Biomedical Engineering Reference
In-Depth Information
FIGURE 4.3
Single 100-fiber bundle encapsulated PAN muscle with three-way fittings
designed especially for transport of pH solution and water within the fiber bundle (relaxed
length is 6 in.).
4.3
PAN CHARACTERIZATION
A number of test fixtures and structures were designed to evaluate the PAN muscles
for loading and displacement characteristics such as the isotonic and the isoionic
test apparatus shown in figures 4.4 and 4.5.
The isotonic apparatus consisted of a container made of acrylic polymer where
the PAN muscle was fastened on its bottom to a center eyebolt. This container was
such that it could be removed and detached from PAN muscle to empty out the pH
solutions after completion of the test. The other end of the PAN fiber was connected
to a balancing counterweight to neutralize the weight of the metal container and
transducer attachments on the other side of the apparatus. The counterweight was
then attached to a nylon string, which was routed around two pulleys (to minimize
the effect of friction) and then attached to a metal container on the other side of the
apparatus. This container was secured from the bottom to a linear variable differential
transducer with 0.001-mm accuracy. The transducer was directly connected to a
digital indicator that converted the analog signal from transducer (resulting from
displacement of the weight container) and at the same time conditioned the signal
to correct for any temperature or pressure variation in the environment.
4.3.1
I
C
SOTONIC
HARACTERIZATION
Consider figure 4.4. To operate in isotonic mode, a known weight was added to the
left (metal) container to put a tension force across the PAN muscle in the right
(acrylic) container. The muscle was then sprayed with 1-
solution of HCl to initiate
contraction. This caused the known weight on the other side to be lifted (pulled),
therefore indicating a positive reading on the digital displacement indicator. When
full contraction of muscles was reached, the final readout was recorded for the known
weight in gram force (gf) units. This can be repeated for any number of weights to
M
