Charge Injection Capacity Measurement

Fig. 16 Current and voltage waveforms of a PEDOT-coated Pt electrode under pulse stimulation (a). The electrode was stimulated in PBS under a charge-balanced, cathodic-first, biphasic pulse current at 1 mC/cm at 50 Hz (b). Voltage excursion was measured under pulse stimulation currents to evaluate the PEDOT electrode charge injection capacity...

Before activation the charge injection capacity of the disc electrodes was measured by the method explained in Sect. 5.3. Outliers were neglected. The measurement error was estimated to be under 6 %. Table 6.2 shows the average results. For MEA 1 two distinct groups were observed, witli a third of the electrodes having the higher charge injection capacity. 

In this study, beside using standard measurement devices like potentiostat, new hardware was designed and implemented in order to investigate microelectrodes. The electrode materials under investigation were iridium, iridium oxide and titanium nitride. It was shown that these can provide more charge injection capacity compared to the traditionally used platinum. Other alternatives like conducting polymers are also studied worldwide and may come to practical applications soon. 

The enclosed area of the curve is a measure of the reversible charge delivery capacity of the electrode. For fast current pulses, a different measurement method is used to determine the charge injection limits without gassing. Current pulses are applied and the voltage over two electrodes is monitored just below the gassing limits (Fig. 24). Once having passed the extensive in vitro testing, the electrodes were tested in chronic animal experiments. 

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