Conducting polymer actuator enhancement through microstructuring

Abstract

Electroactive conducting polymers, such as polypyrrole, polyaniline, and polythiophenes are currently studied as novel biologically inspired actuators. The actuation mechanisms in these materials are based on the diffusion of ions in and out of the polymer film. Giving ions more access to the center of the films by inducing holes on its surface can improve strain rates. A unique surface templating technique using breath figures has been developed for poly (3-hexylthiophene). Spherical holes form on the surface of polymer films during the drop casting process if moist air was blown over the top of the film. This technique has been used to generate 0.8-5 /m holes on the surface of poly(3-hexylthiophene) films. It can also be used to create columns 3 to 10 /tm in height in polypyrrole. Free standing spongy films (10-35 iLm in thickness) of poly(3-hexylthiophene) were generated using this technique and the influence of the additional surface area on the actuation of poly(3-hexylthiophene) and polypyrrole films has been characterized.

(cont.) Actuation seen in poly(3-hexylthiophene) films was not characteristic of actuation seen in polypyrrole or in poly(3,4-ethylenedioxythiophene). Poly(3-hexylthiophene) shows a voltage dependant on-off mechanism as well as a non charge dependant actuation mechanism. This has been primarily attributed to the change in the polymer modulus during the actuation cycle. The subsequent part of this thesis begins the development of linear system identification techniques to track the effect of the changing modulus during actuation.