Mechanoelectric effects in ionic gels

Certain fluorinated ion-exchange membranes, when swollen and suitably plated by conducting electrodes, display a spontaneous curvature increasing with the applied field E (1). There is also an inverse effect, where an imposed curvature induces an electric field (in open circuit conditions). We present here a compact description of these effects in the linear regime, and in static conditions: this is based on linear irreversible thermodynamics, with two driving forces (E and a water pressure gradient ∇ p) and two fluxes (electric current and water current). We also give some qualitative estimates of the three Onsager coefficients which come into play. 1