Researchers at Rensselaer have created a line of brushes whose bristles, made from carbon nanotubes, are so small that a thousand of them could fit inside a strand of hair.

The carbon nanotube brushes already have been tested in a variety of tasks that range from cleaning microscopic surfaces to serving as electrical contacts. The brushes eventually could be used in a whole host of electronic, biomedical, and environmental applications, says Pulickel Ajayan, the Henry Burlage Professor of Materials Science and Engineering at Rensselaer, who is heading the research.

The research, in collaboration with the University of Hawaii at Manoa, was published in the July issue of the journal Nature Materials. Rensselaer postdoctoral associate Anyuan Cao, working with Ajayan, is the lead author of the paper.

The brushes look like microscopic toothbrushes, and brooms, with handles the diameter of a human hair. Each brush is composed of millions of carbon nanotubes, each about 30 nanometers in diameter. The brushes have been tested manually and with rotating electric motors.

The researchers have used them to remove nanoparticles in microscopic grooves on various substrates. They also have cleaned and coated the inside of a 300-micrometer-wide capillary tube. Also, because carbon nanotubes conduct electricity, the brushes have been successfully used as electromechanical switches in micromotors and as electrical contacts.

The brushes could be used to sweep away tiny particles and dust that cause static electricity, particularly nanosize particles that are difficult to remove by other means, Ajayan says. Static electricity due to particulate attraction is a bane to the electronics industry.

From a biomedical perspective, the brushes are small enough to be used to clean up unwanted deposits in arteries and other blood vessels, Ajayan adds.

The materials typically used for making conventional brushes include animal hairs, synthetic polymer fibers, and metal wires. But metals corrode, hair is not very strong, and synthetic fibers degrade easily, according to Ajayan. “Because of their small size, strength, light weight, pliability, and resistance to heat, carbon nanotubes may be a better option.”

Originally published in Rensselaer Magazine, Fall 2005

Published November 1, 2005