Air Date: Week of February 7, 2003

Living on Earth’s Maggie Villiger reports on a new development in nanotechnology, a surface that can toggle back and forth from water repelling to water attractive at the flip of a switch.

Transcript

CURWOOD: Just ahead, wild pigs on the rampage in California. First this environmental technology note from Maggie Villiger.

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MAGGIE VILLIGER: In the field of nanotechnology, it's vital to be able to manipulate the properties of raw materials. Now, researchers at MIT have figured out how to control a surface's ability to attract and repel water.

The scientists constructed a thin gold surface covered with tiny perpendicular molecules. Their invention resembles a hairbrush lying on its back with the bristles pointing upwards, though these bristles are only about one billionth of a meter long. The ends of the bristles are negatively charged and attract water. But when the scientists apply an electric field to the gold surface, the bristle tips are attracted to the gold and bend over. And since the lengths of the arching bristles are positive, they now repel water.

The switch back and forth from water-attractive to water-repelling is easily reversible and repeatable. Scientists foresee using a surface like this one to deliver drugs to precise destinations in the body, or they could be used to sort proteins from a complex mixture of molecules. The researchers are currently working on ways to enhance the strength of the attraction and to figure out how the toggle idea could be applied to properties like adhesion, friction or bio-compatibility.

That's this week's technology note. I'm Maggie Villiger.

CURWOOD: And you're listening to Living on Earth.

[MUSIC: Thievery Corporation “Liberation Front” The Richest Man In Babylon, ESL Music (2002)]