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An Integrated-Circuit Approach to Extracellular Microelectrodes


This paper describes a new multielectrode microprobe which utilizes integrated-circuit fabrication techniques to overcome many of the problems associated with conventional microelectrodes. The probe structure consists of an array of gold electrodes which are supported on a silicon carrier and which project beyond the carrier for a distance of about 50 μ to allow a close approach to active neurons. These electrodes are covered with a thin (0.4-μ) layer of silicon dioxide which is selectively removed at the electrode tips using high-resolution photoengraving techniques to define the recording areas precisely. The processing sequence described permits any two-dimensional electrode array to be realized. Interelectrode spacings can be accurately controlled in the range from 10 to 20 μ or larger, and electrode-tip diameters can be as small as 2 μ. An equivalent-circuit model is developed for the probe structure which allows its performance to be predicted. The stray capacitance from electrode to ground (and corresponding signal attenuation) is very low for the present structure, and interelectrode coupling is virtually negligible. Preliminary tests using these probes in the brain have shown them to be well suited for recording from small populations of neurons, and they have successfully recorded spike discharges from isolated neurons in cat cortex. Copyright © 1970 by The Institute of Electrical and Electronics Engineers, Inc.

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