Dielectric Elastomers AE 510: Research Project Presentation By: Carl Johnson October 22, 2002
How Dielectric Elastomers Work • Dielectric Elastomers have a polymer (aka plastic) film between two electrodes • When an electric field is induced between the electrodes the electrostatic forces cause a change in shape (see figure) Ref. 1
Governing Equation of Dielectric Elastomers p=e*e0*E2 • Where: • p is effective compressive stress • e is relative dielectric constant • e0 is permittivity of free space (a constant) • E is strength of electric field between diodes
Advantages of Dielectric Elastomers • Similar materials include: • Shape memory alloys (SMA) • Piezoelectrics • Compared to these dielectric elastomers have: • Higher energy density • Lower weight • Higher efficiencies • Higher maximum strains
Dielectric Elastomer Comparison Chart Shape Memory Alloys Piezoelectrics Dielectric Elastomers Note Similarity of Dielectric Elastomers and Natural Muscle
Applications: Actuators • Dielectric elastomers are well suited to actuators • Their similarity to natural muscle makes them ideal for use on robots (see right) • They could also be used to motivate insect-like micro UAVs • Dielectric elastomers could be used for human prostheses and make the six million dollar man a reality (see title slide)
Applications: Heel-Strike Generator • DoD is using dielectric elastomers to develop a heel-strike generator to go in soldiers boots that would generate electricity just from walking • A dielectric elastomer generator works like an actuator in reverse (mechanical-to-electrical instead of electrical-to-mechanical energy)
References: • Pelrine, Ron et al. “High Strain Actuator Materials Based on Dielectric Elastomers.” SRI International. 2000. • Wingert, Andrew et al. “Hyper-Redundant Robot Manipulators Actuated by Optimized Binary Dielectric Elastomers.” Smart Structures and Materials Symposium 2002. • http://ndeaa.jpl.nasa.gov/nasa-nde/lommas/eap/EAP-web.htm. SRI International Comparison Tables/Charts. 2002. • Bar-Cohen, Yoseph. “Electroactive Polymers as Artificial Muscles – Capabilities, Potentials and Challenges.” Robotics 2000 and Space 2000. Albuquerque, NM. 2000. • Pelrine, Ron. And Kornbluh, Roy. “Recent Progress in Heel-strike Generators using Electroactive Polymers.” www.darpa.mil/dso/thrust/md/energy/briefings/5sri.pdf • Zorpette, Glenn. “Fly on the Wall.” Red Herring Magazine. October 2000.