Biomedical Engineering Reference
In-Depth Information
FIGURE 6.10
Cantilever and load-cell configuration for measuring the tip-blocking force of IBMC samples.
Porfiri
[53]
also discussed and modeled
sensing and actuation of IPMCs based on
charge dynamics. Wallmersperger
et al
.
[54]
discussed the thermodynamical modeling of the
electromechanical behavior of ionic polymer-
metal composites. It is beyond the scope of this
chapter to elaborate on these models, but a brief
discussion follows.
Once an electric field is imposed on such a net-
work, the conjugated and hydrated cations rear-
range to accommodate the local electric field
and thus the network deforms, which in the sim-
plest of cases, such as in thin membrane sheets,
spectacular bending is observed (
Figure 6.6
)
under small electric fields such as tens of volts
per millimeter.
Let us now summarize the underlying
principle of the IBMC's actuation and sensing
capabilities, which can be described by the
standard Onsager formulation using linear
irreversible thermodynamics. When
static
conditions
are imposed, a simple description of
mechanoelectric effect
is possible based upon two
forms of transport:
ion transport
(with a current
density
J
, normal to the material) and
solvent
transport
(with a flux
Q
, which we can assume is
6.4.1 Linear Irreversible Thermodynamic
Modeling of Forces and Fluxes
As recently as 2000, Gennes
et al.
[46]
presented
the first phenomenological theory for sensing
and actuation in ionic polymer-metal compos-
ites. Note from
Figure 6.11
that there are ionic
fluxes and forces at work within the IBMCs.
