Biomedical Engineering Reference
In-Depth Information
Figure. 8 Calculated current-distance curves toward conducting (solid line) and
insulating (broken line) substrates. Plots represent an approach curve obtained for a
DNA-grafted, redox-polymer coated electrode (for the detailed description, refer to
Section III.3). Equations (4) and (5) that fit into a finite reaction, which follows
primary kinetics, yield the theoretical curves shown in dotted line, which can ex-
plain, in part, the experimental curve.
a disk-shaped tip in a thin insulating planar sheath, either at an
ideally insulating substrate or at a conducting substrate. These
curves are presented in the dimensionless form of
i
T
/
i
T,
҄
vs.
d
/
a
.
Later
i
T
(
L
) denotes
i
T
/
i
T,
҄
with
L
=
d
/
a
. Furthermore, these curves
are independent of disk diameter, diffusion coefficient and solute
concentration. Here,
RG
value given by the ratio between the radi-
us of the insulating sheath and the radius
r
of the tip electrode can
be used for the definition of the geometry of UMEs. When we take
examples of UMEs with
RG
= 10.2, numerical results
33
have pro-
posed the following approximate forms for an insulating substrate:
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