Papers by Keyword: Dielectric Elastomer

Abstract: Unimorph cantilever is widely used in many applications with its bending and tip-deflection. In this paper, a model of the cantilever with the applied voltage and tip-deflection is presented. With the use of this model, a prototype, fabricated by VHB and polycarbonate, is estimated for its bending tip-deflection under a high voltage. And the experiment system is established with a signal generator, high voltage amplifier and laser displacement meter. The experimental results and the theoretical ones are both the same. The conclusions in this paper can be used to make further research on the deformation control of structures.

Abstract: The circular actuators of dielectric elastomer are a type of basic configurations [1]. A pre-stretched polymer film with an annulus electrode will be investigated in this work. The deformation along the radius was be proved to be inhomogeneous [2]. We study the inhomogeneous properties of circular ring actuators based on the ideal dielectric model and meanwhile obtain the failure modes of tension loss which will occur under different geometric parameters. For this type of circular actuator, the loss of tension will occur before electric breakdown. The method illustrated here is generic and can be applied to other complex circular configuration. The results will contribute to the further improvement of DE.

Abstract: Dielectric elastomer sensors are a new kind of capacitive sensors. They can be used to measure forces, pressures and deformations. The sensors have several advantages such as high elasticity and inexpensive fabrication compared with traditional sensors. In this paper, a new sensing device for measuring small concentrated force is proposed. The structure of the device is a cantilever beam with constant strength on which is fixed the dielectric membrane. The dielectric membrane is a capacitance sensor built with dielectric polymer coated with soft electrodes. When the cantilever beam is subjected to a concentrated force at its free end, the strain changed in the cantilever beam will induce the change in the capacitance of the membrane. According to the relation, the unknown concentrated force can be monitored by measuring the change in the capacitance. The testing results on the device show that the concentrated force at the free end of the cantilever beam is approximately proportional to the change in the capacitance. The prototype demonstrated the new device is capable of monitoring small concentrated force with prominent sensitivity.

Abstract: Temperature can significantly affect the performance of a viscoelastic dielectric elastomer (DE). In the current study, we use a thermodynamic model to characterize the influence of temperature on the viscoelastic electromechanical response undergoing a constant electric load by taking into account the temperature dependent elastic modus and dielectric constant. Due to the significant viscoelasticity in the dielectric elastomer, DE membrane creeps in time and the inelastic stretch of DE is smaller than that of the total stretch. The results show that the total stretch of the viscoelastic electromechanical deformation increases with the increasing temperature until suffering electromechanical instability at a high temperature; the actuation performance is dominated by the moduli of the elastomer. This may be used to guide the design of dielectric elastomer actuators undergoing temperature variation.

Abstract: As a member of Electroactive Polymers (EAPs), dielectric elastomer (DE) has shown considerable potential for energy harvesting applications. After the basic principle of DE energy harvesting is studied, a multi-layer DE generator using VHB 4910 (3M, USA) is specially designed and fabricated. Then, an improved energy harvesting circuit is designed to make use of harvested electrical energy. Finally, energy harvesting experiments are implemented under the constant charge (open-circuit) condition and the results prove that the multi-layer DE generator fabricated can produce enough energy to constantly drive a light emitting diode. The harvested electrical energy has good consistent with generated electrical energy and the maximum energy harvesting efficiency ηh can reach 89%.

Abstract: Dielectric elastomer is a kind of electroactive polymer material with optimal performance. As actuator material, dielectric elastomer has shown a good prospect. Based on studying the principle of electroactive polymer, a new type of cylindrical actuator was designed. Its 3-D figure and 2-D dimension drawing was finished by UG software. The animation simulation of the actuator was studied. The simulation results verified the feasibility of design scheme. Electroactive polymer will have broad application prospects in the field of actuator.

Abstract: Elastomers have low elastic modulus, high specific energy density, light weight, high dielectric constant and high electrical breakdown strength. Due to these properties, elastomers are currently recognized as the future materials for actuator technology and actuators based on these materials are known as dielectric elastomer actuators (DEA). Based on Maxwell stress principle, these actuators transform electric energy directly into mechanical work. Modeling large actuation of this material depends on accurate estimation of E-modulus which varies with strain. In this work, E-modulus values at different strain are estimated based Mooney-Rivlin & Ogden Models. The model predicted values of E-modulus are compared with experimentally estimated values of E-modulus and found to be in good agreement.

Abstract: Among the broad class of electro-active polymers, dielectric elastomer actuators represent a rapidly growing technology for electromechanical transduction. In order to further develop this applied science, the high driving voltages currently needed must be reduced. For this purpose, one of the most promising and adopted approach is to increase the dielectric constant while maintaining both low dielectric losses and high mechanical compliance. In this work, a dielectric elastomer was prepared by dispersing functionalised carbon nanotubes into a polyurethane matrix and the effects of filler dispersion into the matrix were studied in terms of dielectric, mechanical and electro-mechanical performance. An interesting increment of the dielectric constant was observed throughout the collected spectrum while the loss factor remained almost unchanged with respect to the simple matrix, indicating that conductive percolation paths did not arise in such a system. Consequences of the chemical functionalisation of carbon nanotubes with respect to the use of unmodified filler were also studied and discussed along with rising benefits and drawbacks for the whole composite material.

Abstract: Thin metal films are not commonly used electrodes for dielectric elastomer actuators as it is a common presumption that they are too stiff to allow large actuated strains. However, using thin metal film electrodes can improve reliability due to their ability to self heal, as shown from their use in metalized plastic film capacitors. Typically, from literature, actuated area strains do not exceed 10% when using thin, un-patterned, metal films formed by sputtering. However, in this present work, large actuated area strains of up to 50% have been demonstrated. This was accomplished by using thin silver film electrodes formed by electroless deposition, and it has been noticed that micro-cracks were present in such electrodes. In this paper, micro-cracks in thin silver electrodes are studied and compared against sputtered silver electrodes. This includes the study of the manner in which they affect the magnitude of actuated strain and the repeatability of the actuator. It has been found that the cracks have helped to improve actuated strain, yet did not affect repeatability, as the cracks did not propagate in subsequent activations. Instead, the cracked electrodes had reached a sort of “steady-state”

Abstract: A kind of compact bending dielectric elastomer actuator is designed and manufactured using VHB4910 as the actuating material. In the contrastive experiments, the maximum displacement of 6.1mm can be achieved, and on the voltage differences of 0.9kv, the active bending of actuator is 8.1°. The research of dielectric elastomer actuator can provide an instruction for the design, analysis and implementation of this kind of actuator.