3-phase electrodes consist of 60 ?m wide parallel traces placed 130 ?m apart are coated by a 40 ?m thin dielectric to prevent breakdown. Because of this thin dielectric fringe fields are generated. When two actuators are placed on top of each other with silicone oil in between them these fringe fields interact and make it move one step. Each time the 3-phase actuation signal changes the actuator moves another step. Because of the potential difference between the electrodes on the top and bottom slider, there is a blocking force that pulls them together. To get motion the force moving the two PCBs must exceed the friction force between them. When designed with a high permittivity dielectric like P(VDF-TrFE-CTFE) the actuator acts like an electrostatic clutch creating more forces blocking forces than moving forces; this is generally solved by using small glass beads to reduce the friction. With a very low permittivity Parylene HT dielectric we were able to fabricate an 8 cm2 electrostatic 3-phase actuator that can produce 1.5N at 5 kV without using glass balls. By in the future rolling up the actuators, integrating fuses, and encapsulating them we will aim at fabricating self-supporting reliable electrostatic actuators with tens of newtons of force.

This work discusses power electronics to drive highly-capacitive loads while recovering most of the stored energy in closed cycles. As power electronics, half-bridges and multilevel topologies are reviewed, which are based on gallium nitride semiconductor transistors and zero-voltage-switching by closed-loop hysteretic current control. High electrical energy recovery efficiencies are reported for ideal (almost lossless) capacitive loads. For emerging solid-state heat pumps, electrocaloric ceramic capacitors are driven and experimental results are shown. Here, the electrical field change causes an almost fully reversible temperature change, and in closed cycles the stored energy in the capacitive component is recovered efficiently. The shown power electronics approach is also applicable to polymer-based electrocaloric capacitors, or other electromechanical components in future. For load capacities above 1 microfarad, charged and discharged by the power electronics up to around 400 volts, with a cycle frequency in the range of 1 to 1000 Hertz, high energy recovery efficiencies beyond 99% are experimentally demonstrated.

Reliability and lifetime are critical factors in assessing the market competitiveness of DET technology, alongside with general properties, i.e. sensor accuracy, actuator performance, or generator efficiency. These attributes are influenced across all product levels and development phases. Their assessment and improvement require comprehensive electromechanical testing, including both short-term and long-term experiments within various operational and environmental conditions, and simultaneous testing of various test objects for accelerated statistical evaluation. In previous work, a comprehensive modular test rig has been proposed that enables simultaneous long-term testing of numerous DETs within controlled environments, and under the specification of mechanical and electrical control parameters. However, this test rig has limitations in providing synchronized electromechanical control, and enabling simultaneous measurement of electrical properties, i.e. electrode resistance or dielectric permittivity during high voltage actuation. These functionalities are crucial to provide more realistic testing conditions for DET-based systems, investigate their self-sensing properties, and to be able to access statistical relevant data with respect to short-term testing conditions. Therefore, this poster presents an upgraded test rig version incorporating these functions, demonstrated through comprehensive electromechanical tests conducted on a representative DET type.

Dielectric elastomer actuators are utilized in soft robotics and biomedical applications. Among these, polydimethylsiloxane elastomers are distinguished by their remarkable elasticity (up to 5000%) and biocompatibility. However, their low dielectric constant requires the application of high voltages (> 500 V) for actuation. To address this challenge, the incorporation of gelatin, a protein fragment derived from collagen, into silicone elastomers is explored. In this study, the facile incorporation of gelatin into silicone elastomers was proposed, and the impact of gelatin morphology on the dielectric properties of silicone elastomers was investigated. Silicone-gelatin blends showed an increase in dielectric permittivity, from 3,5 to 4,5, when 2 % wt. gelatin was incorporated into the sample, while the gelatin temperature upon mixing was shown to influence the morphology of the mixtures and dielectric properties of the elastomers.

Dielectric thin films of polymeric materials are very popular for mechatronics applications; in particular, for the realization of capacitors, printed electronics, and flexible transducers. For these purposes, they are frequently employed as base substrates on which patterns of conductive and, eventually, other insulating materials are deposited to manufacture multilayer devices, where the dielectric thin films typically act not only as a supporting structure but also as an energy-storing and -converting element. There is strong evidence that the performances of the final manufactured devices, whose operation often requires exposure to high voltages, are significantly affected by the electrical and tribological properties of the dielectric thin films involved in their fabrication. This work presents the results obtained from the characterization of the dielectric constant, dielectric strength, surface roughness and static friction of commercial polymeric thin films, having a thickness comprised between 12 and 25 micrometers and made of different plastic materials. Subsequently, the implications of the identified electrical and tribological properties on the performances of electro-adhesive devices (EADs) are experimentally investigated by correlating them with the shear-stress results measured on EAD specimens manufactured with the same dielectric thin films and featuring inkjet-printed electrodes.

Intelligent fiber-elastomer composites and intelligent textiles are both active research areas in the fields of soft robotics and wearables. Tailored properties for these applications can be obtained by tailoring textile structures and fiber functionalities, such as integrated sensor or actuator properties. This work focuses on developing filamentary conductive polymer actuators for use in soft robotics or wearables. The actuators are based on wet-spun poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) fibers, with Polypyrrole (PPy) electropolymerized onto the PEDOT:PSS fibers surface. By varying the duration of PPy electropolymerization, and thus the thickness of the PPy coating, this study investigates its effect on the mechanical and actuation properties of the fibers. The developed actuator fibers achieve a repeatable high linear contractile elongation of up to 1.7%, tensile forces of about 100 mN, and mechanical stresses of about 1 MPa. Such properties make these fibers a compelling choice as a base material for textiles to be integrated into soft robotics and wearables.

Dielectric Elastomer Actuators (DEAs) require high driving voltages (typically in the order of kV) to generate meaningful displacements. As DEA technology becomes more spread, the availability of small, inexpensive, lightweight, and low-power driving electronic circuits becomes an essential requirement for real-life applications. In attaining rapid and precise voltage regulation for DEAs, the formulation of model-based control algorithms is of fundamental importance. This work presents the development and validation of feedback control techniques of a high voltage electronic for capacitive loads. The electronic is small (13 cm × 5 cm), lightweight (5 g), cheap (~20 $ based on off-the-shelf components), and generates voltages within 0-3 kV in response to a 0-6 V input signal. The circuit consists of 2 main stages, namely charging and discharging stages, which are driven by 2 complementary PWM signals. The goal of the control algorithms is to generate a proper PWM control signal, such that the output voltage follows a desired trajectory with high closed-loop bandwidth and accuracy. Finally, the control techniques are validated through numerical simulations and experimental campaigns.

Soft systems with embedded incompressible fluids are used as tuneable lenses, hydraulic actuators, and are at the heart of hydraulically amplified electrostatic actuators including HAXELs, Peano-HASELs and EBMs. These multi-material devices generally require manual filling with a liquid, for instance using a needle. Such processes are not readily scalable to industrial manufacturing. In this work, we present an inkjet-based process in which the working liquid is directly embedded in the actuator during device fabrication. We print the working liquid after printing the bottom of the device. We then freeze the droplets, and finally encapsulate them. We use this method to fabricate hydraulically-amplified taxels (HAXELs) using inkjet-printed silicone dielectric layers, carbon electrodes, and encapsulated oleic acid having a freezing point between 11 and 14 degrees Celsius. The 5 millimetre-wide devices generate up to 400 micrometres out-of-plane displacement at 3 kilovolts. The absence of filling channels allows high density arrays of 5 millimetre-wide actuators with only 0.5 millimetre gap between devices. These results open the door to an upscaled industrial fabrication of customized fluid-filled soft systems.

HASEL (Hydraulically Amplified Self-healing ELectrostatic) actuators are a new class of smart actuators with a unique weight to power ratio driven by an electric field. The HASEL actuator consists of two polymer films (PET, TPU etc.), sealed to a pouch and filled with an insulating oil. The polymer films of the sealed pouch are partially coated with a pair of electrodes on the outer sides. The zipping effect moves the insulating oil inside the pouch to the area without electrodes and deforms the pouch macroscopically. The authors of this paper present HASEL actuators with the area size of 20 mm x 30 mm, fabricated with a semi-automated sealing technology, where four of these actuators are manufactured as a serial chain in one manufacturing step. The HASEL chains are inserted into a flexible 3D printed TPU support structure with a Shore A hardness of 95, which reflects the structure of a flexible finger of a robot gripper. Overall, 20 single HASEL actuators, split into 5 chains, are activated in series with a maximum driving voltage of 9 kV. They bend the flexible support structure with an angle of 43° and an overall displacement of the finger tip of 21 mm. The gaps for the HASEL actuators inside the flexible finger structure were optimized in their geometry to improve the bending behaviour and to reduce unwanted pre-bending. The so created flexible finger structure with integrated HASEL actuators is directly usable for soft grippers and other soft robotics applications.

In this talk, exciting possibilities of utilizing twisted and coiled actuators in heat engines to generate mechanical work will be discussed. Nylon 6,6 stands out as the most suitable material for these actuators because of its high thermal expansion ratio, high softening point, and stiffness, allowing it to withstand significant twisting. An established engine design has been remodeled that previously used shape memory alloys with a higher expansion ratio and replaced it with Nylon fibres. A theoretical framework has been developed to establish a connection between the mechanical output of the engine and the characteristics of the actuator material, enabling the comparison of the performance of this artificial muscle. Material properties required to maximize engine output and speculate on potential material structures that could further enhance engine performance are identified. Further discussed will be the making of these nylon fibres and how the actuation generates the energy required to not only run the engine but also, maximize the output by lifting different masses attached through the pulley.

Reconfigurable modular robots are versatile and sustainable design options compared to fixed robotic designs. When driven by soft actuators, their modular units offer additional features like adaptability and design freedom - but current soft-actuated modules are limited in stroke, speed, and ease of reconfigurability. We introduce hexagonal electrohydraulic (HEXEL) modules - soft electrohydraulic actuators contained in a stiff exoskeleton - which generate high stroke (49% strain), high-speed (4,618%/s) actuation and offer a versatile platform for hosting magnetic, rapidly reversible electrical and mechanical connections between neighboring modules. These modules are additionally capable of untethered operation, allowing for new avenues of reconfigurable robot design.

Dielectric Elastomer (DE) actuators are under research since more then 20 years and the first DE actuators found their way to commercial applications as stack actuators. The performance of DE actuators can be dramatically improved by a pre-stretch of the DE film while manufacturing, which usually results in a high production effort. The authors of this poster present a DE bending actuator based on the unimorph working principle, without pre-stretch while manufacturing. The DE actuator was manufactured with single films of Wacker Elastosil (100 µm thickness), coated by 1k-dispensing with electrodes with an area of 30 mm width and 50 mm or 80 mm length. Eight of such DE films with electrodes were laminated to a stack. In the following step, the DE stack were laminated to a passive stiffening layer of Kapton with a thickness of 25 µm or 50 µm or Dynacode with a thickness of 70 µm. Finally stiffening bars were applied to the DE surface to prevent an additional bending of the DE actuator perpendicular to the intended axis. The DE actuators were tested in terms of their bending performance with up to 50 kV/mm electrical field strength. For the DE actuators with Dynacode stiffening layer, a bending angle of 54° and a tip displacement of 20 mm could be reached, as predicted by additional calculations. For further developments, the combination of unimorph DE actuators with an electroadhesion layer was successfully tested and offers a huge potential for soft robotics applications.

Dielectric elastomers actuators (DEAs) are particularly lightweight, stretchable, flexible, and soft transducers, thus they are suitable for the development of wearable 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 to develop miniaturized, fully-polymeric, and large stroke DEA systems. In comparison to silicone-based domes and metal beams, they exhibit less hysteretic losses while maintaining high softness and flexibility. Their mechanical characteristics can be arbitrarily shaped by changing the thermoforming process parameters, as well as the biasing element layout and geometry. This poster explains the thermoforming manufacturing process, and demonstrates its reproducibility by experimentally characterizing and comparing the force-displacement behavior of several biasing elements with various geometries.

Soft robotics technologies have been recently growing with a lot of focus in developing better functional soft robot. However, to improve the performance of the soft robot, soft matter computation is very important to achieve the next level competence. The ability to integrate computational properties using soft materials, would come in a long way of achieving the goal of fully functional soft robot. Hence the current work focuses on soft material mechanism for the integration of logic by sending a digital or analog signal to the soft robot. Two liquid phases, a conducting and a non-conducting phase where used. The conductive liquid phases and the nonconductive liquid phases acts like an on/off switch. Depending on the size of each phase and how fast the phases are flowing, the setup can be also imagined as a function generator sending a PWM signal. The conducting phase is considered a high signal and the non-conductive phase a low signal. The signal is sent and amplified to an soft robot/actuator using Surface Mount Device (SMD) transistor circuit. The actuation occurs due to the change in voltage or current. The results obtained is promising for a possibility of building such a hybrid soft matter computers. Such hybrid soft matter computers would come a long way in development of electronics free fully autonomous soft robots and actuators.

Recent advancements in electronic skins (e-skins) have significantly improved the ability of robots to interact delicately with objects and ensure safe human-robot interactions. However, the broad adoption of e-skins in robotics is impeded by the complexities associated with their integration, particularly at higher resolutions. Traditional capacitive tactile sensors, while simple and robust, require extensive wiring and complex electronics as they scale, which increases cost and complicates manufacturing. Addressing this challenge, our study introduces an innovative approach by integrating a multifrequency method with supervised machine learning to enhance the functionality of e-skins without the need for complex sensor wiring. We present a novel soft capacitive monolithic sensor that is straightforward to manufacture and uses only two sensor wires. By leveraging machine learning algorithms, our models accurately localize touch interactions within a 5-zone area and quantify both the force and location of touch within a 3-zone area. In live tests, the models demonstrated over 90% accuracy in predicting button presses. This high level of precision indicates that combining soft capacitive sensors with machine learning not only resolves the issue of scalability but also significantly reduces the complexity and cost of e-skin technology, paving the way for more widespread implementation in advanced robotic systems.

This contribution proposes a novel integration of Hydraulically Amplified Self-Healing Electrostatic actuators (HASELs) with dielectric elastomer switches (DESs) to create versatile and adaptive systems, capable of precise deformation and actuation in multi actuator systems. DES possess the ability to integrate signal processing capabilities directly into soft multiactuator systems, enabling complex actuation patterns, without or with minimum external control signals. The integration involves HASEL actuators to deform and stretch a stretchable membrane made of silicone elastomer possessing DESs printed on top of it. This innovative approach capitalizes on the unique properties of both HASEL actuators and dielectric elastomers, enabling digital signal processing embedded in soft actuator networks. HASEL actuators, known for their high force output, rapid response, and self-healing capabilities, serve as the driving force behind the deformation of the silicone membrane. The precise and localized deformations of the stretchable membrane holding the DES generates the control signals for neighboring actuator units. This combination of HASEL and DES forms digital unit cells that are used to directly control the actuation of connected DEAs, enabling the set-up of basic digital logic functionality in multi-actuator arrays.

Electroactive liquid crystal elastomers (eLCEs) have been used to make actuators and soft robotics. However, most eLCEs are monofunctional with one type of deformation (bending or contraction). Recently, we have reported a trilayer eLCE by combining ion-conducting LCE and ionic electroactive polymer device (i-EAD). This i-EAD-LCE is bifunctional and performs either bending or contractile deformation by controlling low-voltage stimulation. Nevertheless, it has a Young's modulus of only 1.63 MPa. To improve the mechanical performance, the i-EAD-IPN-LCE is prepared here, whose central membrane is composed of interpenetrating LCE and ionogel (i-IPN-LCE) instead of a single ion-conducting LCE. This i-EAD-IPN-LCE with a typical thickness of 0.5 mm can function not only as linear and bending actuators, but also as a sensor. As a linear actuator, its Young's modulus, actuation stress and actuation strain are 51.6 MPa, 0.14 MPa and 9%, respectively, reaching skeletal muscles' values. As a bending actuator, its bending strain difference is 1.18% with 3 mN output force. It can also operate as a sensor producing 0.4 mV Open-Circuit-Voltage to respond to bending deformation (bending strain difference = 9%). Therefore, this i-EAD-IPN-LCE is a promising system for the fabrication of robust electroactive devices and sensors with multiple degrees of freedom.

Dielectric elastomer actuators (DEAs) are used in various applications. To achieve the high performance, homogeneous charging and discharging properties are indispensable and depend on various aspects, such as the homogeneity of the electrode resistance or the design of the electrical connection. This poster provides a new approach, in which thermal imaging is used to characterize these aspects for DEAs. It utilizes an artificial increase in the charging current by applying high frequency sinusoidal voltage signals, resulting in relatively low actuation response along with high joule heating. This heating is particularly pronounced in areas of inhomogeneous current distribution and can be visualized by conducting thermographic methods. Analyzing corresponding temperature gradients can be used to make statements about the homogeneity of the charging. In a first study, different geometries of electrical contacts are examined. The DEAs are set to different strain levels, while varying excitation frequencies and voltage amplitudes. Poor contacting leads to inhomogeneous charging characteristics. Improving the contacting geometry significantly reduces the measured temperature and leads to a more homogeneous current flow in the DEAs, thus a more homogeny charging behavior of the DEAs. The results of this work provide an initial insight into the charging behavior of DEAs by means of thermal imaging and will enable to optimize charging processes in the future.

Dielectric elastomer actuators (DEAs) are composed of a thin dielectric elastomer membrane that is sandwiched between two compliant electrodes. When an electrical voltage is applied, the film compresses in the thickness direction and expands in-plane. However, many technical applications require uniaxial deformation. For this purpose, the introduction of mechanical anisotropy by unidirectional fiber reinforcement is commonly used. State of the art publications utilize evenly spaced stiff fibers that are bonded to the dielectric film. These fibers inhibit the deformation of the actuator in the fiber direction, which ideally keeps the width of the actuator constant, leading to increased electro-active forces and strains. However, they also constrain the actuator lengthwise because the material below the fibers can hardly deform. Therefore, the fiber coverage ratio is an important parameter when designing actuators with this kind of reinforcement. As an alternative approach, a composite layer consisting of unidirectional fabric with a soft elastomer matrix can also be used. These reinforcement layers lead to comparable mechanical anisotropy. However, as the stiff fibers are not directly bonded to the dielectric, the actuator's lengthwise stiffness is not significantly increased. This work investigates the effect of these two types of reinforcement on the actuator properties.

Smart Textile is a branch of functional textiles with a built-in ability to respond to various stimuli like chemicals, light, or electricity. The key component of these textiles is "smart yarn" which is engineered to respond the external stimuli. Traditionally, smart textiles focused on textile-based sensors. Now the focus is shifting to the development of yarn and fabric actuators. Yarn coated with Poly-3,4-ethylenedioxythiophene: Polystyrene sulfonate (PEDOT: PSS) and polypyrole (PPy) acts like a soft actuator. When these smart yarns are exposed to an electrochemical potential, the PPy coating contracts and expands, like an artificial muscle. The thickness of the PPy coating impacts the actuator's performance. A thicker coating can generate greater force but might be less responsive (slower contraction/expansion). This paper investigates the effect of PPy thickness on the performance of yarn actuators. The passive yarns were dip-coated with a conductive Poly-3,4-ethylenedioxythiophene: Polystyrene sulfonate (PEDOT: PSS), Dimethyl sulfoxide (DMSO) and Polyethylene glycol 400 (PEG 400) mixture to make them electrically conductive yarns. Then PPy with different thicknesses were deposited using an electro-polymerization process. The resulting yarn actuators were then evaluated for three key properties: strain, speed of movement, and force generation, using a lever arm setup.

Silicone-based dielectric elastomers have emerged as promising devices for a variety of sensing and actuation applications. Their primary drawback is the requirement for high driving voltages for actuation due to their relatively low dielectric permittivity. Enhancing the permittivity of silicones can be achieved through the incorporation of fillers such as: metal oxides, metal nanoparticles, and carbon nanoparticles. However, traditional filler materials often exhibit rigidity and inherently lack compatibility with silicone elastomers. Utilizing functionalized silicone oils as soft fillers offers a means to enhance the dielectric permittivity of the material whilst reducing the adverse effects associated with rigid fillers. By synthetically modifying the functional groups grafted to the silicone chain, the properties of the filler can be tailored to the required application. A novel, high-permittivity soft filler was synthesized by grafting an ionic liquid to a silicone chain. The synthesis process was monitored, and the final product characterized using H1 NMR and FT-IR techniques. Upon incorporation into an elastomer, the filler exhibited more than a twofold increase in dielectric permittivity compared to its pure elastomer counterpart. Notably, the breakdown strength remained high while the tan? remained low in comparison to other high-permittivity silicone elastomers.

Hollow fiber dielectric elastomer actuators (HFDEAs) offer distinctive capabilities in soft robotics due to their unique structure and electromechanical performance. This research focuses on how specific design parameters, including the shape and material properties, such as the inner diameter and elasticity (Young's modulus), impact the electromechanical properties of HFDEAs. These parameters were chosen due to their measurable influence on actuator performance and their relative simplicity for experimental verification. By employing finite element method simulations in COMSOL Multiphysics, we explored the interplay between electrical and mechanical forces within the actuators. We found that differences in surface charge density between the external and internal electrodes not only cause the actuators to stretch but also to widen, a characteristic effect of the hollow fiber structures. Additionally, our simulations offer insights into the actuator's holding force-a metric traditionally difficult to quantify-highlighting how strategic parameter tuning can significantly boost performance. Ultimately, our findings pave the way for a systematic design strategy for HFDEAs, combining experimental insights with computational predictions to optimize the designs. Keywords: Dielectric Elastomer Actuators, Finite Element Method, Electro-Mechanical Modeling, Hollow Fiber Dielectric Elastomer Actuators.

Wearable textiles with mechanical actuation are of great interest for their use in haptics or assistive devices. During the last years we have been developing soft actuators based on ionic electroactive polymers (polypyrrole) in form of tape yarns that have been integrated into textiles through textile processing techniques such as weaving to obtain actuating fabrics. Tape yarns were produced by electropolymerizing Polypyrrole in both sides of an Au coated polyvinylidene fluoride (PDVF) membrane which is then soaked in the ionic liquid choline acetate forming a trilayer tape yarn polypyrrole/choline acetate soaked PVDF membrane/polypyrrole. Thus, when an electrical charge is passed through the trilayer, it produces a bending motion in air, outside of any liquid electrolyte. One of the key aspects for their applicability is their lifetime, an aspect that has not been properly studied before. Here we present the latest results about the lifetime (number of cycles) of such EAP based tape yarn actuators, when different potentials are applied.

As the population ages, the demand for home and care robots is growing. For safe interaction with humans, tactile information is indispensable. Flexible tactile sensor arrays allow robots to safely interact with their environment via touch and reduce the possibility of injuries when humans interact with machines. Many tactile sensor arrays for robotic applications have been presented in the past. However, most of them are complex in design, require complicated processes and expensive materials to manufacture and place high demands on circuit devices. In this paper, we present the design of a fully soft, flexible and stretchable tactile sensor array that can be produced using low-cost materials and widely available devices, has low requirements on circuitry, and is free of ghost signals. The sensor is stretchable, due to its mechanical compliance, it can fit on irregular surfaces and can have customized shape, spatial resolution, and detection thresholds. The sensor's measurement and communication module measures only 35 x 25 mm can be wired or battery-powered and enables Bluetooth communication. Thus, this sensor has broad potential for commercial applications. We present the fundamental functionality of the sensor, the applied production technology and an experimental study on its performance in several applications.

Magnetic and electric fields are interesting physical phenomena. Modern manufacturing methods have allowed us to fabricate transducers that exploit these two phenomena. Our actuator is a round membrane consisting of a magnetorheological elastomer and dielectric electroactive polymer. In our actuator we use the magnetic field to move the membrane, and varying capacitance gives us information about the position of the membrane. We propose to use our actuator with an integrated sensing system to give information about membrane position. In this poster, we present the results of changing actuator capacity from actuator position. This poster aims to show how significant is capacity change in real membrane and the correlation between membrane position and membrane capacity.

Flexible and stretchable electronics, such as multi-layer capacitive strain sensors utilizing dielectric elastomers, have garnered substantial interest owing to their inherent sensitivity, extensive deformation capabilities, and adaptability to intricate geometries. This contribution endeavors to propel the development of dielectric elastomer strain sensors by exploring novel methodologies aimed at enhancing stability, sensitivity, and manufacturability. A comprehensive classification of dielectric elastomer sensor structures, incorporating four electrode layers, including a novel 50µm-capacitor configuration, is introduced to optimize capacitance and sensitivity. Additionally, the study scrutinizes electrode pin designs, evaluating their technological effectiveness and mechanical stability through simulations and validation processes. A novel upside-down fabrication technique is introduced to streamline production processes and bolster reliability. Furthermore, finite element simulations are employed to elucidate the deformation behavior and capacitance variance of stacked sensor structures under diverse loading conditions. This research advances the flexible sensor technology field, particularly benefiting applications in soft- and micro-robotics, sensor-integrated machine elements, and related domains.

Smart textile actuators have been of growing interest due to their applications in soft robotics, exoskeletons, and assistive garments, and can deform controllably and reversibly under application of an external stimulus such as temperature or electric potential. This next generation of smart textiles integrate smart yarn and fiber actuators, and/or the deposition of smart materials in/on textile substrates. The mechanics of the textile substrate used for these actuators has an effect on the performance of the devices, and can be used advantageously to achieve complex actuation modes. Additionally, additive manufacturing processes can be used to fabricate the actuators, providing a means to quickly modify and adapt the patterning of both active and passive materials to further enhance performance. In this study, multi-layered PEDOT:PSS actuators were 3D printed on different woven textiles via syringe-based extrusion to explore the effects of the weave pattern on actuation performance. Furthermore, passive materials were printed in different patterns, utilizing selective compliance to program the movement capabilities of the devices.

Elastic membranes aligned in a fluid flow can suffer from a hydroelastic instability called flutter. This is characterized by large amplitude membrane displacements that are of a periodic nature and that occur above a speed when hydrodynamic forces are comparable with elastic forces. For capacitive sensors this can be a problem because these sensors work through capacitance change associated with flow induced membrane-stretch. Periodic sensor membrane stretch exaggerated by a flutter phenomenon will cast doubts on the veracity of the flow/force measurement. Membrane flutter can be mitigated through stiffening and tensioning the membrane. The bat wing, for instance, employs directional stiffening of its flight membranes. While developing membrane sensors for a fish-like robot we have encountered membrane flutter. This has been manifest on two sensor types: one for measuring pointing direction of the robot (rheotaxis) and the other for measuring the force developed in a bionic fin. In this presentation we will show how we have mitigated this problem for both sensor types.

In this work, we present recent advances on modeling, design, and control of a soft robot driven by rolled DEAs. The module exhibits a T-shaped structure made by two plates connected by a flexible backbone, compressed by two pre-tensioned rolled DEAs. When actuated via high voltage, the DEAs expand and the soft structure bends toward the desired direction. By optimizing the system geometry via a model-based design approach, we trigger by the DEA activation the buckling instability of the beam, resulting in a bi-stable actuation with large bending angles. Despite bi-stability improves the system motion range, proportionality of regulation is lost. To recover it, control strategies based on a passivity framework are adopted. The method is validated experimentally on a real-life prototype based on camera feedback. Experimental results confirm the effectiveness of the stabilizing control approach. While the adoption of a camera feedback is an acceptable choice for initial controller validation, it is not a suitable sensing method to integrate the system in an unstructured environment. To overcome this limitation, a real-time self-sensing scheme is proposed. Based on a real-time processing of voltage and current, the proposed architecture allows estimating the configuration of the soft structure without requiring additional sensors. Finally, first steps towards the model-based design and validations of a three-dimensional version of the DE soft robotic system are presented.

Dielectric elastomer (DEs) are highly stretchable polymeric transducers that are used to convert an applied electric voltage to a controllable deformation. In most applications, DEs are used as independent actuator/sensor systems. New research interests encompass cooperative systems, leveraging on the self-sensing abilities of DE Actuators (DEAs) for lightweight, compact, and flexible solutions. Differently from the stand-alone actuator case, cooperative self-sensing paradigms allow multiple interconnected actuators to estimate not only their own displacement but also that of their neighbours, based on electrical measurements only. This information can then be used to execute complex tasks through the cooperative control of multiple actuators. To effectively develop and optimize cooperative DEAs, however, numerical tools and simulation models are required. This work focuses on a 1-by-3 array of DEAs sharing a common flexible membrane. The goal is to understand the relationship between the capacitive states of the DEAs and the array deformation, enabling the reconstruction of deformation patterns for different actuation scenarios. Moreover, a non-linear finite element model of the DE array accounting for large deformation, electro-mechanical coupling, and geometry is proposed to describe and capture the actuation and sensing features of the system. These results will pave the way for the future development of cooperative control algorithms for interconnected DE array systems.

In recent years, snap-through instabilities in inflated dielectric elastomer actuators have been harnessed to enable large voltage induced deformation. Similarly, snap-through instabilities in interconnected inflated dielectric elastomer actuators have been shown to enable achieve ultrafast actuation and programmable multistable states. Due to the non-material behaviour and complex interplay in interconnected dielectric elastomer actuator systems, it is difficult to analytically model them. Addressing this challenge, we have developed an analytically model for a system of three interconnected dielectric elastomer spherical actuators and devised graphical and numerical approaches to solve for the equilibrium states. The results show a rich landscape of different snap-through instabilities and multistable behaviours that can be achieved in such system. A locus of initial stable states has been identified and the initial conditions can be adjusted to realize a system with multiple states. Analyses shows that in certain conditions, switchable stable states can be realized through selective actuation of a specific actuator in the interconnected systems. Furthermore, a new behaviour of cascading instability in which an actuator undergoes successive snap-through instabilities with monotonic increase of actuation voltage has been identified. We hope this work will propel programmable design of multistable soft systems for soft robots and stretchable electronics.

Dielectric elastomer transducers (DETs) have gained significant interest due to their promising applications in various fields such as sensors and actuators. Characterization and electromechanical analysis of DETs is crucial in research and development to evaluate and optimize their properties. In previous work, a versatile testbench had been presented including a confocal sensor system delivering thickness measurements along one axis. Thickness measurements are of relevance for the characterization of film quality on the one hand, but they also enable an electric field estimation based on applied voltage. Non-contact measuring of thin, highly flexible films is a key challenge, especially due to variations in transparency, reflection, or light absorption. This poster presents a new setup, which enables increased precision with low-vibration operation, allowing for enhanced automatic screening to yield thickness . Additionally, a camera system aimed at the film surface with a digital image correlation algorithm provides the possibility to obtain planar strain fields. Based on these data and using an incompressibility assumption, the calculation of local thickness strains for an entire sample becomes possible. The confocal measurement of a single profile line can then be used to calibrate and subsequently calculate average thickness distribution without having to screen line by line.

Smart wearables, increasingly popular due to technological advances, have diverse applications in medical, industrial, and gaming fields. However, they must be wearable, adaptable, flexible, lightweight, and intuitive. This necessitates the integration of flexible sensors and actuators into clothing fabrics, a challenge addressed by Dielectric Elastomer (DE). DEs are lightweight, highly stretchable transducers capable of simultaneous sensing and actuation. This work introduces a DE-based wearable device providing haptic feedback. The device comprises an air-inflated pouch, pre-stretching both passive and active DE membranes. Activation softens the DE, altering the actuator's internal pressure and the force exerted on the skin. The device's advantages include the ability to change internal air pressure without an external pump, adjust actuation intensity and speed, and reduce production costs by using the active membrane as both sensor and actuator. Future developments aim to create a self-sensing system that achieves desired performance by sensing its own internal pressure while actuated, via a suitable control algorithm.

Ionic polymer-metal composites (IPMCs) have a wide variety of applications as they can act as both sensor and/or actuator. The effects of process parameters on the electroless plating of IPMCs were studied in this work. Specifically, sodium borohydride (NaBH4) reduction of platinum onto Nafion-117 was characterised. The effects of concurrent variation of NaBH4 concentration, stir time and temperature on surface resistance were studied through a full factorial design. The 3 factor 3-level factorial design resulted in 27 runs. Surface resistance was measured using a four-point probe. The fitted responses resulted in a regression model with an R2 value of 97.45%. Temperature was found to have the most significant effect on surface resistance. Generally, surface resistance was found to decrease with increasing stir time (20 minutes to 60 minutes) and temperature (20°C to 60°C). Surface resistance decreased going from 1% to 5% NaBH4 concentration, but increased from 5% to 10% NaBH4 concentration. Maximum tip displacement, measured through a computer vision system, was obtained for all 27 samples. Highest displacement obtained was 65.9mm at 10% NaBH4 concentration, 60 minutes stir time and a temperature of 40°C.

Robotic locomotion in unstructured terrain demands an agile, adaptive, and energy-efficient architecture. To traverse such terrains, legged robots use rigid electromagnetic motors and sensorized drivetrains to adapt to the environment actively. These systems struggle to compete with animals that excel through their agile and effortless motion in natural environments. We propose a bio-inspired musculoskeletal leg architecture driven by antagonistic pairs of Peano-HASEL artificial muscles. Our leg mounted on a boom arm can adaptively hop on varying terrain without using joint angle feedback in an energy-efficient yet agile manner. It can also detect obstacles through capacitive self-sensing. The leg performs powerful and agile motions up to 10 Hz and high jumps up to 40 % of the leg height. Our leg's tunable stiffness and inherent adaptability allow it to hop over grass, sand, gravel, pebbles, and large rocks using only open-loop force control. Our leg features a low cost of transport (0.73), and while squatting, it consumes only a fraction of the energy (1.2 %) compared to its conventional electromagnetic leg. Its agile, adaptive, and energy-efficient properties would open a roadmap toward a new class of musculoskeletal robots for versatile locomotion and operation in unstructured natural environments.

The study of mechanotransduction signals in cells is of great interest because of their implications on the onset of various diseases such as cancer, osteoporosis, or asthma. One way of studying such signals is by applying external mechanical stimuli that affect cellular functions. To date, these stimuli have been performed using magnetic or electrical fields that do not resemble real biophysical stimulation. Polypyrrole-coated wires are easy-to-handle, biocompatible microactuators to induce mechanical stress to study the mechanotransduction pathways of single-cells. In addition, their small size makes them easy to use inside a small cell culture dish. Here, we present the characterization of the actuation of PPy-coated wires with a novel non-contact optical method and its viability in cell-compatible media in three- and two-electrode cell configurations. The wire actuators are prepared by electrodepositing PPy on a 500 ?m diameter gold substrate and then actuated in NaDBS or cell culture media. The electrochemical variables are synchronously recorded with the radial actuation of the PPy using a laser scanner. The difference in the thicknesses of PPy, as well as the effect of two-electrode or three-electrode system configurations on the absolute radial actuation, strain, and consumed charge, are investigated. These results will lay the groundwork for future mechanostimulation experiments on cells and cell signalling analysis.

Soft actuators utilize many different ways of actuation that often require not only power supplies, but also devices converting its energy into different forms, such as high pressure or voltage output. Therefore many soft robotic elements remain tethered to bulky hardware, making it difficult to integrate them into wearables. One concept that offers autonomy in this field is using liquid-gas phase change actuation. This quite simple in principle technology, based on evaporation of the working fluid in enclosed, yet elastic structures, requires only portable power supplies with no need to convert its energy, while allowing to achieve numerous and unique motion types limited only by imagination. This technology has a potential to bridge the gap between emerging, but not yet fully developed concepts and the realistic, present needs of the functional clothes industry. To demonstrate this, we present our results on a concept of flexible, scalable and modular system of elements utilizing phase change phenomena. These small phase change actuation modules created by us are ideal for fashion and functional clothes owing to the fact of their compliance, simplicity of attachment to garments and moderate energy demand. Modules operation is presented in numerous setups including artificial muscle, hinge opener, mechanical instability and functional clothes demonstrator inspired by fish scale granting both protection and smart clothing features proving versatility of our concept.

Wearable mechatronic devices such as powered orthoses, exoskeletons, and prostheses require advanced soft actuation devices that function like 'artificial muscles'. These actuators should be capable of large strains, high stresses, rapid reaction, and integrated self-sensing, while also ensuring electrical safety, low weight, and high compliance. Soft pneumatic actuation has seen a resurgence in the past two decades, thanks to technological progress driven by applications in soft robotics. As of now, quite a few solutions are available to create pneumatic devices with linear actuation and self-sensing properties, using readily available materials and cost-effective manufacturing techniques. Here, we describe a straightforward process to create self-sensing pneumatic actuators that act as 'inverse artificial muscles'. Unlike traditional pneumatic actuators that contract when pressurized, these actuators elongate. They consist of an elastomeric tube encased by a plastic coil to prevent outward expansion. The innovation here is the self-sensing feature, achieved through a piezoresistive stretch sensor, which was made from a conductive elastomeric material and was arranged along the center of the tube.

A silicone fiber dielectric elastomer actuator, which mimics the fibular properties of natural muscles and provides stable linear strains up to 9% at 50V/µm in both wet and dry conditions, is being developed. The hollow fiber is prepared by employing a fast UV thiol-ene cross-linking reaction using a wet spinning technique, resulting in long thin fibers of an average diameter of 500 µm and variable wall thickness of approximately 80 µm. The fiber actuator utilizes ionic liquid as an internal electrode and ionogel or ionic liquid as an external electrode, in dry and wet state conditions, respectively. In this work, we studied multiple possibilities of the fiber preparation technique by adjusting the silicone formulation, UV light intensity, and flow rates to further enhance the actuation performance and improve the fiber robustness.

Dielectric elastomer actuators are excellent contenders for the development of terrestrial and underwater mobile robots due to their silent operation and full electric control. However, sensorizing untethered dielectric elastomer actuators for future autonomous capabilities faces challenges due to their high voltage requirement and nonlinear mechanics. To tackle this challenge, we developed a novel sensing technique by embedding a piezoresistive sensor track to simultaneously estimate the actuator displacement and external interaction force through the measurement of track resistance and feedback voltage. We have characterized the voltage-force-displacement characteristics of the actuator as well as their influence on track resistance. Through a data-driven regression model, Gaussian Process Regression (GPR) was built from the measured data for accurate estimation of force and displacement based on voltage input and feedback resistance. Validation tests were performed on three actuators in different operating conditions which demonstrate promising results, achieving low RMSE values of 29.736 mN for force estimation and 0.023 mm for displacement estimation under no-voltage conditions. Furthermore, we realized an actuator with fully untethered operation capable of force and displacement feedback to a remote computer by integrating a power source, mini voltage amplifier, microcontroller, and wireless connectivity module into a compact form-factor.

This poster introduces a novel wearable device: a waistband equipped with an array of low-cost piezoresistive sensors, made of carbon black and commercially available stretchable wound dressing materials. Optimally positioned around the waist, these sensors detect variations in strain caused by movements of the pelvis and hips. As such, the device is capable of monitoring changes in resistance to accurately identify a variety of activities, including walking and running, as well as distinguishing between movements of the legs. This poster outlines the current progress in the development of this technology, highlighting its potential applications in activity and posture monitoring.

Soft elastomer materials due to their inherently dissipative nature are the materials of choice for dampers. Damping plays a vital role in our modern society, spanning a wide range of application from shoe soles to wheels, with dampers within vehicles, in bridges and buildings or seals within appliances. Taking inspiration from living systems soft multilayered protective structures such as bones, skin or fruit peel that can not only sustain high dynamic, but also quasi-static mechanical loads while being built-up by a small range of basic materials, we present simple approaches to damping structures with adjustable stiffness based on novel silicone elastomers and their foams. We highlight their fabrication, characterization, applicability as adjustable dampers along with their sensing abilities.

Inkjet printing is a remarkably versatile and promising technique for crafting functional materials. Its ability to precisely dispense minuscule ink droplets (measured in picoliters) at the target positions empowers it to achieve high-resolution and thin-layer depositions, offering great potential for the miniaturization of flexible and stretchable electronics. In this study, we developed a novel carbon black (CB) ink and tailored it for compatibility with the small cartridge nozzles (17x17 µm) of inkjet printers. Extensive characterizations were conducted to evaluate the ink, including surface tension, viscosity, stability, conductivity, and particle size distribution. With this ink, we printed a precise pattern onto a dielectric elastomer membrane (VHB). By combining a dielectric elastomer actuator (DEA) next to the printed CB pattern, its resistance could be significantly changed accompanied with actuation and non-actuation of the DEA. More than three orders of magnitude in resistance change have been obtained at frequencies of up to 3 Hz. Thanks to its excellent piezoresistive performance, we have successfully applied this dielectric elastomer-based device as a "switch" for controlling soft grippers and as a multiplexer for signal processing.

The use of electrode arrays to interface with peripheral nerves is attracting significant interest for the diagnosis and treatment of various neurological disorders. Existing electrodes, however, require complex placement surgeries that carry a high risk of nerve injury. Here, we leverage recent advances in soft robotic actuators and flexible electronics to develop highly conformable nerve cuffs that allow for extensive and reprogrammable shape morphing into complex three-dimensional (3D) geometries. These devices combine electrochemically driven conducting polymer-based soft actuators with low impedance microelectrodes. They enable controlled shape reconfiguration of the electrode arrays into predesigned 3D architectures with applied voltages as small as a few hundreds of millivolts, allowing active grasping or wrapping around delicate nerves. We validate this technology in in vivo rat models, showing that the cuffs form and maintain a self-closing and reliable bioelectronic interface with the sciatic nerve of rats without the use of surgical sutures or glues. Moreover, they provide the flexibility to adjust the fit or release the electrode array as required. This seamless integration of soft electrochemical actuators with neurotechnology offers a path toward minimally invasive intraoperative monitoring of nerve activity and high-quality bioelectronic interfaces.

Poly(ionic liquid)s (PILs) are expected to become the next generation materials for assembling various electrochemical devices. Owing to the combination of ionic transport properties with the mechanical stability and processability of polymer materials, these polyelectrolytes became ideal candidates for creating all-solid-state devices and touch sensors, in particular. Such sensors operate on the principle of the piezoionic effect, wherein the diffusion of ions within the PIL matrix induces a variation in potential, thus enabling the detection of applied force. This work aims to create a new subclass of efficient piezoionic sensors by means of synthesizing highly conductive ionic liquid like monomers (ILMs with conductivities of 1.0x10?4 Sxcm?1 at 25 °C) and their further photopolymerization with 2-acetoxyethyl methacrylate (AAEM) and poly(ethylene glycol) dimethacrylate (PEGDM, crosslinker). Optimization of the photopolymerization conditions, including nature and amount of solvent (isopropanol:water mixture), quantity of initiator (TPO, 1 wt.%), ratio of monomers (ILM:AAEM:PEGDM=10:85:5 by wt.%) enabled the preparation of self-standing films with high conversion (95±1 %, by gel fraction) in short time (50.9±0.7 s, by gel point) displaying good mechanical properties (2.6±0.6 kPa, by DMTA). Piezoionic tests of the films revealed the liner response with increase in the applied pressure with a maximum of 51.4 mV responding to 60 kPa stress.

E-textiles are part of an exciting research avenue which merges technologies such as sensing and actuation with the textile industry. Despite the substantial progress made in recent years, there has been little work on incorporating electrostatic actuators into fabrics. Dielectrophoretic Liquid Zipping (DLZ) actuators are a type of electrostatic actuator which show promise for use in wearables, owing to their lightweight construction, silent operation, and high efficiency. However, the design is yet to be optimised for use in wearables. Currently, DLZ actuators use two thin steel electrodes which are held together at one point and separated by solid and liquid dielectrics. When a potential is applied, the two electrodes zip together, starting from their point of convergence. In this work we explore incorporating e-textiles in DLZ actuators. We compare the performance of each material and develop a proof of concept textile-based DLZ actuator. This work paves the way to embedding DLZ actuators into clothing in the future.

Elastic inflatable actuators (EIAs) are widely used in soft robotic applications due to their low cost, ease of fabrication, and fast response. Moreover, harnessing the structural and material nonlinearities of EIAs enables mechanical programmability. Nonlinear EIAs have been utilized to create fluidic controllers for soft robots, embodying fluidic logic, sequential actuation, and self-oscillators. However, the nonlinear response is predetermined by the design, resulting in an equivalent pre-programmed control scheme. In this work, we demonstrate how the introduction of an additional degree of actuation in snapping soft shells allows for the control of snapping pressure points and, thus, provides a means of online re-programmability of the nonlinear response. The additional degree of actuation consists of an electromagnetic force exerted by a PCB coil, on a permanent magnet embedded in the buckled shell. The PCB coil is placed in the inextensible base of the actuator.

Dynamic hand splints are rehabilitation orthoses equipped with elastic bands, which exert a passive resistance to voluntary movements of fingers. In order to make the exercise dynamically adjustable, it would be beneficial to replace the elastic bands with soft actuators, so as to make the load electrically controllable. Such actuators should be able to produce large displacements at moderate forces, with a compact size, low specific weight and electrically safe operation. Moreover, the possibility of combing self-sensing properties would be beneficial to reduce the complexity of the system, for control purposes. Here, we present a dynamic hand splint equipped with a self-sensing pneumatic soft actuator, serving as an 'inverse artificial muscle', as, upon pressurisation, it elongates instead of contracting. The actuator was made of an elastomeric tube surrounded by a plastic coil, which constrained radial expansions. The self-sensing ability was obtained with a piezoresistive stretch sensor shaped as a conductive elastomeric body along the tube's central axis. The self-sensing pneumatic actuator was mounted onto a forearm brace and was connected, on one side, to the finger (via a tendon), and, on the other side, to an on-board load-cell. The latter was used to measure the force produced by the actuator as it was stretched when the finger was bent. The presentation will describe the design, fabrication and characterisation of the system.

Ionogels are organic materials consisting of ionic liquids (ILs) immobilized in a polymer network. Being conductive, flexible and even stretchable, ionogels have attracted attention in the field of flexible ionotronics such as ionic strain sensor, ionic cable... For such applications, ionogels are subjected to repeated deformations and susceptible to damage. Healability is thus required to improve their durability, sustainability and life-span. Here, we propose the introduction of dynamic exchangeble bonds to these materials to enable their healability via vitrimer chemistry such as dynamic beta-hydroxyester (beta-HE) linkages. Vitrimer ionogels were obtained by the step-growth polymerization in IL between and diacide oligomer, diglycidylether oligomer using an triglycidylether as crosslinker via carboxylic acid-epoxy addition. The resulting ionogels are soft, stretchable, conductive and exhibits sensing ability with a great correlation between strain and resistance variation at high sensitivity, and low hysteresis. The healed ionogel exhibits full recovery of their functional properties thanks to rearrangement of beta-HE linkages. Besides, by combining with a vitrimer elastomer containing beta-HE crosslinks, a trilayer ionogel/elastomer/ionogel can be fabricated. Thank to beta-HE functions on the both materials, large adhesion between the ionogel and elastomer has been observed. The trilayer can function as a stretchable iononic cable even after healing.

Multi-sensory human-machine interfaces are currently challenged by the lack of effective, comfortable and affordable actuation technologies for wearable tactile displays of softness in virtual-reality environments. They should provide fingertips with tactile feedback mimicking the tactual feeling perceived while touching soft objects, for applications like virtual reality-based training, tele-rehabilitation, tele-manipulation, tele-presence, etc. Displaying a virtual softness on a fingertip requires the application of quasi-static (non-vibratory) forces via a deformable surface, to control both the contact area and the indentation depth of the skin. The state of the art does not offer wearable devices that can combine simple structure, low weight, low size and electrically safe operation. As a result, wearable displays of softness are still missing for real-life uses. This presentation shows ongoing developments of a technology consisting of fingertip-mounted small deformable chambers, which weight about 3 g and are pneumatically driven by a compact and cost-effective unit. The technology has been used to conduct psychophysical tests with virtual-reality environments, aimed at elucidating how the tactile sensitivity to softness in virtual reality can vary depending on the interplay between visual expectation and tactile feedback.

Work loop testing is a commonly used test for biological muscles however, it is rarely applied to artificial muscles. This paper shows that work loop testing provides useful information beyond the standard isotonic and isometric tests that are commonly used to evaluate the performance of an artificial muscle. A dielectrophoretic liquid zipping actuator (DLZ) was subjected to both work loop testing and conventional isotonic and isometric tests, the results from these different tests were then compared. It was found that the power calculated through work loop testing is smaller than that found from isotonic testing. Work loop testing better simulates the conditions an artificial muscle would be subjected to in an application, thus giving a better approximation of the sustained power that would be available in such a real-world application.