Development of dielectric elastomer actuators has been mainly targeted towards achieving giant static strain with little attention paid to their response speed, which can, depending on materials used, be as long as tens of seconds. However, most of the practical applications require actuators capable of changing shape quickly, therefore a careful choice of materials and technologies for the dielectric and electrodes must be made. Test oscillating actuators, made with a range of silicone membranes with different hardness were tested, and the compliant electrodes were made with different technologies: carbon powder, carbon grease, conductive rubber and metal ion implantation. The transient response of the actuators to a step input was measured with a high speed camera at 5000 frames per seconds for the different combinations of membrane material and electrodes. The results show that the dynamic response of the actuators is extremely dependent on the membrane material, as expected, but also on the compliant electrodes, whose impact cannot be neglected.

Conducting polymers such as polypyrrole are well-known for their volume changing capacity and their use as actuating material. Actuators based on polypyrrole have been demonstrated in dimensions ranging from centimetres down to micrometres as well as in linear strain and bending beam actuation modes. The polypyrrole (micro-)actuators can be operated in salt solutions including cell culture media and blood. In addition, polypyrrole is known to be biocompatible making them a good choice for applications within cell biology and medicine. Applications of polypyrrole actuators within micromechanical devices, such as microrobotics and valves, will be presented. Opportunities and devices for the medical device industry, especially vascular surgery will be shown. This includes a rotating PCTA balloon system, a steerable guide wire, and an implantable drug delivery system. In addition, novel mechanostimulation chips for cell biology will be introduced. Using these devices, we can stretch cells and show the cellular response to this mechanical stimulation. Since the dawn of eukaryotic cells many parallel molecular mechanisms that respond to mechanical stimuli have evolved. This technology allows us to begin the investigation of these mechanisms on a single cell level.

Artificial muscles based on dielectric elastomers show enormous promise for a wide range of applications and are slowly moving from the lab to industry. One problem for industrial uptake is the expensive, rigid, heavy and bulky high voltage driver, sensor and control circuitry that artificial muscle devices currently require. One recent development, the Dielectric Elastomer Switch(es) (DES), shows promise for substantially reducing auxiliary circuitry and helping to mature the technology. DES are piezoresistive elements that can be used to form logic, driver, and sensor circuitry. One particularly useful feature of DES is their ability to embed oscillatory behaviour directly into an artificial muscle device. In this paper we will focus on how DES oscillators can break down the barriers to industrial adoption for artificial muscle devices. We have developed an improved artificial muscle ring oscillator and applied it to form a mechanosensitive conveyor. The free running oscillator ran at 4.4 Hz for 1056 cycles before failing due to electrode degradation. With better materials artificial muscle oscillators could open the door to robots with increased power to weight ratios, simple-to-control peristaltic pumps, and commercially viable artificial muscle motors.

Neural probe insertion methods have a direct impact on the longevity of the device in the brain. Initial tissue and vascular damage caused by the probe entering the brain triggers a chronic tissue response that is known to attenuate neural recordings and ultimately encapsulate the probes. Smaller devices have been found to evoke reduced inflammatory response. One way to record from undamaged neural networks may be to position the electrode sites away from the probe. To investigate this approach, we are developing probes with controllably movable electrode projections, which would move outside of the zone that is damaged by the insertion of the larger probe. The objective of this study was to test the capability of conjugated polymer bilayer actuators to actuate neural electrode projections from a probe shank into a transparent brain phantom. Parylene neural probe devices, having five electrode projections with actuating segments and with varying widths (50 - 250 μm) and lengths (200 - 1000 μm) were fabricated. The electroactive polymer polypyrrole (PPy) was used to bend or flatten the projections. The devices were inserted into the brain phantom using an electronic microdrive while simultaneously activating the actuators. Deflections were quantified based on video images. The electrode projections were successfully controlled to either remain flat or to actuate out-of-plane and into the brain phantom during insertion. The projection width had a significant effect on their ability to deflect within the phantom, with thinner probes deflecting but not the wider ones. Thus, small integrated conjugated polymer actuators may enable multiple neuro-experiments and applications not possible before.

The dielectric elastomers are functional materials that have promising potential as actuators with muscle-like mechanical properties due to their inherent compliancy and overall performance: the combination of large deformations, high energy densities and unique sensory capabilities. Consequently, such actuators should be realized to replace the currently available artificial urinary sphincters building dielectric thin film structures that work with several 10 V. The present communication describes the determination of the forces (1 - 10 N) and deformation levels (~10%) necessary for the appropriate operation of the artificial sphincter as well as the response time to master stress incontinence (reaction time less than 0.1 s). Knowing the dimensions of the presently used artificial urinary sphincters, these macroscopic parameters form the basis of the actuator design. Here, we follow the strategy to start from organic thin films maybe even monolayers, which should work with low voltages but only provide small deformations. Actuators out of 10,000 or 100,000 layers will finally provide the necessary force. The suitable choice of elastomer and electrode materials is vital for the success. As the number of incontinent patients is steadily increasing worldwide, it becomes more and more important to reveal the sphincter's function under static and stress conditions to realize artificial urinary sphincters, based on sophisticated, biologically inspired concepts to become nature analogue.

Over the past 4 years SBM has developed a revolutionary Wave Energy Converter (WEC): the S3. Floating under the ocean surface, the S3 amplifies pressure waves similarly to a Ruben's tube. Only made of elastomers, the system is entirely flexible, environmentally friendly and silent. Thanks to a multimodal resonant behavior, the S3 is capable of efficiently harvesting wave energy from a wide range of wave periods, naturally smoothing the irregularities of ocean wave amplitudes and periods. In the S3 system, Electro Active Polymer (EAP) generators are distributed along an elastomeric tube over several wave lengths, they convert wave induced deformations directly into electricity. The output is high voltage multiphase Direct Current with low ripple. Unlike other conventional WECs, the S3 requires no maintenance of moving parts. The conception and operating principle will eventually lead to a reduction of both CAPEX and OPEX. By integrating EAP generators into a small scale S3, SBM achieved a world first: direct conversion of wave energy in electricity with a moored flexible submerged EAP WEC in a wave tank test. Through an extensive testing program on large scale EAP generators, SBM identified challenges in scaling up to a utility grid device. French Government supports the consortium consisting of SBM, IFREMER and ECN in their efforts to deploy a full scale prototype at the SEMREV test center in France at the horizon 2014-2015. SBM will be seeking strategic as well as financial partners to unleash the true potentials of the S3 Standing Wave Tube Electro Active Polymer WEC.

Five key materials engineering components and how each component impacted the working performance of a polymer actuator material are investigated. In our research we investigated the change of actuation performance that occurred with each change we made to the material. We investigated polymer crosslink density, polymer chain length, polymer gelation, type and density of reactive units, as well as the addition of binders to the polymer matrix. All five play a significant role and need to be addressed at the molecular level to optimize a polymer gel for use as a practical actuator material for biomedical and industrial use.

In this paper, we propose a tactile display with a rigid coupling based on Dielectric Elastomer Actuator. The proposed design of the tactile display is explained and its basic operational principles are discussed. It consists of three parts, that is, actuator layer, coupling and upper layer. The rigid coupling is sandwiched between them. Because of the simplicity of the design, the fabrication is extremely easy, that is just to bond the upper layer to the actuator layer after making EAP actuator sheet and upper layer. The device is fabricated with multiply stacked actuators and its effectiveness is validated experimentally.

Rodents are able to dexterously navigate confined and unlit environments by extracting spatial and textural information with their whiskers (or vibrissae). Vibrissal-based active touch is suited to a variety of applications where vision is occluded, such as search-and-rescue operations in collapsed buildings. In this paper, a compact dielectric elastomer vibrissal system (DEVS) is described that mimics the vibrissal follicle-sinus complex (FSC) found in rodents. Like the vibrissal FSC, the DEVS encapsulates all sensitive mechanoreceptors at the root of a passive whisker within an antagonistic muscular system. Typically, rats actively whisk arrays of macro-vibrissae with amplitudes of up to ±25°. It is demonstrated that these properties can be replicated by exploiting the characteristic large actuation strains and passive compliance of dielectric elastomers. A prototype DEVS is developed using VHB 4905 and embedded strain gauges bonded to the root of a tapered whisker. The DEVS is demonstrated to produce a maximum rotational output of ±22.8°. An electro-mechanical model of the DEVS is derived, which incorporates a hyperelastic material model and Euler- Bernoulli beam equations. The model is shown to predict experimental measurements of whisking stroke amplitude and whisker deflection.

In this paper a dynamic, physics-based model is studied analytically and experimentally for an ionic polymermetal composite (IPMC) sensor that is excited at the base. This work is motivated by structural monitoring and energy-harvesting applications of IPMCs. The model combines the vibration dynamics of a flexible beam under base excitation and the ion transport dynamics within the IPMCs. The vibration dynamics of a base-excited IPMC beam is obtained from the Euler-Bernoulli beam equation incorporating damping and accommodating suitable boundary conditions. The charge dynamics is derived by analytically solving the governing partial differential equation, which captures electrostatic interactions, ionic diffusion and ionic migration along the thickness direction. The derived model relating short-circuit sensing current to the base excitation is expressed as an infinite-dimensional transfer function, in terms of physical and geometric parameters, and is thus scalable. The model is then reduced to a finite-dimensional one for real-time signal processing. In particular, we present an inversion scheme for reconstructing the mechanical stimuli given the sensor output. Experimental results show that the proposed model captures well both the beam dynamics and the overall sensing dynamics. Simulation results are also presented to illustrate the inversion algorithm.

Recent applications of the scanned pipette to materials science problems have included its quantification of the ion flux resulting from conducting polymer actuation. However, in order to correlate this flux with the precise height changes arising from actuation, a separate experiment must be carried out. Herein we propose a new design that may be capable of simultaneously determining both ion flux and topography, on the basis of subtle current density magnitude shifts and precisely chosen experimental positioning parameters. A simulation of the geometrical model - consisting of the pipette, conducting polymer film and electrodes - was setup and solved in 2D axi-symmetrical domain. The ion concentrations, voltage potentials and current densities were determined as a function of time, with three key parameters varied: the maximum ion flux value Jmax, conducting polymer swelling Tp and overall separation distance d between pipette and polymer. It was found that the separation Tp - d should be around 50 to 150 nm, roughly the same as the actuation itself. Furthermore, the current density component arising from geometrical changes due to actuation was on the order of a few percent, and was highly sensitive to Jmax levels.

We report on new method to obtain micrometric electroactive polymer actuators operating in air. High speed conducting Interpenetrating Polymer Network (IPN) microactuators are synthesized and fully characterized. The IPN architecture used in this work allows solving the interface and adhesion problems, which have been reported in the design of classical conducting polymer-based actuators. We demonstrated that it is possible to reduce the thickness of these actuators by a specific synthetic pathway. IPN host matrixes based on polyethylene oxide / polytetrahydrofurane have been shaped by hot pressing. Then, the resulting thin host matrixes (below 10 μm) are compatible with the microfabrication technologies. After interpenetration of poly(3,4-ethylenedioxythiophene) (PEDOT), these electroactive materials are micro-sized using dry etching process. Frequency responses and displacement have been characterized by scanning electronic microscopy. These conducting IPN microactuators can be considered as potential candidates in numerous low frequency applications, including micro-valves, micro-optical instrumentation and micro-robotics.

We have been studying electrochemomechanical deformation (ECMD) of conducting polymers to realize artificial muscles or soft actuators, since 1992. For the practical application, i.e., strain, stress, response time, cycle stability and creep have to be improved to levels of demands. In this paper, some attempts to improve the strain are mentioned for polyaniline, polypyrrole and poly(3,4-ethylenedioxythiophene), PEDOT. Especially, PEDOT actuator was found to show novel features in ECMD under tensile loads. The actuation was driven by cation insertion upon reduction in any combination of electrolytes and solvents. Another interesting feature was that the actuation under tensile loads showed larger strain than that without tensile loads. These facts were explained with a model of helical confinement of anions during the electrodeposition and uniaxial alignment of helices by the electrochemical creep under tensile loads.

The effect of different fillers on the mechanical and dielectric properties of soft elastomers has been investigated. It was found that the addition of a small amount of silica fillers would increase the Young's modulus significantly but not simultaneously increase the tear strength sufficiently for processing as thin films. Addition of nanoclay and barium titanate nanoparticles to the soft elastomers was shown to be very favorable for the enhancement of the dielectric properties without increasing the Young's modulus significantly and could be used for DEAP material in e.g. microprocessing where the tear strength is not crucial for processing. However, for elastomer film processing it is suggested that a combination of the nanoclay or barium titanate with either silica particles or bimodal networks would give the right tear strength together with the desired increased dielectric permittivity.

Experiments indicate that the electrodes affect the charge dynamics, and therefore actuation of ionic polymermetal composite (IPMC) via three different types of currents - electric potential induced ionic current, leakage current, and electrochemical current if approximately higher than 2 V voltage is applied to a typical 200 μm thick IPMC. The ionic current via charge accumulation near the electrodes is the direct cause of the osmotic and electrostatic stresses in the polymer and therefore carries the major role in the actuation of IPMC. However, the leakage and the electrochemical - electrolysis in case of water based IPMCs - currents do not affect the actuation dynamics as directly but cause potential gradients on the electrodes. These in turn affect the ionic current. A physics based finite element (FE) model was developed to incorporate the effect of the electrodes and three different types of currents in the actuation calculations. The Poisson-Nernst-Planck system of equations is used in the model to describe the ionic current and the Butler-Volmer relation is used to describe the electrolysis current for different applied voltages and IPMC thicknesses. To validate the model, calculated tip deflection, applied net current, and potential drop in case of various IPMC thicknesses and applied voltages are compared to experimental data.

A multi-physical model of ionic polymer metal composites (IPMCs) is presented in this paper when they deform under an applied voltage. It is composed of two parts, which describe the dynamic electro-transport and the large deformation respectively. The first part describes the ion and water molecule transport, the equations of which are derived using the thermodynamics of irreversible process. Besides the gradient of the electric potential and the concentration usually considered in the previous models of IPMCs, the hydrostatic pressure gradient is confirmed to be one of the main factors induced the mass transport. The second states the eigen strain induced by the redistribution of ion and water molecule and reveals the stress field from micro to macro scale by the method of micromechanics. The elastic stress balanced with the eigen-stress including the hydrostatic pressure can influence the distribution of ion and water molecule reversely. To explore the reasonable mechanisms of the relaxation phenomena, various kinds of eigen-stresses are discussed here and preliminary numerical results evaluating deformation are given based on the classical Na⁺ Nafion type IPMC. It's obtained that the osmotic pressure is an indispensable eigen-stress to explain the complicated deformation.

Poly(t-butyl acrylate) is a bistable electroactive polymer (BSEP) capable of rigid-to-rigid actuation. The BSEP combines the large-strain actuation of dielectric elastomers with shape memory property. We have introduced a material approach to overcome pull-in instability in poly(t-butyl acrylate) that significantly improves the actuation lifetime at strains greater than 100%. Refreshable Braille display devices with size of a smartphone screen have been fabricated to manifest a potential application of the BSEP. We will report the testing results of the devices by a Braille user.

We investigated the effects of additives incorporated into the electrode layer in order to improve the actuation performance of dry-type carbon nanotube (CNT) actuators. Especially, the addition of conductive nano-particles such as polyaniline (PANI) and polypyrrole (PPy) improves actuation performance very much rather than the addition of nonconductive nano-particles such as mesoprous silica (MCM-41 type). In this paper, we studied on the influences of applied voltage, species of ionic liquid (IL), amounts of IL, thickness of actuator to optimize actuation performance. Imidazolium type ionic liquids with three different anions, that is, 1-ethyl-3-methylimidazolium (EMI) as a cation and tetrafluoroborate (BF₄), trifluoromethanesulfonate (OTf), and bis(trifluoromethanesulfonyl)imide (TFSI) as anions were chosen in this study. EMIBF₄ is the most suitable IL for our CNT actuator including PANI in the electrode layer. We tuned the amount of IL and the thickness of actuator. As a result, the strain was improved to be 2.2% at 0.1 Hz by applying the voltage of 2.5 V. This improved value is almost 2 times larger than our previous results. We also show the potential of improved CNT actuators for a thin and light Braille display.

There is still emerging need for more effective and technologically simple electrode materials for low voltage ionic EAP materials. Most extensively used carbon materials for bending and linear actuators are different types of carbon nanotubes. We have used for the electrode layers carbide-derived carbon (CDC) and several carbon aerogels. The differences in actuation performance were analyzed in the context of pore characteristics of carbons, electromechanical and electrochemical (EIS) properties. Quantum chemistry and molecular dynamics simulations were used to analyze in detail the actuation/sensor processes in material.

Dielectric elastomer actuators (DEAs) can be optimized by modifying the dielectric or mechanical properties of the electroactive polymer. In this work both properties were improved simultaneously by a simple process, the one-step film formation. The silicone elastomer network contains polydimethylsiloxane (PDMS) chains, as well as crosslinker and grafted molecular dipoles in varying amounts. This leads to films, which are homogenous down to the molecular level. Films with higher permittivity and reduced stiffness were obtained. As matrix two PDMS-materials with different molar masses, leading to other network chain lengths, were compared. This directly influences the network density and thus the mechanical properties. A higher electrical field response for long chain matrix materials was found. The actuation sensitivities for both materials were enhanced by 6.3 and 4.6 times for the short and long chain matrix material, respectively.

A new robotic leg design is presented that utilizes dielectric elastomers (3M VHB 4910) to rapidly control stiffness changes for enhanced mobility and agility of a field demonstrated hexapod robot. A set of electromechanical test are utilized to obtain up to 92% reduction in stiffness that is controlled by an electric field. The results are compared to a finite deformation membrane finite element model to understand and improve field driven stiffness changes for real-time robotic applications.

Predictive models for Dielectric Elastomer Actuators require the nonlinear solid mechanics theory of soft dielectrics. This is certainly true for homogeneous systems, but also for devices made of composite materials, where the insertion of stiff conductive particles in the soft matrix may help to improve the overall actuation performance. In this note, we present a theoretical framework to investigate a wide range of instabilities in both homogeneous and composite-manufactured actuators: pull-in/electromechanical instability, buckling-like modes and band-localization failure, that can be analyzed taking into account all the geometric and electromechanical properties of the device such as i) nonlinearities associated with large strains and the employed material model; ii) initial prestretch applied to the system; iii) dependency of the permittivity on the deformation (electrostriction). In particular, we focus on the general expression which gives the condition for pull-in instability, also valid for anisotropic composite soft dielectrics. In the second part, we show that in a layered composite an electromechanical/snap through instability can be designed and possibly exploited to conceive release-actuated systems.

A new design for a multi-layer dielectric elastomer actuator, reinforced with periodic stiffeners is presented. The resulting actuator enables complex out-of- plane motion without the need of the elastomer membrane prestretch. An in situ optical imaging system is used to capture the complex deformation pattern and track the non-planar displacement and curvature under the applied voltage. The role of the stiffeners periodicity, φ, on the macroscopic actuator response is analyzed numerically utilizing ABAQUS finite element software. A user-material subroutine is developed to represent the elastomer deformation under the applied electric field. It is found that the actuator force-stroke characteristics can be greatly changed by varying φ, while maintaining the same overall actuator stiffness. The numerical results showed a band of localized deformation around the stiffeners. The refinement of the stiffener, φ, increases the total actuated volume within the span of the actuator, and thereby the macroscopic actuator stroke. The stored elastic strain energy within the actuator is also increased. φ might be further refined down to the actuator sheet thickness, wherein the localized deformation bands overlaps. This is the practical limit of the stiffeners spacing to achieve the largest macroscopic actuator stroke. The developed experimental and modeling framework would enable the exploitation and optimization of different actuator designs to achieve a preset load-stroke characteristic.

Dielectric elastomer actuators (DEA) and bistable electroactive polymers (BSEP) both require compliant electrodes with rubbery elasticity and high conductivity at large strains. Stretchable opto-electronic devices additionally require the compliant electrodes to be optically transparent. Many candidate materials have been investigated. We report a new approach to mechanically robust, stretchable compliant electrodes. A facile in-situ composite synthesis and transfer technique is employed, and the resulting composite electrodes retain the high surface conductivity of the original conductive network formed by nanowires or nanotubes, while exhibiting the mechanical flexibility of the matrix polymer. The composite electrodes have high transparency and low surface roughness useful for the fabrication of polymer thinfilm electronic devices. The new electrodes are suitable for high-strain actuation, as a complaint resistive heating element to administer the temperature of shape memory polymers, and as the charge injection electrodes for flexible/stretchable polymer light emitting diodes. Bistable electroactive polymers employing the composite electrodes can be actuated to large strains via heating-actuation-cooling cycles.

Electroactive polymer (EAP) actuators are compliant capacitors, where a thin elastomer film is sandwiched between two compliant electrodes. When a high DC voltage is applied to the electrodes, the arising electrostatic pressure squeezes the elastomer film in thickness and thus the film expands in planar directions. They are very promising candidates for "artificial muscles" development. Dielectric elastomer transducers benefit of important advantages compared to other electro-mechanical actuators: high energy density, large and noise-free deformation capability and low cost materials. However, if EAP devices have to be cheap, they work at high voltage (> 1000 V) leading to need for expensive electronics. Such operating conditions preclude their use close to the human body. The electrode material is also a challenge, since clean and fast processes suited to miniaturization of EAP devices are still missing. To solve these drawbacks, we are developing a new fabrication process aiming at reducing the dielectric layer thickness down to <20μm and to increase the efficiency using highly conductive electrode materials deposited by magnetron sputtering. In this work, we show how we succeed in finding the conditions for deposition of compliant metallic thin films that are able to maintain high conductivity at more than 10% stretching. The films are characterized by X-Ray Diffraction, electrical conductivity measurements and Atomic Force Microscopy.

Metallic thin films have not often been used as electrodes in dielectric elastomer actuators (DEAs) as the reported actuated strains have been small. This is especially so when compared to commonly used conductive greases and powders. Here, the use of thin silver films formed by electroless deposition (ELD silver) as electrodes in DEAs is studied. As electroless deposition involves only the use of chemicals, expensive equipment is not needed. That, coupled with the fact that the thin silver electrodes require only a small amount of silver per unit area, means that such electrodes are simple and inexpensive to fabricate. In addition, unlike conductive powders and greases, these silver films adhere well to most substrates that are or have been made hydrophilic. This is especially useful in maintaining structural integrity of the actuator, such as when DEA units need to be stacked up one on top of each other. Most importantly, thin silver film electrodes have the ability to self heal. Self-healing not only averts actuator failure brought about by localised breakdowns, it also enables actuation to resume, even allowing higher driving voltages to be reached. In this paper, we demonstrate that DEAs with corrugated ELD silver electrodes can allow actuated area strains of up to 125% at a relatively low driving voltage of 1.9 kV. This is due to the low stiffening effect that the corrugated ELD silver electrodes have on the dielectric layer, which was found to be close to that of graphite.

Unlike electromagnetic actuators, Dielectric Elastomer Actuators (DEAs) can exert a static holding force without consuming a significant amount of power. This is because DEAs are electrostatic actuators where the electric charges exert a Maxwell stress. A charged DEA stores its electrical energy as potential energy, in a similar way to a capacitor. To remove or reduce the Maxwell stress, the stored charge with its associated electrical energy must be removed. Current DEA driver electronics simply dispose of this stored electrical energy. If this energy can be recovered, the efficiency of DEAs would improve greatly. We present a simple and efficient way of re-using this stored energy by directly transferring the energy stored in one DEA to another. An energy transfer efficiency of approximately 85% has been achieved.

This study found that compliant electrodes using charcoal powder enable self clearing property to dielectric elastomer actuator. Charcoal powder is applied as compliant electrodes by smearing on a 100% bi-axially pre-stretched dielectric elastomer membrane (VHB 9473), with nominal pre-stretched thickness of 62.3 μm. This DEA using charcoal-powder electrodes can sustain up 10 kV without terminal breakdown, while those using graphite or silver grease break down at slightly above 2 kV. It is noted that this DEA using charcoal-powder has maximum areal strain at about 45 % at 4 kV, beyond which the strain does not increase further for reduced electrical conductivity. The dielectric elastomer actuator using the charcoal-powder electrodes generate less actuation strain than that using the graphite. However, the former can produce a large actuation stress as it can driven to a higher driving voltage without pre-mature breakdown.

We report carbide-derived carbon (CDC) based polymeric actuators for the low-voltage applications. The CDC-based actuators have been designed and fabricated in combination with gold foil. The gold-foil-modified actuators exhibited high frequency response and required remarkably low operating voltage (as low as ±0.25 V). Hot-pressed additional gold layer (thickness 100 nm) ensures better conductivity of polymer supported CDC electrodes, while maintaining the elasticity of actuator. Energy consumption of gold-foil-modified (CDC/gold) actuators increased only at higher frequency values (f > 1 Hz), which is in good correlation with enhanced conductivity and improved charge delivery capabilities. Electrochemical measurements of both actuators performed at small operating frequency values (f < 0.01 Hz) confirmed that there was no difference in consumed charge between conventional CDC and CDC/gold actuators. Due to enhanced conductivity of CDC/gold actuators the accumulated charge increased at higher operating frequency values, while initiating larger dimensional changes. For that reason, the CDC/gold actuators exhibited same deflection rate at much lower potential applied. Electrochemical impedance measurements confirmed that relaxation time constant of gold-foil-modified actuator decreased more than one order of magnitude, thus allowing faster charge/discharge cycles. Gold-foil-modified actuators obtained the strain level of 2.2 % when rectangular voltage ±2 V was applied with frequency 0.5 Hz. The compact design and similar working principle of multi-layered actuator also provides opportunity to use actuator concurrently as energy storage device. From practical standpoint, this device concept can be easily extended to actuator-capacitor hybrid designs for generation of energy efficient actuation.

The operation of Dielectric Elastomer Transducers typically requires high voltages in the kilovolt range and relatively low currents. Therefore, for driving Dielectric Elastomer Transducers a high voltage power electronics is necessary. For realization of energy efficient actuator and generator applications bidirectional switched-mode converter topologies should be used enabling a bidirectional energy transfer as well as a high efficiency. In this contribution a modular converter system consisting of several switched-mode converter modules featuring galvanic isolation is presented as a basic concept for realization of a high voltage power supply. Three converter topologies - bidirectional flyback, Dual Active Bridge and Isolated Bidirectional Full-Bridge converter - are investigated and suitable modulation schemes are presented, which are based on hysteretic current-mode control, enabling a high converter dynamic and limitation of the converter output current in order to prevent electrode damage. Simulation results for the proposed converter topologies are presented and experimental results for a single bidirectional flyback converter module are shown.

High surface area carbon, ionic liquid and polymer are incorporated in an electromechanically active composite. This laminate bends when voltage (typically less than 3 V) is applied between the electrodes, and generates voltage and current when bent with an external force. By suitable optimization, the material can be used either as an actuator, energy storage element (supercapacitor) or sensor. Strain caused by bending promotes dislocation of ions in the micropores of carbon. As a result, the charge separation occurs because ions of ionic liquid are likely trapped in the micropores of diameters close to the ion sizes.

As the primary flow sensing organ for fishes, the lateral line system plays a critical role in fish behavior. Analogous to its biological counterpart, an artificial lateral line system, consisting of arrays of micro flow sensors, is expected to be instrumental in the navigation and control of underwater robots. In this paper we investigate the microfabrication of ionic polymer-metal composite (IPMC) cilia for the purpose of flow sensing. While existing macro- and microfabrication methods for IPMCs have predominantly focused on planar structures, we propose a device where micro IPMC beams stand upright on a substrate to effectively interact with the flow. Challenges in the casting of 3D Nafion structure and selective formation of electrodes are discussed, and potential solutions for addressing these challenges are presented together with preliminary microfabrication results.

Mechanical characterization of soft elastomers is usually done either by traditional shear rheometry in the linear viscoelastic (LVE) regime (i.e. low strains) or by extensional rheology in the nonlinear regime. However, in many commercially available rheometers for nonlinear extensions the measurements rely on certain assumptions such as a predefined shape alteration and are very hard to perform on soft elastomers in most cases. The LVE data provides information on important parameters for DEAP purposes such as the Young's modulus and the tendency to viscous dissipation (at low strains only) but provides no information on the strain hardening or softening effects at larger strains, and the mechanical breakdown strength. Therefore it is obvious that LVE can not be used as the single mechanical characterization tool in large strain applications. We show how the data set of LVE, and large amplitude oscillating elongation (LAOE)¹ and planar elongation^2,3 make the ideal set of experiments to evaluate the mechanical performance of DEAPs. We evaluate the mechanical performance of several soft elastomers applicable for DEAP purposes such as poly(propyleneoxide) (PPO) networks^3,4 and traditional unfilled silicone (PDMS) networks⁵.

Dielectric electroactive polymers are thin films based on elastomeric material coated with compliant and conductive electrodes. By applying an electrical field, the polymer performs large deformations, which can be utilized to generate sound waves. When using such kind of electrostatic loudspeakers, no additional resonating sound boxes are required and the vibrating mass is very lightweight, resulting in an excellent impulse and wide-band frequency response. For the loudspeaker's operation both an electrical bias voltage and a mechanical bias stress have to be applied. In this contribution different possibilities are presented to generate the mechanical bias stress. The design of an appropriate power electronics for the acoustic transducer, which is build of standard components, is also described. Finally, the loudspeaker concepts are evaluated by experiments in an anechoic room.

Ionic Polymer Metal Composites (IPMCs), as one of the most promising smart materials, can produce a large deformation for low voltage in the range of 0-5V. Since the materials were found, IPMCs have often been studied as actuators for their large deformation and inherent flexibility. Recently, IPMCs are applied to the optical lens-driving system. In this paper, we design miniature optical lens actuators for the focusing requirements. And two kinds of the driving structure, the petal-shaped and annular structure, are proposed. Then, the preparation processes of IPMCs and the actuators are presented and five kinds of petal-shaped and annular actuators are manufactured and their performances are tested, respectively. Finally, the performances of the actuators with different parameters are analyzed by an equivalent thermal model with FEA software.

IPMCs are bi-polar actuators capable of large, rapid actuation in flexural configurations. The limit of actuation is defined by the maximal voltage that can be applied to the IPMC, above which electrolysis of the electrolyte and damage to the IPMC may occur. In this paper we present preliminary results that indicate how this actuation limit could be tuned and even exceeded through controlled thermal cycling of gold-plated Nafion IPMCs. Thermal cycling is used to move the centre point of the actuation stroke. Subsequent voltage stimulation actuates the structure around this new centre point. It is shown that by further thermal cycling this centre point naturally returns to its initial position. By exploiting this shape memory characteristic as part of a control system it is expected that more sophisticated IPMC actuation will be achievable.

Hydraulic Artificial Muscles (HAMs) consisting of a polymer tube constrained by a nylon mesh are presented in this paper. Despite the actuation mechanism being similar to its popular counterpart, which are pneumatically actuated (PAM), HAMs have not been studied in depth. HAMs offer the advantage of compliance, large force to weight ratio, low maintenance, and low cost over traditional hydraulic cylinders. Muscle characterization for isometric and isobaric tests are discussed and compared to PAMs. A model incorporating the effect of mesh angle and friction have also been developed. In addition, differential swelling of the muscle on actuation has also been included in the model. An application of lab fabricated HAMs for a meso-scale robotic system is also presented.

A multi-walled carbon nanotube (MCNT)/Nafion nanocomposite was fabricated by dispersion of treated MCNTs in a Nafion solution. The multi-walled carbon nanotube (MCNT) filler was prepared with the cationic surfactant cetyl trimethyl ammonium bromide. Starting from cast Nafion membranes, IPMCs were manufactured by electroless plating. The current and the blocking force were measured with an IPMC actuation testing apparatus. Compared with a bare Nafion-based IPMC, the blocking force of the new IPMC improved 1-1.4 times, and the current increased by 33%-67%. The clearly enhanced performance of the new MCNT filler-based IPMC is attributed to the well-distributed MCNTs that improved the electrical properties of the IPMC. Finally, the new IPMC was successfully employed to directly actuate gecko-inspired adhesive arrays that we fabricated by ourselves.

Electroactive polymers (EAPs) that bend, swell, ripple (first generation materials), and now contract with low electric input (new development) have been produced. The mechanism of contraction is not well understood. Radionuclide-labeled experiments, molecular modeling, electrolyte experiments, pH experiments, and an ionic concentration experiment were used to determine the chain of events that occur during contraction and, reciprocally, expansion when the polarity is reversed, in these ionic EAPs. Plasma treatment of the electrodes, along with other strategies, allows for the embedded electrodes and the EAP material of the actuator to work and move as a unit, with no detachment, by significantly improving the metal-polymer interface, analogous to nerves and tendons moving with muscles during movement. Challenges involved with prototyping actuation using contractile EAPs are also discussed.

The contribution describes a new kind of multi-layer beam with a variable stiffness based on electroactive polymers (EAP). These structures are supposed to be components of new smart, self-sensing and -controlling composite materials for lightweight constructions. Dielectric Elastomer foils from Danfoss PolyPower are used to control the beam's stiffness. The basic idea is to change the area moment of inertia of bending beams. These beams are built up as multi-layer stacks of thin metal or PMMA plates. Its internal structure can be changed by the use of the electroactive polymers for controlling the area moment of inertia. So it is possible to strongly change the stiffness of bending beams up to two orders of magnitude. Thereby, the magnitude of varying the stiffness can be scaled by the number of layers and the number and type of electroactive polymer elements used within the bending beam. The mechanisms for controlling the area moment of inertia are described in detail. Modeling of the mechanical structure including the EAP uses a pseudo rigid-body model, a strain energy model as well as a finite element analysis. The theoretical calculations are verified by experiments. The prototype described here consists of two structural layers. First results show the feasibility of the proposed structure for mechanical components with stiffness control.

This paper presents the re-creation of the bell deformation cycle of the Aequorea victoria jellyfish. It focuses on the design, fabrication, and characterization of the bio-inspired bell kinematics of an IPMC actuated robotic jellyfish. The shape and bell kinematics of this underwater vehicle are based on the Aequorea victoria jellyfish. This medusa is chosen as a model system based on a comparative bell kinematics study that is conducted among different jellyfish species. Aequorea victoria is known by its low swimming frequency, small bell deformation, and high Froude efficiency (95%). Different methods of implementing the actuators underneath the bell with smaller IPMC actuators are investigated to replicate the natural jellyfish's bell deformation. Results demonstrates that proper placement of the IPMC actuators results in bell configuration that more accurately represents the deformation properties of the natural jellyfish. Smaller IPMC actuators are used to achieve the desired deformation and thus the power consumption is reduced by 70% compared to previous generations. A biomimetic jellyfish robot prototype is built, and its ability to swim and produce thrust with smaller IPMC actuators is shown. The robot swam with four actuators swam at an average speed 0.77 mm/s and consumed 0.7 W. When eight actuators were used the average speed increased to 1.5 mm/s with a power consumption of 1.14 W.

Biological cells regulate their biochemical behavior in response to mechanical stress present in their organism. Most of the available cell cultures designed to study the effect of mechanical stimuli on cells are cm² area, far too large to monitor single cell response or have a very low throughput. We have developed two sets of high throughput single cell stretcher devices based on dielectric elastomer microactuators to stretch groups of individual cells with various strain levels in a single experiment. The first device consists of an array of 100 μm x 200 μm actuators on a non-stretched PDMS membrane bonded to a Pyrex chip, showing up to 4.7% strain at the electric field of 96 V/μm. The second device contains an array of 100 μm x 100 μm actuators on a 160% uniaxially prestretched PDMS membrane suspended over a frame. 37% strain is recorded at the nominal electric field of 114 V/μm. The performance of these devices as a cell stretcher is assessed by comparing their static and dynamic behavior.

Manipulators based on rigid, kinematically constrained structures and highly geared electromagnetic actuators are poorly suited in applications where objects are soft, delicate, or have an irregular shape, especially if they operate outside of the highly structured environment of a factory. Intrinsically soft DEA, imparted with the ability to self-sense enable the creation of soft, smart artificial muscles provide a way forward. Inherent compliance simplifies manipulator trajectory planning and force control, enables the manipulator to conform to the object, and provides natural damping of mechanical disturbances. In this paper we present a simple proof-of-concept building block that could be used to create a compliant DEA-based manipulator with self-sensing feedback. Capacitive self-sensing has been used to both detect when contact is made with an object and gather information about the object's stiffness. Integrated into a manipulator, this information could be used to adjust the grip directly, or used to reposition or reorient the manipulator to achieve a desired grasp.

Mechanical energy can be converted into electrical energy by using a dielectric elastomer generator. The elastomer is susceptible to various models of failure, including electrical breakdown, electromechanical instability, loss of tension, and rupture by stretching. The models of failure define a cycle of maximal energy that can be converted. On the other hand, when subjected to voltage, the charge will be induced on a dielectric elastomer. When the voltage is small, the charge increases with the voltage. Along with the continuously increase of voltage, when the charge approaches a certain value, it would become saturated. This paper develops a thermodynamic model of dielectric elastomers undergoing polarization saturation. We studied the typical failure model with three variables of Gent Model silicone energy harvester and obtained an analytical solution of the constitutive equation of dielectric elastomer undergoing polarization saturation. These results can be used to facilitate the design and manufacture of dielectric elastomer energy harvesters.

A simple analytical relationship for the efficiency of a constant charge dielectric elastomer energy harvesting cycle is derived for the case of pure shear. The relationship takes into account the nonlinear nature of elastomer materials and the effects of electrically induced strains during relaxation. It is explicitly shown that efficiency is dependent on the applied strain, the shape of the stress-strain curve, and on a lumped parameter (Z') containing the applied electric field, stiffness and permittivity. We show that any term in the lumped parameter can be offset by the other terms; thus a stiff material may require a higher permittivity or electric field to attain the same efficiency as a similar soft material.

Mechanical energy and electrical energy can be converted to each other by using a dielectric elastomer transducer. Large voltage-induced deformation has been a major challenge in the practical applications. The voltage-induced deformation of dielectric elastomer is restricted by electromechanical instability (EMI) and electric breakdown. We study the loading path effect of dielectric elastomer and introduce various methods to achieve giant deformation in dielectric elastomer and demonstrate the principles of operation in experiments. We use a computational model to analyze the operation of DE generators and actuators to guide the experiment. In actuator mode, we get three designing parameters to vary the actuation response of the device, and realize giant deformation with appropriate parameter group. In the generator mode, energy flows in a device with inhomogeneous deformation is demonstrated.

Dielectric elastomer generators (DEG) are variable capacitor power generators that are a highly promising technology for harvesting energy from environmental sources because they have the ability to work over a wide frequency range without sacrificing their high energy density or efficiency. DEG can also take on a wide range of configurations, so they are customizable to the energy source. A typical generation cycle requires electrical charge to be supplied and removed from the DEG at appropriate times as it is mechanically deformed. The manner in which the DEG charge state is controlled greatly influences energy production. The recently developed self-priming circuit can provide this functionality without any active electronics, but it is not configurable to match the generator and its energy source. In this paper a highly configurable self-priming circuit is introduced and an analysis of the self-priming DEG cycle is performed to obtain design rules to optimize the rate at which it can boost its operating voltage. In a case study we compare the performance of an initial prototype selfpriming circuit with one that has been intentionally optimized. The optimized generator voltage climbed from 30 V up to 1500 V in 27 cycles, whereas the same generator required 37 cycles when the suboptimal self-priming circuit was used.

This paper describes the theoretical analysis for changing the stiffness in dielectric elastomer stack actuators (DESA) by electric voltage and investigates the influence of the mounting of DESA. The theoretical calculations are validated by the experimental measurements. The tuning of the stiffness by electrical voltage can be used for small adaptive absorbers to attenuate varying resonance frequencies of a system for example caused by the temperature variations. The best experimental results were reached for the structure with unbonded DESA between stiff plates. The resonance frequency was shifted from 129 Hz to 108 Hz. Besides, the selective mounting of DESA is a promising approach for the adaptive absorber applications.

Partial discharges (PD) occur in solid insulating materials when the insulating material is partially bridged by an electrical discharge in response to an applied voltage stress. PDs typically occur at localized points of high field stresses or at voids and other inhomogeneities within the insulator. The applied field's effect on the frequency of occurrence and intensity of PDs can be used to assess the electrical breakdown strength and aging characteristics of insulating materials. PD testing is therefore a promising characterization method to understand the insulating properties of the elastomers and geometries commonly used in DEAs. Prestretched (~100% and ~230% biaxial) and unstretched acrylic elastomers (3M VHB tapes) with solid metal electrodes have been tested. We have found the number and intensity of PDs increase with applied field, and that a significant number of PDs are detected before any actuation was visibly observed, implying that the fields required for actuation will cause material aging and degradation over time. Most interestingly, the number of PDs steadily increase as the applied voltage increases up to a sufficiently high voltage, where the PDs suddenly cease. Since internal voids can cause PDs, this may indicate that the Maxwell stress minimized the thickness of or eliminated these voids, which could explain how prestretching improves performance.

Thanks to their high energy density and their flexibility, scavenging energy with dielectric polymer is a promising alternative to ensure the autonomy of various sensors such as in e-textiles or biomedical applications. Nevertheless, they are passive materials requiring a high bias voltage source to polarize them. Thus, we present here a new design of scavenger using polymer electrets for poling the dielectric polymer. Our scavenger is composed of commercial dielectric polymer (3M VHB 4910) with Teflon electrets developing a potential of -300V, and patterned grease electrodes. The transducer works in a pure shear mode with a maximal strain of 50% at 1Hz. The typical "3D-textured" structure of the scavenger allows the electrets to follow the movement of the dielectric. A complete electromechanical analytical model has been developed thank to the combination of electrets theory and dielectric modelling. Our new autonomous structure, on an optimal resistance, can produce about 0.637mJ.g^-1.

The electromechanical behavior of dielectric elastomer is strongly affected by the temperature. Very few models accounting for the effects of temperature exist in the literature. A recent experiment showed that the variation of dielectric constant of the most widely used dielectric elastomer (VHB 4910, 3M) according to temperature is relatively significant. In this paper, we develop a thermodynamic model to study the influence of temperature on the instability in dielectric elastomer by involving deformation and temperature-dependent dielectric constant. The results indicate that the increase of temperature could improve the actuation stress and the electromechanical instability of the elastomer.

Subjected to a high electric field, the dielectric deforms. If the dielectric is soft, the voltage induced deformation is large. The deformation is determined by the breakdown voltage together with electromechanical instability and snap-through instability. Based on the theoretical research proposed by Suo and Li, taking the dielectric elastomer soft material research object, we introduce two kinds of material limits: strain-stiffening, polarization saturation, analyze the effect of material limits on voltage induced deformation. For a specific soft dielectric material under certain pre-stretch, the theoretical maximum electrical actuation deformation can be determined.

One of the main technical challenges in the development of dielectric elastomer (DE) stack actuators is the design and realization of suitable electrodes. They must be compliant and be able to undergo large strains without adding too much stiffness. Metal electrodes are therefore normally out of question due to their high stiffness, though their electrical properties are excellent. In this work a new design approach is presented which comprises rigid metal electrodes. Its functionality is proven by means of numerical simulations and experimental tests. It allows the customized tailoring of transducer elements due to the designable electrode structure. A functional demonstrator is built and tested concerning its electrical, mechanical and electromechanical behavior. For this new actuator type a full electromechanical model is developed. It contains all transfer characterisitcs in a nonlinear description and accounts for various physical effects arising from the special actuator design. Due to its standardized interface configuration it can well be used in combination with existing models for mechanical structures and electrical amplifiers to completely model active systems. It is applicable for the realistic simulation necessary in the development of active solutions with EAP devices. A first longterm test with 108 load cycles was performed in order to show the durability of the actuator.

Dielectric elastomer actuators (DEA) based on an organically modified silicone elastomer are introduced. The elastomer carries fluorinated sidegroups in the polysiloxane molecular chain and is synthesized from precursors which all are fluorinated. A fluorinated silicone oil is added in consecutive concentration steps as a softening agent. The electric properties of the modified silicone elastomers in terms of the permittivity, specific conductivity and electric breakdown field strength were investigated and compared with those of the unmodified silicone elastomer as the reference material. Moreover, the mechanical characteristics like Young's modulus in tensile and compressional load as well as the storage and loss modulus in shear load were studied. The permittivity of the modified silicone is enhanced by 80 % compared to the unmodified silicone elastomer. No strong alteration of the specific conductivity occurs. The electric breakdown field strength is comparable to that of the reference material. Simultaneously, the Young's modulus is decreased by the softening agent. Actuation measurements on model actuators show, that the actuation strain of the best materials surmounts that of the unmodified reference material by a factor of up to 5. The modified silicone elastomer materials can also be used for dielectric elastomer sensors and generators.

Robotic grasping requires not only force and touch sensors but also flexibility of such sensors because most of the sensors are attached to the finger tip. Many studies are underway in such sensors using polymer because polymer is flexible and affordable. Polydimethylsiloxane (PDMS) is one of widely used substances because it is very stable physically and chemically. The principle of the capacitive force sensor using polymer is as follows; capacitance values will be changed by changes in the thickness of the dielectric elastomer under normal force or changes in the overlapping area of electrodes under shear force. The force and moment are measured by such changes. Conventional one-axis capacitive type force sensors measure normal or tangential force from one pair of electrodes. The increased number of electrodes can be used for multi-axis force sensors at the cost of the size of the sensor and resolution of the sensor. In this paper, we propose a dual-axis capacitive and resistive hybrid-type force sensor using dielectric elastomer with only one pair of electrodes. The electrodes are made with thermal evaporator. With only one pair of electrodes, the normal force is measured from the change of capacitance and resistance values and the shear force is measured from the change of only capacitance values. Experimental results verify the effectiveness of the proposed dual-axis hybrid type force sensor.

In practical applications, stress-relaxation phenomenon is not preferable feature of IPMC (ionic polymer-metal composite) actuators. In this study, we propose a control method using two (or more) IPMCs in order to reduce the stress-relaxation phenomenon. In the experiment, the force generated by two IPMC strips is measured by a force sensor. The proposed control signal consists of a small fluctuating signal which is oscillating independently of the command, in addition to a simple feedback controller with a feedforward term. We have found that the time to reach the limit voltage became more than twice if the fluctuating signal was added.

IPMC was considered as a polyelectrolyte membrane sandwiched between two flat electrodes in most of its theoretical models. However, structural idealization (ignorance of the interface) may lead to problematic predictions; therefore a proper model to characterize IPMC structures is expected for a more sophisticated electrochemistry or deformation theory. This paper proposed a geometrical model for the electroless-plated palladium-electroded IPMC (Pd-IPMC), where it's treated as a composite containing three distinguished layers: upper electrode, interface layer, and the substrate membrane. Especially, fractal dimension was adopted to describe the rough contact surface between the upper electrode and the substrate membrane. And the interface was determined by the volume fraction of the palladium particles. Based on this model, we estimated the elastic modulus of Pd electrode, and the value was found to be far less than Pd metal. Furthermore, we estimated the tensile elastic modulus of Pd-IPMC, the result agrees well with the experimental one, which proved the applicability of the structure model.

Ionic polymer-metal composites (IPMCs) are an emerging class of electroactive polymers that display both actuating and sensing capabilities. In this study, a longitudinal tensile force performance of millimeter thick IPMCs was investigated. Both, 0.5 mm and 1 mm thick IPMCs with Pt electrodes were tested in tensile mode, by monitoring the change of tensile load in response to applied electric fields. The measurements were performed either under static pre-strain conditions or by dynamically increasing the tensile strain with constant rate, while switching the voltage on and off periodically. The measurements under pre-load and constant voltage were performed in order to evaluate the maximum tensile force of the samples. Our results demonstrate that Pt-IPMCs which show the blocking force in bending direction in range of 50 mN, are capable of generating tensile forces in longitudinal direction more than 1.5 N at an applied voltage of 3 V DC.

In this paper, we carried out the impedance measurements of the bucky-gel actuators and analyzed the results by means of the porous electrode model. We also measured the displacement of the same actuators by applying sinusoidal voltages of various frequencies. The frequency dependence of the displacement responses is discussed in relation with the impedance properties of the bucky-gel electrodes. The electrochemical equivalent circuit of the bucky-gel actuator is discussed on the basis of the impedance analysis. Accordingly, we are able to develop an electrochemical model allowing to analyze the behavior of these actuators.

Robot-assisted surgery provides the surgeons with new tools to perform sophisticated surgical operations in a minimally invasive manner. Small robotic end-effectors at the tip of the surgical forceps are the key advantage of robotic surgery over laparoscopic surgery and any improvement on the design of these small robots can significantly improve the overall functionality of the surgical robots. In this sense, novel bio-compatible electro-active polymeric actuators can improve the design and functionality of these robotic end-effectors particularly by introducing smaller and more flexible robotic tools. Here, we introduce the applications of IPMCs as flexible actuators with embedded tactile and force feedback sensors in minimally-invasive robotic surgery. A new design for the robotic manipulation of the organs is presented in which a two dimensional IPMC actuator is replaced with the rigid robotic distal tip. It is shown that with a customized design, IPMC actuators maintain the required dexterity for two-dimensional bending of robotic distal tip. The overall design of the robot could be considered as a hybrid robot with the combination of rigid robotic links and flexible IPMC actuator with two degrees of freedom. On the other hand with the current robotic distal tips, no tactile force feedback is available during surgery and the surgeons rely solely on vision feedback. With the proposed design of actuator, the IPMC based distal tip could be used to deliver force feedback data by using an embedded IPMC tactile sensor. Design considerations, kinematics and chemo-electro-mechanical model of the proposed actuator is presented.

We demonstrate here an alternative dielectric elastomer actuator (DEA) structure, which relies on the compliant nature of elastomer membranes but does not require any electric field in the elastomer. Our elastomer zipping device is a macroscopic version of the electrostatic zipping actuators common in silicon MEMS. It consists of a cm-sized metallic bottom electrode, covered by a thin insulator, on which the elastomer membrane is bonded, enclosing a tapered air gap. A compliant electrode is patterned on the lower face of the elastomer membrane. Applying a voltage between solid bottom electrode and compliant electrode leads to controlled pull-in in movement, comparable to the closing of a zipper, thus giving large strokes and forces with no electrical requirements on the elastomer since no voltage is applied across the membrane. The compliant electrodes (20 mm diameter) are produced by metal ion-implantation into the elastomer membranes. The bottom metal electrodes are coated with 10 to 30 μm of Al₂O₃. We report on our experimental study of membrane deflection and dynamics and discuss the effect of design parameters such as elastomer mechanical properties and actuator geometry. Membrane deflection of up to 1.4 mm was reached at only 200 V actuation voltage. The large membrane deformation achieved with this zipping actuation can be applied to applications such as pumps or tunable liquid lenses. The out-of plane movement of the membrane can be used for linear actuation.

We report on the use of zipping actuation applied to dielectric elastomer actuators to microfabricate mm-sized pumps. The zipping actuators presented here use electrostatic attraction to deform an elastomeric membrane by pulling it into contact with a rigid counter electrode. We present several actuation schemes using either conventional DEA actuation, zipping, or a combination of both in order to realize microfluidic devices. A zipping design in which the electric field is applied across the elastomer membrane was explored theoretically and experimentally. Single zipping chambers and a micropump body made of a three chambers connected by an embedded channel were wet-etched into a silicon wafer and subsequently covered by a gold-implanted silicone membrane. We measured static deflections of up to 300 μm on chambers with square openings of 1.8 and 2.6 mm side, in very good agreement with our model.

Dielectric electroactive polymers respond to an applied electric field by deformation as described by the Maxwell effect. The response depends on the polymers' dielectric constant and stiffness. Addition of a high dielectric filler material has been shown to enhance the strain response. We report preliminary results on the enhancement of p(EGPEA) polymer films by addition of 1 w/v% of gold-capped, 500 nm SiO₂ Janus particles (JP-SiO₂). In comparison to pure p(EGPEA) and p(EGPEA) filled with unmodified SiO₂ particles, JP-SiO₂ p(EGPEA) films show an up to 24 times enhanced response. Measurement of the relative dielectric constant and the Young's Modulus indicate that the Janus particle additive increases the relative dielectric constant of the films, while at the same time decreasing the Young's Modulus leading to an overall larger electrostrictive coefficient for the JP-SiO₂ p(EGPEA) films.