Electroactive Polymer Transducers Elastomeric polymer materials have demonstrated promise for a variety of actuator and electric power generation applications. The key design feature of devices based on these materials is the use of compliant electrodes that enable polymer films to expand or contract in the in-plane directions in response to applied electric fields or mechanical stresses. We have developed devices that have produced strains in excess of 100%, pressures greater than 100 psi, and specific energy densities exceeding those of all known field actuated materials (such as piezoelectrics and magnetostrictive materials) in response to an applied voltage. These same polymers have produced electric power in response to large deformations with high coupling efficiency and high energy density.

The good electromechanical response of these materials, as well as other characteristics such as good environmental tolerance and long-term durability, suggest a wide range of possible applications. Those under active investigation include acoustic actuators for smart skins; microactuators for micropumps and valves; “artificial muscle” actuators for biomorphic walking, flying, and serpentine robots; and power generators for converting human motion and other mechanical work into electricity.

Flapping Wing Propulsion We are applying our electrostrictive polymer actuators to design and build micro air vehicles (MAVs) that are propelled by bird-like wings. As in nature, flapping wings are more energy efficient at smaller scales than conventional propeller-driven devices. In partnership with aerodynamic specialists at the University of Toronto, we are developing technologies for MAVs that will be useful for indoor and outdoor reconnaissance and surveillance missions.

Video of early electric motor prototype of a flapping wing MAV that is capable of sustained hovering flight.

Dexterous Multiarticulated Manipulator with EPAM Actuators This project is funded by the Office of Naval Research (ONR). The goals of the project are to further develop the electrostrictive polymer technology for application in a new generation of robotic actuators. Such actuators might be used, for example, to develop a multiarticulated (snake-like) robot for manipulation and inspection in cluttered workspaces. The challenges in this project are to design and fabricate reliable actuators with sufficiently large force and stroke. We have demonstrated new fabrication techniques for larger actuators, and several new actuator designs. These designs include a spherical joint powered by a triad of rolled actuators and rotary motor that converts resonant oscillations of the artificial muscle to rotation in an efficient manner. In this project we have also investigated the development of improved polymer materials for the electrostrictive polymer technology. A number of promising new electrostrictive materials have been identified and are under study.

Artificial Muscle for Small Robots SRI has been developing artificial muscle actuators for small mobile robots (on the order of 1.0 cm in size) and other micro machine applications. The work is sponsored by the New Energy Development Organization (NEDO) of MITI of Japan. SRI is a member of the Micro Machine Center (MMC), which oversees this work. We began the project by examining a wide range of candidate actuation technologies and focuses on electrostrictive polymers as the most promising approach, further developed this technology, and demonstrated its potential for exceptional actuator performance with experimental results. We have demonstrated good performance with many actuator configurations including stacks, rolls, tubes, unimorphs, bimorphs, diaphragms, and inchworm-like devices. We are continuing to develop new actuator designs and improve the performance and reliability of the existing ones.