Scientists Develop Self-Cleaning Windows

Jan. 26, 2005 — -- If you don't like to "do windows," you're going to love Bharat Bhushan.

The Ohio State University professor of mechanical engineering is developing technology that could result in windows that actually clean themselves.

Now, clean windows aren't exactly at the top of Bhushan's worry list, but it turns out that the same technology that can reduce friction in the moving parts of tiny devices could also keep your windshield clean.

And we know that because awhile back Bhushan got all worked up over lotus leaves.

Stay with me here.

"The primary application is nano-technology," Bhushan said.

You might say he lives in a very small world, where new devices are being developed at a rapid rate on a scale that almost defies imagination. Motors so small they can power robots smaller than a dime. Sensors so tiny they can't be seen, but so sensitive they can detect even traces of toxic chemicals.

All those tiny gizmos face a common problem, friction. And since it isn't possible to climb inside with an oil can, some way has to be found to virtually eliminate friction between moving parts for the lifetime of the device.

But how do you do that?

For an answer, Bhushan turned to the fabled lotus leaf, because the surface of a lotus leaf seemingly defies the laws of friction. Even water just rolls right off the leaf.

"Nature is doing something right," Bhushan said during an interview while he was waiting to catch an airplane. "So I said, let's see if we can mimic it, and even improve upon nature. That's hard to do."

But as he studied the lotus leaf, he came to a conclusion that has been reached by others. The lotus leaf sheds water because it is what scientists call "hydrophobic." That's a Greek term meaning, literally, fearful of water.

That's important, Bhushan says, because in order to have low friction, a surface has to be hydrophobic. "In general, what's good for water-repellency is good for fighting friction," Bhushan said.