Electroactive polymer

Remarks

Example: a dielectric elastomer film of thickness $d$ with compliant electrodes on both faces. A voltage $V$ across the film gives an electric field $E = V/d$. The attraction of the electrodes acts as an effective pressure $p = \varepsilon_0 \varepsilon_r E^2$ on the film, where $\varepsilon_0$ is the vacuum permittivity and $\varepsilon_r$ the relative permittivity of the polymer. The film is a polymer and it deforms reversibly under the field, so it satisfies the definition.

Non-example: a ceramic piezoelectric crystal such as lead zirconate titanate also deforms under an electric field, but it is not a polymer.

The terms "artificial muscle" and "EAP" are common names for these materials.