2.4. Iridium Oxide (IrO2) Coating

To make the solution for IrO₂ coating, 300 mg of the iridium chloride was added to 200 mL of the DI water and stirred for 15 min. 1000 mg of the oxalic acid powder was added to the solution and stirred for 10 min. Potassium carbonate was used for controlling the pH of the solution to 10.5. The prepared solution was rested at room temperature for 2 days, during which it became a violet color. IrO₂ was electrodeposited through a cyclic voltammetry (CV) measuring instrument using a three-electrode configuration. Only the counter electrode and working electrode were used. The reference electrode was not used. A platinum mesh electrode was used as a counter electrode and a neural interface was used as a working electrode. A voltage of 0 V to 0.76 V was applied at a scan rate of 50 mV/s, and was swept 50 times.