Ongoing in vitro pulse tests of the oxide grown with this method are showing that the activated sites maintain their electrical characteristics over at least 100 million pulses. Q cap is calculated by integrating the area under the CV curve. This measurement and calculation should be made every 50-100 activation cycles in order to determine when the specified Q cap is reached. A ramp wave is still used to calculate Q cap, even though a square wave is used for activation. Activated iridium has characteristics that make it an attractive material for electrical stimulation of neural tissue.
Iridium can store charge by going through valence changes which cause reversible redox reactions.
The fact that these reactions are reversible is important for biocompatibility. The state of the iridium will depend on the potential applied across the metal-electrolyte junction. However, neural stimulation is usually accomplished with a constant current source, so the voltage applied is dependent on the charge storage of the oxide. This reaction defines the water window on the positive voltage side. Only a small portion of the total charge storage capacity of the Iridium oxide is used in current pulsing.