Dielectric elastomers: Stretching the capabilities of energy harvesting
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uction Imagine the ability to generate electric power simply by stretching and relaxing a low-cost rubbery material. Such is the promise of electroactive polymers and, in particular, the type of electroactive polymer known as the “dielectric elastomer.” The term electroactive polymers (EAPs) typically refers to materials that can deform in response to the application of an electrical stimulus (although other mechanical responses are possible too). The many types of EAPs can be divided into two categories: ionic, where mass transport from a flowing charge causes the deformation; and electronic, where a voltage-induced electric field creates the deformation. Bar-Cohen1 and Carpi2 provide good reviews of EAPs. EAPs offer unique properties compared with more conventional transducer technologies, such as those based on rigid materials such as piezoelectrics, magnetostrictives, or electromagnetics. Because of the relatively soft polymer composition and large strain, response
can be similar to that of natural muscle; such EAPs are often called “artificial muscles” and find applications in biologically inspired robots, as well as human prosthetic or orthotic devices. Dielectric elastomers, a type of electronic EAP, have shown great promise for a variety of applications. Dielectric elastomer transducers are composed of deformable polymer films that respond to an electric field applied across their thickness. In a sense, they are stretchable capacitors. When acting as an actuator, dielectric elastomers are capable of large strains (in some cases >100%),3 with the relatively fast response and high efficiency associated with electric-field-activated materials.4 A number of materials, including relatively inexpensive, commercially available ones such as natural rubber, silicone rubbers, and acrylic elastomers, can be used for the component materials of dielectric elastomers. The elastomers can be quite soft, suggesting their potential for a variety of applications involving human interaction or unusual load-matching
Roy D. Kornbluh, SRI International, Menlo Park, CA 94025, USA; [email protected] Ron Pelrine, SRI International, Menlo Park, CA 94025, USA; [email protected] Harsha Prahlad, SRI International, Menlo Park, CA 94025, USA; [email protected] Annjoe Wong-Foy, SRI International, Menlo Park, CA 94025, USA; [email protected] Brian McCoy, SRI International, Menlo Park, CA 94025, USA; [email protected] Susan Kim, SRI International, Menlo Park, CA 94025, USA; [email protected] Joseph Eckerle, SRI International, Menlo Park, CA 94025, USA; [email protected] Tom Low, SRI International, Menlo Park, CA 94025, USA; [email protected] DOI: 10.1557/mrs.2012.41
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MRS BULLETIN • VOLUME 37 • MARCH 2012 • www.mrs.org/bulletin
© 2012 Materials Research Society
DIELECTRIC ELASTOMERS: STRETCHING THE CAPABILITIES OF ENERGY HARVESTING
requirements. The simple structure, wide availability, and unique properties of dielectric elastomers have allowed researchers to explore their use in a wide variety of actuator application
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