Electroactive Polymer Actuation at the Nanoscale

Nanoscale actuators are required for the development of nanorobots and other nanoelectromechanical systems (NEMS) of the future. Actuators based on electrochemically-induced volumetric changes in electroactive polymers (EAPs) have been demonstrated at the macro and microscales, and have been used for artificial muscles and other applications. Here we experimentally and quantitatively demonstrate for the first time that the fundamental phenomena underlying EAP actuation are still active at spatial scales below 100 nm. This opens new directions in nanorobot and NEMS research. Individual polypyrrole structures are investigated in this paper by using atomic force microscopy (AFM) with electrochemistry capabilities. Polypyrrole-based nanowires (~50 nm diameter, ~6 μm in length) and single-walled carbon nanotubes coated with a polypyrrole film ~125 nm thick both show actuation behavior. The nanowire dimensions change from ~2% to as much as ~35%. The single-walled nanotube-polypyrrole structures show a considerably lower percentage of dimensional change.