Biomedical Engineering Reference
In-Depth Information
0.008
0.006
0.004
0.002
0.000
-0.002
-0.004
-0.006
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
Time (sec)
FIGURE 6.29
Dynamic sensing of the ionic polymer due to imposed deformation.
of the imposed electric field
E
,
Y
is the Young's modulus (elastic stiffness) of the
strip, which is a function of the hydration H of the IPMNC, and I is the moment of
inertia of the strip. Note that, locally, M(
E
) is related to the pressure gradient such
that, in a simplified scalar format:
∇
pxyzt
(,,,)
= (2P/t*) = (
M
/I) = Y/
ρ
c
= Y
κ
(6.134)
κ
E
Now, from equation (6.134), it is clear that the vector form of curvature
is
related to the imposed electric field
E
by
κ
E
= (L/KY)
E
(6.135)
δ
max
of an IPMNC
strip of length
l
g
should be almost linearly related to the imposed electric field because
Based on this simplified model, the tip bending deflection
2
2
2
κ
≅
[
2
δ
/ (
l
+
δ
)]
≅
2
δ
/
l
≅
(L/KY)
E
(6.136)
E
max
g
max
max
g
The experimental deformation characteristics depicted in figure 6.30 are clearly
consistent with the preceding predictions obtained by the previous linear irreversible
thermodynamics formulation. This is also consistent with equations (6.133) and
(6.134) in the steady-state conditions and has been used to estimate the value of the
Onsager coefficient,
L
, to be of the order of 10
-8
m
2
/V-s. Here, we have used a low-
frequency electric field in order to minimize the effect of loose water back diffusion
under a step voltage or a DC electric field.
