NASA
Tech Briefs: How long has the NASA Ames Center for Nanotechnology
been operating and what are your principal duties as Director?
Dr.
Meyyappan: We started as a small group in 1996, and since
then, the center has grown to have 50 full-time scientists. In addition
to these scientists, we also have visiting faculty, graduate and
undergraduate students, and high school students working with us
on various projects. Our nano center is the largest in-house nanotechnology
effort within the government, and it is also one of the largest
in the world.
As
the director, I am basically in charge of all the technical aspects;
I provide vision and what kind of projects we will work on. I am
also the senior scientist, which means that I also do technical
work.
NTB:
What nanotechnology projects are you currently working on?
Dr.
Meyyappan: We have a few areas as our primary focus. First,
we are using nanotechnology in the area of electronics and computing,
or nanoelectronics and computing. We are also developing nanotechnology-based
sensors and detectors, and we are utilizing nanotechnology in gene
sequencing. Our project focus is primarily material-driven and we
are looking at a variety of nanoscale materials. The first and the
major focus is on carbon nanotubes.
The
next class of materials that we are working with is inorganic nanowires,
like zinc oxide and gallium nitride, for the manufacture of sensors
and detectors. The third class of materials is protein-based nanotubes,
which are biological. We synthesize them in large quantities and
purify them. We are using them for applications like templates for
lithography.
We
are using the fourth class of materials, organic molecules, as a
conducting channel to make electronic devices. We synthesize these
organic molecules and we try to make a logic chip or a memory chip.
In
nanotechnology research, it is not just enough to do experimental
work. In order to make sense of the results and to understand the
work that we are doing, it is very important to have complimentary
supporting modeling work. We therefore have a group of people who
do modeling and simulation.
NTB:
What are carbon nanotubes?
Dr.
Meyyappan: Carbon nanotubes look like nanoscale cylinders,
about 1 nm or so in diameter and a few microns long. Imagine rolling
up a sheet of graphite into a tube; that is what we are talking
about. There are a few procedures in the lab we are using to grow
these structures. One method is called Chemical Vapor Deposition
(CVD), which uses some hydrocarbon gases such as methane with a
catalyst material like iron. In the second method, called plasma
enhanced CVD, we use low temperature plasmas to grow nanotubes.
NTB:
What is it about the structure of nanotubes that makes them so versatile
and functional to all of these diverse industries?
Dr.
Meyyappan: Carbon nanotubes are very unique in the sense
that they have extraordinary mechanical properties. For example,
compared to steel, nanotubes have a strength-to-weight ratio of
500. At the same time, nanotubes can be used to make a computer
chip, because in addition to these wonderful mechanical properties
they also have very exciting electrical properties. A nanotube,
depending on its growth conditions and its diameter, can be a metal
or a semiconductor, allowing us to create semiconductor-metal and
semiconductor-semiconductor junctions.
What
is unique about this material is that historically, all the materials
we used for computer chip applications were impractical for construction
of an aircraft. The same with aluminum or stainless steel; these
metals could be used to manufacture an automobile, but they could
never be used to make a computer chip. This unique material, which
is still emerging, can be used for both fine applications like computer
chips and sensors, and for massive applications in the aerospace
and automotive industries. The reason why people are so excited
about this technology is that it is versatile and covers a whole
range of applications.
NTB:
Has NASA used carbon nanotubes recently?
Dr.
Meyyappan: We are pretty much in the research stage. NASA has a
measuring system called the “Technology-Readiness Level”
that measures how close a technology is to deployment. The scale
goes from 1 to 9. The technology at the level 1 or 2 is at basic
research. At level 4 or 5, the gap between research and final deployment
is bridged. Our technology readiness level with nanotubes is primarily
level 1 or 2, but I believe that in a few years’ time we will
slowly start migrating up the ladder towards deploying the actual
application.
NTB:
Do you have a specific time frame in mind?
Dr.
Meyyappan: There are actually some applications that are
already beginning to emerge. First, we have used carbon nanotubes
as a tip in an atomic force microscope, a technology that allows
you to look at things at the atomic level. It provides the so-called
“eye” to see something at atomic scale. Carbon nanotubes
provide the resolution to look at something on that level, and are
also able to survive for a long time -- even week after week.
Not
only does it have tremendous applications for NASA, but it also
has immediate applications in the semiconductor industry. In silicon
manufacturing today, we have to profile trenches, which are very
narrow holes, probably about a few microns deep. People want to
know what the profile looks like, which means that we have to use
something sharp in there to trace the profile. This is called a
profilometer, and we were able to demonstrate that carbon nanotube
tips could be used as a profilometer. That technology is actually
being very warmly embraced by the semiconductor industry. NASA Ames
spun off a company about six months ago that is attempting to mass
produce and market these carbon nanotube tips for the semiconductor
industry.
We
are also trying to create biosensors using carbon nanotubes because
biosensors are important to NASA in terms of astrobiology applications.
Currently, we are also involved in a big program with the National
Cancer Institute to develop carbon nanotube-based biosensors for
cancer diagnostics. I believe broader applications will occur in
about two to five years, but the majority of them will have applications
only after a decade.
Resources:
Recent
interviews:
Amy
Keith
Remedial Project Manager for CERCLA
Marshall Space Flight Center
Dr.
Edward Snell
Senior Scientist
Marshall Space Flight Center
Brian
F. Beaton
Technology Commercialization Project Manager
Langley Research Center
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