Give physicists a sandbox, and they can build a career in it. Indeed, many physicists see a sandbox as a sort of universe in miniature. Probing the forces in moving sand, called granular flows, has recently revealed new insights into landslides, earthquakes, and the evolution of the cosmos--and is even helping to predict Wall Street's gyrations.
But when Alexander D. Wissner-Gross boned up on sandbox physics in 1998, at the tender age of 16, his imagination took off in the opposite direction. Instead of contemplating giant events, he thought about the world of the unimaginably small--and of the emerging field called nanotechnology. The goal here is to build everything from microchips and drugs to household appliances, molecule by molecule, or even atom by atom. But there's a hurdle nobody has managed to surmount: the lack of processes that can use individual atoms and molecules as building blocks and quickly assemble them into products. Coaxing nanobits to self-assemble chemically is one promising approach. Wissner-Gross thought sand could offer another solution.
Shake a box of sand rapidly and tiny waves ripple across the surface. To Wissner-Gross, the waves had an appearance similar to moving fingers--and that gave him an idea. He proposed replacing the sand with carbon buckyballs, soccer-ball-shaped molecules just one nanometer (a billionth of a meter) in diameter. In his vision, infinitesimal nanowaves would carry molecules or atoms by the billions and deposit them at selected locations. In particular, nanofinger factories might quickly patch together carbon nanotubes--an elongated cousin of buckyballs--into microscopic computer circuits. Such nanochips could lead to pinhead-size computers packing as much punch as all of today's supercomputers combined.
INQUISITIVE CAMPER. Nanotech researchers soon snapped to attention. "Alex' idea is a classic example of bringing fresh thinking to a phenomenon," says David J.K. Goldhaber-Gordon, a physicist at Harvard University. Paul S. Weiss, a chemist who heads Pennsylvania State University's Center for Molecular Nanofabrication & Devices, terms the concept "incredibly bright and creative."
Wissner-Gross hatched his nanofingers scheme at Mitre Corp.'s elite summer camp for budding scientists. Each year, the Pentagon-funded think tank hires a dozen or more top-performing students to probe the frontiers of nanotechnology, electronics, and other high-tech areas.
Wissner-Gross clearly fit the bill. In the summer of 1998, he had just finished his junior year at Great Neck South High School on Long Island, where he was a legendary whiz kid. In 1997, he ranked No. 4 in the USA Computer Olympiad for student programmers. The next year, he came in first, and also won the USA Math Talent Search competition, which he won again in 1999. A skilled fencer and singer, he performed with the New York City Opera for its 1992 and '93 seasons. Now at Massachusetts Institute of Technology, he's working on a triple major in electrical engineering, physics, and math, plus a minor in biology--and making straight A's.
The nano sandbox idea came after Wissner-Gross joined Mitre's Nanosystems Group and discovered the woeful state of atomic assembly. Today's best approach is a painstaking procedure involving so-called scanning-probe microscopes (SPMs). These complex devices wield ultrafine needles so sharp that they can trace the contours of atoms, then project an eerie, computer-generated landscape. But the capabilities of SPMs aren't confined to viewing atoms--using them to build things is also possible. In 1990, IBM researchers demonstrated the potential, lining up 35 xenon atoms to spell out the company name. That took 22 hours. Since then, nanotechnologists have designed many minuscule motors, gears, and other components. But the time and money required for even the simplest task still falls far short of commercial viability.
When he arrived at Mitre, Wissner-Gross was already familiar with some of the math behind sandbox physics. Digging deeper, he discovered almost no attention had been paid to how much force existed in the sand fingers--or whether it could be tapped. "So I spent the summer figuring out if they could be used for manipulation," he recalls.
PATENTED. Wissner-Gross developed computer simulations showing that the undulating micro dunes are shaped by energy waves that sweep back and forth coherently--and that "this force could be harnessed to do useful work." The research earned him the 10th spot in the 1999 Intel Science Talent Search, in addition to five awards at the 1999 International Science & Engineering Fair, which was also sponsored by Intel Corp. (INTC) Mitre has been so impressed with Wissner-Gross's work that it filed for--and was awarded--a patent in his name.
For confirmation of the student's simulations, Mitre Nanosystems chief James C. Ellenbogen tapped Harvard's Goldhaber-Gordon, a Mitre associate since he went to summer camp in 1989. The setup he built last year is designed to study progressively smaller grains made of plastic, gold, or glass. Shrinking the grain size in steps is essential because things get increasingly sticky as you head down the size scale. Tinier particles tend to clump together more tenaciously--which may necessitate lubricating the balls with a Teflonlike coating. Either way, after nearly two years of testing, Goldhaber-Gordon says he's optimistic that a nanofingers system should be ready to fabricate chips within four years.
First, though, Wissner-Gross must perfect a control system that can arrange nanotubes in precise patterns to form transistors and connecting wires. He hopes this can be done by varying the frequency, direction, and strength of the shaking action. "I'm running several simulations at the moment," he reports, "using complex motions to see what kinds of things the fingers can make." If it all comes together, nanofingers should write Wissner-Gross's name large in history books. By Otis Port in New York