SCIENCE & ENGINEERING NEWS
San Francisco, CALIF. — Carl T. Hall reports for the San Francisco Chronicle that big news is breaking this week in the “nanoworld,” the tiny but fast- growing scientific realm of such oddities as “dancing tin,” molecule-sized “helicopters” and incredible shrunken computer parts.
Using an electron microscope two stories tall, a team of scientists at the University of California at Santa Barbara and in Japan unveiled weird three- dimensional images of finely etched glass.
They look like fantasy scenes from a mathematician’s dreamworld, but turn out to represent a new reality of chemical-trapping “cages,” molecular pores and other structural elements as small as one-thousandth the diameter of a human hair.
The new images, published in the journal Nature, provide an early glimpse at some of the basic building blocks in nanotechnology, where researchers seek to make useful things that measure on a scale of the nanometer, or a billionth of a meter.
Meanwhile, a half-dozen research reports and scientific reviews are being issued in the journal Science, part of a special section on the latest nanotech developments.
“It’s extraordinarily exciting,” said Carlo Montemagno, a nanotechnology researcher at Cornell University. He is co-author of a report showing how biomolecular motors – driven by ATP, the same energy molecule that makes our muscles work – can be used to spin tiny fabricated propellers.
The resulting “helicopter” can’t really fly and has no apparent practical purpose – other than simply to demonstrate how biological and engineered components can be linked together with amazing precision.
“There’s no book to tell how to do this,” Montemagno said, recounting a seven-month effort to construct the first propellers, which he said were deliberately made large enough to be photographed, but could be much, much smaller.
It’s a prototype of hybrid bioengineered machinery that someday might be used to deliver drugs to individual cells in the body.
In fact, no one knows what they might be used for because practical nanotech devices are a long way off. But it now appears the essential first steps are starting to fall into place.
“We’re in the discovery phase,” said Harold Craighead, a physicist at Cornell and a pioneer in nanoscale electronic devices. “But you can see hints of applications starting to emerge already.”
They include finely tuned chemical sensors and devices capable of sniffing out chemicals, such as toxins in the environment, one molecule at a time.
Galen Stucky, a research chemist who led the three-dimensional imaging experiments at UC Santa Barbara, said scientists are starting to get “a direct handle” on objects too small to be seen directly with visible light.
Stucky’s team developed the mathematical formulas needed to produce nanoscale images in 3-D, a system for making “topographic maps” of structured glass. It is a way to see what you’re doing while attempting what’s known as three-dimensional chemical lithography, a type of industrial sculpture where nanoscale control is essential.
That, in turn, is a fundamental step toward fancy chemical-packaging systems and “smart materials,” where each little dip in the 3-D landscape might represent a holding tank for a different molecule or enzyme. Those could make up the working elements of much-anticipated new kinds of lasers, biochemical sensors and powerful shrunken computers where virtually every tiny detail is engineered into place. “Now we can visualize how we do it,” Stucky said.
Other intriguing images of nanotech at work include movie clips of tin crystals “dancing” across a surface of copper at Sandia National Laboratories in New Mexico.
The crystals are little “islands” of tin atoms floating on the copper. The islands spontaneously sweep across the copper dance floor, propelled by free energy and subtle atomic interactions at the surface.
It’s a phenomenon closely related to the so-called “camphor dance” first observed some 300 years ago, in which camphor particles were noted to move across a liquid surface. The phenomenon was used by the 19th century British scientist Lord Rayleigh to calculate the surface tension of water.
Now, scientists are reporting progress in gaining some ability to direct the choreography.
“What we’ve done is convert chemical energy into motion at a very small scale,” said Norman Bartelt, a materials physicist at Sandia and co-author of a report on the dancing tin in Science.
Bartelt and colleagues now are experimenting with other elements besides tin and copper. Later, they hope to gain precise control over the molecular dance steps by building chemical gradients into surface materials.
“There’s a long way to go and a lot of basic research to be done,” Bartelt said. “We want to understand things like this tin-island dance in atomic detail. And probably only when one can understand something like that can one hope to make something out of this.”
Meanwhile, Stanford University scientists are part of a global rush to make computer circuits out of extremely small components, including unimaginably thin wires made of carbon nanotubes.
Those are stretched filaments of thin-walled, precisely structured carbon whose properties can be manipulated by changing how the wires are assembled.
“It’s building structures from the bottom up,” said Stanford’s Hongjie Dai, whose team reported a way to chemically modify nanotubes in order to turn them into what are known as positive-negative junction devices.
These are the devices computer users take for granted – the working innards of logic circuits, in which functionality springs from networks of switches that allow precise manipulation of electrical signals.
The more of these switches that can be packed into a given amount of space, the more powerful the computer. The new nanotube semiconductor junctions are small enough to fit inside a molecule.
There are several other approaches aimed at the same goal of making small supercomputers. Nobody knows yet just how all the pieces might come together, but Dai maintains that will become clear soon enough.
“Within a few years,” Dai said, “we’ll have a much better idea about how to make this into a real technology.”