RESUMO
Miniaturized electrodes, structures and devices are necessary to achieve high target selectivity during stimulation in single neuron networks, while significant charge transfer is still demanded. A reliable test method is required to evaluate charge injection capability for high resolution neural stimulation applications that demand both a large amount of charge injection and a small electrode size. A circuit designed for the pulse-clamp technique was employed to characterize the electrode charge-storage capability of microelectrodes of sizes smaller than 300 microm in diameter. The circuit allows different electrodes and surface modifications to be quickly and accurately compared. Pulse-clamp measurements are performed on planar microelectrodes in 154 mM phosphate buffered saline (PBS) solution with 400 micros long pulses at charges up to 40 nC. The pulse-clamp and cyclic voltammetry results of sputtered iridium oxide film (SIROF) electrodes of different sizes show charge losses of less than 3% and a superior reversible charge injection capability compared to platinum microelectrodes of the same size, even at higher charge density levels.
