Biomedical Engineering Reference
In-Depth Information
goal is to produce electrode arrays that have high neuronal yield, are highly customizable in terms
of geometry/layout, minimize tissue damage, and are easy to mass fabricate.
7.1.1 Microelectrode design Specifications
An optimal electrode design for BMI chronic in vivo recording requires
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small profile probes that exert the least amount of tissue damage during insertion and chronic
recording;
structurally robust probes that do not buckle during insertion into tissue;
low probe impedance that is stable during chronic recording;
recording sites selective to single neuron action potentials;
adaptability to on-chip processing circuitry.
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Using conventional micromachining techniques, one can design small-profile metal traces
enclosed between flexible polyimide insulation, making a cable, as shown in Figure
7.3
. The actual
probes extend from the cable 2 mm and include 20 × 50 µm electrode sites on the tips. The electrode
area is chosen for sufficient compromise between signal selectivity and noise performance. The cor-
responding probe dimensions assure adequate structural integrity according to calculation using the
Euler-Bernoulli beam theory. The metal traces and corresponding bond sites can be made to any
size specification and spacing distance via photolithography. Therefore, custom application specific
FIgURE 7.3:
(a) Flexible substrate microelectrode array with Omnetics connector. (b) Microelectrode
array. (c) Probe tip showing insulation along shank and gold plating on tip.
