Influence of shear on sensing of ionic polymer metal composites

Ionic Polymer Metal Composites (IPMCs) are laminate microstructures composed of an ionic electroactive polymeric membrane plated between two metal electrodes, finding application in actuation and sensing. The IPMC sandwich structure motivates an investigation on the effect of shear deformation on the IPMC behaviour. To reach this goal, we combine the electrochemomechanical framework recently proposed by Cha and Porfiri with the Yu-Krajcinovic structural theory, characterised by a zigzag warping in which the cross-sections of both membrane and electrodes undergo rotations independent of the mid-axis one. This results in an electrochemical response governed by a modified Poisson-Nernst-Planck (MPNP) system of equations nonlinearly modulated by both the curvature and the shear deformation of the membrane. By introducing the Parallel-Plate Assumption (PPA) and resorting to the method of matched asymptotic expansions, we semi-analytically solve the MPNP system and demonstrate, on the basis of a benchmark involving a distributed load, that shear deformation amplifies the sensing response. Our results are validated against two-dimensional continuum finite element simulations, which are further extended to the purpose of providing insight into the role of both the PPA and finite deformations in the presence of shear.