Fast trilayer polypyrrole bending actuators for high speed applications

The synthesis and performance evaluation of trilayer bending type polymer actuators in terms of frequency response and step response are described. The actuators are shown to achieve mechanical resonance at up to 90 Hz and giving tip displacements up to 60 mm for an input voltage of ±1 V at 4 Hz. Polypyrrole doped with trifluoromethanesulfonimide (TFSI) had a considerably higher speed of response when compared to polypyrrole-hexafluorophosphate (PF6) actuator with the same dimensions. The TFSI doped polypyrrole showed faster charging rates, likely due to higher ion diffusion rates through a gel-like polymer structure, thereby producing faster actuation response. These new actuators may be useful for applications requiring a high speed of response, e.g. a propulsion element for a swimming device/robotic fish.