Multiphysics simulation of parametric effects on IPMC actuation dynamics and back-relaxation

Abstract Ionic polymer–metal composites (IPMCs) are a type of smart material capable of large, reversible deformation under low applied voltage. Their flexibility, biocompatibility, and ability to perform underwater make them promising candidates for soft robotics and biomedical devices. However, their application is often limited by their low actuation force and back-relaxation under constant voltage. While many efforts have been made to optimise the performance through material and geometry alteration, a comprehensive investigation of how specific material properties influence the actuation dynamics remains limited. This study attempts to investigate how material parameters and electrical input can influence the actuation behaviour of IPMCs using multiphysics simulation. A 2D finite element model, with consideration of coupled ion–water transport and mechanical deformation, was used to analyse the role of transport (diffusivity, permeability), electrical (dielectric constant), and mechanical (elastic modulus) properties on the actuation performance. Results show that transport-related parameters predominantly affect the transient response, while others influence both transient and steady-state displacement. Specifically, increasing the dielectric constant and diffusion coefficient enhances overall deformation, whereas greater hydraulic permeability and elastic modulus tend to suppress it. Additionally, voltage studies revealed that combining a high AC amplitude with a low DC bias can reduce back-relaxation without compromising actuation performance. These findings clarify the individual roles of material parameters in IPMC deformation dynamics and provide potential voltage modulation strategies to mitigate back-relaxation and improve long-term stability.