This PDF file contains the front matter associated with SPIE Proceedings Volume 10966, including the Title Page, Copyright information, Table of Contents, Author and Conference Committee lists.

Space structures are one of the most critical components for any spacecraft, as they must provide the maximum amount of livable volume with the minimum amount of mass. Deployable structures can be used to gain additional space that would not normally fit under a launch vehicle shroud. This expansion capability allows it to be packed in a small launch volume for launch, and deploy into its fully open volume once in space. Inflatable, deployable structures in particular, have been investigated by NASA since the early 1950’s and used in a number of spaceflight applications. Inflatable satellites, booms, and antennas can be used in low-Earth orbit applications. Inflatable heatshields, decelerators, and airbags can be used for entry, descent and landing applications. Inflatable habitats, airlocks, and space stations can be used for in-space living spaces and surface exploration missions. Inflatable blimps and rovers can be used for advanced missions to other worlds. These applications are just a few of the possible uses for inflatable structures that will continued to be studied as we look to expand our presence throughout the solar system.

Inkjet material deposition is a promising approach to print multiple functional components for dielectric elastomer (DE) devices. The automatic fabrication process promotes reliable and repeatable results, and allows scaling to a few millimetres, which is advantageous in areas such as microfluidics and optics. We present here the printing and evaluation of novel ink formulae comprising silicone and a conductive filler. Carbon black, the conductive filler, is a popular electrode material. Although it has a relatively high resistance, it has been shown to produce compliant electrodes of good performance for dielectric elastomer actuators (DEA). Carbon black is added to liquid silicone rubber and solvents in order to obtain a solution that can be inkjet-printed. The silicone provides binding of the carbon particles into a soft matrix as well as bonding to the elastomer membrane on which it is printed. Each ink has unique electromechanical properties, e.g. sheet resistances ranging from a few kΩ/sq to MΩ/sq. We can apply different inks to provide conductive electrodes for DEA or piezoresistive components such as the dielectric elastomer switch (DES) - able to locally control charge over DEA - or simple resistor and electrode tracks. We discuss ink behaviours and printed sample components for networks of DEA and combined driving circuitry, all with soft, flexible materials.

Fabrication of arterial phantoms is enabled through specially developed additive manufacturing techniques in the Organic Mechatronics and Smart Materials Laboratory to produce high resolution 3D conjugated polymer structures. These techniques have been modified to enable fabrication of arterial phantoms through the direct ink writing of polydimethylsiloxane (PDMS) into a microgel support bath. This support bath behaves as a Bingham plastic, deforming under shear stress during extrusion but quickly returning to solid-state, thus supporting the PDMS and allowing the desired structure to be maintained, producing high-resolution complex geometries. Following curing and removal of the PDMS phantom from the support bath, PEDOT:PSS thin films are selectively deposited on the phantom surface. These films have demonstrated significant hygroscopic actuation under an applied electric field. These phantoms may be imaged with Particle image velocimetry (PIV) to characterize the effect of actively changing vessel geometry. PIV can provide the instantaneous full-field velocity profile and is a well-established technique to characterize flow through phantoms fabricated by conventional casting techniques to provide a standard of comparison. To effectively image the device via PIV, the optical properties of the components must be considered. To this end, PDMS and PEDOT:PSS have been employed due to their favourable transmission properties in the visible spectrum. Additionally, PDMS provides a compliant passive structure to be deformed with relatively low force, easing the performance requirements of the actuators. While this device focuses on the actuation of phantom vessel geometry, this technique may be extended to other applications in microfluidics to create onboard peristaltic pumping action and vascular networks.

The main method for Ionic Polymer Metal Composite (IPMC) electrode fabrication employs RED-OX deposition of noble metals. However, as this chemical plating technique is expensive, time-consuming and uses dangerous chemicals, we investigate the deposition of silver (Ag) electrodes by an additive manufacturing technique; stencil/ screen printing. The results indicate exceptional adhesion and mechanical stability of the cured ink to the Nafion. Moreover, the electrical properties (surface resistance measurements with the 2-probe method), microstructure (with Scanning Electron Microscopy), in addition to the electro-active properties (deflection measurements after slight hydration of sample in water and the application of square waveforms of 10 V in amplitude and 0.05 Hz in frequency) of the 5 mm x 20 mm Ag metalised IPMCs in a cantilever configuration are tested. Resistances are low, in the range of 1.1 - 1.6 Ω, and SEM micrographs indicate electrodes of 10 μm in thickness. Preliminary results illustrate a similar relationship of the induced displacements and the applied voltages and for the samples. The methodology for the fabricated Ag - stencil/ screen printed- electroded IPMCs is introduced, and the properties of these IPMCs are exhibited. This paper hence presents a proof of principle study, utilising a method that can significantly reduce IPMC production costs, as it decreases material prises by approximately 98% and fabrication times from 48 hours down to less than an hour compared to the state-of-theart technique.

Ferroelectric polymers are materials of choice for the development of pyroelectric sensor for IR detection and imaging. Additive manufacturing by inkjet printing is a promising technology that enable the rapid customization and development of high-resolution sensors without ink waste. In this context, it is important to optimize the formulation and printing of electronic ink’s with respect to the different interfaces involved in the fabrication process. In this work, we present the development and characterization of fully printed ferroelectric capacitor on a CMOS wafer. Firstly, Polyvinylidene fluoride trifluoroethylene [P(VDF-TrFE)] is formulated as an ink with respect to its relative viscosity and surface tension and it is inkjet-printed on Ti/TiN thin-film that act as bottom electrode. The printed layer is 3μm thick after crystallization annealing. Then, top electrodes were inkjet-printed on PVDF-TrFE using Ag based ink with different concentration, in order to study the interfacial interaction between the P(VDF-TrFE) and the top electrode. For all the ferroelectric capacitors, the dielectric and ferroelectric properties were analyzed. We demonstrated that the choice of the top electrode ink and it’s thermal annealing are key parameters that control the final electroactivity of the printed sensor.

Recently developed hydraulically amplified self-healing electrostatic (HASEL) actuators can utilize diverse material systems to create high-performance, muscle-mimetic actuators that can be tailored to specific applications. Initial versions of HASEL required cumbersome high voltage driving electronics and utilized a manual fabrication technique which was not easily adjusted to iterate designs. This presentation will describe a versatile and accessible fabrication technique using a computer numerically controlled (CNC) heat sealing machine to rapidly prototype complex designs of HASEL actuators. With this simple fabrication technique, we can create high performance HASELs which offer a variety of actuation modes. These actuators harness electrostatic zipping mechanisms to reduce operating voltages and facilitate a smooth actuation response to input voltage. Moreover, these HASELs feature linear strains over 100%, specific power of 816 W/kg, and cut-off frequencies of 125 Hz; these metrics enable actuators which are fast and powerful enough to jump. Using these devices, we create a continuum actuator capable of three-dimensional articulation and an active surface with programmable morphology. Additionally, we develop a portable electronics package for untethered operation of these soft robotic devices. This presentation will highlight the diverse design freedom inherent to HASEL actuators in terms of material selection and actuator design.

Silicone elastomers are widely used due to the favourable properties, such as flexibility, durable dielectric insulation, barrier properties against environmental contaminants and stress-absorbing properties over a wide range of temperatures ≈ -100°C to 250°C. Additionally they are mechanically reliable over millions of deformation cycles, which makes them ideal candidates for dielectric elastomers and stretchable electronics. In research on dielectric elastomers and other emerging technologies, the most common silicone elastomer utilized is Sylgard 184. One of the main advantages of this formulation is the low viscosity which allows for easy processing resulting in almost defect-free samples. Furthermore, its curing is robust and not as sensitive to poisoning as other silicone elastomer formulations. Commonly, the shortcomings of the final properties of Sylgard 184 are overcome by mixing the base polymer and the curing agent in non‐stoichiometric ratios and also by blending it with softer types of commercially available elastomers. Researchers rarely formulate their own tailor‐made silicone elastomers, probably due to the scarcity of information in literature on how to do this. This report aims to equip the beginners in silicone research with knowledge on how to prepare silicone elastomers with specific properties without compromising the mechanical integrity of the elastomer and thereby avoiding mechanical failure. Here the main focus is put on designing and formulating soft, reliable, and reproducible elastomers.

The structure of dielectric elastomer actuators (DEAs) is based on a thin elastomer layer, which is sandwiched in-between compliant electrodes. This capacitor like structure enables to build lightweight and energy efficient actuators with high design flexibility. An applied high voltage leads to a thickness compression and to a simultaneous area expansion of the elastomer, which can be exploited for actuation. Additionally, due to the capacitive nature of DEAs, the application of a DC voltage allows to maintain a position without consuming energy, making such actuators ideal for, e.g., valves. Despite being relatively easy to manufacture and providing large strokes, membrane DEAs suffer from low force outputs (for single layer systems). This paper presents a novel design concept which permits to retune the stroke-force trade-off of DEAs, by allowing to increase force output of the actuator at the expense of a reduced stroke. This is of particular interest for valve applications, which typically need high closing forces and low strokes in the submillimeter regime. The developed system is based on membrane DEAs biased with linear and non-linear springs. Such systems are typically known for high actuation strain and strokes but low force output, even lower in comparison to a single layer membrane DEA only. By means of the novel design concept, the force output of a single layer membrane DEA can be increased by a factor of 3 to 4. The novel actuator concept is initially illustrated, and subsequently validated via a graphical modeling concept on stripin- plane DEAs.

Dielectric elastomer (DE) actuators such as conventional double cone configurations have demonstrated that coupled DE membranes can be rigidly-coupled to execute antagonistic out-of-plane actuation. This paper presents experimental analysis of the compliant coupling in the emerging magnetically-coupled DE actuator (MCDEA) design, which exploits contactless magnetic repulsion to create a frictionless coupling between DE membranes. The compliance of this coupling enables the advantage of having two different actuation modes: antagonistic reciprocation and bi-directional expansion. However, since this compliance adds an additional degree-of-freedom, it increases the complexity of the actuator’s dynamics because the coupling distance can exhibit oscillatory behavior that is distinct from each of the actuator’s output oscillations in terms of phase difference and frequency. In this work, the relationship between DEA membrane stiffness and required magnetic force is experimentally analyzed before we present an investigation into the phase space of the compliant coupling and its relationship with the stroke amplitude. It is shown that the fundamental frequency of the MCDEA’s output stroke (46.1 Hz) corresponds to a super-harmonic frequency of the magnetic coupling that is double that of the output. The fundamental frequency of the coupling (87.6 Hz) is found to correspond to a second resonant peak in the MCDEA’s output with a much lower amplitude than at 46.1 Hz. This suggests that the dynamics can be exploited by controlling the excitation frequency for unidirectional push/pull or bidirectional expansion/contraction actuation, which creates potential for new compliant DE actuator and generator designs.

A robot capable of shape morphing, to change its configuration without modifying design, can adapt to environments better than a robot with only a fixed configuration. We propose a three-dimensional shape-morphing link that can achieve complex three-dimensional shapes by embedding a variable-stiffness element and multiple twisted-and-coiled actuators (TCA) into a soft elastomer. The TCA, with intrinsic softness, can be driven by electricity and generate forces 100 times larger than a human muscle of the same weight and length. In order to achieve a decoupled actuation of each TCA, the structure of the soft elastomer body is designed to isolate heat from other TCAs in the same body. By feeding back the position of markers on the shape-morphing link, we can precisely control the shape of the link. We demonstrate that a spatial mechanism consists of one or more these links can morph to a variety of configurations thus allowing for different functions. We envision that the proposed morphing link will have a wide range of applications in robotics locomotion mechanisms such as flying wings, walking legs, and swimming fins.

Monofilament Super-Coiled Polymer artificial muscles (SCPs) can be manufactured by twisting nylon filaments until a tight helical coil is formed. A recent advancement involves manufacturing copper-wound SCPs, which can be actuated using electric Joule heating. This paper describes the implementation of an apparatus to manufacture copper-wound SCPs. This apparatus also allows for variation and control of several manufacturing parameters of the SCPs. Using this apparatus, SCP specimens were manufactured with various combinations of these parameter values. The performance of these specimens was then experimentally characterized in order to optimize the strain, contraction time, and efficiency of the SCPs.

This paper describes the design and manufacturing of a modular actuator unit based on twisted and coiled polymer actuator. Twisted and coiled polymer actuators have attracted attention in the field of smart actuators and robotics. The proposed concept allows for the improvement of the response time of the twisted and coiled polymer actuator by incorporating active cooling method. This realization results in the development of modular actuator unit for bio-robotic system. The modular actuator unit consist of several twisted and coiled polymer actuators, a 3D printed frame and DC fans. The design and manufacturing of such modular actuator unit will be discussed in detail. Preliminary results about the performance of the twisted and coiled polymer actuators will also be presented.

High performance artificial muscles based on twisted and coiled polymer fibers have attracted considerable attention since their discovery in 2014. These artificial muscles generate tensile strokes as a result of a torsional actuation occurring within the twisted fiber. The torsion is due to a volume expansion and is related to the helical topology of the twisted polymer fiber or fiber composite. The volume expansion can be induced thermally, electrochemically, photonically or by absorption of small molecules, such as water. The magnitude of the torsional stroke and/or the torque generated has been successfully modeled using a single helix approximation. This paper presents a new type of tensile artificial muscle that exploits the properties of the double helix. Two fibers are plied to form the double helix structure and diameter expansion of the fibers generates a large lengthwise contraction in the plied structure. The process is successfully modeled using the single helix approach. The example plied double helix actuators were fabricated from cotton yarn impregnated with hydrogel. The cotton was pultruded through a solution containing the polyurethane based hydrogel. Actuators were made by air drying followed by co-twisting two lengths of the hydrogel-cotton and heat-setting at 60 degrees C. The samples were tested in isotonic mode by tensioning and fully immersing in water. The samples contracted in length when wet and the process was reversed on drying. The effect of hydrogel content and twist density have been investigated. Single hydrogel-cotton yarn samples showed negligible change in length when immersed in water, but two-ply double helix samples showed contractions of more than 10% in length. The length contraction of the double helices was attributed to the increase in fiber diameter during water absorption. The geometry changes were successfully modeled using a single helix approach.

A fishing-line artificial muscle actuator is typically tested under a constant weight load. This paper reports a new hysteresis phenomenon discovered by changing both load weight and temperature applied to a fishing-line artificial muscle actuator. Obviously the equilibrium position of an actuator changes by load weight. Interestingly, the equilibrium position also largely changes when the actuator is firstly heated and cooled just after exchanging the load weight. In this paper we call this phenomenon as temperature-dependent hysteresis. We have observed that the magnitude of the temperature-dependent hysteresis in the experiment reached the same level as the thermal contraction and was not negligible.

Folding sheet materials into cylindrical structures using an origami-based approach allows the sheet materials to be densely packed within a confined space that can be deployed when needed. Kresling pattern, which is a cylindrical origami pattern consisting of identical triangular panels with cyclic symmetry, functions under the spontaneous buckling of a thin cylindrical shell under torsional loading. The incorporation of smart materials, such as electroactive polymers, in origami structures can allow them to actively fold using electrical stimuli. In this study, finite element analysis (FEA) is performed in a single cell of Kresling pattern as well as the continuous Kresling pattern-based origami structure. Furthermore, different placements of dielectric elastomer actuators (DEAs) implemented within the origami structure are studied to identify the performance. The objective of this study is to validate the effectiveness of DEAs as a method to actively fold the origami structure, to deform and return to its initial state, and to investigate the geometric parameters on the folding structure incorporated with DEAs. Equivalent mechanical pressure and stress are used as loads in the FEA to simulate the electric actuation performed by the DEAs. By thorough FEA investigation, the impact of geometric parameters, material properties, and placement of DEAs on the origami structure for optimal performance is studied to avoid trial and error iterations for experimental studies.

Dielectric elastomers represent an attractive technology for smart actuator, sensor, and generator systems. In order to estimate how the performance of a membrane dielectric elastomer actuator (DEA) changes with the available design parameters (e.g., geometry, electrodes), numerous characterization experiments have to be performed. Alternatively, accurate simulations tools capable of predicting the system performance can be used to effectively optimize the design of DEA applications. In particular, Finite Element (FE) simulations allow to map global quantities as well as locally distributed quantities such as stress and strain fields as well as the electric field, and therefore appear as suitable for applications in which complex membrane geometries or electrode patterns are used. In this work, an FE model based on Comsol Multiphysics is introduced. This model is based on an electro-mechanically coupled formulation for large deformations, which also includes viscoelastic effects and electrodes geometry, while neglecting inertial effects. Due to the poor aspect ratio of membrane structures discretized with three-dimensional continuum elements, computation times appear as excessively large. To overcome this issue, the geometry is reduced to a two-dimensional structure. In order to simulate the local electric field distribution, both electrodes are discretized separately. For model identification and validation, specimens with and without imprinted electrodes are tested. Based on the developed model, the influence of the discretized electrodes is then examined, by varying electrode dimensions. Furthermore, fringe fields at the electrode edges are investigated in order to better understand local phenomena, e.g., the electrical breakdown mechanisms.

Dielectric elastomer(DE) has been recognized as one of the most promising materials that could be used as artificial muscle. Theoretical analyses on issues of DE mechanics, physics and material science in quasi-static state or small deformation have been widely carried out during the past few decades. When subjected to high voltage, the DE material exhibits complex dynamic behavior upon cyclic loading which is known as the viscoelasticity and electromechanical coupling. To understand the dynamic response of this viscoelastic material, a comprehensive model and quantitative research are required to be constituted. In this paper, a theoretical and experimental study is carried out to investigate the dynamic behavior based on experimental results of a rectangular DE actuator undergoing different actuating voltages. Firstly we build a comprehensive constitutive model, based on Gent energy function, by treating the permittivity as a strain-dependent variable. It is validated by experiments and, the ability to predict the behavior of the proposed model and the existed model is compared. The influence of the loading pattern of the applied voltage on the DE actuator performance is also studied. Experiments have been done to compare the maximum strains obtained while DE actuator is under a ramp signal and periodic signal respectively. The experimental results of the two types of strain exhibit the effects of loading pattern on the dynamic performance and inspire us to make an improvement to the constitutive model that can describe the dynamic performance better.

Dielectric Elastomer Transducers (DETs) represent an emerging technology with great potential for mechatronic applications. DETs allow to convert electrical energy into mechanical energy and vice-versa, making it possible to design actuators, generators, and sensors. These devices show many advantages like high energy density, silent operations, and low cost, but their practical applicability is strongly affected by their reliability and lifetime, which depend on both environmental conditions and electro-mechanical loads. Theoretical and experimental studies have recently been initiated to investigate the lifetime ranges of such devices for different loading conditions (e.g., mechanical, electrical, electromechanical). At present, the lifetime characterization of DETs has been conducted by means of stochastic models only. In principle, a better understanding of electro-mechanical fatigue mechanism of DETs can be obtained through an appropriate analysis of their underlying physics. In this context, this paper presents a novel modeling approach for electro-mechanical damage evolution of DETs. In order to describe the phenomena involved in the damage process in physically consistent way, a free-energy framework is adopted. Starting from well-established electro-mechanical free-energy functions, additional variables which account for both mechanical and electrical fatigue mechanisms are introduced. Singular models for damage accumulation are developed and integrated within the free-energy conservation principle, in order to dynamically simulate the life status of the dielectric material when subjected to combined electric and mechanical loads. Finally, the kinetic law for damage evolution history due to combination of different failure modes are introduced, and used to assess DETs reliability based on experimental observations.

Advances in soft robotic systems enable to create devices that can elegantly deal with complex environments and gently interface with humans. However, much progress in actuator technologies is required for adoption in practical and commercial scale-up implementations. An helical dielectric elastomer actuator (HDEA) can be a promising solution that fits in these applications. Nevertheless, in order to move forward from theory to practice, many aspects still need to be developed and advanced. For instance, current works may be insufficient to advance the topics in control systems applied to actuator geometry, in relation to relevant segments such as material synthesis and design for manufacturing. It is apparent that absence of a more complete and generalized dynamics model of an HDEA limits rapid engineering progress in this field. In some previous research, important contributions of electromechanical model were proposed for linear and nonlinear hyperelastic materials. However, other effects such as viscoelasticity and hysteresis in the strain-voltage relation were often neglected. This paper presents the dynamical model derivation of an HDEA using lumped parameters to model the electrical and mechanical behavior of the actuator. Furthermore, it covers the most imperative effects embedded in the dynamics of the actuator. In this work, the dielectric elastomeric transducer is modeled with VHB 4910 acrylic due to its well-documented material parameters needed in the non-linear strain energy functions.

Dielectric elastomer actuator (DEAs) have significant potential for biomimetic area. The DEA has viscoelastic nonlinearities such as hysteresis which will reduce control accuracy in the control system and limit the broader range of applications in the high accuracy field. However, most of modeling the DEA based on viscoelastic are with high order and not suitable for control strategy. In this paper, the hysteresis model is using Controlled Auto-Regressive Model (CAR) to characterize the hysteresis phenomenon between the output displacement and input actuation voltage. Recursive Least Square (RLS) is adopted to identify the hysteresis model. Moreover, a validation experiment is set to validate the model. We also find that the hysteresis is varied with changing the frequence and amplitude of input voltage.

Artificial muscles are characterized by a number of different performance measures, such as actuation strain, stress, strain rate, work and power output. A number of different testing methods are used to measure some of these parameters. The most commonly used test methods are the isotonic test that provides the actuation strain and the isometric test that gives a measure of the force or stress generated. Often the isotonic and isometric tests are performed at different levels of pre-strain. A simple mechanics based approach provides a theoretical framework that suggests that all these actuation parameters can be obtained by measuring the force-extension curves of the artificial muscle in the activated and non-activated states. A graphical method can provide estimates of the isotonic, isometric or any other test method that involves an external load. This presentation provides an overview of the mechanics based simple theory. Experimental data is compared for three types of tensile artificial muscle: pneumatic braid; shape memory alloy spring and a twisted/coiled polymer fiber. Tests were performed under isotonic and isometric conditions and when operated against a spring. All three of these materials show non-idealities in their mechanical behaviour, including load-unload hysteresis and plastic deformation. When these non-idealities were taken into account, the mechanics based approach provided satisfactory estimates of the isotonic, isometric and spring actuation behaviour. The approach provides a simple and standardized method for characterizing the static actuation performance of any type of tensile actuator.

We present a simple open-loop method to suppress the viscoelastic drift of dielectric elastomer actuators (DEAs). Viscoelastic creep is one of the drawbacks of DEAs, especially when made with acrylic elastomer membranes (VHB). This leads to a time-dependent strain response to a voltage input, thus making the precise control of DEAs difficult. Closed-loop methods can be used to mitigate this issue, but they require additional sensors for the strain feedback, or a complex power supply if capacitive self-sensing is used. Our method is based on quasilinear viscoelasticity and relies on two simple characterisation tests: 1) a slow voltage ramp to characterise the steady-state strain versus voltage behaviour, and 2) a strain versus time response to a voltage step input. The model then enables to calculate the voltage profile required to obtain a target strain output. A simple analytical expression can be used to generate strain step responses. The method enables to suppress the viscoelastic drift and to increase the response speed of DEAs. To obtain arbitrary strain profiles (sinusoid, square, etc.), the required voltage can be numerically calculated, thus making the method a simple and versatile tool to compensate the viscoelasticity, and generate precise strain profiles from DEAS, without the need for closed-loop operation.

In this paper, we establish the thermodynamic theory of dielectric elastomer under electromechanical coupling field, different effects are considered, including polarization saturation, strain hardening and stress softening. The instability and dynamic performance of dielectric elastomer is also studied. At last, the devices and application of dielectric are introduced, such as soft robot, energy harvester, gripper.

Dielectric Elastomer Transducers (DETs) are a promising technology for the development of actuators, generators and sensors with high performance and low cost. Practical application and economic viability of DETs is strongly affected by their reliability and lifetime, which depend on the maximum strain and electrical loads that are cyclically applied on such devices. To date, only limited information is available on the fatigue life performances of dielectric elastomer materials and of the transducers made thereof. This paper reports on a first lifetime constant electric-stress test campaign conducted on 38 free-expanding frame-stretched circular DET specimens, made of the silicone elastomer film Elastosil 2030 250/150 by Wacker with blade-casted carbon-black silicone-elastomer electrodes, that have been subjected to nearly square wave electric field signals with 1 Hz frequency, 50% duty cycle and with amplitudes ranging from 65 MV/m to 80 MV/m.

Slide ring materials (SRMs), a novel type of elastomer recently developed, are a promising material for dielectric elastomer actuators (DEAs), because of their unique properties such as high dielectric permittivity and low hysteresis. However, limited information is available on the electromechanical characteristics of SRMs. Here, we report on preliminary results of our ongoing study that is intended to clarify the electromechanical performance of SRMs, while comparing with other commercial elastomers (VHB 4905 and CF19-2186). Characterizations are performed using DEA samples with an aspect ratio of 10 (length:width = 1:10) that are mounted on a universal testing machine measuring the actuated force and strain. All the elastomers were processed into the same DEA sample geometry, and were tested under identical experimental conditions. The results show advantageous features of the SRMs, such as, much larger actuated force and strain compared to the other commercial elastomers under the same electric field.

Slide-ring materials (SRM) are novel polymeric elastomers which are prepared from necklace-like supramolecule, polyrotaxane, consisting of ring molecules and axial polymer. By cross-linking rings of polyrotaxanes, axial polymer chains are connected via ring molecules which can slide on polymer chains. The slidability of the cross-linking points leads to softness and deformability of SRMs. In this work, we investigate the unique mechanical properties of SRMs to apply them to dielectric elastomer actuators (DEAs). From dynamic viscoelasticity measurements, we have found that SRMs exhibit entropic elasticity and low elastic modulus. The stress strain relation of SRMs under uniaxial deformation follows ideal rubber elasticity model in a wide strain range, suggesting homogeneous and reversible network deformation caused by the sliding of cross-linking points in SRMs. The ideal rubber elasticity of SRMs results in their softness and low hysteresis under large deformation, which are advantages for the application as dielectric elastomer actuators.

A dielectric elastomer actuator (DEA) is a soft actuator with low manufacturing cost and high energy efficiency. The structure of a DEA consists of a dielectric material interlayered with elastic electrodes, and DEA expands when an electric field is applied. The degree of freedom of movement of the DEA can be increased by devising the electrode arrangement in DEA. The performance of DEA is determined by permittivity, Young's modulus, and applicable electric field. Material properties including hysteresis loss are also important when a DEA is used as a sensor or high precision actuator. Generally, silicon and acrylic rubbers are used as the dielectric layer. This study focused on the use of a slidering material (SRM) as a more suitable dielectric for DEA than silicone and acrylic rubbers in terms of its dielectric constant and hysteresis loss. In a previous study, a DEA was developed using SRM as a dielectric, and the image correlation method (ICM) was applied to measure the strain distributions in a two-dimensional plane and the basic characteristics of DEA with one pair of electrodes. Here, the strain distribution was measured when the electrodes of the DEA were segmented into several pairs as the next step in the investigation of its basic characteristics. Patterns of electrode arrangements and the amount of DEA prestretching were changed, and strain distribution was measured using ICM.

Electroactive polymer (EAP) is a kind of smart material that exhibits a large deformation on the application of a small potential across the electrodes. On the contrary, the materials can also exhibit sensorial behavior by generating a small electrical potential on the application of mechanical force. These characteristics make these materials to be a promising candidate for applications involving actuators with self-sensing ability. In this work, we report on the development of integrated sensing and actuation of ionic polymer–metal composite. Integrated sensing is accomplished by crafting discrete sensing and actuation sections over a single device by patterning the surface of the electrodes. A control scheme and estimation technique are implemented for self-sensing feedback control that uses the electrode resistance change during deformation. The artificial neural network is used to handle the hysteresis during modelling the relation between electrode resistance change and actual tip displacement. While the need for stable control to overcome nonlinearity and inherent back relaxation behavior of the material is accomplished by using a robust sliding mode controller. The developed model and controller are experimentally verified and found to be capable of predicting and controlling the actuators with excellent tracking accuracy without the need for a separate position sensor and makes the device to perform as a self-sensing actuator.

There is a need for buoyancy engines to modulate sensor depth for optimal positioning and station-keeping. Previously, our group developed a highly efficient Ionic Buoyancy Engine that does not have any moving parts and that may be miniaturized. The engine is an osmotic pump triggered by an electric potential change applied to electrodes in an internal closed chamber. This leads to a local reduction in the ionic concentrations near a semipermeable membrane, which in turn triggers water displacement. In this study a coupled finite element model is used to solve the electrical, chemical, osmotic pressure, and fluid domains. The Nernst-Planck and Poisson equations predict the electro-chemical activities; the osmotic pressure, based on thermodynamic considerations, predicts the pressure across the semi-permeable membrane; and finally, a laminar fluid model is implemented to predict the displacement of water. The model is compared with our previous experimental data, in particular, the effect of the surface area of the electrode and the applied electric potential. In both cases the trends in both models were matching. Finally, the numerical model is used to predict the behavior of the engine due to change in chamber size.

An Ionic Polymer-Metal Composite (IPMC) has characteristics as a sensor as well as an actuator. Zhu has recently proposed a multi-physical model representing sensor voltage of a deformed IPMC. This paper discusses approximation methods aiming at fast simulation or control system design. First, we linearize the nonlinear partial differential equations (PDEs) of Zhu’s model. Next, this paper considers two types of spatial discretization methods, Finite Difference Method and Finite Element Method. We have found that it is not necessary to use a large number of sample points or finite elements for simulating the sensor voltage.

The phenomenon of back-relaxation in ionic polymer-metal composites (IPMCs) has attracted the interest of the scientific community for two decades, yet a conclusive explanation of why and when it occurs is presently lacking. Recent studies have suggested that the interplay between osmotic pressure and Maxwell stress could be the key mechanism underlying back-relaxation, but experimental proof is missing to substantiate this hypothesis. Here, we seek to bring forward new evidence from the technical literature in favor of this explanation by analyzing existing experiments on contactless actuation of ionomer strips in an electrolyte solution. We demonstrate that Maxwell stress dominates osmotic pressure in the contactless actuation of ionomers, thereby supporting the claim that Maxwell stress could help understand back-relaxation in IPMCs.

Dielectric Elastomer Transducers (DETs) integrated into inflatable structures can form the basis for soft, low mass robots. Such robots will have very high packaging efficiency and be simple to deploy. These attributes, combined with the high power density of DETs make them ideal for space robots. In this paper we present a study of different motions achieved from the actuation of three distinct simple experimental designs. Firstly, the dome actuator constructed from a sheet of silicone rubber with segmented electrodes. Secondly, an elongation of the former, capable of producing locomotory motion from phased actuation of segments. Finally, a rolled cylindrical design varying the seam geometry, and electrode position and composition to produce different resonant and non-resonant motion. This study is comprised of experimental results, and finite element modelling of each design using commercially available FEM software. The different structures are simulated undergoing inflation and actuation, and the results compared to experimental data. Modal analyses of the inflated cylindrical structures are also compared with the frequency responses of the experimental models. Extrapolation of these basic units to more complex structures, designed to complement or replace existing space equipment, is presented for discussion alongside the remaining challenges.

Dielectric elastomer switches have shown large potential for integrating signal processing directly into multifunctional dielectric elastomers. Previously presented continuum dielectric elastomer switches (cDES) utilize percolation effects within piezoresistive membranes to directly switch high voltages, controlling dielectric elastomer actuators. The here presented geometric dielectric elastomer switches (gDES) use geometric air gaps in encapsulated soft sensor structures to switch both high and low voltages. gDES consist only of soft materials such as silicones and carbon-doped conductive silicones. The structured conductive electrode areas are arranged in such a way that they create small gaps within a shielded cavity. The gap can be opened or closed by an external deformation or pressure. Depending on the electrode design and mechanical characteristics, the necessary amount of deformation and pressure can be tailored exactly to the requirements of the application. Arrays of these switches can be integrated in soft robotic grippers and extend the features of those grippers by touch and shear force detection. Furthermore, gDES can act as limit switches and can be introduced in automation technology. One of the key advantages is that the switches themselves are entirely shielded and not affected by environmental influences. gDESs have an advantage of operation at lower voltages than related cDES. This reduces the necessary amount of driving voltage and opens up the application in classic automation technologies and robotics. gDESs possess conductive silicone composites containing conductive fillers. The switching points and the general behaviour (normally-open [NO] or normally-closed [NC]) are tuned by the geometry of conductive parts associated with the shielding silicone structures. Related to percolation-based cDESs, the gDESs are produced by classic microelectronic production technologies, such as soft lithography. We present the principle design of different gDESs and arrays of the same, the production techniques and first results of distributed touch sensing for soft robotic grippers. Methods and design parameters for adjusting the switching characteristics are presented and experimentally evaluated.

Animals make use of soft tissues and muscles to produce fluidic motion with superior deformability and adaptability. Soft robotics focuses on mimicking these natural soft systems to produce similar motion. Common approaches to achieve actuation in soft robotics are pneumatics, fluidics, shape memory materials, magnetic fields, chemical reactions and electroactive polymers (EAPs). EAPs are particularly interesting due to their high efficiencies, lightweight design and superior structural compliance. Dielectric elastomer actuators (DEAs), an EAP, can produce large strains, low cost and complexity of fabrication. Performance of a DEA depends on intrinsic material properties like relative permittivity and Young’s modulus. Conventional approaches to manipulate either of these material properties have made use of solid fillers, chemical additives and modifications of polymer backbone, and are generally accompanied with undesirable effects on other properties. In the present work, we demonstrate the fabrication of self-contained liquid filler-polymer composite, with synergetic effects on electrical and mechanical properties of the resulting matrix. A high-k, non-reactive liquid filler was hand mixed with PDMS (polydimethylsiloxane). These composites show an increase of 2 times in the relative permittivity (dielectric constant) and softening of the matrix (more than 50 times decrease in the Young’s modulus), compared to the pristine polymer. The composites can be actuated without pre-stretch with visibly detectable deformations and the figure of merit for electro-mechanical performance was calculated at an impressive value of 94. These ultra-soft composites can be used for applications such as soft robotics, optoelectronics and wearable electronics.

Stimuli-responsive hydrogels are polymer gels possessing the ability to absorb or release solvent, resulting in a respective change of volume. This volume change can be triggered by applying a chemical or electrical stimulus to the gels placed in a solution bath. To describe the chemo-electro-mechanical behavior of these hydrogels in the framework of the Theory of Porous Media, they have to be subdivided in a solid phase, fluid phase and an ionic phase. In this theory, the interaction of the different phases is directly incorporated. Due to the complexity of both, the material and the model, a large amount of material parameters is essential. The determination of these parameters is a challenging task. In this investigation, also the interaction between hydrogel (solid and fluid phase) and surrounding solution bath has to be considered in order to determine the viscoelastic behavior of the gel. Hence, in the present work, polyelectrolyte hydrogels are investigated in consideration of the mechanical characteristics via a tensile test. In the experimental setup the stress is determined by a force sensor and the deformation is analyzed by using a gray scale correlation. Due to the fact, that the mechanical behavior of such multiphasic materials depends on the solid-fluid ratio, the gel is investigated under different swelling degrees. The acquired data then can be used to enhance the material equations. So, an enhanced prediction towards possible applications is gained.

Soft-smart functional devices and machines, made of soft-smart materials and structures, have been augmenting, supplementing, extending, and replacing their conventional hard equivalents due to the fact that they provide intrinsic compliance matching and biocompatibility. These new capabilities enable them to have safer interactions with human beings and natural environments, and better resilience and adaptability to various environments. Dielectric elastomer actuators (DEAs) and soft electroadhesion (EA) grippers are two promising soft-smart mechanisms and structures that can be used for active actuation and adhesion for soft robots. We integrate DEAs and soft EAs into monolithic soft structures capable of self-actuation and self-adhesion. These structures are fabricated by casting customized electrode materials onto dielectric elastomer membranes. Concomitant or separate actuation and adhesion can be achieved in active areas of these structures via customized control strategies. In this work, we also present a comprehensive survey of existing DEA and EA combination work. Soft-smart DEA-EA structures could impact on many fields including robotics and material handling technologies.

In this paper, we propose a soft robotic gripper to be mounted easily and to have high actuation force by harnessing electrostatic and hydraulic phenomena. Specifically, we develop a soft actuator to consist of swelling pouches, a silicon backbone beam, and a supplying pouch with electrodes on its both surfaces. The two pouches include dielectric fluid, and they are connected. When a high voltage is applied to the electrode of the supplying pouch, the fluid in the pouch moves to the swelling one. In addition, we present a soft gripper using the soft electro-hydraulic actuators.

A wearable glove equipped with various types of dielectric elastomer sensors is described. The capacitive flexible sensors serve for different technical operation functions controlled by defined finger actions. A first type is a pressure sensor located at the thumb of the glove. The applied pressure of the thumb on another finger can tune a technical function. By operating a contact sensor, the adjusted value can be frozen. Contact sensors detect the touch between different fingers. In contrast to other proximity sensors, the electrodes are distributed on two fingers. The approach of one finger to another one increases the capacitance between the electrodes. This sensor type can be used for switches to trigger a technical function such as activation or deactivation. A third sensor type consists of three electrodes where two electrodes are located on one finger and the third electrode is located on another finger. Sliding the second finger on the first finger causes an increase or decrease of two capacitances depending on the relative position of the third electrode in relation to the first two electrodes. This sensor can be used as a slider for tuning a technical function such as brightness or loudness. An advanced version of this sensor is a combination of four electrodes on one finger and a fifth electrode on a second finger. Here, the sliding of the fifth electrode on the other four electrodes changes four capacitances. This configuration works as a two-dimensional slider similar to a computer mouse to control a cursor on a screen. All capacitive sensors are manufactured with silicone elastomer components, where the electrodes contain carbon black particles to become conductive. The sensors are integrated in the fabric of a glove. In addition, the glove is equipped with an electronic compartment containing a microprocessor to measure and process the sensor capacitances. The data is transmitted wirelessly to a personal computer, where the status of the sensors can be demonstrated graphically. The paper shows some examples of finger actions and the corresponding reactions of the sensors.

Dielectric elastomer actuators (DEA) enable to build compact, silent and lightweight systems capable of a large actuation bandwidth up to the kHz range. They consist of a thin elastomer film between two electrically conductive and flexible electrodes. If a high voltage is supplied to a DEA, the opposing electrical charges on the two electrodes result in electrostatic forces which produce a controllable deformation. This work presents a systematic design approach for the design of DEA driven pneumatic pumps for mobile applications. Due to the combination of large actuation bandwidth and the high compactness, DEA appear as highly suitable for designing pumps for such applications. Silicone based circular out-of-plane membrane DEAs (also referred to as cone DEAs) combined with biasing springs are studied in this work. A commercially available pump mechanism, consisting of a rolling diaphragm and check valves, is used as an experimental platform to validate the design strategy. Based on characterization data of both DEA membrane and pump, a systematic design approach based on graphical method is performed. The proposed design method allows to predict the system performance at high actuation frequencies by accounting for both static and dynamic effects, as well as external loads, without relying on complex material models. The design procedure forms the basis for building the pump by utilizing rapid prototyping. The performance of the pump can then experimentally evaluated in terms of pressure and resulting flow rate to validate the design concept.

Recent research proposes dielectric elastomers as actuators for mechanical suppression of pathological tremor. Dielectric elastomers offer several advantages compared to traditional actuators, including decreased weight, smaller profile, reduced rigidity, and better scalability. The similarities between dielectric elastomers and human muscle enable application of the actuators in a bio-inspired approach, where external artificial muscles directly actuate against tremor produced by the underlying human muscle. Two approaches exist for dielectric-elastomerbased tremor suppression: fully-active and tremor-active. In the fully-active approach, the dielectric elastomer actuators must actuate against tremor while also activating to follow the voluntary motion of the joint. In contrast, the tremor-active approach only requires activation against the tremor; the human sensorimotor system compensates for the passive dynamics of the dielectric elastomers. The tremor-active approach is unique to dielectric-elastomer-based tremor suppression since the soft actuators can have mechanical impedances on the same order or less than that of the human body. These two approaches have tradeoffs between actuation and viscoelastic requirements: the tremor-active approach decreases the actuation requirements, but applies limitations to the stiffness and viscoelastic characteristics of the actuator. This paper quantifies the necessary actuator parameters to achieve acceptable tremor suppression performance for each approach. The necessary parameters are normalized by joint parameters to generalize the results for tremor suppression about any joint.

The growing demand for wearable sensors has led to advancements in sports rehabilitation, robotic exoskeletons, etextiles, and human-machine interfaces, among other fields. In particular, stretchable tactile sensors for human motion tracking have become essential to the shift of healthcare activities towards more personalized, data-centric frameworks. In this paper, the fabrication, characterization, and deployment of an elastomeric capacitive strain sensor for tracking the Neck Motion Complex (NMC) is presented for physiotherapy applications. The sensor patch consists of a flexible and biocompatible dielectric PDMS film coated on either face with patterned graphene electrodes and encased in protective layers for stick-to-skin applications. The sensor transduces the strain from planar neck bending into a capacitive change between the electrode layers that is quantified and calibrated against the angle of bend. The sensor patch is worn on the side of the neck over the sternocleidomastoid muscle to capture lateral bending motions in our tests. We also present a simple and scalable fabrication method using easily available and lowcost materials and tools. Furthermore, a miniaturized built-for-purpose capacitance data acquisition system with an onboard memory card was designed and tested. The complete system is fully wearable, autonomous, and non-intrusive. Calibration of the sensor versus strain and neck bend was achieved using a high precision tensile tester and Aurora EMI system respectively. Characterization of the electrode performance under strain was also conducted. It is hoped that further iterations of the sensor design will quantify range of motion (ROM) and multi-plane neck motions.

With the focus on providing a sense of touch in robots, enabling feedback in virtual reality (VR) and augmented reality (AR) environment, telerobotics, remote sensing and improving user experience with touch sensitive devices like display kiosks and smartphones, haptic interfaces have become critical as they can convey information quickly. A human hand can feel different physical parameters such as roughness, softness and vibration and discern them as textures of the surface. Most of the technologies being employed for haptic feedback currently rely on simulating the perception of texture change, however few of the technologies like microfluidics and electroactive polymers (EAPs) can create actual topographical changes on the surface. Additionally, most of these haptic devices are opaque and they often serve as mere touchpads whilst the visual component of the simulation is projected elsewhere, so the user appears to interact with the simulated object indirectly. Dielectric elastomer actuators (DEAs), an EAP, is of peculiar interest owing to their characteristics like large actuation strains, facile fabrication, low costs of manufacturing and low power consumption. Herein, we demonstrate a large area, transparent tactile feedback device with 4 individually controlled active regions, that can be integrated onto electronic displays to provide unobstructed topographic texture change. We fabricate the device in a unique architecture, with the elastomeric layer, compliant electrodes, and the soft passive layer as all transparent materials. These devices show high transparency of over 70% in the visible region of the spectrum, and surface deformation of ~165 μm.

As a continuously growing field of robotics, soft robotics is the science and engineering of the robots primarily made of soft materials, components and monolithic active structures such that these soft robots can safely interact with and adapt to their environment better than the robots made of hard components. Soft robotics offers unprecedented solutions for applications involving safe interaction with humans and objects, and manipulating and grasping fragile objects, crops and similar agricultural products. The progress in soft robotics will have a significant impact especially on medical applications such as wearable robots, prosthetic devices, assistive devices, and rehabilitation devices. Robotics research and application community need smart or active or live materials that can change their mechanical, electrical and chemical properties as per the stimuli applied and can be printed into a form/shape with a function to realize soft robots. The progress in soft robotics strongly depends on the progress in materials science and technology. After briefly describing what characteristics differentiate the field of soft robotics from the conventional hard robotics and significance of smart materials for soft robotics, we will answer the question of where we are in soft robotics to establish prosthetic hands with features which will bring them one step closer to their natural counterparts. The primary feature of such a prosthetic hand should be to interpret and receive the hand user’s intention noninvasively, and equally importantly send sensory feedback about the state of a prosthetic hand to its user noninvasively in order to help “restore normality” for prosthetic hand users. We will also report on the progress we have made in the establishment of a fully 3D printed, low cost, low weight and low foot-print transradial prosthetic hand at our center of excellence, ACES, at University of Wollongong. Current prosthetic hands are heavy and expensive with many degrees of freedom to control, requiring a significant amount of battery power. Further, they do not contain sensory or haptic feedback, making their acceptance physically and sensationally worse. With recent progress in soft smart materials and additive manufacturing techniques, we disclose a low cost, low power, low weight, low foot-print prosthetic hand equipped with touch/pressure sensors and strain sensors to provide life like sensory feedback to its users. This soft hand with programmable compliance is designed to have a monolithic topology (i.e. one-piece geometry) with its finger joints simulating motion of the natural fingers such that the hand conforms to the shape of the object it grasps. The hand is fabricated such that it does not require any assembly; ready to be used straight from the fabrication process. It is articulated with a limited number of actuators to provide adaptive grasping ability and address significant deficiencies of the conventional prosthetic hands made of rigid joints and links.

We present variable stiffness dielectric elastomer actuators (DEAs), combining a single DEA actuator with embedded shape memory polymer (SMP) fibers, which can be electrically addressed to locally reduce the stiffness by a factor of 100. The device accommodates two SMP fiber sets oriented perpendicularly on both sides of a DEA, which enables a selective deformation in two different directions. During electrostatic actuation, one of the SMP fiber sets is softened by Joule heating, whereas the unaddressed fiber set remains stiff and determines the actuation direction, principally along the direction of the soft fibers. Using SMPs as a latching mechanism allows holding a given actuated position without any power, which leads to much longer lifetime in static (DC) conditions. The DEA is made of a prestretched acrylic elastomer (VHB, 3M) sandwiched between carbon-loaded polydimethylsiloxane electrodes providing an active area of 20 mm x 20 mm. The SMP fibers are electrically isolated from the DEA electrodes using 40 μm thick acrylic elastomer films. Each SMP fiber is 100 μm thick, 750 μm wide and is on a 6 mm pitch. The ratio of locked strains in the direction of the heated and the unheated fibers is measured to be 1.80 for a square DEA. This ratio is increased up to 8 with a cross-shape DEA using only two variable width fibers, one aligned vertically and the other horizontally.

Optically-switched composite materials based on semiconducting materials have the potential to simplify the circuitry required to control artificial muscles. This contactless control method has the potential to improve visual technologies by enabling controllable haptic and morphing interfaces. Optically-switched active displays could provide enhanced user interaction, especially for those with visual impairments. Research into morphing interfaces with dielectric elastomer actuators (DEAs) centralizes on segmented electrode architectures that can achieve large active strains in multiple degrees of freedom. However, controlling the activation of multiple electrodes typically requires an array of discrete rigid components (e.g. MOSFETs) as well as the separation of high-voltage power lines and low-voltage control signals. In this work, we develop a photo-switched DEA system that removes the need for wired control signals, reducing complexity. Photonic switching of DEA electrodes is achieved by exploiting the light-dependent resistance of a thin film of deposited amorphous silicon (a-Si). Samples with layer thicknesses of 0.84 μm have been fabricated using plasma enhanced chemical vapor deposition. Breakdown voltages of above 6kV were obtained when using a nonconducting substrate (glass). Preliminary testing of the system shows that voltage swings of up to 865V can be achieved between ambient and direct illumination, producing an out of plane actuation of 2 μm in a weight-biased DEA disc actuator. Further tuning of the electric circuit should lead to larger actuation strains. Future work will focus on the control of multiple DEA electrodes using localized light patterns as well as testing and characterizing other materials to improve the voltage swing across the DEA.

Soft robotics is an emerging area that attracts more and more attentions. Dielectric elastomers could deform sustainably subjected to external electrical stimuli and become promising materials for soft robots due to the large actuation strain, low elastic modulus, fast response and high energy density. This paper focuses on the fabrication, applications and design of the dielectric elastomer spring-roll bending actuators. The actuator with large electrically induced bending angle has been made and demonstrated the applications in flexible gripper and inchworm-inspired soft crawling robots. The performance of the gripper and the crawling robot has been characterized. Thermodynamic model has been established to investigate the deformation and failure of such actuators. Comparison between theoretical and test results shows that the model is suitable for the prediction of the performance of the actuator. The influence of some design parameters on the performance of the actuator has been analyzed and discussed based on the model.

Soft robotics research has been motivated in part by the versatility and functionality of human muscle. Researchers have tried to mimic the speed and performance of human muscle by using soft fluid actuators; however, these actuators are often slow and bulky. Research conducted in the use of dielectric elastomers has proven to be promising. These dielectric elastomers can produce large strains using high voltage electrical input. However, the development of these dielectric elastomer actuators has been inhibited due to their susceptibility to dielectric breakdown and electrical aging. One recent technology that can solve these issues and advance the field of soft actuators, is that of the hydraulically amplified self-healing electrostatic (HASEL) actuator. Such actuators are comprised of a liquid dielectric enclosed in an elastomer shell with electrodes on either side of the shell. Incorporating a liquid dielectric dramatically reduces the impact of dielectric breakdown on the performance of HASEL actuators and allows for hydraulically-coupled modes of actuation. However, the voltages that are required to operate these actuators are still challenging for commercial applications. Our work uses a simulation-driven approach to determine design parameters for donut HASEL actuators that provide a high actuation strain at a reduced pull-in voltage. We outline a modeling approach that is comprised of calibrating the properties of a multiphysics finite element model using actual HASEL actuator experimental data. The model is validated using a donut-shape HASEL actuator from literature. The model is then applied to determine the optimal electrode size and fluid dielectric permittivity for achieving a low operating voltage. This simulation-driven design assists in the fabrication of soft actuators with potential application to a variety of industries.

Soft, stretchable and light-weight transducers are most sought after for research on advanced applications like stretchable electronics, soft robotics and energy harvesters. Stretchable electronics require elastomers that have high elongation at break, high dielectric permittivity and high breakdown strength. Commercial silicone elastomer formulations often do not encompass all the necessary properties required to function effectively as stretchable transducers but they are used out of familiarity. In this study, most commonly used commercial silicone formulations are formulated with different stoichiometry and also blends of these formulations are made in order to manipulate their resulting properties. The properties of these blends like ultimate stress and strain, Young’s modulus, dielectric permittivity and breakdown strength are investigated and mapped to identify those that have the best suited properties for fabricating soft stretchable devices. On a research level, Sylgard 184, Sylgard 186, Ecoflex 00-50, Ecoflex 00-30 and Ecoflex 00-10 are widely used for fabricating such soft devices and hence they will be worked upon in this study. The elastomers obtained using the methods of mixing illustrated here can act as a starting point for conceptualizing the feasibility of a product on research level.

Ras Labs’ Synthetic Muscle technology promises to resolve major issues facing amputees, most notably the pain of prosthetic slippage and tissue breakdown. Synthetic Muscle, comprising electroactive polymers (EAPs), actively expand or contract at low voltages, while offering impact resistance and pressure sensing, in one integrated solution. In collaboration with United Prosthetics (UPI), customer testing was initiated with these EAP based pads located in strategic areas of the prosthetic socket of both below knee (BK) and above knee (AK) amputees for evaluation and feedback, with very promising results. The goal is to give amputees natural locomotion with a worry-free prosthesis, maintaining dynamic perfect fit throughout the day and preventing tissue damage from even beginning to occur. Robotic gripper applications, with sensing fingertips, were also prototyped. Characterization of Synthetic Muscle as dual use pressure sensors was investigated, with variable voltage observed and quantified when the EAP sensor was mechanically compressed. The integration of EAP shape-morphing actuation into grippers was also initiated. The EAP shape-morphing control is expected to be modulated as needed by controlling the voltage level. This technology is expected to provide for an adjustable prosthetic liner or socket that can maintain dynamic perfect fit and for biomimetic prosthetic hands and robotic grippers.

DEAs have been studied for decades as a potential polymer artificial muscle for its excellent mechanical properties and large electric field-induced strains. The structural design of DEAs enhances the actuator performances and converts the electrically–controlled strain to diverse motions including linear motion, bending, twisting and moving with multiple degree of freedom. Inspired by the Venus Flytrap (VFT), whose bistable leaves and local strain redistribution are crucial to the fast closure speed, we developed cylindrically-curved bistable laminated DEAs, and activated the bistable shape transformation by electrically tuning the strain field. To obtain the bistable structure, two elastomeric films are prestrained biaxially and bonded orthogonally to a stiffer elastic film in the middle. Due to the elastic energy minimization, the originally flat laminate immediately self-equilibrated to two bistable cylindrical shapes, with the curvatures orthogonal to each other. Basic theoretical analyses on the interaction of prestrains and bending curvatures provide guidance to the design of bistable morphing shapes. The prestrains on the DE films not only generate various curved shapes, but also decreases the film thickness and therefore reduces the actuation voltage. Similar to the fast closure of VFT, which is activated by the strain redistribution resulted from the motor cell enlargement, our bistable DEA achieves reversible bistable shape transformation by voltage-induced strain change at the area covered by compliant electrodes.

Conducting polymers are active materials that exhibit an interesting bidirectional electromechanical coupling, where an input voltage results in the displacement of the film and a voltage is produced when a displacement is applied to the film. Mechanical deformation of the transducer by external mechanical loads causes movement of ions, and the generation of voltages. In this work, a dual sensing and actuation model for conducting polymer is described. The model comprises an RC lumped circuit, representing the electrochemical model, a mechanical model described by a dynamic Euler – Bernoulli beam theory, and an empirical strain-to-charge ratio. All three submodels are presented in a self-consistent Bond Graph formalism. The predictions of this model are then demonstrated by comparing with the experimental sensing and actuation results of a 17 µm thin poly(3,4-ethylenedioxythiophene) – based trilayer transducer, showing that the complete electromechanical model elucidates an effective approach to describe both sensing and actuation.

Traditional robots – made from electric motors and gears – are noncompliant, complex, and bulky, which limits their ability to perform in unstructured environments and increases risk during human-robot interactions. As a result, there have been efforts to design actuators from soft, compliant materials for use in versatile and adaptable robots. Electrohydraulic Peano-HASEL (Hydraulically Amplified Self-healing ELectrostatic) actuators have shown promise as linearly contracting soft actuators with high-speed operation, scalability, and simple design. Coupled with their versatility in fabrication and material systems, Peano-HASEL actuators have broad potential in robotics. In this presentation, we derive an analytical model that accurately predicts the quasi-static stress-strain behavior and scaling laws of Peano-HASEL actuators without using fitting parameters. We provide extensive experimental validation of this model using actuators constructed from heat-sealable biaxially-oriented polypropylene shells, vegetable-based transformer oil, and ionically-conductive hydrogel electrodes. Despite using a simple set of geometric assumptions, we find robust agreement between model and experiment. From these results, we identify several straightforward methods for tuning and improving the performance of Peano-HASELs – including the creation of actuators optimized for maximum strain or maximum force, and a strategy for improving the specific energy of these devices from 6 J/kg currently to > 1000 J/kg. The basic principles of these methods are applicable to a wide range of HASEL actuators. Further, we experimentally demonstrate actuators with increased specific energies following the predictions of these modeling results. Moving forward, these results will serve as a roadmap for the development of high-performance Peano-HASEL actuators, opening new applications in robotics.

Bistable electroactive polymers (BSEP) combine shape memory with large-strain actuation at the rubbery state to achieve rigid-to-rigid actuation. The stiffness of the BSEP is tunable via glass transition or phase changing. The reversible melting-crystallization of the polymer chains in the phase changing BSEP contributes to the stiffness change within a narrow temperature range. A modulus change of more than 1000 folds can be achieved within 3 °C. Additionally, large actuation strains rivaling those of VHB acrylic elastomers can be obtained at the rubbery state. Explorations regarding potential applications of this material have been focused on tactile displays. In one design, Joule heating of a serpentine-shaped compliant electrode coated on a BSEP film, coupled with a pneumatic pressure source has been employed to raise diaphragm dots with 1.5 mm base diameter to heights up to 0.7 mm. The resulting Braille electronic readers could thus be actuated with low voltages.

Recent research work has shown that dielectric fluids, with specific properties, can be combined with stretchable or flexible shell structures, made of polymeric dielectric/electrode composite films, to implement a novel type of soft electrically-driven fluidic transducers with self-healing and self-sensing capabilities that take the name of Liquid based Electro-Active Polymer transducers (LEAPs). These devices are similar to dielectric elastomer transducers in regards to their electrostatic working principle, but they can potentially produce larger displacements due to their lower mechanical stiffness. In this contribution, we present a new transducer concept in which LEAP actuators are employed to induce out-ofplane deformation of a membrane. Specifically, experimental and theoretical demonstrations are provided for applications as dot actuator for Braille displays or other tactile feedback implementations. Results obtained on a preliminary prototype show that the system is able to provide a perceivable force for a human fingertip, offering potential room for further improvement and optimization. Electrically-induced cyclic actuation can be produced over a wide range of frequencies. The results presented in this paper prove the applicability of the LEAP principle on tactile devices and show new design paradigms for this technology.

We present an approach for evaluating the design of Dielectric Elastomer (DE) capacitive pressure sensors on robotic graspers. This approach has used the ANSYS software for Finite Element Method (FEM), along with a MatLab script for calculation of capacitance change. The model has been set up with an axisymmetric indenter and frictionless contact. This study has compared several structured dielectric elastomer (DE) pressure sensors with different sub-surface soft padding thicknesses. The results suggest that: -For padding that is too thin the contact area will be small with localized compression and sensor sensitivity will be compromised by this; -For padding that is very thick compared with the sensor thickness –deformation will be spread over a wider area and the signal sensitivity will be somewhat lower; for a given indenter radius of curvature; -This suggests that there will be an optimal padding thickness for a given contact geometry. The approach developed and presented in the paper will be helpful for sensor soft sensor design for different applications, such as robotics and bio-instrumentational systems, in particular, the design of graspers to identify and pick up different objects.

The suitability for loudspeakers was already demonstrated at the beginning of the development of dielectric elastomer transducers. In contrast to the commonly used electrodynamic principle, which comes along with a variety of components like coils, magnets, springs and a complex system design, dielectric speaker can merely consist of a single membrane. Due to their inherent compliance, only electrodes are necessary to build a loudspeaker. Nevertheless, because of their non-linear actuation behaviour and high driving voltages they were no longer considered in research or commercial applications. Through further development of dielectric films, driving electronics for high voltages and specialized non-linear filters for equalization, these issues can now be addressed. Therefore, we propose new designs of flat dielectric speakers with modular size and adaptable shapes. Total sound pressure levels up to 120 db at 1 m distance, 12.4 kHz transmission range and total harmonic distortions lower than 2 % could be achieved by digital signal processing.

Catheters are commonly used in many medical procedures. These catheters require a high skill to navigate through human blood vessels and also require the use of an X-ray machine to guide the user. Active catheters have been fabricated and studied to increase the dexterity of the catheter, making the catheter much easier to use. Ionic polymer-metal composites (IPMCs) have been studied for this application. IPMCs exhibit large deformations under relatively small voltages (<5 V) making IPMCs excellent candidates for this application. One disadvantage of IPMCs is low stiffness, making the tip of the catheter hard to control in a blood stream. Hydraulic powered active catheters have also been studied. These hydraulically powered active catheters offer higher stiffness but are difficult to control. This research aims to combine these two actuation types into a single hybrid actuator. This will potentially create an active catheter capable of precise complex motion that is safe for human use.

An ionic redox transistor is an ionic device in which ion transport from source to drain is regulated by the electrochemical redox state of the membrane between source and drain. The electrical signal required to switch the device between reduced and oxidized state is applied directly at the gate port that is connected directly to the membrane. In our prior demonstration, we had demonstrated that polypyrrole doped with dodecylbenzenesulfonate [PPy(DBS)] formed over a pore demonstrated a maximum conductance of 30μS/cm and a current gain of 60X as the polymer switches between oxidized (Vm>‐200mV) and reduced state (Vm<‐600mV). The PPy(DBS), PPy(TFSI) and PPy(PF6) membranes are formed on various porous substrates relevant for energy storage (CelgardTM, carbon paper and microporous carbon filter). These membranes are assembled into a custom-made Sawgelok cell with Lithium, lithiated graphite or potassium metal electrodes as required for the energy storage device. Transmembrane ion transport is characterized using HEKA ELP3 SF+SECM hardware and we demonstrate controlled ion transport across suspended PPy(DBS) for various thicknesses, cation concentrations, Vm and VAC. Thickness of PPy(DBS) formed over the porous substrate is varied by controlling areal charge density (AE = 0.05 ‐ 1.5 C/cm2) during potentiostatic electropolymerization. For thickness (AE > 0.15 C/cm2), it is observed from SEM images that PPy(DBS) spans the pores underneath and forms a physical barrier for ion transport across the porous substrate. The experimental setup to investigate ion transport across the membrane. The ionic circuit was set up using the membrane as septum and transmembrane currents were recorded for reduced and oxidized states of the PPy(DBS). The cyclic voltammogram (CV) of PPy(DBS) (areal density of 0.3 C/cm2) in various concentrations of Li+ or K+ ions. The CV appears as expected, with the reduction potential shifting to the right and the peak reduction current increasing with concentration. A typical temporal response of transmembrane current (IAC [mA/cm2]) at different redox potentials (Vm = ‐0.4V to ‐0.9V) and periodic VAC (±100mV). In this figure, it is observed that transmembrane currents are negligibly small (IAC ≈ 0) till the onset of reduction (Vm > ‐0.5V) and the membrane is in the OFF state. As the applied membrane potential is decreased beyond the onset of reduction (Vm < ‐0.5V), the transmembrane current (IAC) begins to increase. As the membrane potential decreases beyond the reduction peak (Vm < ‐0.8V), the transmembrane current reaches a steady state, indicating that it is in the ON state. We define a new metric, amplification factor (ß), to capture the increase in transmembrane current (IAC) as the membrane switches between fully ON and fully OFF states. The amplification factor as a function of Li+ concentration is calculated. At smaller concentrations, below 200mM, the amplification factor is relatively small, and it has a linear dependence between 200mM and 1000mM. At lower Li+ concentrations, smaller number of charge carriers in the electrolyte and comparable size of Li+ ion to porous pathways in PPy(DBS) results in a smaller amplification factor. In this article, we compare the functionality of an ionic redox transistor in organic electrolytes and its application as a smart membrane separator in various energy storage devices (Lithium ion batteries, metal-air battery and super capacitors). We show that the polarity of the device changes due to the electrolyte and hence affects the control strategy required for regulating power output in energy storage devices that uses organic electrolytes.

Ionic Polymer-Metal Composites (IPMC) have various applications in the fields of soft robotics as actuators [1], energy conversion as ion exchange membrane in Fuel cells [2], Biomedical engineering for drug delivery [3] etc. Nafion ionomer plated with a noble metal (such as platinum) is being used successfully as actuators for soft robotic applications [1,4] and recently Aquivion [5] has been explored and proven to be a good candidate to replace Nafion. As ion exchange membrane in Fuel cells, a stable sulfonated silica-based ionomer has been proposed as a replacement for Nafion, which has a dual function as this material has shown to have a higher active surface area of platinum and have increased the performance of fuel cells. These membranes have shown stable performance with improved water management capabilities at low relative humidity, while Nafion based membranes have performed poorly. [6] With this inspiration and the aforementioned advantages we propose to study and investigate the application of sulfonated silica-based membrane to prepare IPMC actuators for soft robots. Based on the positive results these IPMC’s have provided for fuel cell performance, we expect encouraging results for actuation such as higher actuation forces, durability, higher water retainment etc. which would benefit and promote soft robotics. [1,6] References: 1. James D. Carrico, Tom Tyler & Kam K. Leang (2017) A comprehensive review of select smart polymeric and gel actuators for soft mechatronics and robotics applications: fundamentals, freeform fabrication, and motion control, International Journal of Smart and Nano Materials, 8:4, 144-213, DOI: https://doi.org/10.1080/19475411.2018.1438534. 2. Tao Luo, Said Abdu & Matthias Wessling (2018) Selectivity of ion exchange membranes: A review, Journal of Membrane Science 555, 429–454. https://doi.org/10.1016/j.memsci.2018.03.051 3. Saneei Mousavi, M., Karami, A., Ghasemnejad, M., Kolahdouz, M., Manteghi, F., & Ataei, F. (2018). Design of a remote-control drug delivery implantable chip for cancer local on demand therapy using ionic polymer metal composite actuator. Journal of the Mechanical Behavior of Biomedical Materials., 86, 250-256. DOI: https://doi.org/10.1016/j.jmbbm.2018.06.034. 4. Mohsen Shahinpoor and Kwang J Kim (2001) Ionic polymer-metal composites: I. Fundamentals, Smart Materials and Structures, volume 10, number 4, 819-833. http://stacks.iop.org/0964-1726/10/i=4/a=327. 5. Sarah Trabia and Zakai Olsen and Kwang J Kim (2017) Searching for a new ionomer for 3D printable ionic polymer–metal composites: Aquivion as a candidate, Smart Materials and Structures, volume 26, number 11, 115029, DOI: https://doi.org/10.1088/1361-665X/aa919f. 6. Reza Alipour Moghadam Esfahani, Holly M. Fruehwald, Foroughazam Afsahi, E. Bradley Easton (2018) Enhancing fuel cell catalyst layer stability using a dual-function sulfonated silica-based ionomer, Applied Catalysis B: Environmental, Volume 232, 314-321, DOI: https://doi.org/10.1016/j.apcatb.2018.03.080.

We present a method for the patterning of compliant electrodes for dielectric elastomer actuators (DEA) using drop-on-demand (DoD) printing and a lift-off process. DoD is a very appealing method for the patterning of electrodes, due to its high resolution, and the design versatility brought by printing from computer files. However, it has very narrow requirements regarding the viscosity, surface tension, and agglomeration size of the solution to be printed, and a new jetting waveform must be developed for each ink. This makes experimenting with new compliant electrode formulations difficult and time-consuming. Our approach consists in printing a watersoluble sacrificial layer on the elastomer, which serves as a mask selectively protecting portions of the membrane. Compliant electrodes can then be applied on the mask by different means (brush, spray coating, stamping etc.), and the mask can subsequently be dissolved to wash away the excess of ink and reveal the pattern, similar to a lift-off process. The inkjet printing process must only be developed and optimized for a single solution (the sacrificial layer), whereas many different electrodes formulations can then rapidly be patterned and tested, without having to meet the requirements of the printer regarding viscosity, surface tension or agglomeration size. We demonstrate the method by patterning an Polyvinylpyrrolidone (PVP) mask. We then use an airbrush to apply a carbon black/silicone mixture over the whole membrane. Finally, we wash away the mask to reveal the compliant electrodes.

Electro-active polymers (EAPs) such as P(VDF-TrFE-CTFE) was demonstrated to be greatly promising in the field of flexible sensors and actuators[1]. The advantages of using EAPs for smart electrical devices are due to their low cost, elastic properties, low density and ability to be manufactured into various shapes and thicknesses. In earlier years, terpolymer P(VDF-TrFE-CTFE), attracted many researchers due to its relaxor-ferroelectric property that exhibits high electrostriction phenomena[2]. Although their attractiveness, this class of materials still owns the main technological constrain of high electric fields required for their actuation (≥ 30 V/μm, about), which inevitably leads to high level of leakage current and thus short life-time[3]. This paper will demonstrate that an alternative approach is possible. Working on the pure terpolymer P(VDF-TrFE-CTFE) matrix, dedicated electro-thermal treatments are introduced in the film fabrication process in order to limit the conduction mechanisms at high electric fields. Reduction in high-voltage leakage current of 80% are achieved for a wide range of actuation electric fields (up to 90 V/μm), and a 4-fold extension in timeto-breakdown are measured for actuation electric field of 40 V/μm

The novelty of correcting optical mirrors surface in a few microns of the desired precisely-shaped are supported by electroactive polymer actuating/sensing devices. The P(VDF-TrFE-CFE) terpolymer with the 10 % DINP plasticizer has field as EAP which showed 10 times higher in longitudinal strain with respect to the neat one and the increase of total axial strain from 0.4 % - 3.0 % with the multilayer sample 1 to 8 layers respectively. The actuator stack was integrated to the mirror in order to prove the concept of adaptive mirror which is able to reach to goal of a few micron mirror deformation.

The technology of ionic polymer-metal composites (IPMCs) has steadily seen remarkable advancements, but their underlying physics is still elusive. The hypothesis of rigid cross-section is often put forward in IPMC modeling, within structural beam- or plate-like theories. We assess the validity of this hypothesis through the two-dimensional study of multiaxial deformation, based on a thermodynamically-consistent model of IPMC actuation. Our analytical solution is validated through finite element simulations via user-defined elements in Abaqus. Our work demonstrates a rich and complex strain deformation pattern along with a counterintuitive dependence on the Poisson’s ratio.

Dielectric elastomer actuator (DEA) is one of the most promising group of electroactive polymers (EAP) that can find its applications in scientific, medical, industrial and other fields. By geometrically modifying DEA structure, helical dielectric elastomer actuator (HDEA) possesses several advantages due to the continuities of its electrodes and elastomers. The actuator is well known for its competitive electro-mechanical properties and capability to deform significantly in the first place. However, some applications of EAP require relatively high actuation force along with moderate to high deformation capability for a minimum voltage applied. For this purpose, an optimization on the actuator is carried out to maximize the actuation force while keeping the deformation capability on an appropriate level for a particular application. Numerical simulation on a single HDEA actuator is performed to validate the analytical model used in the optimization and to evaluate the performance of the actuator. In both analytical and numerical analyzes, elastomer and electrode layers of HDEA are modeled using a hyperelastic model with the material suitable for 3D printing manufacturing technology. The results of the simulation and analytical solution are compared and discussed. The necessary changes to the hyperelastic model are discussed. In addition, an adaptive soft active composite (SAC) trailing edge of a wing is chosen as a target application in the optimization procedure. Thus, actuator parameters are optimized not only for the single actuator, but also for the adaptive SAC trailing edge with its own dimensional constraints, certain actuation force, deformation, and voltage requirements. The obtained designs will be used in further studies on HDEA-based SAC adaptive structures.