Biomedical Engineering Reference
In-Depth Information
The first attempts to create artificial muscles date back to the pioneering work
of Kuhn and his students (1950) and Katchalsky and his students (1949) in connec-
tion with pH-activated muscles (or simply pH muscles) (Steinberg et al., 1966;
Shahinpoor, 1992, 1993; Otero et al., 1995). Note also the other means of activating
artificial muscles, such as thermal (Kishi et al., 1993; Tobushi et al., 1992; Li et al.,
1999), pneumatic (Shahinpoor et al., 2001), optical (van der Veen and Prins, 1971),
and magnetic (Zrinyi et al., 1997). Chemically stimulated polymers were discovered
more than half a century ago when it was shown that collagen filaments could
reversibly contract or expand when dipped in acidic or alkaline solutions, respectively
(Katchalsky, 1949). This early work pioneered the development of synthetic poly-
mers that mimic biological muscles (Steinberg et al., 1966; Shahinpoor, Bar-Cohen
et al., 1998).
However, electrical stimulation has remained the best means of artificial muscle
material actuation and sensing. Shahinpoor and Mojarrad (1994, 1996, 1997a,
1997b, 1997c, 1997d, 2000) were among the pioneers of making electrically
active—in sensing and actuation—IPCNCs and IPMNCs electrically active in sens-
ing and actuation. (See also Mehran Mojarrad's Ph.D. dissertation, 2001.) Zhang
and colleagues (1998) were able to observe a substantial piezoelectric activity in
PVF2-TrFE as early as 1998. The most progress in artificial muscle materials'
development has occurred in the last 10 years, where effective materials that can
induce strains exceeding 100% have emerged (Perline et al., 1998). All the preced-
ing categories of electroactive polymers also fall under the category of artificial
and or synthetic muscles.
Next we will describe some more specific artificial muscle materials.
1.2.11
S
M
A
(SMA
)
S
M
HAPE
EMORY
LLOYS
S
AND
MALL
EMORY
P
(SMP
)
OLYMERS
S
The history of SMA and SMP artificial muscles is extensive and will not be reported
here. However, the pioneering works of Liang and Rogers (1990, 1992) and Liang
et al. (1997) in developing SMA and SMP actuators are noteworthy. In their work,
a load of a spring-biased SMA actuator was modeled as a dead weight. However,
many practical applications involve varying loads, such as the cases of SMA rotatory
joint actuators (Shahinpoor, 1995d; Wang and Shahinpoor, 1997a, 1997b, 1997c).
A general design methodology of various types of bias-force SMA actuators has
been investigated by Shahinpoor and Wang (1995) (see also Guoping Wang's Ph.D.
dissertation, 1998).
1.2.12
M
H
A
M
S
ETAL
YDRIDE
RTIFICIAL
USCLE
YSTEMS
The binary combination of hydrogen and a metal or metal alloy can absorb large
amounts of hydrogen via surface chemisorption and subsequent hydriding reactions.
This phenomenon can be used to fabricate artificial muscle systems as described in
Shahinpoor and Kim (2001d), U.S. Patent 6,405,532 (Shahinpoor and Kim, 2002f),
Lloyd et al. (2002), Kim et al. (2002), and Shahinpoor (2002c).
Useful characteristics
of metal hydrides as artificial muscles are their large uptake/discharge capacity of
