Abstract: Ion-exchange Polymer-Metal Composites (IPMCs) gain huge attentions due to large deformation, rapid electromechanicalresponse, and high energy conversion efficiency. Deflection of IPMC arises from the volumetric swelling effect inducedby the concentration gradient of hydrated cations between the two electrodes, thus the volume of hydrated cation determines the motion magnitude and direction of IPMC. H ion is one of the most commonly used driving cations for IPMC.However, due to its unique characteristics, particularly the inability to accurately quantify its hydration volume, existingliteratures primarily focus on the physical driving models for metallic cations, i.e., Na+, no driving model for the H ionis reported until now. This paper proposes a novel model of H ion escape from the water’s body-centered cubic lattice tocount the hydration volume. Number (n) of water molecules carried by the H ion is solved by combining the LennardJones potential energy function with Maxwell’s velocity distribution. The specific n value is equivalent to 4.04 for the Hion inside Nafion electrolyte under a 3.0 V DC electric field. Substituting it into the classic Friction Model (proposed byTadokoro et al. at 2000), actuation behaviors of H ion driven IPMC were therefore achieved through Matlab calculationsand Abaqus simulations. The calculated results of dynamic displacement and force highly match to the experimental dataform the Nafion IPMC actuator driven by same electric field, showing a highly reliability of the established escape model.

Key words: IPMC, Friction model, Electromechanical coupling, Number of coordinated water molecules, Bodycentered cubic')">IPMC, Friction model, Electromechanical coupling, Number of coordinated water molecules, Bodycentered cubic