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A man with a deadly brain cancer is sent to a hospital for treatment. Instead of sawing open the man's skull and cutting out the tumor in hours of dangerous surgery, the doctor injects a fleet of tiny, cancer-hunting robots into the man's bloodstream.

This scene is the stuff of science fiction, but the field of nanoengineering could make it real.

Nanoengineering is the applied science of creating nanoscale-sized devices. Closely related to nanotechnology, it commonly involves the study of how atoms can be used to construct molecule-sized devices, such as circuitry wires. Nanoengineering gets its name from the nanometer, which is equal to one millionth of a millimeter.

"There are lots of things to do with objects of this size, mostly in electronics," Harvard University chemist George Whitesides said at an American Association for the Advancement of Science conference.

Gold atoms, a popular nanoengineering material because the metal doesn't corrode, can be arranged to make circuitry wires so thin that a hundred of them could be bundled inside a human hair.

Such tiny circuits show great promise in creating ultra-dense, ultra fast information processing systems in the future, Whitesides said.

He said that researchers at Cornell and Berkeley have already created simple machines on a molecular scale.

Buckminsterfullerenes (also called "buckyballs" after the geodesic dome creations of architect Buckminster Fuller) are round, hollow molecules made up of many carbon atoms, and are usable as tiny ball bearings in other nanomachines.

Nanoengineered devices might be used fairly soon in automobiles as crash sensors for air bags. Other researchers have created microscopic chemical sensors, clockwork gears, and even a miniature chemistry laboratory that can fit on a microchip.

"Even if we fail to come up with the technology to make fundamentally new devices, this will help refine existing devices," Whitesides said.

He also said that nanoengineering holds promise in medicine. He said that the most feasible use of nanomachines in the human body would be as sensors, perhaps for blood pressure or nervous system activity.

Whitesides also discussed the use of nanomachines in studying living cells. Researches have been able to make tiny cups to hold water droplets, only ten trillionths of a liter in volume, that have the same volume as the contents of a cell.

Researches then strip off a cell's outer membrane and dump its contents into the cup so that the cell's organelles can be examined.

Living cells can also be forced to conform to the shape of the cup, thereby allowing scientists to study cell growth.

"We're mucking around with cell shapes with these procedures," said Whitesides.

Despite all these possibilities, researchers must overcome many problems before nanotechnology will be useful outside the laboratory. Tiny circuits and machines are extremely fragile, and the materials the devices are made from must be painstakingly purified.

For instance, if engineers are using gold atoms to build a circuit and another type of atom slips into the batch, the foreign atom could disrupt the circuit's structure.

"When devices get this small, impurities play a very important role," cautioned IBM researcher Phaedon Avouris. "One impurity atom can change the whole device."

Indiana University chemistry department senior scientist John Huffman agrees that there are problems to overcome before nanoengineering will have real practical applications.

He said that nanoengineered circuits are so small that quantum effects can become important. Quantum effects are not seen except at the atomic level. One such effect might be "tunnelling," in which an electron suddenly disappears from one place and reappears in another. In a nanocircuit in which the electricity flow is only a few electrons at a time, having one of those electrons suddenly not be there could create problems.

Huffman believes that this problem can be taken care of by creating several circuits to do the same job within a device so that if one circuit fails there is always at least one backup.

"The main problem with nanoengineering is that it's such a new technology that not many places are equipped to teach or implement it ... it will take a long time before it will be commercially viable," said Huffman.

Despite this, Huffman is enthusiastic about the future of nanoengineering technology.

"The general scientific consensus is that nanoengineering will be invaluable, especially in the areas of sensors. The ability to make exceedingly small devices will allow us to measure all sorts of things, like chemical information and physical information, that we really couldn't measure before," he said.

Huffman also expects that nanoengineering will do great things for computer technology. He said that nanocircuitry will allow more and more information to be stored on a single chip, allowing the speed and complexity of computer systems to increase without wasting power or space.

Huffman was less optimistic about making reliable nanoengineered devices like tiny motors.

"They have demonstrated that they can engineer parts and assemblies, but we're still a long, long way off from developing useful machines," he said.

I originally wrote most of this for the Indiana Daily Student; quotes were obtained at a convention for the American Association for the Advancement of Science.

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