1. INTRODUCTION
Recently, polymers are emerging as promising substitutes for existing actuators. Among these the set of polymers actuated by electrical stimuli, called ElectroActive Polymer(EAP), are building up a new domain of actuators, though it includes several kinds of materials such as Ionic Polymer Metal Composites (IPMC), conducting polymer, polymer gel, dielectric elastomer, piezo electric polymer etc[1]. Normally EAPs are classified into two groups such as ionic and non-ionic EAPs, depending on the basic mechanism of actuation. In the current stage the non-ionic EAPs such as dielectric elastomer or piezo electric polymer are regarded very close to actual applications, though the others also have the possibility of being put into practical use in the near future. Dielectric elastomers are easily found around us, for instance, polyurethane and silicone are dielectric elastomers. Their basic types of deformation are expansion (active)/contraction (passive) which can be used in various ways for actuation[2], [3], [4], [5], [6]. In fact, the proposed actuator is able to accomplish the bidirectional actuation sincec it is antagonistically configured with a stretched film coated with compliant electrodes. In addition it is distinguished from the others with respect to the controllability of its compliance[6]. Bidirectional actuation and compliance controllability are important characteristics for the musclelike actuator and the proposed one satisfies the requirements without any mechanical substitute or complicated algorithms. In the former design[5], [6] the actuator is fabricated on a single film of dielectric elastomer, which gives several advantages such as the ease of fabrication, simplicity in design etc. However, it is vulnerable to the force orthogonal to the film surface. On the contrary, the proposed actuator, though it is based on the same principle as the previous one, uses a couple of films that are balanced along the direction orthogonal to the surface of the films. The design realizes not only rugged actuation, but also makes multiple DOF-actuation possible. In fact, the proposed idea can be implemented in various forms depending on the applications such as robots, active mechanisms etc. In this paper basic concepts of the proposed actuator are addressed. Also several practical implementations such as a single DOF-linear actuator fully packaged, and multiple DOF-actuator for actuating a micro camera are introduced.