A distinct, unmistakable smell wafts through the doorway. North Dakota State University professors Kalpana Katti and Dinesh Katti survey the landscape. Look down -- yards and yards of sawdust litter the concrete floor. Look up -- stacks and stacks of boards and plywood strewn across rafters weave a haphazard wooden tapestry. Picture a cavernous bunker brimming with leftover carpentry projects. Some people might merely see a woodworking shop and storage shed. But as the Kattis pick among the mismatched pieces of wood and layers of sawdust, they imagine what it can become. Sort of like the ebullient real estate agent who shows a "fixer-upper" to a hopeful client in search of a dream home.
In the unkempt and forgotten woodworking shop in Ehly Hall, the professors envision distinct possibilities. There is no basement under the concrete floor, they recall later, almost gleefully -- a crucial feature if it is to house sensitive electronic equipment. It cuts down on the possibility of vibration which could affect the capabilities of the half-million-dollars worth of specialized instruments used in their research. Not that they had yet acquired the equipment they envisioned.
"We will clean it up," says Dinesh, remembering their determination when the couple first saw the space four years ago. Move wood, clean, scrub, sweep out sawdust and clean some more. Get rid of dust, the enemy of sensitive electronic equipment. Students scurry to prepare the space. Elbow grease and hours of work turn it from a carriage house into a castle -- at least if you're a scientific researcher looking for equipment, bright lights and a space to conduct experiments. When the Kattis walk through the door now, the brightly-lit space is punctuated with splashes of red cupboards, sinks, mismatched yet functional steel desks, and 24-inch diameter red spiral metal stanchions topped by a gray-speckled granite counter. "This is a homemade table," notes Dinesh, as he points to what's officially known as a vibration isolation table that students helped to build.
Today the lab hums with electronic equipment and students conduct experiments using an atomic force microscope and infrared spectrometer in the woodshop-turned-laboratory. "Now this space is as good as any lab in the country," says Dinesh. "Our students practically live here. It's like their home."
Both Dinesh and Kalpana speak with passion and enthusiasm about their research in detailed, yet understandable language. To emphasize the "science of the small" or nanotechnology, Kalpana describes herself as 1.6 billion nanometers tall, or about 5'3". As an associate professor at NDSU, Kalpana is a materials scientist.
Professor Dinesh Katti is a computational mechanics expert. Both are part of the civil engineering department at NDSU. The Kattis have received more than $1.5 million in research awards from the National Science Foundation and other groups -- awards that have funded tools and equipment for the former woodshop-turned-laboratory.
What is unique about the Ehly Hall lab, say the Kattis, is the marriage between science and engineering. The blending of these disciplines also brought about an exceptional discovery by the husband and wife research pair. "In the summer of 1999, Dinesh and I were sitting and having lunch," recalls Kalpana. Casually munching sandwiches, Kalpana posed an idea that might later be characterized as a fluke or as serendipity. Or maybe as a summer to-do list by one scientist to her fellow scientist who also happens to be her spouse. "I had just finished some research on seashells and was invited to submit a journal paper. The subject was fresh in my mind. I told him, 'you know, we should look at this.'"
Unsolved mysteries What intrigues the Kattis is the structure nature painstakingly builds on the inside of abalone shells. The pearly, white layer is often used to make jewelry. Known as nacre (pronounced nay' ker) to scientists, astute jewelry buyers know the iridescent gleam as mother-of-pearl. Although recognized for its beauty, scientists have spent decades and tens of millions of dollars to study it for other reasons. The shells are the real estate of choice for the oysters, mussels and other mollusks that live inside them. The organisms probably have no idea that their homes are of potential interest to the Department of Defense and NASA.
"Nature has made this as the best armor material," says Kalpana, tapping on the outside of a red abalone shell. "The outside layer is very hard. The inside layer is very tough. That means the outside layer will take impact. The inside layer will absorb energy if the outside layer breaks. That's exactly how armor works."
Seashells' strong, tough structure captivates scientists. "Strong means it can take a lot of load before it breaks. Tough means it will give a little. This is very unique," explains Kalpana. "Most engineered composites are one or the other."
Studying nacre -- a complex and densely-layered substance at the nanoscale -- involves many disciplines, including chemists, marine biologists, material scientists and others. The Kattis bring engineering to the mix of people working in biomi- metic nanocomposites. Bio meaning biology. Mimetic meaning mimicking nature. Nano meaning extremely small and composites meaning a material made of distinct components. Nacre displays extraordinary mechanical responses. What began as a breezy summer lunch conversation for the Kattis grew into gale force intellectual curiosity.
In addition to lab experiments, the Kattis examined scientific literature on the structure of nacre. "Let's build the structure on the computer and try to see what aspect of the structure makes it so strong and tough," recalls Kalpana. Using a personal computer, Dinesh built the first computer model of the nacre -- a simple structure with little detail. It was a start. "And then we put in more and more detail which people hadn't done," says Kalpana. "We ran simulations on this model. Instead of taking the sample of nacre and doing mechanical tests, we did it in the computer model."
Other research groups had previously determined that nacre's strength and flexibility were due to a variety of factors, including an internal brick-like structure held together by a pliable mortar of proteins that are nanometers thick. The miniscule "bricks" are made of calcium carbonate -- the same substance found in antacids or chalk or limestone. The orderly brick-and-mortar is meticulously arranged with organic and inorganic layers. The Kattis' computational model of nacre showed the organic material contained a soft material of properties with a magnitude much higher than expected. "The first time I presented this at a Materials Research Society meeting," says Kalpana, "at least 10 people stood up in the audience and said, 'There's no way.' These people were like the 'who's who' of biomimetics."
Secrets unfold Over the years, other researchers have made different incremental discoveries about nacre. But perhaps the beguiling beauty of polished jewelry had resulted in a scientific bias. A summer afternoon in one of the Kattis' labs yielded something new. Other studies used polished pieces of nacre to study its properties. Kalpana and Dinesh Katti and their research team milled samples of nacre into approximately 1" x 1/8" dogbone-shaped samples with pinholes at each end. They then used machines to pull the nacre samples apart, fracturing them in the process.
"There were four or five of us in the electron microscopy lab that day in 2002," recalls Kalpana. "Dinesh and I saw it at almost the same time. We jumped out of our chairs because we couldn't believe that nobody had seen this before. And the reason they hadn't seen it was because they always looked at a nice, clean, polished cross-section. They never looked at a fracture sample." By using a "diamond in the rough" rather than a polished sample, the nacre yielded some secrets. "What you could see was that these platelets are penetrating into each other. They are interlocking. This is a simple concept that nature uses and this was not observed by anybody before." Another feature the Kattis observed and reported -- the structure of the material is built like hexagonal bricks and mortar. "If they are rotated and penetrated, that's nacre interlock," says Kalpana.
But the Kattis and their student research team didn't want to simply report their discovery. They wanted to determine its significance. Dinesh's expertise in computational modeling was crucial. This type of modeling is the same modeling used for standard engineering to design a bridge, a car, an airplane. It became evident, though, that a PC couldn't provide the computational horsepower equivalent to the power of a Mack truck needed for their research.
While the nanoarchitecture of nacre represents the science of the extremely small, the computations to model them were at the extreme other end of the scale. To illustrate all the intricate detail contained in nacre's structure, Dinesh's models became more and more computationally intensive. Think of millions and millions of math problems rolled into one. So complex were the models that NDSU's Center for High Performance Computing, as well as the National Center for Supercomputing Applications at the University of Illinois in Urbana-Champaign, were used for the work. With more than two million computer nodes and each node completing an extremely large calculation, the models took hard-core computing power to create. That aspect of the work took approximately one year.
Others take note In some ways, by creating their own lab from scratch and by developing the detailed computer models, the Kattis engaged in a scientific version of "build it and they will come." Others took note of the research being done at NDSU. The Kattis' discoveries led to numerous invited presentations at scientific meetings in Boston, San Francisco, China, Italy, Brazil, as well as serving as guest lecturers at the Massachusetts Institute of Technology. They have published more than 20 articles on nacre, most recently in the May 2005 issue of the Journal of Materials Research. Another article has been accepted for publication this fall in Material Science and Engineering C. As for the doubters at the scientific meeting where Kalpana first reported on their research, "Now we've established ourselves. People know that we're about the only group that has looked at nacre from a mechanics point of view."
Nacre research continues around the world, with some labs creating artificial nacre. But scientists aren't trying to make seashells. "We want to use other materials and understand how seashells are made. Just like nature has taken calcium carbonate and made it 3,000 times tougher, we can take other composites and make them 3,000 times tougher," says Kalpana. "It could make possible lightweight armored aircraft, body armor, artificial body parts, and protective coatings that are strong and flexible." She points out that their research has shown that nacre's interlocking bricks, platelet size and organics are important. "If we can play with those, we can engineer materials that are much better than what we have now."
She remains intrigued by nature's perfection in creating nacre. "For us to manufacture it at this level of detail, we need fancy equipment in a very controlled environment with a clean room. And nature does this in the ocean, at ambient temperature, pressure, in a dynamic environment." Things like the rotation of the "bricks" were originally thought of as defects by scientists. But the Kattis' research and other studies now show differently. "They are there for a reason. Even the defects are engineered," says Kalpana.
Styles and substance Observing the Kattis during a recent television news interview under the bright lights of the lab they built, their complementary styles as research colleagues become apparent. Kalpana, animated and factual, talks in rapid-fire cadence about their work until the interview time is nearly over. "She's doing all the talking," chuckles Dinesh. "She's doing great. It happens at home too," he admits.
By contrast, her research partner Dinesh speaks with more deliberate reserve. He summarizes the implications of their work for the reporters and videographer as they wrap up the interview. "Scientists talk to other scientists. We should also talk to the public and get out of our scientific jargon," he says. "If you look at the type of research being done in nanotechnology, we need this type of research to remain competitive globally and to improve quality of life. When you do research like this, you can spin off industry and attract companies to the region."
Through the Kattis' research thus far, the exotic nacre has revealed some -- but not yet all -- of its secrets. Science, like a good detective novel, remains a mystery that awaits a final ending.
-- Carol Renner