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Electroactive Polymers for Robotic Applications - Kim & Tadokoro (Eds.) Part 8

Tham khảo tài liệu 'electroactive polymers for robotic applications - kim & tadokoro (eds.) part 8', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Polypyrrole Actuators Properties and Initial Applications 133 Figure 5.8. Bilayer and trilayer actuation configurations. In bending bilayers and trilayers one layer expands whereas the other is passive or contracts leading to a bending motion. An example trilayer actuator is shown in Figure 5.9 41 . It is employed to create a camber change in a propeller blade. The structure generates 0.15 N of force. Bilayers have been shown to be very effective for microscale actuation and have been used by Elisabeth Smela and her colleagues to create contracting fingers cell enclosures moveable pixels and micro-origami. Micromuscle.com in Sweden is working to commercialize actuated stents and steerable catheters which appear to use the bilayer principle for operation 51 . Figure 5.9. Trilayer acutator mounted on a propeller blade. The top image shows the geometry of the blade the bottom two images show deflection of the structure. In the trilayers black two films of polypyrrole are separated by a sheet of paper soaked in gel electrolyte. A thin layer of polyethylene encapsulates the bending structure. Journal of Oceanic Engineering reproduced with permission 41 . 134 J. D. Madden Figure 5.4 shows the basic geometry of a linear actuator approach. As in all actuator configurations a counterelectrode and an electrolyte are required. Generally a mechanism must be available to allow transmitting force and displacement to the load. Thus the counterelectrode electrolyte and any packaging must not significantly impede actuation. Also the counterelectrode must accept a tremendous amount of charge from the polymer actuator which stores charge within its volume with an effective capacitance of approximately 100 Farads per gram of polymer. The counterelectrode is best made of a polymer that can itself absorb a lot of charge without requiring a large voltage or degrading the electrolyte. One of the simplest solutions is to employ a conducting polymer counterelectrode. In some cases with .