Biomedical Engineering Reference
In-Depth Information
2.0
Nafion
TM
-117 IPMC
1.5
1.0
0.5
0.0
Na
+
Li
+
K
+
H
+
Ca
++
Mg
++
Ba
++
TBA TMA
Counter ion
FIGURE 3.22
Effects of various cations on the actuation of the IPMNC muscle. Comparisons
were made against Na
+
in terms of maximum force generated at zero displacement. A
sinusoidal input voltage of 1.2 V
rms
and a frequency of 0.5 Hz were set for all experiments.
The samples were cut in a standard size of 0.675
×
2.54 cm. Na
+
was chosen as a reference
since it is coordinated with four water molecules.
Another issue is water uptake, depending upon the type of cation (Komoroski
and Mauritz, 1982). The type of ion-exchange materials used in this study, perfluo-
riated sulfonates, is presumably not cross-linked (Eisenberg and Yeager, 1982) (or
partially cross-linked). Therefore, water uptake (swelling) is expected to be con-
trolled by mobile cations and pretreatment. Also, the ion-cluster phenomenon that
relates exchange sites, counter-ions, and solvent phase as an independent phase (note
that cross-linked polymers cannot form such a phase) could be another important
factor to determine water uptake (Gierke and Hsu, 1982).
In order to clarify the importance of hydration processes, the input power con-
sumption of the sample containing different types of cations was measured. The test
results are presented in figure 3.23. It has the form of
F
P
F
P
+
max(
Na
)
max
(3.3)
in
+
in Na
(
)
This dimensionless form can be interpreted as the specific force generated per a
given applied input power.
