Electroactive polymers as an enabling materials technology

Natural muscles are the actuators in most of the biological systems that are larger than a bacterium. The drive mechanism of muscles is complex, and they are capable of lifting large loads with short time response in the range of milliseconds. Electroactive polymers (EAPs) are human-made actuators that most closely emulate biological muscles, and therefore they earned the moniker 'artificial muscles'. Initially, EAPs received relatively little attention because of their limited actuation capability. In the last 15 years, a series of EAP materials have emerged that exhibit a significant shape change in response to electrical stimulation. Using these materials as actuators, various novel mechanisms and devices were already demonstrated, including robot fish, catheter steering element, miniature gripper, loudspeaker, active diaphragm, and dust wiper. The impressive advances in improving their actuation strain capability are attracting the attention of engineers and scientists from many different disciplines. These materials are particularly attractive to biornimetic applications, because they can be used to make biologically inspired intelligent robots and other mechanisms. Increasingly, engineers are able to develop EAP-actuated mechanisms that were previously considered science fiction. This article reviews the state-of-the-art challenges and potential applications of EAP materials.