Current prostheses are not able to meet the needs of patients. The authors have recently been investigating the feasibility of integrating multiple types of electroactive polymers (EAP) to develop an artificial muscle for prostheses and muscle implants; much like biological muscle is made up of multiple types of muscle fibers. The intent is to produce a lightweight device which has smooth fluid-like motion, in contrast to the jerky motion of current prostheses which use heavy rotary actuators. A human arm model, isolating the bicep muscle, was developed to better understand the requirements on force and strain that an artificial muscle must meet to replace biological muscle. This study was conducted with the assistance of orthopedic surgeons from the Rochester General Hospital. Bicep muscle characteristics were compared with those of dielectric elastomer electroactive polymers (DEAP), since they produce relatively high force and large strain during actuation. Results show that current characteristics of DEAPs will not allow for direct substitution of human muscle fibers with EAPs because their force and strain outputs are too low. To increase the force and strain output of DEAPs to that of human muscle fibers, the stiffness of the DEAP needs to be increased. The analysis done and results obtained are discussed in the paper, as well as possible ways to increase the stiffness of EAPs to better meet the requirements for biological muscle replacement.

Electroactive polymers (EAPs) have been labeled as the future stakeholder for artificial muscle technology and machine actuation. The US Armed Forces have seen an increased population of service members suffering from loss of limbs as a result of conflicts overseas. Civilian populations have suffered as well, due to muscle tissue deterioration brought on by injury or disease. Many prosthetic limbs have been engineered with rotary actuation, but do not mimic fluid motion as human muscles do. Through the research of biomimetics, imitating nature and applying those techniques to technology, electroactive polymers have been found to produce the fluid-like characteristics of biological muscles as needed for precise artificial simulation. These materials exhibit common traits of biological muscle tissue regarding potential energy storage. When activated by an electrical voltage potential, EAPs can produce characteristics such as: bending/axial strain or changes in viscosity. One classification of electroactive polymers, Ionic EAPs, exhibit bipolar activation under low voltages and can be found in various physical states; solid, liquid, and gel states. These characteristics make Ionic EAPs the most attractive materials to be used in low energy or mobile applications, such as exoskeletons and implants. For high strain and large load applications, electronic EAPs can be used. Electronic EAPs require high voltages which induces high rates of strain and large deformations. To date, it appears that various types of EAP materials are being used individually, as opposed to integrated with other types. Biological muscles are made of many different proteins organized in an optimized geometrical structure which yields a more efficient response combined than achieved individually. The focus of the current project is to integrate multiple EAP materials in a designed mechanical system to produce a closer representation of a biological muscle. The status of this RIT project; to design, fabricate, and test an integrated EAP-based artificial muscle will be discussed along with the conceptual thinking for design obtained to date.