Dielectric elastomers

Dielectric elastomers are insulating, mbber-Uke structures, capable of undergoing reversible length change to a large extent and produce usable works. A dielectric elastomer actuator (DEA) works like an electrical motor by virtue of linear motion rather than rotation. 

A DEA is basically a compliant capacitor where an incompressible, yet highly deformable, dielectric elastomeric material is sandwiched between two complaint electrodes. The electrodes are designed to be able to comply with the deformations of the elastomer and are generally made of a conducting material such as a colloidal carbon in a polymer binder, graphite spray, thickened electrolyte solution, etc. Dielectric elastomer films can be fabricated by conventional... 

Actuators based on dielectric elastomer technology operate on a simple principle as shown in Figure 10.4. When an electric field is apphed to the electrodes, positive charges appear on one... 

The magnitude of Coulomb s force due to attraction between the positive and negative charges on the electrodes of the dielectric elastomer is given by the following equation ... 

FIGURE 10.5 Dielectric elastomer actuator (DBA) demonstrated to expand and relax in a circular strain test. The Maxwell s stress associated with the force is perpendicular to the apphed force and is given by... 

Arora has studied the importance of prestrain level of dielectric elastomers of silicone and PU, and a parabolic relationship has been established between the apphed electric field, the axial and radial... 

Table 10.5 gives a preliminary comparison of performance of dielectric elastomer with other acmator technologies. The reported values are collected from different sources and are not based on uniform measurement standards. ... 

Comparison of Properties of Dielectric Elastomers with Other Electroactive Materials... 

Source Liu, C. et at, Electro-statically stricted polymers (ESSP), SPIE Conference on Electroactive Polymer Actuator and Devices, Newport Beach, California, March 1999, SPIE Vol. 3669,0277-786X/99 Kombluh, R. et at, Application of Dielectric Elastomer EAP Actuators, SPIE— the International Society for Optical Engineering, Bellingham, Washington, 2001, Chapter 16. 

Another type of linear configuration known as bow-tie is shown in Figure 10.10. The actuator is constmcted using dielectric elastomer film having the shape of a bow-tie with two compliant electrodes configured on its two surfaces. Application of the electric field results in planar actuation which because of the bow-tie shape is translated into linear motion. Typical applications of these types of actuators comprise a hexapod robot, to mimic the motion of insects like walking, to manufacture various animated devices like face, eyes, skin, etc., or the design of micro-air vehicle/omithopter. 

FIGURE 10.13 Basic mechanism of dielectric elastomer actuator (DEA) generator. (From Kombluh, R., Power from plastic How electroactive polymer artificial muscles will improve portable power generator in tbe 21st century military, Presented at TRI-Service Power Expo, Norfolk, Virginia, July 2003. With permission.)... 

In addition to heel-strike generator and polymer engine other inexpensive possibilities of power generation due to human motion using dielectric elastomer are depicted in Figure 10.15. 

Other efforts which could be made are to put these dielectric elastomer generators on the suspensions of automobiles to aid in the electricity use during operation. This would make things easier on the charging system of the automobile which could possibly save fuel consumption. 

Prahlad et al. have described the configuration of dielectric elastomer generators for conversion of wind or wave energy to produce localized electrical power and also suggested the relevance of this work to rural or other remote areas to fulfill their power requirement where existence of a rehable and centralized power stiU remained a distant possibility. 

Carpi, F., Chiarelli, P., Mazzoldi, A., and De Rossi, D., Electromechanical characterisation of dielectric elastomer planar actuators Comparative evaluation of different electrode materials and different counterloads, Sensors Actuators, A107, 85, 2003. 

Pelrine, R., Kombluh, R., and Kofod, G., High strain actuator materials based on dielectric elastomers, J. Adv. Mater., 12, 1223, 2000. 

Scarborough, D., Dielectric elastomers, demonstrated on the website http /www.engr.siu.edu/mech/ faculty/hippo/ME465SP05ScarboughDielectricElastomersorElectroactivePolymers.doc... 

Arora, S., Development of dielectric elastomer based protot)fpe fiber actuator. Masters thesis submitted to North Carolina State University, July 2005. 

Kofod, G., Dielectric elastomer actuator, Ph.D thesis submitted to Technical University of Denmark, Sept. 2001. 

Toth, L.A. and Goldenburg, A.A., Control system design for a dielectric elastomer actuator The sensory subsystem, smart stmctures and materials 2002, in Electroactive pol3mier actuators and devices, Y. Bar-Cohen (Ed.), Proceedings ofSPIE, Vol. 4695, 0277-786X/2002. 

Carpi, F. and Rossi, D.D., Dielectric elastomer cylindrical actuators Electromechanical modeling and experimental evaluation, Mater. Set Eng., C24, 555, 2004. 

Kombluh, R.D., Flamm, D.S., Vujkovic-Civijin, P., Pelrine, R.E., and Huestis, D., Large fight weight mirrors control by dielectric elastomer artificial muscle, AAS 200 meeting, Albuquerque, NM, June 2002, Paper no. 63-06. 

O Halloran, A. and O MaUey, F., Dielectric elastomer actuators in the development of mechanotronic muscle, NUI, Galway faculty of engineering research day, 2004. 

Prahlad, H., Kombluh, R., Pelrine, R., Stanford, S., Eckerle, J., and Oh, S. Polymer power Dielectric elastomers and their applications in distributed actuation and power generation. Proceedings of ISSS International Conference on Smart Materials, Structures and Systems, Bangalore, India, July 28-30, 2005, SA-13, pp. 100-107. 

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