Biomedical Engineering Reference
In-Depth Information
FIGURE 4.102
A fabricated small-scale PAN system.
FIGURE 4.103
Initial length (left) and contracted length (right).
We also measured the length change between elongation state and contraction
state overall strain. Single-string (25-mm) fiber was taken and immersed in 1
M
HCl. The fiber contracted to 11 mm. We worked on measuring displacement at each
concentration change and generated force with varying pH levels.
Figure 4.103 depicts the change in length of the polyacrylonitrile fiber bundles
before and after contraction. Figure 4.101 depicts the conductive gold-plated helical
compression spring-loaded PAN fiber bundle synthetic muscles and electrode samples.
Three muscle samples were tested. Two of the samples had identical dimensions
and the third one had larger dimensions. Two samples (acid activated and E-activated2,
fig. 4.104) had 25 strands and 15.5-cm length; the other (red) had 30 strands (20%
increased) and 17.5-cm length (16% increased). Electrodes of 7.5 and 10.5 cm, respec-
tively, were used. One sample was soaked in 1
M
HCl to compare results with an
electric activation muscle system (the baseline). An input voltage of 5 V was used to
operate the system. In acid solution, most of the reaction was done in a very short
period of time when compared with the electrically activated fiber with the same
dimensions, and more force was achieved than for the electrical system.
When the reaction was complete, the force was converged to 150 gf. The
electrical system reached 40% of acid-activated force after 25 min of operation and
the force was still increasing.
The larger dimension sample (red) reached 180 gf and 0.06 N force per a single
string of PAN fiber and was achieved with a sharper gradient, which meant short
response time. It also converged after 25 min of operation. It should be noted that
the size of the electrodes affects the performance significantly. This finding was
investigated more carefully. As the previous observations indicated, H
+
ions are
created at the anode side, so a larger surface area of anode increased the possibility
to generate more H
+
to contact fiber with H
+
ion, which basically was to reduce the
