Polypyrrole Soft Actuators

Organic soft actuators attract strong attentions because they have many advantages compared to conventional mechanical actuators. Organic soft actuators are generally light and flexibly deformed. In addition, they operate under low voltage ranges as low as 1 volt or so, and generate no sound during deformation. Amongst those soft actuators, bending soft actuators are of special interest because small volume change in organic materials can cause a large bending displacement. For example, soft actuators consisting of Ionic Conducting Polymer Films (ICPF) have been widely used as bending actuators (Guo et al., 1996). However, the fabrication processes for ICPF actuators seem complicated. In contrast, polypyrrole films synthesized using electropolymerization as a new material for organic soft actuators have been extensively studied (Hara et al., 2004a, 2004b, Hatchison et al., 2000, Jager et al., 1999). In addition, the amount of the volume change can be modified by altering the electropolymerization conditions. Hara et. al. recently reported that the expansion and contraction ratio of their polypyrrole actuators exceeded 40%, which is very encouraging (Hara et al., 2005). Bending actuators can be easily fabricated by forming a bimorph structure consisting of a polypyrrole film and other film material. In this section, simple bimorph actuators using an electropolymerized polypyrrole (PPy) film and a both-side adhesive tape were fabricated. It turned out that those actuators nonuniformly bent depending on the distance between the actuator and the counter electrode. We fabricated a structure consisting of polypyrrole/both-side adhesive tape/polypyrrole whose two polypyrrole films have different extension/contraction ratios, and found that the actuator exhibited more uniform bending deformation which was nearly independent of the distance between the electrodes.