Mildred Dresselhaus: The Queen of Carbon
Electronics made from nanoscale tubes, wires, and sheets of carbon are coming, thanks to pioneering researcher Mildred Dresselhaus
Before silicon got its own valley, this mild-mannered element had to vanquish many other contenders to prove itself the premier semiconductor technology. It did so in the 1950s and 1960s. Today, carbon is poised at a similar crossroads, with carbon-based technologies on the verge of transforming computing and boosting battery-storage capacities. Already, researchers have used these technologies to demonstrate paper-thin batteries, unbreakable touch screens, and terabit-speed wireless communications. And on the farther horizon they envision such carbon-enabled wonders as space elevators, filters that can make seawater drinkable, bionic organs, and transplantable neurons.
Whatever miracles emerge from Carbon Valley, its carbon-tech titans will surely think fondly upon their field's founding mother, Mildred Dresselhaus. This MIT professor of physics and engineering has, since the early 1960s, been laying the groundwork for networks of nanometer-scale carbon sheets, lattices, wires, and switches. Future engineers will turn these things, fabricated from carbon-based materials such as graphene, into the systems that will carry computing into its next era.
Now, after a half century of quiet work, she is accumulating accolades. This past November, in a ceremony at the White House, President Obama awarded her the Presidential Medal of Freedom, the U.S. government's highest civilian honor. “Her influence is all around us, in the cars we drive, the energy we generate, the electronic devices that power our lives," Obama said.
And this June, the IEEE will confer upon Dresselhaus its highest accolade, the IEEE Medal of Honor, for her “leadership and contributions across many fields of science and engineering." She is the first female Medal of Honor recipient in the award's nearly century-long history. (Before the IEEE's formation, the Medal of Honor was presented by the Institute of Radio Engineers, which merged with the American Institute of Electrical Engineers in 1963 to form the IEEE.)
While Dresselhaus has blazed a path for researchers eager to exploit the magic of carbon computing, for most of her 84 years her own pathway has been anything but obvious. It was muddled by a world that had trouble accommodating a visionary engineering researcher who was also a caring and thoughtful mentor—as well as a mother of four (and today a grandmother of five).
The daughter of destitute Eastern European émigrés, a product of Great Depression and World War II–era New York City schools and their melting-pot culture, Dresselhaus (née Spiewak) as a child imagined that the only career open to her was that of schoolteacher. Even that was a bit of a stretch, given the time and place: The kids in her neighborhood and in her struggling primary school in the Bronx were mostly uninterested in their studies. But a mysterious force soon intervened. It was music.
Both her grandfather and great-grandfather served as town cantors in her father's ancestral village of Dzialoszyce, Poland. So when her older brother, Irving, began playing the violin with uncommon grace at age 4, his gift wasn't a complete surprise. Their parents secured a scholarship for him at New York City's prestigious Greenwich House music school. And when Mildred was herself 4 or 5, she began studying music there, too. Although she stopped taking lessons at Greenwich House at 13, she has never abandoned her beloved violin. Dresselhaus still plays every day. “I had his hand-me-down violin," she says. “I inherited all the things he left behind."
And it was music that brought her into contact with more ambitious peers at the Greenwich House school. “It was obvious—education was important," she says she realized not long after arriving at the school, in 1934 or '35. “That was the most important lifelong thing I learned at the music school."
She would probably have again followed her brother's footsteps several years later, into the legendary Bronx High School of Science, but in those days Bronx Science was for boys only. So she set her sights on Hunter College High School, a New York City preparatory school for girls. While studying for her entrance exam, she discovered to her delight how easily math came to her. “My interest was inspired by studying—by myself and motivated by myself—math for the entrance exam to Hunter High," she says.
At Hunter, she did so well in math and science that a poem in Dresselhaus's senior yearbook pays tribute to her abilities: “Any equation she can solve / Every problem she can resolve / Mildred equals brains plus fun / In math and science, she's second to none." She went on to study at Hunter College, where, during her second year, another important force entered into her life.
“Rosalyn Yalow's [physics] course got me more into focusing on the science profession," Dresselhaus says of the course she loved most at Hunter, which was taught by a medical physicist who would soon herself decamp for a research career and ultimately share the 1977 Nobel Prize in Physiology or Medicine. “That's where I really got started. And Rosalyn insisted that I go to graduate school. She was a person who used to tell you what you were doing."
Bolstered by Yalow's effusive letters of recommendation, Dresselhaus was admitted to Radcliffe College in 1951 for graduate studies, an admission deferred so that she could attend the University of Cambridge on a Fulbright fellowship.
“Radcliffe had no [science] classes," Dresselhaus explains. “The classes were at Harvard. But the exams were at Radcliffe. Women didn't take their exams with the men. I had to take my exams by myself in a different room. It was a very complex situation and not a very comfortable one."
During her first year at Harvard, Dresselhaus realized she was growing weary of the university and a bit restless. She'd discovered that the best place in the country to study physics was at the University of Chicago, home to Manhattan Project veteran and Nobel laureate Enrico Fermi. So in 1953, after finishing her master's degree at Radcliffe, she was off to Illinois.
At Chicago, too, Dresselhaus was often the only woman in her classes. But the learning environment wasn't as stifling. And it was at Chicago, she says, where she first really began to learn to think like a physicist, thanks to Fermi himself. Although by then famous for his role in the Manhattan Project, Fermi headed up a small and intimate physics department. In Dresselhaus's incoming class in 1953, for instance, there were just 11 physics students.
Fermi was an early riser, as was Dresselhaus, and they lived along the same walking route to campus. So she, along with other students, faculty, and acolytes, timed their morning commute so they could stroll along with the legendary physicist.
“He was a methodical guy; he always did the same thing every day," Dresselhaus says. On the morning walks, for example, Fermi would talk about the issues on his mind—sometimes related to the day's lecture, sometimes not. And when Fermi gave his talks, he'd first hand the class copies of his notes. “He didn't want people taking notes while he [lectured]. He wanted people to listen. He'd give you the notes. The lecture [notes] didn't have many pages. Very concise."
Fermi, who died in November 1954, during Dresselhaus's second year at Chicago, still had an outsized influence on the young woman during her brief time in his orbit. “He developed in me the mind-set that we should be interested in everything," she says, “because we never know where the next big breakthrough in science will occur."
Selected Papers from Dresselhaus for IEEE Xplore
In the fall of 1955, Dresselhaus began her Ph.D. project, investigating the microwave properties of a superconductor in a magnetic field. The novel and hybrid nature of her investigation—involving low-temperature and solid-state physics, electrical engineering, and materials science—meant she couldn't just order the parts for her research out of a catalog.
She found much of what she needed, though, under the university's football stands, where more than a dozen years before, Fermi had led a group that had created the world's first man-made nuclear-fission chain reaction. There, a mountain of surplus equipment was free for the taking. Repurposing a warehouse worth of materials, she grew superconducting wire for her experiments, built microwave equipment, and even produced liquid helium.
Dresselhaus says she'd developed that kind of gumption because her primary school teachers were terrible. “They were sufficiently bad that if you wanted to learn something, you taught yourself," she says. “That was terrific training."
While at Chicago, she met her future husband, fellow graduate student Gene Dresselhaus. They married in May 1958 and moved to Ithaca, N.Y., where she was a National Science Foundation postdoctoral fellow and Gene had an entry-level faculty position in the physics department at Cornell University. There Dresselhaus also met another celebrity scientist, albeit one whose great fame would come years later—Richard Feynman. At the time, Feynman was developing the equations that would become the quantum theory of electrodynamics.
“He gave a lecture now and then," she says. “And if there's a Feynman lecture, you go to it. It's always interesting, looking at things you've heard about before but from a totally different perspective."
Also in 1959, the Dresselhauses welcomed their first child, Marianne. And despite the stimulating Feynman lectures Dresselhaus occasionally attended, Cornell wasn't exactly a female academic's dream in those days. Early on, a faculty member told her point blank that no woman would ever be permitted to lecture to his engineering students.
Photo: Mike McGregor
So in 1960 the two Dresselhauses went to MIT's Lincoln Laboratory. There she moved out of superconductors, her thesis topic, and began looking instead at magnetic and optical properties of graphite, bismuth, and other so-called semimetals. This field, she says, wasn't popular or very competitive at the time, which gave her the latitude she needed to have four children (one daughter and three sons) through 1964. As a working mother, however, she encountered some bumps in her career progress.
One Lincoln Lab colleague, H. Eugene Stanley (now a professor of physics, chemistry, biomedical engineering, and physiology at Boston University) recalls the day after Dresselhaus delivered her youngest child, Eliot, in 1964.
“When she had her fourth kid," recalls Stanley, “she brought him to work the day after he was born. She was there around noon or 1 o'clock with the baby in tow. But because Lincoln Lab was a government lab, you either had to have clearance or have a badge. They wouldn't let the kid in. She was furious! I didn't see her angry that often, but I saw her angry that day."
Dresselhaus crossed from Lincoln Lab to parent institution MIT in 1967, accepting a visiting professorship in electrical engineering, a position that became permanent the following year. She added a joint appointment in physics in 1983.
“When I first came to MIT, the [physics] department was only interested in high-energy physics," she says of a field that was then consumed with colliding subatomic particles at ever-higher energies. She adds that more quotidian fields of physics, from materials science to engineering physics, were on the back burner at the time. “It's all totally different now.… There's a big shortage of people [who] have a physics background and engineering also."
On a snowy day in the middle of one of Cambridge's harshest winters ever, Dresselhaus holds forth in her MIT office on her favorite topic. “Consider a simple sheet of carbon atoms, also known as graphite," she begins.
She pulls down a well-worn ball-and-stick-model from atop one of her cabinets. “Carbon's crystal structure is such that the in-plane force is the strongest in nature," she says. “But across the plane it's very weak. So it allows separation of layers very easily."
A pencil's graphite flakes off easily without disintegrating, and yet it can still cling to rough, fibrous surfaces like paper. Individual sheets of graphite, in other words, are as tough as diamond. But as a group they're as flaky as phyllo dough.
Date of birth: 11 November 1930
Birthplace: Brooklyn, N.Y.
First job: Teaching a learning-disabled 6-year-old to read when she herself was just 8
First job in science or technology: Staff member, Solid State Division, MIT Lincoln Laboratory, June 1960
Hero: Enrico Fermi
Most recent book read: “One that I reviewed. Nowadays, working time is more precious than ever, and I do not have much time for recreational reading."
Favorite music: “What I am playing on my violin. I enjoy chamber music, like string trios, quartets, and quintets."
Computer most frequently used: Apple iPad
Favorite restaurant: “Eating at home."
Biggest worry: “I don't spend time in worrying. I plan for things and handle the unexpected as best I can."
Honors (partial list): National Medal of Science; Vannevar Bush Award; Enrico Fermi Award; Kavli Prize in Nanoscience; Foreign Associate, Engineering Academy of Japan; Foreign Fellow, National Academy of Sciences of India; Einstein Professorship, Chinese Academy of Sciences; Presidential Medal of Freedom; IEEE Fellow, IEEE Founders Medal, and 2015 IEEE Medal of Honor
Throughout the 1960s, 1970s, and 1980s, Dresselhaus and her graduate students investigated the properties of both graphite and carbon intercalation compounds—that is, sheets of graphite sandwiching individual bromine or potassium atoms, which were captured like olives between slices of bread. Her group also laid the foundation for the discovery and exploitation of nanotechnological wonder materials, such as the tiny carbon spheres known as buckminsterfullerenes, the cylindrical carbon pipes called nanotubes, and the single-atom-thick sheets of carbon called graphene.
Variations or combinations of these carbon structures could yield body armor stronger than Kevlar, ultrathin membranes with pores small enough to filter the salt from seawater, and even bionic implants that can give new hope to those with serious spinal-cord or organ damage. Used as electrodes in batteries or capacitors, graphene and nanotubes offer promise as a kind of ultimate energy storage system. Their charge capacities would exceed those of traditional batteries, and their charge times (on, say, an electric-vehicle battery) would be shorter than the time it takes to pump a tankful of gasoline.
And as a possible substrate for next-generation electronics, graphene has few competitors today. Its high conductivity (better than silver's) and its single-atom thickness make robust, molecule-size graphene circuit components boasting terahertz computing speeds a tantalizing if far-future possibility. “Graphene is not going to replace silicon; it's going to do different things," Dresselhaus says.
Although well into her 80s, Dresselhaus is at her MIT office every day, including weekends and holidays, often as early as 6 a.m. Her enthusiasm for her work, which these days includes studying optical, electric, and vibrational properties of graphene, carbon nanotubes, and other nanomaterials seems undiminished. “I am excited by my present research and am not yet anxious to stop working," she says, simply.
As she has for much of her MIT career, Dresselhaus also mentors young people, especially women starting careers in STEM. She has supervised the theses of more than 60 doctoral students and shepherded many more colleagues and associates through career transitions and inflection points.
“One time at MIT, she told me she was working with this great [Ph.D.] student named Shirley Ann Jackson," says Laura Roth, Dresselhaus's former colleague at Harvard and Lincoln Lab. “And now she's president of Rensselaer Polytechnic Institute." (Jackson has herself earned 52 honorary degrees and been called by Time magazine “perhaps the ultimate role model for women in science.")
Says Gang Chen, head of the mechanical engineering department at MIT, “Four women from my own group…benefitted from Millie's support during their stay at MIT. On several occasions, Millie volunteered to talk to my female students, giving them individual career advice.
“On one hand, it seems to be quite late for the first woman to receive the IEEE Medal of Honor," Chen adds. “On the other hand, no one is more fitting than Millie, and she has set a truly high bar. I am sure Millie's receiving this honor will inspire more women in IEEE to strike high."
This article originally appeared in print as “The Queen of Carbon."