Continuum electromechanics of ionic polymeric gels as artificial muscles for robotic applications

A continuum electromechanical theory is presented for the dynamic deformation of ionic polymeric gels in the presence of an imposed electric field. The proposed theory is based on some recent experimental results for the deformation of ionic polymeric gels and in particular polyacrylic acid plus sodium acrylate cross-linked with bisacrylamide (PAAM). The proposed model takes into account the electro-osmosis, electrophoresis and ionic diffusion of various species. It further considers the spatial distributions of cations and anions within the gel network before and after the application of an electric field. The model derives exact expressions relating the deformation characteristics of the gel as a function of electric field strength or voltage gradient, gel dimensions and gel physical parameters. Direct electrical and computer control of the expansion and contraction of these polymeric ionic gels is possible because ionic polymeric gels are electromechanical in nature.