Professor hopes findings will steer development in a completely new direction
By: David Campbell
Nanotechnology the manipulation and manufacture of materials at the molecular level already has brought about improvements in numerous everyday products, and it promises dramatic breakthroughs in the medical, computing, telecommunication and other industries.
Now, Princeton University theorist Salvatore Torquato has come up with a radical new mathematical approach that could turn a central concept of nanotechnology in a completely new direction. Does it rise to the level of playing God?
"We’ve come up with a completely different approach," Professor Torquato said. "We are standing the problem on its head. We’re able to tune the interactions to get exactly what you want. We’re playing God in this very limited sense."
The interactions in question function according to what nanotechnologists call "self-assembly" and what Professor Torquato referred to as the "Edisonian" approach of trial-and-error.
Put simply, scientists stage interactions among molecular building blocks, which spontaneously arrange themselves into larger, carefully organized structures.
"When you put them together and they self-assemble, you get what you get, and if it’s interesting, fine," said Professor Torquato, who is a chemistry professor at Princeton and a member of the Princeton Institute for the Science and Technology of Materials. He is also a senior fellow at the new Princeton Center for Theoretical Physics.
In a paper published in the Nov. 25 issue of Physical Review Letters, a leading physics journal, he and his colleagues visiting research collaborator Frank Stillinger and Mikael Rechtsman, a graduate student in physics at Princeton outline a mathematical approach that essentially would invert the process.
The interactions still turn on self-assembly but they would do so according to a blueprint designed by the nanotechnologists.
"It’s an inverse approach," he said. "You pick the structure you want, then design the interaction to arrive at that structure. When you put the particles together, they collectively behave toward the target structure when they self-assemble, they fall in line with the design."
Right now, this optimization approach is in the form of a computational algorithm, but he said the technique is more than just hypothetical, noting that computer models of these kinds correspond extremely well with real materials.
He said another colleague, Professor Paul Chaikin, a physicist at New York University and a former Princeton professor, is planning to do laboratory experiments based on the modeling work.
The computer modeled the new technique in two dimensions. Imagine a flat plane of particles like pennies scattered on a table. When compressed, the coins would normally self-assemble into a pattern called a triangular lattice.
But by optimizing the interactions of the pennies, Professor Torquato made them self-assemble into an entirely different pattern known as a honeycomb lattice, a structure that resembles its name.
This is key, because the honeycomb lattice is the two-dimensional analog to the three-dimensional diamond lattice the creation of which he called the "holy grail" of nanotechnology.
The next step is to take the research into three dimensions, Professor Torquato said.
He said he initially had trouble attracting money to support the research, because it was thought too far out in left field. The work was ultimately funded by the Office of Basic Energy Sciences at the U.S. Department of Energy, and it appears to have paid off.
"The honeycomb lattice is a simple example but it illustrates the power of our approach," he said. "We envision assembling even more useful and unusual structures in the future."