<s>
A	O
capacitive	B-Algorithm
micromachined	I-Algorithm
ultrasonic	I-Algorithm
transducer	I-Algorithm
(	O
CMUT	B-Algorithm
)	O
is	O
a	O
relatively	O
new	O
concept	O
in	O
the	O
field	O
of	O
ultrasonic	B-Algorithm
transducers	I-Algorithm
.	O
</s>
<s>
Most	O
of	O
the	O
commercial	O
ultrasonic	B-Algorithm
transducers	I-Algorithm
today	O
are	O
based	O
on	O
piezoelectricity	O
.	O
</s>
<s>
CMUTs	B-Algorithm
are	O
the	O
transducers	O
where	O
the	O
energy	O
transduction	O
is	O
due	O
to	O
change	O
in	O
capacitance	O
.	O
</s>
<s>
CMUTs	B-Algorithm
are	O
constructed	O
on	O
silicon	O
using	O
micromachining	O
techniques	O
.	O
</s>
<s>
On	O
the	O
other	O
hand	O
,	O
if	O
ultrasonic	O
waves	O
are	O
applied	O
on	O
the	O
membrane	O
of	O
a	O
biased	O
CMUT	B-Algorithm
,	O
it	O
will	O
generate	O
alternating	O
signal	O
as	O
the	O
capacitance	O
of	O
the	O
CMUT	B-Algorithm
is	O
varied	O
.	O
</s>
<s>
As	O
CMUTs	B-Algorithm
are	O
micromachined	O
devices	O
,	O
it	O
is	O
easier	O
to	O
construct	O
2D	O
arrays	O
of	O
transducers	O
using	O
this	O
technology	O
.	O
</s>
<s>
This	O
means	O
large	O
numbers	O
of	O
CMUTs	B-Algorithm
could	O
be	O
included	O
in	O
a	O
transducer	O
array	O
providing	O
larger	O
bandwidth	B-Algorithm
compared	O
to	O
other	O
transducer	O
technologies	O
.	O
</s>
<s>
To	O
achieve	O
a	O
high	O
frequency	O
operation	O
using	O
CMUTs	B-Algorithm
is	O
easier	O
due	O
to	O
its	O
smaller	O
dimensions	O
.	O
</s>
<s>
As	O
it	O
is	O
built	O
on	O
silicon	O
,	O
the	O
integration	O
of	O
electronics	O
would	O
be	O
easier	O
for	O
the	O
CMUTs	B-Algorithm
compared	O
to	O
other	O
transducer	O
technologies	O
.	O
</s>
<s>
The	O
properties	O
to	O
use	O
in	O
high	O
frequency	O
with	O
large	O
bandwidth	B-Algorithm
makes	O
it	O
a	O
good	O
choice	O
to	O
use	O
as	O
a	O
transducer	O
in	O
medical	B-Application
imaging	I-Application
,	O
especially	O
in	O
an	O
intravascular	O
ultrasound	O
(	O
IVUS	O
)	O
.	O
</s>
<s>
Because	O
of	O
its	O
broader	O
bandwidth	B-Algorithm
,	O
it	O
could	O
be	O
used	O
in	O
second-harmonic	O
imaging	O
.	O
</s>
<s>
Also	O
some	O
experiments	O
have	O
been	O
performed	O
to	O
use	O
CMUTs	B-Algorithm
as	O
hydrophones	O
.	O
</s>
<s>
Surface	O
micromachining	O
is	O
the	O
traditional	O
way	O
of	O
manufacturing	O
CMUTs	B-Algorithm
.	O
</s>
<s>
In	O
this	O
method	O
,	O
a	O
CMUT	B-Algorithm
is	O
built	O
from	O
two	O
separate	O
wafers	O
,	O
which	O
are	O
later	O
bonded	O
to	O
achieve	O
cells	O
with	O
cavities	O
.	O
</s>
<s>
CMUTs	B-Algorithm
manufactured	O
in	O
the	O
multi-user	O
MUMPS	O
were	O
reported	O
to	O
have	O
reduced	O
performance	O
,	O
such	O
as	O
relatively	O
low	O
resonating	O
frequency	O
.	O
</s>
<s>
In	O
anodic	B-Algorithm
bonding	I-Algorithm
,	O
wafers	O
are	O
sealed	O
at	O
high	O
temperature	O
and	O
in	O
the	O
presence	O
of	O
electric	O
field	O
.	O
</s>
<s>
As	O
mentioned	O
earlier	O
,	O
one	O
of	O
the	O
significant	O
advantages	O
of	O
CMUTs	B-Algorithm
over	O
piezoelectric	O
transducers	O
is	O
the	O
ability	O
to	O
integrate	O
CMUTs	B-Algorithm
with	O
electrical	O
circuits	O
,	O
using	O
existing	O
manufacturing	O
methods	O
.	O
</s>
<s>
CMUT	B-Algorithm
performance	O
is	O
benchmarked	O
using	O
pitch-catch	O
and	O
pulse-echo	O
experiments	O
,	O
and	O
operation	O
uniformity	O
is	O
tested	O
in	O
air	O
and	O
in	O
immersion	O
.	O
</s>
<s>
The	O
CMUT-on-CMOS	O
technology	O
and	O
the	O
flip-chip	O
process	O
allows	O
tight	O
integration	O
of	O
CMUTs	B-Algorithm
with	O
front-end	O
electronics	O
,	O
which	O
is	O
necessary	O
for	O
miniature	O
medical	B-Application
imaging	I-Application
devices	O
,	O
such	O
as	O
IVUS	O
.	O
</s>
