Muscle-like actuators? A comparison between three electroactive polymers.

Muscles fulfill several functions within an animal's body. During locomotion they propel and control the limbs in unstructured environments. Therefore, the functional workspace of muscle needs to be represented by variables describing energy management (i.e. power output, efficiency) as well as control aspects (i.e. stiffness, damping). Muscles in the animal kingdom vary greatly with respect to those variables. To study if ElectroActive Polymer's (EAP) can be considered as artificial muscles we are making a direct comparison between the contractile properties of EAP's and biological muscle. We have measured the functional workspace of EAP actuators using the same setup and techniques that we use to test biological muscle. We evaluated the properties of three different EAP materials; the acrylic and silicone dielectric elastomers developed at 'SRI International' and the high-energy electron-irradiated co-polymers (P(VDF-TrFE)) developed at the MRL laboratory at Penn State University. Initial results indicate that the EAP materials partly capture the functional workspace of natural muscle and sometimes even exceed the capabilities of muscle. Based on the data we have collected it seems that both EAP technologies have characteristics that could qualify them as artificial muscles.