Ionic polymer conductor network composite (IPCNC) is a mixed conductor consisting of a network of loaded ionomer and another network of metallic particles. It is known that the microstructure of the composite, especially that of the electrodes, plays a dominating role in the performance of an IPCNC. However the microstructures of IPCNC have seldom been addressed in theoretical models. This letter formulates a continuum field theory for IPCNC by considering a supercapacitor-like microstructure with a large distributed interface area. The theory is then applied to the study of the equilibrium deformation and electrochemistry in a thin-sheet IPCNC actuator.

Ionic polymer-metal composite (IPMC) is a polyelectrolyte (usually Nafion or Femion swollen by simple salt solution) strip or membrane with both sides plated with metal electrodes. It is a particular design of electroactive-polymer device rather than a new class of material. When a voltage is applied between its electrodes, it will bend toward either electrode depending on the polarity (anode for a negatively charged gel), and the magnitude of deformation could be controlled by the electric signal.  Reversely, the deformation of an IPMC can generate electric signal or even energy output [1-4].  Therefore IPMC has recently becomes a hot topic in actuation, sensor and energy harvesting applications, especially when integrated with the characteristics of certain gels that are responsive to other environmental stimuli such as pH value or temperature.