Impedance characteristics of GSG electrodes for - Jong

Impedance characteristics of GSG electrodes for RLGC modeling of
cell-electrode interface
Jongmin Shin, and Jong-Ho Lee*
Department of ECE and ISRC, Seoul National University, Seoul 151-747, Korea
* E-mail : [email protected]
In the neural engineering, extracellular electrical stimulation and recording has been widely used
for decades with microelectrodes[1]. For RLGC modeling of cell-electrode interface, electrode that
is suitable for high frequency stimulating and recording neurons must be adopted. In this study, we
designed ground-signal-ground(GSG) electrodes for high frequency stimulation and recording of
neural network. GSG electrodes were made of platinium (geometric area: 140 ㎛  90 ㎛) and
passivated by 1 ㎛ SiO2-Si3N4-SiO2(ONO) stack layer. To investigate electrical properties of GSG
electrodes, we use elecetrochemical
impedance spectroscopy(EIS). The impedance of GSG
electrodes was measured in phosphate
buffered saline
(PBS) solution.
The GSG
electrodes-electrolyte interface are modeled by charge transfer resistance and constant phase
angle(CPA) element. In order to measure impedance, 10 mVrms AC signal is applied as a function
of frequency. GSG electrode impedances are ~ 100 kΩ at 1 kHz. As the frequency increases,
capacitance of the total impedance becomes dominant. Finally, since GSG electrode-electrolyte
interface act as a high pass filter.
<1 port GSG pattern>
0.8
signal line
ground line
10
VAC = 10 mVrms
5
(a)
Z ( )
10
4
10
3
(c)
10
100
1k
10k
100k
Frequency (Hz)
1M
signal line
ground line
0.6
-ZIm(M)
6

0.4
0.2
0.0
(d)
0.0
0.1
0.2
ZRe(M)
(b)
Fig 1. (a) GSG electrodes, (b) equivalent circuit model, (c) measured impedance, and (d) Nyquist
plot
[1] Yoonkey. Nam, Bruce C.Wheeler, Marc O. Heuschkel, Journal of Neuroscience Method,. 155,
296-299 (2006).

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