Up and Coming Researcher Touts Interdisciplinary Approach

What does a researcher with a Ph.D. in electrical engineering do when confronted with one of the biggest challenges facing carbon nanotube technology? Mark Hersam's experience at the Beckman Institute told him to look outside the materials science box and try something from the biochemistry labs.

Carbon nanotubes have been touted for years as one of the next great technological breakthroughs for everything from electronics to sensors, but their properties make them difficult to control and, therefore, produce on a large scale.

“Carbon nanotubes, due to a lack of uniformity in their physical and electronic structures, are not suitable for large-scale production in most technologies,” said Hersam, a professor of Materials Science and Engineering at Northwestern University. “So we've recently developed a strategy for sorting carbon nanotubes by their diameter and electronic properties.”

Hersam used a technique in biochemistry called density gradient ultracentrifugation, calling upon a centrifuge to sort the nanotubes by their diameter and electronic properties.

“What we recognized is that carbon nanotubes, as a function of their diameter, will have subtle differences in their buoyant densities, that is their mass per volume,” Hersam said. “As a result, if you can come up with a way of sorting nanotubes by their density, then you should be able to sort them by their structure and properties. As it turns out, there was already a strategy in biochemistry that allows separation by density.

“This work is an excellent example of how my interdisciplinary training at Beckman taught me to look outside of my discipline when faced with a challenging problem. In this case, when faced with a problem in electronics and materials science, we went to biochemistry to find a solution.”

Hersam is just six years removed from a Ph.D. in electrical engineering from the University of Illinois at Urbana-Champaign, but he already has his own research group at Northwestern, a solid line of papers in peer-reviewed journals, and two of the most coveted awards any young researcher can win. Last year, Hersam was given a Sloan Fellowship and in July of 2006 he was honored at the White House with the 2005 Presidential Early Career Award for Scientists and Engineers.

A native of Downers Grove, Hersam earned a B.S. in electrical engineering from the U. of I. and a Master's in physics from Cambridge in England. As an undergraduate and as a graduate student, Hersam did research at Beckman, working with Joe Lyding in the Molecular and Electronic Nanostructures research initiative. Lyding, who built the first scanning tunneling microscope (STM) at Illinois, was a mentor for Hersam, and they collaborated on research projects and papers involving subjects such as atomic level manipulation and silicon-based molecular nanotechnology.

Hersam took his STM expertise and research interests to Northwestern in 2000 when he joined the faculty there. He also brought along an approach to research that was ingrained during his time at Beckman.

“The number one thing that I learned at Beckman is how to interact in an interdisciplinary environment,” Hersam said. “The idea of Beckman really works, all the way down to the student level. At a lot of places faculty may interact with each other but students keep to their own research group.

“But at Beckman the students really interacted. That allowed me to understand how interdisciplinary research works and also learn many of the skills and techniques not only in my field, but also in other fields. Since becoming a faculty member at Northwestern, I've been successful in establishing interdisciplinary research programs as a direct result of my time at Beckman.”

At Northwestern, STM technology has remained an important part of Hersam's work. He currently is using scanning tunneling microscopy to probe the electrical properties of organic molecules on silicon surfaces. Improving the performance of electronics at the level of individual molecules is the long-range goal. Hersam said that Intel Corporation is currently working on transistors at the scale of about 100 nanometers, but the ultimate goal is to get down to the molecular scale, or about one nanometer.

“We are exploring what could happen in future electronic technologies,” Hersam said. “If you look at the trends in microelectronics you're looking at 20 or maybe even 30 years in the future where, if things continue at the same rate as today, you would have devices made at the molecular length scale in industry.

“That's a long way off; this is very long-term research. But with the scanning tunneling microscope we can begin to probe how such devices work and if it is worth continuing electronic miniaturization all the way down to the single molecule level. We may find that electronics cannot be pursued as we know it at this length scale or that there are some fatal flaws to molecular electronic technology. However, at this point, it looks promising enough to continue our research.”

The work with carbon nanotubes is another current focus for Hersam. In the October issue of Nature Nanotechnology, Hersam and his collaborators reported original research using density gradient ultracentrifugation for sorting nanotubes by their density.

“One advantage of this technique is that it is fully scalable,” Hersam said. “If you look at industry today, for example the pharmaceutical industry, you can find large-scale centrifuges that continuously handle hundreds of liters of solution at a time. With this technology, we anticipate that our process can be scaled up to provide large quantities of purified carbon nanotubes.”

Hersam's research has already made an impact, as evidenced by the papers and awards. The Sloan Research Fellowship from the Alfred P. Sloan Foundation is the oldest and one of the most prestigious fellows program in the country. He said the Presidential Early Career Achievement Award was special because researchers from all the sciences are eligible for it. Hersam was also impressed that President Bush took time out of his busy schedule to attend the event.

“President Bush made the time, which was surprising because on that day he had to meet with the Iraqi Prime Minister,” Hersam said. “I think it would have been easy and understandable for him not to attend. His attendance showed his support of scientific research and education.”

Hersam appreciates his Teacher of the Year Award from Northwestern's Department of Materials Science and Engineering as much as any of his honors.

“The teaching award is very meaningful to me. I became a professor first and foremost to educate and the teaching award was granted by the students,” Hersam said.

For anyone thinking about pursuing a career in academia, Hersam has a couple of pieces of advice. He said keeping an open mind is crucial for any person interested in an academic career of teaching and research — and the Beckman Institute is an excellent place to develop that mindset.

“Being in an environment like Beckman is perfect because you can be exposed to a wide range of topics, not just what is going on in your particular research group,” he said.

“I think that's critical for many reasons, one being that most of the interesting problems in research today are at the boundaries between disciplines.”

Hersam added that having a wider range of interests also helps when it comes to securing funding for research proposals.

“If you have a broad training, then you can diversify your research program and be less sensitive to the winds of change in Washington,” Hersam said. “The second piece of advice, which is true not only in academia, but true for any career in science, is to become as efficient as possible in your work.

“Everyone at this level is putting in the maximum number of hours, so there's no way that you can outwork anyone. The only way you can be more productive is to be more efficient and make good decisions regarding how to spend your time.”