Actuation of polypyrrole nanowires

Abstract

Nanoscale actuators are essential components of the NEMS (nanoelectromechanicalsystems) and nanorobots of the future, and are expected to become a major area ofdevelopment within nanotechnology. This paper demonstrates for the first time thatindividual polypyrrole (PPy) nanowires with diameters under 100 nm exhibit actuationbehavior, and therefore can potentially be used for constructing nanoscale actuators. PPyis an electroactive polymer which can change volume on the basis of its oxidation state.PPy-based macroscale and microscale actuators have been demonstrated, but their nanoscalecounterparts have not been realized until now. The research reported here answerspositively the fundamental question of whether PPy wires still exhibit useful volumechanges at the nanoscale. Nanowires with a 50 nm diameter and a length of approximately6 µm, are fabricated by chemical polymerization using track-etched polycarbonatemembranes as templates. Their actuation response as a function of oxidation state isinvestigated by electrochemical AFM (atomic force microscopy). An estimate of theminimum actuation force is made, based on the displacement of the AFM cantilever.