  We analyze the extracellular stimulation current and the charge injection
capacitity (CIC) of microelectrodes coated with an insulating layer to prevent
toxic electrochemical effects in bioelectronic applications. We show for a
microelectrode coated with an insulating ferroelectric layer, that the
ferroelectric polarization current contributes to the extracellular stimulation
current. Depending on the remanent polarization $P_{\rm r}$ of the
ferroelectric, the polarization current in the switching regime can increase
the CIC by up to two orders of magnitude as compared to the commonly used
extracellular capacitive stimulation with microelectrodes that are coated with
a dielectric layer.

Medical Physics