A laboratory testing and driving system for AIROF microelectrodes.

ABSTRACT The charge-injection currents of AIROF (activated iridium oxide film) microelectrodes, which are subjected to charge-balanced biphasic pulsing or monophasic current pulsing, have to be limited such that the anodic and cathodic voltage excursions are kept within safe limits of operation. In earlier studies it has been shown that when using anodic bias asymmetry in the magnitude of the balanced biphasic waveform can be used to increase the charge injection capacity of AIROF electrodes. We present the design of a single-channel testing and driving system for laboratory testing and driving of AIROF microelectrodes within safe charge-injection limits.

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    ABSTRACT: Microelectrodes with an upper functional layer of dc sputtered iridium oxide film (SIROF) are intended to be applied in biohybrid circuits for single insect neuron stimulation. In this paper, we report on electrochemical evaluation and of planar disc microelectrodes of varying size (diameter of 10 to 300 mum) and their charge injection properties of SIROF at microelectrode level during fast current pulses. The pulse injection charge (Q<sub>inj</sub>) limits represent only a fraction of the charge storage capacity (Q<sub>csc</sub>) measured by cyclic voltammetry. Electrodes with diameter down to 100 mum and 80 -100 mC .cm<sup>-2</sup> oxide charge capacity sustain about 2<sup>-2</sup> in pulse mode, while the maximum charge injection per phase for d=10 mum electrodes the respective values were Qcsc = 892.6<sup>-2</sup> and Q<sub>inj</sub> = 9.1<sup>-2</sup> .
    Solid-State Sensors, Actuators and Microsystems Conference, 2007. TRANSDUCERS 2007. International; 07/2007
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    ABSTRACT: The electrochemical activation process of the activated iridium oxide film (AIROF) has been investigated on a microelectrode (the geometric surface area is 7850 μm2) with sputtered iridium in physiological saline solution (0.9% NaCl). For one activation cycle, the potential is swept from −1.0 to 1.0 V at 0.05 Hz. The activation process could be controlled by the activation cycles which are characterized by the current–time data, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). After activation, the charge storage capacity of the AIROF microelectrode is 40.07 mC/cm2, which is nearly 24 times more than that of iridium microelectrode. The impedance at 1 kHz of the AIROF microelectrode is 4064 Ω, about one-tenth of that of iridium microelectrode. The double layer capacitance of the AIROF microelectrode is 1.519 μF, about 34.5 times more than that of iridium microelectrode. The relationship between the electrochemical performance of the AIROF microelectrodes and the applied activation cycles is also investigated. In the neutral electrolyte at pH 7, the Ir(IV)/Ir(III) surface redox couple exhibits increasing separation of the oxidation/reduction peaks due to the protons released/consumed during the Ir(IV)/Ir(III) redox activity. Finally, the relationship between the separation of the redox peaks and the applied activation cycles is also studied.
    Sensors and Actuators B Chemical 01/2014; 190. DOI:10.1016/j.snb.2013.08.085 · 3.84 Impact Factor