<s>
Comb-drives	O
are	O
microelectromechanical	O
actuators	B-Algorithm
,	O
often	O
used	O
as	O
linear	B-Algorithm
actuators	I-Algorithm
,	O
which	O
utilize	O
electrostatic	O
forces	O
that	O
act	O
between	O
two	O
electrically	O
conductive	O
combs	O
.	O
</s>
<s>
Comb	B-Algorithm
drive	I-Algorithm
actuators	B-Algorithm
typically	O
operate	O
at	O
the	O
micro	O
-	O
or	O
nanometer	O
scale	O
and	O
are	O
generally	O
manufactured	O
by	O
bulk	O
micromachining	O
or	O
surface	O
micromachining	O
a	O
silicon	B-Architecture
wafer	I-Architecture
substrate	B-Architecture
.	O
</s>
<s>
The	O
force	O
developed	O
by	O
the	O
actuator	B-Algorithm
is	O
proportional	O
to	O
the	O
change	O
in	O
capacitance	O
between	O
the	O
two	O
combs	O
,	O
increasing	O
with	O
driving	O
voltage	O
,	O
the	O
number	O
of	O
comb	O
teeth	O
,	O
and	O
the	O
gap	O
between	O
the	O
teeth	O
.	O
</s>
<s>
Restoring	O
springs	O
,	O
levers	O
,	O
and	O
crankshafts	B-Language
can	O
be	O
added	O
if	O
the	O
motor	O
's	O
linear	O
operation	O
is	O
to	O
be	O
converted	O
to	O
rotation	O
or	O
other	O
motions	O
.	O
</s>
<s>
Comb	B-Algorithm
drives	I-Algorithm
cannot	O
scale	O
to	O
large	O
gap	O
distances	O
(	O
equivalently	O
actuation	O
distance	O
)	O
,	O
since	O
development	O
of	O
effective	O
forces	O
at	O
large	O
gaps	O
distances	O
would	O
require	O
high	O
voltages	O
—	O
therefore	O
limited	O
by	O
electrical	O
breakdown	O
.	O
</s>
