Biomedical Engineering Reference
In-Depth Information
3.
The ion-exchange polymer is first surface treated with sandpaper. The
standard size of the polymer sample is about 5
×
5 cm.
4.
The ion-exchange polymer is placed between the backing materials facing
the powder-coated side.
5.
Pressing is carried out at 2 tons using a temperature-controlled hot-press
(RAMCO, 50-ton capacity) at 120-130
°
C for a duration of 15 min.
6.
Steps 1-4 are repeated, three times. Usually, low electric surface sheet
resistance is obtained (
R
< 1
Ω
/square by the four-probe method).
7.
The preferred process is to impregnate small noble metal particles (i.e.,
platinum or palladium,
D
p
~ 50 nm) between the primary particles so as
to further fixate them within the ion-exchange polymer. This process is
to introduce metallic ions [Pd(NH
3
)
2+
] or [Pt(NH
3
)
2+
] into the ion-
exchange polymer initially and, later, reduce them to a metallic state.
8.
As a final step, a conductive metallic layer (i.e., gold or palladium) is
further electroplated on the top of the interlocked electrode layer.
Figure 3.54 includes a SEM photograph (cross-section) of a sample IPMNC, its
close-up, and associated x-ray line scan. The penetration of Ag particles is approx-
imately 7-8
µ
m, as can be measured by the x-ray line scan.
Ag (via physical loading)
Dp~1-3
µ
m
Pt (via chemical process)
Dp~50 nm
5
µ
m
FIGURE 3.53
A schematic process illustration of the PLI-IPMNCs (left) and silver particle
used (right). (Shahinpoor, M. and K. J. Kim. 2002. In
Proceedings of SPIE 9th annual
international symposium on smart structures and materials
. SPIE publication no. 4695, paper
no. 36.)
