Finite element analysis of a microelectrode on a substrate.

Analytical solutions for the voltage field generated by a microelectrode are available for simple electrode and volume conductor geometries. However, the practical microelectrodes fabricated on a planar substrate deviate from those simple geometries substantially. It needs to be determined in which cases the analytical methods can be employed without introducing significant errors. We developed a finite element model (FEM) to study the potential field generated in a volume conductor by a circular disk electrode etched into a planar substrate. The results were compared to that of an analytical model provided by Wiley and Webster. The peak voltage at the contact surface varies as a function of the substrate width and it reaches 90% of the maximum at about twice the contact diameter. This suggests that an FEM is required for narrow substrate widths. The effect of the intercontact distance for the bipolar electrodes is also studied.