Biomedical Engineering Reference
In-Depth Information
d
n
3
r
4
n
g
|
2
Figure 8.4
SEM image of
surface morphology of PEDOT/pTS
at
2500
magnification.
8.2.3 Characterisation
There are several key design criteria of conducting polymers for biomedical
applications. These include surface morphology, electrochemical and
mechanical stability, charge transfer characteristics, and biocompatibility.
A summary of common analytical techniques used to characterise these and
other properties is presented below.
.
8.2.3.1 Surface Properties
The critical surface properties typically evaluated include surface chemistry
and topography. There is a range of techniques used to measure these
properties and these are outlined briefly in this section. It is particularly
important to understand how these properties may change as a result of
incorporation of biological molecules and different dopants since they all
directly impact on the cellular and tissue responses.
A critical component of the characterisation of conducting polymer elec-
trodes is its chemical composition. This is of particular importance when
working with novel dopants (such as bioactive dopants) or when incorpor-
ating non-conventional components into conducting polymer films. X-ray
photoelectron spectroscopy (XPS) is the most valuable methodology for
probing the elemental composition, as well as the chemical and electrical
state of conducting polymers. In XPS the sample is irradiated with X-rays
causing electrons to be ejected from the top 10 nm of the material. Meas-
urement of the number and kinetic energy (binding energy) of ejected
electrons provides a characteristic elemental spectrum. By analysing the
relevant elemental spectra it is possible to determine the doping ratio (how
many dopant molecules per monomer unit) as well as the redox state (the
Search WWH ::
Custom Search