Cytoarchitecturally conformal multielectrode arrays for neuroscience and neural prosthetic applications

The research described in this dissertation focuses on the development of multiple configurations of planar, conformally-mapped multielectrode arrays (cMEAs) that have enabled stimulation and recording of acute hippocampal slice activity. The configurations of the five cMEAs fabricated to date are conformal in that the arrays are designed to match specific geometrical features of various subfields of the rat hippocampus (e.g., CA1, CA3, dentate gyrus, and perforant pathways). The high-density characteristic of the arrays has also provided a high spatial resolution for current-source density analysis, with 50 mum or 60 mum center-to-center distances. The combination of geometrical mapping of the arrays and their high-density placement in two dimensions has been attempted for the first time. A primary long-term goal of the research is to address issues related to interfacing biomimetic cortical prosthetic devices to damaged hippocampal regions.;Fabrication of gold- and indium-tin-oxide-based cMEAs with up to sixty-four recording/stimulating elements has been achieved. The crosstalk between adjacent electrodes was measured to be negligible, and the electrode impedances were approximately 180 kO at 1 kHz for 28 mum-diameter gold electrodes. The impedance values of cMEAs with gold and indium-tin-oxide electrodes were well below the means of their respective electrode types as compiled from the literature. Additionally, preliminary data on the impedance of novel indium bump electrodes suggested that their rough surface morphology yields lower impedance values than those of flat gold electrodes. A Randles equivalent circuit model closely followed the actual behavior of the gold electrode-electrolyte interface for a wide range of frequencies. The safe potential range has been identified as between -1.1 V and 1.2 V (vs. Ag/AgCl), and the charge transfer capacity was calculated to be 11.2 mC/cm2 between -0.8 V and 0.8 V. A charge injection capacity of 1.22 mC/cm2 was extracted from potential monitoring experiments in which varying intensities of current pulses were injected into the stimulating electrodes. Various evoked in-vitro electrophysiological experiments with acute hippocampal slices have successfully been performed using the cMEAs. Finally, a summary of the progress achieved and suggestions for future research are provided.