Biomedical Engineering Reference
In-Depth Information
In order to address these problems, we have changed the electric activation
scheme by using thin graphite fibers serving as an effective adjunct electrode circled
around and combined with PAN and gold as a counterelectrode.
4.6.4
G
RAPHITE
AND
G
OLD
F
IBER
E
LECTRODE
W
OVEN
INTO
PAN
M
USCLE
AS
AN
A
DJUNCT
E
LECTRODE
The idea of using a graphite or gold fiber electrode was motivated by the fact that
it could serve as an effective electrode producing necessary ions for contraction and
elongation, respectively. Another advantage is its chemical/mechanical endurance in
chemical environments during its activation process and contraction/elongation pro-
cesses. Also, the problems encountered in the direct metal deposition technique could
be adequately addressed. Figure 4.71 shows an SEM photograph of graphite fibers
employed and the configuration used in this study.
In figures 4.72 and 4.73, the electric activation of C-PAN fiber bundles with
graphite fiber electrodes is shown. Significantly improved response times relative
to the previously reported C-PAN platinum fibers can be observed. In fact, contrac-
tion and elongation as fast as
L
/
L
≈
10%/min and
L
/
L
≈
5%/min, respectively, can
be observed.
The efficient way of producing and diffusing the necessary ions (H
+
and OH
-
)
and their distribution over the C-PAN fibers is the key to producing fast-reacting C-
PAN fibers. Thus, single fiber response was also tested. For a single fiber comprising
2,000 strands of 10-
m diameter C-PAN-G fiber, the contraction time reduced by
about 60% compared to the fiber bundle of 50 fibers, as shown in figure 4.74.
The activation of a single strand of 10-
µ
µ
m fiber reduced the contraction time to
a few seconds, as shown in figure 4.75.
4.6.5
T
OWARD
N
ANOSCALED
A
RTIFICIAL
M
USCLES
AND
M
OTORS
Biological muscle is a magnificent nano- to micro- to macroscaled actuating system
with the capacity to perform diversified functions. According to Pollack (2001), the
PAN muscle
20
µ
m
Graphite fiber
FIGURE 4.71
SEM micrograph shows the graphite fibers used in this study (left). Each fiber
has a diameter of 6.4 µm and the configuration of the graphite electrode and PAN muscle (right).
