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The effect of film thickness on polypyrrole actuation assessed using novel non-contact strain measurements

Micro-actuators have been developed that exploit the electrochemically induced volume change of the electro-active polymer polypyrrole. The strain regime is inherently complex at a physical level and whilst volume change can be estimated indirectly using, for instance, bending beam theory, such methods become unreliable for large deflections owing to limitations in the mathematical model. A new non-contact measuring technique based on laser micrometry is presented to characterize the time-dependent expansion of electro-active films such as polypyrrole. Measurements have been made which demonstrate that the observed strain is dependent on film thickness. The new measurement technique is straightforward to perform and it is anticipated that it can be used for future materials development and performance assessment, including long-term stability evaluations and operational failure studies of the films.