<s>
The	O
exceptional	O
electrical	O
and	O
mechanical	O
properties	O
of	O
carbon	O
nanotubes	O
have	O
made	O
them	O
alternatives	O
to	O
the	O
traditional	O
electrical	O
actuators	B-Algorithm
for	O
both	O
microscopic	O
and	O
macroscopic	O
applications	O
.	O
</s>
<s>
These	O
properties	O
are	O
difficult	O
to	O
find	O
in	O
the	O
same	O
material	O
and	O
very	O
needed	O
for	O
high	O
performance	O
actuators	B-Algorithm
.	O
</s>
<s>
For	O
current	O
carbon	B-Algorithm
nanotube	I-Algorithm
actuators	I-Algorithm
,	O
multi-walled	O
carbon	O
nanotubes	O
(	O
MWNTs	O
)	O
and	O
bundles	O
of	O
MWNTs	O
have	O
been	O
widely	O
used	O
mostly	O
due	O
to	O
the	O
easiness	O
of	O
handling	O
and	O
robustness	O
.	O
</s>
<s>
Carbon	O
nanotube	O
tweezers	O
have	O
been	O
fabricated	B-Architecture
by	O
deposition	O
of	O
MWNT	O
bundles	O
on	O
isolated	O
electrodes	O
deposited	O
on	O
tempered	O
glass	O
micropipettes	O
.	O
</s>
<s>
Researchers	O
of	O
AlliedSignal	O
initially	O
demonstrated	O
the	O
possibility	O
of	O
electrically	O
powered	O
actuators	B-Algorithm
fabricated	B-Architecture
by	O
carbon	O
nanotube	O
sheets	O
.	O
</s>
<s>
They	O
taped	O
carbon	O
nanotube	O
sheets	O
on	O
two	O
sides	O
of	O
a	O
double	O
sided	O
scotch	O
tape	O
and	O
applied	O
potential	O
on	O
the	O
nanotube	O
sheets	O
in	O
a	O
NaCl	B-Application
electrolyte	O
solution	O
.	O
</s>
<s>
Therefore	O
,	O
electrically	O
driven	O
actuators	B-Algorithm
of	O
nanotube	O
sheets	O
are	O
superior	O
to	O
the	O
conjugated	O
polymer	O
actuators	B-Algorithm
which	O
involve	O
solid-state	O
dopant	O
diffusion	O
and	O
structural	O
changes	O
limiting	O
rate	O
,	O
cycle	O
life	O
,	O
and	O
energy	O
conversion	O
efficiencies	O
.	O
</s>
<s>
Nanotube	O
sheet	O
actuators	B-Algorithm
were	O
shown	O
to	O
operate	O
at	O
low	O
voltages	O
( ≈1	O
volts	O
or	O
less	O
)	O
and	O
provide	O
higher	O
work	O
densities	O
per	O
cycle	O
than	O
other	O
alternative	O
technologies	O
.	O
</s>
<s>
showed	O
that	O
actuator	B-Algorithm
response	O
can	O
be	O
observed	O
up	O
to	O
switching	O
rates	O
of	O
1kHz	O
and	O
cycling	O
the	O
nanotube	O
actuator	B-Algorithm
at	O
constant	O
rate	O
of	O
1Hz	O
for	O
140,000	O
cycles	O
decreases	O
the	O
stroke	O
by	O
≈33%	O
.	O
</s>
<s>
0.75	O
MPa	O
of	O
stress	O
were	O
measured	O
on	O
the	O
nanotube	O
sheet	O
actuators	B-Algorithm
,	O
which	O
is	O
greater	O
than	O
the	O
maximum	O
stress	O
(	O
0.3	O
MPa	O
)	O
that	O
can	O
be	O
loaded	O
on	O
a	O
human	O
muscle	O
.	O
</s>
<s>
The	O
maximum	O
actuator	B-Algorithm
strain	O
for	O
electrically	O
driven	O
actuators	B-Algorithm
of	O
carbon	O
nanotube	O
sheets	O
can	O
be	O
improved	O
up	O
to	O
0.7	O
%	O
in	O
a	O
1	O
M	O
electrolyte	O
once	O
the	O
sheets	O
are	O
annealed	O
in	O
an	O
inert	O
atmosphere	O
at	O
very	O
high	O
temperatures	O
(	O
)	O
in	O
contrast	O
to	O
once-reported	O
0.1	O
%	O
or	O
less	O
for	O
low	O
electrochemical	O
potentials	O
( ≈1	O
V	O
or	O
less	O
)	O
.	O
</s>
<s>
The	O
maximum	O
strain	O
for	O
the	O
carbon	O
nanotube	O
sheet	O
actuators	B-Algorithm
at	O
low	O
voltages	O
is	O
greater	O
than	O
that	O
of	O
the	O
high-modulus	O
ferroelectric	O
ceramic	O
actuators	B-Algorithm
( ≈	O
0.1	O
%	O
)	O
,	O
but	O
it	O
is	O
lower	O
than	O
that	O
of	O
the	O
low-voltage	O
( ≈	O
0.4	O
V	O
)	O
conducting	O
polymer	O
actuators	B-Algorithm
( ≈3%	O
film	O
direction	O
,	O
20%	O
thickness	O
direction	O
)	O
.	O
</s>
<s>
The	O
released	O
gas	O
dramatically	O
increases	O
the	O
actuator	B-Algorithm
stroke	O
from	O
the	O
carbon	O
nanotube	O
sheet	O
.	O
</s>
<s>
Having	O
aerogel	O
sheets	O
of	O
MWNTs	O
,	O
UT	O
researchers	O
fabricated	B-Architecture
actuators	B-Algorithm
with	O
giant	O
strokes	O
( ≈180%	O
actuation	O
along	O
the	O
width	O
)	O
with	O
5	O
ms	O
delay	O
time	O
between	O
applying	O
the	O
potential	O
and	O
observing	O
the	O
maximum	O
stroke	O
.	O
</s>
<s>
The	O
subfield	O
of	O
carbon	B-Algorithm
nanotube	I-Algorithm
actuators	I-Algorithm
have	O
been	O
quite	O
successful	O
and	O
ready	O
for	O
scalable	O
applications	O
,	O
considering	O
there	O
are	O
quite	O
a	O
few	O
conventional	O
and	O
scalable	O
methods	O
for	O
the	O
synthesis	O
of	O
large-scale	O
carbon	O
nanotubes	O
.	O
</s>
<s>
Carbon	O
nanotube	O
sheets	O
used	O
as	O
electrodes	O
in	O
electrolyte	O
solutions	O
enable	O
low	O
voltage	O
operations	O
at	O
room-temperature	O
with	O
actuation	O
strokes	O
and	O
rates	O
comparable	O
to	O
the	O
conducting	O
polymer	O
actuators	B-Algorithm
,	O
but	O
with	O
higher	O
work	O
densities	O
per	O
cycle	O
and	O
lifetimes	O
.	O
</s>
