Polymers have many attractive characteristics; they are generally lightweight, inexpensive, fracture tolerant, and pliable. Further, they can be configured into almost any conceivable shape and their properties can be tailored to suit a broad range of requirements. Since the early 1990s, new polymers have emerged that respond to electrical stimulation with a significant shape or size change, and this progress has added an important capability to these materials. This capability of the electroactive polymer (EAP) materials is attracting the attention of engineers and scientists from many different disciplines. Since they behave very similarly to biological muscles, EAPs have acquired the moniker âartificial muscles.â Practitioners in biomimetics (a field where robotic mechanisms are developed based on biologically inspired models) are particularly excited about these materials since the artificial muscle aspect of EAPs can be applied to mimic the movements of animals and insects [Bar-Cohen and Breazeal, 2003]. In the foreseeable future, robotic mechanisms actuated by EAPs will enable engineers to create devices previously imaginable only in science fiction. One such commercial product has already emerged in December 2002: a form of fish robot (Eamex, Japan). An example of this fish robot is shown in Fig. 1. It swims without batteries or a motor and it uses EAP materials that simply bend upon stimulation. For power it uses inductive coils that are energized from the top and bottom of the fish tank. This fish represents a major milestone for the field, as it is the first reported commercial product to use electroactive polymer actuators.
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