Tech Today: Engineering News

Can Nanotech be Made Co-Friendly From the Start?: How research and a new Ph.D. program aim to avoid "the path of DDT"

On a shelf in Greg Lowry's office in Civil and Environmental Engineering (CEE) are several tubes of a South Korean toothpaste. The printing on each box is in Korean characters, except for the block letters that say NANO SILVER. "Silver nanoparticles are anti-microbial," Lowry explains. "Maybe they're in there to attack the microbes that cause bad breath. But when you rinse your mouth, where do those particles go? Down the drain, and then where, and what do they do?"

Lowry's colleague, CEE professor Jeanne VanBriesen, notes that it's now possible to deodorize from head to foot with nanotech. "You can buy socks that have nanosilver embedded in the fibers to make your feet stink less," she says. "But every time you wash the socks, some particles wash away. Again, is there an environmental concern?"

The question looms larger as engineered nanoparticles of many kinds are coming to be used in products from fuel additives to medicines and electronics. What we want to avoid, says VanBriesen, is "going down the path of DDT or CFCs [the gases found to deplete the earth's ozone layer]. Only after those materials were in wide use did we begin to look at the consequences." That approach led to massive recalls and costly rework.

Carnegie Mellon is part of a unique effort to steer nanomaterials on a smarter path. The university is one of six in the U.S. housing research hubs of CEINT—the federally funded Center for the Environmental Implications of NanoTechnology—and one of two, along with Howard University, recently chosen to expand their CEINTs by piloting a first-of-a-kind Ph.D. program in the subject.

VanBriesen, head of the new doctoral program, says one goal is to seed the world of nanotech R&D with "engineers trained to think about the long-term impacts of what they are designing." Also, some of the Ph.D. students will major in engineering and public policy, and their mission will be "to bring scientific literacy to policy making in this field," says Lowry, the director of CEINT@Carnegie Mellon.

New Properties, New Risks

Nanoparticles are chunks of matter with dimensions of about 1 to 100 nanometers, much closer to the size range of individual atoms than to, say, grains of table salt. At that scale, factors such as quantum forces and surface effects can produce properties that a material doesn't have in other configurations.

For example, VanBriesen says, "We know that carbon has different properties depending on its structure. It can be a diamond, or graphite, or coal. Now we can engineer carbon nanotubes"—atoms bound together in long, hollow cylinders—"which are different from all of these and have unusual properties like very high tensile strength and conductivity." The nanotubes are being embedded in resins to make light, tough bicycle parts and other sporting gear; future uses could range from larger structural shapes like auto body parts to super-thin membrane filters and "paper batteries."

To strive for complex and highly targeted effects, nanoparticles may be made of multiple materials or have coatings. Some are being tested in medicine to deliver drugs where they're needed within the body, while scientists are trying to get others to selectively penetrate and kill tumor cells.

However, new properties could bring new hazards. Particles tiny enough to cross bio-barriers might get into unwanted places once they leave the body, and even nanomaterials used to protect the environment have the risk of backfiring. Cerium oxide is a very potent combustion catalyst in nano-form. It's being added to diesel fuels in Europe to burn the fuel more efficiently and cut emissions, and "the EPA is considering mandating its use in the U.S.," Greg Lowry says. "We'd be putting a lot of that nanomaterial into the environment and it's redox-active. It has the potential to interact with organisms."

Learning to Wrangle the Unknowns

The work of assessing and managing nano-risks is not only complex but inherently interdisciplinary. Carnegie Mellon's new Ph.D. program is being created with a five-year, $3.15 million IGERT grant from the National Science Foundation. IGERT (Integrative Graduate Education and Research Traineeship) funds are meant expressly for "preparing people to solve tough problems that can only be addressed at the interfaces of disciplines," VanBriesen says.

All students will take two years of intensive coursework from a curriculum now being designed, then move to Ph.D. research. "The students will choose whether they want to be 'development' engineers with a degree from one of our engineering departments or 'policy' specialists from EPP," VanBriesen goes on. "But the development people will still have to learn about the policy implications of nano, and the policy people will learn enough about the technology to be effective in their work."

Each aspect in itself is daunting. In the CEINT lab where much of the Ph.D. research will be done, Greg Lowry and other CEINT-affiliated engineering faculty already have been at work for over three years trying to characterize a few of the more common potential nano-hazards. For one experiment, rows of small beakers are filled with soil samples—some dry, some submerged in water and some recently wetted to simulate rainfall. They've all been dosed with silver nanoparticles. After due time, says Lowry, "we'll speciate the silver to see what we've got. Has any of it become silver dioxide, silver sulfate, silver chloride? Has it moved up or down in the soil samples? And so on."

This sounds fairly simple, until Lowry explains that the results will be far from definitive. At the CEINT facilities at Duke University, companion experiments are being run under more "natural" conditions, with much lower doses of nanosilver in controlled environments that include plants, fish and other small life forms. The quandary, Lowry says, is that "if you use high concentrations [of a nanoparticle] in the lab you may see effects that aren't observed, or aren't important, in nature. But with extremely low concentrations it's hard to measure anything." So the researchers conduct a variety of experiments, compare observations, and try to project how long-term exposure to the material might play out in real ecosystems.

Then the policy work adds further complexity. Once the possible impacts of a material are understood, "we have to choose appropriate policy responses for managing the risks versus the benefits," VanBriesen says. She notes that nanosilver is only one of many nanomaterials, and "if a material has medical benefits, that's a whole different risk-benefit balance than if it just makes your feet not smell." EPP Professor Elizabeth Casman, an expert in nanotech risk analysis, will take the lead in policy education for the IGERT Ph.D. program.

Despite the challenges, Jeanne VanBriesen believes that the first class of eight to ten Ph.D. students starting in September 2011 will represent a key step forward: "Nano is all about control. It's about choosing and altering materials to get the behaviors you want, when you want them. And there's an opportunity to learn how to get a wider range of benefits with less risk. What we do here can affect how the next generation of engineers will think about their work."

By Mike Vargo

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