Biomedical Engineering Reference
In-Depth Information
4.6.10.5
Further Modeling
Following the modeling presented in the second progress report (appendix B of this
topic), three working forces seem to drive the contraction and elongation of PAN
muscles. The osmotic pressure is a sum of rubber elasticity, proton pressure, and
polymer-polymer affinity. This can be expressed as
∏
t
=
∏
r
+
∏
e
+
∏
p
/
ρν
13
2
2
=−
(
RT
) /
M
+
(
ρ
RTf
/
M
)
ν
+
(
RT
/
V
)[
ν
+
ln(
1
−
ν
)
+
x
ν
]
(4.17)
2
c
c
2
2
2
In this equation, the volume fraction,
v
2
, is usually given by
V
0
/
V
. Notations
V
0
and
V
are the initial network volume and swollen volume, respectively. This volume-
fraction ratio is considered a main driving means of PAN artificial muscles. There-
fore, we attempted to measure the diameter change of the PAN muscle to estimate
the value associated with the term
V
0
/
V
.
Comparing figures 4.91, 4.92, and 4.93, one can clearly observe that “chemical
induction” is extremely effective in volume changes of the activated PAN fibers. This
means that “electric activation” of PAN fibers in an electrochemical cell produces
fewer dimensional changes at the present time compared with chemical activation.
Such findings enable one to further improve the performance of the PAN system. (Note
that the dimensional changes of the PAN fibers are 28.4
µ
m [electric activated] and
14.7
m [chemically activated], respectively.) We also obtained micrographs of PAN
fibers of “raw” and “Oxy-PAN,” for basic analysis (figs. 4.94 and 4.95).
The fiber diameter of the “raw” PAN is approximately 6
µ
µ
m. It expands to 7 ~
7.5
m after heat treatment (Oxy-PAN). An activated PAN (conditioned at 1
N
LiOH)
fiber expands to approximately 31
µ
µ
m in diameter and shrinks approximately 3
µ
m
in diameter upon electrical activation.
The diameter of a PAN fiber immersed in a 2-
N
HCl solution is approximately
15
m. We also observed that the vividness of the PAN fiber color increases as the
diameter decreases. The transport of water into and out of PAN dependent upon the
environmental conditions and resultant expanding and/or contracting volume of PAN
seemingly govern the overall properties of the PAN artificial muscle system.
Further electrical activation of the PAN linear contractile actuator system was
performed. In order to record the detailed dynamic behavior of the PAN linear
contractile actuator system, instrumentation was created with a load cell positioned
at the proximity of the PAN actuator to
µ
conduct analytical studies on PAN fibers (NMR and DMA, or DSC)
continue to improve the modeling and simulation of artificial muscle chemo-
electrodynamics
Three-strand braided configuration of a PAN muscle bundle was also fabricated,
as strong PAN synthetic muscles fiber bundles, for testing in a newly designed
electrochemical cell. The muscle fiber bundle was easy to handle but frictional
