Biomedical Engineering Reference
In-Depth Information
4
Sample #1
Sample #2
Sample #3
3
2
1
0
0
5000
10000
15000
20000
25000
E (V/m)
FIGURE 6.31
Experimental determination of Onsager coefficient
L
using three different
samples.
Figure 6.35 depicts a typical spectacular steady-state deformation mode of a
strip of such ionic polymers under a step voltage.
When we study the
inverse effect
(transduction mode, fig. 6.28), we apply a
bending moment
M
to the cantilever membrane, and we impose two conditions:
No current is produced (
J
= 0).
The strip stays bent with a curvature
κ
E
.
Then, as fully derived and described in de Gennes et al. (2000), the water pressure
gradient turns out to be proportional to
M
.
The condition
J
= 0 gives, from equation (6.131),
∇
pxyzt
(,,,)
L
Exyzt
(,,,)
=∇
σ
p xyzt
(,,,)
(6.137)
Since
∇
pxyzt
(,,,) (
=
M I
/ )
(6.138)
the electric field
E
(
x
,
y
,
z
,
t
) generated is thus proportional to
M
according to
L
I
LY
(,,,)
=
(
)
=
κ
(
)
(6.139)
E xyzt
M
E
σ
σ
