Synthesis and cyclic force characterization of helical polypyrrole actuators for artificial facial muscles

This study focuses on the synthesis and characterization of thick and thin film polypyrrole (PPy)-metal composite actuators for application as artificial muscles in facial robotics. The fabrication method consists of three steps based upon the approach proposed by Ding et al (2003 Synth. Met. 138 391-8): (i) winding the conductive spiral structure around the platinum (Pt) wire core, (ii) deposition of PPy film on the Pt wire core, and (iii) removal of the Pt wire core. This approach yielded good performance from the synthesized actuators, but was complex to implement due to the difficulty in implementing the third step. To overcome the problem of mechanical damage occurring during withdrawal of the Pt wire, the core was replaced with a dispensable gold coated polylactide fiber that could be etched at the end of deposition step. Experimental results indicate that thin film actuators perform better in terms of response time and blocking force. A unique muscle-like structure with smoothly varying cross-section was grown by combining layer by layer deposition with changes in position and orientation of the counter electrode in reference to the working electrode.