  Ionic electro-active polymer (Nafion for example) can be used as sensor or
actuator. To this end, a thin film of the water-saturated material is
sandwiched between two electrodes. Water saturation causes a quasi-complete
dissociation of the polymer and the release of small cations. The application
of an electric field across the thickness results in the bending of the strip.
Conversely, a voltage can be detected between the two electrodes when the strip
is bent. This phenomenon involves multiphysics couplings of
electro-mechanical-chemical type. The system is modeled by a deformable porous
medium in which flows an ionic solution and we use a continuous medium
approach. Maxwell's equations and conservation laws of mass, linear momentum
and energy are first written at the microscopic scale for each phase and
interfaces, then for the complete material using an average technique.
Thermodynamics of linear irreversible processes provides the constitutive
equations : a Kelvin-Voigt stress-strain relation,generalized Fourier's and
Darcy's laws and a Nernst-Planck equation.
