Simulation of the field density of the used electrodes.

<p>Using the Finite Element Method (FEM) the distributions of currents are visualized for (<b>A</b>) a flat gel electrode that can be used for TENS, (<b>B</b>) a concentric electrode, and (<b>C</b>) a matrix array electrode. Assuming an ohmic skin resistance and isotropic electrical properties of skin and underlying tissue, only the matrix array and concentric electrodes showed high current densities preferentially distributed across superficial layers of the skin. The gel electrode showed at least 7 times smaller maximum current densities with a much deeper current distribution. Note the different scaling of the colour codings of current densities as well as the penetration depths.