MRS Proceedings

Articles

Long-lifetime All-polymer Artificial Muscle Transducers

2010 MRS Spring Meeting.

Roy Kornbluha1, Annjoe Wong-Foya2, Ron Pelrinea3, Harsha Prahlada4 and Brian McCoya1

a1 roy.kornbluh@sri.com

a2 annjoe.wongfoy@sri.com, SRI International, Menlo Park, United States

a3 ron.pelrine@sri.com, SRI International, Menlo Park, United States

a4 harsha.prahlad@sri.com, SRI International, Menlo Park, United States

a5 brian.mccoy@sri.com, SRI International, Menlo Park, United States

Abstract

The dielectric elastomer, a particularly attractive type of electroactive polymer, uses commercial polymers such as acrylic and silicone elastomers. The technology has been limited in application by perceived lifetime issues. By addressing several lifetime issues, lifetimes of more than one million cycles, and in some cases beyond ten million cycles, were achieved with a variety of transducer configurations (including operation in generator mode) under a variety of operating conditions (including high humidity). Dielectric elastomers can produce maximum actuation strains of more than 100% and specific energy density exceeding that of known electric-field induced technology. Performance testing for dielectric elastomer actuators has typically been for peak-performance or “over-driven” conditions with short operational lifetimes (typically 100s or 1000s of cycles), particularly under conditions such as high humidity. By minimizing electric field and mechanical strain concentration factors, long lifetimes (>1 million cycles) with acrylic transducers were achieved with actuation strains as great as 40% areal strain (and up to 100% areal strain in generator mode). Actuators in a dry environment had an almost 20x increase in lifetime over actuators at ambient humidity (about 50% RH) at the same driving field conditions. Long actuation lifetimes were also achieved in a 100% RH environment and when fully submerged in salt water at reduced operating strain and field. In 100% RH, lifetimes of several million cycles were achieved at 4% strain. In underwater operation, 6 out of 11 actuators survived for >10 million cycles with an electric field limited to 32 MV/m and approximately 2% strain. The demonstrated lifecycle improvements are applicable to a variety of uses of dielectric elastomers, including haptic interface devices, pumps (implantable and external), optical positioners, and “artificial muscles” to replace small damaged muscles. Continued improvements in materials, actuator design, and packaging, combined with management of operational conditions as described here, should support new practical application of this promising technology.

(Received September 23 2010)

(Accepted September 24 2010)

Key Words:

  • actuator;
  • dielectric properties;
  • energy generation
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