Dielectric Elastomers

1
Dielectric Elastomers

• AE 510 Research Project Presentation
• By Carl Johnson
• October 22, 2002

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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
3
Governing Equation of Dielectric Elastomers

• pee0E2
• 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

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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

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Dielectric Elastomer Comparison Chart
Shape Memory Alloys
Piezoelectrics
Dielectric Elastomers
Note Similarity of Dielectric Elastomers and
Natural Muscle
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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)

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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)

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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/brie
  fings/5sri.pdf
•  
• Zorpette, Glenn. Fly on the Wall. Red Herring
  Magazine. October 2000.