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Extremely Small Brushes Could Improve Chip Production


Next, we have a short report about extremely small objects. Scientists are making brushes like the brushes you use to paint a house, only they're so small that you can't see them. One of them looks like a toothbrush except that it is smaller than a microscopic dust mite. NPR's Nell Boyce explains why anybody would want to make these things.

NELL BOYCE reporting:

Pulickel Ajayan is a scientist and he admits he's a bit of a neat freak.

Dr. PULICKEL AJAYAN: Definitely. I think I'm paranoid about, you know, keeping the house clean.

BOYCE: So it's kind of fitting that he's created the world's tiniest brooms. They can sweep up bits of crud way smaller than a speck of dust. Ajayan works at Rensselaer Polytechnic Institute in New York where he plays around with things called nanotubes. They're cylinders made of carbon atoms and they're just a millionth of a centimeter in diameter. A couple of years ago, the tubes got Ajayan and his colleagues thinking about bristles on a brush.

Dr. AJAYAN: When we looked at nanotubes, you know, it kind of fit the profile of what a bristle should be. They are long. They're flexible; at the same time, you know, locally very strong. And they're very, very tiny. So if you want to make, you know, an ultimate brush with very, very, very tiny, you know, bristles, we thought this could be a nice material.

BOYCE: Now making the ultimate brush is nothing like making your everyday hairbrush. Brush makers usually start with the handle, drill some holes and stick in the bristles.

Dr. AJAYAN: You cannot do that with nanotubes because, you know, first of all, each one of them are too small to handle and you cannot drill that small a hole on a fiber that is as big as your hair.

BOYCE: Instead of drilling holes, his team takes a hair-thin ceramic fiber and coats most of it with gold. Then they stick it in a gas-filled furnace that's over a thousand degrees. At that temperature, carbon atoms in the gases break away. They get attracted to the uncoated ceramic where they grow into nanotubes. Millions stand side by side just like bristles. In the journal Nature Materials, the team reports that it's made all kinds of teeny brushes, and they don't just look cute. They can do real work. They can paint the inside of very thin tubes and they can sweep debris out of impossibly narrow trenches, the kind you might find on a computer chip. That's caught the attention of other nanotech researchers like David Carroll at Wake Forest University.

Dr. DAVID CARROLL (Wake Forest University): It's pretty amazing.

BOYCE: Carroll says that these days a lot of computer chips that come off the assembly line are ruined often by bits of crud. Companies just toss them out, but they may be less willing to do that as they start making fancier chips and even micromachines.

Dr. CARROLL: And it may actually be worth the time and effort and money, the cost, to sit down there and clean it off if it's not working well.

BOYCE: If that day comes, now they know who to ask for some little brooms and tiny scrub brushes. Nell Boyce, NPR News.

INSKEEP: You're listening to NPR News. Transcript provided by NPR, Copyright NPR.

Nell Greenfieldboyce is a NPR science correspondent.
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