Nanotweezers for a Very Small Toolbox

Researchers have developed the smallest pair of tweezers ever: a device that can manipulate particles as small as 10 nanometers across--less than the width of a virus--they report in today's issue of Science. These so-called nanotweezers could help speed the development of microscopic devices in fields such as electronic circuitry, gene chips, and microsurgery.

Until now, manipulating the nanoworld has been limited to pushing nanostructures around with the tip of a scanning probe microscope--an expensive and cumbersome piece of machinery that can only operate in two dimensions. Useful manipulation requires moving in three dimensions, says chemist Charles M. Lieber of Harvard University in Cambridge, Massachusetts. "Let's say you're trying to build a house, and you want to nail the wood together," he says. "With current technology, you could push the nails around and get them wedged in depressions in the wood. But what you need to do is grab the nails, so you can stand them upright and pound them in."

Physicist Philip Kim, now at the University of California, Berkeley, and Lieber created nanotweezers out of micropipettes and nanotubes, hollow carbon tubes related to buckyballs. They affixed two nanotube bundles, each about 50 nm in diameter, to gold electrodes layered on the tip of a micropipette. Opposite charges on the electrodes cause the nanotubes to squeeze together, and the same charge pushes them apart. Testing the nanotweezers on 500-nm polystyrene clusters under a light microscope, Kim and Lieber were able to grab over 80% of their targets. Nanotweezer size is limited only by what the researchers can see under the light microscope--the nanotube arms are just barely longer than the wavelength of visible light.

Lieber says nanotweezers could potentially be used for nanosurgery, unfolding or manipulating protein complexes within a cell, or as microelectrodes. Indeed, they are likely to have many uses not even thought of yet, says chemist Chad A. Mirkin of Northwestern University in Evanston, Illinois: "The sky's the limit right now. All this stuff was almost based solely in science fiction, and now we're seeing these ideas get developed."

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