3D modelling of a hydro gel sheet - electrode array combination for surface functional electrical stimulation

This paper describes a 3D finite element model, which is being used to optimise the design of a self-adhesive electrode array for functional electrical stimulation (FES). The D model was built using ANSYS and used to calculate the current density distribution in tissues in the vicinity of the electrodes. The stimulating function, which is critical for nerve excitation, was then obtained. A series of hydrogel sheets with different resistivities, which were intended to ease application and removal of the electrode array, were tested in the model. The tissue volume with a stimulating function higher than the stimulation threshold of the target nerve formed a half-ellipsoidal pool. The D model is a useful tool to determine and optimise the spatial selectivity of the electrode array. The model demonstrated that for a 1mm thick hydrogel interface a minimum resistivity of 500Ωm is required to maintain selectivity.