Electroactive Polymers (EAP)

Electroactive polymers (EAP) represent a relatively new (as compared with Nitinol) class of smart materials. EAPs can exhibit very high deformations coupled with low forces and are classified in two forms, dielectric and ionic based.  

In the dielectric form polymers are layered with electrodes and a voltage is applied, the electrostatic forces then lead to deformation of the material. Dielectric EAPs therefore rely on the electrostatic forces between electrodes to induce actuation by expansion of the polymer layer. When a high voltage is applied electrostatic attraction between the electrodes leads to an expansion in the plane of the actuator.

Ionic EAPs function via the displacement of ions in the polymer. The required driving voltages are generally on the order of a few volts, less than that required for dielectric EAPs. However, a larger driving current is required. Common applications for EAPs include artificial muscles, body sensors, and peristaltic pump designs. Due to the viscoelastic nature of the base polymer material, EAP actuators generally exhibit low response times.

At the present time, the commercialization of EAP materials is not sufficiently advanced to provide a characterized material source to be considered for a smart materials characterization study. The long-term reliability of EAP actuators is also a concern, dielectric actuators need to be pre-stressed but degradation of the pre-stress stiffness can occur. The advent of new polymers will no doubt lead to improvement in EAP designs and reliability.