Biomedical Engineering Reference
In-Depth Information
8. lonic polymer-metal composites (IPMCs) . Ionic
polymer-metal composite (IPMC) is an
EAP that bends in response to a small
electrical field (5-10 V/mm) as a result of
mobility of cations in the polymer
network. Reference is made to Shahinpoor
et al. for the introductory paper on IPMCs
in 1998 [19] . Oguro et al. [20] and
Shahinpoor [21 , 22] should be consulted
for some earlier similar development of
electroactive inonic membrane gels.
9. Conductive polymers (CP) or synthetic metals .
Conductive polymers operate under an
electric field by the reversible counter-ion
insertion and expulsion that occurs during
redox cycling [23] . Oxidation and reduc-
tion occur at the electrodes, inducing a
considerable volume change due mainly
to the exchange of ions with an electrolyte.
When a voltage is applied between the
electrodes, oxidation occurs at the anode
and reduction at the cathode. The pres-
ence of either a liquid eletrolyte contain-
ing conjugated ions or a solid
polyelectrolyte medium in close proximity
to conductive polymers, such as polypyr-
role (pPy), is often necessary to cause
charge migration into and out of the
conductive polymer.
10. Shape-memory polymers . Shape-memory
polymers (SMPs) are similar to shape-
memory alloys (SMAs) in the sense that
they remember their shape at a certain
specific temperature and can recover their
shape if they are heated to that tempera-
ture. For a very good coverage of this
topic, see Behl et al. [24] .
Briefly, IPMCs are cationic capacitive actua-
tors and sensors that operate dynamically due
to ionic redistribution due to either an imposed
electric field or an imposed deformation field.
When we apply a voltage across their thickness
in a membrane or strip form, they bend quickly
(millisecond response) toward the anode
because cations move away from the anode
toward the cathode side and cause the cathode
side to expand and the anode side to contract;
thus, bending occurs on the anode side. If the
signal is oscillatory, then the strip oscillates
accordingly as the cations move back and forth
across the membrane.
On the other hand, if they are mechanically
bent by outside forces (mechanical deformation
due to applied loads), they generate electric-
ity across the two electrodes attached to them
because ionic redistribution causes an electric
field due to Poisson's effect. Thus they are actua-
tors, sensors, and energy harvesters.
In Ref. 25 , methods of fabrication of several
electrically and chemically active ionic poly-
meric gel muscles, such as polyacrylonitrile
(PAN), poly(2-acrylamido-2-methyl-1-propane
sulfonic) acid (PAMPS), and polyacrylic-acid-
bis-acrylamide (PAAMs) as well as a new class
of electrically active composite muscle such as
ionic polymeric conductor composites (IPCCs)
or ionic polymer-metal composites (IPMCs)
made with perfluorinated sulfonic or carboxylic
ionic membranes, are introduced.
Mathematical theories and numerical simula-
tions associated with ionic polymer nanocom-
posite electrodynamics and chemodynamics are
also formulated for the manufactured materials.
In this chapter we concentrate on ionic
biopolymers such as chitosan for biomimetic
distributed nanoactuation, nanosensing, and
energy harvesting as well as artificial muscle
applications for medical and industrial needs.
Shahinpoor's group has been involved in
performing research on combining the
biopolymer chitosan with organic polymer
electrolytes such as perfluorinated sulfonic or
6.1.5 Ionic Polymer-Metal Composites
Ionic polymer-metal composites (IPMCs) are
in fact nanocomposites and are biomimetic
distributed nanosensors, nanoactuators, energy
harvesters, and artificial muscles. For a good
review of these materials, see Refs. 25-29 .
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