This PDF file contains the front matter associated with SPIE Proceedings Volume 11375, including the Title Page, Copyright information, and Table of Contents.

The acronym, EAP (Electroactive polymers), and the synonymous term, artificial muscles, are now well recognized among scientists and engineers worldwide. Prior to 1999, development of such materials has been done at few research institutes in the US, Japan, Italy and Australia and had with minimal visibility and limited cooperation. The EAPAD Conference has been the first major international forum of communicating the development in the field of EAP. At the opening of the first Conf. that was held in 1999, the author posed an arm-wrestling challenge in an effort to promote worldwide advances towards the realization of the potentials of these materials. In posing the challenge, he sought to see EAP activated robotic arms win against human in wrestling match and thus provide a gauge to the technology state. In the contests that were held in 2005 and 2006, the arms lost against the high school female student who wrestled with them - their measured speed and force were about two orders of magnitude lower that the student. Even though no other contest was held since then, the progress in the field indicates that winning the challenge is becoming increasingly more likely. The improvements have led to many applications and many of them were presented at the annual EAPAD conferences and demonstrated at their EAP-in-Action Session. The applications included soft robots, steering mechanisms, brail displays, miniature grippers, loudspeakers, active diaphragm and pumps, toys as well as many others. This manuscript provides a brief review of the advances that were reported since the first EAPAD Conference, including the state of the art, challenges and the expectations for the field.

As natural and man-made disasters occur, from earthquakes, tornados, and hurricanes to chemical spills and nuclear meltdowns, there is a need for field robotic systems that are able to respond in these hazardous and dangerous environments. This talk will start with presenting a novel hybrid mechanism robot whereby the locomotion and manipulation platforms are designed as one entity to support both locomotion and manipulation symbiotically. Experimental results demonstrate the robot’s unique capabilities, such as traversing challenging obstacles and manipulating various payloads. This talk will then present the extension of this research to new designs of self-reconfigurable and modular field mobile robots that can autonomously and actively bond multiple robotic agents to provide scalable mobility and manipulation configurations. Recent progress on the design and integration of semi-autonomous victim extraction robots will also be presented. The talk will also describe recent results on the design and control of bio-inspired robotic tails capable of stabilizing and maneuvering legged robots. Finally, the talk will describe research on robotic exoskeletons for applications including gesture-based mobile robot tele-operation and upper-extremity hand rehabilitation with autonomous grasping.

Ras Labs makes Synthetic Muscle™, which is a class of electroactive polymer (EAP) based materials and actuators that controllably contract and expand at low voltage (1.5 V to 50 V, including use of batteries), potentially sense pressure (gentle touch to high impact), and attenuate force. This offers biomimetic movement by contracting similar to human muscles, but also exceeds natural biological capabilities by expanding under reversed electric polarity. These EAPs are affordable and robust. They have been tested in many harsh environments, including extreme temperatures, high pressure underwater environments, and in space on the International Space Station. Potential load bearing applications are feasible, with significant mechanical strength when tested in compression. Selected EAP samples were tested and survived 3,000,000 cycles at 4 Hz from 5 psi to 30 psi, followed by a 50-psi compression. Human grasp is gentle yet firm, with tactile touch feedback. In conjunction with shape-morphing abilities, these EAPs also are being explored to intrinsically sense pressure due to the correlation between mechanical force applied to the EAP and its electronic signature. We are continuing to advance EAP technology and apply this technology towards robotic grippers. The robotic field is experiencing phenomenal growth in this fourth phase of the industrial revolution, the robotics era. The combination of Ras Labs’ EAP shapemorphing and sensing features promises the potential for robotic grippers with human hand-like control and tactile sensing. This work is expected to advance both robotics and prosthetics, particularly for collaborative robotics to allow humans and robots to intuitively work safely and effectively together.

A Mars airplane has been in development. This airplane requires lightweight and powerful actuators to fly in the rare Martian atmosphere. A dielectric elastomer actuator (DEA) is a possible candidate for the actuator controlling the airplane since it has high power, and high efficiency. A structural model of a wing having a control surface, a DEA, and a linkage was built and a wind tunnel test of a control surface actuation using a DE actuator was carried out. It is feasible to use the DEA for controlling the Mars airplane under wind speeds of 65m/s in the Martian atmosphere.

Soft robots with many degrees of freedom, modelled after snakes or tentacles, can locomote through a combination of controlled friction and phased multi-segment deformation. Using different periodic motions (gaits) snakes (and snake-like robots) are able to cross open space, climb narrow passages, side-wind across granular substrates, and more. Unlike their biological counterparts, snake-like robots should be able to adapt easily to space flight by utilising controllable friction elements in the form of electro-adhesive pads to selectively attach to and detach from surfaces and objects. They could operate on the interior and exterior of satellites to perform maintenance and repair, or even explore the surfaces of small astronomical bodies which do not produce enough gravity to allow for traditional wheeled rovers. Dielectric elastomer actuators (DEAs) are an ideal candidate for the driving system of such a robot, and have already demonstrated the ability to form multi-degree of freedom actuators of varying design. They are lightweight, use minimal current to maintain a given position, have high energy density, and are capable of self-sensing their strain, reducing the need for external monitoring. We present here the design and analysis of a lightweight DEA snake-like robot incorporating electro-adhesive elements for operating in zero-gravity environments, including different gait waveforms for enhanced performance and finite element analysis for design optimisation. We conclude with discussion of future improvements, such as the incorporation of dielectric elastomer switches for greater autonomy.

This study proposes the development of a locomotion robot using a deformable dielectric elastomer for actuation without pre-stretch. Electroactive polymers (EAPs) that are driven by electrical stimulation have recently garnered attention. Among EAPs, dielectric elastomer actuators (DEAs) are focused herein. DEAs have a structure wherein a dielectric is sandwiched between elastic electrodes. The performance of the DEA depends on the relative permittivity, Young's modulus, and the applicable voltage of the dielectric material. DEAs are usually used with pre-stretching, because of the material properties of the dielectric, which requires a large stress in the initial stage of extension, and the increase in the displacement of DEAs with the application of pre-stretch. However, because rigid frames are generally used for prestretching, there are few DEA applications that utilize their flexibility. Therefore, we focused on slide-ring materials (SRMs) as new dielectric materials. SRMs are polymer materials in which the cross-linking points move freely, and having excellent properties as dielectrics for DEA applications. Thus, pre-stretching is not required, and applications utilizing the flexibility of DEAs is possible. In previous research, a bending unit that did not require pre-stretching was manufactured by attaching non-stretchable tape to one side of the DEA using an SRM as the dielectric material. In addition, a locomotion robot with a bending unit was developed, and it was confirmed that the robot achieved locomotion because of a phase difference between the units. However, the basic characteristics of the bending unit and locomotion robot were not discussed. Therefore, in this research, we measured the frequency characteristics of the bending unit alone and demonstrated the locomotion of the robot.

Soft robots have a great potential for realizing human-friendly robots with adaptability and gentleness. An actuator is a crucial element for realizing them; various types of soft actuators have been developed, such as pneumatic actuators and polymer actuators. We have focused on ionic polymer metal composites (IPMC), and applied them to soft robots. In this paper, new design and fabrication processes are presented with several examples of soft actuators/robots developed in our lab. Two topics are shown in this paper. The first one is a hose-free pneumatic actuator driven by gas/liquid chemical reaction through the IPMC membrane. The pneumatic or gas-driven actuators are one of the most promising actuators in soft robotics. However, they need airsupply hoses, valves, and gas sources, which makes their work as mobile or portable actuators difficult. We have applied the IPMC membrane to control water electrolysis/synthesis, where IPMC works as an ion-exchange membrane. It controls the gas pressure and drives air-driven actuators without a hose. Two examples are shown in this paper— electrically driven thin McKibben muscles and tether-less pneumatic robots. The second topic is on IPMC actuators/robots with various 3D shapes. Most of the previous robots driven by IPMC actuators have been made by cutting and assembling the IPMC sheets, or they are very simple robots for the demonstration of IPMC actuators. Two design and fabrication processes developed in our lab to realize soft robots with arbitrary 3D structures are discussed in this paper, which are multi-layer casting and paper/fabric assisted IPMC actuators or PF-IPMC process.

Using only 0.96g of dielectric elastomer actuator and applying about 3kV we will be demonstrated can lift a weight of 4kg over 1mm. It is driven at relatively high speed and the time required to move 1 mm can be 98 milliseconds. The DEA achieves high output using SWCNT electrodes suitable for acrylic dielectric elastomers. Currently, we are developing a new dielectric elastomer material and SWCNT. With such, we seek to make the actuator more compact and obtain higher output power. Within a year’s time, we are aiming for a DEA that lifts 8kg.

A CNT spray can impart conductivity to various materials through simple application alone, not requiring any special equipment or techniques. The sprayed CNTs are flexible after drying and remain conductive and connected even when bent or stretched. In addition, because of its excellent adhesiveness, it does not easily peel off or scatter after drying. It is very easy to use, able to be applied with a special CNT paint spray. Expensive dispersing equipment and special coating equipment are not required, doing away with troublesome dispersion work. With a CNT sprayer and dielectric elastomer, it is possible to make a DE easily, which can further promote DE research and trial production. It is possible to change the content of CNTs according to the purpose. By simply applying CNT spray, the following can be easily achieved: DE electrodes, wiring of electronic circuits that require flexibility, mounting of electronic components on flexible PCBs, and rubber that requires flexibility. It is also possible to easily add conductivity to a sponge.

The Ras Labs’ Synthetic MuscleTM is made of an EAP material that can be actuated controllably to contract and expand under low voltage (< 50 V). It can be used to sense pressure from gentle touch to high impact. The latest capabilities of this EAP material will be demonstrated.

For everyday cycling, one needs to carry rainproof clothing just for the case of unexpected downpours. In the present research, we present a concept for a helmet which is automatically rainproof when the rain starts. When the sun comes out, the helmet is breathable again even before it completely dries up. This functionality is provided by active hydrogel meshes. Hydrogel meshes offer great advantages due to their ability to change the aperture size with swelling and deswelling. In our current work, we present the design and modeling steps for hydrogel-layered active meshes which use (i) swelling and deswelling in hydrated state and (ii) swelling starting from the dry state. The main goal is to close the air openings of a bicycle helmet when rain starts as an automatic rainproofing. This can be achieved through the swelling of the hydrogel pNiPAAM-co-chlorophyllin in the meshes, which leads to closing when hydrated. At the same time, the light-sensitive behavior leads to opening of the apertures under direct sun exposure, i.e. when the sun appears again after the rain. We present the steps of modeling and design using the Normalized Extended Temperature-Expansion-Model (NETEM) to perform simulations in Abaqus. The model is capable of describing both the swelling of the hydrogel under light stimulus and the volume change due to hydration. It is based on the analogy between free swelling and thermal expansion and defined for nonlinear displacements. We also discuss the fabrication process of hydrogel-layered fibers and challenges in their application and simulation. As a proof of concept for hydrogel-layered meshes, we show preliminary experimental results of a poly(acrylamide)/poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAAm/PAMPS) hydrogel with semi-interpenetrated network (SIPN) structure and its swelling capacities on a mesh. Starting from the active hydrogel meshes as presented in the current work, the next step can be smart textiles that harness the power of hydrogels: the adaptation to combinations of stimuli – like humidity, temperature and brightness - that define environments.

This talk will discuss recent progress in utilizing liquid metals as conductors for stretchable, soft, and reconfigurable components for electroactive polymeric devices. Alloys of gallium are noted for their low viscosity, low toxicity, and near-zero vapor pressure. Despite the large surface tension of the metal, it can be patterned into non-spherical 2D and 3D shapes due to the presence of an ultra-thin oxide skin that forms on its surface. Because it is a liquid, the metal is extremely soft and flows in response to stress to retain electrical continuity under extreme deformation. By embedding the metal into elastomeric or gel substrates, it is possible to form soft, flexible, and conformal electrical components, stretchable antennas, and ultra-stretchable wires that maintain metallic conductivity up to ~800% strain. Thus, these materials are well-suited for soft robotics, stretchable electronics, and actuators because they can maintain metallic properties during deformation. In addition to introducing the advantages of these materials for such applications (e.g. conductive and self-healing electrodes in electroactive polymers), this talk will focus on recent work to utilize liquid metal for (2) tough energy absorbing materials1, stretchable embedded sensors and antennas[2], and soft materials logic3. This latter work is exciting because it suggests a way for materials to perform logic without the need of a centralized processor. Here, the deformation of a material (by touch or actuation) can be used as a logic input, which in turn ‘calculates’ a response. These advances have implications for soft machines and robots that have ultra-soft mechanical properties. References 1. Cooper, C. B. et al. Toughening stretchable fibers via serial fracturing of a metallic core. Sci. Adv. 5, eaat4600 (2019). 2. Dickey, M. D. Stretchable and Soft Electronics using Liquid Metals. Adv. Mater. 29, 1606425 (2017). 3. Jin, Y. et al. Materials Tactile Logic via Innervated Soft Thermochromic Elastomers. Nat. Commun. 10, 4187 (2019).

Electrical permittivity has a central role in the performance of a wide range of dielectric elastomer technologies, from electrostatically-controlled actuators to capacitive sensors and energy harvesting transducers. One approach to improving the permittivity of elastomers is to create an “artificial dielectric” by adding metal filler. However, the addition of rigid filler can reduce the mechanical compliance and elasticity of the host elastomer and result in decreased electromechanical coupling. To avoid this trade-off, I introduce an alternative approach in which the rigid filler is replaced with a dispersion of droplets of liquid-phase metal alloy. Using eutectic gallium-indium (EGaIn) as the liquid metal, I show that it is possible to engineer artificial dielectrics that preserve the mechanical properties of the host elastomer. Moreover, significant degradation of the elastomer’s electrical breakdown strength can be avoided through control of the droplet size and polydispersity. After a discussion of the underlying principles for permittivity enhancement, I present approaches to theoretical methoding based on effective medium approximations and homogenization theories that are in reasonable agreement with the experimental measurements. To demonstrate the practical use of these EGaIn-elastomer composites in dielectric applications, I briefly review three use cases. The first is a capacitive sensor with EGaIn electrodes that measures stretch as a function of change in capacitance. The second is a flexural dielectric elastomer actuator that shows a 80% improvement in blocking force compared to elastomers without EGaIn filler. In the third example, I present a dielectric energy harvesting system that generates significantly more electrostatic energy when EGaIn filler is added to the dielectric.

Dielectric elastomer (DE) sensors have great potential for applications in soft robotics, wearable devices and medical diagnostic. A novel pressure sensor with remarkably improved force sensing characteristics was obtained through combined usage of polydimethylsiloxane (PDMS) and ionic liquid (IL). The regenerated keratin from wool was added and dispersed homogeneously in the PDMS matrix acting as reinforcing fillers. The influence of the amount of IL on the electro-mechanical properties of the composites was investigated. One obvious result was that the permittivity of the ILcontaining elastomers increased dramatically with the increased amount of IL loaded. Furthermore, the sensitivity of the composite elastomers as pressure sensors was investigated by recording the response of the voltage when a small force is applied to the top surface of the pressure sensor. The elastomers with IL loaded exhibit excellent response of the voltage and the maximum sensitivity of the composite elastomer is 2.64 mV/N.

Different capacitive and resistive elastomer sensors for the measurement of the filling level of water in a vertical plastic tube are introduced in the paper. The filling level sensors consist of elastomer membranes carrying electrically conductive layers with special geometrical designs. Three different basic sensor principles in various versions were investigated. First, capacitive strain sensors with different electrode designs detect the pressure of the water column above the elastomer membrane by measuring the change of electrical capacitance due to the stretch deformation. The shape of the electrode layers on these sensors affects their measuring sensitivity. Second, resistive strain sensors are also stretched by the water pressure acting on the membrane, but here the stretch changes the electrical resistance of the sensor. The resistor on the membrane is a silicone layer with conductive particles, which consist of carbon black or alternatively of silver-coated copper flakes. Depending on the kind and the concentration of the particles, the resistance of the sensor and its variation upon stretch can be tuned. Third, capacitive proximity sensors detect the height of the water level by measuring the capacitance between two neighbored electrode layers on the membrane. In this configuration, the sensor is a long elastomer film along the length of the plastic tube. The advantages and disadvantages of the different sensor principles are discussed. This discussion includes the sensor characteristics in terms of the change of capacitance or resistance vs. water level in the tube and also the creep behavior of the different filling level sensor types at constant water filling level.

Fluids functions range from thermal management in buildings to blood circulation in animals. To date the use of fluids in soft and wearable robots has been limited by the need for hard and noisy external pumps. Here we report soft pumps, a class of electrically-driven pumps with an entirely flexible or even stretchable body. These pumps rely on ElectroHydroDynamics, a solid-state mechanism that accelerates liquid molecules using electric fields, resulting in silent bi-directional operation. These elastomer pumps can be integrated into untethered soft robots, soft exoskeletons driven by fluidic muscles, and smart textiles with active temperature management.

Hydraulically amplified self-healing electrostatic (HASEL) actuators provide a framework to create soft robots with excellent strength, speed, and versatility. Peano-HASEL actuators produce fast and powerful linear contraction and achieve a maximum strain of ~15%. However, skeletal muscle achieves ~20% strain on average. Here, high strain Peano-HASELs (HS-Peano-HASELs) are introduced that achieve linear contraction up to ~ 24%. We investigate a wide range of performance metrics for HS-Peano-HASELs constructed with different materials and geometries. Furthermore, HS-Peano-HASELs are used as a tubular pump, resembling the primordial heart of an ascidian. Additionally, a strain amplifying pulley system is introduced to increase the maximum strain to ~42%.

We present a very thin, fast and flexible fluidic valve based on a hydraulically amplified dielectric actuator. A thin cavity made by bonding flexible membranes and including central stretchable region made of silicone is filled with dielectric fluid. Under an electric field, the fluid is displaced from the edges of the cavity to the central region, inflating the center of the actuator and closing a valve. The valve dimensions are less than 10x10x1mm. The valve can block a pressure up to 1Bar in less than 10ms for a 1 mm diameter inlet using a voltage of 1.4kV. Arrays of such valves are easily fabricated with inexpensive materials.

We studied the detailed electrochemical and electromechanical properties of a polyvinyl chloride (PVC) gel with dibutyladipate (DBA) as a plasticizer and developed an electromechanical model based on the electrochemical data. We evaluated the electric deformation of the PVC gel by the bending displacement response of the PVC gel strip when a square-wave voltage is applied. We studied the electrochemical impedance measurements of the PVC gel under bias voltages. Based on the above electromechanical and electrochemical experimental results, we developed a deformation model of the PVC gel where the electric bending response is basically due to the electrochemical formation of the plasticizer-rich layer and its deformation from the Maxwell stress. Then, in order to enhance the actuation performance of polyvinyl chloride (PVC) gel actuators, we prepared PVC gel film with ionic liquid (IL) additives and studied the generated strain of PVC gel actuators with four types of ILs. We found that the actuator response of the PVC gels with 0.01 wt% ILs is almost two times larger than those without ILs at low applied voltages of 200 V to 600 V. We studied the electrochemical properties of the PVC gels with ILs and proposed an electromechanical model previously. On the basis of the proposed electromechanical model, the effect of IL additives on enhancing the actuation performance can be clearly described.

Electroactive polymers (EAPs) are smart materials capable not only to change their shape and/or size in response to electrical stimulation, but also to generate electrical signal in response to mechanical stimulation. Flexible and lightweight, these materials are considered as promising candidates for the development of soft artificial muscles and soft Micro-Electro-Mechanical Systems (MEMS) to move towards soft electronics. This talk aims first at presenting the fabrication, integration and characterization of air-operating soft microactuators and microsensors based on electronically conductive polymers (ECPs) to obtain efficient devices for further integration into microsystems. Layer stacking method has been reported as efficient process for fabricating ECP based microactuators. In this work, electrodes based on poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) have been employed. By using polar reactive additive based on poly(ethylene oxide) (PEO), electrodes with improved electrical, mechanical and electrochemical properties have been obtained and used to fabricate efficient trilayer microactuators according to a simple and reproducible process. In addition, a process fully compatible with microsystems has been developped. The complete elaboration of the trilayer microdevices will be described including their full integration with electrical connections and subsequent operation on a flexible substrate without any manual handling, allowing the design of microsystems with complex configurations. The resulting microsystems were successfully characterized as microactuators and for the first time as mechanical strain microsensors. Finally, by combining PEDOT:PSS based electrodes with different electrochemical or mechanical properties, we demonstrate that it is possible to develop air-operating linear actuators in a rational approach according to a theoretical model. Best combination of electrodes was used to develop asymmetrical trilayer devices with simple layer stacking process. The resulting devices presented linear actuation with performances in the range of predicted values. Linear strain sensing ability of these devices was also demonstrated.

This talk focuses on recent progress in representative applications of ferroelectric and relaxor ferroelectric polymers in flexible electronics. First, a brief introduction will be given on Poly(vinylidene fluoride) (PVDF) based polymers whose are among electroactive polymers that attract a substantial amount of attention for modern flexible electronics. Then, fabrication technologies of PDVF-based polymer thin film as well as several applications of the ferroelectric copolymer P(VDF-TrFE) including piezoelectric sensors will be highlighted. Finally, research aspects involving the use of relaxor ferroelectric P(DVF-TrFE-CTFE) for high k gate dielectric material and actuators will be presented.

Dielectric elastomers (DE) are thin polymer films which are coated with compliant and conductive electrodes on each side. By stacking several layers, multilayer transducers can be realized, which maximize force or absolute deformation caused by the influence of an electrical field. Due to uncertainties in manufacturing processes and material parameters, deviations in the intended design parameters naturally occur. This paper deals with impacts on the actuation characteristics caused by uncertainties when manufacturing multilayer transducers. First, by formulating an appropriate mathematical model for a proposed DE multilayer transducer design and defining relevant design parameters, the effect of deficient electrodes is pointed out. Moreover, the model is used to derive analytic expressions to describe deviations from nominal actuation force and stretch caused by the mentioned uncertainties. Utilizing exemplary design parameters, results of the analytical approach are compared with numerical experiments using the Monte-Carlo-Method. Finally, the obtained results are discussed and conclusions about the impact of uncertainties and relevant influencing parameters are pointed out.

For silicone elastomers used as actuators, softness is key for enabling actuation at low voltages. Recently, an extremely soft (Young’s modulus < 50 kPa) silicone elastomer without cross-links has been reported by Goff et al. Besides its extreme softness, the elastomer was reported to almost completely recover (82%) from a 10-cycle elongation of more than 5000%. This observation challenges conventional elasticity theory of cross-linked elastomers because a network without covalent crosslinks should not be able to strain-recover to such extent. In this work, the elastomer is hypothesized to be formed from concatenated rings through heterodifunctional uni-molecular ring closure. It is found that the elastic properties of this uncross-linked elastomer can be described by the dynamics of concatenated rings, which act as pseudo-crosslinks and pseudo-entanglements. Isolated rings and dangling rings function as external solvents and internal solvents respectively, thereby contributing to the unprecedented softness. The ability to precisely control the ratio between concatenated and dangling rings is expected to lead to even softer dielectric elastomers paving the way forward for ultra-soft robotics without significant mechanical losses.

Slide-ring elastomers have mobile cross-links that can slide on their axial polymers in a manner similar to a pulley on a zip line. This supramolecular network structure imparts unique mechanical properties to the elastomers, such as high deformability and low hysteresis upon cyclic loading, that are often favorable for dielectric elastomer actuators (DEAs). The utilization of this type of dynamic network for actuation has been limited by the low compatibility of slide-ring materials and common elastomer platforms used in DEAs. Here, a synthetic pathway is proposed to allow for incorporation of slide-ring cross-linkers into silicone networks.

Limitations of conventional actuators and sensors in small-scaled and complex devices have diverted the researches’ attentions towards smart material transducers such as ionic polymer-metal composites (IPMCs). In addition to actuation capabilities, IPMCs generate voltage when subjected to mechanical deformation. Utilization of IPMCs as sensors has been studied much less than IPMC actuation, and direct comparison of sensing methods is required for efficient implementation. This paper characterizes IPMC active sensing methods i.e. voltage, current, and charge in terms of frequency responses, coherence, noise, and repeatability. IPMC is excited mechanically between 0.08 Hz and 60 Hz under identical experimental conditions, while signal and displacement are measured. The results provide an absolute comparison for IPMC active sensing dynamic methods, for a typical IPMC (Nafion, Pt, Na⁺).

Ionic polymer metal composites (IPMCs) are a class of soft electroactive polymers. IPMCs comprise a soft ionic polymer core, on which two stiff metal electrodes are plated. These active materials exhibit large bend- ing upon the application of a small driving voltage across their electrodes, in air or in aqueous environments. In a recent work, we presented compelling theoretical and numerical evidence suggesting that ionic polymer membranes exhibit complex multiaxial deformations neglected by reduced-order structural models. Where most beam theories (including Euler-Bernoulli, Timoshenko, and most higher-order shear deformation models) would suggest vanishing through-the-thickness deformation, we discover the onset of localized deformation that rever- berates into axial stretching. Building upon this effort, here we investigate the role of the electrodes and shear on multiaxial deformations of IPMCs. We establish a novel structural theory for IPMCs, based on the Euler- Bernoulli kinematics enriched with the through-the-thickness deformation in the ionic polymer, computed from a Saint-Venant-like problem for uniform bending. While considering boundary conditions that elicit non-uniform bending, we compare the results of this model against classical Euler-Bernoulli beam theory without enrichment and finite element simulations, encapsulating the nonlinear response of the material. We demonstrate that our theory can predict the macroscopic displacement of the IPMC, along with the localized deformation in the ionic polymer at the interface with the electrodes, which are not captured by the classical Euler-Bernoulli beam theory. This work paves the way to the development of more sophisticated structural theories for IPMCs and analogous active materials, affording an accurate description of deformations at a limited computational cost.

Dielectric Elastomers (DE) can be excellent transducers for actuators, sensors and generators. Therefore, a lot of research on DE applications has been done. Actuators, sensors and generators for small devices will be coming to the market very soon. However, much of the market demand is for heavier applications such as DE power suits, DE motors, DE muscles for robots, and larger DE power systems. In order to meet such requirements, attempts have recently been made to use new carbon foam materials such as SWCNTs or MWCNTs as electrodes for DEs. As a result, using SWCNT electrodes, a DE actuator with only 0.96 g of DE material can easily lift a 41N weight. Furthermore, a transparent diaphragm actuator can be manufactured by using super purified SWCNTs. This paper shows that the performance of DE varies significantly depending on the type of electrode materials used. When carbon black, MWCNT and SWCNT were used as electrode materials for DE, we investigated how much weight could be lifted in each case. Assuming that the carbon black is 1, it is possible to lift a weight of about 2.2 times for SWCNTs. In addition, the difference in elongation due to the difference in electrode material is 1.7 to 2.2 times that of SWCNTs, although it depends on the frequency used. It has been also found that the use of higher crystalline SWCNTs and metal CNTs is more effective. Moreover, this paper discusses the application of DEs using CNT electrodes and the risk management when using CNTs.

In this contribution, an analytical modeling approach to describe the influence of electrodes on the actuation behaviour of DE-transducers is presented and validated by corresponding FE-simulations. As the impact of electrodes has almost been neglected in previous work, our theoretical approach considers the electrode’s dimensions and stiffness with respect to quantities of the elastomeric poly- mer film covered by the electrodes. The analytical modeling is based on energy considerations utilizing hyperelastic models for both, the polymer film and the compliant electrodes and by bal- ancing forces in each direction. The corresponding FE-analysis performed in COMSOL multiphysics validate the analytically obtained results. It turned out that area, thickness and stiffness of the electrodes regarding to the polymer’s quantities have a strong impact of the actuation behaviour of DE-transducers. Obtained results are reflected by published measurements validating our findings.

This work presents how the lifetime of silicone-based dielectric elastomer actuators (DEAs) is affected by the choice of silicone elastomer material, humidity and temperature at constant DC electric fields and membrane prestretch. High (>50%RH) humidity levels are found to significantly decrease the lifetime of silicone-based DEAs under DC actuation, whereas temperature and the type of silicone elastomer have a more limited impact. Under a constant DC electric field of 83V/μm and a membrane prestretch of 1.3, all DEAs operating at 80°C – 90%RH fail within 24 hours whereas DEAs actuated at 20°C – 10%RH all survive over 14 days without any failure.

An important part of the communication between a device and its environment occurs via their interface. Currently, the surface of many devices is still static and cannot be programmed to communicate dynamically with its surroundings. By bringing these static surfaces into motion, devices can potentially provide haptic feedback, switch between specular and diffuse reflection, or actively transport material at the device surface. Recently, we introduced a new design to create oscillating surface waves into an initially flat surface using a continuous AC electric field. In this paper we present new insights in the parameters that influence the surface dynamics, focusing on how circuit and electrode pattern design can be optimized to obtain naturally favorable dynamic surface topographies with programmable shapes.

Novel insights into the electromechanical failure of dielectric elastomers are presented. Measurements are conducted by coupling a high-speed camera to electrical breakdown strength equipment. It is shown that the breakdown behavior is far from simple since the thin elastomer film undergoes complex dimensional changes before the breakdown. Multiple geometries of the electrodes were investigated and different behaviors were observed. The breakdown patterns were categorized and the underlying theory behind this complex process will be presented.

Fishing-line artificial muscles can exhibit various motions. Twisted Polymer Fiber (TPF) actuators, which are a class of fishing-line artificial muscle actuators, generate torsional motion by applying heat. In general, untwisted fiber contracts by heating. However, measuring the blocking thermal tensile force of a TPF, we have discovered that the tensile force decreased and fluctuated depending on the initial number of twists in the TPF. This suggests that a TPF expands depending on the initial number of twists. Furthermore, the tensile force does not decrease monotonically but fluctuates during heating.

Supercoiled polymer (SCP) actuators belong to a recently discovered class of artificial muscles that show strong promise in various robotic applications. Extensive studies have been conducted on various aspects of SCP actuators, including the characterization of their hysteresis nonlinearity and dynamical behaviors. However, the existing strategies cannot effectively capture the first cycle of SCP actuators, which, under the application of certain sequences of inputs, gives rise to a “lonely stroke”. For example, under the application of continuous voltage oscillation sequences, the first output cycle is different from the successive repeatable cycles. This lonely stroke behavior in SCP actuators needs to be better analyzed since no comprehensive experimental investigations have been conducted. Furthermore, the lonely stroke affects SCP actuator’s performances in repeatable cycles. In this study, we conduct experimental investigations on SCP actuator’s lonely stroke under different loading and temperature conditions. The experimental procedures and measurements are presented and discussed. The results show that the coupling between lonely stroke and hysteresis is complex and history-dependent. For example, the maximum output strain discrepancy due to the lonely stroke was found to be 3.5% for an SCP actuator with a maximum strain of 15%.

High-performance artificial muscle is of great interest to robotics community. In this study, we investigate the influence of pre-stress on fishing line artificial muscle's tensile stroke. Fishing line artificial muscles with electrothermal actuation were made from nylon 6 mono-filament and resistance wires. The tensile stroke in time domain was found to exhibit different actuation behavior under different levels of pre-stress in spring-load test. The supplied current was kept constant through all the experimental tests to investigate the effect of prestress on the artificial muscle performance. The presented study provided new insight into implementation of fishing line artificial muscle towards robotic applications, especially regarding how to choose appropriate pre-stress for muscle integration.

Dielectric Elastomers (DEs) are deformable dielectrics that can be used as active materials in mechatronic transducers, such as actuators, sensors and generators. Focusing on actuation systems, several kinds of DE actuators have been proposed in the literature, being characterized by various shapes/sizes and disparate performances in terms of efficiency, force/power densities and reliability. In any case, up to date, these devices are mostly based on either silicone or acrylic elastomers. On the other hand, actuator prototypes, which exploit the electromechanical properties of styrenic rubber, have been scarcely considered. Therefore, in this paper, a styrene-based-rubber Lozenge-Shaped DE Actuator (LS-DEA) is proposed and its performance are empirically evaluated. In particular, after material characterization and on the basis of a design procedure previously proposed by the authors, it is practically shown how it is possible to optimize the LS-DEA elastic response in order to tailor the application requirements and also (if needed) to obtain a nearly-zero mechanical stiffness. Several experimental results are henceforth provided, as a basis to highlight advantages and disadvantages of styrenic rubber LS-DEA over similar acrylic or silicone-based devices

The behaviour of Dielectric Elastomer Actuators (DEA) can be predicted using hyperelastic models that are based on strain energy density functions. The parameters used in the hyperelastic models are generally obtained via a uni-axial pull test. However, DEAs are most commonly used in an biaxially stretched configuration. This is an appropriate assumption if the modelled parameters translate accurately to different stretch configurations. We have conducted stress-stretch experiments on silicone membranes in two different configurations; uni-axial and pure shear stretch. Fitting common hyperelastic models, such as Gent, to the experimental data shows that the modelling parameters depend on the stretch configuration. In addition, we show that the Mullins effect, where the stress-stretch response is dependent on the maximum stretch previously experienced by the sample, is predominant in the silicone membranes. This means that the model parameters depend on the loading configuration and the stretch history of the sample making it difficult to predict the behaviour of highlyprestretched DEAs. One way to tackle this issue is to carry out testing as close to the original configuration as possible which is difficult in the case of highly prestretched DEAs. We have created a model that takes into account both the loading configuration and the Mullins effect and used this to optimize the prestretch and stretch of the cell stretching device.

We develop and validate an analytical model in order to achieve large actuation deformation and high load-bearing capacity in a multistable dielectric elastomer actuator (DEA). We integrate patterned shape memory polymers (SMPs) and stretchable heaters with a 30 mm x 30 mm DEA to locally soften different SMP regions by 250 times during the actuation, allowing multiple a wide range of actuated shapes, and latching of those shapes. The model allows optimizing SMP thicknesses and other design parameters to offer the best trade-off between the actuation and the load-bearing.

In this paper, we develop and characterise the use of amorphous Silicon as an optically functional material in actuated devices. A novel actuator is developed which uses thin amorphous silicon film deposited on a polyimide substrate using Plasma Enhanced Chemical Vapour Deposition (PECVD). The actuator generates an active stroke via electrostatic attraction which causes the electrodes to “zip” together. The magnitude of displacement is controlled by exploiting the light-dependant resistance of an amorphous silicon (a-Si) photoreceptor integrated onto the actuator. An 8mm long actuator was prototyped and curvature changes were measured using image processing techniques to track the amorphous silicon electrode during actuation. A change of radius of 1mm was found between the ambient (22 Lux) and illuminated states (36 kLux) with an applied voltage of 5 kV.

Electrothermal actuator (ETA) is an area of smart and active materials that is being heavily researched to utilize their large strain capabilities. Traditionally, these actuators are fabricated by coating a polymeric soft elastomer onto a layer of conductive fillers such as buckypaper. This paper explores various factors that can influence the actuation performance including, but not limited to, electrical conductivity, sample thickness, addition of insulation layers, and spatially varying conductance zones. While conventionally, small and thin film-like ETA structures with uniform heating distributions are used, this paper proposes scalable ETAs by fabricating larger ETAs with spatially varying conductance zones.

Having a multitude of electromechanical and robotic applications, most flexible elastomer actuators require electrically conductive electrode components as well as nonconductive substrate components to operate. Various analytical models of flexible actuators typically show that several properties of the elastomer, such as thickness, permittivity, and softness, directly influence the actuation capability. As such, the optimization of flexible actuators, particularly in dielectric elastomer actuator (DEA), has focused on improving the elastomer while electrodes are often overlooked. However, the electrodes with high modulus of elasticity, thickness, and low stretchability can reduce the amount of actuator performance. In addition, inadequate electrical conductivity increases the actuator’s power requirement and influences the viscoelastic properties of DEA materials through resistive heating. Furthermore, besides material composition of electrode, manufacturing methods also govern the actuator performances. Therefore, a thorough investigation of both electrode properties and manufacturing methods is crucial to attain high-performance DEAs. In this work, a microdispensing additive manufacturing technique was used to produce high-quality electrodes and to fabricate test coupons composed of PEDOT:PSS (conductive and transparent polymer) and Triton X-100 (surfactant plasticizer). These coupons, as well as some molded coupons, were used to investigate important mechanical, electrical, and thermal properties of DEAs. Through the testing, the electrode showed satisfactory stretchability up to 55% for a PDMS-supported sample. Although Young’s modulus of PEDOT:PSS was decreased largely by adding Triton X-100, the value was still relatively high (8.3 MPa) that needed to be lowered more to be effectively used for DEA application. The electrode maintained its conductivity above 50 S/cm when tested in the deformed state (up to 50% of strain) or at different temperatures (25-55 °C). Finally, the applicability of electrode composition was verified by electromechanical tests performed on a fully printed single layer DEA with 20 microns thick electrodes.

Dielectric elastomer (DE) transducers consist of a dielectric elastomer layer coated with flexible electrodes on both surfaces. Apart from the dielectric film, the properties of the electrodes affect the electromechanical behavior of the DEtransducers as well. Electrodes must be able to sustain conductivity at large deformations, must exhibit a low stiffness and provide sufficient adhesion to the DE-layer. Different processing technologies exist for application of electrodes suitable for DE-transducer. Among them, the inkjet printing technique gained attention in recent years as a very precise and purely non-contact deposition method to fabricate thin electrode layers. In contrast to other methods, e. g. using a shadow mask in case of spraying, the inkjet technique is very versatile and allows a fast adjustment of the processed electrode geometry. In order to describe the requirements of the inkjet printing process and ink adaptation itself, we present a theoretical description of those processes accompanied with the definition of parameters, which need to be considered during experimental processing. Furthermore, we present first results of our adaptation of an ink formulation and an inkjet printing procedure. For this purpose a commercial electrode paste, Elastosil LR 3162, made of carbon black-silicone composite, was adapted to the inkjet printing process. In first experimental studies, the adapted ink was inkjet printed onto dielectric elastomer layers by varying the inkjet printing parameters. Different measurements were performed in order to characterize separate dots as well as continuous lines and areas of the inkjet printed electrodes. The electrode thicknesses and its shapes were recorded by surface-profile measurements. The electrical properties of the printed electrodes as well as their mechanical influence on the elastic properties of the elastomer layers were measured under continuous and cyclic mechanical stretching.

The efficient manufacturing of dielectric layers and electrodes for dielectric elastomers is challenging especially for stacked configurations. In an earlier publication we describe a contactless programmable manufacturing approach for aerosol-jet-printing stacked silicone and reduced graphene oxide (rGO)-layers in one process device. One limitation of the setup presented there is the long production time of e.g. 45 minutes for a 1 cm2 electrode with a sheet resistance of 1 MΩ. This contradicts the goal of printing numerous layers for stacked systems and is related to the usage of an ultrasonic atomizer. Therefore we present a new hybrid atomizer, which significantly lowers the printing times of rGO-electrodes. This hybrid atomizer again uses an ultrasonic aerosol generation system. Hence, particle-inks without chemical stabilizers that would affect the curing process of printed adjacent silicone structures, can still be used in the system over hours without agglomeration. In addition, a pneumatic aerosol generation is integrated with the new hybrid atomizer. The combined material output of the pneumatic and the ultrasonic approach allows for the printing of rGO-electrodes in two minutes or less with characteristics comparable to those described above. Furthermore, a light-heating-system is integrated into the printing system which enables the fast evaporation of the solvents independently of the height of the previously stacked layers. For this new system, several printing strategies are evaluated by comparing different programmed trajectories of the print head. Printed rGO-electrodes with thicknesses from 3-20 μm and values for the sheet resistance from 1 MOhm to 200 kOhm are characterized regarding their ability to bear a maximal deformation up to 100 % and repeated cyclic stretching up to 25 %.

LiveMetaOptics presented the Exo-life finder (ELF) telescope combined with the hybrid dynamic structure of live and light active mirror named as “Live-mirror”. Recently we reported the idea of active optical surface correction using the advantage of an electromechanical stimulator to deform mirror surface in a significant correction scale. An effort to develop a conventional electroactive polymer (EAP) actuator through Live-mirror application has been taken the new approach, assembling EAP actuator via additive manufacturing or 3D printing technology. The approach of next-generation mirror leaned on 3D printing technological advancement is able to unlock the principles of a potentially new actuator manufacturing technique. Full 3D print of modified EAP was formulated with plasticized terpolymer for an active layer and terpolymer/CB composite for printed electrodes. Though rudimentary of electroactive polymer, the full-printed actuator could transfer its transversal stress or shear force to shape the mirror surface under low applied electric fields. We described here as well creating multilayer structures with capabilities well beyond those of the individual actuator components. Our various configurations of printed actuators could achieve glass surface deformation in a range of 50 nm to 2 µm considering the maximum glass deformation. As a result of material modification coupled with 3D printing technology, we can increase productivity while enabling a mass and cost reduction and an increase of the parts functionality in terms of the real application.

This paper describes the development of an electro-adhesive gripper with silver interdigitated electrodes that are inkjetprinted on a pre-fabricated flexible dielectric film made of polyether ether ketone (PEEK), which also acts as the gripper adhering surface, and encapsulated in a blade-casted silicone elastomer backing layer. After a description of the manufacturing approach, the paper presents and discusses the results of the electro-mechanical characterization of two fabricated nominally identical electro-adhesive devices, by specifically focusing on: electrically-induced adhesion shear stress, capacitance variation, energy and power consumption.

Dielectric Elastomer (DE) stack-transducers enable high force densities and considerable deformations since they consist almost only of active material. Based on a holistic model of the transducer system a self-sensing estimator based on an extended Kalman-filter is introduced in this contribution. By measuring the terminal voltage and current of the DE transducer the Kalman-filter estimates the deformation of the transducer, its inner states and an external load force as disturbance without superimposed excitation. In closed loop operation the deformation of the DE transducer is controlled by a sliding mode control based on the self-sensing estimation results. The self-sensing estimator and the self-sensing control are experimentally validated, finally.

Biofouling accumulation on synthetic underwater surfaces presents serious economic problem for the marine industry. When a substrate-bonded dielectric elastomer (DE) is subjected to high voltage, deformations in form of creases can be formed at the surface of the DE. This deformation, has been already demonstrated for the prevention and detachment of biofouling from the surface of DEs. In this work, we add sensing capability to the anti-biofouling effect of active DE surfaces. A device consisting of a metallic plate, a Kapton sheet, and a thin silicone membrane is immersed in conductive solution, which acts as one electrode, with the metal plate being the second electrode. Two different conductive solutions were used 3.5 wt% NaCl and 20 wt% NaCl. The surface deformation of the silicone as a function of applied voltage is monitored under microscope in order to verify electrical measurements. Breakdown measurements of the dielectric material in different conductive solutions are also performed. Because the membrane is made from incompressible elastomer and bonded to a rigid substrate, voltages below the creasing threshold create no deformation in the membrane, and therefore no change in capacitance. Above the voltage threshold, creasing instabilities appear at the surface of the silicone, thus increasing the capacitance of the device. Therefore, the capacitance of the sensor is measured as a function of applied voltage, and the voltage at which the capacitance increases is the threshold voltage at which creases occur. Creases are identified when using both 3.5 wt% NaCl and 20 wt% NaCl as top electrode. Theoretical values of creasing voltage deviate from the experimental measurements. Type of conductive solution is shown to have no significant influence on a breakdown voltage.

Pathological tremor produces undesired movements that decrease quality of life. Typical treatments such as medications and surgery have varying efficacy, risks, and side effects. Mechanical tremor suppression offers a potential alternative to these treatments: mechanical tremor suppression applies torques about joints to oppose the tremor-producing muscular torque and reduce tremor motion. Typical actuators create bulky exoskeletons that are not suitable for clinical implementations. However, dielectric elastomers enable soft, low-profile actuation that improves the potential for clinical implementation of mechanical tremor suppression. Recent research performs theoretical evaluation of dielectric elastomer-based tremor suppression, demonstrating the ability of dielectric elastomer stack actuators (DESAs) to produce very effective and robust tremor suppression via tremor-active control. A tremor-active approach only actuates to reduce tremor while the human motor system compensates for DESA passive dynamics. This approach leverages the low mechanical impedance of dielectric elastomers to compensate for their low actuation levels. This paper performs benchtop experimental testing of scaled tremor-active suppression using folded DESAs to validate previous theoretical studies. Since DESA manufacturing by folding can only achieve relatively thick layers, the DESAs do not possess the necessary actuation levels to suppress typical tremor amplitudes. Therefore, this paper evaluates a scaled system using a piezoelectric bimorph cantilever beam to represent human motion. Experiments demonstrate the effectiveness of a tremor-active impedance controller for DESA-based tremor suppression. Scaling up to DESAs with higher actuation levels will enable suppression of typical hand tremors.

Hand gesture recognition algorithms require information from the material world to be converted to digital data. In this paper we present an analysis of dielectric elastomer sensors for hand gesture recognition. A glove with five dielectric elastomer sensors has been used to collect motion data from the hand. The capacitance value of each sensor was read and analysed for a total of 24 participants. The study shows that the sensors provide enough information to differentiate gestures from each participant, although the maximum capacitance value varied with each participant, making gesture recognition over all participants difficult. Data processing allowed for this problem to be solved.

Due to recent progress in human-machine interaction towards industry 4.0 applications, the development of interfaces ensuring a safe collaboration between handling devices and workers is gaining a significant attention. For such applications, integration of wearable and highly stretchable actuator/sensor elements permits to endow the handling system with advanced and intelligent features. This paper presents on the development of a novel intelligent glove system which makes use of highly stretchable dielectric elastomer (DE) transducers as textile-integrated actuator and sensor components. The presented DE system can be used, e.g., as an adaptive assistance tool suitable for industry 4.0 environment. As a first step towards the development of the intelligent glove prototype, this paper mainly focuses on DE-based integrated force measurements. Different concepts for DE-based force measurements are presented and compared. Some of these sensing strategies are then selected, and their performance compared within the context of human-machine interaction and user interfaces.

In this paper, we demonstrate a soft, flexible and stretchable dielectric elastomer (DE) capacitive compression mat, which is able to measure pressure/force and locations (multi-touch) simultaneously. This compression mat is composed of a multi-layer soft and stretchy DE sensor. This newly designed compression mat can be intergraded into robotic grippers to measure the grasping force and identify the contact points when picking up an object. It can also be used as a clinical measurement mat to help foot exercise treatments for diabetic patients’ ulcerated feet.

Soft compression sensors represent a promising approach to provide proprioceptive feedback for robotic manipulators. However, dielectric elastomer sensors work well as stretch sensors, their sensitivity is low when used as com- pression sensors, due to the incompressibility of elastomers. Therefore, the simple electrode/membrane/electrode sensor configuration is not sensitive enough to a low range of force. Here, we report on the use of a patterned silicone layer (it is considered as pillars) to produce a compressible dielectric elastomer sensor to detect deformation and pressure. Interdigitated electrodes (IDEs) are patterned on the backside of the sensor to generate a fringing electric field into the dielectric material. The deformation of the silicone pillars causes changes in the relative permittivity due to changes in the air-volume fraction of each component. By using IDEs on the backside of the sensor, there is no need for compliant electrodes, and a simple printed circuit board (PCB) can be used. This simplifies the fabrication process and takes advantage of the good conductivity and reliability of the PCB copper electrodes. We optimized different parameters of the sensor such as the pillar’s dimension which affects the stiffness and electrical sensitivity of the sensor. Using our optimization process, we demonstrate sensors that exhibit a capacitance change of more than 36% for an input force of 60N. Our sensor combines high sensitivity with a simple fabrication and assembly, thus making it ideal for applications like the manipulation of fragile objects.

Silicone-based dielectric elastomer sensors (DESs) are highly flexible, fast responding, energy efficient, and low-cost transducers which are highly suitable for integration in existing wearable systems. This paper aims at investigating the sensor properties of a DES system shaped in a matrix configuration. For the DES matrix, an LCR-meter is used to characterize the capacitance, while a separate measurement technique is used to detect the total electrode resistance. The collected data are then compared with the measurements obtained via a commercially available integrated circuit. The electrical characteristic of the proposed DE layout is then studied, and the capability of standard integrated circuits in handling DES systems is experimentally evaluated.

While previous guest-filled carbon nanotube yarn muscles provide remarkable performance, whose actuation is driven by the volume change of a guest. They also have problems. For instance (a) carbon nanotube yarns are expensive and (b) input energy is provided to the entire muscle, but the central region of the muscle contributes little to muscle contraction. Here, we eliminated this problem by driving the muscle using a sheath, which can be on an inexpensive coiled yarn or fiber core. This configuration change dramatically increases muscle power and enables cheap commercialized yarns to replace expensive carbon nanotube yarns. For different application purposes, we coated different types of polymer or other materials to optimized the actuation performance under different trigger conditions. For instance, the electrochemical SRAM which using the CNT as the sheath and Nylon 6 yarn as the core can generate 1.98 W/g of average contractile power - 40 times that for human muscle and 9.0 times that of the highest power alternative electrochemical muscle. The electrothermal PEO-SO3@CNT SRAMs (PEO-SO3 as the sheath and CNT as the core) operated in air and in room-temperature water to produce 2.6 W/g (at 9 Hz) and 9.0 W/g (at 12 Hz) of full-cycle contractile power, respectively, compared with the 0.05 W/g typical of human muscle. Additionally, coating vapors or moisture response material on the twisted core material, we can obtain a muscle which operates torsional and tensile actuation under different vapor concentration or humidity. Because sheath-run muscles can be made so cheaply without using carbon nanotubes, and are easily upscaled, we fabricated a comfort adjusting textiles that respond to temperature, humidity and the presence or absence of perspiration by opening and closing pores(1). Reference (1) Mu, Jiuke, et al. "Sheath-run artificial muscles." Science 365.6449 (2019): 150-155.

The sense of touch, also known as tactile recognition, is crucial for modern robotics to explore and understand ambient environments. This study used a commercial inkjet printer to additively manufacture a flexible and passive tactile sensor consisting of a piezoelectric P(VDF-trFE) thin film sandwiched by a pair of electrodes. Consistent and reliable printing of piezoelectric thin films is achieved by investigating ink preparation procedures, printer settings, and substrate surface treatment. Post-processing procedures, including drying and curing, are studied to ensure thin film uniformity and functionality. Eventually, in-situ signal processing and wireless data transmission circuits are developed and validated. The printed piezoelectric tactile sensor can be potentially used for human health monitoring and soft robotics due to its high flexibility and biocompatibility.

In recent years, the field of soft robotics has received an increasing attention due to the growing needs in human-robot collaboration. Dielectric Elastomer (DE) transducers are soft and flexible substrates sandwiched between two compliant electrodes, and appear as highly suitable as actuators and sensors for soft robots. In this paper we present a control-oriented dynamic model for a novel soft robotic structure, consisting of a flexible beam actuated by two opposing DE transducers. The model accounts for both DE material behavior and elastic properties of the flexible structure, as well as interaction between the two. Actuation performance of the soft robotic structure, quantified in terms of angular deflection and beam tip displacement, is investigated by means of numerical simulations studies.

In this work we present a new concept for scalable and tightly rolled dielectric elastomer actuators (DEA). The proposed solution is motivated by the need for designing soft, high energy density, and compact actuators for soft robotics and artificial muscle applications. Each rolled DEA is made starting from a 50 μm thin silicone film (Wacker Elastosil 2030) with flexible carbon-black based electrodes screen-printed on one side. Two of those printed films are first stacked and subsequently tightly rolled, leading to the final DEA design. At first, the systematic development of the rolled DEA concept is presented. Electrical and mechanical contacts are provided by off-the-shelf wire end ferrules. The roll manufacturing process is described subsequently. Finally, an experimental evaluation of mechanical and electrical characteristics of the developed DEAs is performed. Our measurements show a change of blocking force of 0.18 N under constant load conditions and we predict a stroke of 2.5% at 2 N.

Dielectric elastomer actuators (DEAs) are usually composed of elastomeric membranes and electrodes, which are separately fabricated and patterned. In this contribution, we describe a method to monolithically fabricate DEAs that combines molding and microfluidic technologies. In our process, microfluidic channels having desired electrode geometry are formed in a single, monolithic elastomeric matrix, and then liquid conductive material is injected into it. This fabrication method is expected to be effective for making DEAs with multiple sets of electrodes as they can be formed at once. In addition, it potentially enables easy fabrication of DEAs with complicated shapes. We prove the concept through the fabrication and characterization of a DEA that contains a single set of electrodes. A PDMS (Dow Corning, Sylgard 184) and a liquid metal (EGaIn) are chosen as the materials for the elastomeric matrix and the electrodes, respectively. Polylactic acid (PLA) is used as the molding parts made by a commercial FDM 3D printer. After curing the PDMS matrix with microfluidic channel, EGaIn is injected using a vacuum filling method, forming a monolithic DEA ready to be tested. The fabricated DEA has an active electrode area of 10 mm × 10 mm with a gap between the electrodes of 0.5 mm. During the characterization, the device exhibited actuated deformation of 13.2 um at applied electric field of 9 V/um.

This paper presents the fabrication, electromechanical modelling and testing of a highly stretchable textile-dielectric elastomer capacitive sensor for capturing motion. The proposed sensor is made of conductive fabric as electrode and ultra-thin dielectric elastomer film as dielectric. This type of capacitive sensor exhibits high linearity and sensitivity as compare to available commercial sensors. By using basic calibration technique integrated with microelectronics, such sensors can easily capture motion and can also be paired with a mobile application, which is capable of visualizing the recorded 3D movement in real time domain, has the potential to be used in wearables.

Based on aligned multi-walled carbon nanotubes (MWCNTs), a highly stretchable and conductive polydimethylsiloxane (PDMS)/ MWCNTs composite fiber has been fabricated through a simple, effective and environmental friendly method. The prepared fiber shows excellent stretchability (up to 360% strain) and conductivity (4 S/m) with only around 2wt% of MWCNTs. In addition, the prepared fiber exhibits increased conductivity under tensile strain and cyclic stretching, which makes it an interesting candidate for a wide variety of applications in electronics. An application as conductive wires demonstrates that the prepared fiber will provide a new possibility for the development of next generation electronics.

The conductivity of DE can be further improved by using single-wall CNT (SWCNT), which has higher conductivity than carbon black. Electrodes using SWCNTs can be easily created by packing the CNTs in a spray can. This method was most recently developed by Zeon Corporation under the direction of Chiba et al. In the CNT dispersion, the CNT and 2% by weight sodium cholate were first added to the dispersion medium, and then dispersed using an ultrasonic homogenizer. When DE was produced using this CNT spray electrode on 3M acrylic, it was 2.2 times better than DE produced using the carbon.