Electroactive-polymer actuators with selectable deformations

NASA Tech Briefs, Jul 2002

There are numerous options for selecting materials, configurations, and modes of operation. NASA's jet Propulsion Laboratory, Pasadena, California

Efforts are underway to develop compact, lightweight electromechanical actuators based on electroactive polymers (EAPs). An actuator of this type is denoted an electroactive-polymer actuator with selectable deformation (EAPAS). The basic building blocks of these actuators are sandwichlike composite-material strips, containing EAP layers plus electrode layers, that bend when electric potentials are applied to the electrodes. Prior NASA Tech Briefs articles that have described such building blocks as parts of actuators for specific purposes include "Robot Hands With Electroactive-Polymer Fingers" (NPO-20103), Vol. 22, No. 10, (October 1998), page 78; "Robot Arm Actuated by Electroactive Polymers" (NPO-20393), Vol. 23, No. 6 (June 1999), page 12b; "Wipers Based on Electroactive Polymeric Actuators" (NPO-20371), Vol. 23, No. 2 (February 1999), page 7b; and "Miniature Electroactive-Polymer Rakes" (NPO-20613), Vol. 25, No. 10 (October 2001), page 6b.

The EAPAS concept admits of almost endless variations in the selection of materials, actuator configurations, and modes of operation; it must suffice here to present only a few illustrative examples. EAPs that can be used in EAPASs include electronically conductive, ion-exchange, ferroelectric, and electrostrictive polymers; graft elastomers; ferrogels; and possibly others. An EAPAS can comprise one or more pairs) of bender strips placed back-to-back and stacked in a parallel, serial, or parallel/serial arrangement (see figure), as needed to satisfy force and displacement requirements for a given task. The following are a few examples of options for design and operation:

* The pairs of benders in a given EAPAS can be electrically addressed individually, all together, or in intermediate combinations to control the displacement and/or shape of the EAPAS.

* Stacked benders can be enclosed in a protective case, effectively rendering an EAPAS a compact linear motor.

* EAPASs can be embedded in deformable "smart" structures for controlling their shapes.

* An EAPAS designed mainly as a contractile actuator (in other words, a puller) could serve as an artificial muscle: for this purpose, it would be anchored at one end and would pull on a wire (which would serve as an artificial tendon) at the other end.

* A more complex EAPAS could serve as a tactile display device.

This work was done by Yoseph Bar-Cohen of NASA's Jet Propulsion Laboratory, Virginia Olazabal of Caltech, and Jose-Maria Sansinena of San Sebastian, Spain. For further information, access the Technical Support Package (TSP) free on-line at www.nasatech. com/lt under the Mechanics category.

In accordance with Public Law 96-517, the contractor has elected to retain title to this invention. Inquiries concerning rights for its commercial use should be addressed to

Intellectual Property group JPL Mail Stop 202-233 4800 Oak Grove Drive Pasadena, CA 91109 (818) 354-2240

Refer to NPO-211 74, volume and number of this NASA Tech Briefs issue, and the page number.