New Nano-Brushes Keep the Tiny Tidy

June 17, 2005

Even at the nano-scale—where machines and materials can be the size of atoms and molecules—there are messes to sweep, walls to paint, tubes to unclog, and electronics to power. And now there's a way to make the tiniest of brushes to do these chores.

Made with bristles more than a thousand times smaller than a human hair, they are the tiniest brushes in the world. Yet they are durable and flexible enough to perform any brushing chore.

Conventional brush bristles, made of animal hairs, synthetic polymer fibers, and metal wires, are flimsy and prone to breaking down at the nano-scale, researchers say.

To work at the nano-scale, researchers realized that a different kind of material was needed.

"It dawned on us that [carbon] nanotubes would make excellent bristle material," Pulickel Ajayan, a professor of materials science and engineering at the Rensselaer Polytechnic Institute (RPI) in Troy, New York, said in an e-mail to National Geographic News.

Ajayan has worked with carbon nanotubes—or cylinders of carbon molecules—for more than a decade. Their small size, strength, elasticity, and ability to conduct electricity make them ideal bristle material at the nano-scale, he says.

Together with colleagues at RPI and the University of Hawaii at Manoa, Ajayan has made brushes with nanotube bristles in a variety of shapes and sizes. The researchers used them to perform tasks such as sweeping up nanoparticles in a narrow trench, coating the inside of a tube, and serving as electrical contacts in a nano-motor.

The researchers explain how they made the new brushes in the July issue of the academic journal Nature Materials.

Eric Grulke, a professor of chemical and materials engineering at the University of Kentucky in Lexington, said in an e-mail that the research was "quite innovative with respect to potential applications."

Nano-Brush Market

According to Ajayan, as materials and machines get smaller and smaller, the potential market for nano-sized brushes will blossom. Even the smallest amount of dirt can render machines at the nano-scale useless.

Interest in cleaning up nanoparticles has intensified lately due to growing health concerns over their release in the environment.

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