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David Carroll

Physics professor David Carroll, director of the Center for Nanotechnology and Molecular Materials, examines a solar power cell developed using nanomaterials.

The Nanotechnology Center

Thinking big about some very small things.

By Ker Than

The Center for Nanotechnology and Molecular Materials, which opened its doors in 2004, is Wake Forest's entry into the field of nanotechnology, a relatively new but fast-growing and encompassing science devoted to the study and manufacture of structures and materials too miniscule to be seen with the naked eye.

Advances in nanotechnology have the potential to impact virtually every field of science, according to the center's director, David Carroll. The research at Wake Forest could one day enable doctors to use tiny probes smaller than living cells to image cancers in unprecedented detail, and then eliminate them using nano-medicines that seek out tumors like microscopic hounds, leaving healthy cells untouched.

Exotic nanomaterials being developed could allow engineers to manipulate light to create more energy-efficient lighting, or bend it in ways previously considered impossible so as to construct invisibility cloaks like the one worn by Harry Potter. Nanomanufacturing techniques could enable future scientists to shape hearts, livers, and other organs using synthetic protein fibers in much the same way a potter sculpts and molds clay.

Derived from the Greek word for midget, "nano" means a billionth. A nanometer is a billionth of a meter. This is about a hundred-thousandth of the width of a human hair, and smaller than the distance between two peaks in a wavelength of visible light.

At the nanoscale, commonplace materials display new and often startling physical and chemical properties. Solids become liquid; opaque materials become transparent; and electric insulators become willing channels for flowing electrons.

"We've always been able to make things relatively small, but what we've found is that by controlling the way we do it, properties emerge from these materials that we couldn't have imagined," Carroll says.

For example, a nano-material that is currently of intense interest to scientists is carbon nanotubes. These are single-atom-thick sheets of carbon atoms that have been curled into cylinders. If you could magnify one until it was visible to the naked eye, it would look like a rolled sheet of chain-linked fence. Carbon nanotubes can be one hundred times stronger than steel but weigh six times less. A single strand as thin as a sewing thread can lift an automobile yet is flexible enough to be woven into fibers.

The amazing thing is that carbon nanotubes are chemically identical to graphite, the material in pencil lead. Both consist of sheets of carbon atoms. But whereas carbon nanotubes consist of a single sheet or at most a few sheets, graphite is made up of innumerable layers of carbon atoms stacked atop one another. The chemical bonds between carbon atoms in a sheet are incredibly strong, but the bonds between layers are not.

Wake Forest researchers are working with carbon nanotubes to develop alternative energy technologies and to devise new ways of combating cancer. They are also inventing new nanomaterials and creating new manufacturing techniques that might one day allow scientists to grow artificial hearts or make invisibility cloaks a reality. Some of these technologies will require years to bear fruit, but two developed at Wake Forest have been successfully spun off into startup companies that could soon be making products for the commercial marketplace.

Carroll aims to make Wake Forest a major player in the burgeoning nanotech field, and the University has given him the resources to make his dream a reality. "When you go to the nanotech center, you see one of the best equipped and finest centers of its kind that I know of," Carroll says proudly. The "clean room" at the Center's main building on Deacon Boulevard alone contains more than $10 million worth of microscopy equipment. "It's a very good facility," Carroll says. "We're told that constantly by people that come over."

And people are always coming over. As part of his effort to make the Center for Nanotechnology a world-class research facility, Carroll has set up a visiting scientist program that invites top people in the field to conduct research at Wake Forest. In the past year alone, the Center has hosted researchers from Canada, Thailand, Germany, and the UK, among other countries.

The goal, Carroll says, is to foster a cross-pollination of ideas and to make Wake Forest "a part of the conversation" in nanotechnology research. "Whatever is going on, you need to be in the middle of it," Carroll says. "When development happens, you want to be one of the ones that are talking."


Part 2: Cross campus interaction

Wake Forest scientists are encouraged to interact with scientists from other fields on campus in order to learn from each other and to collaborate when it is mutually beneficial. Carroll does his part by organizing seminars for his colleagues that introduces them to nanotechnology and its potential.

A few years ago, Carroll gave one such seminar to cancer biologists and researchers at Wake Forest University Baptist Medical Center. Among the audience members were husband and wife cancer researchers Frank and Suzi Torti. (Frank Torti, formerly director of the Comprehensive Cancer Center at Wake Forest University Baptist Medical Center, took a leave of absence from the medical center in the spring of 2008 to become principal deputy commissioner and the first chief scientist of the U.S. Food and Drug Administration.)

"That was really eye-opening," Suzi Torti recalls. "It taught a lot of us things we didn't know were possible. That was really the catalyst that got us thinking about how we could take advantage of these new materials."

Soon after that talk, the couple conceived of a novel way of using carbon nanotubes to kill tumors. Their method involves injecting the tiny cylinders into tumor cells and then shining infrared (IR) light upon the affected area. One of the remarkable properties of carbon nanotubes is that they make excellent antennas. Upon exposure to IR light, the nanotubes become hot and destroy the cancer cells but leave healthy surrounding tissue intact.

The Tortis have tested their technique on tissue cultures and in mice, and the results have been very encouraging. "We can get what looks to be excellent tumor regression," Suzi Torti says. The tumors "shrink to nearly non-detectable levels."

If the Tortis' technique can be shown to be safe for humans, it could replace a widely used procedure known as radio frequency ablation, which involves inserting electrodes into tissue near a tumor and then using high-energy radio waves to heat and kill cells in the region. This technique involves surgery, however, and it often damages healthy tissue in the process.

In contrast, the nanotubes approach could be much more precise and would be noninvasive, Suzi Torti says. The nanotubes could be injected into a patient's bloodstream and circulate through the body until it reaches the site of the tumor, where they would "leak out" naturally.

"Tumors recruit blood vessels into them so they can have enough oxygen and nutrients to grow," Suzi Torti explains. "But this vasculature is imperfect. It's sort of a deformed leaky blood vessel, so if you introduce things into the blood stream, they can leak out of vessels in the tumor and accumulate. But they won't leak out of normal vessels."

Another researcher inspired by the exciting possibilities offered by nanotechnology is Joel Berry (PhD '00), a Wake Forest biomedical engineer. In collaboration with scientists at the Center for Nanotechnology, Berry has developed a technique called "electro-spinning" to create very thin fibers of the protein collagen, which is a primary component of connective tissue in animals.

Berry aims to weave the fibers into "collagen scaffolds" upon which living cells can attach and grow to become living blood vessels, heart valves, or whole organs. To create a scaffold, the fibers are slowly deposited onto a spinning target structure. "It's almost like making cotton candy at the circus," Berry says. "You form a three-dimensional shape by continually wrapping the fibers onto a target."

Berry thinks electro-spinning could overcome the problem of poor blood circulation, the main obstacle faced by scientists attempting to grow artificial organs. Normal tissues and organs are crisscrossed by tiny blood vessels and capillaries that deliver oxygen and nutrients to cells and carry away wastes. So far, scientists have failed to recreate this "microcirculation" in the lab, but scaffolds of electro-spun collagen fibers could be made porous enough for blood vessels to grow.

"If you give cells enough porosity and enough nutrients, they will simply thrive upon that network," Berry says.

His team still has a long way to go before they create a beating heart in the lab, however. Their immediate goal is to create a functioning "living artery" that could be useful for people in need of arterial replacements. In coronary bypass surgery, for example, doctors commonly remove a section of artery from another part of the patient's body, such as the thigh, and use it to replace a damaged heart artery. "You can eliminate another surgery if you don't have to take it from someplace else," Berry says.

Since joining the Wake Forest faculty in 2003, Carroll has published more than 200 articles in scientific journals. Two of his research topics have been successfully spun off into commercial companies called Plexilight and FiberCell.

Plexilight uses nanotechnology to produce visible light directly instead of as a byproduct of heating a filament or a gas, which is the method used in traditional incandescent and florescent bulbs. The company has already developed light fixtures that are lighter, thinner, and more efficient than existing incandescent or fluorescent fixtures.

FiberCell combines nano-manufacturing techniques with optical fiber technology to create solar cells that are lighter and more economical than current silicon-based solar panels, which are bulky and expensive. While solar collectors with the new technology might look similar to existing panels, they could be installed in new ways because their efficiency is not as dependent on the angle of the sun. FiberCell solar panels might one day be incorporated directly into roof shingles or mixed with paints, making them unobtrusive and nearly invisible.

If they can be manufactured cheaply, FiberCell solar panels could help improve the lives of people in developing countries. "What people in sub-Saharan Africa need is access to power to run the single refrigerator that sits in their very small clinic at the end of their village," Carroll says. "Right now they're having to walk forty miles to get a gallon of gas to keep their generator running. We can make a solar cell out of plastic that's completely mobile that they can unfurl to keep those clinics going and get off-grid power."

A desire to harness the power of nanotechnology to improve the lives of the less fortunate is a major driving force behind Carroll's research and his goals for the center. "It's about raising people's expectations about themselves and their planet, and doing the kind of science that makes a real difference," he says.

Ker Than is a freelance writer living in New York City.



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