Photo by Bill Arsenault
Photo by Bill Arsenault
Image courtesy of Richard Van Duyne, Charles E. and Emma H. Morrison Professor of Chemistry.
In Paris the glowing reds and purples of Notre Dame cathedral’s famous stained glass windows owe their color to one precious metal: gold. The artisans of stained glass for medieval cathedrals across Europe had recipes for their glass, throwing soluble gold salts into the mix, knowing that only gold particles of certain very small sizes gave them their vibrant colors. They just didn’t know why.
Now, many centuries later, scientists and engineers around the world are beginning to fully comprehend the amazing properties of gold and other matter on the tiniest of scales, that of atoms and molecules.
In the future this growing knowledge could lead to fantastic new tools: gene chips as small as a needle tip, wallpaper that acts as a light source, devices that seek out and destroy plaque in arteries, powerful computers that run on molecules, windows that change color when anthrax spores are detected, lighter but stronger airplanes and automobiles, and solar cells that mimic photosynthesis.
Welcome to the wonders of nanotechnology, an industrial revolution in which Northwestern is leading the way.
Off to an Early Start
“It’s mind-boggling,” says Samuel Stupp (GMcC77), Board of Trustees Professor of Materials Science and Engineering and of Chemistry and a professor of medicine, “but such developments are possible only when you start to think about technology created on a much smaller scale. Nanotechnology is not a fad or a development in one discipline. It is a revolution across all science and technology.”
Nanotechnology — a broad term that refers to the design, fabrication and control of new materials and small structures on the nanometer-length scale — promises to affect virtually all future products. Human health, the environment, electronics, biological and chemical diagnostics, manufacturing and transportation all stand to benefit from nanotechnology and the power of the small.
Only in the last few years have countries around the world really started to pump government money into nanotechnology. According to Mihail C. Roco, who oversees the National Nanotechnology Initiative, launched in January 2000 by President Clinton, worldwide investment in nanotechnology research and development has increased fivefold since 1997. At least 30 countries have initiated national activities in the field, with the United States, Japan and Western Europe in the forefront. For the fiscal year 2003 budget, President George W. Bush requested $710 million for federal investment in nanoscale science, engineering and technology — 17 percent higher than the previous year’s figure.
The $34 million Center for Nanofabrication and Molecular Self-Assembly, one of the first federally funded nanotechnology facilities in the country, now sits on the Evanston campus. (The Institute for Nanotechnology, an umbrella organization for many of Northwestern’s nanotechnology research efforts, is housed here.) In 2001 the University landed one of only six National Science Foundation grants awarded to create a Nanoscale Science and Engineering Center. And Northwestern is playing a major role in two new NASA research institutes dedicated to nanotechnology.
“Northwestern University is one of the great nanotechnology success stories,” says Charles Martin, director of the Center for Research at the Bio/Nano Interface and a professor of chemistry at the University of Florida. “Scientists at Northwestern recognized the importance of this area over a decade ago and began at that time to develop and build a world-class nanotech research institute. That institute is now up and running, and as a result Northwestern is recognized as one of this country’s — and the world’s — leading centers for nanotechnology research. Other universities stand in envy of what Northwestern has accomplished. And other universities are desperately trying to play catch-up.”
Northwestern’s strongest competitors include Harvard, Cornell, Columbia and Rice Universities, MIT, Rensselaer Polytechnic Institute, and the Los Angeles and Santa Barbara campuses of the University of California.
In the early 1990s a critical mass of creative research dealing with miniaturization existed at Northwestern, particularly in chemistry and materials science, two areas where the University has historically been very strong. And the scale of miniaturization was pushing into new territory, from micro to nano, the ultimate in smallness.
“We realized we had something really special here,” says Chad Mirkin, George B. Rathmann Professor of Chemistry and director of the Institute for Nanotechnology, who, together with fellow chemistry professor Mark Ratner (G69), helped secure early funding that got the nanotechnology ball rolling and made a new building possible.
“Northwestern had great people who really liked to work together, to collaborate across boundaries,” Mirkin adds. “By bringing these pockets of excellence together, we created an institute and formed teams to go after early nanotechnology block grants.
“Very quickly we had one of the largest and most aggressive programs in the world,” he continues. “Other scientists frequently come up to me at conferences and say, ‘I wish my university were doing what Northwestern is doing.’”
The University’s interdisciplinary effort now taps faculty expertise in four schools (the Judd A. and Marjorie Weinberg College of Arts and Sciences, the Robert R. McCormick School of Engineering and Applied Science, The Feinberg School of Medicine and the Kellogg School of Management). It pulls together chemists; physicists; materials scientists; mechanical, chemical, biomedical and electrical engineers; physicians; and business experts. Hundreds of postdoctoral researchers and graduate students also are involved.
What’s Down There?
“Nano” comes from the Greek word for dwarf. Just how small is nano? A nanometer is one billionth of a meter or roughly the length of three atoms side by side. A DNA molecule is 2.5 nanometers wide, a protein approximately 50 nanometers and a flu virus about 100 nanometers. A human hair is approximately 10,000 nanometers thick.
Legendary physicist and Nobel laureate Richard Feynman was well ahead of his time when in late 1959 he delivered a now-famous speech, “There’s Plenty of Room at the Bottom,” suggesting the need to work at the most miniaturized level to meet society’s needs.
“What I want to talk about is the problem of manipulating and controlling things on a small scale,” said Feynman in his remarks. “As soon as I mention this, people tell me about miniaturization, and how far it has progressed today. They tell me about electric motors that are the size of the nail on your small finger. And there is a device on the market, they tell me, by which you can write the Lord’s Prayer on the head of a pin.
“But that’s nothing; that’s the most primitive, halting step in the direction I intend to discuss,” Feynman added. “It is a staggeringly small world that is below. In the year 2000, when they look back at this age, they will wonder why it was not until the year 1960 that anybody began seriously to move in this direction.”
Four decades later Mirkin developed the world’s smallest pen, an innovative tool that writes with molecular ink, and spelled out a portion of Feynman’s speech with strokes 60 nanometers wide. Using this technique, called dip-pen nanolithography, Mirkin could write 80 million pages per square inch — information far more dense than a prayer on the head of a pin.
Basically nanotechnology breaks down into three areas, all of which are actively researched at Northwestern. First, sophisticated tools, like Mirkin’s DPN, are being developed for making and manipulating structures on the nanoscale. (One hundred nanometers or smaller is the typical nanoscale.) Second, using these tools, new properties of materials are being identified. Third, researchers are figuring out how to utilize these properties for practical applications.
“What makes a material or device a true product of nanotechnology?” asks Stupp, who recently headed up a study requested by the White House on the effectiveness of the National Nanotechnology Initiative and in September testified at the first U.S. Senate hearing to be held on nanotechnology. “The features and structure are there by design.”
Historically, humankind has built things from the top down, carving computer chips out of silicon or building a cathedral out of quarried limestone. Now there is a fundamentally different way of building structures: from the bottom up.
Because researchers are learning to manipulate and control the interactions of individual atoms and molecules with precision, they can use these tiny building blocks to create designer materials and structures with superior properties that were purely science fiction only a few years ago.
“Two somewhat distinct approaches exist when building from the bottom up,” explains chemistry professor George Schatz, who applies materials theory to nanotechnology and whose knowledge is invaluable to the efforts of his fellow faculty.
“One is nanopatterning, where you use mechanical tools to move nanoparticles around manually and make structures,” he adds. “The atoms and molecules are happy to be put in place and remain there. The other approach is what nature uses, molecular self-assembly. These molecules will organize into a specific preprogrammed structure — the human body is a perfect example — with no patterning involved. And recently researchers have begun to merge these concepts.”
Questions and Answers
Sitting around a table outside a laboratory, materials science graduate student James Hulvat presents findings about a material’s properties to his fellow students and to Stupp. After listening closely to the details, Stupp says, “I have two questions: Why and so what?”
These two questions drive the scientists and engineers working in nanotechnology today. Only with the invention of powerful instruments, such as the scanning tunneling microscope and atomic force microscope, over the last two decades have researchers been able to control, manipulate and measure atoms and molecules. (The STM, invented in 1981, allowed scientists to view atoms in real space for the first time.) As a result, they are asking — and beginning to answer — a lot of interesting questions.
It turns out that properties — optical, structural, electrical, mechanical and chemical — for nearly every material change when shrunk down to the nanoscale. The most obvious is color. A micropowder of one material, say, the metal gold, is one color (gold), while the same material as a nanopowder is another color (red). The melting temperatures for gold in bulk form and gold on the nanoscale have a difference of hundreds of degrees. Why? And maybe more importantly, so what? How can a material’s properties, once probed, measured and understood, be applied to something useful?
Mirkin has made a discovery that is very useful indeed: He figured out how to attach gold nanoparticles to single strands of DNA without destroying the DNA. This tricky and novel pairing is leading to new and better medical diagnostic systems. When target DNA, say that of tuberculosis, is present in the physical sample, the strand matches its complementary strand of DNA on the test chip. Gold nanoprobes latch on to the match and act as a strong optical signal that the disease has been found.
“An inexpensive handheld device requiring a much smaller sample could be used to quickly and easily detect biological weapons such as anthrax and smallpox as well as a wide range of genetic and pathogenic diseases, from cystic fibrosis to HIV,” says Mirkin. He teamed up with Robert Letsinger, professor emeritus of chemistry and an expert in making synthetic DNA. “Results could be available in the doctor’s office or on the battlefield in a matter of minutes instead of days.”
Only after developing gold nanoparticles and better understanding their properties did Mirkin realize that the particles were useful for diagnostics. “It’s called keeping your eyes open,” he says.
Nanoparticles amplify light, and because the “noble metals” gold and silver do it best, Northwestern researchers are focusing on them and learning how to control their physical, chemical and optical properties. Theory always said metals could be used to create different colors by changing shapes and sizes. Now Richard Van Duyne has shown he can make every color of the rainbow from silver just by varying the shape and size of silver nanoparticles.
“It’s pretty amazing,” says Van Duyne, Charles E. and Emma H. Morrison Professor of Chemistry. “Once we understand their properties better and learn how to synthesize them in large quantities cheaply, nanoparticles will make a substantial commercial impact. ‘Smart’ windows could act like sunglasses and control the amount of heat that enters a building, and windows could be sensors to a biological attack.”
Michael Wasielewski, professor of chemistry and department chair, wants to harvest light. For years he has been interested in how green plants convert sunlight into chemical energy during the process of photosynthesis, so he’s taking cues from nature in a quest to build a better solar cell. Advances in nanotechnology have given him tools to begin understanding the details and to attempt to mimic the process in the lab.
“Instead of the typical stiff solar cell, we want to develop thin, flexible cells,” says Wasielewski. “They would have universal applications as portable, cheap and disposable power sources.”
Mark Hersam, assistant professor of materials science and engineering, has his eye on molecular electronics. His research group has developed a method to deposit precise patterns of atoms on a silicon surface, the material most commonly used in electronics. This could lead to molecular pathways and switches in computer chips thousands of times smaller and faster than today’s varieties, as well as nanoscale chemical and biological sensors.
After coating the silicon surface with hydrogen, Hersam uses the tip of a scanning tunneling microscope to pluck off hydrogen atoms one at a time and create a pattern of his choosing. This leaves a template full of dangling bonds, with the exposed silicon looking for something with which to react.
“The beauty is that very few materials exist that won’t react with these bonds, which opens up all kinds of possibilities,” says Hersam, who recently won a National Science Foundation CAREER award, NSF’s most prestigious award for new faculty. “We use silicon because we want to integrate with current technology, to create a bridge between microelectronics and nanoelectronics.”
Like electronics, flat-panel displays have turned into a multibillion-dollar industry. By being one of the first to probe organic light-emitting diodes at the nanoscale, Tobin Marks, Vladimir N. Ipatieff Professor of Catalytic Chemistry and professor of materials science and engineering, has developed technology that could lead to the world’s most versatile and stable LEDs. Marks expects his LEDs could be used in ultrathin flat-panel displays for automobiles, computer monitors, television screens, wristwatches, cellphones and other small devices, plus optical circuits, medical diagnostic devices and even greeting cards.
Working with theorist Ratner and Pulak Dutta, professor of physics and astronomy, Marks has been studying how electricity is injected into plastic, flows through the material and is turned into light. His experiments resulted in organic molecules self-assembling one layer at a time into a thin plastic film — the basis for his light-emitting diode technology. “We are using materials on the nanoscale — one nanometer or less — to govern the properties of our LEDs, such as brightness, color and viewing angle,” says Marks. The technology also could be used to make the world’s smallest light bulbs, perhaps to be integrated into wallpaper one day.
Biology is full of examples of nanotechnology, where organic and inorganic materials are employed to build systems with desired properties. While scientists and engineers are nowhere near nature’s capabilities, they are trying very hard to learn its secrets.
“Our bodies and most living things are the result of molecular self-assembly, where weak bonds form naturally between molecules,” says Ratner, who is often credited with starting the field of molecular electronics by proposing that single molecules might behave similarly to entire electronic devices. “How can we design and build new structures using similar bonds? First we need to understand the basic chemistry and science of molecular self-assembly, an area that is not very well understood.”
Molecular self-assembly is Sam Stupp’s forte. He has created self-assembling nanostructures shaped like mushrooms or fibers that form synthetic materials which could assist in human tissue repair and the delivery of drugs. Other self-assembling molecules form into “nanoribbons” that could strengthen and toughen plastics. (Molecules in current polymers are in a random network, in contrast with controlled nanopatterns that could produce beneficial properties.)
Stupp has been working with Monica Olvera de la Cruz, professor of materials science and engineering, whose specialty is polymer theory. “Sam discovered the system of these self-assembling mushrooms, and I helped explain why his materials behave the way they do,” says Olvera de la Cruz. “I enjoy understanding what causes a complex structure to form and why its properties are what they are.”
“Regenerative medicine is a big frontier,” says Stupp, who is director of Northwestern’s new Institute for Bioengineering and Nanoscience in Advanced Medicine. “Ideally we want the body to heal itself, regenerating bones, nerves, cartilage, the heart and other organs.
“Our work aims to create organic matrices, a road map of sorts,that can provide cells with the right information to differentiate themselves — into bone cells, neurons or pancreatic cells. Cells in any tissue live in an extracellular matrix from which they take their cues. We’ve mimicked this for bone, but we have offered a strategy that would work for other tissues and organs of the human body.”
Doctors one day might inject molecules that will self-assemble into structures that will encourage new bone-cell growth, perhaps for the treatment of osteoporosis or severe fractures in the elderly, or even to regenerate old nerve connections in a patient paralyzed as a result of a spinal cord injury.
The Road to Becoming Real
Science fiction writers were the first to imagine nanotechnology.
“Nanotechnology and its possibilities have played roles in Isaac Asimov’s Fantastic Voyage, Star Trek, Minority Report, The X-Files and Honey, I Shrunk the Kids, to name a few,” says Mirkin, whose expertise was appreciated by his son, Ben, only when nanotechnology made an appearance in the summer hit movie Spider-Man.
“Science fiction was here,” he says as he forms a circle with his right hand, “and the reality of nanotechnology was here,” making a circle with the other, separated by a large gap of space. “Now we have intersecting spheres,” as he moves his hands together, circles overlapping. “Nanotechnology is now in the process of becoming real.”
But it is still very early. While we already have sunscreen made of nanoparticles that let visible light pass through while capturing ultraviolet rays and nanoscale components in computers that make them run faster, the best is yet to come.
Mirkin predicts that biological and chemical diagnostic products capable of on-the-spot detection will be on the market over the next two years, resulting in major advances. Specially designed nanomaterials are expected to produce higher-density computer chips, gene chips and protein arrays in four to seven years. In the same timeframe might come drugs in a nanocapsule, programmed to travel to a specific part of the body to deliver medication at the right time. Further on the horizon, in 10 to 20 years, are nanoscale electronics, where it is hoped that molecules could assemble themselves into speedy computer chips.
To help ease the transition of important Northwestern inventions into the commercial market, the Institute for Nanotechnology has established the Small Business Evaluation and Entrepreneurs program, supported by $10 million from Chicago-based Lurie Investments. Using the expertise of faculty and MBA students from the Kellogg School of Management, the program gives scientists and engineers with new technologies assistance in developing comprehensive business plans for presentation to potential investors.
“BusinessWeek reports that nanotechnology promises to be a new industrial revolution leaving ‘virtually no business untouched,’” says Barry Merkin, clinical professor of entrepreneurship at Kellogg. “This new program is a tremendous opportunity for our students to be a part of a remarkable, emerging field.
“My students team up with scientists or engineers for at least one quarter, developing an extremely professional business plan and then presenting it to financial backers. The question we all are interested in answering is, ‘Do we have a business here?’”
Chad Mirkin used technology from his lab as successful trial runs for the business program and turned his inventions into what are now two companies, each a year old. Nanosphere Inc., founded with Letsinger, is working to advance DNA detection using nanoparticle probes, and NanoInk Inc. is commercializing Mirkin’s dip-pen nanolithography, which uses an atomic force microscope as a tiny pen for nanoscale patterning. (Northwestern has filed several patent applications based on Mirkin’s research, and several of them have been licensed to Nanosphere and NanoInk.)
This year Stupp and venture capitalist Steve Gorlin founded a company, NanoMateria, to develop Stupp’s discoveries in molecular self-assembly. Scott Barnett, professor and associate chair of materials science and engineering, established Functional Coating Technology LLC, a company to commercialize a protective coating material made extremely hard by its underlying nanostructure, which should be particularly useful for industrial cutting tools. There promise to be many more companies.
While these strides in gaining control over atoms and molecules are impressive, nanotechnology is in its infancy. Scientists invented the transistor in 1947, but it took decades before it led to widespread computers and the Information Age. James Watson and Francis Crick discovered the molecular structure of DNA in 1953, but it wasn’t until the mid-1990s that biotechnology and genetic engineering really began to take off.
This early stage, where breakthrough discoveries of fundamental science will fuel the technologies of tomorrow, is a critical time. And Northwestern is in it for the long haul.
“Chicago and the Midwest missed the information technology boom and largely missed biotechnology,” says Van Duyne, “but we are not going to miss nanotechnology.”
Megan Fellman is a senior editor in the Department of University Relations. She covers the sciences and engineering for the media relations group.
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