AMHERST, Mass. - University of Massachusetts physicist Mark Tuominen may have some trouble finding a T-shirt small enough for the UMass logo recently sketched in his lab. Tuominen, in collaboration with Tom Russell and Jacques Penelle of polymer science and engineering, is researching nanotechnology, a field aimed at producing devices so small that they can only be seen with an electron microscope. Tuominen and graduate student Mustafa Bal recently created a UMass logo which is roughly the size of a red blood cell - some six micrometers in diameter.
Although the yellow-and-orange microscopic logo may be cute, the technology behind it has some serious ramifications, according to Tuominen. The development, part of research funded by the National Science Foundation, has potential in creating precisely placed nanowires, still-smaller integrated circuits, and greatly increasing the bounds of magnetic storage in computers, he said. "Devices have gotten smaller and smaller," according to Tuominen. "This allows for faster computers and smarter cell phones. Developments in miniaturization have enabled a lot of our technology."
The field is so promising, noted Russell, that late last month, President Bill Clinton announced that he would seek a $2.8-billion boost in basic scientific and medical research - with $475 million of that to be spent on nanotechnology research, effectively tripling the amount of funding in the field. The funding is part of the budget that Clinton presented to Congress on Feb. 7.
In the last few years, scientists have been reaching the limit of how tiny a device they can create using conventional techniques. So the UMass researchers have turned to nature.
"What we realize is that nature has created very small devices in a very robust way," Tuominen said. "So it makes sense to learn from what nature does." Specifically, they look at molecules that form complex patterns spontaneously - molecules that scientists call "self-assembling." Though the concept sounds as though it was born in a laboratory, it is found in life: human beings contain molecules that self-assemble, from the DNA that holds our genetic coding to the lipids that help make up our cell membranes, Tuominen pointed out.
The UMass team began with molecular chains, like necklaces, called polymers. These polymers were custom-made in Russell's lab by graduate student Chris Stafford. Two distinct polymers linked together (called "diblock copolymers" by scientists) behave like oil and water, repelling each other while remaining inherently connected. The molecules "self-assemble" into a honeycomb-like grid of polystyrene - the same material used to make disposable coffee cups - with long, hexagonal channels, about ten thousand times thinner than a human hair. These channels are filled with polymethylmethacrylate -- Plexiglas. Thomas Thurn-Albrecht, a visiting scientist with Russell, used an electric field to orient the honeycomb in the film for the logo to be created.
To create the logo, Tuominen and Bal exposed regions of the "honeycomb" to a finely sharpened electron beam, which broke down the chemical bonds in the Plexiglas. The now-empty channels show up as orange areas on a yellow background. The UMass researchers have successfully filled the holes with metal, a major step toward creating usable electronic devices.
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