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Multichannel Microelectrode for Recording Neural Activity

IP.com Disclosure Number: IPCOM000045566D
Original Publication Date: 1983-Apr-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 5 page(s) / 47K

Publishing Venue

IBM

Related People

Cuomo, JJ: AUTHOR [+3]

Abstract

This article relates generally to apparatus for recording electrophysiological data and more particularly to a multichannel microelectrode for recording neural activity.

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Multichannel Microelectrode for Recording Neural Activity

This article relates generally to apparatus for recording electrophysiological data and more particularly to a multichannel microelectrode for recording neural activity.

This article describes, in two different embodiments, the fabrication of a multichannel microelectrode using methods found in the microelectronic industry.

A schematic of the first version of a microelectrode 1 is shown in Fig. 1. An enlargement of the tip area 2 is shown in Fig. 2.

Microelectrode 1 consists of an array of forty-one recording sites 3 fabricated on a thin, narrow substrate 4, as shown in Fig. 2, connected via transmission lines 5 to output pads 6, as shown in Fig. 1. The recording site - transmission line - output pad circuits are made of gold sandwiched between two layers of silicon dioxide. Recording sites 3 and output pads 6 are exposed through the top layer of insulation, allowing electrical contact.

A number of factors influenced the design of microelectrode 1. The overall length of 3.75 cm was selected for ease of manipulation. The regions of the brain which are of interest are well within the reach of an electrode of this length. The number of recording sites was limited to forty-one. This number is far more than that on any previously reported electrode. In order to accurately investigate neural interactions, it is imperative that the electrode not destroy what is meant to be observed. To accomplish this, the electrode must be kept as slender as possible. With forty-one sites, the overall width of microelectrode 1 is 220 Mum.

Since the dendritic and local axonal branching of neurons in different brain areas ranges approximately from 20 to 500 Mum, the spacing of recordng sites 3 should be in that range to monitor neurons that are likely to be functionally connected. A spacing of 100 mm was selected for microelectrode 1.

Silicon was chosen as the substrate material since its technology is well developed and has good mechanical strength. Gold was selected as the recording circuit because of its corrosion resistance to biological fluids and compatibility with the selected fabrication techniques. Silicon dioxide was chosen since it meets both physiological and processing requirements and has been used extensively in the past as electrode material. It is inert to the body electrolyte and is also one of the few insulating materials which can be deposited in thin uniform films and controllably etched using microelectronic fabrication techniques.

The starting point for the fabrication of microelectrode 1 is the device substrate. This is 5.7 cm diameter, 375 Mum thick, single crystal silicon wafer. For compatibility with the final etching step, the wafer has been prepared such that the (100) crystallographic direction is perpendicular to the surface of the wafer. The wafer is cleaned using reagent grade solvents and is then thermally oxidized on both surfaces by heating the wafers to 1100 deg...