October 2002

Dr. Meyya Meyyappan
Center for Nanotechnology, Ames Research Center

Dr. Meyya Meyyappan is the Director and Senior Scientist at Ames’ Center for Nanotechnology in Moffett Field, CA. His team is presently researching and developing carbon nanotubes.

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.


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