Charge and Charge Density

Agnew et al. (1990) “Neural Prostheses: Fundamental Studies” p 226.

In this Figure, the abscissa and ordinate are related by electrode contact area, as shown by the labeled parallel lines. Two ‘k’ values are also shown.
The consensus is that to reduce neural damage, the operating areas should be in the lower left of the plot.

A sintered Tantalum Oxide electrode and a high-resolution micrograph of the surface are shown here. The sintered surface was an attempt to increase the total surface for current discharge above the geometric area.