This PDF file contains the front matter associated with SPIE Proceedings Volume 11587, including the Title Page, Copyright information, and Table of Contents.

An engineering contradiction exists between enduring and adaptable robots—we have examples of autonomous cars that can drive for 100’s of miles, or legged ones that can do backflips for a little while, but never the twain shall meet. Pushing this Pareto frontier outwards towards biological capabilities of enduring and adaptive mobility will probably require embracing complexity and multifunctionality. Meaning, hierarchical assembly of several sub-systems (i.e., organs) and packing energy into every cubic centimeter of volume. Towards this end, I will talk about our work to “innervate” robots for tactile feedback using stretchable sensing “skins” for high density shape sensing measurements to improve control authority in high degree of freedom (passive or active) continuum structures and actuators. My focus will be on the use of stretchable fiberoptic lightguides as a sensing medium for estimating deformation and temperature in the “meat” of these compliant structures and actuators. After discussing sensing, I will then describe our concept of “Robot Blood” in order to increase the overall energy density of hydraulically powered robots. This Robot Blood is an electrolyte based off of redox flow battery (RFB) chemistry that performs the additional function of force transmission and soft actuator inflation. I will close by demonstrating robots that take advantage of this electrohydraulic power

Electrohydraulic HASEL (hydraulically amplified, self-healing, electrostatic) actuators are a versatile class of soft actuators that feature large strains, fast actuation, and high power densities. Using the Peano-HASEL actuator as a model system, this work investigates the dynamic behavior of HASEL actuators experimentally and theoretically. A dimensional analysis identifies two different dynamic regimes in which single characteristic time scales govern the speed of actuation: a viscous and an inertial regime. Based on a numeric model for the dynamic behavior of Peano-HASEL actuators we provide guidelines for the design of fast HASEL actuators.

Planar electrohydraulic HASEL (hydraulically amplified, self-healing, electrostatic) actuators are soft actuators which display large linear strains and actuation stresses, as well as high specific energies and specific powers. We use the energy minimization approach to derive a nonlinear quasistatic model to describe the actuation behavior of planar HASEL actuators. In the model, we consider the large strains in the shell due to the Maxwell stress, large deflections of the actuator from the electrostatic zipping, and the hydraulic coupling due to the liquid. We apply the model to both linear planar and circular planar HASEL actuators and compare the results with experimental data

Current and prominent actuation systems used today are limited due to a number of factors including a lack of mechanical flexibility, large system mechanisms, and the inability to integrate safely with biological systems. However, in the novel field of soft robotics, there is a unique liquid-based electroactive polymer actuator (EAP actuator) called the HASEL actuator, that can satisfy these limitations. The HASEL actuator is a versatile actuator, utilizing compliant materials in conjunction with the principles of electrostatic and hydraulic actuation. This study aims to build a model to better understand the system and further explore the versatility of the actuator in practical applications.

When a substrate-bonded silicone dielectric elastomer (DE) is subjected to high voltage, creasing, wrinkling, and cratering instabilities can be formed at the surface of the DE. This deformation, has been already demonstrated for the prevention and detachment of biofouling from the surface of DEs. In this work we add sensing capabilities to the anti-biofouling effect of active DE surfaces. The capacitance of the sensor is measured as a function of applied voltage, and the threshold voltage at which instabilities occur is identified. The formation of instabilities increases the capacitance of the device. When stiff biofouling material attach to the surface of the silicone, the threshold voltage necessary to develop instabilities on the surface of the silicone will increase and this can be used as a measure of attached species to the surface.

A novel design for dielectric elastomer pressure sensors based on a capacitive measurement principle is introduced. Compared with easily compressible and highly sensitive dielectric elastomer sensors containing internal voids, the new sensors are compact and suitable for an elevated pressure range up to about 2 MPa. In these sensors, a dielectric elastomer film with several dielectric and electrode layers is covered on both surfaces by plates, which exhibit a pattern of openings. When the sensor film is compressed, the elastomer material can expand into these openings, which reduces the film thickness and increases the capacitance. The dielectric elastomer film consists of a soft silicone with carbon black particles in the electrode layers. With this design, the sensitivity of the pressure sensors in terms of the capacitance increase is enhanced in comparison with reference sensors without openings in the plates and the disturbing hysteresis of the capacitance vs. pressure curves is reduced. With FEM Multiphysics simulations, the capacitance enhancement upon pressure increase and the sensor deformation were calculated and compared with experimental data. In a systematic study, different parameters of the sensor design were varied, in order to evaluate their influence on the sensor performance. The results of this study are presented in the paper.

We report on pneumatic artificial muscles (PAMs), also known as McKibben artificial muscles, that are integrated with a tubular dielectric elastomer sensor (DES). PAMs are usually composed of a rubber tube surrounded by a sleeve. When pressurized, the deformations of the rubber tube are conformed by the sleeve such that the actuator shrinks in the length direction and expands in the radial direction. To precisely control PAMs, a sensor is required to detect the deformations. DES is suitable for this purpose because it is highly compliant and thin, minimizing the influence on the configuration and performance of the actuators. In order to prove the concept, a sensorized PAM is fabricated by adhering a tubular DES onto the outside of the rubber tube, followed by placing the sleeve. A natural rubber tube with an outer diameter of 6 mm is employed. DES is made of an acrylic elastomer (3M, VHB4905) sandwiched between two compliant electrodes (Adhesives Research, ARcare 90366). When injecting air, the surface of the actuator increases therefore the capacitance of DES. This relationship enables the sensing of the actuator length by measuring the change in capacitance. We characterize the actuators in terms of capacitance as a function of the actuator displacement at different applied pressure.

Virtual reality allows users to immerse themselves into an alternate reality. Science fiction books and films, like Ready Player One, have represented the interaction with virtual reality as a body and mind immersion, where the user is able to move freely, interact with objects and feel the surrounding environment like in the real world. Although we are not there yet, advances in technology are bringing us closer to this vision. One of which, is the advancement in dielectric elastomers sensors (DES). By integrating DES into a wetsuit to capture shoulder and elbow motion, we are able to replicate the movement in a virtual reality humanoid avatar. Compared to the elbow motion, which can be modelled as extension and flexion motions, the shoulder joint is much more complex with a greater number of degrees of freedom. In this paper we present a wetsuit with 5 dielectric elastomer sensors that captures the elbow flexion/extension, shoulder flexion/extension, abduction/adduction and rotation with an RMSE of 11.8°, 5.2°, 5.4° and 7.9° respectively.

A flexible array of high-force and high-stroke mm-scale actuators for wearable haptics will be presented. The soft actuators are capable of both of out-of-plane motion and in-plane motion, allowing the user to feel both normal forces and shear forces from the same active bump. Combining features of DEAs and HASEL devices, each actuator consists of an oil-filled cavity made of a metalized polymer perimeter and a central elastomer region. When a voltage is applied to the electrodes, the fluid is rapidly forced into the central region, forming a bump. Each actuator generates forces of up to 300 mN and displacements of up to 500 µm (60% strain), with a response time of under 10 ms. The 5x5 array is low-profile (<1 mm thick), lightweight (90 mg per actuator) and is suitable for integration in a haptic glove, sleeve or bracelet. It can also be used as a dynamic graphical display for blind or visually impaired users.

This demo presents the Electrostatic Bellow Muscle (EBM), a flexible multipurpose actuator that is obtained by stacking multiple bellow-shaped actuation units. EBM takes inspiration from previous work on liquid-gap electrostatic actuators introducing a new architecture. This novel solution makes it possible to implement an actuator that features a flexible/multipurpose applications such as contractile muscle, pump or energy harvester, while maintaining performance that are comparable to those of previously developed actuation systems. Additionally, a very simple manufacturing process makes it possible to scale up force or displacement by arranging in series or in-parallel actuators. Specifically, the demo will show an EBM with cylindrical shape with a diameter of 30 mm and a height sof 14 mm lifting a weight of approximately 300g with a displacement of 6-7mm at different frequencies.

The increasing demand for devices that are deformable, wearable, or implantable has been driving the development of functional materials that are additionally compliant and repeatedly stretchable. I will introduce our recent efforts in developing elastomeric dielectrics, semiconductors, and conductors. The formation of interpenetrating networks and other microstructural control techniques are used to (1) enhance the electromehcanical responses of dielectric elastomers, (2) protect the conductive percolation network of silver nanowires and carbon nanotubes at large-strain deformations, and (3) to impart elastic deformability to semiconductor materials that are otherwise not stretchy. Explorations of devices incorporating these materials will also be presented.

An environment is defined by a set of field values, such as temperature, electro-magnetic field, light intensity, air humidity and air composition. Smart materials, such as hydrogels, are able to react to these kinds of stimuli. The spatial and time development of environmental values is governed by transport equations. Hence the reaction, i.e. actuation or sensing, of the smart material can be described based on the same assumptions. The displacement, here swelling and deswelling, of the material depends on the combination of the environmental parameters. Smart materials are called multi-sensitive, when more than one parameter is purposely used (i) to manipulate the material, i.e. as an actuator or (ii) to measure the quantities, i.e. as a (multi-)sensor. However, the material can also perform (iii) the objective of a logic processing unit in addition to (i) and (ii). In the current work, we present a device that realizes this concept: An automatic window opener that senses environmental parameters (light-level and air temperature) and reacts accordingly. The hydrogel material that is included in the simplistic device simultaneously acts as sensor, logic processing unit and actuator.

In this work, we investigate PVC gels, a material which responds to electric stimuli, for use I as multi-directional bending actuators. PVC gel bending actuators have been studied, however none of these allow for multidirectional control. PVC gels offer many favorable properties in comparison to other electroactive materials, such as the ability to move in air, high displacement, low power requirements, and lower voltage requirements than other electroactive polymers. A bending actuator which can be controlled to bend in multiple directions is fabricated and tested for its mechanical properties. A mathematical model which can predict actuator motion is also presented.

Polyvinyl chloride (PVC) gels have been studied in some detail and exhibit mechanoelectrical transduction properties, making these materials suitable for sensing applications. This study aims to investigate these mechanoelectrical properties through mathematical modeling. A nonlinear gray-box hybrid state space approach can accurately model the mechanoelectrical transduction properties of the PVC gel sensor in both transient and steady state responses. This approach studies multiple nonlinearities in both transient and steady state mechanoelectrical responses such as overshoot variation and signal attenuation. Mechanoelectrical polarity inversion for tensile/compressive loading schemes exhibited in experimental testing is also investigated in the nonlinear model. A simplified linearized model also shows accurate results for the linear region of mechanoelectrical responses in the PVC gel sensors. Further mathematical modeling aims to describe some underlying physics and governing equations of the mechanoelectrical properties of PVC gel sensors.

In the last decade, twisted coiled actuators (TCAs) made from nylon have drawn the attention of the community as an attractive electroactive mechanism mimicking the performance of human muscles, with notably favourable output power densities. The feasibility of the TCA, in terms of performance, size, safety, and scalability has been evaluated in previous studies, but they exhibit substantially non-linear behaviour, thereby requiring a sophisticated control system. Furthermore, it is desired that these actuators are able to rapidly actuate to match biological muscle levels of capability. To this end, the efficacy of a linear physics-based model of TCAs was tested to elucidate the relationship between temperature, force, and displacement in these actuators. The accuracy of this modelling approach is discussed in the context of position control theory using a two-degree- of-freedom proportional-integral-derivative (PID) controller to switch between Joule heating and active cooling with a continuously controlled fan to enhance actuator response time. This model was subsequently employed to simulate the TCA response to heating and cooling in the MATLAB-Simulink® environment while referencing the experimental results reported by Takagi et al. as a benchmark. Results from this investigation indicate a 5% offset error, which is attributed to the non-linear nature of the TCA. Finally, results confirm that TCAs augmented with active cooling exhibit significantly improved cycle times relative to conventionally heat-controlled TCAs.

Supercoiled polymer (SCP) actuators have shown promising applicability as artificial muscles due to their low-cost, high strains (10%+), work density that is more than 100 x that of muscle, and non-hysteretic behavior. Here, we present a lightweight, low-cost, SCP-actuated valve that operates by pinching rubber tubing closed. The valve comprises a 3D printable frame and incorporates a pulley system, which functions to reduce the total linear dimensions of the device. The actuator mechanism is compatible with different tubing diameters and materials and, by nature of its design, is isolated from direct contact with the working fluid. Using 1/4”/6.3 mm inside diameter latex tubing, a flow rate of up to 88 L/h and a holding pressure of over 29.4 kPa are demonstrated. The valve is normally open and takes 10 seconds to close by running a current through the coiled, silver-coated nylon actuator. An empirical model of the system is developed and open-loop control incorporated, which effectively reduced valve activation time by 30%. Further developments are suggested to achieve a faster response and pumping action.

Visual impairments limit a person’s ability to process information such as obstacles, environments, reading and especially multimedia content (e.g., photographs and videos). In this work, we present the design and operating mechanism of Braille PolyPad, a prototype 2D refreshable braille display featuring 4×10 braille cells, enabling the transformation of images to 2D braille information. The Braille Polypad is based on a miniature pump enabled pneumatic actuation of Braille pins. The encoder transformed the pattern information to a heating circuits to trigger the softening of a stiffness variable polymer, allowing for large pneumatic actuation in the softened pin area. The braille pattern can switch on and off in 0.5s each regardless of the number of braille cells and pins, with low operation voltage and low power consumption. The technical features in this work could enable low-cost, large-size matrix refreshable braille displays in compact form factor. Full development of the prototype device is still ongoing, including materials optimization, actuation uniformity, and improvement of user-friendly control interface.

Electronically conducting polymer (ECP) actuators and sensors are ionic EAPs, whose working principle relies on the motion of ions, usually contained in an electrolyte, toward or from the electroactive polymer. We demonstrate here that linear deformation and sensing in open-air are accessible for ionic EAPs if classical trilayer devices are made electromechanically asymmetric by tuning the properties of PEDOT:PSS electrodes according to an electromechanical model. We also present the first results on “dry” ionic conducting membranes based on polymeric ionic liquids. This “dry” electrolyte allows developing ionic EAPs without any liquid component and still presenting large and fast bending deformation

By combining small dielectric elastomer (DE) elements in an array configuration, their simultaneous actuation and sensing capabilities can be exploited to develop flexible and energy efficient cooperative systems. In this paper we present development, modelling, and experimental validation of a flexible DE array system. After discussing the system operating principle, a physics-based lumped parameter model is developed to describe the electro-mechanical interactions among the several DE elements. An experimental investigation is also conducted on a first 1-by-3 DE array prototype, with the aim of studying the influence of the geometric parameters on the spatially coupled system response. The experimental data is then used to validate the developed model.

For the design of a shape changing display, unimorph bending actuators are investigated. To achieve deformations still visible from a distance, the displacements of the envisioned actuator need to be maximized. The designed actuator is made of a multilayered silicone laminate, which is bonded to a passive, inextensible layer made of nylon ”rip-stop” material with low thickness and density but high tensile strength. Applying a voltage induces a maxwell pressure in the active material and causes an area expansion. The passive layer constraints extension and thus forces a curvature of the device. Approximating the geometry with a circular arc, the device is modeled both statically and dynamically. Experiments are conducted by tracking the tip of the actuator with a image processing software. Static deflection angles of 150° are achieved. Evaluating the step response to a 2500 V voltage step, the resonance frequency of 4.3 Hz is obtained. The findings will be used to maximize stroke, while minimizing the driving voltage. Actuators of this kind can also find application in robots, such as for biomimetic wings or fins.

Transducers based on dielectric elastomers (DEs) consist of a polymer as dielectric between two compliant electrodes and can convert electrical into mechanical energy and vice versa. The geometry significantly determines the performance of DEs, which is mainly reflected by the static and dynamic behavior of pressure and strain. The goal of multilayered dielectric elastomer stack-transducers (DETs) is to maximize the force while maintaining a reasonable deflection. To scale the voltage down to 1 kV the thickness of the elastomeric film must be reduced. For this purpose, a roll-to-sheet lamination process has been adopted by modifying an existing process in order to use elastomeric films with a thickness of 20 µ m, applied with electric field strength up to 50 V/ µ m. In a first step, 10 films are laminated in a semi-automated process resulting in submodules. Fully functional submodules are stacked to form a multilayered stack-transducer up to hundreds of thin films. The production process can be divided into 5 partial processes which are described in detail. The goal of each manufacturing step as well as challenges are presented. With this outline, the outcome of the mentioned manufacturing approach of thin film-based multilayered DE stack-transducers is investigated. The roll-to-sheet lamination approach to produce DETs via submodules provides a good basis for further research in this field.

Ionic artificial muscles containing a polymer electrolyte membrane sandwiched between two electrodes have received intensive attention for many applications. Realizing those applications requires these actuators to display excellent performances, which demand advances in electrodes and electrolytes. However, while electrodes have been intensively researched, polymer electrolytes have progressed slowly. Herein, we developed polystyrene-b-poly(4-styrenesulfonate) block copolymer for the actuators, poly(4-styrenesulfonate) for conducting ions and polystyrene for mechanical stability. The corresponding actuators showed improved performances (low voltage of 0.05 V, durability over 14,000 cycles, fast response of 5s), which demonstrate the quality of the polymer and the potential of the actuators for applications.

In spite of the simple fabrication process, Ionic electroactive polymers (iEAP) work based on a very complex actuation mechanism that is originated in the movement of unequally sized ions through the ionic channels inside the polymer membrane. Such a sophisticated mechanism leads to nonlinear behavior of iEAPs while subjected to electric stimulation and makes their response unpredictable. Here we propose a real-time measurement technique for tracing the movement of ions inside the polymer membrane to better estimate the behavior of the iEAPs during actuation. To do so, a highly flexible and porous electrode is needed to be incorporated into the polymer membrane thus it neither blocks the ions’ path nor restricts the mechanical deformation. Using such an electrode one can measure the internal electrical potential of the membrane, during actuation, to monitor the potential alteration caused by the ions’ migration inside the membrane.

In this paper, the electrical response of ionic electro-active polymer (IEAP) based tri-layer micro-actuator al- lowing to consider some phenomena which occur in the micro-actuator behavior is presented. A detailed study on the measured currents during charging and discharging process is analyzed. Electrical charges, time con- stants, capacitance and resistance of the simplified equivalent electrical circuit are investigated. The results have shown that, the micro-actuator exhibits a linear behavior for applied voltage lower than 1 V. Beyond that, non- linearities appear and are related to the discharging process, especially the corresponding electrical resistance which increases in a non-linear way. At this stage, accumulated electrical charges which depend on the previously applied voltage are not totally restored during the discharging process. The results of this study are illustrated with experimental and theoretical results.

Modelling trilayer conducting polymer is still challenging as it exhibits interrelated coupled multiscale and non-linear characteristics. Therefore, this work proposes to review the underlying electro-chemo-mechanical principles in ultrathin PEDOT trilayer ionic conducting polymers based upon internal ion charge transport, conduction phenomena, redox process and elastic deformation. Microscale governing equations are first analyzed and the choice of appropriate assumptions depending of the used material is discussed. Since exact analytical solutions can be so far given only for some limited conditions, numerical solutions are developed to solve the problem. Then simulations in both sensing and actuating are successfully compared with experiments.

Ionic polymer metal composites (IPMCs) are porous electroactive polymers that are characterized by a uniquely complex electrochemomechanical coupling. The literature includes several modeling approaches, many of which do not consider the presence of water or include its potential role only implicitly. Here, we propose a finite deformations model for IPMCs that accounts explicitly for the water motion within a thermodynamically consistent framework. Through finite element simulations, we disentangle the contribution of water dynamics on the physics of IPMCs. Such a model could be extended to include solution non-idealities, whose effects is presently elusive in IPMC actuation.

Ionic polymer metal composites (IPMCs) are electroactive materials that comprise an ionomer core with metal electrodes. In the ionomer, anions are attached to the polymeric backbone, while cations can migrate within the membrane. The application of a potential difference across the electrodes causes macroscopic bending of the material. Despite the availability of many physically-based models to explain IPMC actuation, experimental validation of theoretical predictions remains a challenging task, due to the sensitivity of IPMC electrochemical properties to the electrodes’ microstructure. Contactless actuation of perfluorinated ionomer membranes (with- out plated electrodes) offers a unique possibility to experiment with these materials, at a smaller variability. Previous experiments showed that, under the effect of an external electric field, ionomer membranes in salt solution deflect toward the cathode. However, the physical underpinnings of their actuation remain unclear. Previously, we have studied the role of the voltage level, salt concentration, and membrane width on membrane deflection. Here, we experimentally explore the effect of the size of the cations in the solution and membrane on the actuation of ionomer membranes. By increasing the size of cations in the solution, we observe a significant reduction of membrane deflection. Surprisingly, for combinations of large cations in both the solution and mem- brane, membranes deflect toward the anode. By increasing membrane cations’ size, we find larger deflections for smaller cations in the solution and smaller deflections for larger cations in the solution. These results can help inform theoretical models to explain actuation of ionomer membranes.

The Organic Mechatronics and Smart Materials Laboratory has previously reported a photosensitive electroactive polypyrrole (PPy) composite resin. The photosensitivity of this resin overcame common issues associated with conjugated polymer device fabrication such that complex 3D structures can now be fabricated via light-based additive manufacturing methods. While this resin formulation enabled the fabrication of previously achievable structures and devices, it also required the introduction of copolymers bisphenol A ethoxylate dimethacrylate and polyethylene glycolmethyl ether methacrylate (BEMA-PEGMA). These copolymers improved the mechanical stability of 3D structures with a concomitant trade-off with the electroactive properties of the composite. This study investigates the introduction of PPy coated carbon nanotubes (CNTs) to improve the electrical and electrochemical properties of the composite material. The effect on performance of the composite was investigated by creating stable dispersions of PPy-CNTs at loading factors from 1 9 mg/mL directly into the pyrrole monomer. The electrical conductivity, electroactive response, and suitability for 3D fabrication of the composite has been assessed. 3D transducers fabricated using this new formulation are shown to exhibit feature resolution comparable to the original resin formulation. Finally, the improved electrical conductivity of the material is assessed to enable the post-hoc deposition of PPy microstructures via soft template electropolymerization. In this process, hydrogen gas bubbles are formed on the working electrode of 3-electrode electrochemical cell, and upon subsequent application of a positive potential PPy is polymerized around the bubble templates. The resulting hierarchical PPy microstructures on the vat polymerized composite films are shown to increase surface area and consequently improve electroactive response.

Polypyrrole (PPy) is a biocompatible electroactive polymer that incorporates and releases complex molecules via oxidation/reduction reactions utilized as a drug delivery mechanism. However, an increased ion-doping capacity is required to load a clinically sufficient amount of drug into the polymer. In this study, we set out to increase the surface area of PPy films with defined microstructures using a soft-template electropolymerization method. Cyclic voltammetry was used to polymerise PPy films from the aqueous solution of pyrrole and camphorsulfonic acid. By modifying the conditions of this process and changing the setup of electrodes, features of different shapes and sizes were created. PPy films with and without microstructures were subsequently doped with Fluorescein and Rhodamine 6G, model drug substances. Three pH values (2.0, 7.5, 11.0) were chosen as stimuli for drug delivery studies. Drug release was measured using UV-spectroscopy. PPy films modified with microstructures had a higher absorbance peak of fluoresce after release compared to the flat films due to the addition of surface modifications. The pH activated release mechanism was shown to be successful in both flat and microstructured PPy films. Microstructures deposited on the PPy films contributed to the increase in drug incorporation sites, thus providing higher ion-doping capacity. These results show Localized pH changes of the surrounding environment can trigger drug release from the polymer in vivo, where an increase of acidity/alkalinity accompanies pathological processes.

Ras Labs makes Synthetic Muscle™, which are electroactive polymer (EAP) based materials and actuators that controllably contract and expand at low voltage (1.5 V to 50 V, battery levels), sense pressure (gentle touch to high impact), and attenuate force. Robotic sensing is mainly visual, which is useful up until the point of contact. To understand how an object is being gripped, tactile feedback is needed. By using soft Synthetic Muscle™ based EAP pads as the sensors, immediate feedback was generated at the first point of contact. Because these pads provided a soft, compliant interface, the force applied to the object to be finely controlled. The EAP sensor could also detect a change in pressure location on its surface, making it possible to detect and prevent slippage by then adjusting the grip strength – directional glide provided feedback for the presence of possible slippage to control with a slightly tighter grip, without stutter, due to both the feedback and the softness of the fingertip-like EAP pads themselves. These EAP pads also naturally held the gripped object, improving the gripping quality over rigid grippers without an increase in applied force. EAPs with appropriate coatings and electronics were positioned as pressure sensors in the fingertip regions of robotic grippers. Pressure position and magnitude tests were successful, with sensitivity down to 0.05 N. While we were holding one of our sensors, we noticed what we thought was an electronic artifact, but was the sensor picking up the heartbeat pulse in our fingers. The pressure range is from 0.05 N to about 20 N within the same sensor. The different touch points of the gripper sensed different areas along the length of the sensor, which can show glide and provide feedback to prevent slippage. Synthetic Muscle™ was also retrofitted as actuator systems into off-the-shelf robotic grippers and considered in novel biomimetic gripper designs. Human grasp is gentle yet firm, with tactile touch feedback. The combination of our EAP shape-morphing and sensing features promises the potential for robotic grippers with human hand-like control and tactile sensing. This work is expected to advance robotics, whether it is for agriculture, medical surgery, therapeutic or personal care, or in extreme environments where humans cannot enter, including with contagions that have no cure, as well as for collaborative robotics to allow humans and robots to intuitively work safely and effectively together.

Dielectric elastomers (DEs) can undergo very large spatial deformations in response to an externally applied electrical field, giving them significant potential as soft actuators. High-performance DEs are usually modified by high-permittivity additives, which are used to lower driving voltages. In this study, a novel high-permittivity soft additive (LMS-EIL) was developed via the combination of high-permittivity ionic liquid (IL) and chloropropyl-silicone, enabling good compatibility with the silicone matrix. The relative dielectric permittivity of the novel silicone oil additive was 9×104 times higher at 0.1Hz compared to pristine chloropropyl-silicone oil. High-permittivity silicone elastomers were then achieved via incorporation of this novel IL-grafted chloropropyl-silicone oil. The relative dielectric permittivity of elastomers modified with 10 parts per hundred rubber (phr) LMS-EIL increased from 3.0 (pure film) to 22 at 0.1Hz, while the Young’s modulus decreased steadily with increasing LMS-EIL concentration. A simplified figure of merit (Fom') was used to evaluate actuation performance, and was shown to be 8.1 for the elastomer incorporated with 10 phr LMS-EIL, indicating excellent potential for use as an actuator.

Enabling desirable actuations at low voltages for silicone based dielectric elastomer actuators (DEAs) is challenging. Reducing the thickness and increasing the softness of the silicone film are key approaches for this purpose. In this work, a super-stretchable silicone elastomer was characterized and used as DEA. The prepared elastomer can be stretched uniaxially to 2400% strain, allowing a significant thickness reduction through pre-stretches. Besides, it shows a moderate average elastic modulus of 0.32 MPa even at strains of 1000%-1500%. These properties favor its application in DEAs. Actuation results show that the elastomer was not only actuated to a high strain but also actuated at attractive voltages. Specifically, a 1 mm-thick elastomer with a pre-strain of 200%×200% was actuated 45% in area at 4 kV, and a 0.25 mmthick elastomer film with pre-strain of 600%×600% showed a 3% actuation strain at only 120 V. Considering its easy fabrication and excellent actuation performance at low voltages, the elastomer is promising in the application in DEAs.

Slide-ring elastomers consist of mobile cross-links that can rearrange themselves within the network in contrast to conventional elastomers with fixed junctures. This unique feature affects the macroscopic mechanical properties of the sliding elastomers by imparting a distinct sliding elasticity that is caused by the distribution entropy of the sliding crosslinks. Slide-ring silicone elastomers exhibit two distinct time dependent elastic responses that can be credited to the conformational entropy of the polysiloxane chains and the distribution entropy of the threaded rings. In this work, the transition between rubber elasticity of the silicone chains and the sliding elasticity of the rings has been observed through linear viscoelastic studies. The extensional properties of the elastomers further corroborated the presence of two distinct time dependent viscoelastic profiles. This novel network structure presents the potential to design more intricate dielectric elastomer transducers with two distinctive modes of behavior determined by the operational speed of the system.

In healthcare products the proper fit of e.g. orthosis is crucial for its therapeutic success. To monitor movement and pressure, sensors with the ability to adapt their shape to the curvilinear form of the human body as well as a highly dynamic performance during motion are needed. Dielectric elastomer sensors (DES) present most of the required specifications and can be an excellent solution for body-near motion detection. For signal capturing either changes in resistance, capacitance or impedance can be measured. Therefore, different circuit configurations can be used that follow different methods e.g. frequency based or an impedance approach. In this paper, an impedance measurement bridge that enables the detection of stretch and pressure loads with a frequency of 200 Hz is modified. The novel architecture is conceptualized to work with a battery based energy supply and have small enough dimensions to function as a wearable with a wireless communication interface. Furthermore, our former presented additive manufacturing method for dielectric elastomers via aerosol jet printing allows an integrated tuning of the measurement bridge in the process. In addition, to the electrodes of the capacitor one electrode with a defined layer resistance is stacked on top of the DES. Hence, the additional electrode, which makes the architecture scalable for different sensor sizes and shapes, serves as an integrated adjustment of the measurement bridge. The data acquisition of multiple sensors is feasible by time division multiplexing, but is limited in its frequency due to the switching rate of the multiplexer.

It is well know that ZnO based polymer composite attract enormous research interests, especially in applications of sensor/actuator devices as well as energy harvesting systems. In this study, a PDMS polymer filled with ZnO microparticles were synthesized and its piezoelectric behavior was observed while varying the ZnO concentration, the dielectrophoretic alignment process, and the poling condition. A real-time observation of particles movement under an alternating (AC) field was achieved in non-cured composites through a digital microscopy. Several processing parameters including amplitude and frequency of the applied electric field was investigated to determine the best configuration of dielectrophoretic manipulation. Simulation and experiment results revealed that the alignment process of the particles improved the poling effect caused by the directionality of the network structures. Owing to the high ZnO/ZnO connectivity, the aligned composites give raise to significantly enhanced dielectric and piezoelectric properties with respect to those randomly dispersed. The dielectric permittivity and piezoelectric response of composites increase with an increasing ZnO volume fraction as well. Finally, a 2D finite element model (FEM) was developed to predict the dielectric constant and the piezoelectric coefficient of the ZnO material. Simulation was in good agreement with the experiment results, confirming that a well-designed network structure of the composite would be a viable approach to improve the piezoelectric performance.

Dielectric elastomer actuators (DEAs) are usually operated at high voltage to induce sufficient electric pressure between two compliant electrodes sandwiching the dielectric elastomer. However, a harsh environment (e.g. humid environment combined with high voltage) often induces electrical breakdown (EB) of the DEAs, which results in pinhole formation or even tearing of the device, followed by macroscopic failure. Therefore, it is ideal for DEAs to be self-healing to extend robustness and lifetime, such as observed for biological muscles, which can be healed from injuries by inherent biological processes. Herein, we prepared a soft (Young’s modulus: 187 kPa) polydimethylsiloxane (PDMS) thermoplastic elastomer (TPE) to demonstrate an autonomous self-healing ability. The system exploits hydrogen bonding (H-bonding) in two types of transient cross-linkers: urea group serves as a sacrificial bond under loading and ureidopyrimidone (UPy) serves as a strong, load-carrying crosslinker. The PDMS TPE shows a crossover of the elastic moduli at 119 °C and highly frequency dependent elastic modulus. The DEA is prepared with compliant, corrugated silver electrodes on both sides of a corrugated PDMS TPE film. A maximum actuation strain (6.8 % in longitudinal direction) is achieved at 18.8 V μm-1. A further increase in potential does not increase the actuation strain, but EBs are observed on the electrodes and the actuation is maintained without any detrimental effects to the film despite the previous breakdown. The EBs do not form permanent pinholes, nor do they cause tearing of films. Instead, only the removal of the silver electrode is observed, which is the so-called self-clearing effect commonly observed for metallic electrodes. In combination with the self-clearing effect, the heat generated by the EBs allows the PDMS TPE to soften. The polymer molecules are then capable of flowing into the voids that were created at the initiation of the EBs. As a result, further propagation of the EB is hindered, and instead, an instantaneous and autonomous self-healing of the DEA is observed.

Silicone is used in the space industry for protecting underlying materials from atomic oxygen. This oxygen reacts with the silicone to form silicon dioxide, which is highly resistant to further attack. Our work is focussed on exploring the use of dielectric elastomer transducers (DETs) in the space sector. These devices often use silicone as their key elastomeric component, if a DET becomes oxidised its motion is at least severely impaired if not completely halted. We have developed a solution to this problem in the form of a protective coating. We present here results of ground-based testing testing of the coating.

We report an experimental investigation of the lifetime of dielectric elastomer actuators (DEAs) under constant DC actuation, with a characterization setup which allows the monitoring of strain and resistance over time for 6 DEAs in parallel. We show how the choice of the electrode influences the lifetime of silicone-based DEAs under constant DC actuation and under different environmental conditions. The DEAs consist of a 12 μm thick prestretched Elastosil 2030 silicone membrane sandwiched between 1 - 4 μm thick and 5 mm diameter circular electrodes. Three types of electrodes are used: 1) pad-printed carbon powder - PDMS composite, 2) inkjet-printed carbon black suspension, and 3) carbon black powder. The DEAs are operated under a constant DC electric field in controlled temperature and humidity, ranging from 30% RH at 20°C to 85% RH at 85°C. 6 DEAs were tested simultaneously for each experimental condition (electrode type, % RH, T). Operated at an electric field of 90 V/μm, at 85°C and at 85% RH, DEAs with pad-printed electrodes show more than 10x higher lifetimes than DEAs with inkjet-printed electrodes. However, no significant difference in lifetime is seen at dry conditions. When operating at electric fields chosen to have the same actuation strain for the different DEAs, those with dry carbon black electrodes show over 5x higher lifetimes compared to DEAs with pad-printed or inkjet-printed DEAs, owing to the lower operational electric field required (50 V/μm vs. 90 V/μm) to reach a given strain. At 85°C, increasing the humidity from 20% RH to 85% RH leads to a 40x to 400x decrease in lifetime for DEAs with pad-printed and with inkjet-printed DEAs.

For dielectric elastomer actuators (DEAs) to find more widespread adoption in commercial products, a better understanding of their durability is needed. By determining the different mechanisms contributing to ageing and breakdown in DEAs, new methods for improving their lifetime could be devised. Using a newly-developed setup for performance and lifetime evaluation of DEAs, we investigate how the choice of electrode material and application process influence lifetime. Our investigation is focused on DEAs made from a slide ring material (SRM) as the dielectric. SRM is an interesting candidate for DEAs as it offers a much higher permittivity (εr < 7) than commonly used silicone rubbers. However, the log-term durability of SRM DEAs, and how it is influenced by external factors such as the type of electrode material, has not yet been thoroughly studied. We tested SRM DEAs made with various carbon-based electrode materials, different application methods including blade casting, inkjet- and pad-printing, and ink formulations with different solvents. Average lifetime of the DEAs at 50 Hz and 40 V/μm varied from under 1 h (160,000 cycles) to over 100 h (16,000,000 cycles) between the different electrode types. Our experiments show that not only the type of material but also the thickness and topology of the electrode layer can greatly influence lifetime. We observed that some solvents such as isopropyl alcohol cause swelling and wrinkling of the SRM membrane, but that this has no negative impact on lifetime. We propose that high electrode resistance can improve lifetime by limiting current and reducing the damage from heating, arcing, or partial discharge. This effect can also be achieved by addition of an external resistor. Our results suggest that charge and discharge current of DEAs should always be limited to the very minimum needed for the intended application in order to reduce degradation.

Conducting polymers have interested many research groups as they exhibit a large strain in response to electrical stimulation, which is promising for materials used in MEMS. To date, these micro-actuators have very often been characterized by applying an AC voltage to extract the produced strains and forces. However, many applications require subjecting the actuators to an electrical voltage threshold for about 10 seconds or until several minutes. A micro-camera tracking the displacements of an object, the actuation of a cochlear implant during surgery, or the closing of micro-tweezers for manipulation objects are potential applications for which actuation is achieved by applying a DC voltage. In this way, the kinetics to reach the maximum strain are identified and compared. The application of a DC voltage to the conducting polymer-based micro-actuator for an extended period of time results in the emergence of a “memory effect”. In particular, the actuator does not return to its initial position promptly after a short-circuit. In addition, the electromechanical measurements conducted show that the deformation obtained depends on the DC voltage used for the previous actuation. The memory effect is directly related to the intrinsic operation of micro-actuator trilayers where the separator (NBR/PEO) is filled with an ionic liquid electrolyte that is involved during oxidation and reduction of the conductive polymer electrodes (PEDOT:PSS/PEO). An explanation of the physico-chemical phenomena involved will be proposed. These results are needful for the modeling and future control of these conjugated polymer micro-actuators integrated into microsystems devices for real-life applications.

We developed an ionic electroactive polymer-based actuator integrating a Nafion and carbon nanotube (CNT) composite electrode material. The electrodes are composed of high-density, closely packed arrays of vertically-aligned CNTs on a current collector and are oriented perpendicularly to the plane of the membrane. The CNTs act as high-surface-area scaffolding for the impregnated Nafion ionomer layer. The increased electroactive area improves the force generation and provides a similar degree of bending deformation to neat Nafion actuators. An ionic liquid electrolyte (1-ethyl-3- methylimidazolium tetrafluoroborate) was incorporated to further enhance the actuation and force. The CNT composite actuators produced between two and ten times the force compared to commercially available materials. The degree of deformation was comparable to neat Nafion actuators. The actuators consumed approximately 500 μA at 4 VDC, a power draw of 2 mW.

Electroactive polymers have great potential for many real-world applications, from soft robots and implantable devices to smart coatings for buildings and deployable structures in space. Unfortunately, the fundamental physics of EAPs lends them to operation at much smaller scales. The challenge therefore is to scale up the smart behaviour of EAPs (in sensing, actuation and energy harvesting) from the nano- and micro-scales to human scale and beyond. In this presentation we will explore the motivation for, and difficulty of, EAP scale-up and examine practical routes to achieving it. These will include the integration of micro-actuation across spatial and temporal domains. We will also take inspiration from biological mechanisms which are so good at achieving this scale-up through efficient materials selection and structural design. Examples we will consider include biological skeletal muscle activation, zipping electro-origami and crawling electro-skins. We will address the elephant-in-the-room of multi-scale hierarchical fabrication and propose potential solutions through smart metamaterials and self-assembly. If these challenges can be met, the true potential impact of EAPs could be realised within a decade.

In recent years, dielectric elastomers (DEs) have found novel applications in the field of soft robotics, where compliant and compact actuators with high energy densities are needed. Rolled DEs can be effectively used to achieve muscle-like actuators for soft robots, eliminating the need for external motors while providing at the same time a lightweight structure with self-sensing capabilities. In this paper, we propose a large deformation, energy-based model for rolled DEs which permits to describe the actuator behavior in a lumped-parameter fashion. The model is intended for control and self-sensing applications. After presenting the model equations, a parameter identification is performed and discussed based on experimental data.

This paper presents a cost-efficient HV amplifier suitable for driving capacitive loads such as dielectric elastomer (DE) loudspeakers within a typically used bandwidth for audio applications. First, the unique challenges, especially considering voltage range, dynamics, and distortion posed on electronics driving DE loudspeakers, are examined. Subsequently, the suitability of different types of output stages for the intended purpose is discussed. The developed topology capable of driving capacitive loads at high voltages is then introduced. Its significant advantages are the small number of expensive high-voltage (HV) semiconductors, its high bandwidth and linearity at a low quiescent current. The authors analytically examine the amplifier’s operation and discuss the selection as well as the dimensioning of different key components. The driver stage contains a cascaded voltage-current-control loop realized with operational amplifiers, ensuring the power stage HV semiconductors’ appropriate driving. Tuning the control loop to the intended behavior is achieved with the method of pole placement. Thereby, the closed-loop control guarantees excellent command response from DC to 20 kHz and good disturbance suppression. Using a prototype with a maximum output voltage of 2500 V and a maximum output current of ±20 mA, the converter’s behavior is experimentally examined. Measurements focusing on frequency response, output power, and the total harmonic distortion show the topology’s excellent HV and audio characteristics. After presenting the prototype’s cost distribution, the authors finally discuss the proposed topology’s suitability for driving DE loudspeakers and other possible use cases.

This paper presents a multi-physics model of an electrostatic loudspeaker system that combines the acoustic diaphragm and the actuator into a lightweight dielectric elastomer (DE) membrane. The focus is set on the so-called cone-shaped DE actuator (DEA) topology, which features a self-standing compact architecture, free from pneumatic loading systems, and is potentially suitable for integration onto complex surfaces and structures. We propose an axial-symmetrical lumped-parameter nonlinear model of the cone DEA structural dynamics, and use it to predict the acoustic pressure field generated by the speaker. We then present a case study in which the model is used to predict the linearised mode shapes of a reference DEA, evaluate their effect on the acoustic frequency response, and compare the harmonic distortions resulting from different driving strategies.

Robotic systems based on tensegrity structures have been widely studied in recent years due to their unique characteristics such as lightweight property, deformability, and modularity. These features are originated from the structural configuration of tensegrity that consists of rigid rods connected and stabilized by pre-stretched elastic cables. However, most of the tensegrity robotic systems are driven by electromagnetic motors, which can make their structure bulky and complicated. In this contribution, we present tensegrity structures using dielectric elastomer actuators (DEAs). In these active tensegrity structures, DEAs are used as the elastic cables, allowing them to generate voltage-controlled deformations. Thanks to the multifunctional nature of DEAs, this configuration also enables the sensing of deformations. Given the large actuation strokes and high compliance of DEAs, the DE-tensegrity is expected to become a multifunctional building element for soft robotic systems. In order to prove the concept, we fabricate a DE-tensegrity using an acrylic elastomer (3M, VHB4905) and acrylic (poly(methyl methacrylate)(PMMA)) plate that are used for DEAs and the rigid rods, respectively. A conductive acrylic elastomer is used as the electrodes of DEAs. We characterize the active tensegrity to clarify the actuation and sensing performance and discuss the results.

Actuators driven by electrostatic force represent a very promising opportunity for the development of advanced robotic systems. Dielectric elastomer actuators have been long investigated and more recently devices based on fluid dielectric have been proposed as a possible alternative that shows remarkable performance. Here, we present a novel electrostatic actuator that is made of thin polyimide films and liquid dielectric, combined with rigid plates assembled to form a circular actuation unit that undergoes to out-of-plane expansion/contraction. Prototypes of these actuation units have been tested showing a contraction of up to 40%, a maximum power density during contraction of 100 W/kg, a maximum strain rate of 1000% per second, a bandwidth of approximately 10 Hz, and the ability to lift hundreds of times their weight. Additionally, these units resulted easy to manufacture in different dimensions and can be assembled in arrays and stacks to form an electrostatic bellow muscles (EBM) that can be effectively employed as a contractile artificial muscle, as pump and as electrostatic generator. EBM demonstrated their flexibility in matching a wide range of requirements and scales in terms force-displacement combinations and bandwidth. The compact 2-D shape, the low-cost of components, the simple assembling procedure, the high level of reliability and the relevant performance make the EBM a possible enabling technology for a variety of high-performance robotic and mechatronic systems.

Zipping electrostatic actuators operate by bending flexible electrodes using electrostatic forces. This principle allows the use of a wide range of dielectric and conductive materials. Additive Manufacturing (AM) techniques can be used to fabricate these actuators. The selective direct deposition of multiple materials improves the actuator design flexibility, as customized prototypes can be fabricated without masks and moulds. Here we present the first integration of AM techniques in the fabrication process of Hydraulically Amplified Taxels (HAXELs), a class of electrostatic actuators combining zipping electrodes deformation with the inflation of a stretchable material using fluidic coupling. We use an inkjet printer (jetlab® 4 by MicroFab) to deposit Polydimethylsiloxane (PDMS) as the stretchable material and Ethyl Cellulose as a sacrificial material for fluidic features patterning. We integrate gold-sputtered, laser-cut Mylar foils for the flexible part of the actuator by encapsulating them between the inkjet-printed layers. After dissolving the sacrificial material, a dielectric fluid can be injected in the fabricated actuators. Qualitative evaluation of a fabricated device is reported, showing electrode zipping. The presented fabrication process allows future fabrication of highly integrated actuators having arbitrary shapes.

The name artificial muscles has given dielectric elastomer actuators much attention in the field of medical technology. In healthcare applications, these compliant materials are particularly suitable for soft and lightweight actuators and in addition, they show many advantageous properties such as great extensibility for on-body sensors. However, the lack of industrial scaled production capabilities is still a limiting factor in the transfer of these promising materials into a broad application. To address this issue, we have modified an aerosol jet printer for automated stacking of electrodes and dielectric layers in one process device, which is described in earlier publications. As the performance is mainly dependent on the electrical and mechanical characteristics of the dielectric, a broad material variety is required to face different tasks in healthcare technology. Therefore, different medical grade silicones are investigated in this paper regarding the suitability for aerosol jet printing. In a first step, the printing parameters are derived from rheological testing of the uncured components that are used pure and in mixture with silicone oils to vary the specific Young’s module. Through heat application and dilution, the range for printable materials increases to silicones with initial viscosities up to 8200 mPas. Subsequently aerosol jet printing is used to manufacture stacked silicone dielectrics that are then investigated regarding their mechanical and electrical characteristics for dielectric elastomers. Finally, the collected parameters are compared and an overview of the feasible property combinations is given which can be used as a material guideline for different applications.

This paper investigates a droplet based dispensing method for the application of compliant electrode layers for Dielectric Elastomer (DE) transducers and presents the characterization of the deposited electrodes. It is a non-contact, robust and in terms of the material requirements versatile method. As electrodes, three different carbon black based materials are prepared for the deposition by adjusting their fluid properties. The working principle of the deposition method is introduced and the deposition parameters are determined. Subsequently, the electrode materials are deposited on the very thin dielectric elastomer film. The electrical and mechanical properties of the deposited electrodes are experimentally characterized. A surface resistance of 4.1 kΩ at 4.5 µm thickness is measured and no significant stiffening is observed up to 20 % elongation. The investigated deposition technique is able to deposit the particle filled electrode materials with a relatively wide viscosity range without contact and a homogeneous thickness of under 5 µm within the deposited area.

A dielectric elastomer transducer (DET) consists of a thin elastomer film and compliant conductive electrodes on each side. By laminating several layers, DE multilayer transducers can be designed, having a great potential in different industrial applications. So far, different manufacturing pro- cesses, such as spin-coating, 3D-printing, roll-to-roll and roll-to sheet processes, have been success- fully developed and applied. Manufacturing processes based on pre-fabricated elastomer material have the advantage, that the dielectric elastomer film is characterized by homogeneous and re- producible properties. Nevertheless, the handling and the tension-free lamination of very thin elastomer films is a challenge. Moreover, the transition of a process from a laboratory to an in- dustrial scale should be considered at the beginning of the process design. This paper presents a new approach of a manufacturing process for high-quality dielectric elastomer laminates which can be processed to DE multilayer transducers. Starting with a pre-fabricated elastomer film, different process steps such as sheet creation, stacking and applying structured electrodes are performed to finally achieve a DE laminate with a high number of layers. A crucial process step, the detachment of the pre-fabricated elastomer film from the liner and the subsequent stacking, is experimentally demonstrated. Based on the presented concept, a laboratory scale setup to carry out the designed process is introduced.

Flexible thin-film Electro-Adhesive Devices (EADs) represent a promising technology with great potential for gripper applications. Generally, the gripping action of an EAD is due to the electrostatic force induced by an electric field produced by applying a voltage across a couple of electrodes that are embedded between dielectric substrates. This paper presents a novel manufacturing process and the experimental characterization of a multilayer electro-adhesive gripper. The proposed device employs highly elastic silicone (PDMS) thin-film as the grasping layer, i.e., the dielectric layer that comes in contact with the grasped object, a carbon-black mixture in a silicone compound for the electrodes, and a rigid polyimide thin-film as the backing layer, i.e., the dielectric layer on the backside of the EAD. A fabrication methodology is illustrated, which starts from a casting of thin conductive electrodes on a polyimide film, followed by a laser-cutting operation to shape the electrodes and a blade casting process to encapsulate the overall system in a PDMS compound. Different prototypes obtained through this manufacturing procedure have been experimentally evaluated through a testing campaign conducted on three groups of specimens, each composed of five identical samples, with a different electrode thickness per group. Samples are tested for electrostatic shear stress and electrical breakdown during the grasping of paper substrates, identifying the best performing EAD group.

A DE capable of the high speed and high output required for driving robots and automobiles is still under study. Chiba et al succeeded in raising and lowering a 4kg weight by about 1mm at a speed of 97msec using a total DE weight of 0.98g last year. The DEA used a VHB4910 and SWCNTs. For the above purposes mentioned above, however, the current weight able to lifted is insufficient. We examined various elastomers (including materials newly developed) and various electrode materials, and we succeeded in lifting a weight of 8 kg quickly. We also considered the potential of this DEA as a drive source for electric vehicles and a potential for power generation from the vehicle’s movement.

Owing to their intrinsic actuation capability and outstanding electromechanical characteristics, dielectric elastomer actuators (DEAs) are promising smart materials with the potential to outperform conventional mechanical and electrical actuation systems for certain engineering applications, such as soft robotics and biomedical engineering. As a single-layer, planar DEA produces only one-dimensional deformation, i.e., contraction-expansion, with a moderate actuation force, different actuation mechanisms, such as rolling or stacking DEAs, have been implemented to obtain larger deformations and higher actuation forces. However, these DEA configurations do not alter the fundamental type of thickness-wise deformation. In some applications, DEA’s out-of-plane actuation motion, such as bending, is often desired for effective system operation. Currently, the desired types of DEA deformation are generally attained by implementing additional members or mechanisms using various means, e.g., stiff frames, unimorph or bimorph, multistable structures, preloaded mechanisms. Although the methods above enable DEAs to achieve desired motions, they can considerably constrain deformation and actuation force and mostly require manual assemblies. This paper demonstrates a novel DEA capable of generating the needed range of motions without introducing additional elements within the actuator. This was accomplished by tailoring the electrode-elastomer pattern and thereby deforming the elastomer in the desired manner. Studied DEA design was first developed using theoretical basics about flat capacitors and then verified through finite element analysis. The designed actuator was additively manufactured using a contact microdispensing 3D printer and tested to validate its bending due to the tailored electric field.

By using a dielectric elastomer (DE) sensor and observing the change in capacitance due to the amount of water, the amount of change in water can be measured more accurately. Further, since it is flexible, it offers excellent wearability as a sensor attached to the body, or is excellent comfort as an unobtrusive sensor attached to a chair. Also, since this sensor does not use metal leads, there is no risk of rust or metal allergies. The principle is simple; the frequency changes due to the change in the capacitance of DE (capacitor), making it is possible to measure moisture by the change. An inexpensive elastomer can be used for the dielectric, and carbon black, CNT, or the like can be used for the stretchable electrode.

The use of piezoelectric thin sensors, when subjected to large static strain levels in ultrasonic applications is reported in this paper. A novel flipped beam bending method is proposed to induce static strain level nearing twice the incipient yield strain in the beam material (~0.39%). First, the effect of static large strain on ultrasonic guided wave propagation in the beam was studied using the velocity measurements obtained from a laser Doppler vibrometer. Next, the ultrasonic response of thin sensors is studied under compressive and tensile static strain (±0.72%) with the sensors symmetrically bonded on the lower and upper surfaces, and at the same axial location. The ultrasonic guided wave response to varying levels of static strain is recorded at different center frequencies (50–400 kHz) of the narrow banded ultrasonic excitation. As a case study, the variation of the ultrasonic guided wave response of polyvinylidene difluoride (PVDF) thin sensors with center frequencies at different static strain levels was analyzed and compared with that of lead zirconate titanate (PZT) thin sensors. PZT sensors show a higher variation of sensing performance with strain when compared to PVDF sensors. Apart from static strain, the possible effects on the change in performance of sensors, such as the change in the capacitance is discussed. The characterization method provides a reusable beam arrangement to study the ultrasonic sensor performance at large static strain levels. Characterization at large strain level allows the development of fail-safe sensors even under large strain and permanent plastic deformation of structure on which they are bonded, allowing accurate ultrasonic structural health monitoring even in the presence of damage progression. Piezopolymer sensor like PVDF are least susceptible to static strain due to large yield strain and low modulus and can serve as fail-safe sensors under large strain.

Dielectric elastomer actuators (DEAs), with the advantages of high energy density, large actuation strain and light weight, have been explored for numerous assistive related applications, including refreshable tactile displays, tunable optics, and bio-mimic robotics. However, their steps to practical applications are limited by the poor reliability and durability, especially under large actuation strain. Here we report a self-clearable compliant electrode comprising an ultra-thin singlewalled carbon nanotube (SWNT) electrode with an overcoated thin polymer layer. This bilayer electrode can provide the acrylic-based DEAs with a long lifetime stably under both cyclic and continuous actuation at 150% actuation strain in area.

Electroactive polymers strain sensors bear a great potentiality in the area of soft robotics, wearable devices, and fitness industries. A small initial defect present in such sensor may grow to a critical size during contraction and relaxation cycles leading to mechanical failure, therefore, prediction of fatigue life is inevitable. The crack growth approach is one of the amicable ways to estimate the fatigue life considering parameters like tear energy, crack geometry, and power law. In this work, crack growth approach based on power law is being proposed to predict fatigue life utilizing conducting and stretchable freestanding films consisted of SEBS rubber and dodecyl benzenesulfonic acid (DBSA) doped polyaniline composite. Utilizing this crack growth model for the prediction of fatigue life exhibited that such films can sustain more than a million cycles even at a large value of deformation.

This paper discusses a simple characterization method for thin stacked dielectric elastomer actuators (DEAs), which is difficult to measure the mechanical impedance. We employ a method of suspension for characterizing the mechanical impedance. A weight is attached to a thin stacked DEA and then the DEA is electrically excited. The frequency response is obtained by measuring the vibration displacement. Consequently, we can estimate the mechanical impedance or viscoelasticity of the thin stacked DEA. From the experimental frequency response of electrical excitation, Young’s modulus and damping ratio were successfully estimated.

A novel concept for sound generation using buckled dielectric (DE) elastomer membranes was proposed recently, which relies on buckling induced by a DC voltage, superimposed by an AC signal voltage to force vibration. To accurately describe the large amplitude vibrations of buckled, viscoelastic structures at frequencies in the audio spectrum, complex theories are required in general. In this work, a compact differential equation is derived, which rests on some simplifications to reduce the complexity of the problem. To assess its validity, several devices of different diameters and thicknesses are experimentally investigated and compared to the model. As expected, the model loses accuracy with increasing relative thickness, which is in line with other studies in the field. For moderately thick plates the stiffness is underestimated due to neglected shear effects. But, for relatively thin membranes the model provides an efficient tool to predict the post-buckling behavior of DE membranes and will help develop lightweight and small loudspeakers.

The superior swimming ability of fish has encouraged the development of fish-like robots. To fully capture fish swimming kinematics a continuum under-actuated robot can be used, and there are many examples of such robots in the literature. But for realistic fish-like swimming in strong currents such robots will benefit from closed-loop feedback. We demonstrate how this can be achieved, underwater, using a stretchy neoprene sensing skin with embedded, discrete dielectric elastomer stretch sensors. The latest prototype skin, with 8 sensors, 4 on each side, is currently being evaluated on an underactuated tensegrity fish-like robot driven by a stepper motor. Carangiform movement of the body has been characterized using cameras and this data has been compared with a virtual model of the robot that uses sensor input for real-time model kinematic data. Four angles along the body defined the shape. A root mean square error between model and true camera angles of less than 3° was calculated for realistic cangiform motion at 0.5 Hz tail frequency.

Polymer computational simulations enable the prediction of material properties, exploration of the microscopic and macroscopic phenomenon of materials, and guidance of in vitro macromolecular materials design. This paper presents a mesoscopic level, multiscale approach to generate a complex polymer morphology for future simulations of polymer chains aimed at the design of materials or the study of material properties, such as strain/stress relations and electromechanical properties. To generate a complex polymer morphology, a mesoscopic level model is developed, in which the polymer chains are modeled as one-dimensional homogeneous flexible chains, and the crystalline regions are modeled as rigid continuum bodies. The polymer domain is firstly discretized into a uniform mesh. Location, orientation, and size of crystalline regions can be either pre-defined or randomly distributed inside the polymer domain. Nodes of each cuboid element grid located within crystal units are marked as occupied. Then, a random walking process is applied to generate polymer chains. No overlap is permitted between polymer chains nor between polymer chains and crystalline regions. Chain propagation ceases upon reaching the crystal block surface. Polymer chain properties, such as longitudinal stiffness, bending stiffness, and torsional stiffness, are derived based on molecular structures. Interactions, those between polymer chains, and those between polymer chains and crystalline regions are derived based on Lennard-Jones forces. An explicit dynamic relaxation algorism is applied to minimize potential energy. This approach is much more efficient than MD simulation. The computing time required for this mesoscopic simulation is only 0.5-1% of MD simulation. Yet, nanoand micro-scale geometries of polymer morphology can still be analyzed in detail. Polyvinylidene difluoride (PVDF) is selected to demonstrate the efficiency and efficacy of this numerical model due to its high piezoelectric coefficient.