By Marlene Cimons, National Science Foundation
Mildred Dresselhaus started studying carbon nearly 50 years ago, early in her research career, when few scientists had any interest in this important element, the strongest material known and the sixth most abundant in nature.
Often dubbed the “Queen of Carbon Science,” Dresselhaus, 81, a longtime Massachusetts Institute of Technology professor, is regarded as a leader in the field of condensed matter and materials physics, and an expert on all the multi-faceted forms of carbon from its largest sizes to its tiniest.
“Carbon is a very important material in our planet,’’ she says. “The world has a huge amount of carbon in it. Lots of things have to do with carbon. Carbon atoms, all by themselves, make interesting material in nature. If you go walking in the woods, you can find flakes of carbon in the soil. My first ten years were spent studying the electronic structure of carbon, and getting to understand how it works.’’
Her research into superconductivity, the electronic properties of carbon, thermoelectricity and the new physics at the nanometer scale have led to numerous scientific discoveries, with the potential for more.
Dresselhaus, MIT’s institute professor emerita of electrical engineering and physics, recently won the prestigious Kavli Prize for nanoscience, “for her pioneering contributions to the study of phonons, electron-phonon interactions, and thermal transport in nanostructures,” an honor that also brings $1 million award. She also is a longtime grantee of the National Science Foundation (NSF), dating back to the 1960s, when NSF first began supporting her materials research.
The Kavli committee lauded her multiple advances explaining how the nanoscale properties of materials can vary from those of the same materials at larger dimensions, as well as her early work on carbon fibers and on intercalation compounds for laying the groundwork for later discoveries concerning carbon nanotubes, graphene and buckeyballs. (The latter are large molecules of carbon, each one composed of 60 or 70 carbon atoms linked together in a structure that resembles a soccer ball. Buckeyballs can trap other atoms, appear capable of withstanding great pressures and have magnetic and superconductive properties.)
“Nowadays, circuits are based on nanotubes and graphene combinations,’’ she says. “I’m not going to tell you that they will replace silicon, but carbon electronics will have a role in electronics in the future, particularly in high frequency communications. There is a big limit to what silicon can go up to, and in that regime, carbon will take over.’’
The first concept she worked on involved creating atomic sized “intercalation’’ compounds made up of “super lattices,’’ layers of different chemical species sandwiched between layers of graphite, the foundation of lithium-ion batteries, such as those used in automobiles and cell phones.
Later, she sought to learn more about carbon at the nanoscale, a size so incredibly small it must be magnified ten million times to be seen by the naked eye. In 1992, she was among the first to propose that carbon nanotubes--tubes with the thickness of a single atom--could be metallic or semi-conducting, depending on their structure. Later, she made them.
“Nowadays, we’ve gone beyond the nanotubes and we’re back to graphene, which is where we started in 1960,’’ she says. “You take a single nanotube, split it open and you get a little ribbon of graphene. You flatten it out and make a sheet out of it. A nanotube is a rolled up graphene sheet.’’
Graphene is a single atomic layer of carbon molecules, and currently the focus of considerable research. It shows great promise for use in electronics and other fields as a fast, efficient substance from which to make computer chips, sensors, and ultracapacitors, devices that supply energy but differ from batteries in that they can be charged and discharged quickly, although, unlike batteries, cannot store energy very well.
“Heat is among carbon’s many properties, it is the very best thermal conductor,’’ she says. “Nanotubes and graphene transport heat very well. Their electronic properties are so much better when you make them in nanoform than when you make them in bulk form.’’
Dresselhaus receives credit for being among those scientists who prompted renewed interest in the thermoelectrics research field by moving it in the direction of nanostructures. In 1992, the U.S. and French navies both sought her help in designing a new power system for submarines that would make them less detectable to the Russians. She suggested they develop a thermal nanosystem that would generate power from the temperature difference between the system, which was hot, and the ocean, which was cold, instead of with traditional fuel.
“If you could run these submarines with power that is not from an engine making a lot of noise, but run by the temperature difference between something heating very quietly and the ocean, which is cold, and use that voltage difference, they could run the submarines quietly and nobody would know they were there,’’ she recalls. “The power would come from the thermal electric effects, and you wouldn’t have to use your engine. Imagine a ship running without noise; it would make the submarine much less obvious. They could go through the water stealth-like.
“Now they are looking for the next generation, new processes that will improve thermoelectric performance,’’ she adds.
Since 1973, she has held an institute-wide chair at MIT that allows her to conduct research in any area she chooses, without restriction. She works seven days a week, although only half-day days on the weekends so she can spend time with her family, and arrives to work long before anyone else, sometimes as early as 5 or 6 a.m.
Born and raised in New York City, Dresselhaus, as an undergraduate at Hunter College, met future Nobel Laureate Rosalyn Yalow, who recognized her talent and encouraged her to pursue science. “She was a teacher of mine at Hunter when I started doing science,’’ Dresselhaus says.
“Hunter was the kind of college you attended to become a schoolteacher, there wasn’t much opportunity to study science,’’ she adds. “ She was teaching because she couldn’t get another job. She taught only for one semester, and I was in the class. So I benefited from having a research-oriented teacher.’’
That exposure likely was among the factors leading to her passionate commitment to mentoring students, particularly women in science. “Mentors are important, and I try to be a mentor,’’ she says. “I believe that people always should pay back.’’
Queen of Carbon Science
Kavli prize winner is a nanoscience pioneerJuly 27, 2012 RSS Feed Print
By Marlene Cimons, National Science Foundation