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Abstract

For over 30 years, techniques have been developed that allow for the microscale (10-30 /mum) measurement of chemical signals with high temporal resolution (1-200 Hz). Such measurements, called in vivo electrochemical recordings, allow for the direct determination of neurotransmitter molecules and related compounds in biological systems. Multiple recordings, simultaneously performed at different, closely spaced, well defined locations throughout a three-dimensional tissue volume in the brain, are of interest in neuroscience. Developments in microelectronic techniques enable the fabrication of multi-electrode microprobes for recording extracellular action potentials generated by individual neurons simultaneously. A high-yield microfabrication process has been successfully developed for the fabrication of a novel semiconductor based, four-site silicon microprobe that involves a three-mask process and standard UV photolithography. A plasma process has been developed for dry etching of the gold electrodes and conducting lines. The electrochemical behavior of the microprobe is investigated by a high-speed computer-based in vitro electrochemical recording system. The electrochemical signals are measured at 5 Hz and varying gain. It is found that a selectivity of over 500:1 is achieved, and the signal to noise ratio of the recorded signal is particularly suitable for in vivo recordings.

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