Biomedical Engineering Reference
In-Depth Information
d
n
4
t
3
n
g
|
7
Figure 3.7
Micrograph of 2D wire electrode array with 120 mm spacind.
42
(Reprinted by kind permission of the IEEE.)
n
3
.
Figure 3.8
3D conductive doped silicon electrode array. Each electrode is insulated
with silicon nitride and the exposed tip is platinum plated with a
0.005mm
2
area. Electrode lengths range from 0.5 to 1.5mm with 400 mm
spacing.
43
(Reprinted by kind permission of the American Physiological Society.)
Spontaneous activity and induced action potentials can be detected with
MEAs using the ion flux associated with channel receptors in the neural
membrane. The principle measurement is based on detecting the electrical
capacity measured between a chemically modified microelectrode and the
neuron axon using ac-coupled amplifiers with high input impedance. Figure 3.9
shows a commercially available microelectrode array with planar 50 mm
2
elec-
trodes.
41
The whole configuration is immersed in a special measurement
chamber, which may contain reference electrodes, counter electrodes and/or
ion-selective electrodes (for pH or oxygen, etc.) which are connected to multiple
