Fabrication and use of conducting polymer linear actuators

Abstract

The development of biomimetic devices will benefit from the incorporation of actuators with combinations of properties common to biological systems, for example low density, controllable mechanical flexibility, and compact size. Conducting polymers, such as polypyrrole, exhibit muscle-like properties and the potential to provide the above capabilities while delivering significant forces over useful displacements. Current conducting polymer linear actuators, however, are generally limited to displacements of less than 0.5 mm, forces of less than 1 N, and cycle frequencies of less than 0.1 Hz. These materials are rarely tested on a length scale of more than a few millimeters, and their incorporation into real applications has to date been limited. This work focuses on improving and scaling conducting polymer linear actuators for application in macroscale systems. A new fabrication method is described that delivers polypyrrole ribbons with uniform thicknesses of 10 to 30 [mu]m, widths of 20 [mu]m to 20 mm, and lengths exceeding 5 m. A second method is described where a conductive gold layer is incorporated into the ribbons and is shown to enhance performance and mitigate limiting effects common to longer conducting polymer actuators. Additionally, parallel actuation is explored as a method to achieve greater forces without compromising actuation speed. The integration of these actuators into stand alone systems that include joints and flexures has yielded novel techniques in amplifying motion while minimizing friction, improving electrical connection, and increasing actuator lifetime. The challenges of incorporating these actuators into an example biomimetic system are discussed and an approach is introduced. These methods and systems are shown to have increased conducting polymer linear actuator displacement output, force output, and actuation speed each by a full order of magnitude, thus bringing this technology closer to practical incorporation and use in biomimetic systems.