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: Capacitive coupling within high-density microelectrode arrays can degrade neural recording signal or disperse neural stimulation current. Material deterioration in a chronically implanted neural stimulation/recording system can cause such an undesired effect. We present a simple method with an iterative algorithm to quantify the cross-coupling capacitance, in-situ.Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 02/2006; 1:3365-8. DOI:10.1109/IEMBS.2006.259543
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ABSTRACT: Activated Iridium Oxide Film (AIROF) microelectrodes are thought to be well-suited for neural stimulation of the cortex because they can sustain high charge capacity (about ten times higher than Pt microelectrodes) when characterized in phosphate-buffered saline (PBS) or other high ionic strength electrolytes. However, it is known that their capacity diminishes after they are implanted in vivo. It has been suggested that tissue encapsulation is an underlying cause. In this paper, we report electrochemical measurements of AIROF microelectrodes that were performed acutely in the brain of the zebra finch. The experiment showed that the interstitial fluid environment in the bird's brain did not maintain the high charge delivery capacity of the AIROF microelectrodes. A simple compensation for access resistance may create hazards to sustained electrode integrity.Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 02/2006; 1:886-9. DOI:10.1109/IEMBS.2006.259869
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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